diff --git a/app/(site)/(components-ui)/components-ui/examples/actions-and-forms.tsx b/app/(site)/(components-ui)/components-ui/examples/actions-and-forms.tsx
index 2925f940..7fc3ec19 100644
--- a/app/(site)/(components-ui)/components-ui/examples/actions-and-forms.tsx
+++ b/app/(site)/(components-ui)/components-ui/examples/actions-and-forms.tsx
@@ -2,7 +2,7 @@
 
 import { useRef, useState, type FormEvent } from "react";
 import { RotateCcw } from "lucide-react";
-import { UiButton, UiCopyAction, UiDisclosure, UiDownloadAction, UiQuantityField, UiRepeatableList, UiSelect, UiTextField, type UiOption } from "@/app/ui/controls";
+import { UiButton, UiCopyAction, UiDisclosure, UiDownloadAction, UiQuantityField, UiRepeatableList, UiSelect, UiShareAction, UiTextField, uiSetSummary, type UiOption } from "@/app/ui/controls";
 import { UiActionRow, UiStatus } from "@/app/ui/display";
 import { Example } from "../gallery";
 import styles from "../components-ui.module.css";
@@ -23,6 +23,9 @@ type Drive = { id: string; capacity: number; unit: string };
 export function ActionsAndFormsExamples() {
   const [hostname, setHostname] = useState("");
   const [recordSize, setRecordSize] = useState("128K");
+  const [windowDays, setWindowDays] = useState("");
+  const [annualShare, setAnnualShare] = useState("");
+  const advancedSet = [windowDays, annualShare].filter((value) => value.trim()).length;
   const [hostnameError, setHostnameError] = useState<string | null>(null);
   const [status, setStatus] = useState("Enter a hostname, then check it.");
   const hostnameRef = useRef<HTMLInputElement>(null);
@@ -112,8 +115,17 @@ export function ActionsAndFormsExamples() {
         />
       </Example>
 
-      <Example components={["UiDisclosure"]} note="Hide settings most people never change." source="app/ui/controls.tsx" title="Hidden settings">
-        <UiDisclosure label="Advanced settings" summary={`${recordSizeOptions.find((option) => option.id === recordSize)?.label} record size`}>
+      <Example components={["UiDisclosure", "uiSetSummary"]} note="Advanced holds optional refinements, closed by default. Name it for what's inside. While closed, the summary says what's set. Empty fields change nothing." source="app/ui/controls.tsx" title="Advanced settings">
+        <UiDisclosure label="Cohorts and billing" summary={uiSetSummary(advancedSet)}>
+          <div className={styles.twoColumns}>
+            <UiTextField hint="Days each trial gets to pay, counted from its start." inputMode="numeric" label="Follow-up window" onChange={setWindowDays} placeholder="30" suffix="days" value={windowDays} />
+            <UiTextField hint="Share of new customers who pick a yearly plan." inputMode="decimal" label="Annual-plan share" onChange={setAnnualShare} placeholder="20" suffix="%" value={annualShare} />
+          </div>
+        </UiDisclosure>
+      </Example>
+
+      <Example components={["UiDisclosure"]} note="A disclosure can also hold evidence or diagnostics, such as raw responses." source="app/ui/controls.tsx" title="Diagnostics">
+        <UiDisclosure label="Pool settings" summary={`${recordSizeOptions.find((option) => option.id === recordSize)?.label} record size`}>
           <div className={styles.narrow}>
             <UiSelect
               label="Record size"
@@ -124,6 +136,12 @@ export function ActionsAndFormsExamples() {
           </div>
         </UiDisclosure>
       </Example>
+
+      <Example components={["UiShareAction"]} note="Copies a link that reopens the tool with the same inputs. Empty values stay out of the link." source="app/ui/controls.tsx" title="Share link">
+        <UiActionRow>
+          <UiShareAction params={{ trials: 200, paid: 22, price: 29, window: "" }} />
+        </UiActionRow>
+      </Example>
     </>
   );
 }
diff --git a/app/(site)/(components-ui)/components-ui/examples/charts.tsx b/app/(site)/(components-ui)/components-ui/examples/charts.tsx
index b11112b8..cccbdd75 100644
--- a/app/(site)/(components-ui)/components-ui/examples/charts.tsx
+++ b/app/(site)/(components-ui)/components-ui/examples/charts.tsx
@@ -45,6 +45,20 @@ const visitors: UiChartSpec = {
   xFormat: "date",
 };
 
+// A paperback that costs $4.60 to print: 50% below $9.99, 60% from $9.99, so the line steps up there.
+const royaltyCurve: UiChartSpec = (() => {
+  const royalty = (cents: number) => (Math.round(cents * (cents >= 999 ? 0.6 : 0.5)) - 460) / 100;
+  const prices = [920, 998, 999, ...Array.from({ length: 21 }, (_, index) => 1000 + index * 100)];
+  return {
+    format: "currency",
+    kind: "line",
+    marks: [{ label: "Your price", x: 14.99, y: royalty(1499) }],
+    series: [{ id: "royalty", label: "Royalty per sale", points: prices.map((cents): UiChartPoint => [cents / 100, royalty(cents)]) }],
+    title: "Royalty by list price",
+    xFormat: "currency",
+  };
+})();
+
 const minute = 60_000;
 const rawLatency = (() => {
   const random = seeded(9);
@@ -161,6 +175,79 @@ const signups: UiChartSpec = {
   xFormat: "date",
 };
 
+const trialFunnel: UiChartSpec = {
+  format: "number",
+  height: 280,
+  kind: "funnel",
+  stages: [
+    { id: "visitors", label: "Visitors", value: 4800 },
+    { id: "signups", label: "Signups", value: 640 },
+    { id: "trials", label: "Trials", value: 200 },
+    { id: "paid", label: "Paid", value: 22 },
+  ],
+  title: "Visitors to paid customers",
+};
+
+const goal: UiChartSpec = { format: "currency", height: 240, kind: "gauge", label: "of $10,000 MRR goal", max: 10_000, title: "MRR goal", value: 6_400 };
+
+const costs: UiChartSpec = {
+  format: "currency",
+  height: 280,
+  kind: "treemap",
+  parts: [
+    { id: "hosting", label: "Hosting", value: 420 },
+    { id: "database", label: "Database", value: 260 },
+    { id: "email", label: "Email", value: 90 },
+    { id: "analytics", label: "Analytics", value: 60 },
+    { id: "monitoring", label: "Monitoring", value: 40 },
+    { id: "backups", label: "Backups", value: 30 },
+    { id: "domains", label: "Domains", value: 25 },
+  ],
+  title: "Monthly costs",
+};
+
+const mrrFlow: UiChartSpec = {
+  format: "currency",
+  height: 300,
+  kind: "sankey",
+  links: [
+    { source: "start", target: "kept", value: 8200 },
+    { source: "start", target: "churned", value: 600 },
+    { source: "start", target: "contracted", value: 200 },
+    { source: "kept", target: "end", value: 8200 },
+    { source: "new", target: "end", value: 1400 },
+    { source: "expansion", target: "end", value: 500 },
+  ],
+  nodes: [
+    { id: "start", label: "Starting MRR" },
+    { id: "new", label: "New" },
+    { id: "expansion", label: "Expansion" },
+    { id: "kept", label: "Kept" },
+    { id: "churned", label: "Churned" },
+    { id: "contracted", label: "Contraction" },
+    { id: "end", label: "Ending MRR" },
+  ],
+  title: "Where this month's MRR came from and went",
+};
+
+const plans: UiChartSpec = {
+  axes: [
+    { label: "Price", max: 10 },
+    { label: "Storage", max: 10 },
+    { label: "Seats", max: 10 },
+    { label: "Support", max: 10 },
+    { label: "Integrations", max: 10 },
+  ],
+  format: "number",
+  height: 320,
+  kind: "radar",
+  series: [
+    { id: "starter", label: "Starter", values: [9, 4, 3, 5, 6] },
+    { id: "team", label: "Team", values: [5, 8, 9, 8, 7] },
+  ],
+  title: "Two plans compared",
+};
+
 const kilobytes = (text: string) => `${(new TextEncoder().encode(text).length / 1000).toFixed(1)} KB`;
 
 /** What a chart adds to the page HTML: the server drawing, and the data handed to the browser. */
@@ -196,6 +283,11 @@ export function ChartsExamples() {
         <LiveChartExample />
       </Example>
 
+      <Example components={["UiChart"]} note="Marks put labeled dots on a line, such as the person's own value on a curve." source="app/ui/charts/chart-option.ts" title="Line with a mark">
+        <UiChart spec={royaltyCurve} />
+        <Weight spec={royaltyCurve} />
+      </Example>
+
       <Example components={["UiChart"]} note="Stacked areas add up to the total." source="app/ui/charts/chart.tsx" title="Stacked area">
         <UiChart spec={storage} />
         <Weight spec={storage} />
@@ -226,6 +318,31 @@ export function ChartsExamples() {
         <Weight spec={activity} />
       </Example>
 
+      <Example components={["UiChart"]} note="Stages that narrow, in order. Hover a stage for its share of the first and the previous stage." source="app/ui/charts/chart.tsx" title="Funnel">
+        <UiChart spec={trialFunnel} />
+        <Weight note="funnel, gauge, treemap, sankey, and radar load their script only on pages that use them" spec={trialFunnel} />
+      </Example>
+
+      <Example components={["UiChart"]} note="One value against a scale, such as progress toward a goal." source="app/ui/charts/chart.tsx" title="Gauge">
+        <UiChart spec={goal} />
+        <Weight spec={goal} />
+      </Example>
+
+      <Example components={["UiChart"]} note="Parts of a total as blocks. Reads better than a donut when there are many parts." source="app/ui/charts/chart.tsx" title="Treemap">
+        <UiChart spec={costs} />
+        <Weight spec={costs} />
+      </Example>
+
+      <Example components={["UiChart"]} note="How amounts flow from one group to the next." source="app/ui/charts/chart.tsx" title="Flow">
+        <UiChart spec={mrrFlow} />
+        <Weight spec={mrrFlow} />
+      </Example>
+
+      <Example components={["UiChart"]} note="Several measures compared as shapes. Click a name to hide or show it." source="app/ui/charts/chart.tsx" title="Radar">
+        <UiChart spec={plans} />
+        <Weight spec={plans} />
+      </Example>
+
       <Example components={["UiStaticChart"]} note="Drawn on the server only, with no chart script and no hover. For articles and reference pages." source="app/ui/charts/chart-static.tsx" title="Static chart">
         <UiStaticChart spec={signups} />
         <Weight interactive={false} spec={signups} />
diff --git a/app/(site)/(components-ui)/components-ui/examples/page-layout.tsx b/app/(site)/(components-ui)/components-ui/examples/page-layout.tsx
index a6cbe494..9b97311b 100644
--- a/app/(site)/(components-ui)/components-ui/examples/page-layout.tsx
+++ b/app/(site)/(components-ui)/components-ui/examples/page-layout.tsx
@@ -8,6 +8,9 @@ import { PageHeader } from "@/app/ui/site/page-header";
 import { PageMeta } from "@/app/ui/site/page-meta";
 import { PageTitleIcon } from "@/app/ui/site/page-title-icon";
 import { ThemeToggle } from "@/app/ui/site/theme-toggle";
+import { UiButton, UiTextField } from "@/app/ui/controls";
+import { UiActionRow, UiPrimaryResult } from "@/app/ui/display";
+import { ToolFieldRow, ToolResult, ToolWorkbench } from "@/app/ui/tools/tool-workbench";
 import { Example } from "../gallery";
 import styles from "../components-ui.module.css";
 
@@ -60,6 +63,25 @@ export function PageLayoutExamples() {
         </div>
       </Example>
 
+      <Example components={["ToolWorkbench", "ToolFieldRow", "ToolResult"]} note="Every tool sits in this band: the shared working width, inputs in rows that fill it, the action row, and the result below one divider. A result whose inputs changed steps back with stale." source="app/ui/tools/tool-workbench.tsx" title="Tool workbench">
+        <ToolWorkbench label="Example tool">
+          <ToolFieldRow>
+            <UiTextField label="Drives" suffix="drives" value="4" />
+            <UiTextField label="Drive size" suffix="TB" value="8" />
+          </ToolFieldRow>
+          <UiActionRow>
+            <UiButton type="button" variant="primary">Calculate capacity</UiButton>
+            <UiButton type="button">Reset</UiButton>
+          </UiActionRow>
+          <ToolResult label="Example result">
+            <UiPrimaryResult detail="Example" label="Usable capacity" unit="TB" value="24" />
+          </ToolResult>
+          <ToolResult label="Stale example result" stale>
+            <UiPrimaryResult detail="Inputs changed" label="Usable capacity, stale" unit="TB" value="24" />
+          </ToolResult>
+        </ToolWorkbench>
+      </Example>
+
       <Example components={["AppShell", "PageCanvas"]} note="Every page uses the shared shell with a sidebar, and PageCanvas for each content section. This gallery uses both. See full layouts on their live pages." source="app/ui/site/app-shell.tsx, app/ui/site/page-canvas.tsx" title="Full page layouts">
         <ul className={styles.layoutLinks}>
           {fullLayouts.map((layout) => (
diff --git a/app/(site)/(components-ui)/components-ui/examples/results.tsx b/app/(site)/(components-ui)/components-ui/examples/results.tsx
index 6834ab10..b7eb60a6 100644
--- a/app/(site)/(components-ui)/components-ui/examples/results.tsx
+++ b/app/(site)/(components-ui)/components-ui/examples/results.tsx
@@ -2,7 +2,7 @@
 
 import { useState } from "react";
 import { UiButton, UiCopyAction, UiRawOutput } from "@/app/ui/controls";
-import { UiActionRow, UiAllocationBar, UiCodeOutput, UiKeyValueList, UiMetricGroup, UiPrimaryResult, UiProgressBar, UiResultLead, UiStatusWord, UiSteps, UiTimeline } from "@/app/ui/display";
+import { UiActionRow, UiAllocationBar, UiCodeOutput, UiRangeMarker, UiKeyValueList, UiMetricGroup, UiPrimaryResult, UiProgressBar, UiResultLead, UiStatusWord, UiSteps, UiTimeline, UiUnitGrid } from "@/app/ui/display";
 import { Example } from "../gallery";
 import styles from "../components-ui.module.css";
 
@@ -21,12 +21,26 @@ export function ResultsExamples() {
             items={[
               { id: "raw", label: "Raw", value: "32", unit: "TiB" },
               { id: "protection", label: "Protection", value: "8", unit: "TiB" },
-              { id: "reserve", label: "Reserve", value: "2.2", unit: "TiB" },
+              { id: "reserve", label: "Reserve", value: "2.2", unit: "TiB", hint: "Free space kept back so the pool stays fast." },
             ]}
           />
         </div>
       </Example>
 
+      <Example components={["UiMetricGroup"]} note="The list layout gives one row per number, label left and value right, for numbers people read down a column." source="app/ui/display.tsx" title="Supporting numbers as a list">
+        <div className={styles.stack}>
+          <UiMetricGroup
+            ariaLabel="Trial numbers"
+            items={[
+              { id: "not-paid", label: "Didn't pay", value: "460" },
+              { id: "per-paid", label: "Trials per paying customer", value: "12.5", hint: "How many trial starts it took for each one that paid." },
+              { id: "mrr", label: "New MRR", value: "$1,960.00" },
+            ]}
+            layout="list"
+          />
+        </div>
+      </Example>
+
       <Example components={["UiPrimaryResult"]} note="Tones mark a good, risky, or failing answer. Neutral is the default." source="app/ui/display.tsx" title="Result tones">
         <div className={styles.twoColumns}>
           <UiPrimaryResult label="Break-even ACoS" tone="success" unit="%" value="42" />
@@ -64,6 +78,40 @@ export function ResultsExamples() {
         </div>
       </Example>
 
+      <Example components={["UiRangeMarker"]} note="Where a value sits next to published ranges. Position only, never a grade. The hint names each range's source. An optional range under the track shows where the person's own value probably sits, such as at a small sample size." source="app/ui/display.tsx" title="Range marker">
+        <div className={styles.stack}>
+          <UiRangeMarker
+            ariaLabel="Your trial conversion rate next to published ranges"
+            bands={[
+              { id: "median", from: 4, to: 6, label: "Median, no-card trials", valueText: "4 to 6%", hint: "ChartMogul survey of 200 software products, January 2026." },
+              { id: "top", from: 10, to: 15, label: "Top quarter, no-card trials", valueText: "10 to 15%", hint: "ChartMogul survey of 200 software products, January 2026." },
+            ]}
+            max={30}
+            maxText="30%"
+            minText="0%"
+            range={{ from: 5.92, to: 10.72, label: "Likely range at 500 starts", valueText: "5.92 to 10.72%", hint: "The true rate is probably in this range. Fewer starts make it wider." }}
+            value={8}
+            valueText="8%"
+          />
+          <UiRangeMarker
+            ariaLabel="A value near the start of the scale"
+            bands={[{ id: "median", from: 4, to: 6, label: "Median", valueText: "4 to 6%" }]}
+            max={30}
+            maxText="30%"
+            minText="0%"
+            value={1.5}
+            valueText="1.5%"
+          />
+        </div>
+      </Example>
+
+      <Example components={["UiUnitGrid"]} note="A share of a group, as filled units out of 100. The last unit fills partly. Use it for rates of people or items. An optional target outlines the units up to a goal." source="app/ui/display.tsx" title="Unit grid">
+        <div className={styles.twoColumns}>
+          <UiUnitGrid ariaLabel="Paid out of every 100 who started" emptyLabel="Didn't pay" filled={13.22} filledLabel="Paid" target={{ amount: 20, label: "At 20%", valueText: "20 of every 100" }} valueText="13.22 of every 100" />
+          <UiUnitGrid ariaLabel="Drives that failed out of every 100" emptyLabel="Still running" filled={4.5} filledLabel="Failed" tone="neutral" valueText="4.5 of every 100" />
+        </div>
+      </Example>
+
       <Example components={["UiAllocationBar"]} note="Parts of one total. Pick the neutral, accent, or categorical palette." source="app/ui/display.tsx" title="Allocation bar">
         <div className={styles.stack}>
           <UiAllocationBar ariaLabel="Neutral allocation" formatValue={formatTiB} palette="neutral" segments={[{ id: "used", label: "Used", value: 21.8 }, { id: "free", label: "Free", value: 10.2 }]} total={32} />
diff --git a/app/(site)/(components-ui)/components-ui/examples/text-and-choices.tsx b/app/(site)/(components-ui)/components-ui/examples/text-and-choices.tsx
index 0cc1f153..21a5c8e9 100644
--- a/app/(site)/(components-ui)/components-ui/examples/text-and-choices.tsx
+++ b/app/(site)/(components-ui)/components-ui/examples/text-and-choices.tsx
@@ -33,6 +33,7 @@ export function TextAndChoicesExamples() {
   const [hourCycle, setHourCycle] = useState<12 | 24>(12);
   const [layout, setLayout] = useState("raidz1");
   const [format, setFormat] = useState("paperback");
+  const [trialType, setTrialType] = useState("no-card");
   const [marketplaces, setMarketplaces] = useState(["us", "uk"]);
   const [recordTypes, setRecordTypes] = useState(["a"]);
   const [keepFree, setKeepFree] = useState(false);
@@ -43,12 +44,29 @@ export function TextAndChoicesExamples() {
       <Example components={["UiTextField"]} source="app/ui/controls.tsx" title="Text field">
         <div className={styles.twoColumns}>
           <UiTextField label="DNS name" placeholder="example.com" required spellCheck={false} />
-          <UiTextField description="Shown under the field when it helps." label="Book title" placeholder="My first cookbook" />
+          <UiTextField description="Outside tools only. Tools use a hint." label="Book title" placeholder="My first cookbook" />
           <UiTextField error={domainError} label="Field with an error" onChange={setDomain} required spellCheck={false} value={domain} />
           <UiTextField label="Field with a suffix" placeholder="80" suffix="pages" />
         </div>
       </Example>
 
+      <Example components={["UiHint"]} note="A label most people wouldn't understand gets one sentence behind a ?. It opens on hover, keyboard focus, and tap. Every field takes a hint prop." source="app/ui/controls.tsx" title="Field hint">
+        <div className={styles.twoColumns}>
+          <UiTextField hint="Everyone who started a trial in the same month." inputMode="numeric" label="Trials started" placeholder="200" required />
+          <UiChoiceGroup
+            hint="A card upfront means they enter a card before the trial starts."
+            label="Trial type"
+            onChange={setTrialType}
+            options={[
+              { id: "no-card", label: "No card" },
+              { id: "card", label: "Card upfront" },
+              { id: "free-plan", label: "Free plan" },
+            ]}
+            value={trialType}
+          />
+        </div>
+      </Example>
+
       <Example components={["UiSearchField"]} source="app/ui/controls.tsx" title="Search field">
         <div className={styles.narrow}>
           <UiSearchField label="Filter records" onChange={setSearch} placeholder="Type to filter…" value={search} />
@@ -77,7 +95,7 @@ export function TextAndChoicesExamples() {
         </div>
       </Example>
 
-      <Example components={["UiChoiceGroup"]} note="Pick exactly one. Options can carry a short description." source="app/ui/controls.tsx" title="One choice">
+      <Example components={["UiChoiceGroup"]} note="Pick exactly one. Tools keep options to names. Outside tools, options can carry a short description." source="app/ui/controls.tsx" title="One choice">
         <div className={styles.twoColumns}>
           <UiChoiceGroup
             label="Layout"
diff --git a/app/(site)/(components-ui)/components-ui/sections.ts b/app/(site)/(components-ui)/components-ui/sections.ts
index 867d1c18..81a09d56 100644
--- a/app/(site)/(components-ui)/components-ui/sections.ts
+++ b/app/(site)/(components-ui)/components-ui/sections.ts
@@ -37,7 +37,7 @@ export const gallerySections: GallerySection[] = [
     label: "Text and choices",
     description: "Fields for typing, searching, picking a date or time, and choosing from options.",
     icon: TextCursorInput,
-    components: ["UiTextField", "UiSearchField", "UiTextArea", "UiSelect", "UiComboBox", "UiDatePicker", "UiTimeField", "UiDateTimePicker", "UiChoiceGroup", "UiMultiChoiceGroup", "UiCheckbox", "UiSwitch"],
+    components: ["UiTextField", "UiSearchField", "UiTextArea", "UiSelect", "UiComboBox", "UiDatePicker", "UiTimeField", "UiDateTimePicker", "UiChoiceGroup", "UiMultiChoiceGroup", "UiCheckbox", "UiSwitch", "UiHint"],
   },
   {
     slug: "numbers-and-sliders",
@@ -49,9 +49,9 @@ export const gallerySections: GallerySection[] = [
   {
     slug: "actions-and-forms",
     label: "Actions and forms",
-    description: "Buttons, form validation, copy and download actions, repeated rows, and hidden settings.",
+    description: "Buttons, form validation, copy, share, and download actions, repeated rows, and Advanced settings.",
     icon: MousePointerClick,
-    components: ["UiButton", "UiActionRow", "UiCopyAction", "UiDownloadAction", "UiRepeatableList", "UiDisclosure"],
+    components: ["UiButton", "UiActionRow", "UiCopyAction", "UiShareAction", "UiDownloadAction", "UiRepeatableList", "UiDisclosure"],
   },
   {
     slug: "file-uploads",
@@ -72,7 +72,7 @@ export const gallerySections: GallerySection[] = [
     label: "Results",
     description: "The main answer, supporting numbers, status words, progress, steps, timelines, and generated output.",
     icon: Gauge,
-    components: ["UiPrimaryResult", "UiResultLead", "UiMetricGroup", "UiKeyValueList", "UiStatusWord", "UiProgressBar", "UiAllocationBar", "UiSteps", "UiTimeline", "UiCodeOutput", "UiRawOutput"],
+    components: ["UiPrimaryResult", "UiResultLead", "UiMetricGroup", "UiKeyValueList", "UiStatusWord", "UiProgressBar", "UiAllocationBar", "UiRangeMarker", "UiUnitGrid", "UiSteps", "UiTimeline", "UiCodeOutput", "UiRawOutput"],
   },
   {
     slug: "tables",
@@ -84,7 +84,7 @@ export const gallerySections: GallerySection[] = [
   {
     slug: "charts",
     label: "Charts",
-    description: "Line, area, bar, donut, scatter, and heatmap charts from data, in both themes, with the page weight they add.",
+    description: "Line, area, bar, donut, scatter, heatmap, funnel, gauge, treemap, flow, and radar charts from data, in both themes, with the page weight they add.",
     icon: ChartColumn,
     components: ["UiChart", "UiStaticChart", "UiLiveChart"],
   },
@@ -133,9 +133,9 @@ export const gallerySections: GallerySection[] = [
   {
     slug: "page-layout",
     label: "Page layout",
-    description: "Page headers, title icons, the entry hero, page metadata, and brand pieces.",
+    description: "Page headers, title icons, the entry hero, page metadata, brand pieces, and the tool workbench.",
     icon: LayoutTemplate,
-    components: ["PageHeader", "PageTitleIcon", "CategoryIcon", "EntryHero", "PageMeta", "BrandWordmark", "ThemeToggle"],
+    components: ["PageHeader", "PageTitleIcon", "CategoryIcon", "EntryHero", "PageMeta", "BrandWordmark", "ThemeToggle", "ToolWorkbench", "ToolFieldRow", "ToolResult"],
   },
 ];
 
diff --git a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/article.mdx b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/article.mdx
index 9c09e2b3..82330ac5 100644
--- a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/article.mdx
+++ b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/article.mdx
@@ -1,74 +1,95 @@
 ## How is free trial conversion rate calculated?
 
-Take one cohort. Divide the accounts in it that paid within your window by all the accounts that started in it. Both numbers must come from the same group. [ChartMogul's trial-to-paid chart](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate) counts the same way.
+Divide the accounts that paid by the accounts that started a trial in the same cohort, then multiply by 100.
 
-<Formula title="Trial-to-paid rate">
+<Formula title="Trial to paid conversion rate">
 
-Rate = accounts in the cohort that paid within the window ÷ accounts that started in the cohort × 100
+Conversion rate = paid accounts from the cohort ÷ trial starts in the cohort × 100
 
 </Formula>
 
-A common mistake is dividing this month's payments by this month's starts. Someone who starts a trial on August 25 may pay in September, and that count misses them.
+40 paid out of 500 trial starts is 8%. [ChartMogul's trial-to-paid metric](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate) works the same way: it follows people who started a trial in one period and counts the ones who later paid.
 
-<Example title="100 trials started in August, with a 30-day window">
+The common mistake is dividing one month's new customers by the same month's trial starts. Those are different people.
 
-6 of them paid during August. By day 30 of each person's trial, 20 had paid.
+<Example title="100 trial starts in August">
 
-August payments ÷ August starts gives 6%. The cohort rate is 20%, because the 14 who paid in September started in August.
+20 of the 100 paid within 30 days, some of them in September. That cohort's rate is 20%.
 
-</Example>
+August's billing report shows only 6 of those first payments. Dividing 6 by 100 gives 6%, which mixes up the month someone paid with the month they started.
 
-The 20% is final only once someone who started on August 31 has had all 30 days. Until then, the tool marks it `Provisional`.
+</Example>
 
 ## What counts as a paid conversion?
 
-An account converts when its first payment goes through. These don't count:
+An account counts once its first payment goes through.
 
-- A card saved at signup. It isn't a payment until the charge succeeds.
-- A pending payment or a failed first invoice.
+- A card on file, a pending invoice, or a failed first charge isn't a payment.
+- Count each account once, in both the starts and the paid count. [Recurly counts trial starts per subscription](https://recurly.com/resources/report/state-of-subscriptions-acquisition/), so one account with two trial subscriptions counts twice there.
+- A first payment isn't a kept customer. Someone who pays once and cancels still counts as converted.
 
-In Stripe, check that the first invoice after the trial was paid, not only that the [subscription](https://docs.stripe.com/api/subscriptions/object) moved out of `trialing`. Count accounts, not subscriptions: a customer with two plans counts once.
+## How long should you wait before you count?
 
-## Why doesn't this match Stripe's trial conversion rate?
+Wait until every account in the cohort has had its full follow-up window. Before then, some people who will pay haven't yet, so the rate is low.
 
-[Stripe Billing's trial conversion rate](https://support.stripe.com/questions/calculating-trial-conversion-rate-in-billing?locale=en-GB) compares trials that converted in the last 30 days with trials that ended in the last 30 days. Those aren't the same people, so Stripe notes its rate can go above 100%.
+There's no standard window. [ChartMogul notes](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate) that a cohort's rate can still change after the signup month, as people pay later. Its 2026 survey counts conversions within six months. Pick one window that fits how long your customers take to decide, and use it for every cohort you compare.
 
-That number helps you spot a recent change. This calculator answers a different question: of the people who started together, how many paid?
+The calculator marks a cohort `Provisional` until its age reaches the window. Age counts from the cohort's last start, so the newest account has had the full window too.
 
 ## What is a good free trial conversion rate?
 
-There's no single good rate. Asking for a card upfront makes a big difference. Your product, price, trial length, and where signups come from matter too. These dated sources split their figures by trial type.
+There's no single good rate. It depends on whether people enter payment details to start, how long you wait, and who you sell to. Published figures also count conversions in different ways, so compare yours only with a figure that measures the same thing.
 
-| Source | Free trial, no card | Free trial, card upfront | Free plan |
+| Source | No card | Card upfront | Free plan |
 | --- | --- | --- | --- |
-| ChartMogul, Growth Unhinged, and ProductLed | Median 4 to 6%. Top quarter 10 to 15%. | Median 25 to 35%. Top quarter 50 to 60%. | Median 3 to 5%. Top quarter 8 to 12%. |
-| First Page Sage | 17.4 to 18.2% | 48.8 to 51% | 2.6 to 2.8% |
-| Recurly | 12% | 39% | Not reported |
+| ChartMogul survey, 2026 | Median 4 to 6%, top quarter 10 to 15% | Median 25 to 35%, top quarter 50 to 60% | Median 3 to 5%, top quarter 8 to 12% |
+| First Page Sage, 2022 to 2025 | Average 18.2% | Average 48.8% | Average 2.6% |
+| Recurly, 2022 | Average 12.0% | Average 39.0% | Not reported |
+| ChartMogul help center | Median 3%, trial type not stated | | |
 
-The median is the middle product in the survey. A product at the top-quarter figure did better than three in four others.
+Each source measured something different:
 
-Who each source measured:
+- [ChartMogul's SaaS Conversion Report](https://chartmogul.com/reports/saas-conversion-report/) surveyed 200 software products in January 2026, typically $1 million to $10 million ARR. It counts paid within six months, as each respondent estimated it.
+- [First Page Sage](https://firstpagesage.com/seo-blog/saas-free-trial-conversion-rate-benchmarks/), updated September 5, 2025, averages 86 SaaS companies from 2022 to 2025. The figures above are for organic traffic. One paid month counts, and there's no fixed window.
+- [Recurly](https://recurly.com/resources/report/state-of-subscriptions-acquisition/) averages 803 subscription sites from January to August 2022, including consumer services. It counts 22 million trial starts per subscription, not per account.
+- [ChartMogul's help center](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate) gives a 3% median for SaaS companies, with no sample size or window.
 
-- [ChartMogul, Growth Unhinged, and ProductLed 2026 SaaS Conversion Report](https://chartmogul.com/reports/saas-conversion-report/): a January 2026 survey of 200 software products, self-reported. A typical respondent had $1m to $10m in ARR. All models counted conversions within six months.
-- [First Page Sage](https://firstpagesage.com/seo-blog/saas-free-trial-conversion-rate-benchmarks/), updated September 2025: 86 of the agency's clients from 2022 to 2025, split by organic and paid traffic. Converted means one paid month.
-- [Recurly State of Subscriptions](https://recurly.com/resources/report/state-of-subscriptions-acquisition/), 2022 data: 22 million trials on 803 subscription sites, not only SaaS. Trials that asked for a card averaged 29 days. Trials that didn't averaged 39 days. Recurly counted subscriptions, not accounts, so one account could count more than once.
+The calculator shows only the ChartMogul ranges. They're the only figures here split by trial type with a fixed window. It shows them when your follow-up window is six months, or when you haven't set one. A shorter or longer window counts something different, so it gets no range. Even so, they're survey estimates, and the report doesn't say how many products fall in each trial type.
 
-<Note title="Use these as rough guides, not targets">
+<Note title="Small cohorts">
 
-Each source counts conversion its own way, so they don't agree. None of these sources reports figures for small indie SaaS by trial type and follow-up window.
+A rate from a few dozen trials can move a lot with one or two more payments. Check your likely range before comparing. If it covers the published median, your cohort is too small to tell the difference yet.
 
 </Note>
 
-A higher rate with a card upfront doesn't tell you which setup brings more customers. Fewer people may start when you ask for a card, so compare how many paid, not only the rate.
+## Why does a small cohort's rate swing so much?
+
+With few trials, chance plays a big part. 30 paid out of 42 is 71.43%, but the likely range runs from 56.43% to 82.84%.
+
+The likely range is a 95% [Wilson score interval](https://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval#Wilson_score_interval). It's the range of true rates that could easily have produced your counts. Four times as many trials make it about half as wide.
+
+## Does requiring a card upfront improve conversion?
+
+It raises the share of trial starts who pay, but fewer people start a trial. To compare the two, count paying customers per visitor, not just per trial.
+
+First Page Sage's averages show both effects:
+
+| Trial type, organic traffic | Visitor to trial | Trial to paid |
+| --- | --- | --- |
+| No card | 8.5% | 18.2% |
+| Card upfront | 2.5% | 48.8% |
 
-## How is a free plan different from a free trial?
+Multiplied out, both land between 1 and 2 paying customers per 100 visitors. These averages come from different companies, so treat them as a rough picture, not a forecast for yours.
 
-A free plan has no end date, so people can upgrade months after they sign up. Use a longer window, such as 180 days, and don't compare a free plan rate with a trial rate. 180 days matches the six months the ChartMogul report used.
+## Is new MRR from trials the same as revenue?
 
-## Is new MRR the same as revenue?
+No. New MRR is the monthly recurring revenue these paid accounts added: each monthly plan at its price, and each annual plan at a twelfth of its yearly price.
 
-No. New MRR is the monthly recurring amount these customers added, not the cash you collected. [ChartMogul's MRR definition](https://chartmogul.com/saas-metrics/mrr/) counts a $120 annual plan as $10 a month and leaves out one-time fees, such as setup charges.
+The ARR run rate is new MRR × 12, the same Annual Run Rate formula as [ChartMogul's glossary](https://chartmogul.com/reports/saas-go-to-market-report/). It's a pace, not revenue earned this year. It doesn't include churn, refunds, upgrades, or one-time fees.
 
-The ARR run rate is new MRR × 12. It isn't what you'll earn this year, because some of these customers will cancel. The tool counts only customers who paid and puts no price on those who didn't.
+## What to check next
 
-To total MRR across all your plans, use the [MRR calculator](/mrr-calculator). The [customer acquisition cost calculator](/customer-acquisition-cost-calculator) shows what each new paying customer cost to win. The [customer churn calculator](/customer-churn-calculator) shows how many of them stay.
+- [MRR calculator](/mrr-calculator): add these customers to your total monthly recurring revenue.
+- [Customer churn calculator](/customer-churn-calculator): see how many of them stay.
+- [Customer acquisition cost calculator](/customer-acquisition-cost-calculator): what it cost to win each one.
+- [Customer lifetime value calculator](/customer-lifetime-value-calculator): what a kept customer is worth.
diff --git a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/intro.mdx b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/intro.mdx
index 99b07019..5068fb24 100644
--- a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/intro.mdx
+++ b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/intro.mdx
@@ -1,3 +1,3 @@
-See what share of the people who started a free trial, or a free plan, paid within a set number of days. The calculator also tells you if the group is old enough to trust.
+Enter how many people started a free trial and how many of them paid. You get your trial-to-paid rate, how sure that rate is at your cohort's size, and where it sits next to published figures for your type of trial.
 
-Before you start, count how many accounts started in a month and how many of those same accounts have paid. Add a price to see the new MRR they brought in.
+Have the counts for one group that started together, such as everyone who started in August.
diff --git a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/usage.mdx b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/usage.mdx
index 13c3c1fe..f151c33e 100644
--- a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/usage.mdx
+++ b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/content/usage.mdx
@@ -1,33 +1,33 @@
 ## What to enter
 
-Pick the option that matches how people start. If they enter a card before the trial begins, pick `Free trial, card upfront`, even if you charge only at the end.
+1. Pick one cohort: everyone who started a trial in one period, such as August.
+2. Count how many of those same accounts paid, whenever they paid. Leave out payments from people who started in another month.
+3. Count accounts in both fields. If your billing tool counts subscriptions or seats, one customer can show up twice.
 
-A cohort is everyone who started in the same period, usually one month. Get the starts from your billing tool or your signup table. For paid, count only accounts from that same cohort whose first payment went through.
+Paid means the first payment went through. A card on file, a pending invoice, or a failed charge isn't a payment yet.
 
-The follow-up window is how many days each account gets to pay, counted from the day it started. For a 14-day trial, a 30-day window also catches people who pay a little late. Use the same window every time you compare.
+The `Window, activation, revenue, and cohorts` section is optional. Leave it closed and the answer uses your two counts alone.
 
-Cohort age is how many days have passed since the last account in the cohort started. An August cohort counted on October 15 is 45 days old.
-
-For new MRR, enter recurring prices only, without setup fees. With annual plans, pick `Monthly and annual plans` and enter the full yearly price. The tool divides it by 12.
+| Add | When you want to know |
+| --- | --- |
+| `Follow-up window` and `Cohort age` | Whether the cohort has had long enough to pay. A young cohort shows `Provisional` and the days left. |
+| `Activated` | Where people drop off. Use your own activation event, such as creating a first project, and count everyone who paid in it. |
+| `Target conversion` | How many more paying accounts you'd need to reach a higher rate. |
+| `Monthly price` and `Annual price` | The new MRR these customers added. With both prices, also enter how many paid accounts are on annual plans. |
+| `Other cohorts` | Whether the rate holds across months, channels, or plans. Each cohort needs its own accounts. |
 
 ## How to read the result
 
-`Complete` means every account in the cohort had the full window to pay. `Provisional` means some still have days left, so the rate can still go up.
-
-With several cohorts, the main rate is the total paid divided by the total starts of the complete cohorts. It isn't the average of each row's rate. A cohort with days left still shows in the table, but stays out of the main rate as long as the complete cohorts have at least one start. If they have none, the tool uses all cohorts and marks the rate `Provisional`.
+The big number is the share of your trial starts that paid, with the counts under it so you can check the division. The grid shows the same share as people out of every 100.
 
-With one cohort, the result also shows how many didn't pay within the window. Some may still pay later.
+The bar under it shows your rate as `You`. The line under the track is your likely range: where the true rate probably sits, given how many trials you counted. The colored bands are published medians and top quarters for the trial type you picked. They count payments within six months, so they show only when your follow-up window is six months or not set. With a 30-day window, the bar shows your rate and likely range alone.
 
-<Example title="Three months, a 30-day window, counted on October 15">
+With other cohorts, `All cohorts` divides total paid by total starts. It leaves out cohorts still marked `Provisional`, so a young month doesn't pull the rate down. If every cohort is still provisional, it combines them all, and its `?` says so.
 
-| Cohort | Starts | Paid | Age | Rate |
-| --- | --- | --- | --- | --- |
-| July | 400 | 60 | 76 days | 15.00% |
-| August | 500 | 70 | 45 days | 14.00% |
-| September | 450 | 30 | 15 days | 6.67%, 15 days left |
+<Example title="160 trial starts, 3 paid">
 
-The main rate is 14.44%: 130 paid out of 900 starts in July and August. September's 6.67% isn't ready to compare yet. Its last starts have had only 15 of their 30 days.
+The rate is 1.88%, and 157 didn't pay. The likely range runs from 0.63% to 5.37%.
 
-At an average price of $29 a month, the 160 paid customers from all three months add $4,640.00 of new MRR. September's 30 count here, because they've already paid.
+That range overlaps the published no-card median of 4 to 6%. With 160 trials, you can't yet tell whether your rate is lower than typical. A few more months of trials will narrow the range.
 
 </Example>
diff --git a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator-from-url.tsx b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator-from-url.tsx
new file mode 100644
index 00000000..5c14a050
--- /dev/null
+++ b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator-from-url.tsx
@@ -0,0 +1,17 @@
+"use client";
+
+import { useInitialQuery } from "@/app/ui/tools/use-initial-query";
+import { freeTrialInputFromQuery } from "@/lib/free-trial-conversion-calculator/engine";
+import { FreeTrialConversionCalculator } from "./free-trial-conversion-calculator";
+
+// Reads a shared link in the browser so the page stays static. A clean URL opens on the example.
+export function FreeTrialConversionFromUrl() {
+  const query = useInitialQuery();
+  const shared = query.key !== "default";
+  return (
+    <FreeTrialConversionCalculator
+      key={query.key}
+      initialInput={shared ? freeTrialInputFromQuery(query.get) : undefined}
+    />
+  );
+}
diff --git a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator.module.css b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator.module.css
index 75bc50b7..f1cc6ad7 100644
--- a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator.module.css
+++ b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator.module.css
@@ -1,195 +1,104 @@
-.workbench {
-  background: var(--color-surface);
-  border-block: 1px solid var(--color-border-strong);
-  grid-column: 1 / -1;
-  margin-inline: calc(-1 * var(--container-gutter));
+.form {
+  display: grid;
+  gap: var(--space-6);
   min-width: 0;
-  padding: var(--space-7) var(--container-gutter);
-  width: calc(100% + var(--container-gutter) + var(--container-gutter));
 }
 
-.content,
-.form,
-.results {
+.advanced {
   display: grid;
   gap: var(--space-6);
   min-width: 0;
+  padding-top: var(--space-5);
 }
 
-.content {
-  gap: var(--space-7);
-  margin-inline: auto;
-  max-width: 66rem;
-}
-
-.group,
-.resultGroup,
-.mrr {
+.cohorts {
   display: grid;
   gap: var(--space-4);
   min-width: 0;
 }
 
-.group h2,
-.resultGroup h2 {
+.cohortsLabel {
+  align-items: center;
+  display: flex;
   font-family: var(--font-display);
-  font-size: var(--text-h3);
-  font-weight: var(--weight-bold);
-  line-height: var(--line-heading);
-  margin: 0;
-}
-
-.groupTitle {
-  display: grid;
+  font-weight: var(--weight-semibold);
   gap: var(--space-2);
-  min-width: 0;
-}
-
-.helper {
-  color: var(--color-text-muted);
-  font-size: var(--text-small);
-  line-height: var(--line-body);
-  margin: 0;
 }
 
-.window {
-  max-width: 22rem;
-  min-width: 0;
-}
-
-.cohortList :global([data-repeatable-row]) {
+/* One line per cohort on wide screens: name, starts, paid, and age. Remove sits in the list's last column. */
+.cohortRow {
   align-items: start;
-}
-
-/* The shared tooltip uses max-content. A long cohort name then widens the page. */
-.cohortList :global([data-repeatable-row]) > :global(button[aria-label])::after {
-  content: none;
-  overflow: hidden;
-  white-space: normal;
-  width: 16rem;
-}
-
-.cohortList :global([data-repeatable-row]) > :global(button[aria-label]):hover::after,
-.cohortList :global([data-repeatable-row]) > :global(button[aria-label]):focus-visible::after {
-  content: attr(aria-label);
-}
-
-/* The remove action lines up with the inputs, below the visible labels. */
-.cohortList :global([data-repeatable-row]) > :global(button) {
-  margin-top: calc(var(--text-body) * var(--line-ui) + var(--space-2));
-}
-
-.cohort {
-  align-items: start;
-  border: 0;
   display: grid;
   gap: var(--space-4);
-  grid-template-columns: minmax(0, 1.2fr) repeat(3, minmax(0, 1fr));
-  margin: 0;
+  grid-template-columns: minmax(0, 1.4fr) repeat(3, minmax(0, 1fr));
   min-width: 0;
-  padding: 0;
 }
 
-.cohort > * {
+/*
+ * The answer and its grid of 100 lead, where the eye lands. Where the rate sits follows the
+ * answer, and the numbers to dig into follow the grid, on the same left edge.
+ */
+.summary {
+  align-items: start;
+  display: grid;
+  gap: var(--space-6) var(--space-8);
+  grid-template-areas:
+    "answer visual"
+    "position visual"
+    "position numbers";
+  grid-template-columns: minmax(0, 6fr) minmax(0, 5fr);
   min-width: 0;
 }
 
-.visuallyHidden {
-  clip: rect(0 0 0 0);
-  clip-path: inset(50%);
-  height: 1px;
-  overflow: hidden;
-  position: absolute;
-  white-space: nowrap;
-  width: 1px;
-}
-
-.mrrSettings {
-  align-items: start;
-  display: grid;
-  gap: var(--space-5);
-  grid-template-columns: minmax(8rem, 10rem) minmax(0, 1fr);
+.answer {
+  grid-area: answer;
   min-width: 0;
 }
 
-.mrrSettings > * {
+.grid {
+  grid-area: visual;
+  max-width: 14rem;
   min-width: 0;
 }
 
-.fieldGrid {
-  align-items: start;
+.position {
   display: grid;
-  gap: var(--space-5);
-  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: var(--space-4);
+  grid-area: position;
+  justify-items: start;
   min-width: 0;
 }
 
-.fieldGrid > * {
+.numbers {
+  grid-area: numbers;
   min-width: 0;
 }
 
-.results {
-  border-top: 1px solid var(--color-border);
-  overflow-wrap: anywhere;
-  padding-top: var(--space-6);
+.position > figure {
+  justify-self: stretch;
 }
 
-.results :global(th),
-.results :global(td) {
-  overflow-wrap: anywhere;
+.detail {
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--space-2) var(--space-4);
 }
 
-@media (min-width: 761px) {
-  .results :global(table) {
-    table-layout: fixed;
-    width: 100%;
-  }
+.status {
+  align-self: center;
 }
 
-.valueLines {
-  display: grid;
-  gap: var(--space-1);
+.share {
+  display: flex;
 }
 
-@media (max-width: 760px) {
-  .workbench {
-    padding-block: var(--space-5);
-  }
-
-  .content {
-    gap: var(--space-6);
-  }
-
-  .window {
-    max-width: none;
-  }
-
-  .mrrSettings,
-  .fieldGrid {
+@media (max-width: 720px) {
+  .cohortRow {
     grid-template-columns: minmax(0, 1fr);
   }
 
-  .currency {
-    max-width: 12rem;
-  }
-
-  .cohortList :global([data-repeatable-row]) {
-    border-bottom: 1px solid var(--color-border);
-    padding-bottom: var(--space-4);
-  }
-
-  .cohortList :global([data-repeatable-row]:last-child) {
-    border-bottom: 0;
-    padding-bottom: 0;
-  }
-
-  .cohortList :global([data-repeatable-row]) > :global(button) {
-    margin-top: 0;
-  }
-
-  /* One column keeps the long "Paid within N days" label from pushing its input out of line. */
-  .cohort {
-    gap: var(--space-3);
+  .summary {
+    grid-template-areas: "answer" "visual" "position" "numbers";
     grid-template-columns: minmax(0, 1fr);
   }
 }
diff --git a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator.tsx b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator.tsx
index 6fb718d5..37c8007f 100644
--- a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator.tsx
+++ b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/free-trial-conversion-calculator.tsx
@@ -1,70 +1,80 @@
 "use client";
 
 import { RotateCcw } from "lucide-react";
-import { useRef, useState, type FormEvent, type RefObject } from "react";
-import { UiButton, UiCheckbox, UiChoiceGroup, UiRepeatableList, UiSelect, UiTextField, uiOption } from "@/app/ui/controls";
+import { useEffect, useRef, useState, type FormEvent, type RefObject } from "react";
+import type { UiChartSpec } from "@/app/ui/charts/chart-option";
+import { UiLiveChart } from "@/app/ui/charts/chart-client";
+import {
+  UiButton,
+  UiChoiceGroup,
+  UiDisclosure,
+  UiHint,
+  UiRepeatableList,
+  UiSelect,
+  UiShareAction,
+  UiTextField,
+  uiOption,
+  uiSetSummary,
+} from "@/app/ui/controls";
 import {
   UiActionRow,
-  UiDataTable,
-  UiKeyValueList,
+  UiMetricGroup,
   UiPrimaryResult,
+  UiRangeMarker,
   UiStatus,
   UiStatusWord,
+  UiUnitGrid,
+  type UiMetric,
 } from "@/app/ui/display";
+import { ToolFieldRow, ToolResult, ToolWorkbench } from "@/app/ui/tools/tool-workbench";
 import {
+  FREE_TRIAL_EXAMPLE_INPUT,
   TRIAL_MAX_COHORTS,
   calculateFreeTrialConversion,
-  type FreeTrialConversionErrors,
-  type FreeTrialConversionInput,
-  type FreeTrialConversionValues,
-  type TrialCohortField,
-  type TrialCohortInput,
-  type TrialConversionRate,
-  type TrialFieldKey,
-  type TrialModel,
-  type TrialMrrMethod,
+  freeTrialShareParams,
+  type FreeTrialErrors,
+  type FreeTrialInput,
+  type FreeTrialValues,
+  type TrialCohortRowInput,
+  type TrialMaturity,
+  type TrialRate,
+  type TrialType,
 } from "@/lib/free-trial-conversion-calculator/engine";
 import { SAAS_ECONOMICS_CURRENCIES, type SaasEconomicsCurrency } from "@/lib/saas-economics/shared";
-import { PUBLISHED_FIGURES } from "./published-figures";
+import { PUBLISHED_WINDOW_DAYS, publishedRanges } from "./published-figures";
 import styles from "./free-trial-conversion-calculator.module.css";
 
-type StatusMessage = { text: string; tone: "neutral" | "danger" };
-type CohortDraft = TrialCohortInput & { id: string };
-type FormFields = Omit<FreeTrialConversionInput, "cohorts">;
-
-const CHANGED = "Inputs changed. Calculate again.";
+type Shown = { input: FreeTrialInput; values: FreeTrialValues | null };
+type TextKey = Exclude<keyof FreeTrialInput, "cohorts" | "trialType" | "currency">;
 
-const MODEL_OPTIONS = [
-  uiOption("trialNoCard", "Free trial, no card", "They try it without entering a card."),
-  uiOption("trialCardRequired", "Free trial, card upfront", "They enter a card to start, and they're charged when the trial ends unless they cancel."),
-  uiOption("freemium", "Free plan", "They sign up for a free plan with no end date."),
+const trialTypeOptions = [
+  uiOption("noCard", "No card"),
+  uiOption("cardUpfront", "Card upfront"),
+  uiOption("freePlan", "Free plan"),
 ];
+const currencyOptions = SAAS_ECONOMICS_CURRENCIES.map((currency) => uiOption(currency, currency));
+const advancedKeys: readonly TextKey[] = ["windowDays", "ageDays", "activated", "targetRate", "monthlyPrice", "annualPrice", "annualAccounts"];
+const basicKeys = new Set(["form", "trialType", "starts", "paid"]);
+const focusOrder = ["trialType", "starts", "paid", "windowDays", "ageDays", "activated", "targetRate", "currency", "monthlyPrice", "annualPrice", "annualAccounts"];
 
-function emptyCohort(id: string): CohortDraft {
-  return { id, label: "", starts: "", paid: "", ageDays: "" };
-}
+/* ---------------- formatting ---------------- */
 
-function emptyFields(): FormFields {
-  return {
-    model: "trialNoCard",
-    windowDays: "",
-    includeMrr: false,
-    currency: "USD",
-    mrrMethod: "average",
-    averageMonthly: "",
-    monthlyCustomers: "",
-    monthlyPrice: "",
-    annualCustomers: "",
-    annualPrice: "",
-  };
+function formatInteger(value: bigint): string {
+  return new Intl.NumberFormat("en-US", { maximumFractionDigits: 0 }).format(value);
 }
 
-/* ---------------- formatting ---------------- */
+function formatHundredths(hundredths: bigint): string {
+  const fraction = (hundredths % 100n).toString().padStart(2, "0").replace(/0+$/, "");
+  return `${formatInteger(hundredths / 100n)}${fraction ? `.${fraction}` : ""}%`;
+}
 
-const integerFormat = new Intl.NumberFormat("en-US", { maximumFractionDigits: 0 });
+function formatRate(rate: TrialRate): string {
+  if (rate.kind === "none") return "—";
+  return rate.roundedToZero ? "Under 0.01%" : formatHundredths(rate.hundredths);
+}
 
-function formatInteger(value: bigint | number): string {
-  return integerFormat.format(value);
+function rateNumber(rate: TrialRate): number {
+  return rate.kind === "rate" ? Number(rate.hundredths) / 100 : NaN;
 }
 
 function currencySymbol(currency: SaasEconomicsCurrency): string {
@@ -74,526 +84,533 @@ function currencySymbol(currency: SaasEconomicsCurrency): string {
 }
 
 function formatMoney(cents: bigint, currency: SaasEconomicsCurrency): string {
-  const fraction = (cents % 100n).toString().padStart(2, "0");
-  return `${currencySymbol(currency)}${formatInteger(cents / 100n)}.${fraction}`;
+  return `${currencySymbol(currency)}${formatInteger(cents / 100n)}.${(cents % 100n).toString().padStart(2, "0")}`;
 }
 
-function formatRate(rate: TrialConversionRate): string {
-  if (rate.kind === "notAvailable") return "Not available";
-  if (rate.roundedToZero) return "Under 0.01%";
-  const fraction = (rate.hundredths % 100n).toString().padStart(2, "0");
-  return `${formatInteger(rate.hundredths / 100n)}.${fraction}%`;
+function startsWord(type: TrialType, plural = true): string {
+  if (type === "freePlan") return plural ? "free signups" : "free signup";
+  return plural ? "trial starts" : "trial start";
 }
 
-function days(count: bigint | number): string {
-  return `${formatInteger(count)} ${count === 1n || count === 1 ? "day" : "days"}`;
-}
+/* ---------------- input helpers ---------------- */
 
-function plural(count: number, one: string, many: string): string {
-  return `${formatInteger(count)} ${count === 1 ? one : many}`;
+let rowCounter = 0;
+function emptyRow(): TrialCohortRowInput {
+  rowCounter += 1;
+  return { id: `cohort-${rowCounter}`, name: "", starts: "", paid: "", ageDays: "" };
 }
 
-function cohortName(label: string, index: number): string {
-  return label.trim() || `Cohort ${index + 1}`;
+function rowIsBlank(row: TrialCohortRowInput): boolean {
+  return [row.name, row.starts, row.paid, row.ageDays].every((value) => value.trim() === "");
 }
 
-function windowLabel(raw: string): string | null {
-  const text = raw.trim();
-  if (!/^\d+$/.test(text)) return null;
-  const value = Number(text);
-  return value >= 1 && value <= 730 ? days(value) : null;
+function advancedCount(input: FreeTrialInput): number {
+  const filled = advancedKeys.filter((key) => input[key].trim() !== "").length;
+  const priced = input.monthlyPrice.trim() !== "" || input.annualPrice.trim() !== "";
+  return filled + (priced ? 1 : 0) + input.cohorts.filter((row) => !rowIsBlank(row)).length;
 }
 
-function nouns(model: TrialModel) {
-  return model === "freemium"
-    ? { count: "Free signups", column: "Signups", lower: "free signups", lead: "Free plan to paid", none: "No signups", figures: "Published rates for free plans" }
-    : { count: "Trial starts", column: "Starts", lower: "trial starts", lead: "Free trial to paid", none: "No starts", figures: model === "trialCardRequired" ? "Published rates for trials with a card upfront" : "Published rates for trials with no card" };
+function hasAdvancedError(errors: FreeTrialErrors): boolean {
+  return Object.keys(errors).some((key) => !basicKeys.has(key));
 }
 
-/* ---------------- results ---------------- */
-
-function leadLines(values: FreeTrialConversionValues): { detail: string; maturity: { word: string; tone: "neutral" | "warning"; text: string } | null } {
-  const { combined, cohorts, model } = values;
-  const noun = nouns(model);
-  const window = days(values.windowDays);
-  const single = cohorts.length === 1;
-  const included = combined.includedIndexes.length;
-
-  let detail: string;
-  if (combined.rate.kind === "notAvailable") {
-    detail = `${noun.none} in ${single ? "this cohort" : "these cohorts"}, so there's no rate.`;
-  } else if (single) {
-    detail = `${formatInteger(combined.paid)} of ${formatInteger(combined.starts)} ${noun.lower} paid within ${window}. ${formatInteger(combined.notPaid)} didn't.`;
-  } else if (combined.basis === "complete") {
-    detail = `${formatInteger(combined.paid)} of ${formatInteger(combined.starts)} ${noun.lower} in ${plural(included, "complete cohort", "complete cohorts")} paid within ${window}.`;
-    if (combined.excludedMaturing > 0) {
-      detail += combined.excludedMaturing === 1
-        ? " 1 newer cohort is left out until its window ends."
-        : ` ${formatInteger(combined.excludedMaturing)} newer cohorts are left out until their windows end.`;
-    }
-  } else {
-    detail = `${formatInteger(combined.paid)} of ${formatInteger(combined.starts)} ${noun.lower} across ${plural(included, "cohort", "cohorts")} paid within ${window}.`;
-  }
-
-  if (combined.rate.kind === "notAvailable") return { detail, maturity: null };
-  if (combined.status === "complete") {
-    return {
-      detail,
-      maturity: {
-        word: "Complete",
-        tone: "neutral",
-        text: single ? `Every account had the full ${window}.` : `Every account in these cohorts had the full ${window}.`,
-      },
-    };
-  }
-  const first = cohorts[0];
-  const text = single && first.maturity.status === "maturing"
-    ? `The last accounts to start have ${formatInteger(first.maturity.daysLeft)} more ${first.maturity.daysLeft === 1n ? "day" : "days"} to pay. This rate can still rise.`
-    : `No cohort with starts has had the full ${window} yet.`;
-  return { detail, maturity: { word: "Provisional", tone: "warning", text } };
+function firstErrorKey(errors: FreeTrialErrors, input: FreeTrialInput): string | null {
+  const rowKeys = input.cohorts.flatMap((_, index) => ["name", "starts", "paid", "ageDays"].map((field) => `cohorts.${index}.${field}`));
+  return [...focusOrder, ...rowKeys, "cohorts"].find((key) => key in errors) ?? null;
 }
 
-function TrialResults({ resultRef, values }: { resultRef: RefObject<HTMLOutputElement | null>; values: FreeTrialConversionValues }) {
-  const noun = nouns(values.model);
-  const lead = leadLines(values);
-  const several = values.cohorts.length > 1;
-  const label = several && values.combined.basis === "complete" ? `${noun.lead}, complete cohorts` : noun.lead;
-  const figures = PUBLISHED_FIGURES.filter((source) => source.figures[values.model]);
-  const mrr = values.newMrr;
-  const anyMaturing = values.cohorts.some((cohort) => cohort.maturity.status === "maturing");
-
-  const mrrRows = mrr ? [
-    { label: "New MRR", value: formatMoney(mrr.mrrCents, mrr.currency) },
-    {
-      label: "How",
-      value: mrr.method === "average"
-        ? `${plural(Number(mrr.paidCustomers), "paid customer", "paid customers")} × ${formatMoney(mrr.averageMonthlyCents ?? 0n, mrr.currency)}`
-        : `${formatInteger(mrr.monthlyPlan?.customers ?? 0n)} monthly × ${formatMoney(mrr.monthlyPlan?.priceCents ?? 0n, mrr.currency)} + ${formatInteger(mrr.annualPlan?.customers ?? 0n)} annual × ${formatMoney(mrr.annualPlan?.annualPriceCents ?? 0n, mrr.currency)} ÷ 12`,
-    },
-    {
-      label: "ARR run rate",
-      value: (
-        <span className={styles.valueLines}>
-          <span>{formatMoney(mrr.runRateArrCents, mrr.currency)}</span>
-          <span className={styles.helper}>New MRR × 12. Not what you'll earn this year.</span>
-        </span>
-      ),
-    },
-  ] : [];
-  const mrrNotes = mrr ? [
-    mrr.mrrIsRounded ? "Rounded to the cent." : null,
-    anyMaturing ? "Includes customers from cohorts that still have days left." : null,
-  ].filter((note): note is string => note !== null) : [];
-
-  return (
-    <section aria-label="Conversion results" className={styles.results}>
-      <UiPrimaryResult
-        detail={(
-          <span className={styles.valueLines}>
-            <span>{lead.detail}</span>
-            {lead.maturity ? (
-              <span>
-                <UiStatusWord tone={lead.maturity.tone}>{lead.maturity.word}</UiStatusWord>{" "}
-                {lead.maturity.text}
-              </span>
-            ) : null}
-          </span>
-        )}
-        inputRef={resultRef}
-        label={label}
-        value={formatRate(values.combined.rate)}
-      />
-
-      {several ? (
-        <section aria-labelledby="trial-cohorts-title" className={styles.resultGroup}>
-          <h2 id="trial-cohorts-title">By cohort</h2>
-          <UiDataTable
-            ariaLabel="Conversion by cohort"
-            columns={[
-              { id: "cohort", label: "Cohort" },
-              { id: "starts", label: noun.column, align: "right" },
-              { id: "paid", label: "Paid", align: "right" },
-              { id: "rate", label: "Rate", align: "right" },
-              { id: "status", label: "Status" },
-            ]}
-            rows={values.cohorts.map((cohort) => ({
-              id: String(cohort.index),
-              cells: {
-                cohort: cohortName(cohort.label, cohort.index),
-                starts: formatInteger(cohort.starts),
-                paid: formatInteger(cohort.paid),
-                rate: formatRate(cohort.rate),
-                status: cohort.maturity.status === "complete"
-                  ? <UiStatusWord>Complete</UiStatusWord>
-                  : <UiStatusWord tone="warning">{`${days(cohort.maturity.daysLeft)} left`}</UiStatusWord>,
-              },
-            }))}
-          />
-        </section>
-      ) : null}
-
-      {mrr ? (
-        <section aria-labelledby="trial-mrr-title" className={styles.resultGroup}>
-          <h2 id="trial-mrr-title">New MRR from these customers</h2>
-          <UiKeyValueList rows={mrrRows} />
-          {mrrNotes.length > 0 ? <p className={styles.helper}>{mrrNotes.join(" ")}</p> : null}
-        </section>
-      ) : null}
-
-      <section aria-labelledby="trial-figures-title" className={styles.resultGroup}>
-        <h2 id="trial-figures-title">{noun.figures}</h2>
-        <UiDataTable
-          ariaLabel="Published conversion figures"
-          columns={[
-            { id: "source", label: "Source" },
-            { id: "measured", label: "Who was measured" },
-            { id: "reported", label: "Reported" },
-          ]}
-          rows={figures.map((source) => ({
-            id: source.id,
-            cells: {
-              source: (
-                <span className={styles.valueLines}>
-                  <a href={source.url} rel="noopener" target="_blank">{source.name}</a>
-                  <span className={styles.helper}>{source.date}</span>
-                </span>
-              ),
-              measured: source.measured,
-              reported: source.figures[values.model],
-            },
-          }))}
-        />
-        <p className={styles.helper}>
-          Rough guides, not targets. Each source counts conversion its own way. None of these sources reports figures for small indie SaaS by trial type and follow-up window.
-        </p>
-      </section>
-    </section>
-  );
+function calculate(input: FreeTrialInput) {
+  try {
+    return calculateFreeTrialConversion(input);
+  } catch {
+    return null;
+  }
 }
 
-/* ---------------- form ---------------- */
+/* ---------------- the tool ---------------- */
 
-export function FreeTrialConversionCalculator() {
-  const [cohorts, setCohorts] = useState<CohortDraft[]>(() => [emptyCohort("cohort-1")]);
-  const [fields, setFields] = useState<FormFields>(emptyFields);
-  const [errors, setErrors] = useState<FreeTrialConversionErrors>({});
-  const [result, setResult] = useState<FreeTrialConversionValues | null>(null);
-  const [status, setStatus] = useState<StatusMessage | null>(null);
-  const nextCohortId = useRef(2);
+export function FreeTrialConversionCalculator({ initialInput }: { initialInput?: FreeTrialInput }) {
+  const shared = initialInput !== undefined;
+  const [first] = useState(() => {
+    const input = initialInput ?? { ...FREE_TRIAL_EXAMPLE_INPUT, cohorts: [] };
+    const calculation = calculate(input);
+    return {
+      input,
+      shown: { input, values: calculation?.status === "valid" ? calculation.values : null } satisfies Shown,
+      errors: shared ? calculation?.errors ?? {} : {},
+    };
+  });
+  const [input, setInput] = useState<FreeTrialInput>(first.input);
+  const [shown, setShown] = useState<Shown>(first.shown);
+  const [errors, setErrors] = useState<FreeTrialErrors>(first.errors);
+  const [isExample, setIsExample] = useState(!shared);
+  const [isStale, setIsStale] = useState(false);
+  const [failed, setFailed] = useState(false);
+  const [advancedOpen, setAdvancedOpen] = useState(hasAdvancedError(first.errors));
+  const [focusTarget, setFocusTarget] = useState<string | null>(shared ? firstErrorKey(first.errors, first.input) : null);
   const formRef = useRef<HTMLFormElement>(null);
-  const resultRef = useRef<HTMLOutputElement>(null);
-
-  const model = fields.model as TrialModel;
-  const noun = nouns(model);
-  const paidLabel = windowLabel(fields.windowDays);
-  const atLimit = cohorts.length >= TRIAL_MAX_COHORTS;
-  const split = fields.mrrMethod === "split";
-
-  function clearForEdit(announce?: string) {
-    const hadResult = result !== null;
-    setErrors({});
-    setResult(null);
-    if (hadResult) setStatus({ text: CHANGED, tone: "neutral" });
-    else if (announce) setStatus({ text: announce, tone: "neutral" });
-    else if (status?.text !== CHANGED) setStatus(null);
-  }
-
-  function updateField<K extends keyof FormFields>(field: K, value: FormFields[K]) {
-    setFields((current) => ({ ...current, [field]: value }));
-    clearForEdit();
-  }
-
-  function updateCohort(id: string, field: TrialCohortField, value: string) {
-    setCohorts((current) => current.map((cohort) => cohort.id === id ? { ...cohort, [field]: value } : cohort));
-    clearForEdit();
+  const answerRef = useRef<HTMLOutputElement>(null);
+
+  // Focus waits for a render, so a field inside Advanced exists before it gets focus.
+  useEffect(() => {
+    if (!focusTarget) return;
+    if (focusTarget === "answer") answerRef.current?.focus();
+    else {
+      const target = focusTarget === "cohorts"
+        ? formRef.current?.querySelector<HTMLElement>("[data-repeatable-add]")
+        : formRef.current?.querySelector<HTMLElement>(`[data-focus-key="${focusTarget}"]`);
+      target?.focus();
+    }
+    setFocusTarget(null);
+  }, [focusTarget]);
+
+  function edit(next: FreeTrialInput, clearKeys: string[]) {
+    setInput(next);
+    setIsStale(true);
+    setFailed(false);
+    if (clearKeys.some((key) => key in errors)) {
+      setErrors((current) => {
+        const rest = { ...current };
+        for (const key of clearKeys) delete rest[key as keyof FreeTrialErrors];
+        return rest;
+      });
+    }
   }
 
-  function focusKey(key: string) {
-    requestAnimationFrame(() => {
-      formRef.current?.querySelector<HTMLElement>(`[data-focus-key="${key}"]`)?.focus();
-    });
+  function setField(key: TextKey | "trialType" | "currency", value: string) {
+    edit({ ...input, [key]: value }, [key]);
   }
 
-  function addCohort() {
-    if (atLimit) return;
-    const cohort = emptyCohort(`cohort-${nextCohortId.current++}`);
-    setCohorts((current) => current.length >= TRIAL_MAX_COHORTS ? current : [...current, cohort]);
-    clearForEdit(`Cohort ${cohorts.length + 1} added.`);
+  function setRow(id: string, field: keyof Omit<TrialCohortRowInput, "id">, value: string) {
+    const index = input.cohorts.findIndex((row) => row.id === id);
+    edit(
+      { ...input, cohorts: input.cohorts.map((row) => (row.id === id ? { ...row, [field]: value } : row)) },
+      [`cohorts.${index}.${field}`, ...(field === "ageDays" ? ["windowDays"] : [])],
+    );
   }
 
-  function removeCohort(id: string) {
-    const index = cohorts.findIndex((cohort) => cohort.id === id);
-    const name = index >= 0 ? cohortName(cohorts[index].label, index) : "Cohort";
-    if (cohorts.length === 1) {
-      // The list always keeps one row, so removing the only cohort clears it.
-      const cohort = emptyCohort(`cohort-${nextCohortId.current++}`);
-      setCohorts([cohort]);
-      clearForEdit(`${name} cleared.`);
-      focusKey("cohorts.0.label");
+  function submit(event?: FormEvent) {
+    event?.preventDefault();
+    const calculation = calculate(input);
+    if (!calculation) {
+      setFailed(true);
       return;
     }
-    setCohorts((current) => current.filter((cohort) => cohort.id !== id));
-    clearForEdit(`${name} removed.`);
-  }
-
-  function focusFirstError(nextErrors: FreeTrialConversionErrors) {
-    const order: TrialFieldKey[] = [
-      "model",
-      "windowDays",
-      ...cohorts.flatMap((_, index) => (["label", "starts", "paid", "ageDays"] as const)
-        .map((field) => `cohorts.${index}.${field}` as const)),
-      "cohorts",
-      "currency",
-      "mrrMethod",
-      ...(split
-        ? ["monthlyCustomers", "monthlyPrice", "annualCustomers", "annualPrice"] as const
-        : ["averageMonthly"] as const),
-    ];
-    const first = order.find((key) => nextErrors[key]);
-    if (!first) return;
-    if (first === "cohorts") {
-      requestAnimationFrame(() => formRef.current?.querySelector<HTMLElement>("[data-repeatable-add]")?.focus());
-    } else {
-      focusKey(first);
-    }
-  }
-
-  function submit(event: FormEvent<HTMLFormElement>) {
-    event.preventDefault();
-    setStatus(null);
-    try {
-      const calculation = calculateFreeTrialConversion({
-        ...fields,
-        cohorts: cohorts.map(({ label, starts, paid, ageDays }) => ({ label, starts, paid, ageDays })),
-      });
-      if (calculation.status === "invalid") {
-        setErrors(calculation.errors);
-        setResult(null);
-        if (calculation.errors.form) setStatus({ text: calculation.errors.form, tone: "danger" });
-        focusFirstError(calculation.errors);
-        return;
-      }
-      setErrors({});
-      setResult(calculation.values);
-      requestAnimationFrame(() => resultRef.current?.focus());
-    } catch {
-      setErrors({});
-      setResult(null);
-      setStatus({ text: "Couldn't calculate. Try again.", tone: "danger" });
+    setFailed(false);
+    setErrors(calculation.errors);
+    if (calculation.status === "valid") {
+      setShown({ input, values: calculation.values });
+      setIsExample(false);
+      setIsStale(false);
     }
+    const firstError = firstErrorKey(calculation.errors, input);
+    // Open Advanced whenever it holds an error, even when focus goes to a Basic field first.
+    if (hasAdvancedError(calculation.errors)) setAdvancedOpen(true);
+    setFocusTarget(firstError ?? "answer");
   }
 
   function reset() {
-    setCohorts([emptyCohort(`cohort-${nextCohortId.current++}`)]);
-    setFields(emptyFields());
+    const example = { ...FREE_TRIAL_EXAMPLE_INPUT, cohorts: [] };
+    const calculation = calculate(example);
+    setInput(example);
+    setShown({ input: example, values: calculation?.status === "valid" ? calculation.values : null });
     setErrors({});
-    setResult(null);
-    setStatus({ text: "Form reset.", tone: "neutral" });
-    focusKey("model");
+    setIsExample(true);
+    setIsStale(false);
+    setFailed(false);
+    setAdvancedOpen(false);
   }
 
-  const listNote = errors.cohorts ?? (atLimit ? `Up to ${TRIAL_MAX_COHORTS} cohorts` : undefined);
-
-  function moneyField(field: "averageMonthly" | "monthlyPrice" | "annualPrice", label: string) {
-    return (
-      <UiTextField
-        autoCapitalize="none"
-        dataFocusKey={field}
-        error={errors[field] ?? null}
-        inputMode="decimal"
-        label={label}
-        onChange={(value) => updateField(field, value)}
-        required
-        spellCheck={false}
-        suffix={fields.currency}
-        value={fields[field]}
-      />
-    );
-  }
-
-  function countField(field: "monthlyCustomers" | "annualCustomers", label: string) {
-    return (
-      <UiTextField
-        autoCapitalize="none"
-        dataFocusKey={field}
-        error={errors[field] ?? null}
-        inputMode="numeric"
-        label={label}
-        onChange={(value) => updateField(field, value)}
-        required
-        spellCheck={false}
-        value={fields[field]}
-      />
-    );
-  }
+  const type = (TRIAL_TYPES_SET.has(input.trialType) ? input.trialType : "noCard") as TrialType;
+  const startsLabel = type === "freePlan" ? "Free signups" : "Trial starts";
+  const currency = (SAAS_ECONOMICS_CURRENCIES as readonly string[]).includes(input.currency)
+    ? input.currency as SaasEconomicsCurrency : "USD";
+  const atMax = input.cohorts.length >= TRIAL_MAX_COHORTS;
+  // Advanced fields that become required once their partner is filled.
+  const needsWindow = [input.ageDays, ...input.cohorts.map((row) => row.ageDays)].some((value) => value.trim() !== "");
+  const needsPrices = input.annualAccounts.trim() !== "";
+  const needsAnnualAccounts = input.monthlyPrice.trim() !== "" && input.annualPrice.trim() !== "";
 
   return (
-    <section aria-label="Free trial conversion calculator" className={styles.workbench} data-tool-workbench>
-      <div className={styles.content}>
-        <form aria-label="Free trial conversion inputs" className={styles.form} noValidate onSubmit={submit} ref={formRef}>
-          <UiChoiceGroup
-            dataFocusKey="model"
-            error={errors.model ?? null}
-            label="What people sign up for"
-            onChange={(value) => {
-              if (!MODEL_OPTIONS.some((option) => option.id === value)) return;
-              updateField("model", value);
-            }}
-            options={MODEL_OPTIONS}
+    <ToolWorkbench label="Free trial conversion calculator">
+      <form className={styles.form} noValidate onSubmit={submit} ref={formRef}>
+        <UiChoiceGroup
+          dataFocusKey="trialType"
+          error={errors.trialType}
+          hint="Card upfront means people enter payment details to start the trial."
+          label="Trial type"
+          required
+          onChange={(value) => setField("trialType", value)}
+          options={trialTypeOptions}
+          value={input.trialType}
+        />
+        <ToolFieldRow>
+          <UiTextField
+            dataFocusKey="starts"
+            error={errors.starts}
+            hint="Everyone who started in one period, such as August, counting each account once."
+            inputMode="numeric"
+            label={startsLabel}
+            onChange={(value) => setField("starts", value)}
             required
-            value={fields.model}
+            value={input.starts}
           />
-
-          <div className={styles.window}>
-            <UiTextField
-              autoCapitalize="none"
-              dataFocusKey="windowDays"
-              description="Days each account gets to pay, counted from the day it started."
-              error={errors.windowDays ?? null}
-              inputMode="numeric"
-              label="Follow-up window"
-              onChange={(value) => updateField("windowDays", value)}
-              required
-              spellCheck={false}
-              suffix="days"
-              value={fields.windowDays}
-            />
-          </div>
-
-          <section aria-labelledby="trial-cohort-title" className={styles.group}>
-            <div className={styles.groupTitle}>
-              <h2 id="trial-cohort-title">Cohorts</h2>
-              <p className={styles.helper}>A cohort is everyone who started in the same period, such as one month. Count each account once. Paid means the first payment went through. A card on file isn&apos;t a payment.</p>
-            </div>
-            <div className={styles.cohortList}>
+          <UiTextField
+            dataFocusKey="paid"
+            error={errors.paid}
+            hint="Accounts from those starts whose first payment went through."
+            inputMode="numeric"
+            label="Paid"
+            onChange={(value) => setField("paid", value)}
+            required
+            value={input.paid}
+          />
+        </ToolFieldRow>
+
+        <UiDisclosure
+          isExpanded={advancedOpen}
+          label="Window, activation, revenue, and cohorts"
+          onExpandedChange={setAdvancedOpen}
+          summary={uiSetSummary(advancedCount(input))}
+        >
+          <div className={styles.advanced}>
+            <ToolFieldRow>
+              <UiTextField
+                dataFocusKey="windowDays"
+                error={errors.windowDays}
+                hint="Days each account had to pay, counted from its own start."
+                inputMode="numeric"
+                label="Follow-up window"
+                onChange={(value) => setField("windowDays", value)}
+                required={needsWindow}
+                suffix="days"
+                value={input.windowDays}
+              />
+              <UiTextField
+                dataFocusKey="ageDays"
+                error={errors.ageDays}
+                hint="Days from this cohort's last start to the day you counted paid."
+                inputMode="numeric"
+                label="Cohort age"
+                onChange={(value) => edit({ ...input, ageDays: value }, ["ageDays", "windowDays"])}
+                suffix="days"
+                value={input.ageDays}
+              />
+              <UiTextField
+                dataFocusKey="activated"
+                error={errors.activated}
+                hint="Starts that reached your activation event, counting everyone who paid."
+                inputMode="numeric"
+                label="Activated"
+                onChange={(value) => setField("activated", value)}
+                value={input.activated}
+              />
+              <UiTextField
+                dataFocusKey="targetRate"
+                error={errors.targetRate}
+                hint="The conversion rate you're aiming for."
+                inputMode="decimal"
+                label="Target conversion"
+                onChange={(value) => setField("targetRate", value)}
+                suffix="%"
+                value={input.targetRate}
+              />
+            </ToolFieldRow>
+            <ToolFieldRow>
+              <UiSelect
+                dataFocusKey="currency"
+                error={errors.currency}
+                label="Currency"
+                onChange={(value) => setField("currency", value)}
+                options={currencyOptions}
+                value={input.currency || "USD"}
+              />
+              <UiTextField
+                dataFocusKey="monthlyPrice"
+                error={errors.monthlyPrice}
+                hint="Average monthly plan price for a new customer, without one-time fees."
+                inputMode="decimal"
+                label="Monthly price"
+                onChange={(value) => edit({ ...input, monthlyPrice: value }, ["monthlyPrice", "annualAccounts"])}
+                required={needsPrices}
+                suffix={currency}
+                value={input.monthlyPrice}
+              />
+              <UiTextField
+                dataFocusKey="annualPrice"
+                error={errors.annualPrice}
+                hint="Average yearly plan price, which counts as a twelfth each month."
+                inputMode="decimal"
+                label="Annual price"
+                onChange={(value) => edit({ ...input, annualPrice: value }, ["annualPrice", "annualAccounts"])}
+                required={needsPrices}
+                suffix={currency}
+                value={input.annualPrice}
+              />
+              <UiTextField
+                dataFocusKey="annualAccounts"
+                error={errors.annualAccounts}
+                hint="How many of the paid accounts chose a yearly plan."
+                inputMode="numeric"
+                label="On annual plans"
+                onChange={(value) => setField("annualAccounts", value)}
+                required={needsAnnualAccounts}
+                value={input.annualAccounts}
+              />
+            </ToolFieldRow>
+            <div className={styles.cohorts}>
+              <div className={styles.cohortsLabel}>
+                <span>Other cohorts</span>
+                <UiHint label="Other cohorts" text="Earlier months, channels, or plans, each with its own accounts." />
+              </div>
               <UiRepeatableList
-                addDescription={listNote}
+                addDescription={errors.cohorts ?? (atMax ? "Up to 12 cohorts" : undefined)}
                 addDescriptionIsError={Boolean(errors.cohorts)}
-                addDisabled={atLimit}
+                addDisabled={atMax}
                 addLabel="Add cohort"
-                ariaLabel="Cohorts"
-                items={cohorts}
-                onAdd={addCohort}
-                onRemove={removeCohort}
-                removeLabel={(cohort, index) => `Remove ${cohortName(cohort.label, index)}`}
-                renderItem={(cohort, index) => (
-                  <fieldset className={styles.cohort}>
-                    <legend className={styles.visuallyHidden}>{cohortName(cohort.label, index)}</legend>
+                ariaLabel="Other cohorts"
+                items={input.cohorts}
+                onAdd={() => edit({ ...input, cohorts: [...input.cohorts, emptyRow()] }, [])}
+                onRemove={(id) => {
+                  // Row errors are keyed by position, so they no longer match after a removal.
+                  setErrors((current) => Object.fromEntries(Object.entries(current).filter(([key]) => !key.startsWith("cohorts"))));
+                  edit({ ...input, cohorts: input.cohorts.filter((row) => row.id !== id) }, []);
+                }}
+                removeLabel={(row, index) => `Remove ${row.name.trim() || `cohort ${index + 2}`}`}
+                renderItem={(row, index) => (
+                  <div aria-label={row.name.trim() || `Cohort ${index + 2}`} className={styles.cohortRow} role="group">
                     <UiTextField
-                      autoCapitalize="none"
-                      className={styles.cohortName}
-                      dataFocusKey={`cohorts.${index}.label`}
-                      error={errors[`cohorts.${index}.label`] ?? null}
-                      label="Cohort name"
-                      onChange={(value) => updateCohort(cohort.id, "label", value)}
-                      placeholder="Aug 2026"
-                      value={cohort.label}
+                      dataFocusKey={`cohorts.${index}.name`}
+                      error={errors[`cohorts.${index}.name`]}
+                      label="Name"
+                      onChange={(value) => setRow(row.id, "name", value)}
+                      placeholder={`Cohort ${index + 2}`}
+                      value={row.name}
                     />
                     <UiTextField
-                      autoCapitalize="none"
                       dataFocusKey={`cohorts.${index}.starts`}
-                      error={errors[`cohorts.${index}.starts`] ?? null}
+                      error={errors[`cohorts.${index}.starts`]}
                       inputMode="numeric"
-                      label={noun.count}
-                      onChange={(value) => updateCohort(cohort.id, "starts", value)}
-                      required
-                      spellCheck={false}
-                      value={cohort.starts}
+                      label={startsLabel}
+                      onChange={(value) => setRow(row.id, "starts", value)}
+                      required={!rowIsBlank(row)}
+                      value={row.starts}
                     />
                     <UiTextField
-                      autoCapitalize="none"
                       dataFocusKey={`cohorts.${index}.paid`}
-                      error={errors[`cohorts.${index}.paid`] ?? null}
+                      error={errors[`cohorts.${index}.paid`]}
                       inputMode="numeric"
-                      label={paidLabel ? `Paid within ${paidLabel}` : "Paid within window"}
-                      onChange={(value) => updateCohort(cohort.id, "paid", value)}
-                      required
-                      spellCheck={false}
-                      value={cohort.paid}
+                      label="Paid"
+                      onChange={(value) => setRow(row.id, "paid", value)}
+                      required={!rowIsBlank(row)}
+                      value={row.paid}
                     />
                     <UiTextField
-                      autoCapitalize="none"
                       dataFocusKey={`cohorts.${index}.ageDays`}
-                      description={index === 0 ? "Days from the last start in this cohort to the day you counted." : undefined}
-                      error={errors[`cohorts.${index}.ageDays`] ?? null}
+                      error={errors[`cohorts.${index}.ageDays`]}
                       inputMode="numeric"
-                      label="Cohort age"
-                      onChange={(value) => updateCohort(cohort.id, "ageDays", value)}
-                      required
-                      spellCheck={false}
+                      label="Age"
+                      onChange={(value) => setRow(row.id, "ageDays", value)}
                       suffix="days"
-                      value={cohort.ageDays}
+                      value={row.ageDays}
                     />
-                  </fieldset>
+                  </div>
                 )}
               />
             </div>
-          </section>
-
-          <section aria-label="New MRR" className={styles.group}>
-            <UiCheckbox isSelected={fields.includeMrr} onChange={(selected) => updateField("includeMrr", selected)}>
-              Add new MRR from these customers
-            </UiCheckbox>
-            {fields.includeMrr ? (
-              <div className={styles.mrr}>
-                <div className={styles.mrrSettings}>
-                  <div className={styles.currency}>
-                    <UiSelect
-                      dataFocusKey="currency"
-                      error={errors.currency ?? null}
-                      label="Currency"
-                      onChange={(value) => {
-                        if (!SAAS_ECONOMICS_CURRENCIES.includes(value as SaasEconomicsCurrency)) return;
-                        updateField("currency", value);
-                      }}
-                      options={SAAS_ECONOMICS_CURRENCIES.map((currency) => uiOption(currency, currency))}
-                      required
-                      value={fields.currency}
-                    />
-                  </div>
-                  <UiChoiceGroup
-                    dataFocusKey="mrrMethod"
-                    error={errors.mrrMethod ?? null}
-                    label="Prices"
-                    onChange={(value) => {
-                      if (value !== "average" && value !== "split") return;
-                      updateField("mrrMethod", value satisfies TrialMrrMethod);
-                    }}
-                    options={[uiOption("average", "One average amount"), uiOption("split", "Monthly and annual plans")]}
-                    required
-                    value={fields.mrrMethod}
-                  />
-                </div>
-                {split ? (
-                  <>
-                    <div className={styles.fieldGrid}>
-                      {countField("monthlyCustomers", "Monthly-plan customers")}
-                      {moneyField("monthlyPrice", "Average monthly price")}
-                    </div>
-                    <div className={styles.fieldGrid}>
-                      {countField("annualCustomers", "Annual-plan customers")}
-                      {moneyField("annualPrice", "Average annual price")}
-                    </div>
-                  </>
-                ) : (
-                  <div className={styles.fieldGrid}>{moneyField("averageMonthly", "Average monthly price")}</div>
-                )}
-                <p className={styles.helper}>Recurring price only. Leave out setup and other one-time fees.</p>
-              </div>
-            ) : null}
-          </section>
-
-          <UiActionRow>
-            <UiButton type="submit" variant="primary">Calculate conversion</UiButton>
-            <UiButton onPress={reset} type="button" variant="secondary">
-              <RotateCcw aria-hidden="true" size={17} />
-              Reset
-            </UiButton>
-          </UiActionRow>
-          {status ? <UiStatus tone={status.tone}>{status.text}</UiStatus> : null}
-        </form>
-        {result ? <TrialResults resultRef={resultRef} values={result} /> : null}
+          </div>
+        </UiDisclosure>
+
+        <UiActionRow>
+          {failed ? <UiStatus tone="danger">Couldn&apos;t calculate. Try again.</UiStatus> : isStale ? <UiStatus>Inputs changed</UiStatus> : null}
+          <UiButton type="submit" variant="primary">Calculate conversion</UiButton>
+          <UiButton onPress={reset} type="button" variant="secondary">
+            <RotateCcw aria-hidden="true" size={17} />
+            Reset
+          </UiButton>
+        </UiActionRow>
+        {errors.form ? <UiStatus tone="danger">{errors.form}</UiStatus> : null}
+      </form>
+
+      <ToolResult label="Conversion result" stale={isStale}>
+        <ResultView answerRef={answerRef} isExample={isExample} shown={shown} />
+      </ToolResult>
+    </ToolWorkbench>
+  );
+}
+
+const TRIAL_TYPES_SET = new Set<string>(["noCard", "cardUpfront", "freePlan"]);
+
+/* ---------------- the result ---------------- */
+
+function maturityWord(maturity: TrialMaturity) {
+  if (maturity.status === "complete") return <UiStatusWord>Complete</UiStatusWord>;
+  if (maturity.status === "provisional") {
+    return <UiStatusWord tone="warning">Provisional, {formatInteger(maturity.daysLeft)} {maturity.daysLeft === 1n ? "day" : "days"} left</UiStatusWord>;
+  }
+  return null;
+}
+
+function ResultView({ answerRef, isExample, shown }: {
+  answerRef: RefObject<HTMLOutputElement | null>;
+  isExample: boolean;
+  shown: Shown;
+}) {
+  const { values } = shown;
+  const type = (values?.trialType ?? (TRIAL_TYPES_SET.has(shown.input.trialType) ? shown.input.trialType : "noCard")) as TrialType;
+  const label = type === "freePlan" ? "Free signup to paid" : "Trial to paid";
+  const hasRate = values?.rate.kind === "rate";
+  const rate = values ? rateNumber(values.rate) : NaN;
+  const status = isExample ? <UiStatusWord>Example</UiStatusWord> : values ? maturityWord(values.maturity) : null;
+
+  const detail = !values
+    ? "Enter your counts and calculate"
+    : !hasRate
+      ? `No ${startsWord(type)}`
+      : `${formatInteger(values.paid)} of ${formatInteger(values.starts)} ${startsWord(type, values.starts !== 1n)} paid${values.windowDays !== null ? ` within ${formatInteger(values.windowDays)} days` : ""}`;
+
+  const target = values?.target ?? null;
+  const targetText = target ? formatHundredths(target.hundredths) : "";
+  const targetAmount = target ? Number(target.hundredths) / 100 : NaN;
+
+  const metrics: UiMetric[] = [
+    { id: "not-paid", label: "Didn't pay", value: values ? formatInteger(values.notPaid) : "—" },
+    {
+      id: "per-paid",
+      label: type === "freePlan" ? "Signups per paying customer" : "Trials per paying customer",
+      hint: `How many ${startsWord(type)} it took, on average, for each one that paid.`,
+      value: values?.trialsPerPaidTenths != null ? `${formatInteger(values.trialsPerPaidTenths / 10n)}.${values.trialsPerPaidTenths % 10n}` : "—",
+    },
+  ];
+  if (values?.revenue) {
+    const { currency } = values.revenue;
+    metrics.push(
+      { id: "mrr", label: "New MRR", hint: "Paid accounts × their monthly amount, with annual plans as a twelfth.", value: formatMoney(values.revenue.mrrCents, currency) },
+      { id: "arr", label: "ARR run rate", hint: "New MRR × 12, a run rate, not revenue earned this year.", value: formatMoney(values.revenue.arrRunRateCents, currency) },
+    );
+  }
+  if (target) {
+    metrics.push({ id: "extra-paid", label: `Extra paid at ${targetText}`, value: formatInteger(target.extraPaid) });
+    if (target.extraMrrCents !== null && values?.revenue) {
+      metrics.push({ id: "extra-mrr", label: `Extra MRR at ${targetText}`, value: formatMoney(target.extraMrrCents, values.revenue.currency) });
+    }
+  }
+  if (values?.cohorts) metrics.push(allCohortsMetric(values.cohorts, values.windowDays));
+
+  // The published ranges count paid within six months. A different window isn't the same measure,
+  // so it gets no range. An unset window keeps them, and their labels name the six months.
+  const { bands: publishedBands, scaleMax } = publishedRanges[type];
+  const windowDays = values?.windowDays ?? null;
+  const windowMatches = windowDays === null || (windowDays >= PUBLISHED_WINDOW_DAYS.min && windowDays <= PUBLISHED_WINDOW_DAYS.max);
+  const bands = windowMatches ? publishedBands : [];
+  const high = values?.likely ? Number(values.likely.highHundredths) / 100 : 0;
+  const max = high > scaleMax ? Math.min(100, Math.ceil(high / 10) * 10) : scaleMax;
+
+  return (
+    <>
+      <div className={styles.summary}>
+        <div className={styles.answer}>
+          <UiPrimaryResult
+            detail={<span className={styles.detail}>{detail}{status ? <span className={styles.status}>{status}</span> : null}</span>}
+            inputRef={answerRef}
+            label={label}
+            value={values ? formatRate(values.rate) : "—"}
+          />
+        </div>
+        <div className={styles.grid}>
+          <UiUnitGrid
+            ariaLabel={`Paid out of every 100 ${startsWord(type)}`}
+            emptyLabel="Didn't pay"
+            filled={Number.isFinite(rate) ? rate : 0}
+            filledLabel="Paid"
+            target={target && targetAmount > rate ? { amount: targetAmount, label: `At ${targetText}`, valueText: `${targetText.replace("%", "")} of every 100` } : undefined}
+            valueText={hasRate ? `${formatRate(values!.rate).replace("%", "")} of every 100` : "none"}
+          />
+        </div>
+        <div className={styles.position}>
+          <UiRangeMarker
+            ariaLabel={bands.length ? "Your conversion rate next to published ranges" : "Your conversion rate and its likely range"}
+            bands={bands}
+            max={max}
+            maxText={`${max}%`}
+            minText="0%"
+            range={values?.likely ? {
+              from: Number(values.likely.lowHundredths) / 100,
+              to: Number(values.likely.highHundredths) / 100,
+              label: `Likely range at ${formatInteger(values.starts)} ${startsWord(type, values.starts !== 1n)}`,
+              valueText: `${formatHundredths(values.likely.lowHundredths).replace("%", "")} to ${formatHundredths(values.likely.highHundredths)}`,
+              hint: "Your true rate probably sits here, and fewer starts widen it.",
+            } : undefined}
+            value={rate}
+            valueText={values ? formatRate(values.rate) : "—"}
+          />
+          {!windowMatches && windowDays !== null ? (
+            <UiStatusWord>No published range for a {formatInteger(windowDays)}-day window</UiStatusWord>
+          ) : null}
+        </div>
+        <div className={styles.numbers}>
+          <UiMetricGroup ariaLabel="Supporting numbers" items={metrics} layout="list" />
+        </div>
       </div>
-    </section>
+
+      {values?.activation ? <FunnelChart type={type} values={values} /> : null}
+      {values?.cohorts ? <CohortChart values={values} /> : null}
+
+      {values ? (
+        <div className={styles.share}>
+          <UiShareAction params={freeTrialShareParams(shown.input)} />
+        </div>
+      ) : null}
+    </>
   );
 }
+
+function allCohortsMetric(cohorts: NonNullable<FreeTrialValues["cohorts"]>, windowDays: bigint | null): UiMetric {
+  const { combined, rows } = cohorts;
+  const counts = `${formatInteger(combined.paid)} of ${formatInteger(combined.starts)} starts`;
+  let hint = `${counts} across every cohort.`;
+  if (combined.basis === "settled" && combined.leftOut > 0 && windowDays !== null) {
+    const left = rows.filter((row) => row.maturity.status === "provisional").map((row) => row.name);
+    const names = left.length === 1 ? left[0] : `${left.slice(0, -1).join(", ")} and ${left.at(-1)}`;
+    hint = `${counts}, leaving out ${names} until ${left.length === 1 ? "it has" : "they have"} had ${formatInteger(windowDays)} days.`;
+  } else if (combined.status === "provisional") {
+    hint = `${counts}, all from cohorts still inside the window.`;
+  }
+  return { id: "all-cohorts", label: "All cohorts", hint, value: formatRate(combined.rate) };
+}
+
+function FunnelChart({ type, values }: { type: TrialType; values: FreeTrialValues }) {
+  const activation = values.activation!;
+  const share = (rate: TrialRate) => (rate.kind === "rate" ? `, ${formatRate(rate)}` : "");
+  const spec: UiChartSpec = {
+    kind: "funnel",
+    title: `Where ${startsWord(type)} drop off`,
+    format: "number",
+    height: 260,
+    stages: [
+      { id: "starts", label: type === "freePlan" ? "Free signups" : "Trial starts", value: Number(values.starts) },
+      { id: "activated", label: `Activated${share(activation.activationRate)}`, value: Number(activation.activated) },
+      { id: "paid", label: `Paid${share(activation.activatedToPaid)}`, value: Number(values.paid) },
+    ],
+  };
+  return <UiLiveChart spec={spec} />;
+}
+
+function CohortChart({ values }: { values: FreeTrialValues }) {
+  const rows = values.cohorts!.rows;
+  const spec: UiChartSpec = {
+    kind: "horizontal-bar",
+    title: values.windowDays !== null ? `Paid within ${formatInteger(values.windowDays)} days, by cohort` : "Paid, by cohort",
+    format: "percent",
+    height: Math.max(260, rows.length * 40 + 48),
+    // Long names would squeeze the bars on phones, so the axis shows a short name and the status on a second line.
+    categories: rows.map((row) => {
+      const name = row.name.length > 18 ? `${row.name.slice(0, 17).trimEnd()}…` : row.name;
+      if (row.rate.kind === "none") return `${name}\nno starts`;
+      if (row.maturity.status === "provisional") return `${name}\n${formatInteger(row.maturity.daysLeft)} ${row.maturity.daysLeft === 1n ? "day" : "days"} left`;
+      return name;
+    }),
+    series: [{ id: "rate", label: "Paid", values: rows.map((row) => (row.rate.kind === "rate" ? Number(row.rate.hundredths) / 100 : 0)) }],
+  };
+  return <UiLiveChart spec={spec} />;
+}
diff --git a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/page.tsx b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/page.tsx
index b0bd5fbe..b586e9c9 100644
--- a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/page.tsx
+++ b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/page.tsx
@@ -3,7 +3,7 @@ import { ToolPageShell } from "@/app/ui/tools/tool-page-shell";
 import { ToolPageArticle, ToolPageHeader } from "@/app/ui/site/tool-page-content";
 import { PageCanvas } from "@/app/ui/site/page-canvas";
 import { getRequiredToolPage } from "@/lib/tool-pages";
-import { FreeTrialConversionCalculator } from "./free-trial-conversion-calculator";
+import { FreeTrialConversionFromUrl } from "./free-trial-conversion-calculator-from-url";
 import Article from "./content/article.mdx";
 import Intro from "./content/intro.mdx";
 import Usage from "./content/usage.mdx";
@@ -14,7 +14,7 @@ export default async function FreeTrialConversionCalculatorPage() {
     <ToolPageShell toolPage={toolPage}>
       <PageCanvas>
         <ToolPageHeader icon={<Hourglass strokeWidth={2.2} />} intro={<Intro />} toolPage={toolPage} />
-        <FreeTrialConversionCalculator />
+        <FreeTrialConversionFromUrl />
         <ToolPageArticle>
           <Usage />
           <Article />
diff --git a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/published-figures.ts b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/published-figures.ts
index 13f70c60..8bfb3006 100644
--- a/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/published-figures.ts
+++ b/app/(site)/(tools)/(saas)/free-trial-conversion-calculator/published-figures.ts
@@ -1,50 +1,35 @@
-import type { TrialModel } from "@/lib/free-trial-conversion-calculator/engine";
+import type { UiRangeBand } from "@/app/ui/display";
+import type { TrialType } from "@/lib/free-trial-conversion-calculator/engine";
 
-// Copied from content_docs/free-trial-conversion-calculator/research.md, checked 2026-10-10.
-// Each source counts conversion its own way, so these are directional only.
-export type PublishedFigureSource = {
-  id: string;
-  name: string;
-  url: string;
-  date: string;
-  measured: string;
-  figures: Partial<Record<TrialModel, string>>;
-};
+const chartMogul = "ChartMogul survey of 200 software products, January 2026, counting paid within six months.";
+
+/** The survey counts paid within six months: 180 to 184 days, depending on the months. */
+export const PUBLISHED_WINDOW_DAYS = { min: 180n, max: 184n };
 
-export const PUBLISHED_FIGURES: readonly PublishedFigureSource[] = [
-  {
-    id: "chartmogul-2026",
-    name: "ChartMogul, Growth Unhinged, and ProductLed",
-    url: "https://chartmogul.com/reports/saas-conversion-report/",
-    date: "Survey, January 2026",
-    measured: "200 software products, self-reported. A typical respondent had $1m to $10m in ARR. B2B, consumer, and hybrid. All models counted conversions within six months.",
-    figures: {
-      trialNoCard: "Median 4 to 6%. Top quarter 10 to 15%.",
-      trialCardRequired: "Median 25 to 35%. Top quarter 50 to 60%.",
-      freemium: "Median 3 to 5%. Top quarter 8 to 12%.",
-    },
+/**
+ * Published ranges by trial type, with the scale each starts on. Labels name the six-month window,
+ * so a reader who hasn't set a window sees what the ranges measure.
+ */
+export const publishedRanges: Record<TrialType, { bands: UiRangeBand[]; scaleMax: number }> = {
+  noCard: {
+    bands: [
+      { id: "median", from: 4, to: 6, label: "No-card median, paid within 6 months", valueText: "4 to 6%", hint: chartMogul },
+      { id: "top", from: 10, to: 15, label: "No-card top quarter, paid within 6 months", valueText: "10 to 15%", hint: chartMogul },
+    ],
+    scaleMax: 30,
   },
-  {
-    id: "first-page-sage-2025",
-    name: "First Page Sage",
-    url: "https://firstpagesage.com/seo-blog/saas-free-trial-conversion-rate-benchmarks/",
-    date: "Updated September 2025",
-    measured: "86 of the agency's clients, 2022 to 2025. 71% B2B. Converted means one paid month.",
-    figures: {
-      trialNoCard: "18.2% from organic, 17.4% from paid ads.",
-      trialCardRequired: "48.8% from organic, 51% from paid ads.",
-      freemium: "2.6% from organic, 2.8% from paid ads.",
-    },
+  cardUpfront: {
+    bands: [
+      { id: "median", from: 25, to: 35, label: "Card-upfront median, paid within 6 months", valueText: "25 to 35%", hint: chartMogul },
+      { id: "top", from: 50, to: 60, label: "Card-upfront top quarter, paid within 6 months", valueText: "50 to 60%", hint: chartMogul },
+    ],
+    scaleMax: 80,
   },
-  {
-    id: "recurly-2022",
-    name: "Recurly",
-    url: "https://recurly.com/resources/report/state-of-subscriptions-acquisition/",
-    date: "2022 data",
-    measured: "22 million trials on 803 subscription sites, not only SaaS. Average trials ran 29 days with a card and 39 without. Recurly counted subscriptions, not accounts, so one account could count more than once.",
-    figures: {
-      trialNoCard: "12% average across sites.",
-      trialCardRequired: "39% average across sites.",
-    },
+  freePlan: {
+    bands: [
+      { id: "median", from: 3, to: 5, label: "Free plan median, paid within 6 months", valueText: "3 to 5%", hint: chartMogul },
+      { id: "top", from: 8, to: 12, label: "Free plan top quarter, paid within 6 months", valueText: "8 to 12%", hint: chartMogul },
+    ],
+    scaleMax: 30,
   },
-];
+};
diff --git a/app/(site)/(tools)/kdp-royalty-calculator/content/article.mdx b/app/(site)/(tools)/kdp-royalty-calculator/content/article.mdx
index 4f938091..5813fc46 100644
--- a/app/(site)/(tools)/kdp-royalty-calculator/content/article.mdx
+++ b/app/(site)/(tools)/kdp-royalty-calculator/content/article.mdx
@@ -1,14 +1,14 @@
 ## How is KDP royalty calculated?
 
-KDP pays you a share of the list price, minus what it costs to print or deliver the book.
+KDP pays you a share of the list price, then takes out the cost to print or deliver the book.
 
-<Formula title="KDP royalty per sale">
+<Formula title="KDP royalty per copy">
 
 Print book: `rate × list price - printing cost`
 
-eBook at 70%: `70% × (list price - delivery cost)`
+eBook on 70%: `70% × (list price - delivery cost)`
 
-eBook at 35%: `35% × list price`
+eBook on 35%: `35% × list price`
 
 </Formula>
 
@@ -16,36 +16,57 @@ eBook at 35%: `35% × list price`
 | --- | --- | --- |
 | Paperback or hardcover | Up to $9.98 | 50% |
 | Paperback or hardcover | $9.99 to $250 | 60% |
-| eBook | $2.99 to $12.99 | 70%, if you choose it |
-| eBook | Up to $200 | 35% |
+| Kindle eBook | $2.99 to $12.99 | 70%, if you choose it |
+| Kindle eBook | Up to $200 | 35% |
 
 Printing cost is a fixed fee plus a cost per page, set by trim size, ink, and paper. Some short books pay one flat fee instead. See KDP's [paperback](https://kdp.amazon.com/en_US/help/topic/G201834340) and [hardcover](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H) printing costs, and its [paperback](https://kdp.amazon.com/en_US/help/topic/G201834330) and [hardcover](https://kdp.amazon.com/en_US/help/topic/G77F3WPD3KQLJTFS) royalty rules.
 
-eBook delivery costs $0.15 per MB, at least $0.01, and applies only at 70%. KDP rounds the file size up to the next KB. See KDP's [eBook royalty rules](https://kdp.amazon.com/en_US/help/topic/G200634500). Larger files also need a higher lowest price. The [KDP minimum list price calculator](/kdp-minimum-list-price-calculator) lists the price bands.
+eBook delivery costs $0.15 per MB of the converted file, rounded up to the next KB, and at least $0.01. You pay it only on the 70% plan. See KDP's [digital book pricing](https://kdp.amazon.com/en_US/help/topic/G200634500).
 
-## Why does one cent change my paperback royalty by a dollar?
+## Why does one cent change a paperback royalty by $1?
 
-The print rate jumps from 50% to 60% at $9.99. For the 300-page paperback above, $9.98 earns $0.39 and $9.99 earns $1.39. If your price is just under $9.99, check that extra cent.
+The print rate jumps from 50% to 60% at $9.99. A 200-page paperback earns $1.59 at $9.98 and $2.59 at $9.99, because you get 60% of the price instead of 50%, while printing costs the same. If your price sits just under $9.99, check that extra cent.
 
-## When does 35% pay more than 70%?
+## Should you choose 35% or 70% for your eBook?
 
-It happens above $12.99 and with large files at low prices.
+From $2.99 to $12.99, 70% pays more as long as delivery costs less than half your price. A 2 MB eBook at $4.99 earns $3.28 on 70% and $1.75 on 35%.
 
-- A 5 MB eBook earns $8.57 at $12.99. At $13.00 it drops to 35% and earns $4.55. You'd need $24.48 to earn $8.57 again.
-- A 20 MB eBook costs $3.00 to deliver. At $2.99 it earns -$0.01 at 70%, but $1.05 at 35%.
+Two things can make 35% the better or the only choice:
 
-## Is royalty the same as profit?
+- Pricing above $12.99. KDP raised the top of the 70% band from $9.99 to $12.99 on July 7, 2026. Above it, every sale pays 35%. A 2 MB eBook earns $8.88 at $12.99, but $4.90 at $13.99. At 35% you'd need $25.36 to earn $8.88 again.
+- A large file at a low price. A 30 MB eBook costs $4.50 to deliver. At $2.99 the 70% plan pays nothing, while 35% pays $1.05.
 
-No. Royalty comes before your own costs, like editing, cover design, ads, and your time. To compare paperback and hardcover editions and add your costs, use the [KDP price and profit calculator](/kdp-price-profit-calculator).
+KDP also pays 35% in some stores, for books that are mostly public domain content, and in some cases when the eBook isn't priced at least 20% below its print edition. See KDP's [eBook list price rules](https://kdp.amazon.com/en_US/help/topic/G200634560).
+
+## What is the lowest list price KDP allows?
+
+For a print book, it's the price where your share just covers printing. A 200-page paperback costs $3.40 to print, so its lowest price is $6.80, where 50% pays exactly $3.40 and you earn nothing.
+
+A long book can skip the 50% rate entirely, because its lowest price lands above $9.98. A 600-page paperback costs $8.20 to print, so its lowest price is $13.67 at 60%. At $14.99 it earns $0.79.
+
+eBooks have a lowest price set by file size: $0.99 under 3 MB, $1.99 from 3 MB to under 10 MB, and $2.99 at 10 MB or more. The 70% plan starts at $2.99 for every size.
+
+The lowest price is a floor KDP sets, not a price it recommends. What readers will pay is a separate question.
+
+## What does Expanded Distribution pay?
+
+Expanded Distribution sells your paperback to bookstores and libraries. It pays 40% of the list price, minus printing, applicable taxes, and withholding. A 200-page paperback at $12.99 earns $1.80 there, against $4.39 on Amazon.com.
+
+KDP says this channel has its own lowest price, but doesn't publish how it's worked out. The calculator shows the break-even price instead, where 40% just covers printing: $8.50 for that paperback. KDP's real minimum may be higher. Your book's Rights & Pricing page in KDP shows the actual figure. See KDP's [Expanded Distribution](https://kdp.amazon.com/en_US/help/topic/GQTT4W3T5AYK7L45) page.
+
+## Is a KDP royalty the same as profit?
+
+No. A royalty is what KDP pays you before your own costs: editing, cover design, ads, and tax. To add your costs and compare editions, use the [KDP price and profit calculator](/kdp-price-profit-calculator).
 
 ## What doesn't this calculator cover?
 
-Results are estimates for Amazon.com in US dollars, using KDP rules checked on September 16, 2026. It doesn't cover:
+Results are estimates for Amazon.com in US dollars, using KDP's US rules, last checked October 11, 2026. The calculator doesn't cover:
 
-- Other Amazon stores, currencies, or Expanded Distribution.
-- Taxes, refunds, promotions, or price matching.
+- Other Amazon stores and currencies. Each has its own printing costs, VAT, and price rules.
+- Taxes, refunds, promotions, or price matching, which can change what you're paid.
+- Whether your book qualifies for 70% or Expanded Distribution, or whether KDP will accept it.
 - Kindle Unlimited page reads. Use the [Kindle Unlimited KENP earnings calculator](/kindle-unlimited-kenp-earnings-calculator).
-- Other 70% rules. KDP pays 35% for books that are mostly public domain content, and for eBooks priced less than 20% below your print edition on Amazon.
-- Whether KDP will accept your book.
 
-It runs in your browser and doesn't touch your Amazon account. Confirm your price in KDP before you publish.
+To find the price for a royalty you want, use the [KDP minimum list price calculator](/kdp-minimum-list-price-calculator). To set an ad bid from your break-even ACoS, use the [KDP book ads bid check](/kdp-break-even-acos-calculator).
+
+The calculator runs in your browser and never touches your Amazon account. Confirm your price in KDP before you publish.
diff --git a/app/(site)/(tools)/kdp-royalty-calculator/content/intro.mdx b/app/(site)/(tools)/kdp-royalty-calculator/content/intro.mdx
index 9c0170cd..66e742a3 100644
--- a/app/(site)/(tools)/kdp-royalty-calculator/content/intro.mdx
+++ b/app/(site)/(tools)/kdp-royalty-calculator/content/intro.mdx
@@ -1 +1 @@
-See what you earn from one sale of your paperback, hardcover, or Kindle eBook on Amazon.com, in US dollars. For a print book, have your trim size, page count, ink, and paper ready. For an eBook, have your file size.
+See what Amazon pays you for each copy of your paperback, hardcover, or Kindle eBook sold on Amazon.com, and what nearby prices would pay. Have your list price ready, plus the page count for a print book.
diff --git a/app/(site)/(tools)/kdp-royalty-calculator/content/usage.mdx b/app/(site)/(tools)/kdp-royalty-calculator/content/usage.mdx
index 2449e053..9dfbf459 100644
--- a/app/(site)/(tools)/kdp-royalty-calculator/content/usage.mdx
+++ b/app/(site)/(tools)/kdp-royalty-calculator/content/usage.mdx
@@ -1,23 +1,25 @@
 ## What to enter
 
-- Page count. Use your final interior file's page count, blank pages included. Odd counts round up to the next even number. No final file yet? Use the [KDP page count estimator](/kdp-page-count-estimator).
-- eBook file size. KDP measures the file itself, so its size can differ from your upload. Your upload's size is a fair first guess.
-- Royalty option. 70% works only from $2.99 to $12.99. Outside that range, the calculator uses 35% and tells you.
-- Monthly income target. Optional. It shows how many sales a month you'd need.
+- Page count: every page in your final interior file, blank pages included. KDP prints an even number of pages, so an odd count rounds up. No final file yet? Use the [KDP page count estimator](/kdp-page-count-estimator).
+- Trim size and paper: the calculator assumes 6 × 9 in on white paper. If your book differs, change them under Trim, paper, channel, and goal. Larger trims cost more per page.
+- eBook file size: KDP charges delivery on the file it converts, which can be larger or smaller than your upload. It shows that size on your book's pricing page. Until you have it, the calculator uses 2 MB.
+- Monthly royalty goal: optional. It shows how many copies a month earn that amount.
 
 ## How to read the result
 
-| Result | What it means |
+| Result | What it tells you |
 | --- | --- |
-| Royalty per sale | What Amazon pays you for one copy. |
-| Minimum list price | The lowest price KDP lets you set. For print, you earn little or nothing at this price. For an eBook, this shows the 35% file-size minimum, even when you select 70%. Prices below $2.99 use 35%. |
-| Royalty margin | Your royalty as a share of the price. |
-| Break-even ad spend | The most you can spend on ads per sale before the sale earns nothing. To turn it into a click bid, use the [KDP book ads bid calculator](/kdp-break-even-acos-calculator). |
-| Break-even ACoS | That limit as a share of the price. ACoS is ad spend divided by ad sales. |
-| Price table | Nearby prices, including where the rate changes. These aren't price suggestions. |
+| Royalty per copy | What KDP pays you for one sale at this price. |
+| Bar | Where the list price goes: your royalty, printing or delivery, and Amazon's share. |
+| Lowest list price | The lowest price KDP lets you set for this book. If you enter less, the answer switches to this price. |
+| Share of list price | Your royalty divided by the price. It's also your break-even ACoS: if ads cost more than this share of the sales they bring, each of those sales loses money. |
+| At $9.99, On the 35% plan, and similar | The next thing worth checking: a price where the rate changes, or what the other plan or channel pays. |
+| Chart | Your royalty at every nearby price, with your price marked. Hover to read any point. |
 
-<Example title="A 300-page paperback at $14.99">
+<Example title="A 200-page paperback at $12.99">
 
-A 6 × 9 in black and white paperback on white paper costs $1.00 + 300 × $0.012 = $4.60 to print. At $14.99 the rate is 60%, so you earn $8.99 - $4.60 = $4.39 per sale. A $500 monthly target needs 114 sales.
+A 6 × 9 in black and white paperback on white paper costs $1.00 + 200 × $0.012 = $3.40 to print. At $12.99 KDP pays 60%, which is $7.79. Take away printing and you earn $4.39 a copy. Amazon keeps the other $5.20.
+
+To earn $1,000 a month from this book, you'd need 228 sales.
 
 </Example>
diff --git a/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator-from-url.tsx b/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator-from-url.tsx
new file mode 100644
index 00000000..8f0bfda6
--- /dev/null
+++ b/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator-from-url.tsx
@@ -0,0 +1,12 @@
+"use client";
+
+import { useInitialQuery } from "@/app/ui/tools/use-initial-query";
+import { KdpRoyaltyCalculator, inputFromQuery, isSharedLink } from "./kdp-royalty-calculator";
+
+// Reads a shared link in the browser so the page stays static. A clean URL, or one with only
+// other parameters such as tracking tags, opens on the example and leaves the address alone.
+export function KdpRoyaltyCalculatorFromUrl() {
+  const query = useInitialQuery();
+  const shared = isSharedLink(query.get);
+  return <KdpRoyaltyCalculator initialInput={shared ? inputFromQuery(query.get) : undefined} key={query.key} />;
+}
diff --git a/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.module.css b/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.module.css
new file mode 100644
index 00000000..9ba7236c
--- /dev/null
+++ b/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.module.css
@@ -0,0 +1,59 @@
+.form {
+  display: grid;
+  gap: var(--space-6);
+  min-width: 0;
+}
+
+/* Basic rows pair a choice row on the left with one field on the right, so the choices get the wider share.
+   Nested under .form so it wins over the shared row's auto-fit columns. */
+.form .basicRow {
+  grid-template-columns: minmax(0, 3fr) minmax(0, 2fr);
+}
+
+/* Print refinements sit two to a row, so their choice rows stay on one line and a lone field keeps half the width. */
+.form .pairRow {
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+}
+
+.advanced {
+  display: grid;
+  gap: var(--space-6);
+  min-width: 0;
+  padding-top: var(--space-5);
+}
+
+/* The answer on the left and the price split beside it, centered on each other. */
+.top {
+  align-items: center;
+  display: grid;
+  gap: var(--space-8);
+  grid-template-columns: minmax(0, 2fr) minmax(0, 3fr);
+  min-width: 0;
+}
+
+.detail {
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--space-2) var(--space-4);
+}
+
+.status {
+  align-items: center;
+  display: inline-flex;
+  flex-wrap: wrap;
+  gap: var(--space-2);
+}
+
+.actions {
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--space-3);
+}
+
+@media (max-width: 720px) {
+  .form .basicRow,
+  .form .pairRow,
+  .top {
+    grid-template-columns: minmax(0, 1fr);
+  }
+}
diff --git a/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.tsx b/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.tsx
index 2e09b8fd..045b884b 100644
--- a/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.tsx
+++ b/app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.tsx
@@ -1,153 +1,598 @@
 "use client";
 
-import { CircleDollarSign, RotateCcw } from "lucide-react";
-import { useRef, useState, type FormEvent } from "react";
-import { UiButton, UiChoiceGroup, UiCopyAction, UiDisclosure, UiNumberField, UiSelect, UiTextField, uiOption } from "@/app/ui/controls";
-import { UiActionRow, UiDataTable, UiKeyValueList, UiPrimaryResult, UiStatus } from "@/app/ui/display";
-import { calculateKdpRoyalty, formatKdpMoney, formatKdpPercent, parseKdpRoyaltyMoney, type KdpRoyaltyFormat, type KdpRoyaltyInput, type KdpRoyaltyResult } from "@/lib/kdp/royalty.ts";
-import { getKdpInteriorOptions, getKdpPaperOptions, getKdpTrimOptions, interiorLabel, paperLabel, type KdpBinding, type KdpInterior } from "@/lib/kdp/specs.ts";
-import styles from "../../../ui/tools/kdp-tool.module.css";
+import { RotateCcw } from "lucide-react";
+import { useEffect, useRef, useState, type FormEvent, type ReactNode, type RefObject } from "react";
+import type { UiChartSpec } from "@/app/ui/charts/chart-option";
+import { UiLiveChart } from "@/app/ui/charts/chart-client";
+import {
+  UiButton,
+  UiChoiceGroup,
+  UiCopyAction,
+  UiDisclosure,
+  UiSelect,
+  UiShareAction,
+  UiTextField,
+  uiOption,
+  uiSetSummary,
+  type UiShareParams,
+} from "@/app/ui/controls";
+import {
+  UiActionRow,
+  UiAllocationBar,
+  UiMetricGroup,
+  UiPrimaryResult,
+  UiStatus,
+  UiStatusWord,
+  type UiAllocationSegment,
+  type UiMetric,
+} from "@/app/ui/display";
+import { ToolFieldRow, ToolResult, ToolWorkbench } from "@/app/ui/tools/tool-workbench";
+import {
+  calculateKdpRoyaltyEstimate,
+  type KdpRoyaltyCalculatorField,
+  type KdpRoyaltyCalculatorInput,
+  type KdpRoyaltyCalculatorValues,
+} from "@/lib/kdp/royalty-calculator.ts";
+import {
+  findKdpTrim,
+  getKdpInteriorOptions,
+  getKdpPaperOptions,
+  getKdpTrimOptions,
+  interiorLabel,
+  paperLabel,
+  type KdpBinding,
+  type KdpInterior,
+  type KdpPaper,
+} from "@/lib/kdp/specs.ts";
+import styles from "./kdp-royalty-calculator.module.css";
 
-const formatOptions = [uiOption("paperback", "Paperback"), uiOption("hardcover", "Hardcover"), uiOption("ebook", "Kindle ebook")];
-const ebookRateOptions = [uiOption("70", "70%"), uiOption("35", "35%")];
-const distributionNote = "Expanded Distribution excluded";
+type Input = KdpRoyaltyCalculatorInput;
+type Values = KdpRoyaltyCalculatorValues;
+type Errors = Partial<Record<KdpRoyaltyCalculatorField, string>>;
+type Format = Values["format"];
+type Shown = { input: Input; values: Values };
 
-function defaultInput(): KdpRoyaltyInput {
-  return { format: "paperback", trimId: "6x9", pageCount: 300, interior: "black-white", paper: "white", listPrice: 9.99, ebookFileSizeMB: 5, ebookRoyaltyOption: 70 };
+const EXAMPLE: Input = {
+  format: "paperback",
+  listPriceText: "12.99",
+  pageCountText: "200",
+  interior: "black-white",
+  trimId: "",
+  paper: "",
+  channel: "",
+  fileSizeText: "",
+  plan: "",
+  monthlyGoalText: "",
+};
+
+const formatOptions = [uiOption("paperback", "Paperback"), uiOption("hardcover", "Hardcover"), uiOption("ebook", "Kindle eBook")];
+const channelOptions = [uiOption("amazon", "Amazon.com"), uiOption("expanded", "Expanded Distribution")];
+const planOptions = [uiOption("70", "70%"), uiOption("35", "35%")];
+const advancedFields = new Set<KdpRoyaltyCalculatorField>(["trimId", "paper", "channel", "fileSize", "plan", "monthlyGoal"]);
+const focusOrder: KdpRoyaltyCalculatorField[] = ["format", "listPrice", "interior", "pageCount", "trimId", "paper", "channel", "fileSize", "plan", "monthlyGoal"];
+const seriesLabels = { amazon: "Amazon.com", expanded: "Expanded Distribution", plan70: "70% plan", plan35: "35% plan" } as const;
+
+/* ---------------- formatting ---------------- */
+
+const usd = new Intl.NumberFormat("en-US", { currency: "USD", style: "currency" });
+const whole = new Intl.NumberFormat("en-US", { maximumFractionDigits: 0 });
+
+function money(cents: number) {
+  return usd.format(cents / 100);
+}
+
+/** A goal like $1,000 reads without cents unless it has some. */
+function goalMoney(cents: number) {
+  return cents % 100 === 0 ? `$${whole.format(cents / 100)}` : money(cents);
+}
+
+function percent(basisPoints: number) {
+  return `${(basisPoints / 100).toFixed(1).replace(/\.0$/, "")}%`;
+}
+
+function megabytes(size: number) {
+  return `${new Intl.NumberFormat("en-US", { maximumFractionDigits: 2 }).format(size)} MB`;
+}
+
+function formatWord(format: Format) {
+  return format === "ebook" ? "Kindle eBook" : format;
+}
+
+/* ---------------- inputs ---------------- */
+
+function isFormat(value: string): value is Format {
+  return value === "paperback" || value === "hardcover" || value === "ebook";
+}
+
+/** Keeps print choices valid for a binding: a trim, interior, or paper it doesn't offer falls back to the default. */
+function fitPrintChoices(input: Input, binding: KdpBinding): Input {
+  const trimId = getKdpTrimOptions(binding).some((trim) => trim.id === input.trimId) ? input.trimId : "";
+  const interior = getKdpInteriorOptions(binding).includes(input.interior as KdpInterior) ? input.interior : "black-white";
+  const paper = getKdpPaperOptions(binding, interior as KdpInterior).includes(input.paper as KdpPaper) ? input.paper : "";
+  return { ...input, trimId, interior, paper };
+}
+
+/** A shared link's values. Unknown choices fall back to their defaults; typed values stay as written, so errors show. */
+/** The parameters a shared link carries. Anything else in the address, such as tracking tags, is ignored. */
+const shareParamNames = ["format", "price", "pages", "interior", "trim", "paper", "channel", "size", "plan", "goal"] as const;
+
+export function isSharedLink(get: (name: string) => string): boolean {
+  return shareParamNames.some((name) => get(name) !== "");
 }
 
-function errorFor(result: KdpRoyaltyResult | null, field: string) {
-  return result?.issues.find((issue) => issue.field === field && issue.severity === "error")?.message ?? null;
+export function inputFromQuery(get: (name: string) => string): Input {
+  const format = isFormat(get("format")) ? get("format") : "paperback";
+  const input: Input = {
+    format,
+    listPriceText: get("price"),
+    pageCountText: get("pages"),
+    interior: get("interior") || "black-white",
+    trimId: get("trim"),
+    paper: get("paper"),
+    channel: get("channel") === "expanded" ? "expanded" : "",
+    fileSizeText: get("size"),
+    plan: get("plan") === "35" ? "35" : "",
+    monthlyGoalText: get("goal"),
+  };
+  return format === "ebook" ? input : fitPrintChoices(input, format as KdpBinding);
 }
 
-function summary(values: NonNullable<KdpRoyaltyResult["values"]>) {
+function shareParams(input: Input): UiShareParams {
+  const print = input.format !== "ebook";
+  const params: Record<(typeof shareParamNames)[number], string | null> = {
+    format: input.format,
+    price: input.listPriceText.trim(),
+    pages: print ? input.pageCountText.trim() : null,
+    interior: print ? input.interior : null,
+    trim: print ? input.trimId : null,
+    paper: print ? input.paper : null,
+    channel: input.format === "paperback" ? input.channel : null,
+    size: print ? null : input.fileSizeText.trim(),
+    plan: print ? null : input.plan,
+    goal: input.monthlyGoalText.trim(),
+  };
+  return params;
+}
+
+function advancedCount(input: Input) {
+  const print = input.format !== "ebook";
   return [
-    `Format: ${values.format}`,
-    `List price: ${formatKdpMoney(values.listPriceCents)}`,
-    `Royalty: ${formatKdpMoney(values.royaltyCents)}`,
-    `Rate: ${values.effectiveRoyaltyRate}%`,
-    values.effectivePageCount === null ? "" : `Effective pages: ${values.effectivePageCount}`,
-    values.printingCostCents === null ? `Delivery: ${formatKdpMoney(values.deliveryCostCents ?? 0)}` : `Printing: ${formatKdpMoney(values.printingCostCents)}`,
-  ].join("\n");
-}
-
-export function KdpRoyaltyCalculator() {
-  const [input, setInput] = useState<KdpRoyaltyInput>(defaultInput);
-  const [listPriceText, setListPriceText] = useState("9.99");
-  const [monthlyTargetText, setMonthlyTargetText] = useState("");
-  const [result, setResult] = useState<KdpRoyaltyResult | null>(null);
-  const [status, setStatus] = useState("");
+    print && input.trimId !== "" && input.trimId !== "6x9",
+    print && input.paper !== "" && input.paper !== "white",
+    input.format === "paperback" && input.channel === "expanded",
+    !print && input.fileSizeText.trim() !== "",
+    !print && input.plan === "35",
+    input.monthlyGoalText.trim() !== "",
+  ].filter(Boolean).length;
+}
+
+function advancedLabel(format: string) {
+  if (format === "ebook") return "File size, plan, and goal";
+  if (format === "hardcover") return "Trim, paper, and goal";
+  return "Trim, paper, channel, and goal";
+}
+
+/* ---------------- the tool ---------------- */
+
+export function KdpRoyaltyCalculator({ initialInput }: { initialInput?: Input }) {
+  const shared = initialInput !== undefined;
+  const [first] = useState(() => {
+    const example = calculateKdpRoyaltyEstimate(EXAMPLE);
+    if (example.status !== "calculated") throw new Error("The KDP royalty example must calculate.");
+    const exampleShown: Shown = { input: EXAMPLE, values: example.values };
+    if (!initialInput) return { input: EXAMPLE, shown: exampleShown, errors: {} as Errors, stale: false };
+    const result = calculateKdpRoyaltyEstimate(initialInput);
+    return result.status === "calculated"
+      ? { input: initialInput, shown: { input: initialInput, values: result.values }, errors: result.fieldErrors as Errors, stale: false }
+      : { input: initialInput, shown: exampleShown, errors: result.fieldErrors, stale: true };
+  });
+  const [input, setInput] = useState<Input>(first.input);
+  const [shown, setShown] = useState<Shown>(first.shown);
+  const [errors, setErrors] = useState<Errors>(first.errors);
+  const [isExample, setIsExample] = useState(!shared || first.stale);
+  const [isStale, setIsStale] = useState(first.stale);
+  const [advancedOpen, setAdvancedOpen] = useState(Object.keys(first.errors).some((key) => advancedFields.has(key as KdpRoyaltyCalculatorField)));
+  const [focusTarget, setFocusTarget] = useState<string | null>(shared ? firstError(first.errors) : null);
   const formRef = useRef<HTMLFormElement>(null);
-  const resultRef = useRef<HTMLOutputElement>(null);
+  const answerRef = useRef<HTMLOutputElement>(null);
 
-  function update(next: Partial<KdpRoyaltyInput>) {
-    setInput((current) => ({ ...current, ...next }));
-    setResult(null);
-    setStatus("");
-  }
+  // Focus waits for a render, so a field inside Advanced exists before it gets focus.
+  useEffect(() => {
+    if (!focusTarget) return;
+    if (focusTarget === "answer") answerRef.current?.focus();
+    else formRef.current?.querySelector<HTMLElement>(`[data-focus-key="${focusTarget}"]`)?.focus();
+    setFocusTarget(null);
+  }, [focusTarget]);
 
-  function changeFormat(format: KdpRoyaltyFormat) {
-    if (format === "ebook") {
-      update({ format, ebookFileSizeMB: input.ebookFileSizeMB ?? 5, ebookRoyaltyOption: input.ebookRoyaltyOption ?? 70 });
-      return;
+  function edit(next: Input, fields: KdpRoyaltyCalculatorField[]) {
+    setInput(next);
+    setIsStale(true);
+    if (fields.some((field) => field in errors)) {
+      setErrors((current) => {
+        const rest = { ...current };
+        for (const field of fields) delete rest[field];
+        return rest;
+      });
     }
-    const binding = format as KdpBinding;
-    const trimOptions = getKdpTrimOptions(binding);
-    const trimId = trimOptions.some((trim) => trim.id === input.trimId) ? input.trimId : trimOptions[0].id;
-    const interiors = getKdpInteriorOptions(binding);
-    const interior = interiors.includes(input.interior as KdpInterior) ? input.interior : interiors[0];
-    const papers = getKdpPaperOptions(binding, interior as KdpInterior);
-    update({ format, trimId, interior, paper: papers[0] });
   }
 
-  function changeInterior(interior: KdpInterior) {
-    update({ interior, paper: getKdpPaperOptions(input.format as KdpBinding, interior)[0] });
+  function changeFormat(value: string) {
+    if (!isFormat(value)) return;
+    const next = { ...input, format: value };
+    edit(value === "ebook" ? next : fitPrintChoices(next, value), ["format", "trimId", "interior", "paper", "pageCount", "channel", "fileSize", "plan"]);
+  }
+
+  function changeInterior(value: string) {
+    edit(fitPrintChoices({ ...input, interior: value }, input.format as KdpBinding), ["interior", "paper", "pageCount"]);
   }
 
   function submit(event?: FormEvent) {
     event?.preventDefault();
-    const listPrice = parseKdpRoyaltyMoney(listPriceText);
-    const monthlyTarget = monthlyTargetText.trim() === "" ? undefined : parseKdpRoyaltyMoney(monthlyTargetText);
-    const next = calculateKdpRoyalty({ ...input, listPrice, monthlyTarget });
-    setResult(next);
-    setStatus(next.status === "invalid" ? "Fix highlighted fields." : next.issues.length ? "Royalty calculated; review possible issues." : "Royalty calculated.");
-    requestAnimationFrame(() => {
-      if (next.status === "valid") resultRef.current?.focus();
-      else formRef.current?.querySelector<HTMLElement>(`[data-focus-key="${next.issues.find((issue) => issue.severity === "error")?.field ?? "listPrice"}"]`)?.focus();
-    });
+    const result = calculateKdpRoyaltyEstimate(input);
+    const nextErrors: Errors = result.fieldErrors;
+    setErrors(nextErrors);
+    if (result.status === "calculated") {
+      setShown({ input, values: result.values });
+      setIsExample(false);
+      setIsStale(false);
+    }
+    const target = firstError(nextErrors);
+    if (target && advancedFields.has(target)) setAdvancedOpen(true);
+    setFocusTarget(target ?? "answer");
   }
 
   function reset() {
-    setInput(defaultInput());
-    setListPriceText("9.99");
-    setMonthlyTargetText("");
-    setResult(null);
-    setStatus("Calculator reset.");
-    requestAnimationFrame(() => formRef.current?.querySelector<HTMLElement>('[data-focus-key="format"]')?.focus());
+    const example = calculateKdpRoyaltyEstimate(EXAMPLE);
+    setInput(EXAMPLE);
+    if (example.status === "calculated") setShown({ input: EXAMPLE, values: example.values });
+    setErrors({});
+    setIsExample(true);
+    setIsStale(false);
+    setAdvancedOpen(false);
   }
 
-  const isEbook = input.format === "ebook";
-  const binding = isEbook ? "paperback" : input.format as KdpBinding;
-  const trimOptions = getKdpTrimOptions(binding);
-  const interiorOptions = getKdpInteriorOptions(binding);
-  const paperOptions = getKdpPaperOptions(binding, input.interior as KdpInterior);
-  const values = result?.values ?? null;
+  const format: Format = isFormat(input.format) ? input.format : "paperback";
+  const print = format !== "ebook";
+  const binding = (print ? format : "paperback") as KdpBinding;
+  const interiors = getKdpInteriorOptions(binding);
+  const papers = getKdpPaperOptions(binding, (interiors.includes(input.interior as KdpInterior) ? input.interior : "black-white") as KdpInterior);
+  const trimOptions = getKdpTrimOptions(binding).map((trim) => uiOption(trim.id, trim.label));
+
+  const goalField = (
+    <UiTextField
+      dataFocusKey="monthlyGoal"
+      error={errors.monthlyGoal}
+      hint="Shows how many copies a month earn this much."
+      inputMode="decimal"
+      label="Monthly royalty goal"
+      onChange={(value) => edit({ ...input, monthlyGoalText: value }, ["monthlyGoal"])}
+      suffix="USD"
+      value={input.monthlyGoalText}
+    />
+  );
 
   return (
-    <section aria-label="Royalty inputs and results" className={styles.tool} data-tool-workbench>
-      <form className={styles.form} onSubmit={submit} ref={formRef}>
-        <div className={styles.grid}>
-          <UiChoiceGroup dataFocusKey="format" label="Format" onChange={(value) => changeFormat(value as KdpRoyaltyFormat)} options={formatOptions} value={input.format} />
-          <UiTextField dataFocusKey="listPrice" error={errorFor(result, "listPrice")} inputMode="decimal" label="List price (USD)" onChange={(value) => { setListPriceText(value); setResult(null); setStatus(""); }} value={listPriceText} />
-          {!isEbook ? <>
-            <UiSelect dataFocusKey="trimId" error={errorFor(result, "trimId")} label="Trim size" onChange={(value) => update({ trimId: value })} options={trimOptions.map((trim) => uiOption(trim.id, trim.label))} value={input.trimId} />
-            <UiNumberField dataFocusKey="pageCount" error={errorFor(result, "pageCount")} label="Page count" min={1} onChange={(value) => update({ pageCount: value })} value={input.pageCount} />
-            <UiSelect dataFocusKey="interior" error={errorFor(result, "interior")} label="Interior" onChange={(value) => changeInterior(value as KdpInterior)} options={interiorOptions.map((interior) => uiOption(interior, interiorLabel(interior)))} value={input.interior} />
-            <UiSelect dataFocusKey="paper" error={errorFor(result, "paper")} label="Paper" onChange={(value) => update({ paper: value as KdpRoyaltyInput["paper"] })} options={paperOptions.map((paper) => uiOption(paper, paperLabel(paper)))} value={input.paper} />
-          </> : <>
-            <UiNumberField dataFocusKey="ebookFileSizeMB" error={errorFor(result, "ebookFileSizeMB")} label="Ebook file size" min={0.01} onChange={(value) => update({ ebookFileSizeMB: value })} step={0.01} suffix="MB" value={input.ebookFileSizeMB ?? 5} />
-            <UiChoiceGroup dataFocusKey="ebookRoyaltyOption" error={errorFor(result, "ebookRoyaltyOption")} label="Royalty option" onChange={(value) => update({ ebookRoyaltyOption: Number(value) as 35 | 70 })} options={ebookRateOptions} value={String(input.ebookRoyaltyOption ?? 70)} />
-          </>}
-          <UiTextField dataFocusKey="monthlyTarget" description="Optional target in USD" error={errorFor(result, "monthlyTarget")} inputMode="decimal" label="Monthly income target" onChange={(value) => { setMonthlyTargetText(value); setResult(null); setStatus(""); }} value={monthlyTargetText} />
-        </div>
-        <UiActionRow>
-          <div className={styles.actions}>
-            <UiButton onPress={reset} type="button"><RotateCcw aria-hidden="true" size={17} /> Reset</UiButton>
-            <UiButton type="submit" variant="primary"><CircleDollarSign aria-hidden="true" size={17} /> Calculate royalty</UiButton>
+    <ToolWorkbench label="KDP royalty calculator">
+      <form className={styles.form} noValidate onSubmit={submit} ref={formRef}>
+        <ToolFieldRow className={styles.basicRow}>
+          <UiChoiceGroup
+            dataFocusKey="format"
+            error={errors.format}
+            label="Format"
+            required
+            onChange={changeFormat}
+            options={formatOptions}
+            value={format}
+          />
+          <UiTextField
+            dataFocusKey="listPrice"
+            error={errors.listPrice}
+            hint="The price readers pay on Amazon.com, before any sale."
+            inputMode="decimal"
+            label="List price"
+            required
+            onChange={(value) => edit({ ...input, listPriceText: value }, ["listPrice"])}
+            suffix="USD"
+            value={input.listPriceText}
+          />
+        </ToolFieldRow>
+        {print ? (
+          <ToolFieldRow className={styles.basicRow}>
+            <UiChoiceGroup
+              dataFocusKey="interior"
+              error={errors.interior}
+              hint="Premium color prints richer images than standard color, and costs more."
+              label="Interior"
+              required
+              onChange={changeInterior}
+              options={interiors.map((interior) => uiOption(interior, interiorLabel(interior)))}
+              value={input.interior}
+            />
+            <UiTextField
+              dataFocusKey="pageCount"
+              error={errors.pageCount}
+              hint="Every page in your interior file, including blank pages."
+              inputMode="numeric"
+              label="Page count"
+              required
+              onChange={(value) => edit({ ...input, pageCountText: value }, ["pageCount"])}
+              suffix="pages"
+              value={input.pageCountText}
+            />
+          </ToolFieldRow>
+        ) : null}
+
+        <UiDisclosure
+          isExpanded={advancedOpen}
+          label={advancedLabel(format)}
+          onExpandedChange={setAdvancedOpen}
+          summary={uiSetSummary(advancedCount(input))}
+        >
+          <div className={styles.advanced}>
+            {print ? (
+              <>
+                <ToolFieldRow className={styles.pairRow}>
+                  <UiSelect
+                    dataFocusKey="trimId"
+                    error={errors.trimId}
+                    hint="Trims over 6.12 in wide or 9 in tall cost more per page."
+                    label="Trim size"
+                    onChange={(value) => edit({ ...input, trimId: value }, ["trimId", "pageCount"])}
+                    options={trimOptions}
+                    value={input.trimId || "6x9"}
+                  />
+                  {papers.length > 1 ? (
+                    <UiChoiceGroup
+                      dataFocusKey="paper"
+                      error={errors.paper}
+                      hint={papers.includes("groundwood") ? "Cream allows fewer pages, and groundwood is thinner and cheaper." : "Cream allows fewer pages than white."}
+                      label="Paper"
+                      onChange={(value) => edit({ ...input, paper: value }, ["paper", "pageCount"])}
+                      options={papers.map((paper) => uiOption(paper, paperLabel(paper)))}
+                      value={input.paper || "white"}
+                    />
+                  ) : null}
+                </ToolFieldRow>
+                <ToolFieldRow className={styles.pairRow}>
+                  {format === "paperback" ? (
+                    <UiChoiceGroup
+                      dataFocusKey="channel"
+                      error={errors.channel}
+                      hint="Expanded Distribution sells to bookstores and libraries, and pays 40% minus printing."
+                      label="Sales channel"
+                      onChange={(value) => edit({ ...input, channel: value === "expanded" ? "expanded" : "" }, ["channel"])}
+                      options={channelOptions}
+                      value={input.channel || "amazon"}
+                    />
+                  ) : null}
+                  {goalField}
+                </ToolFieldRow>
+              </>
+            ) : (
+              <ToolFieldRow>
+                <UiTextField
+                  dataFocusKey="fileSize"
+                  error={errors.fileSize}
+                  hint="Empty uses 2 MB until KDP shows your converted size."
+                  inputMode="decimal"
+                  label="Converted file size"
+                  onChange={(value) => edit({ ...input, fileSizeText: value }, ["fileSize"])}
+                  placeholder="2"
+                  suffix="MB"
+                  value={input.fileSizeText}
+                />
+                <UiChoiceGroup
+                  dataFocusKey="plan"
+                  error={errors.plan}
+                  hint="KDP pays 70% only on prices from $2.99 to $12.99."
+                  label="Royalty plan"
+                  onChange={(value) => edit({ ...input, plan: value === "35" ? "35" : "" }, ["plan"])}
+                  options={planOptions}
+                  value={input.plan || "70"}
+                />
+                {goalField}
+              </ToolFieldRow>
+            )}
           </div>
+        </UiDisclosure>
+
+        <UiActionRow>
+          {isStale ? <UiStatus>Inputs changed</UiStatus> : null}
+          <UiButton type="submit" variant="primary">Calculate royalty</UiButton>
+          <UiButton onPress={reset} type="button" variant="secondary">
+            <RotateCcw aria-hidden="true" size={17} />
+            Reset
+          </UiButton>
         </UiActionRow>
-        {status ? <UiStatus tone={result?.status === "invalid" ? "danger" : result?.issues.length ? "warning" : "neutral"}>{status}</UiStatus> : null}
-        {result?.status === "invalid" ? <ul className={styles.issueList}>{result.issues.map((issue) => <li data-severity={issue.severity} key={`${issue.code}-${issue.field}`}>{issue.message}</li>)}</ul> : null}
       </form>
 
-      {values ? (
-        <section aria-label="Royalty result" className={styles.result}>
-          <UiPrimaryResult detail={`${values.effectiveRoyaltyRate}% rate after print or delivery cost`} inputRef={resultRef} label="Royalty per sale" tone={values.royaltyCents > 0 ? "success" : "warning"} value={formatKdpMoney(values.royaltyCents)} />
-          <div className={styles.actions}><UiCopyAction label="Copy royalty" successLabel="Royalty copied" value={summary(values)} withManualFallback /></div>
-          <UiKeyValueList rows={[
-            { label: "Minimum list price", value: formatKdpMoney(values.minimumListPriceCents) },
-            ...(values.effectivePageCount === null ? [] : [{ label: "Effective pages", value: values.effectivePageCount }]),
-            { label: "Printing cost", value: values.printingCostCents === null ? "Not used" : formatKdpMoney(values.printingCostCents) },
-            ...(values.fixedCostCents === null ? [] : [{ label: "Fixed cost", value: formatKdpMoney(values.fixedCostCents) }, { label: "Page cost", value: formatKdpMoney(values.pageCostCents ?? 0) }]),
-            { label: "Delivery cost", value: values.deliveryCostCents === null ? "Not used" : formatKdpMoney(values.deliveryCostCents) },
-            { label: "Royalty margin", value: formatKdpPercent(values.royaltyMarginBasisPoints) },
-            { label: "Break-even ad spend", value: formatKdpMoney(values.breakEvenAdSpendCents) },
-            ...(values.breakEvenAcosBasisPoints === null ? [] : [{ label: "Break-even ACoS", value: formatKdpPercent(values.breakEvenAcosBasisPoints) }]),
-            ...(values.monthlyTargetStatus === "omitted" ? [] : [{ label: `${formatKdpMoney(values.monthlyTargetCents ?? 0)} monthly target`, value: values.monthlyTargetStatus === "unavailable" ? "Unknown — no positive royalty" : values.copiesForMonthlyTarget ?? 0 }]),
-          ]} />
-          {result?.issues.length ? <ul className={styles.issueList}>{result.issues.map((issue) => <li data-severity={issue.severity} key={`${issue.code}-${issue.field ?? "result"}`}>{issue.message}</li>)}</ul> : null}
-          <UiDataTable
-            ariaLabel="Price comparison"
-            columns={[{ id: "price", label: "List price" }, { id: "rate", label: "Rate" }, { id: "cost", label: "KDP cost" }, { id: "royalty", label: "Royalty" }, { id: "margin", label: "Margin" }]}
-            rows={values.pricePoints.map((point) => ({ id: String(point.listPriceCents), cells: { price: formatKdpMoney(point.listPriceCents), rate: `${point.royaltyRate}%`, cost: point.deductionCents ? formatKdpMoney(point.deductionCents) : "—", royalty: formatKdpMoney(point.royaltyCents), margin: formatKdpPercent(point.marginBasisPoints) } }))}
-          />
-          <UiDisclosure label="Calculation details">
-            <p className={styles.notice}>US Amazon.com · Standard distribution · USD.</p>
-            <p className={styles.notice}>{distributionNote}</p>
-            <p className={styles.notice}>Rules checked 2026-09-16. Sources: {values.sources.map((source, index) => <span key={source}>{index ? "; " : ""}<a href={source} rel="noreferrer">KDP help</a></span>)}.</p>
-          </UiDisclosure>
-        </section>
-      ) : null}
-    </section>
+      <ToolResult label="Royalty result" stale={isStale}>
+        <ResultView answerRef={answerRef} isExample={isExample} shown={shown} />
+      </ToolResult>
+    </ToolWorkbench>
+  );
+}
+
+function firstError(errors: Errors): KdpRoyaltyCalculatorField | null {
+  return focusOrder.find((field) => field in errors) ?? null;
+}
+
+/* ---------------- the result ---------------- */
+
+const limitCopy = {
+  "below-minimum": { label: "Lowest price KDP allows", status: "Below KDP minimum", mark: "KDP minimum" },
+  "below-break-even": { label: "Expanded Distribution break-even", status: "Below break-even", mark: "Break-even" },
+  "above-maximum": { label: "Highest price KDP allows", status: "Above KDP maximum", mark: "KDP maximum" },
+} as const;
+
+function statusWords(values: Values, isExample: boolean): ReactNode[] {
+  const words: string[] = [];
+  if (isExample) words.push("Example");
+  if (values.limit) words.push(limitCopy[values.limit.kind].status);
+  if (values.seventyOutsideBand) words.push("Paid at 35%");
+  if (values.deliveryExceedsShare) words.push("Delivery tops the 70% share");
+  return words.map((word) => <UiStatusWord key={word}>{word}</UiStatusWord>);
+}
+
+function costLabel(values: Values) {
+  if (values.costKind === "printing" && values.printing) {
+    const { enteredPages, printedPages } = values.printing;
+    return printedPages !== enteredPages ? `Printing, ${printedPages} pages` : "Printing";
+  }
+  if (!values.delivery) return "Delivery";
+  const label = `Delivery, ${megabytes(values.delivery.fileSizeMB)}`;
+  // The bar splits the price, so a fee larger than the price shows only the part it takes.
+  return values.delivery.costCents > values.split.costCents ? `${label}, part of a ${money(values.delivery.costCents)} fee` : label;
+}
+
+function rateHint(values: Values) {
+  if (values.rate === 40) return "Expanded Distribution pays 40% of the list price, minus printing.";
+  if (values.rate === 70) return "70% of the list price after the delivery cost.";
+  if (values.rate === 35) return "35% of the list price, with no delivery cost.";
+  return "KDP pays 50% below $9.99 and 60% from $9.99, minus printing.";
+}
+
+function comparisonMetric(values: Values): UiMetric | null {
+  const comparison = values.comparison;
+  if (!comparison) return null;
+  const value = money(comparison.royaltyCents);
+  if (comparison.kind === "rate-step") {
+    return { id: "comparison", label: `At ${money(comparison.priceCents)}`, hint: "KDP pays 60% from $9.99.", value };
+  }
+  if (comparison.kind === "other-channel") {
+    return { id: "comparison", label: "Amazon.com only", hint: "What an Amazon.com sale at the same price pays.", value };
+  }
+  if (comparison.kind === "other-plan") {
+    return { id: "comparison", label: `On the ${comparison.rate}% plan`, hint: "What the other plan pays at the same price.", value };
+  }
+  return { id: "comparison", label: `At ${money(comparison.priceCents)} on 70%`, hint: "The nearest price KDP pays 70% on.", value };
+}
+
+function metricsFor(values: Values): UiMetric[] {
+  const breakEven = values.minimumKind === "break-even";
+  // Below the minimum, the answer already is the minimum, so it isn't repeated here.
+  const answeredAtMinimum = values.limit !== null && values.limit.kind !== "above-maximum";
+  const minimumHint = breakEven
+    ? "Where 40% just covers printing; KDP's own minimum may be higher."
+    : values.format === "ebook"
+      ? "KDP sets it by file size; 70% starts at $2.99."
+      : "KDP sets it so your share covers printing.";
+  const comparison = comparisonMetric(values);
+  return [
+    { id: "rate", label: "Royalty rate", hint: rateHint(values), value: `${values.rate}%` },
+    ...(answeredAtMinimum ? [] : [{
+      id: "minimum",
+      label: breakEven ? "Break-even price" : "Lowest list price",
+      hint: minimumHint,
+      value: money(values.minimumPriceCents),
+    }]),
+    {
+      id: "share",
+      label: "Share of list price",
+      hint: "Also your break-even ACoS: ad spend above this share of sales loses money.",
+      value: percent(values.shareBasisPoints),
+    },
+    ...(comparison ? [comparison] : []),
+    ...(values.goal ? [{
+      id: "goal",
+      label: `Copies a month for ${goalMoney(values.goal.goalCents)}`,
+      value: values.goal.copies === null ? "—" : whole.format(values.goal.copies),
+    }] : []),
+  ];
+}
+
+function chartSpec(values: Values): UiChartSpec {
+  const markLabel = values.limit ? limitCopy[values.limit.kind].mark : "Your price";
+  return {
+    format: "currency",
+    height: 280,
+    kind: "line",
+    marks: [{ label: markLabel, x: values.curve.mark.priceCents / 100, y: values.curve.mark.royaltyCents / 100 }],
+    series: values.curve.series.map((series) => ({
+      id: series.id,
+      label: seriesLabels[series.id],
+      points: series.points.map(([price, royalty]) => [price / 100, royalty / 100] as const),
+    })),
+    title: "Royalty at each list price",
+    xFormat: "currency",
+  };
+}
+
+function setupLine(input: Input, values: Values) {
+  if (values.format === "ebook") {
+    const size = values.delivery ? megabytes(values.delivery.fileSizeMB) : "";
+    return `Kindle eBook, ${size}, ${values.plan}% plan`;
+  }
+  const trim = findKdpTrim(input.trimId || "6x9")?.label ?? "6 × 9 in";
+  const parts = [
+    values.format === "paperback" ? "Paperback" : "Hardcover",
+    trim,
+    interiorLabel(input.interior as KdpInterior).toLowerCase(),
+    `${paperLabel((input.paper || "white") as KdpPaper).toLowerCase()} paper`,
+    `${values.printing?.enteredPages ?? ""} pages`,
+  ];
+  if (values.channel === "expanded") parts.push("Expanded Distribution");
+  return parts.join(", ");
+}
+
+function summaryText(input: Input, values: Values) {
+  const lines = [
+    "KDP royalty estimate, Amazon.com, USD",
+    setupLine(input, values),
+    `List price: ${money(values.priceCents)}${values.limit ? ` (${limitCopy[values.limit.kind].label.toLowerCase()}; you entered ${money(values.enteredPriceCents)})` : ""}`,
+    `Royalty: ${money(values.royaltyCents)} per copy at ${values.rate}%`,
+  ];
+  if (values.printing) {
+    const { costCents, fixedCents, pageCents, printedPages } = values.printing;
+    lines.push(`Printing: ${money(costCents)} (${money(fixedCents)} fixed + ${money(pageCents)} for ${printedPages} pages)`);
+  }
+  if (values.costKind === "delivery" && values.delivery) lines.push(`Delivery: ${money(values.delivery.costCents)}`);
+  lines.push(`${values.minimumKind === "break-even" ? "Break-even price" : "Lowest list price"}: ${money(values.minimumPriceCents)}`);
+  lines.push(`Share of list price: ${percent(values.shareBasisPoints)}`);
+  const comparison = comparisonMetric(values);
+  if (comparison) lines.push(`${comparison.label}: ${comparison.value}`);
+  if (values.goal) lines.push(`Copies a month for ${goalMoney(values.goal.goalCents)}: ${values.goal.copies === null ? "none, no royalty" : whole.format(values.goal.copies)}`);
+  lines.push(`KDP rules as of ${values.rulesVersion}`);
+  return lines.join("\n");
+}
+
+function ResultView({ answerRef, isExample, shown }: { answerRef: RefObject<HTMLOutputElement | null>; isExample: boolean; shown: Shown }) {
+  const { input, values } = shown;
+  const limit = values.limit;
+  const words = statusWords(values, isExample);
+  const detail = limit ? `earns ${money(values.royaltyCents)} a copy` : `on a ${money(values.priceCents)} ${formatWord(values.format)}`;
+  const segments: UiAllocationSegment[] = [
+    { id: "royalty", label: "Your royalty", tone: "chartreuse", value: values.split.royaltyCents },
+    ...(values.costKind ? [{ id: "cost", label: costLabel(values), tone: "medium" as const, value: values.split.costCents }] : []),
+    { id: "amazon", label: "Amazon", tone: "light", value: values.split.amazonCents },
+  ];
+
+  return (
+    <>
+      <div className={styles.top}>
+        <UiPrimaryResult
+          detail={(
+            <span className={styles.detail}>
+              {detail}
+              {words.length ? <span className={styles.status}>{words}</span> : null}
+            </span>
+          )}
+          inputRef={answerRef}
+          label={limit ? limitCopy[limit.kind].label : "Royalty per copy"}
+          value={money(limit ? limit.priceCents : values.royaltyCents)}
+        />
+        <UiAllocationBar
+          ariaLabel={`How the ${money(values.priceCents)} list price splits`}
+          formatValue={(value) => money(Number(value))}
+          segments={segments}
+        />
+      </div>
+      <UiMetricGroup ariaLabel="Supporting numbers" items={metricsFor(values)} />
+      <UiLiveChart spec={chartSpec(values)} />
+      <div className={styles.actions}>
+        <UiCopyAction label="Copy summary" successLabel="Summary copied" value={summaryText(input, values)} withManualFallback />
+        <UiShareAction params={shareParams(input)} />
+      </div>
+    </>
   );
 }
diff --git a/app/(site)/(tools)/kdp-royalty-calculator/page.tsx b/app/(site)/(tools)/kdp-royalty-calculator/page.tsx
index 26991044..6d3f8afc 100644
--- a/app/(site)/(tools)/kdp-royalty-calculator/page.tsx
+++ b/app/(site)/(tools)/kdp-royalty-calculator/page.tsx
@@ -1,9 +1,9 @@
-import { ToolPageShell } from "@/app/ui/tools/tool-page-shell";
 import { CircleDollarSign } from "lucide-react";
+import { ToolPageShell } from "@/app/ui/tools/tool-page-shell";
 import { ToolPageArticle, ToolPageHeader } from "@/app/ui/site/tool-page-content";
+import { PageCanvas } from "@/app/ui/site/page-canvas";
 import { getRequiredToolPage } from "@/lib/tool-pages";
-import { PageCanvas } from "../../../ui/site/page-canvas";
-import { KdpRoyaltyCalculator } from "./kdp-royalty-calculator";
+import { KdpRoyaltyCalculatorFromUrl } from "./kdp-royalty-calculator-from-url";
 import Article from "./content/article.mdx";
 import Intro from "./content/intro.mdx";
 import Usage from "./content/usage.mdx";
@@ -14,7 +14,7 @@ export default async function KdpRoyaltyCalculatorPage() {
     <ToolPageShell toolPage={toolPage}>
       <PageCanvas>
         <ToolPageHeader icon={<CircleDollarSign strokeWidth={2.2} />} intro={<Intro />} toolPage={toolPage} />
-        <KdpRoyaltyCalculator />
+        <KdpRoyaltyCalculatorFromUrl />
         <ToolPageArticle>
           <Usage />
           <Article />
diff --git a/app/ui/charts/chart-client.tsx b/app/ui/charts/chart-client.tsx
index 5b313882..6390d17f 100644
--- a/app/ui/charts/chart-client.tsx
+++ b/app/ui/charts/chart-client.tsx
@@ -5,11 +5,25 @@ import type { EChartsType } from "echarts/core";
 import type { DateValue } from "react-aria-components";
 import { useEffect, useMemo, useRef, useState } from "react";
 import { UiDatePicker } from "@/app/ui/controls";
-import { chartLegend, chartOption, donutTotal, hasChartTable, rangedSeries, rangeStart, xBounds, type UiChartRange, type UiChartSpec } from "./chart-option";
+import { chartLegend, chartOption, donutTotal, hasChartTable, needsMoreCharts, rangedSeries, rangeStart, xBounds, type UiChartRange, type UiChartSpec } from "./chart-option";
 import { ChartDataTable, ChartHeading } from "./chart-parts";
 import { echarts } from "./echarts";
 import styles from "./charts.module.css";
 
+// Funnel, gauge, treemap, sankey, and radar load once, on the first chart that needs one.
+let moreCharts: Promise<void> | null = null;
+let moreChartsReady = false;
+const loadMoreCharts = () => (moreCharts ??= import("./echarts-more").then(
+  () => {
+    moreChartsReady = true;
+  },
+  (error: unknown) => {
+    // A failed download can be tried again by the next chart.
+    moreCharts = null;
+    throw error;
+  },
+));
+
 const ranges: { id: UiChartRange; label: string; name: string }[] = [
   { id: "1m", label: "1M", name: "Last month" },
   { id: "3m", label: "3M", name: "Last 3 months" },
@@ -56,6 +70,10 @@ function keepSpan(bounds: Bounds | null, preset: UiChartRange | null, span: Span
 export function UiLiveChart({ spec, svg }: { spec: UiChartSpec; svg?: string }) {
   const hostRef = useRef<HTMLDivElement>(null);
   const chartRef = useRef<EChartsType | null>(null);
+  // ECharts copies its layout steps when an instance starts, so a chart started before the extra
+  // types loaded is started again to draw them.
+  const startRef = useRef<(() => void) | null>(null);
+  const startedWithMore = useRef(false);
   const [drawnIn, setDrawnIn] = useState<number | null>(null);
   const [hidden, setHidden] = useState<string[]>([]);
   const legend = chartLegend(spec);
@@ -90,40 +108,59 @@ export function UiLiveChart({ spec, svg }: { spec: UiChartSpec; svg?: string })
   useEffect(() => {
     const host = hostRef.current;
     if (!host) return;
-    const chart = echarts.init(host, null, { renderer: "svg" });
-    chartRef.current = chart;
-    const resize = new ResizeObserver(() => chart.resize());
+    const start = () => {
+      chartRef.current?.dispose();
+      const chart = echarts.init(host, null, { renderer: "svg" });
+      chartRef.current = chart;
+      startedWithMore.current = moreChartsReady;
+      chart.on("datazoom", (event) => {
+        const current = latestState.current.bounds;
+        if (!current) return;
+        const zoom = (event as ZoomEvent).batch?.[0] ?? (event as ZoomEvent);
+        if (zoom.start === undefined || zoom.end === undefined) return;
+        const span = current.last - current.first;
+        setVisible({ end: current.first + span * zoom.end / 100, start: current.first + span * zoom.start / 100 });
+        setDraft({});
+        setPreset(null);
+      });
+    };
+    start();
+    startRef.current = start;
+    const resize = new ResizeObserver(() => chartRef.current?.resize());
     resize.observe(host);
-    chart.on("datazoom", (event) => {
-      const current = latestState.current.bounds;
-      if (!current) return;
-      const zoom = (event as ZoomEvent).batch?.[0] ?? (event as ZoomEvent);
-      if (zoom.start === undefined || zoom.end === undefined) return;
-      const span = current.last - current.first;
-      setVisible({ end: current.first + span * zoom.end / 100, start: current.first + span * zoom.start / 100 });
-      setDraft({});
-      setPreset(null);
-    });
     return () => {
       resize.disconnect();
-      chart.dispose();
+      chartRef.current?.dispose();
       chartRef.current = null;
+      startRef.current = null;
     };
   }, []);
 
   useEffect(() => {
-    const chart = chartRef.current;
-    if (!chart) return;
+    let cancelled = false;
+    let frame = 0;
     const started = performance.now();
-    const option = chartOption(spec);
-    // A redraw keeps the lines the reader turned off and the range they picked.
-    const { hidden: off, visible: span } = latestState.current;
-    option.legend = { selected: Object.fromEntries(off.map((label) => [label, false])), show: false };
-    if (span && Array.isArray(option.dataZoom)) option.dataZoom = option.dataZoom.map((zoom) => ({ ...zoom, endValue: span.end, startValue: span.start }));
-    chart.setOption(option, { notMerge: true });
-    // Reported once the browser has painted the chart; the gallery's page weight panel reads it.
-    const frame = requestAnimationFrame(() => setDrawnIn((time) => time ?? performance.now() - started));
-    return () => cancelAnimationFrame(frame);
+    const draw = () => {
+      if (cancelled) return;
+      if (needsMoreCharts(spec) && !startedWithMore.current) startRef.current?.();
+      const chart = chartRef.current;
+      if (!chart || chart.isDisposed()) return;
+      const option = chartOption(spec);
+      // A redraw keeps the lines the reader turned off and the range they picked.
+      const { hidden: off, visible: span } = latestState.current;
+      option.legend = { selected: Object.fromEntries(off.map((label) => [label, false])), show: false };
+      if (span && Array.isArray(option.dataZoom)) option.dataZoom = option.dataZoom.map((zoom) => ({ ...zoom, endValue: span.end, startValue: span.start }));
+      chart.setOption(option, { notMerge: true });
+      // Reported once the browser has painted the chart; the gallery's page weight panel reads it.
+      frame = requestAnimationFrame(() => setDrawnIn((time) => time ?? performance.now() - started));
+    };
+    // Until the extra types arrive, the server drawing, if any, stays in place.
+    if (needsMoreCharts(spec)) loadMoreCharts().then(draw, () => {});
+    else draw();
+    return () => {
+      cancelled = true;
+      cancelAnimationFrame(frame);
+    };
   }, [spec]);
 
   const zoomTo = (start: number, end: number) => {
diff --git a/app/ui/charts/chart-option.ts b/app/ui/charts/chart-option.ts
index 9da8cf92..bfc9c58a 100644
--- a/app/ui/charts/chart-option.ts
+++ b/app/ui/charts/chart-option.ts
@@ -51,6 +51,8 @@ export type UiChartSpec = Shared & (
       xFormat?: UiChartFormat;
       /** Time charts: show range buttons and a range slider, starting at this range. */
       range?: UiChartRange;
+      /** Labeled dots at numeric x values, such as the person's own value on a curve. */
+      marks?: readonly UiChartMark[];
     }
   | { kind: "bar" | "stacked-bar" | "horizontal-bar"; categories: readonly string[]; series: readonly { id: string; label: string; values: readonly number[] }[] }
   | { kind: "donut"; slices: readonly { id: string; label: string; value: number }[] }
@@ -63,8 +65,73 @@ export type UiChartSpec = Shared & (
       /** What a cell counts, for the tooltip. */
       valueLabel: string;
     }
+  /** Stages that narrow, such as trials to paid. Stages keep their order. */
+  | { kind: "funnel"; stages: readonly UiChartPart[] }
+  /** One value against a scale, such as progress toward a goal. */
+  | { kind: "gauge"; label: string; max: number; min?: number; value: number }
+  /** Parts of a total as nested-feeling blocks, for many parts or long tails. */
+  | { kind: "treemap"; parts: readonly UiChartPart[] }
+  /** How amounts flow from one group to the next, such as MRR movements. */
+  | { kind: "sankey"; nodes: readonly { id: string; label: string }[]; links: readonly { source: string; target: string; value: number }[] }
+  /** Several measures compared as shapes, such as two plans across five qualities. */
+  | { kind: "radar"; axes: readonly { label: string; max: number }[]; series: readonly { id: string; label: string; values: readonly number[] }[] }
 );
 
+export type UiChartPart = { id: string; label: string; value: number };
+
+/** One labeled dot on a line chart, such as `Your price`. */
+export type UiChartMark = { label: string; x: number; y: number };
+
+/** Kinds drawn by chart types that load only on pages that use them. See echarts-more.ts. */
+const moreKinds: ReadonlySet<UiChartSpec["kind"]> = new Set(["funnel", "gauge", "treemap", "sankey", "radar"]);
+
+export const needsMoreCharts = (spec: UiChartSpec) => moreKinds.has(spec.kind);
+
+// The drawing, tooltip, and screen-reader table all read data through these, so they always agree.
+
+/** Funnel stages with a finite value. */
+const funnelStages = (spec: Extract<UiChartSpec, { kind: "funnel" }>) => spec.stages.filter((stage) => Number.isFinite(stage.value));
+
+/** Treemap parts with a finite positive value. */
+const treemapParts = (spec: Extract<UiChartSpec, { kind: "treemap" }>) => spec.parts.filter((part) => Number.isFinite(part.value) && part.value > 0);
+
+/** A radar value on its axis, or null for a gap. */
+const radarValue = (values: readonly number[], index: number) => (Number.isFinite(values[index]) ? values[index] : null);
+
+type SankeySpec = Extract<UiChartSpec, { kind: "sankey" }>;
+
+/**
+ * Links ECharts can lay out: both ends known, a finite positive value, and no loop back. A flow
+ * must only move forward, so a link that would close a cycle is left out instead of crashing the drawing.
+ */
+const sankeyLinks = (spec: SankeySpec) => {
+  const ids = new Set(spec.nodes.map((node) => node.id));
+  const next = new Map<string, string[]>();
+  const reaches = (from: string, to: string) => {
+    const seen = new Set<string>();
+    const stack = [from];
+    while (stack.length) {
+      const id = stack.pop()!;
+      if (id === to) return true;
+      if (seen.has(id)) continue;
+      seen.add(id);
+      stack.push(...(next.get(id) ?? []));
+    }
+    return false;
+  };
+  return spec.links.filter((link) => {
+    if (!ids.has(link.source) || !ids.has(link.target) || !Number.isFinite(link.value) || link.value <= 0) return false;
+    if (reaches(link.target, link.source)) return false;
+    next.set(link.source, [...(next.get(link.source) ?? []), link.target]);
+    return true;
+  });
+};
+
+const hasGaugeScale = (spec: Extract<UiChartSpec, { kind: "gauge" }>) =>
+  Number.isFinite(spec.min ?? 0) && Number.isFinite(spec.max) && spec.max > (spec.min ?? 0) && Number.isFinite(spec.value);
+
+const share = (value: number, total: number) => `${numberFormat.format(total ? value / total * 100 : 0)}%`;
+
 /** Names shown in the legend, in series order. Donut slices also show their value and share. */
 export function chartLegend(spec: UiChartSpec): { label: string; detail?: string }[] {
   if (spec.kind === "donut") {
@@ -74,7 +141,8 @@ export function chartLegend(spec: UiChartSpec): { label: string; detail?: string
       label: slice.label,
     }));
   }
-  if (spec.kind === "heatmap") return [];
+  // These label their parts on the drawing itself, so a toggle legend would only repeat them.
+  if (spec.kind === "heatmap" || spec.kind === "funnel" || spec.kind === "gauge" || spec.kind === "treemap" || spec.kind === "sankey") return [];
   return spec.series.map((series) => ({ label: series.label }));
 }
 
@@ -86,6 +154,18 @@ type LineSpec = Extract<UiChartSpec, { kind: "line" | "area" | "stacked-area" }>
 
 const isLine = (spec: UiChartSpec): spec is LineSpec => spec.kind === "line" || spec.kind === "area" || spec.kind === "stacked-area";
 
+/** Marks with finite values. A labeled x axis places by position, so it takes none. */
+function lineMarks(spec: UiChartSpec) {
+  if (!isLine(spec) || !spec.marks || xLabels(spec)) return [];
+  return spec.marks.filter((mark) => Number.isFinite(mark.x) && Number.isFinite(mark.y));
+}
+
+/** How a mark reads out loud, such as `Your price, $14.99: $4.39`. */
+const markText = (spec: LineSpec, mark: UiChartMark) => `${mark.label}, ${formatChartValue(mark.x, spec.xFormat ?? "number")}: ${formatChartValue(mark.y, spec.format)}`;
+
+/** Every mark read out loud, for charts too large for a hidden table. */
+export const chartMarksText = (spec: UiChartSpec) => (isLine(spec) ? lineMarks(spec).map((mark) => markText(spec, mark)) : []);
+
 /**
  * The labels of a labeled x axis, or null when x values are numbers. Labels are positions: every
  * series lists its points in the same order, and a label may repeat, so the longest series names them.
@@ -111,6 +191,11 @@ const tableLimit = 60;
 function valueCount(spec: UiChartSpec) {
   if (spec.kind === "donut") return spec.slices.length;
   if (spec.kind === "heatmap") return spec.cells.length;
+  if (spec.kind === "funnel") return funnelStages(spec).length;
+  if (spec.kind === "gauge") return 1;
+  if (spec.kind === "treemap") return treemapParts(spec).length;
+  if (spec.kind === "sankey") return sankeyLinks(spec).length;
+  if (spec.kind === "radar") return spec.axes.length * spec.series.length;
   if (spec.kind === "bar" || spec.kind === "stacked-bar" || spec.kind === "horizontal-bar") return spec.categories.length * spec.series.length;
   const points = (spec.series as readonly UiChartSeries<unknown>[]).reduce((count, line) => count + line.points.length, 0);
   return spec.kind === "scatter" ? points * 2 : points;
@@ -137,6 +222,41 @@ export function chartTable(spec: UiChartSpec): { columns: string[]; corner: stri
       ],
     };
   }
+  if (spec.kind === "funnel") {
+    const stages = funnelStages(spec);
+    const first = stages[0]?.value ?? 0;
+    return {
+      columns: ["Value", "Share of first stage"],
+      corner: "Stage",
+      rows: stages.map((stage) => ({ cells: [format(stage.value), share(stage.value, first)], label: stage.label })),
+    };
+  }
+  if (spec.kind === "gauge") {
+    const cells = hasGaugeScale(spec) ? [format(spec.value), `${format(spec.min ?? 0)} to ${format(spec.max)}`] : ["No value", ""];
+    return { columns: ["Value", "Scale"], corner: "Measure", rows: [{ cells, label: spec.label }] };
+  }
+  if (spec.kind === "treemap") {
+    const parts = treemapParts(spec);
+    const total = parts.reduce((sum, part) => sum + part.value, 0);
+    return { columns: ["Value", "Share"], corner: "Part", rows: parts.map((part) => ({ cells: [format(part.value), share(part.value, total)], label: part.label })) };
+  }
+  if (spec.kind === "sankey") {
+    const names = new Map(spec.nodes.map((node) => [node.id, node.label]));
+    return { columns: ["To", "Value"], corner: "From", rows: sankeyLinks(spec).map((link) => ({ cells: [names.get(link.target) ?? link.target, format(link.value)], label: names.get(link.source) ?? link.source })) };
+  }
+  if (spec.kind === "radar") {
+    return {
+      columns: spec.series.map((shape) => shape.label),
+      corner: "Measure",
+      rows: spec.axes.map((axis, index) => ({
+        cells: spec.series.map((shape) => {
+          const value = radarValue(shape.values, index);
+          return value === null ? "No value" : format(value);
+        }),
+        label: axis.label,
+      })),
+    };
+  }
   if (spec.kind === "heatmap") {
     const cells = new Map(spec.cells.map(([x, y, value]) => [`${x},${y}`, value]));
     return {
@@ -172,16 +292,29 @@ export function chartTable(spec: UiChartSpec): { columns: string[]; corner: stri
   // One row per x value, so lines that share a date share a row.
   const xs = [...new Set(series.flatMap((line) => line.points.map((point) => point[0])))];
   xs.sort((a, b) => Number(a) - Number(b));
+  // A mark belongs to no one line, so its value gets its own column.
+  const marks = lineMarks(spec);
+  const markColumn = marks.length ? [""] : [];
   return {
-    columns: series.map((line) => line.label),
+    columns: [...series.map((line) => line.label), ...(marks.length ? ["Marked value"] : [])],
     corner: isTimeFormat(spec.xFormat) ? "Date" : "Point",
-    rows: xs.map((x) => ({
-      cells: series.map((line) => {
-        const point = line.points.find((item) => item[0] === x);
-        return point ? format(point[1]) : "";
-      }),
-      label: typeof x === "string" ? x : formatChartValue(x, spec.xFormat ?? "number"),
-    })),
+    rows: [
+      ...xs.map((x) => ({
+        cells: [
+          ...series.map((line) => {
+            const point = line.points.find((item) => item[0] === x);
+            return point ? format(point[1]) : "";
+          }),
+          ...markColumn,
+        ],
+        label: typeof x === "string" ? x : formatChartValue(x, spec.xFormat ?? "number"),
+      })),
+      // Each mark gets its own row, read with its label, after the line's points.
+      ...marks.map((mark) => ({
+        cells: [...series.map(() => ""), format(mark.y)],
+        label: `${mark.label}, ${formatChartValue(mark.x, spec.xFormat ?? "number")}`,
+      })),
+    ],
   };
 }
 
@@ -252,6 +385,8 @@ const axisLabel = { color: ink.muted, fontSize: 12, hideOverlap: true, padding:
 // Every label says where it is: a zoomed-in axis shows "May 25", not a bare "25".
 const timeLabels = { day: "{MMM} {d}", hour: "{HH}:{mm}", millisecond: "{HH}:{mm}", minute: "{HH}:{mm}", month: "{MMM}", second: "{HH}:{mm}:{ss}", year: "{yyyy}" };
 const splitLine = { lineStyle: { color: ink.grid } };
+// Text drawn over colored shapes: the page color outlines it, so it reads on any data color in both themes.
+const onShape = { color: ink.text, textBorderColor: ink.page, textBorderWidth: 3 };
 const axisLine = { lineStyle: { color: ink.axis } };
 
 /** Turns data into a complete ECharts option in the site style. The server and the browser call it with the same data. */
@@ -260,7 +395,7 @@ export function chartOption(spec: UiChartSpec): EChartsCoreOption {
   const base = {
     animation: false,
     // Small charts carry a data table instead; see chartTable.
-    aria: { enabled: !hasChartTable(spec), label: { description: spec.caption ? `${spec.title}. ${spec.caption}` : spec.title } },
+    aria: { enabled: !hasChartTable(spec), label: { description: [spec.title, spec.caption, ...chartMarksText(spec)].filter(Boolean).join(". ") } },
     color: [...seriesInk],
     legend: { show: false },
     textStyle: { color: ink.text, fontFamily: "var(--font-mono)", fontSize: 12 },
@@ -283,6 +418,7 @@ export function chartOption(spec: UiChartSpec): EChartsCoreOption {
     const ranged = rangedSeries(spec);
     const { first, last } = ranged ? xBounds(ranged) : { first: 0, last: 0 };
     const withRange = ranged !== null;
+    const marks = lineMarks(spec);
     return {
       ...base,
       dataZoom: withRange
@@ -307,28 +443,44 @@ export function chartOption(spec: UiChartSpec): EChartsCoreOption {
           ]
         : undefined,
       grid: { bottom: withRange ? 52 : 16, left: 12, right: 16, top: 16 },
-      series: spec.series.map((line, index) => ({
-        areaStyle: spec.kind === "line" ? undefined : { color: seriesColor(index), opacity: spec.kind === "stacked-area" ? 0.32 : 0.14 },
-        color: seriesColor(index),
-        // A labeled axis places values by position, so a repeated label keeps its own point.
-        data: labels ? line.points.map((point) => point[1]) : line.points,
-        emphasis: { disabled: true },
-        id: line.id,
-        itemStyle: { borderColor: ink.page, borderWidth: 2, color: seriesColor(index) },
-        lineStyle: { color: seriesColor(index), width: 2 },
-        name: line.label,
-        sampling: "lttb",
-        showSymbol: false,
-        stack: spec.kind === "stacked-area" ? "total" : undefined,
-        symbol: "circle",
-        symbolSize: 8,
-        type: "line",
-      })),
+      series: [
+        ...spec.series.map((line, index) => ({
+          areaStyle: spec.kind === "line" ? undefined : { color: seriesColor(index), opacity: spec.kind === "stacked-area" ? 0.32 : 0.14 },
+          color: seriesColor(index),
+          // A labeled axis places values by position, so a repeated label keeps its own point.
+          data: labels ? line.points.map((point) => point[1]) : line.points,
+          emphasis: { disabled: true },
+          id: line.id,
+          itemStyle: { borderColor: ink.page, borderWidth: 2, color: seriesColor(index) },
+          lineStyle: { color: seriesColor(index), width: 2 },
+          name: line.label,
+          sampling: "lttb",
+          showSymbol: false,
+          stack: spec.kind === "stacked-area" ? "total" : undefined,
+          symbol: "circle",
+          symbolSize: 8,
+          type: "line",
+        })),
+        // Marks sit on top of the lines as outlined dots, each named by its label.
+        ...(marks.length ? [{
+          data: marks.map((mark) => ({ name: mark.label, value: [mark.x, mark.y] })),
+          emphasis: { disabled: true },
+          id: "marks",
+          itemStyle: { borderColor: ink.page, borderWidth: 2, color: ink.text },
+          label: { ...onShape, formatter: "{b}", position: "top", show: true },
+          name: "Marks",
+          symbolSize: 11,
+          type: "scatter",
+          z: 3,
+        }] : []),
+      ],
       tooltip: {
         ...base.tooltip,
         axisPointer: { lineStyle: { color: ink.axis, width: 1 }, type: "line" },
         formatter: (params: unknown) => {
-          const list = asParams(params);
+          // The marks repeat a line's own value, so the tooltip lists the lines only.
+          const list = asParams(params).filter((item) => item.seriesIndex < spec.series.length);
+          if (!list.length) return "";
           const x = list[0]?.axisValue ?? (list[0]?.value as number[])[0];
           // A labeled axis holds plain values; numeric and time axes hold [x, y] pairs.
           const y = (item: TooltipParam) => (labels ? Number(item.value) : (item.value as number[])[1]);
@@ -444,6 +596,185 @@ export function chartOption(spec: UiChartSpec): EChartsCoreOption {
     };
   }
 
+  if (spec.kind === "funnel") {
+    const stages = funnelStages(spec);
+    const first = stages[0]?.value ?? 0;
+    const max = Math.max(0, ...stages.map((stage) => stage.value));
+    return {
+      ...base,
+      series: [{
+        bottom: 8,
+        data: stages.map((stage, index) => ({ itemStyle: { color: seriesColor(index) }, name: stage.label, value: stage.value })),
+        emphasis: { disabled: true },
+        gap: 3,
+        itemStyle: { borderWidth: 0 },
+        // Labels sit beside the funnel in plain text, so they read in both themes without an outline.
+        // The value goes under the name, and long names wrap, so labels fit beside the funnel on phones.
+        label: { color: ink.text, formatter: (item: { name: string; value: number }) => `${item.name}\n${format(item.value)}`, lineHeight: 18, overflow: "break", position: "right", width: 128 },
+        labelLine: { length: 12, lineStyle: { color: ink.axis } },
+        left: 8,
+        max,
+        min: 0,
+        minSize: "8%",
+        name: spec.title,
+        sort: "none",
+        width: "50%",
+        top: 8,
+        type: "funnel",
+      }],
+      tooltip: {
+        ...base.tooltip,
+        formatter: (params: unknown) => {
+          const [item] = asParams(params);
+          const previous = stages[item.dataIndex - 1]?.value;
+          const rows = [{ color: item.dataIndex, label: "Value", value: format(item.value as number) }, { color: item.dataIndex, label: "Of first stage", value: share(item.value as number, first) }];
+          if (previous !== undefined) rows.push({ color: item.dataIndex, label: "Of previous stage", value: share(item.value as number, previous) });
+          return tooltipHtml(item.name, rows);
+        },
+        trigger: "item",
+      },
+    };
+  }
+
+  if (spec.kind === "gauge") {
+    // A broken scale draws nothing rather than progress that means nothing.
+    if (!hasGaugeScale(spec)) return base;
+    const min = spec.min ?? 0;
+    return {
+      ...base,
+      series: [{
+        axisLabel: { show: false },
+        axisLine: { lineStyle: { color: [[1, ink.grid]], width: 16 } },
+        axisTick: { show: false },
+        center: ["50%", "62%"],
+        data: [{ name: spec.label, value: Math.min(spec.max, Math.max(min, spec.value)) }],
+        detail: { color: ink.text, fontFamily: "var(--font-mono)", fontSize: 28, fontWeight: 600, formatter: () => format(spec.value), offsetCenter: [0, "-8%"] },
+        emphasis: { disabled: true },
+        endAngle: -20,
+        max: spec.max,
+        min,
+        name: spec.title,
+        pointer: { show: false },
+        progress: { itemStyle: { color: seriesColor(0) }, show: true, width: 16 },
+        radius: "92%",
+        splitLine: { show: false },
+        startAngle: 200,
+        title: { color: ink.muted, fontSize: 12, offsetCenter: [0, "22%"] },
+        type: "gauge",
+      }],
+      tooltip: { show: false },
+    };
+  }
+
+  if (spec.kind === "treemap") {
+    const parts = treemapParts(spec);
+    const total = parts.reduce((sum, part) => sum + part.value, 0);
+    return {
+      ...base,
+      series: [{
+        breadcrumb: { show: false },
+        // ECharts puts a root node first, so each part carries its own color index for the tooltip.
+        data: parts.map((part, index) => ({ colorIndex: index, itemStyle: { color: seriesColor(index) }, name: part.label, value: part.value })),
+        emphasis: { disabled: true },
+        height: "100%",
+        itemStyle: { borderColor: ink.page, borderWidth: 2, gapWidth: 2 },
+        label: { ...onShape, formatter: (item: { name: string; value: number }) => `${item.name}\n${format(item.value)}`, position: "insideTopLeft" },
+        left: 0,
+        name: spec.title,
+        nodeClick: false,
+        roam: false,
+        top: 0,
+        type: "treemap",
+        width: "100%",
+      }],
+      tooltip: {
+        ...base.tooltip,
+        formatter: (params: unknown) => {
+          const [item] = asParams(params);
+          const colorIndex = (item.data as { colorIndex?: number } | undefined)?.colorIndex ?? 0;
+          return tooltipHtml(spec.title, [{ color: colorIndex, label: item.name, value: `${format(item.value as number)} (${share(item.value as number, total)})` }]);
+        },
+        trigger: "item",
+      },
+    };
+  }
+
+  if (spec.kind === "sankey") {
+    // Nodes are keyed by id, so two nodes may share a label.
+    const names = new Map(spec.nodes.map((node) => [node.id, node.label]));
+    const nameOf = (id: string) => names.get(id) ?? id;
+    return {
+      ...base,
+      series: [{
+        bottom: 8,
+        data: spec.nodes.map((node, index) => ({ itemStyle: { color: seriesColor(index) }, name: node.id })),
+        draggable: false,
+        emphasis: { disabled: true },
+        label: { color: ink.text, formatter: (item: { name: string }) => nameOf(item.name) },
+        left: 8,
+        lineStyle: { color: "source", opacity: 0.32 },
+        links: sankeyLinks(spec).map((link) => ({ source: link.source, target: link.target, value: link.value })),
+        nodeGap: 12,
+        nodeWidth: 12,
+        right: 96,
+        top: 8,
+        type: "sankey",
+      }],
+      tooltip: {
+        ...base.tooltip,
+        formatter: (params: unknown) => {
+          const item = asParams(params)[0] as TooltipParam & { dataType?: string; data: { source?: string; target?: string; value?: number } };
+          if (item.dataType === "edge") return tooltipHtml(`${nameOf(item.data.source ?? "")} to ${nameOf(item.data.target ?? "")}`, [{ color: 0, label: "Value", value: format(item.data.value ?? 0) }]);
+          return tooltipHtml(nameOf(item.name), [{ color: item.dataIndex, label: "Value", value: format(item.value as number) }]);
+        },
+        trigger: "item",
+      },
+    };
+  }
+
+  if (spec.kind === "radar") {
+    if (!spec.axes.length) return base;
+    return {
+      ...base,
+      radar: {
+        axisLine: axisLine,
+        axisName: { color: ink.muted, fontSize: 12 },
+        indicator: spec.axes.map((axis) => ({ max: axis.max, name: axis.label })),
+        axisNameGap: 8,
+        // Leaves room for axis names beside the shape on a phone-width chart.
+        radius: "52%",
+        splitArea: { show: false },
+        splitLine,
+      },
+      series: [{
+        data: spec.series.map((shape, index) => ({
+          areaStyle: { color: seriesColor(index), opacity: 0.14 },
+          itemStyle: { color: seriesColor(index) },
+          lineStyle: { color: seriesColor(index), width: 2 },
+          name: shape.label,
+          // One value per axis. A missing or broken value draws as a gap, not as zero.
+          value: spec.axes.map((_, axis) => radarValue(shape.values, axis) ?? "-"),
+        })),
+        emphasis: { disabled: true },
+        symbol: "circle",
+        symbolSize: 6,
+        type: "radar",
+      }],
+      tooltip: {
+        ...base.tooltip,
+        formatter: (params: unknown) => {
+          const [item] = asParams(params);
+          const values = spec.series[item.dataIndex]?.values ?? [];
+          return tooltipHtml(item.name, spec.axes.map((axis, index) => {
+            const value = radarValue(values, index);
+            return { color: item.dataIndex, label: axis.label, value: value === null ? "No value" : format(value) };
+          }));
+        },
+        trigger: "item",
+      },
+    };
+  }
+
   if (spec.kind !== "heatmap") return base;
   const values = spec.cells.map((cell) => cell[2]);
   return {
diff --git a/app/ui/charts/chart-static.tsx b/app/ui/charts/chart-static.tsx
index d5bbe3f2..82be3fee 100644
--- a/app/ui/charts/chart-static.tsx
+++ b/app/ui/charts/chart-static.tsx
@@ -1,6 +1,8 @@
-import { chartLegend, chartOption, donutTotal, hasChartTable, type UiChartSpec } from "./chart-option";
+import { chartLegend, chartMarksText, chartOption, donutTotal, hasChartTable, type UiChartSpec } from "./chart-option";
 import { ChartDataTable, ChartHeading } from "./chart-parts";
 import { echarts } from "./echarts";
+// The server draws every chart type. The browser loads these only when a chart needs one.
+import "./echarts-more";
 import styles from "./charts.module.css";
 
 /** Server drawing widths: the wide content column, the reading column, and a phone. */
@@ -26,7 +28,7 @@ export function UiStaticChart({ spec }: { spec: UiChartSpec }) {
   const total = donutTotal(spec);
   const withTable = hasChartTable(spec);
   // Small charts are read from their hidden table. Larger ones get a short description instead.
-  const description = [spec.title, spec.caption, legend.length ? `Shows ${legend.map((item) => item.label).join(", ")}.` : null].filter(Boolean).join(". ");
+  const description = [spec.title, spec.caption, legend.length ? `Shows ${legend.map((item) => item.label).join(", ")}.` : null, ...chartMarksText(spec)].filter(Boolean).join(". ");
   return (
     <figure className={`${styles.figure} ${styles.static}`}>
       <ChartHeading spec={spec} />
diff --git a/app/ui/charts/echarts-more.ts b/app/ui/charts/echarts-more.ts
new file mode 100644
index 00000000..96b8cdee
--- /dev/null
+++ b/app/ui/charts/echarts-more.ts
@@ -0,0 +1,10 @@
+import { FunnelChart, GaugeChart, RadarChart, SankeyChart, TreemapChart } from "echarts/charts";
+import { RadarComponent } from "echarts/components";
+import { echarts } from "./echarts";
+
+/**
+ * Chart types beyond the common set. The server always registers them. The browser loads this
+ * file only for a chart that needs one, so pages with ordinary charts don't carry their weight.
+ * Add a new ECharts type here, or in echarts.ts when most chart pages will use it.
+ */
+echarts.use([FunnelChart, GaugeChart, RadarChart, RadarComponent, SankeyChart, TreemapChart]);
diff --git a/app/ui/controls.module.css b/app/ui/controls.module.css
index ba3ae886..d06c261e 100644
--- a/app/ui/controls.module.css
+++ b/app/ui/controls.module.css
@@ -33,6 +33,83 @@
   color: var(--color-danger-text);
 }
 
+/* A label with its ? hint beside it. */
+.labelRow {
+  align-items: center;
+  display: flex;
+  gap: var(--space-2);
+  min-width: 0;
+}
+
+.hint {
+  display: inline-flex;
+  flex: none;
+}
+
+/* The visible circle stays small. A transparent ring around it gives a comfortable tap target. */
+.hintButton {
+  align-items: center;
+  background: transparent;
+  border: 0;
+  color: var(--color-text-muted);
+  cursor: help;
+  display: inline-grid;
+  height: 24px;
+  justify-content: center;
+  margin: -4px;
+  padding: 0;
+  width: 24px;
+}
+
+.hintButton > span {
+  align-items: center;
+  border: 1px solid currentColor;
+  border-radius: 50%;
+  display: inline-grid;
+  font-family: var(--font-display);
+  font-size: 11px;
+  font-weight: var(--weight-semibold);
+  height: 15px;
+  justify-content: center;
+  line-height: 1;
+  width: 15px;
+}
+
+.hintButton:hover,
+.hintButton[data-open] {
+  color: var(--color-text);
+}
+
+.hintButton:focus-visible {
+  border-radius: 50%;
+  box-shadow: var(--focus-ring);
+  outline: none;
+}
+
+.hintBubble {
+  background: var(--color-surface);
+  border: 1px solid var(--color-border-strong);
+  border-radius: var(--radius);
+  box-shadow: 0 12px 30px var(--color-overlay);
+  color: var(--color-text);
+  font-family: var(--font-sans);
+  font-size: var(--text-small);
+  font-weight: var(--weight-regular);
+  left: 0;
+  line-height: var(--line-body);
+  max-width: min(18rem, calc(100vw - 16px));
+  padding: var(--space-2) var(--space-3);
+  pointer-events: none;
+  position: fixed;
+  top: 0;
+  width: max-content;
+  z-index: 120;
+}
+
+.hintBubble[hidden] {
+  display: none;
+}
+
 .input,
 .textarea,
 .searchControl,
@@ -1392,6 +1469,120 @@
   font-family: var(--font-mono);
 }
 
+.metricGroup dt > .hint {
+  margin-left: var(--space-2);
+  vertical-align: middle;
+}
+
+/* One row per number: label left, value right, read top to bottom. */
+.metricGroup[data-layout="list"] {
+  grid-template-columns: minmax(0, 1fr);
+}
+
+/* The value drops under its label when both don't fit on one line. */
+.metricGroup[data-layout="list"] > div {
+  align-items: baseline;
+  column-gap: var(--space-5);
+  display: flex;
+  flex-wrap: wrap;
+  padding: var(--space-3) 0;
+  row-gap: var(--space-1);
+}
+
+.metricGroup[data-layout="list"] dt {
+  flex: 1 1 auto;
+}
+
+.metricGroup[data-layout="list"] dd {
+  justify-content: flex-end;
+  margin-left: auto;
+  max-width: 100%;
+}
+
+.metricGroup[data-layout="list"] dt {
+  font-size: var(--text-body);
+}
+
+.metricGroup[data-layout="list"] dd strong {
+  font-size: var(--text-body);
+  font-weight: var(--weight-semibold);
+  overflow-wrap: normal;
+  text-align: right;
+}
+
+.unitFigure {
+  display: grid;
+  gap: var(--space-4);
+  margin: 0;
+  max-width: 280px;
+  min-width: 0;
+  width: 100%;
+}
+
+.unitGrid {
+  display: grid;
+  gap: 3px;
+}
+
+/* The inset ring sits under the fill, so a full unit reads as one solid square. */
+.unit {
+  aspect-ratio: 1;
+  background: var(--color-surface-2);
+  border-radius: var(--radius);
+  box-shadow: inset 0 0 0 1px var(--color-border);
+  overflow: hidden;
+  position: relative;
+}
+
+/* Result visuals are data, not accent: the first data color marks the person's own share. */
+.unitFill,
+.unitSwatch[data-filled] {
+  background: var(--color-data-chartreuse);
+}
+
+/* Units up to a target: an outline in the same color, so the gap to the goal reads as one shape. */
+.unit[data-target],
+.unitSwatch[data-target] {
+  box-shadow: inset 0 0 0 2px var(--color-data-chartreuse);
+}
+
+.unitFill {
+  bottom: 0;
+  left: 0;
+  position: absolute;
+  top: 0;
+}
+
+.unitFigure[data-tone="neutral"] .unitFill,
+.unitFigure[data-tone="neutral"] .unitSwatch[data-filled] {
+  background: var(--color-text);
+}
+
+.unitLegend {
+  color: var(--color-text-muted);
+  display: flex;
+  flex-wrap: wrap;
+  font-size: var(--text-small);
+  gap: var(--space-2) var(--space-6);
+  list-style: none;
+  margin: 0;
+  padding: 0;
+}
+
+.unitLegend li {
+  align-items: center;
+  display: inline-flex;
+  gap: var(--space-2);
+}
+
+.unitSwatch {
+  background: var(--color-surface-2);
+  border-radius: var(--radius);
+  box-shadow: inset 0 0 0 1px var(--color-border);
+  height: 10px;
+  width: 10px;
+}
+
 .timeline {
   display: grid;
   grid-auto-columns: minmax(150px, 1fr);
@@ -1716,3 +1907,164 @@
     transition-duration: 0.01ms;
   }
 }
+
+/* Range marker: the person's value against published ranges. Neutral data colors only. */
+.rangeFigure {
+  display: grid;
+  gap: var(--space-4);
+  margin: 0;
+  min-width: 0;
+}
+
+.rangeScale {
+  display: grid;
+  gap: var(--space-2);
+}
+
+/* Room above the track for the marker label. The marker line runs from the label through the track. */
+.rangeLane {
+  padding-top: calc(var(--text-small) * 1.5 + var(--space-2));
+  position: relative;
+}
+
+.rangeTrack {
+  background: var(--color-surface-2);
+  border: 1px solid var(--color-border-strong);
+  border-radius: var(--radius);
+  height: 14px;
+  overflow: hidden;
+  position: relative;
+}
+
+.rangeBand,
+.rangeSwatch {
+  background: var(--color-data-cyan);
+}
+
+.rangeBand {
+  bottom: 0;
+  position: absolute;
+  top: 0;
+}
+
+.rangeBand[data-band="1"],
+.rangeSwatch[data-band="1"] {
+  background: var(--color-data-blue);
+}
+
+.rangeBand[data-band="2"],
+.rangeSwatch[data-band="2"] {
+  background: var(--color-data-violet);
+}
+
+/* The person's likely range sits just under the track, in the first data color, with the marker through it. */
+.rangeSpanLane {
+  height: 6px;
+  margin-top: 3px;
+  position: relative;
+}
+
+.rangeSpan {
+  background: var(--color-data-chartreuse);
+  border-radius: var(--radius);
+  bottom: 0;
+  min-width: 2px;
+  position: absolute;
+  top: 0;
+}
+
+.rangeSwatch[data-span] {
+  background: var(--color-data-chartreuse);
+}
+
+.rangeMarker {
+  background: var(--color-text);
+  bottom: -4px;
+  position: absolute;
+  top: calc(var(--text-small) * 1.5);
+  transform: translateX(-1px);
+  width: 2px;
+}
+
+.rangeMarkerLabel {
+  bottom: 100%;
+  color: var(--color-text);
+  font-size: var(--text-small);
+  left: 50%;
+  line-height: var(--line-ui);
+  padding-bottom: var(--space-1);
+  position: absolute;
+  transform: translateX(-50%);
+  white-space: nowrap;
+}
+
+.rangeMarker[data-edge="start"] .rangeMarkerLabel {
+  left: 0;
+  transform: none;
+}
+
+.rangeMarker[data-edge="end"] .rangeMarkerLabel {
+  left: auto;
+  right: 0;
+  transform: none;
+}
+
+.rangeMarkerLabel strong {
+  font-family: var(--font-mono);
+  font-weight: var(--weight-semibold);
+}
+
+.rangeAxis {
+  color: var(--color-text-muted);
+  display: flex;
+  font-family: var(--font-mono);
+  font-size: var(--text-small);
+  justify-content: space-between;
+  line-height: 1.5;
+}
+
+/* One row per range, value on the right, so long labels never squeeze into columns. */
+.rangeLegend {
+  display: grid;
+  list-style: none;
+  margin: 0;
+  padding: 0;
+}
+
+.rangeLegend li {
+  align-items: baseline;
+  border-top: 1px solid var(--color-border);
+  display: grid;
+  gap: var(--space-3);
+  grid-template-columns: 10px minmax(0, 1fr) auto;
+  min-width: 0;
+  padding: var(--space-3) 0;
+}
+
+.rangeLegend li:last-child {
+  border-bottom: 1px solid var(--color-border);
+}
+
+.rangeLegendLabel {
+  min-width: 0;
+  overflow-wrap: anywhere;
+}
+
+/* The ? stays on the last line of a wrapped label instead of floating beside the whole block. */
+.rangeLegendLabel > .hint {
+  margin-left: var(--space-2);
+  vertical-align: middle;
+}
+
+.rangeLegend strong {
+  font-family: var(--font-mono);
+  font-weight: var(--weight-semibold);
+  text-align: right;
+  white-space: nowrap;
+}
+
+.rangeSwatch {
+  border: 1px solid var(--color-border-strong);
+  height: 10px;
+  width: 10px;
+}
diff --git a/app/ui/controls.tsx b/app/ui/controls.tsx
index a77bffdc..9805d532 100644
--- a/app/ui/controls.tsx
+++ b/app/ui/controls.tsx
@@ -1,6 +1,6 @@
 "use client";
 
-import { CalendarDays, Check, Clock, ChevronDown, ChevronLeft, ChevronRight, Copy, Download, Minus, Plus, Search, X } from "lucide-react";
+import { CalendarDays, Check, Clock, ChevronDown, ChevronLeft, ChevronRight, Copy, Download, Link2, Minus, Plus, Search, X } from "lucide-react";
 import {
   Button as RacButton,
   Calendar as RacCalendar,
@@ -63,6 +63,7 @@ import {
   type ReactNode,
   type Ref,
 } from "react";
+import { createPortal } from "react-dom";
 import styles from "./controls.module.css";
 
 export type UiOption = {
@@ -74,13 +75,20 @@ export type UiOption = {
 
 type FieldCopy = {
   label: string;
+  /** Visible text under the field. Tools use `hint` instead. */
   description?: string;
   error?: string | null;
+  /** One plain sentence behind a small ? beside the label. */
+  hint?: string;
   required?: boolean;
 };
 
-function UiLabel({ label, required }: Pick<FieldCopy, "label" | "required">) {
-  return (
+function subscribeToNothing() {
+  return () => {};
+}
+
+function UiLabel({ hint, label, required }: Pick<FieldCopy, "hint" | "label" | "required">) {
+  const text = (
     <Label className={styles.label}>
       {label}
       {required ? (
@@ -91,17 +99,127 @@ function UiLabel({ label, required }: Pick<FieldCopy, "label" | "required">) {
       ) : null}
     </Label>
   );
+  if (!hint) return text;
+  // The ? sits beside the label, not inside it, so pressing it never moves focus to the field.
+  return (
+    <div className={styles.labelRow}>
+      {text}
+      <UiHint label={label} text={hint} />
+    </div>
+  );
 }
 
-function FieldMessages({ description, error }: Pick<FieldCopy, "description" | "error">) {
+function FieldMessages({ description, error, hint }: Pick<FieldCopy, "description" | "error" | "hint">) {
+  // Screen readers hear the hint as the field's description, so nobody has to find the ? first.
   return (
     <>
-      {description ? <Text className={styles.description} slot="description">{description}</Text> : null}
+      {description ? (
+        <Text className={styles.description} slot="description">
+          {description}
+          {hint ? <span className={styles.visuallyHidden}> {hint}</span> : null}
+        </Text>
+      ) : hint ? (
+        <Text className={styles.visuallyHidden} slot="description">{hint}</Text>
+      ) : null}
       <FieldError className={styles.error}>{error}</FieldError>
     </>
   );
 }
 
+/**
+ * A small ? beside a label. Its one sentence shows on hover, keyboard focus, and tap, so a
+ * tool never needs help text under its fields. A tap or click keeps it open until the next
+ * tap elsewhere, Escape, or leaving the button.
+ */
+export function UiHint({ label, text }: { label: string; text: string }) {
+  const id = useId();
+  // The bubble lives in document.body, so a clipped or transformed parent can't hide or move it.
+  const hydrated = useSyncExternalStore(subscribeToNothing, () => true, () => false);
+  const buttonRef = useRef<HTMLButtonElement>(null);
+  const bubbleRef = useRef<HTMLSpanElement>(null);
+  const pinned = useRef(false);
+  const [open, setOpen] = useState(false);
+
+  const close = useCallback(() => {
+    pinned.current = false;
+    setOpen(false);
+  }, []);
+
+  useLayoutEffect(() => {
+    if (!open) return;
+    // Fixed position keeps the bubble out of any clipped parent. It sits above the ?, moves
+    // below it near the top of the screen, and stays inside the viewport's sides.
+    const place = () => {
+      const button = buttonRef.current;
+      const bubble = bubbleRef.current;
+      if (!button || !bubble) return;
+      const margin = 8;
+      const anchor = button.getBoundingClientRect();
+      const box = bubble.getBoundingClientRect();
+      const viewport = document.documentElement.clientWidth;
+      const centered = anchor.left + anchor.width / 2 - box.width / 2;
+      const left = Math.max(margin, Math.min(centered, viewport - box.width - margin));
+      const above = anchor.top - box.height - 6;
+      bubble.style.left = `${left}px`;
+      bubble.style.top = `${above >= margin ? above : anchor.bottom + 6}px`;
+    };
+    const closeOutside = (event: PointerEvent) => {
+      if (!buttonRef.current?.contains(event.target as Node)) close();
+    };
+    const closeOnEscape = (event: KeyboardEvent) => {
+      if (event.key === "Escape") close();
+    };
+    place();
+    window.addEventListener("resize", place);
+    window.addEventListener("scroll", place, true);
+    document.addEventListener("pointerdown", closeOutside);
+    document.addEventListener("keydown", closeOnEscape);
+    return () => {
+      window.removeEventListener("resize", place);
+      window.removeEventListener("scroll", place, true);
+      document.removeEventListener("pointerdown", closeOutside);
+      document.removeEventListener("keydown", closeOnEscape);
+    };
+  }, [close, open]);
+
+  return (
+    <span className={styles.hint}>
+      <button
+        aria-describedby={id}
+        aria-label={`About ${label}`}
+        className={styles.hintButton}
+        data-open={open || undefined}
+        onBlur={close}
+        onClick={() => {
+          if (open && pinned.current) {
+            close();
+            return;
+          }
+          pinned.current = true;
+          setOpen(true);
+        }}
+        onFocus={(event) => {
+          if (event.currentTarget.matches(":focus-visible")) setOpen(true);
+        }}
+        onPointerEnter={(event) => {
+          if (event.pointerType === "mouse") setOpen(true);
+        }}
+        onPointerLeave={(event) => {
+          if (event.pointerType === "mouse" && !pinned.current) setOpen(false);
+        }}
+        ref={buttonRef}
+        type="button"
+      >
+        <span aria-hidden="true">?</span>
+      </button>
+      {hydrated ? createPortal(
+        <span className={styles.hintBubble} hidden={!open} id={id} ref={bubbleRef} role="tooltip">{text}</span>,
+        document.body,
+      ) : null}
+    </span>
+  );
+}
+
 export type UiTextFieldProps = FieldCopy & {
   autoCapitalize?: "none" | "off" | "sentences" | "words" | "characters";
   autoComplete?: string;
@@ -128,6 +246,7 @@ export function UiTextField({
   dataFocusKey,
   description,
   error,
+  hint,
   inputMode,
   inputRef,
   label,
@@ -154,7 +273,7 @@ export function UiTextField({
       validationBehavior="aria"
       value={value}
     >
-      <UiLabel label={label} required={required} />
+      <UiLabel hint={hint} label={label} required={required} />
       {suffix ? (
         <Group className={styles.numberControl}>
           <Input
@@ -181,7 +300,7 @@ export function UiTextField({
           spellCheck={spellCheck}
         />
       )}
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
     </TextField>
   );
 }
@@ -193,7 +312,7 @@ export type UiSearchFieldProps = FieldCopy & {
   value?: string;
 };
 
-export function UiSearchField({ description, error, label, name, onChange, placeholder, required, value }: UiSearchFieldProps) {
+export function UiSearchField({ description, error, hint, label, name, onChange, placeholder, required, value }: UiSearchFieldProps) {
   return (
     <SearchField
       className={styles.field}
@@ -204,7 +323,7 @@ export function UiSearchField({ description, error, label, name, onChange, place
       validationBehavior="aria"
       value={value}
     >
-      <UiLabel label={label} required={required} />
+      <UiLabel hint={hint} label={label} required={required} />
       <Group className={styles.searchControl}>
         <Search aria-hidden="true" className={styles.leadingIcon} size={18} />
         <Input autoComplete="off" className={styles.searchInput} placeholder={placeholder} />
@@ -212,7 +331,7 @@ export function UiSearchField({ description, error, label, name, onChange, place
           <X aria-hidden="true" size={16} />
         </RacButton>
       </Group>
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
     </SearchField>
   );
 }
@@ -230,7 +349,7 @@ export type UiTextAreaProps = FieldCopy & {
   value?: string;
 };
 
-export function UiTextArea({ autoCapitalize, className = "", description, error, inputRef, label, name, onChange, placeholder, readOnly, required, rows = 4, spellCheck, value }: UiTextAreaProps) {
+export function UiTextArea({ autoCapitalize, className = "", description, error, hint, inputRef, label, name, onChange, placeholder, readOnly, required, rows = 4, spellCheck, value }: UiTextAreaProps) {
   return (
     <TextField
       className={`${styles.field} ${className}`}
@@ -241,9 +360,9 @@ export function UiTextArea({ autoCapitalize, className = "", description, error,
       validationBehavior="aria"
       value={value}
     >
-      <UiLabel label={label} required={required} />
+      <UiLabel hint={hint} label={label} required={required} />
       <TextArea autoCapitalize={autoCapitalize} className={styles.textarea} name={name} placeholder={placeholder} ref={inputRef} rows={rows} spellCheck={spellCheck} />
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
     </TextField>
   );
 }
@@ -274,7 +393,6 @@ export function UiDateTimePicker(props: UiDateTimePickerProps) {
   return <DatePickerBase {...props} granularity="minute" />;
 }
 
-const subscribeToNothing = () => () => {};
 
 /**
  * Date and time segments follow the reader's locale, which the server can't know: it would
@@ -296,6 +414,7 @@ function DatePickerBase({
   disabled,
   error,
   granularity,
+  hint,
   hourCycle = 12,
   label,
   maxValue,
@@ -321,14 +440,14 @@ function DatePickerBase({
       validationBehavior="aria"
       value={value ?? null}
     >
-      <UiLabel label={label} required={required} />
+      <UiLabel hint={hint} label={label} required={required} />
       <Group className={styles.dateControl}>
         <DateSegments />
         <RacButton aria-label={`Open ${label} calendar`} className={styles.dateButton}>
           <CalendarDays aria-hidden="true" size={18} />
         </RacButton>
       </Group>
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
       <Popover className={`${styles.popover} ${styles.calendarPopover}`} placement="bottom start">
         <Dialog className={styles.calendarDialog}>
           {hasTime ? <DateThenTime commit={onChange} hourCycle={hourCycle} maxValue={maxValue} minValue={minValue} minuteStep={minuteStep} /> : <PickerCalendar />}
@@ -432,7 +551,7 @@ export type UiTimeFieldProps = FieldCopy & TimeOptions & {
 };
 
 /** Hours and minutes. Type each part, or open the clock to pick from a list. */
-export function UiTimeField({ description, disabled, error, hourCycle = 12, label, maxValue, minValue, minuteStep = 5, onChange, required, value }: UiTimeFieldProps) {
+export function UiTimeField({ description, disabled, error, hint, hourCycle = 12, label, maxValue, minValue, minuteStep = 5, onChange, required, value }: UiTimeFieldProps) {
   return (
     <TimeField
       className={styles.field}
@@ -446,7 +565,7 @@ export function UiTimeField({ description, disabled, error, hourCycle = 12, labe
       validationBehavior="aria"
       value={value ?? null}
     >
-      <UiLabel label={label} required={required} />
+      <UiLabel hint={hint} label={label} required={required} />
       <Group className={styles.dateControl}>
         <DateSegments />
         <DialogTrigger>
@@ -471,7 +590,7 @@ export function UiTimeField({ description, disabled, error, hourCycle = 12, labe
           </Popover>
         </DialogTrigger>
       </Group>
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
     </TimeField>
   );
 }
@@ -631,6 +750,7 @@ export function UiSelect({
   disabled,
   error,
   hideLabel,
+  hint,
   label,
   name,
   onChange,
@@ -654,13 +774,13 @@ export function UiSelect({
       value={value ?? null}
     >
       <div className={hideLabel ? styles.visuallyHidden : undefined}>
-        <UiLabel label={label} required={required} />
+        <UiLabel hint={hint} label={label} required={required} />
       </div>
       <RacButton className={styles.selectTrigger} data-focus-key={dataFocusKey} data-tool-label={accessibleLabel}>
         <SelectValue className={styles.selectValue} />
         <ChevronDown aria-hidden="true" size={18} />
       </RacButton>
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
       <Popover className={styles.popover} placement="bottom start">
         <ListBox className={styles.listbox} items={options}>
           {(option) => (
@@ -689,7 +809,7 @@ export type UiComboBoxProps = FieldCopy & {
   value?: string | null;
 };
 
-export function UiComboBox({ description, error, label, onChange, onInputChange, onOpenChange, options, placeholder, required, value }: UiComboBoxProps) {
+export function UiComboBox({ description, error, hint, label, onChange, onInputChange, onOpenChange, options, placeholder, required, value }: UiComboBoxProps) {
   const triggerLabelId = useId();
 
   return (
@@ -704,7 +824,7 @@ export function UiComboBox({ description, error, label, onChange, onInputChange,
       validationBehavior="aria"
       value={value ?? null}
     >
-      <UiLabel label={label} required={required} />
+      <UiLabel hint={hint} label={label} required={required} />
       <span className={styles.visuallyHidden} id={triggerLabelId}>Open {label}</span>
       <Group className={styles.comboControl}>
         <Input autoComplete="off" className={styles.comboInput} placeholder={placeholder} />
@@ -712,7 +832,7 @@ export function UiComboBox({ description, error, label, onChange, onInputChange,
           <ChevronDown aria-hidden="true" size={18} />
         </RacButton>
       </Group>
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
       <Popover className={styles.popover} placement="bottom start" shouldFlip={false}>
         <ListBox className={styles.listbox}>
           {(option: UiOption) => (
@@ -753,6 +873,7 @@ export function UiNumberField({
   description,
   disabled,
   error,
+  hint,
   inputRef,
   label,
   max,
@@ -785,6 +906,7 @@ export function UiNumberField({
       <div className={styles.label}>
         {label}
         {required ? <span aria-hidden="true" className={styles.requiredMark}>*</span> : null}
+        {hint ? <UiHint label={label} text={hint} /> : null}
       </div>
       <Group className={styles.numberControl}>
         <RacButton aria-label={`Decrease ${accessibleLabel}`} className={styles.stepButton} slot="decrement">
@@ -796,7 +918,7 @@ export function UiNumberField({
           <Plus aria-hidden="true" size={16} />
         </RacButton>
       </Group>
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
     </NumberField>
   );
 }
@@ -811,6 +933,7 @@ export function UiQuantityField({
   description,
   disabled,
   error,
+  hint,
   label,
   max,
   min,
@@ -823,6 +946,7 @@ export function UiQuantityField({
   units,
   value,
 }: UiQuantityFieldProps) {
+  const hintId = useId();
   return (
     <div className={styles.field}>
       <div className={styles.label}>
@@ -833,9 +957,12 @@ export function UiQuantityField({
             <span className={styles.visuallyHidden}> Required</span>
           </>
         ) : null}
+        {hint ? <UiHint label={label} text={hint} /> : null}
       </div>
+      {hint ? <span className={styles.visuallyHidden} id={hintId}>{hint}</span> : null}
       <div className={styles.quantityControl}>
         <NumberField
+          aria-describedby={hint ? hintId : undefined}
           aria-label={label}
           className={styles.quantityNumber}
           isDisabled={disabled}
@@ -896,6 +1023,7 @@ export function UiQuantityInput({
   description,
   error,
   hideLabel,
+  hint,
   label,
   onChange,
   onUnitChange,
@@ -908,21 +1036,32 @@ export function UiQuantityInput({
 }: UiQuantityInputProps) {
   const inputId = useId();
   const errorId = useId();
+  const hintId = useId();
+  const describedBy = [hint ? hintId : null, error ? errorId : null].filter(Boolean).join(" ") || undefined;
+  const labelElement = (
+    <label className={hideLabel ? styles.visuallyHidden : styles.label} htmlFor={inputId}>
+      {label}
+      {required ? (
+        <>
+          <span aria-hidden="true" className={styles.requiredMark}>*</span>
+          <span className={styles.visuallyHidden}> Required</span>
+        </>
+      ) : null}
+    </label>
+  );
 
   return (
     <div className={styles.field}>
-      <label className={hideLabel ? styles.visuallyHidden : styles.label} htmlFor={inputId}>
-        {label}
-        {required ? (
-          <>
-            <span aria-hidden="true" className={styles.requiredMark}>*</span>
-            <span className={styles.visuallyHidden}> Required</span>
-          </>
-        ) : null}
-      </label>
+      {hint && !hideLabel ? (
+        <div className={styles.labelRow}>
+          {labelElement}
+          <UiHint label={label} text={hint} />
+        </div>
+      ) : labelElement}
+      {hint ? <span className={styles.visuallyHidden} id={hintId}>{hint}</span> : null}
       <div className={styles.quantityControl} data-invalid={Boolean(error) || undefined}>
         <input
-          aria-describedby={error ? errorId : undefined}
+          aria-describedby={describedBy}
           aria-invalid={Boolean(error)}
           aria-label={ariaLabel}
           className={styles.quantityTextInput}
@@ -959,7 +1098,7 @@ export type UiChoiceGroupProps = FieldCopy & {
   value?: string;
 };
 
-export function UiChoiceGroup({ dataFocusKey, description, error, label, name, onChange, options, required, value }: UiChoiceGroupProps) {
+export function UiChoiceGroup({ dataFocusKey, description, error, hint, label, name, onChange, options, required, value }: UiChoiceGroupProps) {
   return (
     <RadioGroup
       className={styles.field}
@@ -970,7 +1109,7 @@ export function UiChoiceGroup({ dataFocusKey, description, error, label, name, o
       validationBehavior="aria"
       value={value}
     >
-      <UiLabel label={label} required={required} />
+      <UiLabel hint={hint} label={label} required={required} />
       <div className={styles.choiceRow}>
         {options.map((option) => (
           <Radio className={styles.choice} data-focus-key={option.id === options[0]?.id ? dataFocusKey : undefined} id={option.id} key={option.id} value={option.id}>
@@ -978,7 +1117,7 @@ export function UiChoiceGroup({ dataFocusKey, description, error, label, name, o
           </Radio>
         ))}
       </div>
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
     </RadioGroup>
   );
 }
@@ -1001,7 +1140,7 @@ export type UiMultiChoiceGroupProps = FieldCopy & {
 };
 
 /** Choose any number of options. Each chip carries a small check box, so it reads differently from the one-choice group. */
-export function UiMultiChoiceGroup({ dataFocusKey, description, error, label, name, onChange, options, required, value }: UiMultiChoiceGroupProps) {
+export function UiMultiChoiceGroup({ dataFocusKey, description, error, hint, label, name, onChange, options, required, value }: UiMultiChoiceGroupProps) {
   return (
     <CheckboxGroup
       className={styles.field}
@@ -1012,7 +1151,7 @@ export function UiMultiChoiceGroup({ dataFocusKey, description, error, label, na
       validationBehavior="aria"
       value={value}
     >
-      <UiLabel label={label} required={required} />
+      <UiLabel hint={hint} label={label} required={required} />
       <div className={styles.choiceRow}>
         {options.map((option) => (
           <RacCheckbox className={`${styles.choice} ${styles.multiChoice}`} data-focus-key={option.id === options[0]?.id ? dataFocusKey : undefined} id={option.id} key={option.id} value={option.id}>
@@ -1021,7 +1160,7 @@ export function UiMultiChoiceGroup({ dataFocusKey, description, error, label, na
           </RacCheckbox>
         ))}
       </div>
-      <FieldMessages description={description} error={error} />
+      <FieldMessages description={description} error={error} hint={hint} />
     </CheckboxGroup>
   );
 }
@@ -1051,41 +1190,57 @@ export function UiSwitch({ children, isDisabled, isSelected, onChange }: { child
 
 type SliderCopy = {
   label: string;
+  /** One plain sentence behind a small ? beside the label. */
+  hint?: string;
   min?: number;
   max?: number;
   step?: number;
   formatOptions?: Intl.NumberFormatOptions;
 };
 
-export function UiSlider({ label, min = 0, max = 100, step = 1, value, onChange, formatOptions }: SliderCopy & { value: number; onChange?: (value: number) => void }) {
+function SliderHintText({ hint, id }: { hint?: string; id: string }) {
+  return hint ? <span className={styles.visuallyHidden} id={id}>{hint}</span> : null;
+}
+
+export function UiSlider({ hint, label, min = 0, max = 100, step = 1, value, onChange, formatOptions }: SliderCopy & { value: number; onChange?: (value: number) => void }) {
+  const hintId = useId();
   return (
     <Slider className={styles.slider} formatOptions={formatOptions} maxValue={max} minValue={min} onChange={onChange} step={step} value={value}>
       <div className={styles.sliderHeader}>
-        <Label className={styles.label}>{label}</Label>
+        <span className={styles.labelRow}>
+          <Label className={styles.label}>{label}</Label>
+          {hint ? <UiHint label={label} text={hint} /> : null}
+        </span>
         <SliderOutput className={styles.sliderOutput} />
       </div>
       <SliderTrack className={styles.sliderTrack}>
         <SliderFill className={styles.sliderFill} />
-        <SliderThumb aria-label={label} className={styles.sliderThumb} />
+        <SliderThumb aria-describedby={hint ? hintId : undefined} aria-label={label} className={styles.sliderThumb} />
       </SliderTrack>
+      <SliderHintText hint={hint} id={hintId} />
     </Slider>
   );
 }
 
-export function UiRangeSlider({ label, min = 0, max = 100, step = 1, value, onChange, formatOptions }: SliderCopy & { value: number[]; onChange?: (value: number[]) => void }) {
+export function UiRangeSlider({ hint, label, min = 0, max = 100, step = 1, value, onChange, formatOptions }: SliderCopy & { value: number[]; onChange?: (value: number[]) => void }) {
+  const hintId = useId();
   return (
     <Slider className={styles.slider} formatOptions={formatOptions} maxValue={max} minValue={min} onChange={onChange} step={step} value={value}>
       <div className={styles.sliderHeader}>
-        <Label className={styles.label}>{label}</Label>
+        <span className={styles.labelRow}>
+          <Label className={styles.label}>{label}</Label>
+          {hint ? <UiHint label={label} text={hint} /> : null}
+        </span>
         <SliderOutput className={styles.sliderOutput}>
           {({ state }) => state.values.map((item) => state.getFormattedValue(item)).join(" to ")}
         </SliderOutput>
       </div>
       <SliderTrack className={styles.sliderTrack}>
         <SliderFill className={styles.sliderFill} />
-        <SliderThumb aria-label={`${label} minimum`} className={styles.sliderThumb} index={0} />
-        <SliderThumb aria-label={`${label} maximum`} className={styles.sliderThumb} index={1} />
+        <SliderThumb aria-describedby={hint ? hintId : undefined} aria-label={`${label} minimum`} className={styles.sliderThumb} index={0} />
+        <SliderThumb aria-describedby={hint ? hintId : undefined} aria-label={`${label} maximum`} className={styles.sliderThumb} index={1} />
       </SliderTrack>
+      <SliderHintText hint={hint} id={hintId} />
     </Slider>
   );
 }
@@ -1096,7 +1251,8 @@ export type UiLevel = Readonly<{
   label: string;
 }>;
 
-export function UiLevelSlider({ label, levels, onChange, value }: { label: string; levels: readonly UiLevel[]; onChange?: (value: string) => void; value: string }) {
+export function UiLevelSlider({ hint, label, levels, onChange, value }: { hint?: string; label: string; levels: readonly UiLevel[]; onChange?: (value: string) => void; value: string }) {
+  const hintId = useId();
   const selectedIndex = Math.max(0, levels.findIndex((level) => level.id === value));
   const selected = levels[selectedIndex];
   if (!selected || levels.length < 2) return null;
@@ -1111,17 +1267,21 @@ export function UiLevelSlider({ label, levels, onChange, value }: { label: strin
       value={selectedIndex}
     >
       <div className={styles.sliderHeader}>
-        <Label className={styles.label}>{label}</Label>
+        <span className={styles.labelRow}>
+          <Label className={styles.label}>{label}</Label>
+          {hint ? <UiHint label={label} text={hint} /> : null}
+        </span>
         <SliderOutput className={styles.levelOutput}>{selected.label}</SliderOutput>
       </div>
       <SliderTrack className={styles.sliderTrack} data-tool-level-track>
         <SliderFill className={styles.sliderFill} data-tool-level-fill />
-        <SliderThumb aria-label={label} aria-valuetext={selected.label} className={styles.sliderThumb} />
+        <SliderThumb aria-describedby={hint ? hintId : undefined} aria-label={label} aria-valuetext={selected.label} className={styles.sliderThumb} />
       </SliderTrack>
       <div aria-hidden="true" className={styles.levelMarks} style={{ gridTemplateColumns: `repeat(${levels.length}, minmax(0, 1fr))` }}>
         {levels.map((level) => <span data-selected={level.id === selected.id || undefined} key={level.id}>{level.label}</span>)}
       </div>
       {selected.description ? <p className={styles.levelDescription}>{selected.description}</p> : null}
+      <SliderHintText hint={hint} id={hintId} />
     </Slider>
   );
 }
@@ -1164,6 +1324,11 @@ export function UiDisclosure({
   );
 }
 
+/** The closed summary for an Advanced disclosure: `Not used`, or how many optional values are set. */
+export function uiSetSummary(count: number): string {
+  return count > 0 ? `${count} set` : "Not used";
+}
+
 export function UiRepeatableList<T extends { id: string }>({
   addDescription,
   addDescriptionIsError = false,
@@ -1323,6 +1488,7 @@ export function UiCopyAction({
 }) {
   const [copied, setCopied] = useState(false);
   const [failed, setFailed] = useState(false);
+  const fallbackId = useId();
 
   async function copy() {
     const didCopy = await copyText(value);
@@ -1345,8 +1511,64 @@ export function UiCopyAction({
       </span>
       {failed && withManualFallback ? (
         <div className={styles.copyFallback}>
-          <label>Select and copy this text manually.</label>
-          <textarea onFocus={(event) => event.currentTarget.select()} readOnly rows={5} value={value} />
+          <label htmlFor={fallbackId}>Select and copy this text manually.</label>
+          <textarea id={fallbackId} onFocus={(event) => event.currentTarget.select()} readOnly rows={5} value={value} />
+        </div>
+      ) : null}
+    </div>
+  );
+}
+
+export type UiShareParams = Record<string, string | number | null | undefined>;
+
+/**
+ * Copies a link that reopens the tool with the same inputs. Empty values stay out of the link.
+ * It leaves the address bar alone. The tool reads the link back with `useInitialQuery()`.
+ */
+export function UiShareAction({
+  failureLabel = "Copy failed",
+  label = "Copy link",
+  params,
+  successLabel = "Link copied",
+  variant = "secondary",
+}: {
+  failureLabel?: string;
+  label?: string;
+  params: UiShareParams;
+  successLabel?: string;
+  variant?: UiButtonProps["variant"];
+}) {
+  const [copied, setCopied] = useState(false);
+  const [fallback, setFallback] = useState<string | null>(null);
+  const fallbackId = useId();
+
+  async function share() {
+    const url = new URL(window.location.pathname, window.location.origin);
+    for (const [key, value] of Object.entries(params)) {
+      const text = value === null || value === undefined ? "" : String(value).trim();
+      if (text) url.searchParams.set(key, text);
+    }
+    const link = url.toString();
+    const didCopy = await copyText(link);
+    setFallback(didCopy ? null : link);
+    if (!didCopy) return;
+    setCopied(true);
+    window.setTimeout(() => setCopied(false), 1600);
+  }
+
+  return (
+    <div className={styles.copyAction}>
+      <UiButton aria-label={fallback ? failureLabel : copied ? successLabel : label} onPress={share} variant={variant}>
+        {copied ? <Check aria-hidden="true" size={17} /> : <Link2 aria-hidden="true" size={17} />}
+        {fallback ? failureLabel : copied ? successLabel : label}
+      </UiButton>
+      <span aria-live="polite" className={styles.visuallyHidden} role="status">
+        {fallback ? `${failureLabel}. Select the link manually.` : copied ? successLabel : ""}
+      </span>
+      {fallback ? (
+        <div className={styles.copyFallback}>
+          <label htmlFor={fallbackId}>Select and copy this link.</label>
+          <textarea id={fallbackId} onFocus={(event) => event.currentTarget.select()} readOnly rows={2} value={fallback} />
         </div>
       ) : null}
     </div>
diff --git a/app/ui/display.tsx b/app/ui/display.tsx
index 07878e53..7fa7e994 100644
--- a/app/ui/display.tsx
+++ b/app/ui/display.tsx
@@ -1,5 +1,6 @@
 import { ArrowRight, Check, Circle } from "lucide-react";
 import type { ReactNode, Ref } from "react";
+import { UiHint } from "./controls";
 import { TableFrame } from "./table-frame";
 import styles from "./controls.module.css";
 
@@ -73,6 +74,198 @@ export function UiProgressBar({
   );
 }
 
+export type UiRangeBand = {
+  id: string;
+  from: number;
+  to: number;
+  /** A plain name, such as `Median, no-card trials`. Never a grade. */
+  label: string;
+  /** The range as people read it, such as `4 to 6%`. */
+  valueText: string;
+  /** One sentence naming the source, such as `ChartMogul survey, January 2026.` */
+  hint?: string;
+};
+
+/** The span the person's own value probably sits in, such as a likely range at a small sample size. */
+export type UiRangeSpan = {
+  from: number;
+  to: number;
+  /** A plain name, such as `Likely range at 500 starts`. */
+  label: string;
+  /** The span as people read it, such as `5.92 to 10.72%`. */
+  valueText: string;
+  /** One sentence on what the span means. */
+  hint?: string;
+};
+
+// Callers check the scale and value are finite first.
+function rangePercent(value: number, min: number, max: number) {
+  return Math.min(100, Math.max(0, (value - min) / (max - min) * 100));
+}
+
+/**
+ * Where the person's value sits next to published ranges. It shows position only: no grade,
+ * and no success or danger colors, because a healthy number differs by niche.
+ */
+export function UiRangeMarker({
+  ariaLabel,
+  bands,
+  max,
+  maxText,
+  min = 0,
+  minText,
+  range,
+  value,
+  valueText,
+  youLabel = "You",
+}: {
+  ariaLabel: string;
+  bands: readonly UiRangeBand[];
+  max: number;
+  maxText: string;
+  min?: number;
+  minText: string;
+  /** The span the person's value probably sits in. It draws under the track in the first data color. */
+  range?: UiRangeSpan;
+  value: number;
+  valueText: string;
+  youLabel?: string;
+}) {
+  // A broken scale or value draws nothing rather than a marker in the wrong place.
+  const hasScale = Number.isFinite(min) && Number.isFinite(max) && max > min;
+  const hasValue = hasScale && Number.isFinite(value);
+  const position = hasValue ? rangePercent(value, min, max) : 0;
+  const edge = position < 15 ? "start" : position > 85 ? "end" : undefined;
+  const hasRange = hasScale && range !== undefined && Number.isFinite(range.from) && Number.isFinite(range.to);
+  const rangeFrom = hasRange ? rangePercent(Math.min(range.from, range.to), min, max) : 0;
+  const rangeTo = hasRange ? rangePercent(Math.max(range.from, range.to), min, max) : 0;
+
+  return (
+    <figure aria-label={ariaLabel} className={styles.rangeFigure}>
+      {hasScale ? <div aria-hidden="true" className={styles.rangeScale}>
+        <div className={styles.rangeLane}>
+          <div className={styles.rangeTrack}>
+            {bands.map((band, index) => {
+              if (!Number.isFinite(band.from) || !Number.isFinite(band.to)) return null;
+              const from = rangePercent(Math.min(band.from, band.to), min, max);
+              const to = rangePercent(Math.max(band.from, band.to), min, max);
+              return to > from ? (
+                <span className={styles.rangeBand} data-band={index % 3} key={band.id} style={{ left: `${from}%`, width: `${to - from}%` }} />
+              ) : null;
+            })}
+          </div>
+          {hasRange ? (
+            <div className={styles.rangeSpanLane}>
+              <span className={styles.rangeSpan} style={{ left: `${rangeFrom}%`, width: `${rangeTo - rangeFrom}%` }} />
+            </div>
+          ) : null}
+          {hasValue ? (
+            <span className={styles.rangeMarker} data-edge={edge} style={{ left: `${position}%` }}>
+              <span className={styles.rangeMarkerLabel}>{youLabel} <strong>{valueText}</strong></span>
+            </span>
+          ) : null}
+        </div>
+        <div className={styles.rangeAxis}>
+          <span>{minText}</span>
+          <span>{maxText}</span>
+        </div>
+      </div> : null}
+      <figcaption>
+        {hasValue ? <span className={styles.visuallyHidden}>{youLabel}: {valueText}.</span> : null}
+        <ul className={styles.rangeLegend}>
+          {hasRange ? (
+            <li>
+              <span aria-hidden="true" className={styles.rangeSwatch} data-span="" />
+              <span className={styles.rangeLegendLabel}>
+                {range.label}
+                {range.hint ? <UiHint label={range.label} text={range.hint} /> : null}
+              </span>
+              <strong>{range.valueText}</strong>
+            </li>
+          ) : null}
+          {bands.map((band, index) => (
+            <li key={band.id}>
+              <span aria-hidden="true" className={styles.rangeSwatch} data-band={index % 3} />
+              <span className={styles.rangeLegendLabel}>
+                {band.label}
+                {band.hint ? <UiHint label={band.label} text={band.hint} /> : null}
+              </span>
+              <strong>{band.valueText}</strong>
+            </li>
+          ))}
+        </ul>
+      </figcaption>
+    </figure>
+  );
+}
+
+/**
+ * A share of a group as filled units, such as 8 paid out of every 100 who started. Units fill
+ * row by row, and the last one fills partly, so 13.22 fills 13 units and a fifth of the next.
+ */
+export function UiUnitGrid({
+  ariaLabel,
+  columns = 10,
+  emptyLabel,
+  filled,
+  filledLabel,
+  target,
+  tone = "accent",
+  units = 100,
+  valueText,
+}: {
+  ariaLabel: string;
+  columns?: number;
+  emptyLabel: string;
+  /** How many units to fill, from 0 to `units`. A fraction fills the last unit partly. */
+  filled: number;
+  filledLabel: string;
+  /** A goal above the filled amount. Units between the two draw outlined, so the gap shows. */
+  target?: { amount: number; label: string; valueText: string };
+  /** `accent` fills with the first data color, `neutral` with the text color. */
+  tone?: "accent" | "neutral";
+  units?: number;
+  /** The filled amount as people read it, such as `8 of every 100`. Screen readers hear it. */
+  valueText: string;
+}) {
+  const requested = Number.isInteger(units) && units > 0 ? units : 100;
+  // Large groups draw at most 400 cells, scaled, so the filled share stays true.
+  const count = Math.min(requested, 400);
+  const scale = count / requested;
+  const perRow = Number.isInteger(columns) && columns > 0 ? Math.min(columns, count) : 10;
+  const rawFilled = Number.isFinite(filled) ? Math.max(0, filled) : 0;
+  const rawGoal = target && Number.isFinite(target.amount) ? Math.max(0, target.amount) : 0;
+  const amount = Math.min(count, rawFilled * scale);
+  const goal = Math.min(count, rawGoal * scale);
+  // A goal past the grid still counts as unmet: the cells can't show it, so the legend and text do.
+  const showsTarget = target !== undefined && rawGoal > rawFilled;
+
+  return (
+    <figure aria-label={ariaLabel} className={styles.unitFigure} data-tone={tone}>
+      <div aria-hidden="true" className={styles.unitGrid} style={{ gridTemplateColumns: `repeat(${perRow}, minmax(0, 1fr))` }}>
+        {Array.from({ length: count }, (_, index) => {
+          const fill = Math.min(1, Math.max(0, amount - index));
+          return (
+            <span className={styles.unit} data-target={showsTarget && fill < 1 && goal > index ? "" : undefined} key={index}>
+              {fill > 0 ? <span className={styles.unitFill} style={{ width: `${(fill * 100).toFixed(2)}%` }} /> : null}
+            </span>
+          );
+        })}
+      </div>
+      <figcaption>
+        <span className={styles.visuallyHidden}>
+          {filledLabel}: {valueText}.{showsTarget ? ` ${target.label}: ${target.valueText}.` : null}
+        </span>
+        <ul aria-hidden="true" className={styles.unitLegend}>
+          <li><span className={styles.unitSwatch} data-filled="" />{filledLabel}</li>
+          {showsTarget ? <li><span className={styles.unitSwatch} data-target="" />{target.label}</li> : null}
+          <li><span className={styles.unitSwatch} />{emptyLabel}</li>
+        </ul>
+      </figcaption>
+    </figure>
+  );
+}
+
 export type UiAllocationPalette = "neutral" | "accent" | "categorical";
 
 export type UiAllocationTone =
@@ -218,16 +411,25 @@ export function UiCodeOutput({
 export type UiMetric = {
   id: string;
   label: string;
+  /** One plain sentence behind a small ? beside the label. */
+  hint?: string;
   unit?: ReactNode;
   value: ReactNode;
 };
 
-export function UiMetricGroup({ ariaLabel, items }: { ariaLabel: string; items: UiMetric[] }) {
+/**
+ * Supporting numbers under a main answer. `columns` spreads them across the width. `list` gives
+ * one row per number, label left and value right, for numbers people read down.
+ */
+export function UiMetricGroup({ ariaLabel, items, layout = "columns" }: { ariaLabel: string; items: UiMetric[]; layout?: "columns" | "list" }) {
   return (
-    <dl aria-label={ariaLabel} className={styles.metricGroup}>
+    <dl aria-label={ariaLabel} className={styles.metricGroup} data-layout={layout === "list" ? "list" : undefined}>
       {items.map((item) => (
         <div key={item.id}>
-          <dt>{item.label}</dt>
+          <dt>
+            {item.label}
+            {item.hint ? <UiHint label={item.label} text={item.hint} /> : null}
+          </dt>
           <dd>
             <strong>{item.value}</strong>
             {item.unit ? <span>{item.unit}</span> : null}
diff --git a/app/ui/tools/tool-workbench.module.css b/app/ui/tools/tool-workbench.module.css
new file mode 100644
index 00000000..7992fd2a
--- /dev/null
+++ b/app/ui/tools/tool-workbench.module.css
@@ -0,0 +1,43 @@
+/* The band. Its surface and rules span the main column; tool-workbench.css draws them. */
+.workbench {
+  grid-column: 1 / -1;
+  min-width: 0;
+  padding-block: var(--space-7);
+}
+
+/* The working width every tool shares. Inputs and results fill it; nothing sits in a narrow island. */
+.content {
+  display: grid;
+  gap: var(--space-7);
+  margin-inline: auto;
+  max-width: 66rem;
+  min-width: 0;
+  width: 100%;
+}
+
+.fieldRow {
+  align-items: start;
+  display: grid;
+  gap: var(--space-5);
+  grid-template-columns: repeat(auto-fit, minmax(min(100%, 13rem), 1fr));
+  min-width: 0;
+}
+
+.fieldRow > * {
+  min-width: 0;
+}
+
+.result {
+  border-top: 1px solid var(--color-border);
+  display: grid;
+  gap: var(--space-6);
+  min-width: 0;
+  padding-top: var(--space-7);
+}
+
+/* A result from older inputs steps back until the person calculates again: its visuals lose their
+   color. Its words keep full contrast, and the tool's status says the inputs changed. */
+.result[data-stale] {
+  filter: grayscale(1);
+  transition: filter var(--motion-fast);
+}
diff --git a/app/ui/tools/tool-workbench.tsx b/app/ui/tools/tool-workbench.tsx
new file mode 100644
index 00000000..b8544cf3
--- /dev/null
+++ b/app/ui/tools/tool-workbench.tsx
@@ -0,0 +1,45 @@
+import type { ComponentPropsWithoutRef, ReactNode, Ref } from "react";
+import styles from "./tool-workbench.module.css";
+
+/**
+ * The band every tool sits in: a full-width surface, the shared 66rem working width, and the
+ * spacing between the form and the result. Tools put their form and `ToolResult` inside it
+ * instead of writing their own workbench, width, or gaps.
+ */
+export function ToolWorkbench({ children, label }: { children: ReactNode; label: string }) {
+  return (
+    <section aria-label={label} className={styles.workbench} data-tool-workbench>
+      <div className={styles.content}>{children}</div>
+    </section>
+  );
+}
+
+/** Fields that belong to one decision. They share a row on wide screens and stack on phones. */
+export function ToolFieldRow({ children, className = "" }: { children: ReactNode; className?: string }) {
+  return <div className={`${styles.fieldRow} ${className}`}>{children}</div>;
+}
+
+/**
+ * The result region, below one divider. It keeps its place in the layout in every state, so the
+ * page never jumps when a result appears, goes stale, or can't be calculated.
+ */
+export function ToolResult({
+  children,
+  className = "",
+  label,
+  ref,
+  stale = false,
+  ...props
+}: Omit<ComponentPropsWithoutRef<"section">, "aria-label"> & {
+  children: ReactNode;
+  label: string;
+  ref?: Ref<HTMLElement>;
+  /** The inputs changed since this result was calculated. */
+  stale?: boolean;
+}) {
+  return (
+    <section {...props} aria-label={label} className={`${styles.result} ${className}`} data-stale={stale || undefined} ref={ref}>
+      {children}
+    </section>
+  );
+}
diff --git a/content_docs/free-trial-conversion-calculator/research.md b/content_docs/free-trial-conversion-calculator/research.md
index b7692826..304b01f8 100644
--- a/content_docs/free-trial-conversion-calculator/research.md
+++ b/content_docs/free-trial-conversion-calculator/research.md
@@ -1,225 +1,237 @@
 # Research: Free trial conversion calculator
 
-Recommended slug: `/free-trial-conversion-calculator`. Live search wording includes "free trial conversion rate calculator" and "free trial conversion calculator." This slug is concise and keeps "free trial," the clearest modifier. Use "free trial to paid" in the page title or description to make the outcome clear. `/trial-conversion-rate-calculator` is less specific; `/trial-to-paid-conversion-calculator` is precise but drops "free trial." This is a wording recommendation from current results, not search-volume data.
-
 Route: `/free-trial-conversion-calculator`  
-Checked: 2026-10-10  
-Competitors used: 5
+Checked: 2026-10-11
+Competitors used: 6 public calculators
 
-## Scope
+## Who uses it
+
+The main searcher is a SaaS founder or operator who has counts for a trial cohort and wants to know what share became paying customers. A growth or product lead may have more detailed cohort and activation data and wants to compare segments or estimate the revenue effect of a change.
+
+| Group | Rough share | What they already know | Their questions, in their words |
+| --- | --- | --- | --- |
+| Most people, such as a founder with one cohort report | Most | Trial starts and paid accounts, often from a billing dashboard or spreadsheet | “What percentage of trial users paid?” “Is 3 out of 160 bad?” “How much more MRR would 5% or 10% bring?” |
+| Pros, such as a growth lead with analytics events | Few | Cohort dates, activation events, trial type, acquisition channel, plan, and time to conversion | “What share converted within 30, 90, or 180 days?” “Where does the funnel lose users?” “Does the result hold by channel, plan, or trial model?” |
+
+These shares are a qualitative read of search results, calculator pages, and forum questions, not measured market shares.
 
-The tool should answer: "Of the people who started a free trial or entered a free product in a defined period, how many became paying customers within a defined follow-up window, and what monthly recurring revenue did those conversions add?" Trial and freemium starts are different cohorts and need separate modes. No-card and card-required trials also need separate labels because their populations and conversion rates differ.
+- Most searchers want the rate, numerator, denominator, and a quick check that they divided the right counts.
+- Most can provide trial starts and paid conversions from one cohort. They may need to look up whether the cohort has had enough time to convert and whether the billing report counts people, accounts, subscriptions, or seats.
+- Pros need a stated observation window, mature cohorts, consistent counting units, and cuts by trial type, plan, channel, or activation. They may also want to model revenue, but a rate alone does not explain retention or acquisition quality.
 
-The core rate is cohort based. A trial that starts in August and pays in September belongs to the August cohort. Counting August conversions divided by August trial starts can miss that conversion, or mix in people whose trials started in July. Users need to choose an event that means "paid" in their billing system and give every cohort the same time to mature. A result for an incomplete cohort is provisional.
+## Published comparison data
+
+| Figure | Source and date | Who was measured | Same definition as the tool? |
+| --- | --- | --- | --- |
+| For free trials without payment details, ChartMogul/ProductLed labels 4–6% “good” and 10–15% “great.” For trials requiring payment details, it labels 25–35% “good” and 50–60% “great.” These bands represent the 50th and 75th percentile in the report, not universal targets. | [ChartMogul SaaS Conversion Report](https://chartmogul.com/reports/saas-conversion-report/), published February 2026. Survey of 200 software products conducted in January 2026. The question measures free signups converting to paid within six months. | Software products, mostly SaaS and AI/SaaS hybrids, typically $1–10M ARR. The free-trial subgroup counts are not published. | Close only when the user's metric is paid conversion from a free-signup cohort over six months and the payment-details model matches. Treat as directional because subgroup size and the survey's exact counting method are not stated. |
+| First Page Sage reports average opt-in trial-to-paid rates of 18.2% for organic and 17.4% for paid traffic, and opt-out rates of 48.8% and 51%. It defines conversion as at least one paid month and warns readers to check retention and churn too. | [First Page Sage SaaS Free Trial Conversion Rate Benchmarks](https://firstpagesage.com/seo-blog/saas-free-trial-conversion-rate-benchmarks/), published September 5, 2025. Data spans Q1 2022–Q3 2025. | Agency data from 86 SaaS companies, 71% B2B and 29% B2C. | Partly. It separates trial model and traffic source, but the page does not state a fixed cohort window. “At least one paid month” does not mean retained revenue. Do not combine with a six-month survey figure. |
+| Recurly reports a 37.5% average site-level trial conversion rate. Sites with billing details averaged 39.0%, compared with 12.0% for trials without billing details. | [Recurly State of Subscriptions: The acquisition chapter](https://recurly.com/resources/report/state-of-subscriptions-acquisition/), page date not stated; underlying data covers January–August 2022. | 22 million subscription-level trial starts from 803 sites managed by Recurly merchants. The overall study covers subscription businesses, including consumer categories. | Similar event, different population and aggregation. Recurly explicitly counts two trial subscriptions from one account as two starts and reports an average site-level rate. It is not a SaaS-only, account-level benchmark. |
+| ChartMogul's help article gives a 3% median across SaaS companies. | [ChartMogul Trial-to-Paid Conversions help article](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate), currently accessible; underlying sample and data period are not stated. | ChartMogul's SaaS company data, with no sample size or cohort window on the page. | It uses a cohort-based trial-to-paid definition, but the page does not define a fixed conversion window. It is not directly comparable to the six-month survey bands. |
 
-The scope does not include churn, retention, revenue recognition, CAC, full funnel attribution, trial activation, or a forecast of future conversions. The MRR result is new recurring run rate from converted accounts, not cash collected, first-year revenue, or MRR retained after churn.
+These sources do not support one blended range. ChartMogul's dated, model-specific six-month bands are the clearest candidate for an optional comparison, but they are survey percentiles and do not publish the size of either trial subgroup. First Page Sage, Recurly, and ChartMogul's help article measure different populations, traffic mixes, aggregation levels, or time windows. If the page shows a comparison, date it, identify the trial model and window, and label it as context rather than a grade.
 
-Searches tried:
+## Scope
 
-- "free trial conversion calculator SaaS trial to paid calculator"
-- "trial conversion rate calculator cohort free trial to paid SaaS"
-- "freemium free to paid conversion rate calculator SaaS"
-- "trial to paid conversion rate calculator benchmarks SaaS"
-- "free trial conversion rate SaaS"
-- "trial to paid conversion benchmark primary study"
-- "trial to paid conversion calculator free SaaS tools"
-- "site:reddit.com/r/SaaS trial to paid cohort"
+The tool's core job is to calculate paid conversions as a share of a stated trial cohort. It can also help a founder estimate new MRR from the cohort if the founder supplies a monthly revenue per new account. It should not claim to predict conversion, diagnose product-market fit, decide whether the company should require payment details, or infer lifetime value from the first paid month.
 
-Search results repeatedly surfaced ChartMogul, Growth Unhinged/ProductLed, First Page Sage, Appcues, Userpilot, Wall Street Prep, Calclet, Agents for Data, TrialMonitor, VentriTools, Technotize, and Recurly. The local SearXNG search endpoint was unavailable, so the search fallback was the web search connector and a live Google results page. No search-volume tool was available. Search wording above is evidence for the slug, not a volume estimate.
+The route is under the `(saas)` tool group and its registry-backed `layout.tsx` remains. The deleted route page, engine, content, test, research file, and spec are absent. The likely primary catalog is `/saas-tools`, based on the current SaaS tool family and sibling SaaS tool docs. The coordinator should confirm the development row's actual catalog membership during planning or integration. No public vendor offers an official, neutral trial-conversion calculator. The official vendor sources found here are analytics and billing documentation, not standalone calculators.
 
-### Existing stack127 tools
+Queries tried:
 
-- `/mrr-calculator` takes paid plan counts, prices, and billing intervals, then normalizes them into MRR and ARR. It does not connect subscriptions to a trial-start cohort.
-- `/customer-acquisition-cost-calculator` divides acquisition spend by new first-time paying customers. Its guidance excludes trials, signups, and renewals from that customer count. It does not calculate trial conversion or cohort MRR.
-- `/saas-metrics-calculator` analyzes a completed month of MRR changes, retention, and growth, with optional CAC and burn inputs. It does not separate trial or free signup cohorts.
+- `free trial conversion rate calculator SaaS`
+- `trial conversion rate calculator SaaS benchmark`
+- `what is a good free trial conversion rate SaaS`
+- `how to calculate free trial to paid conversion rate cohort`
+- `does free trial conversion rate include signups still in trial cohort window`
+- `site:reddit.com/r/SaaS "trial-to-paid" conversion rate free trial users`
+- `site:reddit.com/r/B2BSaaS "credit card" trial conversion rate`
 
-This tool adds early-funnel measurement: trial-start and freemium-start cohorts, a named follow-up window, separate no-card and card-required trial context, and the normalized MRR added by converted customers. It complements the existing tools; it does not replace their CAC or whole-business MRR calculations.
+The calculator results that kept appearing included `agentsfordata.com`, `calcbee.com`, `rightleftagency.com`, `kalkulero.com`, `ventritools.com`, `saaspricelab.com`, and `trialmonitor.io`. Sources that recur for definitions or benchmark claims include ChartMogul, First Page Sage, Recurly, Paddle, and Reddit discussions in r/SaaS and r/B2BSaaS.
 
 ## Search intent
 
 | Query | What the searcher wants | Answer they need | What current results miss |
 | --- | --- | --- | --- |
-| free trial conversion calculator | A quick trial-to-paid rate | A clear numerator, denominator, and result | Many calculators use "started this period" without saying whether conversions came from those same starts. |
-| trial conversion rate calculator cohort | A rate that accounts for trial length and delayed purchases | Start cohort, paid event, and equal follow-up window | Most calculators give a single period rate without cohort maturity or lag. |
-| opt-in vs opt-out trial conversion rate | A way to compare no-card and card-required trials | Plain definitions and model-specific context | Results often use "opt-in/opt-out" inconsistently or compare rates without noting the different friction and populations. |
-| free-to-paid conversion rate calculator | A freemium conversion rate | A separate free-account cohort and measurement window | Some pages treat freemium as a trial despite having no fixed end date. |
-| trial conversion MRR calculator | The recurring revenue associated with newly paid accounts | Monthly normalized recurring value, including annual plans | Competitors may call hypothetical unconverted value "lost revenue," or omit billing interval normalization. |
-| SaaS trial conversion rate benchmarks | A sense of whether a result is plausible | Dated evidence split by business and trial model | Generic "good" bands often lack primary sources, sample details, or a clear definition of conversion. |
+| `free trial conversion rate calculator SaaS` | An immediate rate from two counts | Paid trial-cohort entities divided by all entities in that same cohort, with the count and formula shown | Several results add benchmark scores or revenue estimates before making the cohort and window clear. |
+| `how to calculate free trial to paid conversion rate cohort` | A formula they can reproduce in billing or analytics | A same-cohort numerator and denominator, a conversion window, and a clear counting unit | Search summaries sometimes suggest matching calendar-month totals. Cohort-based conversion can continue to change after the signup month. |
+| `what is a good free trial conversion rate SaaS` | Context for whether their rate is unusually high or low | A comparison split by payment-details requirement and time window, with the study population and date | Results mix SaaS and consumer subscriptions, trial and freemium models, “average” and percentile bands, and different windows. |
+| `credit card required vs no credit card trial conversion` | Whether their trial policy changes the result | Explain that payment details affect both signup volume and conversion among trial starters; compare the whole funnel separately | Many pages compare trial-to-paid rates alone and imply that a higher rate means more paid customers overall. |
+| `trial conversion rate revenue impact calculator` | MRR effect of changing trial conversion | New paid accounts in the cohort multiplied by monthly revenue per account, with retention and annualization assumptions stated | Some pages call a multiplied MRR figure “annual revenue” or “ARR” without saying whether it is run-rate, first-year recognized revenue, or retained revenue. |
+| `SaaS trial activation rate to paid` | Where the signup-to-paid funnel loses people | Distinguish trial-to-activation from activation-to-paid, and define the activation event | Some calculators add activation fields but do not define a product-specific activation event or explain whether paid counts can exceed activated counts. |
+
+Google's “People also ask” questions for `what is a good free trial conversion rate SaaS` on 2026-10-11:
 
-Google's live "People also ask" results included "What is the typical conversion rate for SaaS trials?", "What is a good trial conversion rate?", and "Is 2.5% a good conversion rate?" The same page also showed "What is the 3 3 2 2 2 rule of SaaS?", which is not useful for this calculator. Related searches included "Free trial conversion rate SaaS calculator," "Conversion rate optimization for SaaS trial to paid funnel," "SaaS conversion rate benchmarks," "Activation rate SaaS," and "Average freemium conversion rate."
+- “What is the typical conversion rate for SaaS trials?”
+- “Is 2.5% a good conversion rate?”
+- “What is a good trial conversion rate?”
+- “Is a 10% conversion rate considered good?”
 
-The result that needs the most care is "What is a good trial conversion rate?" No single answer applies across no-card trials, card-required trials, freemium, B2B and consumer products, trial lengths, or sales-assisted funnels. The page should make the rate computable first and show benchmark figures only with their population and date.
+Related searches included `best free trial conversion rate calculator SaaS`, `SaaS free trial conversion rate`, `conversion rate optimization for SaaS trial to paid funnel`, `SaaS conversion rate benchmarks`, `activation rate SaaS`, and `average freemium conversion rate`.
 
 ## User problems
 
 | Problem people repeat | Evidence link | What it means for the tool |
 | --- | --- | --- |
-| Founders debate whether requiring a card improves paid conversion enough to offset fewer or less engaged signups. | [SaaS thread on card required upfront or not](https://www.reddit.com/r/SaaS/comments/1s4dsd5/free_trial_credit_card_required_upfront_or_not/) | Make no-card and card-required modes explicit. Do not present the higher card-required rate as proof that one model is better; signups, activation, refunds, and retention also matter. |
-| A builder moved from a card wall to an email-only seven-day trial and wants paid outcomes rather than signup counts, while weighing server costs. | [SaaS thread on freemium versus card upfront](https://www.reddit.com/r/SaaS/comments/1t6nx4x/freemium_vs_cc_upfront_for_a_7day_trial_just/) | Distinguish free starts from paid conversions, and avoid implying that signup volume alone measures success. A cost or unit-economics model is outside this tool. |
-| Founders ask what trial-to-paid rate others see, while acknowledging that product, audience, activation, and time to convert vary. | [SaaS thread asking for trial conversion rates](https://www.reddit.com/r/SaaS/comments/1ro9ggt/whats_your_trail_to_conversion_rate/) | Show the cohort and measurement window so a user can compare like with like. Explain that one percentage without segment and timing details is hard to interpret. |
-| An adjacent consumer app owner reported a 20.7% blended rate versus 44% for four fully observed weekly cohorts, plus missed analytics events and small-cohort caveats. | [AppBusiness thread on fixing trial conversion tracking](https://www.reddit.com/r/AppBusiness/comments/1upohjk/fixed_my_trial_conversion_21_44_and_just_passed/) | Label cohort maturity and tracking completeness. This is an anecdote from an iOS fitness app, not a SaaS benchmark. |
+| A founder has 160 trial signups and 3 paid accounts and asks whether a 1.9% result means the SaaS is failing. Replies vary by product category and focus on whether the few converted accounts remain. | [“How many of your trial users ended up becoming paying users? Is my SaaS doomed?”](https://www.reddit.com/r/SaaS/comments/1rfdj8o/how_many_of_your_trial_users_ended_up_becoming/), February 26, 2026. Individual reports are not a benchmark. | Show the actual counts with the rate. Do not mark the result healthy or unhealthy from a universal threshold. Keep retention distinct from first paid conversion. |
+| A founder reports 71.43% from 42 trials, then commenters question whether that sample supports a broad conclusion. | [“We just hit 71.43% trial-to-paid conversion rate”](https://www.reddit.com/r/SaaS/comments/1tnrbul/we_just_hit_7143_trialtopaid_conversion_rate/), May 26, 2026. | Preserve the sample size beside the percentage. Avoid strong percentile or health claims from a small cohort. |
+| A B2B SaaS operator with a seven-day, payment-details-required trial asks if 15% is too low and what to change. | [“CC Required Trial → Paid Conversion rates for B2B SaaS?”](https://www.reddit.com/r/B2BSaaS/comments/1ssivq2/cc_required_trial_paid_conversion_rates_for_b2b/), April 22, 2026. | A comparison needs trial model and window. Forum replies provide conflicting targets, so do not treat peer comments as a benchmark. |
+| A founder with 300+ signups and 17 conversions reports about 4% and asks why the trial is underperforming. | [“300+ trial signups, 17 conversions, the real reason most SaaS trials fail”](https://www.reddit.com/r/SaaS/comments/1nocjgp/300_trial_signups_17_conversions_the_real_reason/), September 23, 2025. | The rate alone cannot identify onboarding, audience fit, activation, or trial length as the cause. A funnel breakdown needs defined events and should remain separate from the core calculation. |
 
-These forum posts are qualitative evidence of questions and measurement pain, not representative rate data.
+These are self-reported community examples. Use them to understand questions people ask, not to set benchmark values.
 
 ## Facts to get right
 
 | Fact | Primary source | How the tool should treat it |
 | --- | --- | --- |
-| Cohort rate is the converted share of trial starts from the same start cohort. A cohort can update as later conversions arrive. | [ChartMogul: Trial-to-paid conversion rate](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate) | Use the same start cohort for numerator and denominator. Require or state a follow-up window, or compare cohorts at the same age. Mark immature cohorts provisional. Keep the customer/account/subscription unit consistent. |
-| A rolling-window conversion KPI can use a different denominator and can exceed 100%. Stripe's Billing metric compares conversions in the last 30 days to trials ended in the last 30 days; the two groups need not be the same cohort. | [Stripe: Calculating trial conversion rate in Billing](https://support.stripe.com/questions/calculating-trial-conversion-rate-in-billing?locale=en-GB) | Do not silently call a rolling period rate a cohort conversion rate. Explain why it can differ from the start-cohort answer. |
-| "Paid" depends on billing state. Stripe's subscription lifecycle moves a trialing subscription to active after trial end, and first invoice/payment status affects whether it is paid. | [Stripe Subscription object](https://docs.stripe.com/api/subscriptions/object) | Define the paid event. Do not count a card on file as a conversion. Users should align the event with their billing or analytics source. |
-| Freemium conversion is a free-start cohort, not a time-limited trial cohort. The 2026 ChartMogul report defines free-to-paid as leads or free signups that become paying within six months. | [ChartMogul 2026 SaaS Conversion Report](https://chartmogul.com/reports/saas-conversion-report/) | Give freemium its own mode and state the chosen window. Do not compare its rate with trial rates without showing the difference in model and horizon. |
-| MRR is recurring subscription value normalized to one month. Annual subscriptions are divided by 12; one-time fees are excluded. New Business MRR is recurring revenue from new paying customers. | [ChartMogul: MRR](https://chartmogul.com/saas-metrics/mrr/) | Sum normalized monthly recurring value for the converted cohort, or multiply conversions by a stated average monthly recurring amount. Label it new MRR/run rate; exclude one-time fees. |
-| Recurly's trial chart can use trial start date and distinguishes subscribers from subscriptions. It separates payment failures and pending states from successful paid transitions. | [Recurly: Trial performance](https://docs.recurly.com/recurly-subscriptions/docs/trial-performance) | Be explicit about whether the unit is an account, subscriber, or subscription. Do not mix failed or pending payments into paid conversions. |
+| Trial-to-paid conversion is a cohort measure. ChartMogul counts customers who started a trial and later began a paid subscription, divided by customers who started a trial in the cohort. Later conversions can change the earlier cohort's rate. | [ChartMogul Trial-to-Paid Conversions calculation](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate) | Keep trial starts and paid conversions in the same cohort. Ask for or show the conversion window. Do not divide conversions in one calendar month by starts from a different cohort. |
+| The counting unit changes the result. Recurly counts each trial subscription separately, so one account can contribute more than one start. | [Recurly acquisition report](https://recurly.com/resources/report/state-of-subscriptions-acquisition/) | Use the same unit for both counts, such as customers, accounts, or subscriptions. Name the unit and do not mix accounts with seats or subscriptions. |
+| Cohorts need enough time to mature. ChartMogul says rates can change retroactively as trial users pay later and advises using older intervals relative to the sales cycle. | [ChartMogul report notes](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate) | Label the observation window and whether the cohort has completed it. Treat an immature cohort as provisional, not as a final rate. There is no one conversion window used by every source. |
+| Payment-details-required and cardless trials are different trial models. Requiring payment details may screen signups, while cardless trials lower the signup barrier. The number of paid conversions among starts does not show the visitor-to-paid result. | [Paddle trials documentation](https://developer.paddle.com/concepts/subscriptions/trials/) and [ChartMogul's 2026 report](https://chartmogul.com/reports/saas-conversion-report/) | Compare matching trial models. Do not infer that a higher trial-to-paid percentage means the model produced more paid customers from traffic. “Card required” is common shorthand; billing providers may accept payment methods other than cards. |
+| Published benchmarks vary by sample, model, and time horizon. ChartMogul's 2026 bands refer to free-signup-to-paid conversion within six months; Recurly's 2022 figures are subscription-site averages across wider subscription industries. | [ChartMogul 2026 report](https://chartmogul.com/reports/saas-conversion-report/) and [Recurly acquisition report](https://recurly.com/resources/report/state-of-subscriptions-acquisition/) | If a comparison is shown, cite the date, population, model, and window next to it. Do not merge these studies into a single SaaS average. |
+| Trial duration and conversion window are separate facts. The 2026 ChartMogul/ProductLed survey found 14 days was the most common trial length among products that offered a trial, but it did not establish that 14 days is optimal. | [ChartMogul 2026 report](https://chartmogul.com/reports/saas-conversion-report/) | Do not turn the most common duration into a recommendation. Trial duration alone does not define the conversion window. |
+| A percentage is undefined when there are no trial starts. Paid conversions cannot exceed trial starts for a single cohort and counting unit. | Formula and count constraints; these follow from the definition above. | Require nonnegative whole counts and `paid conversions ≤ trial starts`. For zero starts, explain that the rate cannot be calculated instead of showing 0%. |
+| MRR multiplied by 12 is an annualized run rate, not a measured year of revenue or retained customer value. | [ChartMogul SaaS Go-To-Market report glossary](https://chartmogul.com/reports/saas-go-to-market-report/) | If revenue is modeled, label new MRR and annualized run rate separately. State that retention, billing timing, refunds, and future conversion behavior are not included unless the calculation explicitly models them. |
 
-Recommended calculation:
+Unknown: No neutral primary source establishes a universal conversion window for every SaaS trial. The sources here use six months, a vendor cohort that may update later, or a site-level metric without a stated window.
 
-`trial-to-paid rate = unique eligible accounts from a trial-start cohort that meet the named paid-event rule within the selected window / unique eligible accounts in that same trial-start cohort * 100`
-
-For freemium, replace trial starts with eligible free-account starts. Count unique entities consistently. Use a fixed elapsed window from cohort start, or compare cohorts only after the same elapsed time. A hypothetical example: 100 trials start in August; 6 pay during August and 20 have paid by day 30. The calendar-month ratio is 6%, while the 30-day start-cohort rate is 20%. The latter requires observing that cohort through day 30.
+## Competitor reviews
 
-For added MRR, sum each converted account's recurring subscription amount normalized to a month at the chosen conversion point. For an annual plan, divide its recurring annual amount by 12; exclude setup fees and other one-time charges. This is new-business MRR at conversion, not cash collected, recognized revenue, retained MRR, or money "lost" from people who did not convert. If annualized ARR is shown, describe it as run rate (MRR multiplied by 12), not first-year revenue.
+I found no official, public, stand-alone trial conversion calculator from a billing or analytics provider. I tested six calculators surfaced by searches for SaaS trial conversion calculators. I entered a valid example, a zero-start edge case, and an impossible conversion count where the controls allowed it.
 
-### Benchmark evidence and limits
+### 1. Agents for Data
 
-| Source and date | Population and method | Reported figures | How much to trust it |
-| --- | --- | --- | --- |
-| [ChartMogul, Growth Unhinged, and ProductLed, 2026 SaaS Conversion Report](https://chartmogul.com/reports/saas-conversion-report/) | Survey of 200 software products in January 2026, distributed through email, Slack, and social channels. Typical respondent was reported at $1m-$10m ARR and $50-$249 monthly ARPC. The report includes B2B, consumer, hybrid, and several free models. | "Good" (50th percentile) / "great" (75th percentile): freemium regular signup 3-5% / 8-12%; free trial with no card 4-6% / 10-15%; card-required trial 25-35% / 50-60%. Overall median was 8%. | Dated, sourced, and directly split by model, so it is the most relevant found. It is self-reported survey data with a convenience distribution, mixed product types, and smaller segment counts than the total 200. Use as directional segment evidence, not a universal target or a guarantee. |
-| [First Page Sage, updated September 5, 2025](https://firstpagesage.com/seo-blog/saas-free-trial-conversion-rate-benchmarks/) | Agency data from 86 SaaS clients, Q1 2022 through Q3 2025; 71% B2B and 29% B2C. The page reports organic and paid acquisition separately. | No-card "opt-in" trial to paid: 18.2% organic, 17.4% paid. Card-upfront "opt-out": 48.8% organic, 51% paid. Freemium to paid: 2.6% organic, 2.8% paid. | A dated first-party agency dataset with a stated client count and mix. It is a selected agency client sample; weighting, cohort maturity, and exact attribution details are not fully exposed. The page defines conversion as one paid month, so rates do not establish retention or LTV. Treat as source-specific directional data. |
-| [Recurly State of Subscriptions acquisition report, 2022 data](https://recurly.com/resources/report/state-of-subscriptions-acquisition/) | Recurly operational data from January-August 2022: 22 million free trials across 803 subscription sites. Broad subscription businesses, not only SaaS. Average trial length was 30 days. | Average site-level conversion reported as 37.5%; 87.4% required billing information. Sites requiring billing information averaged 39%, versus 12% without it; average trial lengths also differed (29 versus 39 days). | Large operational dataset with a clear period and site count. It is broad subscription data, not an indie SaaS benchmark, and trial models had different lengths. The report's counting unit can include multiple subscriptions per account. Use to show population and model effects, not to set a SaaS goal. |
-| [Recurly 2024 State of Subscriptions release](https://recurly.com/newsroom/recurly-releases-its-2024-state-of-subscriptions-report/) | Recurly report about subscription businesses, reporting a 2023 median. The public summary does not show conversion-specific sample size or model split. | Median trial-to-paid conversion reported as 50%. | Primary source, but too broad and under-described in the summary for comparison with self-serve SaaS cohorts. Do not combine with the 2022 average or quote as a SaaS norm. |
+URL: [agentsfordata.com/saas/trial-conversion-rate](https://www.agentsfordata.com/saas/trial-conversion-rate)
 
-No primary, dated dataset found for indie SaaS split by trial model, trial length, and equal follow-up window. Common online bands such as "5-25%," "50-70%," and "2-5%" often lack a direct dataset, date, or consistent conversion definition. Mark the benchmark for that exact population as unknown. An Appcues 2022 report result appeared in search, but its linked PDF returned 404 when checked, so its figures were not used.
+- [Observed] It asks for total trial users, paid conversions, trial length, and monthly ARPU. It shows a rate, benchmark label, health score, revenue, and “opportunity” results immediately. Defaults of 75 paid out of 500 produce 15%.
+- [Observed] Correct example: `75 paid / 500 trial starts -> 15%`. Edge: `0 / 0` gives 0% and a prompt to enter users, while its benchmark status still says “Below Average.” Wrong: `120 / 100` gives 120%, “Top 25%,” and -20 users not converted. It does not reject the impossible count.
+- [Documented] The page claims benchmarks for 2024 and labels some ranges “SaaS Industry Benchmarks 2024” and others “OpenView & Lenny's Newsletter SaaS Benchmarks 2024.” The live form has no trial-model selector, although its instructions say to indicate whether a card is required.
+- [Inferred] The health score and fixed ranges can make a mathematically impossible input look like an excellent result. The separate source labels make it hard to know which benchmark is being applied.
+- [Unknown] The page does not show a cohort date or conversion window, and it does not explain the source sample behind the displayed bands.
 
-## Competitor reviews
+```text
+75 paid / 500 starts -> 15%; 0 / 0 -> 0%; 120 / 100 -> 120% and -20 unconverted
+```
 
-### 1. Calclet
+### 2. CalcBee
 
-URL: [Free trial conversion rate calculator](https://www.calclet.com/tools/free-trial-conversion-rate-calculator)
+URL: [calcbee.com/calculators/business/saas/trial-conversion-rate](https://calcbee.com/calculators/business/saas/trial-conversion-rate/)
 
-- [Observed] Inputs are trial starts and paid conversions. The result shows conversion rate and remaining non-converted trials. The labels say "Trials started (period)" and "Converted to paid (same cohort)," which still leaves the actual cohort window to the user.
-- [Observed] Correct: 1,180 starts and 156 paid returns 13.22% and 1,024 not converted. Edge: 0 starts and 0 paid returns 0.00%, though the rate is undefined with a zero denominator. Wrong: 0 starts and 1 paid returns 100% and -1 not converted; the input is not rejected.
-- [Documented] Its accompanying article tells users to compare conversions from the same cohort.
-- [Inferred] A user may trust an impossible 100% result or compare calendar periods without a fixed maturity window.
-- [Unknown] No benchmark methodology or way to set a follow-up window was confirmed.
+- [Observed] It asks for trial starts, paid conversions, average revenue per customer, and trial type. Trial type options combine payment-details requirement with 7, 14, or 30 days. It also shows projected MRR at several conversion rates.
+- [Observed] Correct example: `100 paid / 1,000 starts -> 10%`; at the default $79 ARPU it shows $7,900 new MRR. Edge: `0 / 0` hides the calculation and revenue result. Wrong: `120 / 100` produces 120% and -20 failed trials, without an error.
+- [Documented] The default no-card, 14-day selection displays low 10%, average 20%, and top 30%. The page text also claims 15–30% is common for trials versus 2–5% for freemium, without a source beside that claim.
+- [Inferred] Trial type and scenario modeling are useful, but the range appears baked into the page and is not tied to a visible cohort window.
+- [Unknown] I could not find a dated primary source for its trial-type ranges.
 
 ```text
-1,180 starts -> 156 paid -> 13.22%; 1,024 not converted
-0 starts -> 1 paid -> 100%; -1 not converted
+100 / 1,000 -> 10%; 0 / 0 -> no result; 120 / 100 -> 120% and -20 failed trials
 ```
 
-### 2. Agents for Data
+### 3. Right Left Agency
 
-URL: [SaaS trial conversion rate](https://www.agentsfordata.com/saas/trial-conversion-rate)
+URL: [rightleftagency.com/saas-free-trial-conversion-calculator](https://rightleftagency.com/saas-free-trial-conversion-calculator/)
 
-- [Observed] Inputs include trial users, paid conversions, trial length, and monthly ARPU. Default values of 500, 75, 14 days, and $50 produce a 15.0% rate and $3,750 monthly revenue from converted users.
-- [Observed] Edge: 0 starts and 0 conversions shows 0.0%, "Below Average," and a 10/100 score. Wrong: 100 starts and 101 conversions returns 101.0%, -1 unconverted, and a 100/100 health score; there is no count validation.
-- [Documented] The page labels its benchmarks "SaaS Industry Benchmarks 2024," but the benchmark section did not link a primary dataset during review. Its broad benchmark bands and model-specific figures also conflict: one section calls 15-25% healthy, while another gives opt-in average 15-25%; its card-required ranges are higher still.
-- [Inferred] The score can give false confidence because its thresholds are not traceable and impossible counts are allowed.
-- [Unknown] The source, sample, conversion horizon, and cohort method behind the benchmark score could not be confirmed.
+- [Observed] It asks for monthly signups, activated users, paid customers, and monthly revenue per customer. A Calculate button reveals activation, activated-to-paid conversion, MRR, a funnel, diagnosis, and a target-rate slider. The page also offers an agency audit.
+- [Observed] Correct example: `1,000 starts, 600 activated, 100 paid, $100 ARPU -> 10% trial-to-paid, 60% activation, 16.7% activated-to-paid, $10,000 new MRR`. Edge: zero signups triggers “Monthly free trial signups must be at least 1.” Wrong: 120 paid from 100 starts triggers “Paid customers cannot exceed total trial signups.” In both invalid cases, the previous example's result remains on screen.
+- [Documented] It says values stay in the browser and are not sent or stored. Its input wording counts signups and paid customers “each month,” and it does not ask for a cohort window.
+- [Inferred] Activation detail is useful to a growth operator. A rejected calculation with a stale result can make a reader think the invalid numbers were accepted.
+- [Unknown] The page gives no benchmark source or published conversion range in the tested result.
 
 ```text
-500 starts -> 75 paid -> 15.0%; $50 ARPU -> $3,750 monthly revenue
-100 starts -> 101 paid -> 101.0%; -1 unconverted; score 100/100
+100 paid / 1,000 starts -> 10%; 0 starts -> validation error; 120 paid / 100 starts -> validation error
 ```
 
-### 3. TrialMonitor
+### 4. Kalkulero
 
-URL: [Trial conversion calculator](https://trialmonitor.io/tools/trial-conversion-calculator)
+URL: [kalkulero.com/free-trial-conversion-calculator](https://kalkulero.com/free-trial-conversion-calculator/)
 
-- [Observed] Sliders ask for monthly trial volume, conversion rate, and monthly ARPU. Defaults of 50 starts, 10%, and $49 show 5 customers, $245 new MRR, and $2,940 ARR. The page also labels the 45 non-converters as $2,205 MRR and $26,460 ARR of "lost" revenue.
-- [Observed] Edge: the minimum trial slider value is 10, so a zero-start case cannot be entered. Wrong: attempts below the 1% minimum rate are blocked by the slider. At 50 starts and 1%, the page rounds 0.5 expected customers to one customer and shows $25 MRR.
-- [Documented] It labels converted-customer revenue as new MRR and annualizes it to ARR, and says its estimates exclude churn.
-- [Inferred] "Lost revenue" may lead users to mistake the spend of hypothetical non-converters for revenue they would actually have earned. Rounding fractional expected customers to a whole person hides the estimate.
-- [Unknown] No cohort window or benchmark source was confirmed. The slider-only inputs prevent testing other invalid numeric strings.
+- [Observed] It asks for monthly trial volume, payment-details model, monthly ARPU, activation rate, paid conversion rate, 90-day retention, and monthly ad budget. It shows MRR, annualized ARR, funnel drop-off, retention-adjusted MRR, CAC, and a funnel quality label.
+- [Observed] Correct example: its default `1,200 starts × 6% paid = 72 new customers`; at $79 ARPU it shows $5,688 new MRR and $4,550 retained monthly MRR at day 90. Edge: zero starts gives 0% and a “Leaky Trial Funnel” label. Wrong: entering 120% paid conversion displays 100% and 100 paid out of 100 starts, rather than rejecting the value.
+- [Documented] It offers no-card and card-required models. Its English page includes a German benchmark note that claims 4–8% for no-card and 40–60% for card-required trials. The note has no nearby source. The displayed formula calculates paid users from trial starts, not activated users.
+- [Inferred] The model has more depth than most results, but the many inputs and labels make it hard to see which rate drives which total. The benchmark label and 90-day retention can look like a validated diagnosis even though the assumptions are user-entered.
+- [Unknown] I could not confirm the source or population for its benchmark statement or “funnel quality” labels.
 
 ```text
-50 starts/mo -> 10% -> $49 monthly ARPU -> 5 customers; $245 new MRR; $2,940 ARR
-50 starts/mo -> 1% -> rounds 0.5 expected customer to 1; $25 MRR
+72 / 1,200 -> 6%; 0 / 0 -> 0% with “Leaky” label; 120% input -> displayed as 100%
 ```
 
-### 4. VentriTools
+### 5. SaaSPriceLab
 
-URL: [Free trial conversion calculator](https://ventritools.com/tools/saas/free-trial-conversion-calculator/)
+URL: [saaspricelab.com/saas-metrics-calculators/conversion-revenue](https://www.saaspricelab.com/saas-metrics-calculators/conversion-revenue)
 
-- [Observed] Inputs are monthly trial starts, current rate, target rate, and average revenue per account. Defaults of 500 starts, 4% current, 6% target, and $79 ARPA show 20 versus 30 customers, $1,580 versus $2,370 MRR, $790 incremental MRR, and $9,480 12-month incremental ARR.
-- [Observed] Edge: zero starts with current and target rates set to zero returns zero values. Wrong: entering -5 starts was accepted despite the visible minimum; with 10% current and 20% target it produced negative customer/revenue outputs and an inconsistent positive incremental result.
-- [Documented] The page presents a rate-improvement scenario and says 2-8% is typical for opt-in trials, but no benchmark source was visible during review.
-- [Inferred] It answers "what if I improve this rate?" rather than "what happened to this start cohort?" The user may also mistake annualized run rate for revenue earned in the next year.
-- [Unknown] Cohort definition, benchmark provenance, and whether rates are rounded before revenue calculation were not confirmed.
+- [Observed] It uses sliders for trial starts, paid conversion rate, ARPU, and trial length. It shows conversions, new MRR, annualized value, a revenue projection, and a benchmark panel. Copy, CSV, and share controls are visible; the full benchmark report is gated behind a paid report.
+- [Observed] Correct example: the default `500 starts × 12% = 60 conversions`; at $60 ARPU it shows $3,600 new MRR and $43,200 annualized. Edge: the minimum starts value is 10, so the tool does not allow a zero denominator. Wrong: the paid-rate slider stops at 40%, so keyboard input beyond its maximum remains at 40%.
+- [Documented] Slider bounds are 10–5,000 starts, 1–40% paid conversion, $10–$500 ARPU, and 7–60 trial days. The free result calls 12% “top quartile” but does not expose the benchmark bands; it offers a $19 report.
+- [Inferred] The sliders and export options help scenario work. The hidden benchmark detail makes the visible percentile label hard to audit.
+- [Unknown] I could not verify the benchmark sample or the full trial-length model from the free result.
 
 ```text
-500 starts -> 4% current / 6% target -> 20 / 30 customers; $1,580 / $2,370 MRR
--5 starts -> 10% / 20% -> negative customer and revenue values accepted
+60 / 500 -> 12%; 10 starts is the minimum; paid-rate values above 40% are blocked
 ```
 
-### 5. Technotize
+### 6. VentriTools
 
-URL: [Trial to paid conversion calculator](https://technotize.io/tools/trial-to-paid-conversion-calculator)
+URL: [ventritools.com/tools/saas/free-trial-conversion-calculator](https://ventritools.com/tools/saas/free-trial-conversion-calculator/)
 
-- [Observed] Inputs are trial starts and paid conversions. Correct: 100 starts and 18 conversions returns 18.00%. It also offers an inverse mode for estimating required trials.
-- [Observed] Edge: 0 starts and 0 conversions prompts "Enter trials started above 0." Wrong: 100 starts and 101 conversions is rejected with "Paid conversions must be between 0 and trials."
-- [Documented] Its article says freemium and trial conversion differ and recommends cohort measurement. It does not offer a separate freemium mode or MRR output.
-- [Inferred] It validates the counts better than several competing calculators, but the two input counts alone cannot resolve cross-period lag or cohort maturity.
-- [Unknown] No explicit follow-up window or primary source for its "opt-in often in teens, opt-out 40-60%" benchmark statement was found.
+- [Observed] It asks for monthly trial starts, current rate, monthly revenue per customer, and target rate. It focuses on incremental MRR and an annualized impact.
+- [Observed] Correct example: `1,000 starts, 5% current, $100 ARPU, 6% target -> 50 vs. 60 new customers, $1,000 incremental MRR, $12,000 annualized`. Edge: zero starts produces zero current and target revenue. Wrong: it accepts 120% current conversion on 1,000 starts, producing 1,200 current customers. The result then shows both positive “incremental MRR” and negative additional MRR, while the annualized value is positive.
+- [Documented] The page labels 2–8% as typical for opt-in trials. Its formula is monthly starts × conversion rate × ARPU. It says its 12-month figure multiplies incremental MRR by 12 and excludes customer retention.
+- [Inferred] The narrow conversion lever keeps the calculator easy to scan. Without validation and a clear sign convention, an impossible rate produces contradictory revenue results.
+- [Unknown] The page does not identify a source for the 2–8% range in the result section, and it does not model a cohort window.
 
 ```text
-100 starts -> 18 paid -> 18.00%
-100 starts -> 101 paid -> rejected: paid conversions must be between 0 and trials
+50 / 1,000 -> 5%; 0 starts -> $0; 120% of 1,000 -> 1,200 paid customers
 ```
 
 ## Comparison
 
-| Feature or answer | Calclet | Agents for Data | TrialMonitor | VentriTools | Technotize | What stack127 should do |
-| --- | --- | --- | --- | --- | --- | --- |
-| Core model | Starts and same-cohort paid count | Starts and paid count | Starts multiplied by rate | Monthly starts and current/target rates | Starts and paid count | Use a named start cohort and fixed elapsed window. |
-| Freemium mode | No | No | No | No | Discusses it, no mode | Give freemium its own free-start cohort mode. |
-| No-card/card-required context | No | Labels benchmark bands | No | Mentions opt-in benchmark | Article mentions models | Explain both in plain terms and keep the rates separate. |
-| MRR from conversions | No | Revenue using ARPU | Yes, plus "lost" MRR | Current/target MRR | No | Normalize recurring prices and label new MRR; do not call non-converters lost revenue. |
-| Cohort maturity or horizon | Article mentions same cohort | No confirmed horizon | No confirmed horizon | No confirmed horizon | No confirmed horizon | Show how later conversions and immature cohorts affect the result. |
-| Invalid-count handling | Accepts impossible counts | Accepts conversions above starts | Slider constrains range | Accepted negative starts | Rejects conversions above starts | Reject negative counts and conversions greater than eligible starts. Define zero-denominator behavior as "not available." |
-| Benchmark evidence | No verified data found | 2024 label without direct source; inconsistent bands | No verified data found | Unsourced 2-8% claim | Unsourced model ranges | Use dated, sourced figures with population, method, and caveats. |
+| Feature or answer | Agents for Data | CalcBee | Right Left | Kalkulero | SaaSPriceLab | VentriTools | What Stack127 should do |
+| --- | --- | --- | --- | --- | --- | --- | --- |
+| Core rate | Yes | Yes | Yes | Yes | Yes | Yes | Show the numerator, denominator, and formula beside the rate. |
+| Activation funnel | No | No | Yes | Yes | No | No | Keep activation a separate, defined metric for users who have that event data. |
+| Revenue scenario | Yes | Yes | Yes | Yes | Yes | Yes | Label new MRR and annualized run-rate separately. Do not imply retention or lifetime value. |
+| Trial model or length | Instructions mention card choice but no control | Six trial type and length choices | No | Payment-details model | Trial length slider | No | Treat payment-details model and conversion window as context; do not convert the most common length into advice. |
+| Cohort window | No | No | No | No | No | No | Make the measurement window explicit and keep the paid count within that cohort. |
+| Invalid count handling | Allows >100% | Allows >100% | Rejects but leaves stale results | Clamps to 100% | Slider bounds block values | Allows >100%, with inconsistent scenario signs | Reject impossible counts; clear stale results and explain zero-start cases. |
+| Comparison and grading | Dated-looking but weakly sourced bands and health score | Fixed low/average/top band | No rate benchmark in result | Unsourced benchmark note and quality label | Free result hides ranges behind paid report | Unsourced typical range | Avoid grades. If showing a benchmark, state source, date, population, trial model, and window. |
 
 ## Where competitors disagree
 
-- **Start cohort versus rolling period:** ChartMogul's cohort rate counts paid customers from the trial-start cohort, and the result may rise as the cohort matures. Stripe's Billing metric instead compares conversions and ended trials inside separate rolling 30-day windows; Stripe notes that this rolling measure can exceed 100%. Both can be valid for their stated purpose, but only the same-start-cohort formula answers the tool's cohort question. Do not call the Stripe rolling metric a cohort rate.
-- **What counts as paid:** A paid event may mean an active paid subscription, a successful first invoice, or a subscription that has moved through a billing system's trial state. Stripe's lifecycle makes payment status relevant. The tool should ask the user to align the event to their billing source; a stored card is not itself paid revenue.
-- **Benchmark levels:** ChartMogul's 2026 survey reports lower medians for no-card trials and freemium than for card-required trials. First Page Sage's client sample reports higher no-card trial rates. Recurly's broad subscription data shows another distribution. These populations, dates, acquisition sources, trial lengths, event definitions, and methods differ, so there is no defensible single "good SaaS rate" from these sources.
-- **Model labels:** "Opt-in" and "opt-out" can be ambiguous. Use "no card required upfront" and "card required upfront; subscription starts unless canceled," then explain the model. Freemium should stay separate from a fixed-duration trial.
-- **Revenue labels:** Some competitors describe the estimated spend of non-converters as lost revenue. That assumes every non-converter would have paid. Report only actual cohort conversions and their normalized recurring MRR; a hypothetical recovery scenario should be clearly labeled as a scenario.
+- **Calendar month versus signup cohort.** Search summaries and some tool labels compare monthly trial starts with monthly paid counts. ChartMogul's documented method keeps users with the same trial-start cohort together and allows later conversions to update that cohort. The tool needs a stated observation window; a raw pair of counts without cohort context can be misleading.
+- **What counts as one trial.** Recurly counts subscriptions, including two trial subscriptions held by one account. Other systems may count customers or accounts. The denominator and numerator must use the same unit.
+- **What counts as a “good” result.** ChartMogul's 2026 survey gives good/great bands of 4–6%/10–15% for no-payment-details trials and 25–35%/50–60% for payment-details-required trials, within six months. First Page Sage reports 17–18% and 49–51% averages, but gives no fixed conversion window. Recurly reports 37.5% site-level conversion across a wider subscription market. ChartMogul's help center separately says 3% median for SaaS with no stated sample or window. These values should not be averaged or displayed as if they came from one study.
+- **Trial-to-paid versus retained value.** First Page Sage counts even a single paid month and warns that churn matters. A paid event is not a retained customer or LTV. Likewise, MRR × 12 is an annualized run-rate, not recognized first-year revenue.
 
-## How stack127 can win
+## How Stack127 can win
 
-- Calculate a cohort rate from starts and conversions from the same cohort. Let users select a follow-up window and show whether the cohort has reached it.
-- Keep trial-to-paid and freemium-to-paid as separate modes. For trials, distinguish no-card from card-required upfront in the explanation. Avoid using unexplained "opt-in" and "opt-out" labels alone.
-- Define the paid event and entity counted. Include clear treatment for zero starts, negative numbers, conversions greater than starts, duplicate subscriptions, pending payments, and failed first invoices.
-- Show a small worked example where a conversion in the following month belongs to the original trial-start cohort. Explain that recent cohorts can understate their eventual result.
-- Calculate new MRR only for the converted accounts. Normalize annual billing to monthly value, exclude one-time fees, and state the timestamp used for the recurring amount. Do not call unconverted trial value "lost MRR."
-- Put benchmark figures beside source, date, population, model, and method. Present survey percentiles and agency/client data as directional evidence, not a universal target. For an indie SaaS benchmark split by trial type and equal cohort age, say "unknown."
-- State that trial length, sales assistance, customer type, acquisition channel, activation, and conversion horizon can change the comparison. Keep the tool focused on rate and new MRR; point to the existing CAC and MRR calculators for those separate jobs.
+- Let a founder enter counts from one cohort and verify the answer from a visible formula. Keep the counting unit and conversion window clear.
+- Guard against negative or fractional people, zero denominators, and paid counts above starts. Keep the previous example from looking like the result for rejected inputs.
+- Show the sample size with the percentage. Do not assign a health score from one number, especially for a small or immature cohort.
+- Keep optional funnel or revenue analysis tied to explicit definitions. Activation is product-specific. Revenue scenarios need an ARPU and should distinguish new MRR from annualized run-rate and retention-adjusted revenue.
+- If the page shows comparison data, use the dated ChartMogul/ProductLed survey as model-specific, six-month context. Say its trial subgroup size is not disclosed. Do not use Recurly's broader site average or unsourced tool ranges as a SaaS target.
+- The tool needs no paid API, external account, or maintained live dataset. A benchmark section would need source review and date updates as new studies appear.
 
 ## Blockers
 
-None for the calculation or initial page. No paid API, account, or maintained live dataset is required. The exact benchmark for indie SaaS by card model, trial length, and equal follow-up window remains unknown; use the dated sources above with their limits or omit a universal target.
+None. No paid API or maintained dataset is needed for the core calculation. Benchmark claims need dated source references and review, but the calculator itself can use user-entered counts.
 
 ## Sources
 
-- [ChartMogul: Trial-to-paid conversion rate](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate), checked 2026-10-10.
-- [Stripe: Calculating trial conversion rate in Billing](https://support.stripe.com/questions/calculating-trial-conversion-rate-in-billing?locale=en-GB), checked 2026-10-10.
-- [Stripe Subscription object](https://docs.stripe.com/api/subscriptions/object), checked 2026-10-10.
-- [ChartMogul: MRR](https://chartmogul.com/saas-metrics/mrr/), checked 2026-10-10.
-- [ChartMogul, Growth Unhinged, and ProductLed: 2026 SaaS Conversion Report](https://chartmogul.com/reports/saas-conversion-report/), checked 2026-10-10.
-- [First Page Sage: SaaS free trial conversion rate benchmarks](https://firstpagesage.com/seo-blog/saas-free-trial-conversion-rate-benchmarks/), updated 2025-09-05, checked 2026-10-10.
-- [Recurly: State of Subscriptions acquisition report](https://recurly.com/resources/report/state-of-subscriptions-acquisition/), 2022 data, checked 2026-10-10.
-- [Recurly: 2024 State of Subscriptions report release](https://recurly.com/newsroom/recurly-releases-its-2024-state-of-subscriptions-report/), checked 2026-10-10.
-- [Recurly: Trial performance](https://docs.recurly.com/recurly-subscriptions/docs/trial-performance), checked 2026-10-10.
-- [Calclet calculator](https://www.calclet.com/tools/free-trial-conversion-rate-calculator), checked 2026-10-10.
-- [Agents for Data calculator](https://www.agentsfordata.com/saas/trial-conversion-rate), checked 2026-10-10.
-- [TrialMonitor calculator](https://trialmonitor.io/tools/trial-conversion-calculator), checked 2026-10-10.
-- [VentriTools calculator](https://ventritools.com/tools/saas/free-trial-conversion-calculator/), checked 2026-10-10.
-- [Technotize calculator](https://technotize.io/tools/trial-to-paid-conversion-calculator), checked 2026-10-10.
-- [Reddit: card-required trial discussion](https://www.reddit.com/r/SaaS/comments/1s4dsd5/free_trial_credit_card_required_upfront_or_not/), checked 2026-10-10.
-- [Reddit: freemium versus card upfront discussion](https://www.reddit.com/r/SaaS/comments/1t6nx4x/freemium_vs_cc_upfront_for_a_7day_trial_just/), checked 2026-10-10.
-- [Reddit: trial conversion rate discussion](https://www.reddit.com/r/SaaS/comments/1ro9ggt/whats_your_trail_to_conversion_rate/), checked 2026-10-10.
-- [Reddit: AppBusiness trial conversion tracking discussion](https://www.reddit.com/r/AppBusiness/comments/1upohjk/fixed_my_trial_conversion_21_44_and_just_passed/), checked 2026-10-10.
-- [Appcues 2022 Benchmark Report PDF](https://try.appcues.com/hubfs/2022-Appcues-Benchmark-Report.pdf), returned 404 when checked 2026-10-10; figures not used.
+- [Google search: free trial conversion rate calculator SaaS](https://www.google.com/search?q=free+trial+conversion+rate+calculator+saas), checked 2026-10-11.
+- [Google search: what is a good free trial conversion rate SaaS, including People also ask](https://www.google.com/search?q=what+is+a+good+free+trial+conversion+rate+saas), checked 2026-10-11.
+- [Agents for Data calculator](https://www.agentsfordata.com/saas/trial-conversion-rate), checked 2026-10-11.
+- [CalcBee calculator](https://calcbee.com/calculators/business/saas/trial-conversion-rate/), checked 2026-10-11.
+- [Right Left Agency calculator](https://rightleftagency.com/saas-free-trial-conversion-calculator/), checked 2026-10-11.
+- [Kalkulero calculator](https://kalkulero.com/free-trial-conversion-calculator/), checked 2026-10-11.
+- [SaaSPriceLab calculator](https://www.saaspricelab.com/saas-metrics-calculators/conversion-revenue), checked 2026-10-11.
+- [VentriTools calculator](https://ventritools.com/tools/saas/free-trial-conversion-calculator/), checked 2026-10-11.
+- [ChartMogul SaaS Conversion Report](https://chartmogul.com/reports/saas-conversion-report/), published February 2026; checked 2026-10-11.
+- [ChartMogul report on what improves conversion](https://chartmogul.com/reports/saas-conversion-report-2/), published March 18, 2026; checked 2026-10-11.
+- [ChartMogul Trial-to-Paid Conversions help article](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate), checked 2026-10-11.
+- [ChartMogul SaaS Go-To-Market Report](https://chartmogul.com/reports/saas-go-to-market-report/), published June 11, 2025; benchmarks cover Q1 2024–Q1 2025; checked 2026-10-11.
+- [First Page Sage trial conversion benchmarks](https://firstpagesage.com/seo-blog/saas-free-trial-conversion-rate-benchmarks/), published September 5, 2025; data covers Q1 2022–Q3 2025; checked 2026-10-11.
+- [Recurly State of Subscriptions: The acquisition chapter](https://recurly.com/resources/report/state-of-subscriptions-acquisition/), underlying trial data covers January–August 2022; checked 2026-10-11.
+- [Paddle developer docs on trials](https://developer.paddle.com/concepts/subscriptions/trials/), checked 2026-10-11.
+- [Reddit r/SaaS conversion question](https://www.reddit.com/r/SaaS/comments/1rfdj8o/how_many_of_your_trial_users_ended_up_becoming/), posted February 26, 2026; checked 2026-10-11.
+- [Reddit r/SaaS 71.43% trial-to-paid discussion](https://www.reddit.com/r/SaaS/comments/1tnrbul/we_just_hit_7143_trialtopaid_conversion_rate/), posted May 26, 2026; checked 2026-10-11.
+- [Reddit r/B2BSaaS card-required conversion question](https://www.reddit.com/r/B2BSaaS/comments/1ssivq2/cc_required_trial_paid_conversion_rates_for_b2b/), posted April 22, 2026; checked 2026-10-11.
+- [Reddit r/SaaS 300 trials and 17 conversions](https://www.reddit.com/r/SaaS/comments/1nocjgp/300_trial_signups_17_conversions_the_real_reason/), posted September 23, 2025; checked 2026-10-11.
diff --git a/content_docs/free-trial-conversion-calculator/tool-spec.md b/content_docs/free-trial-conversion-calculator/tool-spec.md
index b677c155..13e88de1 100644
--- a/content_docs/free-trial-conversion-calculator/tool-spec.md
+++ b/content_docs/free-trial-conversion-calculator/tool-spec.md
@@ -4,95 +4,135 @@ Route: `/free-trial-conversion-calculator`
 
 Research: [research.md](research.md)
 
-## Why people will choose this tool
+## People and questions
+
+- Most users are: SaaS founders with one trial cohort in a billing dashboard or spreadsheet. They come with two counts: how many started a trial, and how many of them paid. They know offhand whether people enter a card to start.
+- Their top questions:
+  - "What percentage of trial users paid?"
+  - "Is 3 out of 160 bad?"
+  - "How much more MRR would 5% or 10% bring?"
+- Basic answers them with: trial type (`No card`, `Card upfront`, `Free plan`), trial starts, and paid. That's enough for the rate, how sure it is at this sample size, and where it sits next to the one published range that measures the same thing for that trial type.
+- Advanced holds, for growth leads and founders who track more than two counts:
+  - **Follow-up window and cohort age**, because a cohort that hasn't had the full window yet understates its final rate. ChartMogul's rates change after the signup month, and no competitor marks a young cohort. The old tool had both.
+  - **Activated trials**, for growth leads who ask where the funnel loses people. Right Left and Kalkulero both have it, and it splits one rate into two places to work on.
+  - **Revenue**: currency, monthly plan price, annual plan price, and how many paid accounts chose annual. All six competitors model revenue, and "how much MRR" is a top question. The old tool had the monthly and annual split.
+  - **Target conversion**, for "how much more would 10% bring". VentriTools and CalcBee have it. The result adds the extra paid accounts and extra MRR.
+  - **Other cohorts**, up to 12, each with a name, starts, paid, and age. Pros ask whether the rate holds by month, channel, plan, or trial type. The old tool had a cohort list and a combined rate that leaves young cohorts out.
+- Left out:
+  - **Retention, churn, CAC, and LTV.** A first payment isn't a kept customer, and modeling churn here would make one rate look like lifetime value. `/customer-churn-calculator`, `/customer-acquisition-cost-calculator`, and `/customer-lifetime-value-calculator` do those jobs with the inputs they need.
+  - **Visitor-to-trial conversion and ad budget** (Kalkulero). It's a different funnel step with different counts, and it would turn this into a marketing planner.
+  - **A health score or grade.** Niches differ, and the research shows every competitor's grade is unsourced or contradicts its own math.
+  - **Trial length as an input.** It doesn't change the rate. The follow-up window is what changes the answer, and it's in Advanced.
+- Example values it opens with: `No card`, 500 trial starts, 40 paid. That's 8%, between ChartMogul's no-card median (4 to 6%) and top quarter (10 to 15%), so the first comparison doesn't flatter or alarm. Competitors open on similar sizes (500 at Agents for Data and SaaSPriceLab).
+- Published comparison: yes, for all three types. ChartMogul's January 2026 survey gives median and top-quarter bands for no-card trials, card-upfront trials, and free plans with a regular signup, for paid within six months. It's the only source that splits by trial type with a stated window. First Page Sage has no fixed window, Recurly counts subscriptions across consumer sites, and ChartMogul's 3% help-center median has no sample or window, so they go in the article, not the result. The research missed the free plan bands; the writing round found them in the same report and added them. The ranges count paid within six months, so they show only when the follow-up window is 180 to 184 days, or isn't set. With no window, the band labels name the six months, so the reader sees what they measure. Any other window shows no range and says so.
+- Domain limits:
+  - Paid can't exceed trial starts in one cohort. That's an error, never a clamp or a rate above 100%.
+  - Zero starts has no rate. The answer reads `—` with `No trial starts`, not 0%.
+  - A rate under 0.01% shows `Under 0.01%`, not `0%`.
+  - A cohort younger than its window is `Provisional`, with the days left. Its rate can still rise.
+  - A target at or below the current rate adds 0 paid accounts. It never shows a negative.
 
-The searcher wants to know what share of the people who started a free trial, or signed up for a free plan, went on to pay. They also want to know if that number is any good. Usually they're deciding whether to change the trial: card or no card, length, or onboarding.
+## Why people will choose this tool
 
-Where current results fail them (see the research's competitor reviews):
+The searcher is deciding whether their trial is working, and usually whether to change it: card or no card, onboarding, or pricing. Where the top results fail them:
 
-- They take "starts" and "paid" from any period. Nothing ties the paid count to the same start cohort or a fixed follow-up window, so a calendar-month ratio passes as a conversion rate.
-- None of them tells you when a cohort is too young to judge. A recent cohort looks worse than it will end up.
-- Most accept impossible counts. 0 starts with 1 paid gives 100%. 101 paid of 100 gives 101% and a perfect score. Negative starts are accepted.
-- No-card trials, card-upfront trials, and free plans get mixed together or are labeled with bare "opt-in" and "opt-out".
-- Revenue outputs call non-converters "lost revenue", round 0.5 expected customers up to a whole person, or skip annual plan normalization.
-- Benchmarks are unsourced bands or a made-up health score.
+- Most accept impossible counts. 120 paid from 100 starts gives 120% and a "Top 25%" label at Agents for Data, CalcBee, and VentriTools. Kalkulero quietly clamps it. Right Left rejects it but leaves the old result on screen as if it were accepted.
+- They grade one number against unsourced bands, with no trial type or window, and SaaSPriceLab hides its bands behind a paid report.
+- None says how much to trust a rate from 42 trials, which is exactly what r/SaaS commenters argue about.
+- None marks a young cohort, so a recent month looks worse than it will end up.
+- Revenue outputs call MRR × 12 "annual revenue" and don't say it's a run rate.
 
 What this tool does better:
 
-1. It measures one start cohort against itself: starts, and paid within a named window counted from each person's own start.
-2. It shows a visible **Complete** or **Provisional** state from the cohort's age, with the days left.
-3. An optional list of cohorts compares months at the same age. The combined rate uses complete cohorts only.
-4. It has three plain-word models: free trial with no card, free trial with a card upfront, and free plan.
-5. It rejects impossible counts beside the field and never clamps. Zero starts gives "Not available", not 0% or 100%.
-6. Optional new MRR uses one average monthly amount, or monthly and annual plans with annual ÷ 12. It leaves out one-time fees, shows ARR only as a run rate, and never mentions "lost" revenue.
-7. Published figures for the chosen model come with source, date, population, and method. They're directional, with no score or grade, and the page says plainly that indie SaaS figures by model are unknown.
+1. The answer comes with its counts, `40 of 500 trial starts paid`, so you can check you divided the right numbers.
+2. A likely range at your sample size, drawn on the same scale as the published range. 30 of 42 is 71%, but anywhere from about 56% to 83% is plausible.
+3. One dated, named comparison that matches your trial type and window, shown as position only. No grades, no colors that judge.
+4. Impossible counts get a field error, and the last good result steps back instead of pretending.
+5. `Provisional, 18 days left` when the cohort is too young, and a combined rate across cohorts that leaves young ones out.
+6. New MRR and ARR run rate labeled for what they are, with annual plans counted as a twelfth a month.
 
 ## Product
 
 ### Promise and scope
 
-- **User:** an indie hacker or solo SaaS founder with a free trial or free plan, reading counts from Stripe, Paddle, Lemon Squeezy, or their own database.
-- **Job:** find the trial-to-paid (or free-to-paid) rate for one or more start cohorts, know whether each one is old enough to trust, and optionally see the new MRR those customers added.
-- **Answer:** a cohort conversion rate with its window and maturity state. Optionally, a per-cohort table and new MRR with ARR run rate.
-
-In scope:
-
-- Three models: `trialNoCard`, `trialCardRequired`, `freemium`. The math is the same for all three. The model changes the count labels and the published figures shown.
-- One follow-up window in days, shared by every cohort, so cohorts are compared at the same age.
-- 1 to 12 cohorts.
-- New MRR from paid customers, by one average monthly amount or a monthly and annual split.
-- Published figures for the selected model, from the research's dated sources.
-
-Out of scope: forecasts or "what if the rate improves" scenarios, expected-customer estimates, churn, retention, CAC, LTV, cash collected, revenue recognition, activation, funnel attribution, rolling-window rates like Stripe's, CSV import, and saving or sharing state. Link out to `/mrr-calculator`, `/customer-acquisition-cost-calculator`, and `/customer-churn-calculator` for those jobs.
+- **Primary user:** a SaaS founder with counts for one trial cohort.
+- **Main job:** find the share of trial starts that paid, see how sure that is, and see it next to a matching published range.
+- **Delivered answer:** the conversion rate with its counts, a likely range, a 100-unit picture, and, from Advanced, maturity, an activation funnel, new MRR, a target scenario, and a cohort comparison.
+- **Launch scope:** everything in this spec. One calculation runs in the browser. No network, storage, or account.
+- **Exclusions:** see "Left out" above. Also no CSV import, no Stripe connection, no rolling-window rates like Stripe's 30-day metric, and no expected-customer fractions.
 
 ### Technical contract
 
 **Definitions**
 
-- A cohort is a group of accounts that started a trial (or free plan) in one period, such as a calendar month. Each account counts once.
-- Paid means the account's first payment succeeded within the window, counted from that account's own start. A card on file, a pending payment, or a failed first invoice isn't paid. The engine can't check this. It takes the count as given, and the interface and article explain it.
-- The follow-up window `N` is a whole number of days.
-- Cohort age is the number of days from the cohort's newest start to the day the paid count was taken.
-
-**Formulas**, all exact (bigint fractions, no floats):
-
-- Rate = paid ÷ starts × 100.
-- Didn't pay within the window = starts − paid. Never label this "lost".
-- Maturity: `complete` when age ≥ `N`. Otherwise `maturing`, with `daysLeft = N − age`.
-- Combined rate, with one or more cohorts:
-  - If the complete cohorts have more than 0 starts in total, use only complete cohorts: `basis: "complete"`, `status: "complete"`.
-  - Otherwise use every cohort: `basis: "all"`. The status is `provisional` if any cohort is maturing, else `complete`.
-  - Combined rate = Σ paid ÷ Σ starts over the basis cohorts. It is not an average of the cohort rates.
-  - If Σ starts is 0, the rate is `notAvailable`.
-- New MRR, when on. "Paid customers" means Σ paid across **all** listed cohorts, maturing ones included, because those payments already happened.
-  - `average`: MRR = paid customers × average monthly amount.
-  - `split`: monthly-plan customers + annual-plan customers must equal paid customers. MRR = monthly customers × average monthly price + annual customers × average annual price ÷ 12.
-  - ARR run rate = exact MRR × 12. Compute it from the exact MRR, not the rounded one.
-
-**Rounding**
-
-- Rates go to hundredths of a percent, half away from zero, through `roundExact` (`lib/saas-economics/unit-economics.ts`). Return `isRounded`. Return `roundedToZero` when paid > 0 but the rounded value is 0. The interface then shows `Under 0.01%`.
-- Money is in cents, half away from zero, with `isRounded`.
-- Counts are whole numbers and never rounded. The tool takes no fractional people and makes no expected-customer estimates.
-
-**Units and bounds**
-
-| Field | Parse | Range |
-| --- | --- | --- |
-| Starts, paid, monthly and annual customers | `parseWholeNumber` | 0 to 10,000,000 |
-| Window | `parseWholeNumber` | 1 to 730 days |
-| Cohort age | `parseWholeNumber` | 0 to 3,650 days |
-| Money | `parseMoneyCents` | 0 to `SAAS_ECONOMICS_MAX_MONEY_CENTS` (1,000,000,000.00) |
-| Cohort name | `parseOptionalLabel` | up to 40 characters, blank allowed |
-| Currency | `isSaasEconomicsCurrency` | the listed currencies |
-
-Strict text: no signs, commas, spaces inside, exponents, or currency symbols. This matches the sibling engines.
-
-**Privacy and security:** the tool runs only in the browser. No network calls, no storage, and no URL state, because these are private business numbers. Labels render as text, never HTML.
+- A cohort is a group of accounts that started a trial, or signed up for a free plan, in one period. Each account counts once.
+- Paid means the account's first payment went through. The engine takes the count as given. The hint and article say a card on file isn't a payment.
+- The follow-up window is the days each account had to pay, counted from its own start.
+- Cohort age is the days from the cohort's last start to the day the paid count was taken.
+- Activated means the start reached the person's own activation event. The funnel is nested: activated includes everyone who paid.
+
+**Inputs, parsing, and bounds**
+
+Every value arrives as a string from a text field. Strict parsing, as in the sibling SaaS engines: no signs, commas, spaces inside, exponents, or currency symbols. Leading and trailing spaces are trimmed.
+
+| Field | Parser | Range | Empty means |
+| --- | --- | --- | --- |
+| `trialType` | one of `noCard`, `cardUpfront`, `freePlan` | | error |
+| `starts`, `paid` | `parseWholeNumber` | 0 to 10,000,000 | error |
+| `windowDays` | `parseWholeNumber` | 1 to 730 | no window: maturity unknown |
+| `ageDays` | `parseWholeNumber` | 0 to 3,650 | maturity unknown |
+| `activated` | `parseWholeNumber` | 0 to 10,000,000 | no funnel |
+| `targetRate` | `parsePercentHundredths` | 0.01 to 100 | no target |
+| `currency` | `isSaasEconomicsCurrency` | `USD`, `EUR`, `GBP`, `INR`, `CAD`, `AUD` | `USD` |
+| `monthlyPrice`, `annualPrice` | `parseMoneyCents` | 0 to `SAAS_ECONOMICS_MAX_MONEY_CENTS` | not used |
+| `annualAccounts` | `parseWholeNumber` | 0 to 10,000,000 | see revenue rules |
+| cohort `name` | `parseOptionalLabel` | up to 40 characters | `Cohort 2`, `Cohort 3`, by list position + 1 |
+| cohort `starts`, `paid` | `parseWholeNumber` | 0 to 10,000,000 | error, unless the whole row is blank |
+| cohort `ageDays` | `parseWholeNumber` | 0 to 3,650 | maturity unknown |
+| `cohorts` | array | up to 12 rows | no comparison |
+
+A cohort row with every field blank is ignored. It isn't an error.
+
+**Formulas.** Exact bigint fractions through `lib/saas-economics/unit-economics.ts`, except the likely range.
+
+- Rate = paid ÷ starts × 100. Rounded to hundredths of a percent, half away from zero. `roundedToZero` when paid > 0 and the rounded value is 0.
+- Not paid = starts − paid.
+- Trials per paying customer = starts ÷ paid, rounded to tenths. None when paid is 0.
+- Likely range: the 95% Wilson score interval, z = 1.96, in floating point. Low rounds down and high rounds up to hundredths of a percent, so the range always contains the true interval. None when starts is 0.
+  - `p = paid / starts`, `n = starts`, `d = 1 + z²/n`, `c = p + z²/(2n)`, `s = z × √(p(1 − p)/n + z²/(4n²))`, low = (c − s) / d, high = (c + s) / d.
+- Maturity, when both window and age are set: `complete` when age ≥ window, otherwise `provisional` with `daysLeft = window − age`. Otherwise `unknown`.
+- Activation, when `activated` is set: activation rate = activated ÷ starts. Activated to paid = paid ÷ activated. Each is a rate as above, or none when its denominator is 0.
+- Revenue, when either price is set. The per-account monthly amount:
+  - Monthly price only: every paid account at the monthly price.
+  - Annual price only: every paid account at annual price ÷ 12.
+  - Both: `annualAccounts` on annual price ÷ 12, the rest on the monthly price.
+  - New MRR = the sum, exact, then rounded to cents half away from zero. ARR run rate = exact MRR × 12, rounded to cents. Never round MRR first.
+- Target, when `targetRate` is set:
+  - Paid at target = ceil(target ÷ 100 × starts). Whole accounts, rounded up, because reaching the target takes a whole extra account. 9 of 99 is 9.09%, and 10% needs 10 paid, so 1 extra.
+  - Extra paid = max(0, paid at target − paid).
+  - Extra MRR, when revenue is set = extra paid × MRR per paid account, rounded to cents. MRR per paid account = exact MRR ÷ paid when paid > 0. When paid is 0, it's the monthly price if set, else annual price ÷ 12.
+- Cohorts, when at least one row is filled. The Basic cohort is index 0, named `This cohort`. Each row gets its own rate, maturity (the shared window with its own age), and likely range.
+  - Combined: if the non-provisional cohorts have more than 0 starts in total, use only those: `basis: "settled"`. Otherwise use all: `basis: "all"`.
+  - Combined rate = Σ paid ÷ Σ starts over the basis cohorts. It is not an average of the row rates.
+  - `status` is `provisional` if any basis cohort is provisional, else `complete` if every basis cohort is complete, else `unknown`.
+
+**Invalid, unknown, and partial results**
+
+- Basic errors (trial type, starts, paid, paid > starts) make the whole calculation invalid. No values come back.
+- Advanced errors hide only the part they feed. The calculation stays valid, that part is `null`, and its errors come back alongside:
+  - Window or age error: `maturity` is `unknown`, and cohort maturities are `unknown`.
+  - Activated error: `activation` is `null`.
+  - Revenue error: `revenue` is `null`, and `target.extraMrrCents` is `null`.
+  - Target error: `target` is `null`.
+  - Any cohort row error: `cohorts` is `null`.
+- An age, on the Basic cohort or any row, with no window is an error on `windowDays`.
+- A window alone is valid. It names the window in the result, and maturity stays `unknown`.
+
+**Privacy and security:** the calculation runs in the browser. No network calls and no storage. The URL holds inputs only after the person presses `Copy link`. Cohort names render as text, never HTML.
 
 ### Backend contract
 
-Same runtime rules as the other SaaS economics engines: strip-types safe, no enums or namespaces, explicit `.ts` imports, and no DOM, network, time, or randomness. Reuse `lib/saas-economics/shared.ts` (`parseWholeNumber`, `parseMoneyCents`, `parseOptionalLabel`, `isSaasEconomicsCurrency`, `SAAS_ECONOMICS_MAX_MONEY_CENTS`) and `lib/saas-economics/unit-economics.ts` (`exactFraction`, `addExact`, `multiplyExact`, `divideExact`, `roundExact`, `isWholeAtScale`) unchanged. No API route, script, dataset, or migration.
+Same runtime rules as the other SaaS engines: strip-types safe, no enums or namespaces, explicit `.ts` imports, and no DOM, network, time, or randomness. Reuse `lib/saas-economics/shared.ts` and `lib/saas-economics/unit-economics.ts` unchanged. No API route, script, dataset, or migration.
 
 #### `lib/free-trial-conversion-calculator/engine.ts`
 
@@ -100,215 +140,272 @@ Same runtime rules as the other SaaS economics engines: strip-types safe, no enu
 import { type SaasEconomicsCurrency } from "../saas-economics/shared.ts";
 import { type ExactFraction } from "../saas-economics/unit-economics.ts";
 
-export const TRIAL_MODELS = ["trialNoCard", "trialCardRequired", "freemium"] as const;
-export type TrialModel = (typeof TRIAL_MODELS)[number];
-export const TRIAL_MRR_METHODS = ["average", "split"] as const;
-export type TrialMrrMethod = (typeof TRIAL_MRR_METHODS)[number];
+export const TRIAL_TYPES = ["noCard", "cardUpfront", "freePlan"] as const;
+export type TrialType = (typeof TRIAL_TYPES)[number];
 export const TRIAL_MAX_COHORTS = 12;
 
-export type TrialCohortInput = { label: string; starts: string; paid: string; ageDays: string };
-export type TrialCohortField = keyof TrialCohortInput;
-export type FreeTrialConversionInput = {
-  model: string;
+export type TrialCohortRowInput = { id: string; name: string; starts: string; paid: string; ageDays: string };
+export type FreeTrialInput = {
+  trialType: string;
+  starts: string;
+  paid: string;
   windowDays: string;
-  cohorts: TrialCohortInput[];
-  includeMrr: boolean;
-  currency: string;          // ignored when includeMrr is false
-  mrrMethod: string;         // ignored when includeMrr is false
-  averageMonthly: string;    // used by "average"
-  monthlyCustomers: string;  // used by "split"
+  ageDays: string;
+  activated: string;
+  targetRate: string;
+  currency: string;
   monthlyPrice: string;
-  annualCustomers: string;
   annualPrice: string;
+  annualAccounts: string;
+  cohorts: TrialCohortRowInput[];
 };
 
+/** The example the tool opens with and Reset returns to. */
+export const FREE_TRIAL_EXAMPLE_INPUT: FreeTrialInput; // noCard, 500, 40, every other field "", currency "USD", cohorts []
+
 export type TrialFieldKey =
-  | "form" | "model" | "windowDays" | "cohorts"
-  | `cohorts.${number}.${TrialCohortField}`
-  | "currency" | "mrrMethod" | "averageMonthly"
-  | "monthlyCustomers" | "monthlyPrice" | "annualCustomers" | "annualPrice";
+  | "form" | "trialType" | "starts" | "paid"
+  | "windowDays" | "ageDays" | "activated" | "targetRate"
+  | "currency" | "monthlyPrice" | "annualPrice" | "annualAccounts"
+  | "cohorts" | `cohorts.${number}.${"name" | "starts" | "paid" | "ageDays"}`;
+// Row keys use the row's position in the input array, blank rows included.
+
+export type TrialRate =
+  | { kind: "rate"; hundredths: bigint; exact: ExactFraction; isRounded: boolean; roundedToZero: boolean }
+  | { kind: "none" };
+// hundredths = percent × 100. 800n is 8%.
 
-export type TrialConversionRate =
-  | { kind: "finite"; hundredths: bigint; exact: ExactFraction; isRounded: boolean; roundedToZero: boolean }
-  | { kind: "notAvailable"; reason: "noStarts" };
-// hundredths = percent × 100. 1322n means 13.22%. exact is the percent as a fraction.
+export type TrialLikelyRange = { lowHundredths: bigint; highHundredths: bigint } | null;
 
 export type TrialMaturity =
   | { status: "complete" }
-  | { status: "maturing"; daysLeft: bigint };
+  | { status: "provisional"; daysLeft: bigint }
+  | { status: "unknown" };
 
 export type TrialCohortResult = {
-  index: number;             // position in the input
-  label: string;             // trimmed; "" when blank. The UI shows "Cohort 1" etc.
+  inputIndex: number | null; // null for the Basic cohort, else the row's index in input.cohorts
+  name: string;              // "This cohort", the trimmed name, or "Cohort N"
   starts: bigint;
   paid: bigint;
-  notPaid: bigint;           // starts - paid
-  ageDays: bigint;
-  rate: TrialConversionRate;
+  rate: TrialRate;
+  likely: TrialLikelyRange;
   maturity: TrialMaturity;
 };
 
-export type TrialCombined = {
-  basis: "complete" | "all";
-  status: "complete" | "provisional";
-  includedIndexes: number[]; // cohorts in the basis, in input order
-  excludedMaturing: number;  // maturing cohorts left out (0 when basis is "all")
-  starts: bigint;            // over the basis
+export type FreeTrialValues = {
+  trialType: TrialType;
+  starts: bigint;
   paid: bigint;
   notPaid: bigint;
-  rate: TrialConversionRate;
-};
-
-export type TrialNewMrr = {
-  currency: SaasEconomicsCurrency;
-  method: TrialMrrMethod;
-  paidCustomers: bigint;               // across all cohorts
-  averageMonthlyCents: bigint | null;  // "average" only
-  monthlyPlan: { customers: bigint; priceCents: bigint; mrrCents: bigint } | null; // "split" only, exact
-  annualPlan: { customers: bigint; annualPriceCents: bigint; mrrCents: bigint; isRounded: boolean } | null; // "split" only, ÷12 rounded
-  mrrCents: bigint;                    // rounded from the exact total
-  mrrIsRounded: boolean;
-  runRateArrCents: bigint;             // exact MRR × 12, rounded (always whole in practice)
+  rate: TrialRate;
+  likely: TrialLikelyRange;
+  trialsPerPaidTenths: bigint | null;
+  windowDays: bigint | null;
+  maturity: TrialMaturity;
+  activation: { activated: bigint; activationRate: TrialRate; activatedToPaid: TrialRate } | null;
+  revenue: {
+    currency: SaasEconomicsCurrency;
+    monthlyAccounts: bigint;
+    annualAccounts: bigint;
+    mrrCents: bigint;
+    mrrIsRounded: boolean;
+    arrRunRateCents: bigint;
+  } | null;
+  target: {
+    hundredths: bigint;
+    paidAtTarget: bigint;
+    extraPaid: bigint;
+    extraMrrCents: bigint | null; // null when revenue isn't set or has an error
+  } | null;
+  cohorts: {
+    rows: TrialCohortResult[]; // Basic cohort first, then filled rows in input order
+    combined: {
+      basis: "settled" | "all";
+      status: "complete" | "provisional" | "unknown";
+      leftOut: number;          // provisional cohorts left out (0 when basis is "all")
+      starts: bigint;
+      paid: bigint;
+      rate: TrialRate;
+    };
+  } | null;
 };
 
-export type FreeTrialConversionValues = {
-  model: TrialModel;
-  windowDays: bigint;
-  cohorts: TrialCohortResult[];
-  combined: TrialCombined;
-  newMrr: TrialNewMrr | null;
-};
+export type FreeTrialErrors = Partial<Record<TrialFieldKey, string>>;
 
-export type FreeTrialConversionErrors = Partial<Record<TrialFieldKey, string>>;
+export type FreeTrialCalculation =
+  | { status: "valid"; values: FreeTrialValues; errors: FreeTrialErrors } // errors only for Advanced parts
+  | { status: "invalid"; values: null; errors: FreeTrialErrors };
 
-export type FreeTrialConversionCalculation =
-  | { status: "valid"; values: FreeTrialConversionValues; errors: Record<string, never> }
-  | { status: "invalid"; values: null; errors: FreeTrialConversionErrors };
+export function calculateFreeTrialConversion(input: unknown): FreeTrialCalculation;
 
-export function calculateFreeTrialConversion(input: unknown): FreeTrialConversionCalculation;
+/** Share link values. Empty fields stay out. */
+export function freeTrialShareParams(input: FreeTrialInput): Record<string, string>;
+/** Rebuilds the input from a shared link. Missing keys fall back to the example for Basic fields and "" for the rest. Bad values pass through as text, so the engine reports them as field errors. */
+export function freeTrialInputFromQuery(get: (key: string) => string): FreeTrialInput;
 ```
 
-The engine collects every error in one pass and never throws for user input. A non-object input, a non-array `cohorts`, a non-object cohort, or a non-boolean `includeMrr` gives `errors.form`. MRR fields are checked only when `includeMrr` is true, and only the active method's fields.
+The engine collects every error in one pass and never throws for user input. A non-object input or a non-array `cohorts` gives `errors.form` and `status: "invalid"`.
 
-Error messages. The engine owns these strings, and the writing pass may reword them:
+Share link keys: `type`, `starts`, `paid`, `window`, `age`, `activated`, `target`, `currency`, `monthly`, `annual`, `annualPaid`, and `cohorts`. `cohorts` holds the filled rows as `name~starts~paid~age`, joined by `|`. `~` and `|` are removed from names. `currency` goes in only when a price is set. More than 12 rows in a link keeps the first 12. Row IDs are made fresh on read, such as `shared-0`.
+
+Error messages. The engine owns these, and the writing pass may reword them:
 
 | Case | Key | Message |
 | --- | --- | --- |
 | Bad payload | `form` | `Something in the form is out of date. Reset and try again.` |
-| Unknown model | `model` | `Choose one of the listed options.` |
-| Window blank | `windowDays` | `Enter the follow-up window in days.` |
+| Unknown trial type, currency | that key | `Choose one of the listed options.` |
+| Starts or paid blank | the field | `Enter a count. Use 0 if there were none.` |
+| Any count starts with `-` | the field | `Counts can't be negative.` |
+| Any count in another bad format, such as `2.5`, `1,180`, `1e3` | the field | `Use a whole number with no commas or decimals.` |
+| Any count above 10,000,000 | the field | `Enter a number up to 10,000,000.` |
+| Paid > starts | `paid` | `Paid can't be more than trial starts. Count only accounts from this cohort.` |
 | Window bad or out of range | `windowDays` | `Enter whole days from 1 to 730.` |
-| 0 cohorts | `cohorts` | `Add at least one cohort.` |
-| More than 12 cohorts | `cohorts` | `Use up to 12 cohorts.` |
-| Count starts with `-` | the field | `Counts can't be negative.` |
-| Count blank | the field | `Enter a count. Use 0 if there were none.` |
-| Count other bad format, such as `2.5`, `1,180`, `1e3` | the field | `Use a whole number with no commas or decimals.` |
-| Count above 10,000,000 | the field | `Enter a number up to 10,000,000.` |
-| Paid > starts | `cohorts.i.paid` | `Paid can't be more than starts. Count only accounts from this cohort.` |
-| Age blank | `cohorts.i.ageDays` | `Enter the days since the newest start.` |
-| Age bad or out of range | `cohorts.i.ageDays` | `Enter whole days from 0 to 3,650.` |
-| Label too long or has control characters | `cohorts.i.label` | `Use a name up to 40 characters on one line.` |
-| Unknown currency or method | that key | `Choose one of the listed options.` |
-| Money blank | the field | `Enter an amount.` |
+| Age, here or in any row, with no window | `windowDays` | `Enter the follow-up window to compare cohort age against.` |
+| Age bad or out of range | the field | `Enter whole days from 0 to 3,650.` |
+| Activated > starts | `activated` | `Activated can't be more than trial starts.` |
+| Paid > activated | `activated` | `Activated must include everyone who paid, so it can't be less than <paid>.` |
+| Target bad or out of range | `targetRate` | `Enter a rate from 0.01 to 100%.` |
 | Money bad format | the field | `Use digits with up to two decimals. No signs, commas, or currency symbols.` |
 | Money above max | the field | `Enter an amount up to 1,000,000,000.00.` |
-| Split doesn't add up | `monthlyCustomers` | `Monthly and annual customers must add up to <paid>, the paid customers above.` For example, `…add up to 156, the paid customers above.` Only when every count parsed. |
-
-Negative numbers get their own message because the research shows competitors accepting them. Zero starts with zero paid is valid and gives `notAvailable`. Zero starts with paid > 0 is the "paid > starts" error.
-
-#### Published figures
-
-No engine involvement. The frontend keeps them as a typed constant in the route folder (see Ownership), copied from the research's benchmark table. They're display content, not calculation.
+| `annualAccounts` set without both prices | `annualAccounts` | `Enter a monthly and an annual price to split paid accounts by plan.` |
+| Both prices set, `annualAccounts` blank | `annualAccounts` | `Enter how many paid accounts are on annual plans.` |
+| `annualAccounts` > paid | `annualAccounts` | `Annual accounts can't be more than <paid>, the paid count.` |
+| Row with starts or paid blank, other fields filled | the field | `Enter a count. Use 0 if there were none.` |
+| Row paid > row starts | `cohorts.i.paid` | `Paid can't be more than starts in this cohort.` |
+| Row name too long or has control characters | `cohorts.i.name` | `Use a name up to 40 characters on one line.` |
+| More than 12 rows | `cohorts` | `Use up to 12 other cohorts.` |
 
 ### Known examples
 
-Calculated by hand. Use `trialNoCard` with MRR off unless stated.
+Calculated by hand. `noCard`, Advanced empty, unless stated. Likely ranges were checked with the Wilson formula above.
 
 | Inputs | Expected |
 | --- | --- |
-| Window `30`. One cohort: starts `1180`, paid `156`, age `45` | Rate `1322n` (13.2203…%), `isRounded: true`. `notPaid: 1024n`. Maturity `complete`. Combined: the same rate, `basis: "complete"`, `status: "complete"`. (Calclet's 13.22%.) |
-| As above, MRR on, USD, `average`, `49` | Paid customers `156n`. MRR `764400n` ($7,644.00), not rounded. ARR run rate `9172800n` ($91,728.00). |
-| Window `30`. One cohort: starts `100`, paid `20`, age `30` | `2000n` (20.00%). Age = window gives `complete`. The article contrasts this with the 6% calendar-month ratio (6 of the 100 paid in August). The tool doesn't compute that ratio. |
-| Window `14`. One cohort: starts `200`, paid `30`, age `10` | `1500n`. Maturity `maturing`, `daysLeft: 4n`. Combined `basis: "all"`, `status: "provisional"`. |
-| Window `30`. Cohorts: Jul `400`/`60`/age `75`; Aug `500`/`70`/age `45`; Sep `450`/`30`/age `10` | Rows: `1500n`; `1400n`; `667n` (6.6667%) `maturing`, `daysLeft: 20n`. Combined: `basis: "complete"`, `includedIndexes: [0, 1]`, `excludedMaturing: 1`, 130 ÷ 900 gives `1444n` (14.444…%). Not the mean of the row rates (14.50%). |
-| Same three cohorts, MRR on, `average`, `20` | Paid customers `160n` (Sep included). MRR `320000n`. |
-| Window `30`. Cohorts `100`/`5`/age `5` and `200`/`10`/age `12` | Rows `500n`, `500n`, both maturing. Combined `basis: "all"`, `provisional`, `500n` (5.00%) from 15 ÷ 300. Corrected by coordinator after the backend check. |
-| Window `30`. Cohorts `0`/`0`/age `40` and `100`/`10`/age `5` | Row 1 `notAvailable`, `complete`. The complete starts total is 0, so the basis is `all`: `provisional`, 10 ÷ 100 gives `1000n`. |
-| One cohort `0`/`0`/age `40` | Valid. Rate `notAvailable`, shown as `Not available`. Combined `notAvailable`. |
-| One cohort `3`/`1` and `3`/`2` (separate runs), age ≥ window | `3333n` and `6667n`, both `isRounded: true`. |
-| One cohort `1`/`1` | `10000n` (100.00%), not rounded. |
-| One cohort `2000000`/`1` | `0n`, `roundedToZero: true` (exact 0.00005%). Shown as `Under 0.01%`. |
-| Paid `4` total. MRR `split`: monthly `3` at `10`, annual `1` at `100` | Monthly plan `3000n`. Annual plan `833n` (exact 833.33…), `isRounded: true`. MRR `3833n` ($38.33), `mrrIsRounded: true`. ARR run rate `46000n` ($460.00), from the exact MRR. Rounding first would give $459.96. |
-| Paid `156`. MRR `split`: monthly `100`, annual `50` | Error on `monthlyCustomers`: `…must add up to 156…`. |
-| Paid `0`. MRR `average` `49` | MRR `0n`, valid. |
-| `freemium`. Window `180`. One cohort `5000`/`150`/age `200` | `300n` (3.00%), `complete`. Same math and only the model differs. |
-| Maximums: starts `10000000`, paid `10000000`, window `730`, age `3650`; MRR `average` `1000000000` | `10000n`. MRR `1000000000000000000n` cents ($10,000,000,000,000,000.00). ARR run rate twelve times that. No overflow, because everything is bigint. |
-| Invalid: starts `100`, paid `101` | Error on `cohorts.0.paid`. No values. (Agents for Data and Technotize case.) |
-| Invalid: starts `0`, paid `1` | Error on `cohorts.0.paid`. (Calclet's 100% case.) |
-| Invalid: starts `-5` | `Counts can't be negative.` (VentriTools case.) |
-| Invalid: starts `2.5`, `1,180`, `1e3`, blank; window `0`, `731`, blank; age blank, `-1`; label of 41 characters; 0 cohorts; 13 cohorts; model `optIn`; MRR on with currency `JPY`, method `blend`, average `$49`, or annual price `-1` | A field-specific error for each, under the keys above. `status: "invalid"`. Several errors in one input all come back together. |
-| MRR off, with every MRR field blank or garbage | Valid. MRR fields aren't checked. |
+| The example: 500 starts, 40 paid | Rate `800n` (8%), not rounded. Not paid `460n`. Trials per paying customer `125n` (12.5). Likely `592n` to `1072n` (exact 5.9298% to 10.7107%). Maturity `unknown`. Everything else `null`. |
+| 160 / 3 | `188n` (1.875%), `isRounded`. Likely `63n` to `537n` (0.6397% to 5.3671%). Trials per paying customer `533n` (53.3). |
+| 42 / 30 | `7143n` (71.428…%). Likely `5643n` to `8284n` (56.4325% to 82.8331%). Trials per paying customer `14n` (1.4). |
+| 1,180 / 156 | `1322n`. Likely `1140n` to `1528n`. |
+| 50 / 0 | `0n`, not `roundedToZero`. Likely `0n` to `714n` (7.1350%). Trials per paying customer `null`. |
+| 50 / 50 | `10000n`. Likely `9286n` to `10000n`. Trials per paying customer `10n` (1.0). |
+| 2,000,000 / 1 | `0n`, `roundedToZero: true` (exact 0.00005%). Likely `0n` to `1n`. Shown as `Under 0.01%`. |
+| 0 / 0 | Valid. Rate `none`, likely `null`, not paid `0n`, trials per paying customer `null`. |
+| 500 / 40, window `30`, age `45` | Maturity `complete`. |
+| 500 / 40, window `30`, age `30` | `complete`. Age equal to the window is complete. |
+| 500 / 40, window `30`, age `12` | `provisional`, `daysLeft: 18n`. |
+| 500 / 40, window `30` only | Valid. `windowDays: 30n`, maturity `unknown`. |
+| 500 / 40, activated `200` | Activation rate `4000n` (40%). Activated to paid `2000n` (20%). |
+| 500 / 0, activated `0` | Activation rate `0n`. Activated to paid `none`. |
+| 500 / 40, monthly `29` | 40 monthly accounts. MRR `116000n` ($1,160.00), not rounded. ARR run rate `1392000n` ($13,920.00). |
+| 500 / 40, annual `290` | 40 annual accounts. MRR `96667n` ($966.67, exact 966.666…), `mrrIsRounded`. ARR run rate `1160000n` ($11,600.00) from the exact MRR. |
+| 500 / 40, monthly `29`, annual `290`, annual accounts `10` | 30 monthly, 10 annual. MRR `111167n` ($1,111.67, exact 1,111.666…), `mrrIsRounded`. ARR run rate `1334000n` ($13,340.00). Rounding MRR first would give $13,340.04. |
+| 500 / 40, target `10` | Paid at target `50n`. Extra paid `10n`. Extra MRR `null`. |
+| 500 / 40, target `10`, monthly `29` | Extra MRR `29000n` ($290.00). |
+| 500 / 40, target `10`, monthly `29`, annual `290`, annual accounts `10` | Extra MRR = 10 × 1,111.666… ÷ 40 = 277.916… → `27792n` ($277.92). |
+| 333 / 20, target `7.5` | Paid at target = ceil(24.975) = `25n`. Extra paid `5n`. |
+| 99 / 9, target `10` | Paid at target = ceil(9.9) = `10n`. Extra paid `1n`. |
+| 500 / 40, target `5` | Paid at target `25n`. Extra paid `0n`, never negative. |
+| 500 / 0, target `10`, monthly `29` | Extra paid `50n`. Extra MRR `145000n` ($1,450.00), priced at the monthly price because paid is 0. |
+| 500 / 40, window `30`, age `45`. Rows: `Jul` 400 / 36 / age 75; `Sep` 450 / 18 / age 10 | Rows: This cohort `800n` complete; Jul `900n` complete; Sep `400n` provisional, `daysLeft: 20n`. Combined `basis: "settled"`, `status: "complete"`, `leftOut: 1`, 76 ÷ 900 → `844n` (8.444…%). Not the mean of the settled rows (8.5%). |
+| 500 / 40, window `30`, age `5`. Row: `Aug` 300 / 17 / age 8 | Both provisional. Combined `basis: "all"`, `status: "provisional"`, 57 ÷ 800 → `713n` (7.125%). |
+| 500 / 40, no window. Row: blank name, 300 / 17, no age | Row name `Cohort 2`, rate `567n`. Both `unknown`. Combined `basis: "settled"`, `status: "unknown"`, 57 ÷ 800 → `713n`. |
+| 500 / 40. Rows: one fully blank row | Valid. Blank row ignored. `cohorts` is `null`. |
+| Maximums: 10,000,000 / 10,000,000, monthly `1000000000`, target `100` | Rate `10000n`. MRR $10,000,000,000,000,000.00. No overflow. |
+| Invalid: starts `100`, paid `120` | `status: "invalid"`, error on `paid`. |
+| Invalid: starts `0`, paid `1` | Error on `paid`. |
+| Invalid: starts `-5`; `2.5`; `1,180`; `1e3`; blank | The count messages above, on `starts`. |
+| Partial: 500 / 40, activated `30` | Valid. Rate `800n` and the rest as normal. `activation: null`. Error on `activated`: `…can't be less than 40.` |
+| Partial: 500 / 40, age `20`, no window | Valid. Maturity `unknown`. Error on `windowDays`. |
+| Partial: 500 / 40, monthly `$29` | Valid. `revenue: null`. Error on `monthlyPrice`. |
+| Partial: 500 / 40, monthly `29`, annual accounts `5` | Valid. `revenue: null`. Error on `annualAccounts`. |
+| Partial: 500 / 40, row `Sep` 100 / 120 | Valid. `cohorts: null`. Error on `cohorts.0.paid`. |
+| Partial: target `0`, `101`, `abc` | Valid. `target: null`. Error on `targetRate`. |
+| Share round trip: the cohort example, with the Sep row named `Sep~\|26` | `freeTrialShareParams` gives `type=noCard`, `starts=500`, `paid=40`, `window=30`, `age=45`, and `cohorts=Jul~400~36~75\|Sep26~450~18~10`. No empty keys. Reading it back gives the same input, with the name `Sep26` and fresh row IDs. |
 
 ### Ownership
 
 Sol builds the backend:
 
 - `lib/free-trial-conversion-calculator/engine.ts`.
-- `tests/pages/free-trial-conversion-calculator/free-trial-conversion-calculator.test.mjs`, covering the examples above in the CAC test's style.
-- The development tool-page preview row, with a clearly marked placeholder title, when the coordinator asks.
+- `tests/pages/free-trial-conversion-calculator/free-trial-conversion-calculator.test.mjs`, covering the examples above in the style of the other SaaS engine tests.
+- The development tool-page row needs no change. It already exists.
 
 Opus builds the frontend:
 
-- `app/(site)/(tools)/(saas)/free-trial-conversion-calculator/page.tsx`, `layout.tsx`, `free-trial-conversion-calculator.tsx`, `free-trial-conversion-calculator.module.css`, and `published-figures.ts`, the typed benchmark constant.
-- Card art: `art/free-trial-conversion-calculator.spec.json`, `.svg`, and `.ts` through `$marker-art-draw`, a new `trialConversion` motif in `scripts/stack127/marker-art/figures.mjs`, and the key in `lib/card-art.ts`. Other agents may be editing these shared files, so check `git status` first and wait if they're touched.
-- The page icon: lucide `Hourglass`.
+- `app/(site)/(tools)/(saas)/free-trial-conversion-calculator/page.tsx`. Keep `layout.tsx` as it is.
+- `free-trial-conversion-calculator.tsx`, the client tool. It calls only the engine contract.
+- `free-trial-conversion-calculator-from-url.tsx`, the `useInitialQuery()` wrapper, as on `dns-lookup`.
+- `free-trial-conversion-calculator.module.css`, for the result's two-column top only.
+- `published-figures.ts`, the typed ChartMogul bands for the comparison.
+- `content/intro.mdx`, `content/usage.mdx`, and `content/article.mdx`, in the writing round.
+- Check that `lib/registered-site-pages.json` lists the route again once `page.tsx` exists.
+- Card art already exists and stays: `art/free-trial-conversion-calculator.*`, motif `trialConversion`, registered in `lib/card-art.ts`.
 
-No URL-restore wrapper. Business counts and prices don't go in the URL.
+Shared components improved during planning (Opus, done in this round): `UiRangeMarker` and `UiUnitGrid`. See Components.
 
 ### Catalog placement
 
-Primary and only catalog: `/saas-tools`. A founder there is working through SaaS money and growth numbers. Trial conversion is the earliest funnel step before MRR and CAC, so put it next to `/customer-acquisition-cost-calculator` and `/mrr-calculator`. The coordinator sets the final order. No secondary catalog fits. There's no growth or marketing catalog, and creating one isn't needed for this tool.
-
-Catalog `toolSpot` key: `free-trial-conversion-calculator`. Motif name: `trialConversion`.
+Primary and only catalog: `/saas-tools`. A founder there is working through SaaS money and growth numbers, and trial conversion is the funnel step before MRR and CAC. Place it near `/mrr-calculator` and `/customer-acquisition-cost-calculator`. The coordinator confirms the development row's membership during integration. No secondary catalog fits.
 
-- Takeaway: from a group that started together, a few paid before the window closed.
-- Focal subject: a short horizontal time track with three or four small ticks. A dashed vertical gate line stands near its right end, for day N. Left of the gate, a loose cluster of five or six small hollow circles sits on the track: the starters. Just past the gate, two filled `@primary` circles: the ones who paid.
-- One relationship: the gate. Paid means past the line in time, not moved by an arrow.
-- Tone: calm and neutral, with accent only on the two paid circles. No currency signs, numbers, cards, funnels, arrows, hourglasses, calendars, or person glyphs.
-- It must read differently from `customerChurn` (four person icons with an arrow out to one), `cohortRetention` (anchored bars), and `acquisitionCost` (person on a plinth). Wordless, and legible at card size in both themes.
+Card art: keep the existing `toolSpot`, key `free-trial-conversion-calculator`, motif `trialConversion`. Its takeaway still fits: from a group that started together, a few paid before the window closed. A dashed gate line on a short time track, hollow starter circles before it, and two filled circles past it. No words, numbers, cards, funnels, or person glyphs. Recheck it at card size in both themes during the frontend round, and redraw only if it fails.
 
 ## Interface
 
 ### Flow
 
-- Question: "Of the people who started in this cohort, what share paid within my window, and is the cohort old enough to trust?"
-- Minimum input: model (preselected), window, and one cohort row with starts, paid, and age.
-- Primary action: `Calculate conversion`.
-- Lead answer: the combined conversion rate, with its Complete or Provisional state.
-- Control mode: `single`. Every visible field drives the answer. `Add new MRR` is a visible checkbox that adds required fields to the main flow. The model choice changes labels and the published figures, not the math. That's documented here so the audit doesn't flag it as a no-op.
-
-Workbench order:
-
-1. `What people started`, a `UiChoiceGroup` with descriptions. These are plain words, never bare "opt-in/opt-out":
-   - `Free trial, no card`: `They try it without entering a card.`
-   - `Free trial, card upfront`: `They enter a card to start. The plan bills when the trial ends unless they cancel.`
-   - `Free plan`: `They sign up for a free plan with no end date.`
-2. `Follow-up window`, a narrow `UiTextField` with suffix `days`. Helper: `Days each account gets to pay, counted from its own start.`
-3. `Cohorts`, a group heading with one note under it: `Count each account once. Paid means the first payment went through. A card on file isn't a payment.` Then a `UiRepeatableList` with `Add cohort` (max 12). Each row is one line on desktop:
-   - `Cohort name`: optional, placeholder `Aug 2026`.
-   - `Trial starts`, or `Free signups` for the free plan model.
-   - `Paid within 30 days`. The number follows the window field and shows `Paid within window` while the window is blank.
-   - `Cohort age`, with a `days` suffix. A longer label wrapped and pushed the input out of line.
-   - The remove button.
-
-   The age field gets one helper, on the first row only: `Days from the last start in this cohort to the day you counted.` Removing the only row clears its fields and keeps the row.
-4. `Add new MRR from these customers`, a `UiCheckbox`. When on, below it in the main flow:
-   - `Currency`, a narrow `UiSelect`.
-   - `Price data`, a `UiChoiceGroup`: `One average amount` or `Monthly and annual plans`.
-   - For average: `Average monthly price` (currency suffix). Helper: `Recurring price only. Leave out setup and other one-time fees.`
-   - For split, two paired rows: `Monthly-plan customers` with `Average monthly price`, and `Annual-plan customers` with `Average annual price`. The same helper sits under the group.
-5. `Calculate conversion` (primary) and a quiet `Reset`, in `UiActionRow`.
-6. One divider, then the results.
+- Question: "What share of my trial starts paid, how sure is that, and how does it compare?"
+- Lead answer: the conversion rate, large, with `40 of 500 trial starts paid` under it.
+- Example values it opens with: `No card`, 500 trial starts, 40 paid, Advanced empty. The result shows 8%, marked `Example`.
+- Button: `Calculate conversion`, with a quiet `Reset` beside it.
+
+### Inputs
+
+| Input | Basic or Advanced | Required or optional | Hint, one sentence or none | What it changes in the result |
+| --- | --- | --- | --- | --- |
+| `Trial type`: `No card`, `Card upfront`, `Free plan` | Basic | Required, `No card` selected | `Card upfront means people enter payment details to start the trial.` | The lead label and count words, and which published range shows. |
+| `Trial starts`, or `Free signups` for `Free plan` | Basic | Required | `Everyone who started in one period, such as August, counting each account once.` | Every number in the result. |
+| `Paid` | Basic | Required | `Accounts from those starts whose first payment went through. A card on file isn't a payment.` | Every number in the result. |
+| `Follow-up window`, suffix `days` | Advanced | Optional | `Days each account had to pay, counted from its own start.` | The detail line reads `paid within 30 days`. With age, the `Complete` or `Provisional` status, and the cohort chart labels. |
+| `Cohort age`, suffix `days` | Advanced | Optional, needs the window | `Days from this cohort's last start to the day you counted paid.` | `Complete`, or `Provisional` with the days left. |
+| `Activated` | Advanced | Optional | `Starts that reached your activation event, such as a first project, including everyone who paid.` | Adds the funnel chart with activation and activated-to-paid rates. |
+| `Target conversion`, suffix `%` | Advanced | Optional | `The conversion rate you're aiming for.` | Adds `Extra paid at 10%` and, with a price, `Extra MRR at 10%`. Outlines the target units in the grid. |
+| `Currency` | Advanced | Optional, `USD` selected | none | The currency of every money value. |
+| `Monthly price`, currency suffix | Advanced | Optional | `Average monthly plan price for a new customer, without one-time fees.` | Adds `New MRR` and `ARR run rate`. Prices `Extra MRR`. |
+| `Annual price`, currency suffix | Advanced | Optional | `Average yearly plan price, which counts as a twelfth each month.` | Same as monthly price. |
+| `On annual plans` | Advanced | Optional, required when both prices are set | `How many of the paid accounts chose a yearly plan.` | Splits paid accounts between the two prices. |
+| `Other cohorts` rows: `Name`, `Trial starts`, `Paid`, `Age` (`days`) | Advanced | Optional. Starts and paid are required in a filled row | On the list: `Earlier months, channels, or plans, each with its own accounts.` | Adds the cohort chart and the `All cohorts` rate. |
+
+Advanced is one `UiDisclosure` named `Window, activation, revenue, and cohorts`, closed, with `uiSetSummary(count)`. The count is every filled field, plus one per filled cohort row. Currency counts only when a price is set.
+
+Cut: a separate `Trial length` field (it changes nothing the window doesn't), a monthly-customers count (derived from paid minus annual), and per-row trial type (put different trial types in separate runs or name the row).
+
+### Result
+
+Everything here comes from the person's inputs. Sources, method notes, and definitions go in the article.
+
+1. **The answer.** `UiPrimaryResult`, label `Trial to paid`, or `Free signup to paid`. Value `8%`, with hundredths when needed (`13.22%`, `1.88%`) and trailing zeros trimmed. Detail: `40 of 500 trial starts paid`, adding `within 30 days` when the window is set. Under it, a `UiStatusWord`:
+   - `Example` until the person calculates.
+   - `Complete` when the cohort has had the full window.
+   - `Provisional` with `18 days left`, warning tone. The rate can still rise.
+   - Nothing when maturity is unknown.
+2. **The picture.** `UiUnitGrid`, 10 × 10, beside the answer. Filled units are the paid share of every 100 starts, in the first data color. With a target, outlined units run from the rate up to the target. Legend: `Paid`, `Didn't pay`, and `At 10%`. It makes 2 of 100 feel like 2 of 100, which a percentage doesn't.
+3. **Supporting numbers.** `UiMetricGroup` under the answer, in the same column:
+   - `Didn't pay`: `460`.
+   - `Trials per paying customer`: `12.5`, hint `How many trial starts it took, on average, for each one that paid.`
+   - With a price: `New MRR` `$1,160.00`, hint `Paid accounts × their monthly amount, with annual plans as a twelfth.` And `ARR run rate` `$13,920.00`, hint `New MRR × 12. It isn't revenue earned this year, and it doesn't count churn.`
+   - With a target: `Extra paid at 10%` `10`, and with a price `Extra MRR at 10%` `$290.00`.
+   - With other cohorts: `All cohorts` `8.44%`, hint naming what's in it, such as `76 of 900 starts in complete cohorts. Sep is left out until it has 30 days.`
+4. **Comparison and likely range.** `UiRangeMarker`, full width. The track shows ChartMogul's two bands for the chosen trial type, the `You` marker at the rate, and a likely-range bar under the marker:
+   - The bands show only when the follow-up window is 180 to 184 days (six months), or isn't set. Any other window draws the marker and likely range alone, with the status word `No published range for a 30-day window` under it.
+   - `No card`: `No-card median, paid within 6 months` 4 to 6%, and `No-card top quarter, paid within 6 months` 10 to 15%. Scale 0 to 30%.
+   - `Card upfront`: `Card-upfront median, paid within 6 months` 25 to 35%, and `Card-upfront top quarter, paid within 6 months` 50 to 60%. Scale 0 to 80%.
+   - `Free plan`: `Free plan median, paid within 6 months` 3 to 5%, and `Free plan top quarter, paid within 6 months` 8 to 12%. Scale 0 to 30%.
+   - When the likely range's top is past the scale, the scale grows to the next 10%, up to 100%.
+   - Each band's hint: `ChartMogul survey of 200 software products, January 2026, counting paid within six months.`
+   - The likely range legend reads `Likely range at 500 starts` and `5.92 to 10.72%`, hint `The true rate is probably in this range. Fewer starts make it wider.`
+   - No grade words, no colors that judge.
+5. **Funnel**, with `Activated`. `UiLiveChart` kind `funnel`, full width, 260px tall, title `Where trial starts drop off`. Stages: `Trial starts` 500, `Activated` 200, `Paid` 40, each label with its share of the stage before (`40%`, `20%`).
+6. **Cohort comparison**, with other cohorts. `UiLiveChart` kind `horizontal-bar`, full width, title `Paid within 30 days, by cohort`, or `Paid, by cohort` without a window. One bar per cohort, `This cohort` first, rate at the bar end. A provisional cohort's label reads `Sep, 20 days left`. Height grows with rows, at least 260px.
+7. **Share.** `UiShareAction`, `Copy link`, at the end of the result.
 
 ### Components
 
@@ -316,161 +413,123 @@ Existing shared components:
 
 | Use | Component |
 | --- | --- |
-| Model, MRR method | `UiChoiceGroup` from `@/app/ui/controls` (option `description` carries the plain explanation) |
-| Window, counts, age, name, money | `UiTextField` from `@/app/ui/controls`, with `inputMode="numeric"` for counts and days and `decimal` for money, `days` or currency-code `suffix`, and autocomplete, capitalization, and spellcheck off. `UiTextField`, not `UiNumberField`, so pasted text like `-5` or `1,180` reaches the strict parser and gets its message. |
-| Cohort rows | `UiRepeatableList` from `@/app/ui/controls`, as on `/mrr-calculator` |
+| Band, rows, result region | `ToolWorkbench`, `ToolFieldRow`, `ToolResult` from `@/app/ui/tools/tool-workbench` |
+| Trial type | `UiChoiceGroup` from `@/app/ui/controls` |
+| Counts, days, prices, target, cohort names | `UiTextField` from `@/app/ui/controls`, with `inputMode="numeric"` for counts and days and `decimal` for money and the target, suffixes `days`, `%`, or the currency code. A text field, so pasted `-5` or `1,180` reaches the strict parser. |
 | Currency | `UiSelect` from `@/app/ui/controls` |
-| MRR toggle | `UiCheckbox` from `@/app/ui/controls` |
-| Actions | `UiActionRow` from `@/app/ui/display`, `UiButton` from `@/app/ui/controls` |
-| Lead | `UiPrimaryResult` from `@/app/ui/display` |
-| Maturity label | `UiStatusWord` from `@/app/ui/display`: `warning` tone for `Provisional`, `neutral` for `Complete` |
-| Cohort table, published figures | `UiDataTable` from `@/app/ui/display` |
-| New MRR facts | `UiKeyValueList` from `@/app/ui/display` |
-| Change, reset, and failure messages | `UiStatus` from `@/app/ui/display` |
-
-**Multi-cohort decision: build it, with the shared list.** It fits existing components: `UiRepeatableList` for input rows and `UiDataTable` for output, the same pairing `/mrr-calculator` uses. It's the clearest way to show the research's core point, that a young cohort understates its final rate. It also lets the combined rate leave maturing cohorts out instead of quietly blending them in. One row is the default, so the quick single-cohort job costs nothing extra.
-
-**No chart.** With at most 12 rates, the table shows exact values side by side. A bar chart would draw maturing cohorts as if they were finished, and marking them differently would need a new chart feature for little gain.
-
-**No new or improved shared component.** The row grid, paired MRR rows, and figures note are route CSS.
-
-Tool-specific component, in the route file:
-
-- `FreeTrialConversionCalculator`: owns the raw form state, row IDs, error mapping by `TrialFieldKey`, focus, status, and result rendering. It calls only `calculateFreeTrialConversion`. It reads `published-figures.ts` for the selected model.
-
-### Result regions
-
-Each region answers a different question, and no formatted value repeats.
-
-1. **Lead.** `UiPrimaryResult`.
-   - Label: `Free trial to paid` (both trial models) or `Free plan to paid`. With several cohorts, add `, complete cohorts` when `basis` is `complete`.
-   - Value: `13.22%`, `Under 0.01%`, or `Not available` with no unit.
-   - Detail line 1, one cohort: `156 of 1,180 trial starts paid within 30 days. 1,024 didn't.` For several cohorts: `130 of 900 starts in 2 complete cohorts paid within 30 days.`, adding `1 cohort still maturing is left out.` when `excludedMaturing` > 0. For `notAvailable`: `No starts in this cohort, so there's no rate.`
-   - Detail line 2, maturity, starting with `UiStatusWord`:
-     - Complete: `Complete: every account had the full 30 days.`
-     - Provisional, one cohort: `Provisional: the newest starts have 4 more days. This rate can still rise.`
-     - Provisional, several cohorts with basis `all`: `Provisional: no cohort has had the full 30 days yet.`
-   - The tone stays `neutral`. No grade color on the number.
-2. **Cohort table**, only with two or more cohorts. `UiDataTable` columns: `Cohort`, `Starts` (or `Signups`), `Paid`, `Rate`, `Status`, with numbers right-aligned. Status reads `Complete` or `20 days left`. Rows show in input order. A blank name shows `Cohort 1`. A rate of `notAvailable` shows `Not available`.
-3. **New MRR**, when on. A small heading, `New MRR from these customers`, then a `UiKeyValueList`:
-   - `New MRR`: `$7,644.00`.
-   - `How`: `156 paid customers × $49.00`, or for split, `3 monthly × $10.00 + 1 annual × $100.00 ÷ 12`.
-   - `ARR run rate`: `$460.00` with `New MRR × 12. Not revenue earned this year.`
-   - When `mrrIsRounded`: `Rounded to the cent.`
-   - When a maturing cohort is listed: `Includes customers from cohorts still maturing.`
-4. **Published figures for this model.** A small heading, then a `UiDataTable` with columns `Source`, `Who was measured`, `Reported`. Show only the rows for the selected model:
-   - ChartMogul, Growth Unhinged and ProductLed, January 2026 survey: all three models.
-   - First Page Sage, updated September 2025: all three.
-   - Recurly, 2022 data: both trial models. No free plan row.
-   - Leave out Recurly's 2024 50% median. The research marks it as too broad.
-   - Each source name links out.
-   - One note line under the table: `Directional only. Each source counts conversion its own way. No dated figure was found for indie SaaS by model and follow-up window.`
-   - The user's rate is never placed against these bands, scored, or colored.
+| Advanced | `UiDisclosure` and `uiSetSummary` from `@/app/ui/controls` |
+| Other cohorts | `UiRepeatableList` from `@/app/ui/controls` |
+| Button, reset, status | `UiButton` from `@/app/ui/controls`, `UiActionRow` and `UiStatus` from `@/app/ui/display` |
+| Answer, status word, numbers | `UiPrimaryResult`, `UiStatusWord`, `UiMetricGroup` from `@/app/ui/display` |
+| Picture | `UiUnitGrid` from `@/app/ui/display` |
+| Comparison and likely range | `UiRangeMarker` from `@/app/ui/display` |
+| Funnel, cohort bars | `UiLiveChart` from `@/app/ui/charts/chart-client` |
+| Copy link | `UiShareAction` from `@/app/ui/controls` |
+| Shared link | `useInitialQuery` from `@/app/ui/tools/use-initial-query` |
 
-### States
+Shared components improved in this round:
 
-- **Initial.** Model `Free trial, no card`. Window blank. One blank cohort row. MRR off, with USD and `One average amount` preselected under it. No result. The published figures appear only with a result.
-- **Invalid or incomplete.** Clear the old result and keep the inputs. Show one error under each invalid field. Put a list-level `cohorts` error in the list's `addDescription` slot as an error. Focus the first invalid field in reading order and add no error panel. All error fields stay visible: MRR fields only exist while the checkbox is on, and the engine only checks them then.
-- **Valid.** Render the regions, focus the lead, and announce once through the focused output.
-- **Zero starts.** Valid. The lead reads `Not available`. It isn't an error.
-- **Provisional.** Valid. Same layout, with a warning-tone `Provisional` word and the days left.
-- **Edited after a result.** Clear the result and announce once, politely: `Inputs changed. Calculate again.` Changing the model counts as an edit. Focus stays where the reader is.
-- **Rows.** `Add cohort` focuses the new row's name field. At 12 rows the add button is disabled with `Up to 12 cohorts`. Removing a row focuses the next row, or `Add cohort`. Removing the only row clears it instead.
-- **MRR toggle and method.** Turning it on adds fields in place, and focus stays on the checkbox. Turning it off or switching method keeps drafts.
-- **Unexpected failure.** If the engine throws, keep the inputs, clear the result, and show one `UiStatus` error by the actions: `Couldn't calculate. Try again.`
-- **Reset.** Restore the initial state, focus the model group, and announce `Form reset.`
-- **Restored.** The clean URL never changes. A back-forward cache restore keeps the result until the next edit.
-- **Long values.** `10,000,000` starts, `$10,000,000,000,000,000.00` MRR, and a 40-character cohort name fit their cells and leads without clipping. Names wrap in the table.
-- **Loading, partial, and retry.** These don't apply. The calculation is synchronous and local.
-
-### Responsive and accessible behavior
-
-Desktop:
-
-- Shared workbench band with a measured inner width.
-- The model choices sit in one row. The window field is narrow.
-- Each cohort row is a five-column grid: name, starts, paid, age, remove. The remove button is in the fixed last column. Labels repeat per row, like the MRR calculator's plan rows.
-- Paired MRR fields share a row.
-- Results stack full width: lead, table, MRR, figures.
-
-Mobile (set breakpoint, as the sibling tools use):
-
-- Model choices stack.
-- Each cohort row stacks its fields in one column, in tab order. In two columns, `Paid within 30 days` wrapped and misaligned its input. The remove button stays top-right.
-- Paired MRR fields stack. Buttons go full width.
-- `UiDataTable` turns into labeled rows.
-- No page-level horizontal overflow. Grid children get `min-width: 0`.
-
-Keyboard and screen readers:
-
-- Tab order follows the visual order, row by row.
-- Enter in any field submits.
-- Every field has a visible label. Each row is a group named `Cohort 2` (or its name), so a screen reader announces "Cohort 2, Paid within 30 days".
-- Errors are tied to their fields.
-- One polite live region announces changes, resets, and failures. Results are announced through the focused lead only.
-- The `Provisional` meaning is in words, never only in color.
-
-Check at desktop and mobile in both themes:
-
-- 1,180 / 156 with average MRR `49`.
-- The three-cohort example.
-- The provisional single cohort.
-- 0 / 0.
-- 100 / 101 and `-5` errors.
-- The split MRR rounding example.
-- 12 rows with long names.
+- `UiRangeMarker` gets an optional `range` (`from`, `to`, `label`, `valueText`, `hint`). It draws the person's likely range as a bar in the first data color, just under the track, with the `You` marker through it, and adds it to the legend first. Any tool with a small sample can use it.
+- `UiUnitGrid` gets an optional `target` amount and `targetLabel`. Units from the filled amount up to the target draw as outlined, so a gap to a goal shows in the same picture. Its fill now uses the first data color instead of the accent fill, as `design-system.md` requires for result visuals. `tone="neutral"` is unchanged.
+- Both have gallery examples in the Results section.
 
-## Content
+Tool-specific components, in the route:
 
-Plan for the writing session. The engine was run with the three-cohort example (Jul 400/60/75, Aug 500/70/45, Sep 450/30/10, window 30, average price 29): lead 14.44%, complete cohorts, Sep left out with 20 days left, 160 paid customers, new MRR $4,640.00, ARR run rate $55,680.00. A reader might misread the lead as the average of the row rates, read the maturing Sep row as a drop, or read "didn't pay" as money missed.
+- `FreeTrialConversionCalculator`: form state, cohort row IDs, error mapping by `TrialFieldKey`, focus, stale state, and the result. It calls only the engine.
+- `FreeTrialConversionFromUrl`: reads a shared link and renders the tool with `key={query.key}`.
 
-### Search intent and title
+### Layout
 
-The searcher wants their trial-to-paid rate, and to know if it's any good. Top results take two counts from any period, accept impossible counts, and quote unsourced "good" bands. This page ties both counts to one start cohort, says when a cohort is too young, and shows dated figures with who was measured.
+Desktop, inside the 66rem working width:
 
-- Visible title: `Free trial conversion calculator: how many free trials turn into paid customers?`
-- SEO title: `Free trial to paid conversion rate calculator`
-- SEO description: names trial or free plan starts, a follow-up window, complete or provisional cohorts, and optional new MRR. No grade, no benchmark promise.
-- Card: `Free trial conversion`, with the share of a trial cohort that paid in the window, and the new MRR.
+- Row 1: `Trial type` choice row. Three short options in one line.
+- Row 2: `Trial starts` and `Paid`, side by side, each half the width. They're one decision.
+- `Window, activation, revenue, and cohorts`, closed. Inside:
+  - Row: `Follow-up window`, `Cohort age`, `Activated`, `Target conversion`. Four across: everything about this cohort.
+  - Row: `Currency`, `Monthly price`, `Annual price`, `On annual plans`. Four across: revenue.
+  - `Other cohorts` list. Each row on one line: name, starts, paid, age, and remove in a fixed last column. `Add cohort` below, disabled at 12 with `Up to 12 cohorts`.
+- Action row: `Calculate conversion` and `Reset`, with `Inputs changed` beside them when stale.
+- Result, below one divider:
+  - Top: two columns. Left, about two thirds: the answer, then the supporting numbers in a grid under it. Right: the unit grid at 280px, top-aligned with the answer, legend under it. Both columns hold their own, so there's no empty half.
+  - Then full width: the comparison and likely range, the funnel if any, the cohort chart if any, and `Copy link`.
 
-### Reader questions
+Phones:
 
-| Question | Where it's answered |
-| --- | --- |
-| What's my trial-to-paid rate? | Tool lead. Formula and the 6% versus 20% example in content. |
-| Which counts do I enter, and from where? | Usage: cohort, paid, window, age. |
-| Why does my newest month look low? | Tool `Provisional` line and table. Usage on reading the result. |
-| What counts as paid? | Cohort note in the tool. Content section with the Stripe link. |
-| Why doesn't this match Stripe's number? | Content: Stripe's rolling 30-day metric. |
-| What's a good rate? | Content table of three dated sources by trial type, plus the in-tool figures for the chosen type. |
-| Free plan or free trial? | Model choice descriptions. Content section on the longer window. |
-| What MRR did they add? | Tool MRR group. Content on run rate versus revenue. |
+- Every row stacks in reading order. Trial type options wrap.
+- Each cohort row stacks its fields, with remove top-right.
+- Result: the answer, then the unit grid at full column width up to 320px, then the supporting numbers in two columns, then the full-width pieces. The range marker's legend stacks. Charts keep their overflow inside their own frame.
 
-### Outline
+### States
+
+- **Opens:** the example and its result, status `Example`. Advanced closed, `Not used`.
+- **Edited after a result:** `ToolResult stale` steps the result back, and `UiStatus` says `Inputs changed`. Opening or closing Advanced isn't an edit.
+- **Calculated:** the result updates, `Example` goes away, focus moves to the answer.
+- **Basic error:** on press, errors under each field, focus on the first. The last good result stays stale.
+- **Advanced error:** on press, Advanced opens whenever it holds an error, even when a Basic error takes focus first. Focus goes to the first error in reading order. The main answer updates. Only the part that field feeds disappears: the funnel, the revenue numbers, the target numbers, the cohort chart and `All cohorts`, or the maturity word.
+- **Paid more than starts:** a field error on `Paid`. Never a clamp or a rate past 100%.
+- **Zero starts:** valid. The answer reads `—` with `No trial starts`. The grid is empty, the range marker draws bands only, and the numbers read `—`. The layout keeps its size.
+- **Zero paid:** `0%`, with `Trials per paying customer` `—`. The likely range still shows, from 0%.
+- **Tiny rate:** `Under 0.01%`.
+- **Provisional:** warning-tone `Provisional` and the days left, beside the answer and on each young cohort's bar label.
+- **Target at or below the rate:** `Extra paid at 5%` reads `0`, and the grid draws no outlined units.
+- **Window other than six months:** the published bands drop out, and `No published range for a 30-day window` sits under the marker. The likely range stays.
+- **Shared link:** opens and calculates right away. Invalid values show their errors the same way as a press, with Advanced opened if needed.
+- **Reset:** back to the example and its result, Advanced closed, cohort rows cleared.
+- **Long values:** 10,000,000 starts, a 17-digit MRR, and a 40-character cohort name fit without page overflow. Names wrap in chart labels.
+- **Loading and retry:** don't apply. The calculation is local and synchronous.
+
+## Content
 
-- **Intro.** Three sentences: what you get, what to have ready, the optional MRR.
-- **Usage.** `What to enter`: trial type when unsure, the window, where the counts come from, cohort age with a date example, the MRR prices. `How to read the result`: complete and provisional, the combined rate, the cohort table, "didn't pay", new MRR. One `Example` with the three-cohort run.
-- **Article.** `How is free trial conversion rate calculated?` (Formula, 6% vs 20% example). `What counts as a paid conversion?` (list). `Why doesn't this match Stripe's trial conversion rate?` `What is a good free trial conversion rate?` (table across types, sources list, note). `How is a free plan different from a free trial?` `Is new MRR the same as revenue?` with next steps.
+Written after the frontend. The tool was run with the example (500 / 40), the forum case (160 / 3), the small-sample case (42 / 30), and the full Advanced example before writing.
 
-No chart and no marker art in the article. The card art is registered.
+### Search intent and title
 
-### Left out on purpose
+The searcher has two counts and wants the rate, then wants to know if it's normal. Top results grade the number against unsourced bands and accept impossible counts. This page gives the rate with its counts, says how sure it is, and shows dated ranges that match the trial type.
 
-- Input format, ranges, and the 12-cohort limit: field errors.
-- Zero starts, `Under 0.01%`, cent rounding: result text and the spec.
-- Every combined-rate fallback case: the result lines say which cohorts were used.
-- Card versus no-card strategy advice, activation, CAC, churn: out of scope. Linked next steps instead.
+- Visible title: keep `Free trial conversion calculator: how many free trials turn into paid customers?`
+- SEO title: keep `Free trial to paid conversion rate calculator`.
+- SEO description, new: `Find what share of your free trial starts paid, how sure that rate is at your cohort's size, and how it compares with published ranges for your trial type.`
+- Card: keep the name `Free trial conversion`. New description: `Find what share of your trial starts paid, and how it compares.`
 
-### Facts and limits
+### Reader questions
 
-- Formula and same-cohort rule: ChartMogul trial-to-paid help article.
-- Paid event and trialing to active: Stripe Subscription object. Count each account once; Recurly separates subscribers from subscriptions.
-- Stripe rolling 30-day rate can exceed 100%: Stripe support article.
-- Benchmarks: ChartMogul, Growth Unhinged, and ProductLed (January 2026 survey, 200 products); First Page Sage (86 clients, 2022 to 2025, updated September 2025); Recurly (2022 data, 803 sites, 22 million trials). Leave out Recurly's 2024 50% median.
-- Free plan six-month window: ChartMogul 2026 report.
-- MRR normalization and one-time fees: ChartMogul MRR.
-- Avoid: benchmarks as targets, grades, "lost" revenue, saying card-upfront is better, an indie SaaS benchmark (unknown).
+| Question | Where it's answered |
+| --- | --- |
+| What percentage of my trial users paid? | Tool answer. Formula and the 6% versus 20% example in the article. |
+| Which counts do I enter? | Usage, "What to enter". |
+| What counts as paid? | Paid hint, usage, and the article section. |
+| Is 3 out of 160 bad? | Tool comparison and likely range. Usage example. Article "good rate" and "small cohort" sections. No grade anywhere. |
+| Why does my newest month look low? | `Provisional` status. Article "How long should you wait". |
+| What's a good rate? | Article table of four sources, with who was measured. |
+| Does a card upfront convert better? | Article, with First Page Sage's visitor-to-trial and trial-to-paid averages. |
+| How much MRR would 10% bring? | Tool target and revenue numbers. Article MRR section. |
 
-### Next steps
+### Outline
 
-`/mrr-calculator`, `/customer-acquisition-cost-calculator`, `/customer-churn-calculator`.
+- Intro: what you get and what to have ready, in three sentences.
+- Usage: three numbered steps for the counts, what counts as paid, a table of what each Advanced input answers, how to read the result, and one `Example` (160 / 3).
+- Article:
+  - `How is free trial conversion rate calculated?` Formula, then an `Example` of the calendar-month mistake.
+  - `What counts as a paid conversion?` Bullets.
+  - `How long should you wait before you count?` Paragraphs.
+  - `What is a good free trial conversion rate?` Source table, then a `Note` on small cohorts.
+  - `Why does a small cohort's rate swing so much?` The 42 / 30 case and the Wilson interval.
+  - `Does requiring a card upfront improve conversion?` Small table.
+  - `Is new MRR from trials the same as revenue?`
+  - `What to check next` Links.
+
+Left out: input format rules and limits (field errors), zero starts and `Under 0.01%` (the result shows them), the combined-rate fallback rules (the `All cohorts` hint names what's in it), and advice on trial length (the most common length isn't evidence of the best one).
+
+### Facts, limits, and sources
+
+- Formula and cohort rule, later conversions changing a cohort: [ChartMogul help article](https://help.chartmogul.com/article/219-chart-trial-to-paid-conversion-rate).
+- Ranges by trial type, six-month window, 200 products, January 2026, typical $1M to $10M ARR, self-estimated: [ChartMogul SaaS Conversion Report](https://chartmogul.com/reports/saas-conversion-report/). Free plan bands are for freemium with a regular signup.
+- Trial-to-paid and visitor-to-trial averages, 86 companies, 2022 to 2025, one paid month counts: [First Page Sage](https://firstpagesage.com/seo-blog/saas-free-trial-conversion-rate-benchmarks/), updated September 5, 2025.
+- 37.5% site-level average, 39.0% with billing details, 12.0% without, per subscription, 803 sites, January to August 2022: [Recurly](https://recurly.com/resources/report/state-of-subscriptions-acquisition/).
+- ARR = MRR × 12: [ChartMogul SaaS Go-To-Market Report glossary](https://chartmogul.com/reports/saas-go-to-market-report/).
+- Likely range: 95% Wilson score interval.
+- Avoid: calling any rate good or bad, blending sources into one average, saying card-upfront produces more customers, a recommended trial length, and an indie-specific benchmark (none exists).
+
+### Next step
+
+`/mrr-calculator`, `/customer-churn-calculator`, `/customer-acquisition-cost-calculator`, `/customer-lifetime-value-calculator`: totals, retention, cost, and value of the customers this tool counts.
diff --git a/content_docs/kdp-royalty-calculator/brief.md b/content_docs/kdp-royalty-calculator/brief.md
deleted file mode 100644
index 8aee764a..00000000
--- a/content_docs/kdp-royalty-calculator/brief.md
+++ /dev/null
@@ -1,13 +0,0 @@
-# Brief: KDP royalty calculator
-
-## Who is here
-
-An author is pricing a paperback, hardcover, or Kindle eBook for Amazon.com. They know the page count or file size and want to see whether a price leaves room for royalties and ads.
-
-## The job
-
-They leave with one selected-price royalty, the cost that produced it, the minimum viable price, and a small comparison that shows what changes at KDP's rate boundary. An optional monthly target turns the per-sale result into a unit count.
-
-## Show vs say
-
-The tool UI carries the work: a single scenario form, a royalty-first result, a cost receipt, a comparison table, and the ad and target math. A table compares price points because rate, cost, royalty, and margin repeat. Short sentences beside the result explain the US-only scope, the eBook 70% fallback, the source date, and limits such as taxes and price matching. No chart or marker drawing is needed.
diff --git a/content_docs/kdp-royalty-calculator/competitive-report.md b/content_docs/kdp-royalty-calculator/competitive-report.md
deleted file mode 100644
index 0db8ec7b..00000000
--- a/content_docs/kdp-royalty-calculator/competitive-report.md
+++ /dev/null
@@ -1,147 +0,0 @@
-# Competitive report: kdp royalty calculator
-
-Status: ready
-Tool: KDP royalty calculator
-Route: `/kdp-royalty-calculator`
-Direct competitors reviewed: 5
-Saturation exception: yes
-
-## Research scope
-
-This review covers pricing decisions for paperback, hardcover, and Kindle ebooks: printing cost, royalty rate, price floors, delivery cost, ad headroom, and monthly sales targets. Queries tried: `KDP royalty calculator`, `KDP paperback printing cost calculator`, `KDP hardcover royalty`, `KDP ebook delivery fee`, and `KDP ACoS calculator`. Repeated domains: kdp.amazon.com, kindlepreneur.com, bookow.com, ingramspark.com, and publishing calculator sites. Exclusions: Expanded Distribution, non-US marketplaces, taxes and VAT, advertising platform reporting, and live price scraping. The job is established but fragmented, so the saturation exception is yes.
-
-## Search intent
-
-| Query job | User intent | Required answer | Current gap |
-| --- | --- | --- | --- |
-| Print royalty | See what remains after printing cost | Rate, cost, and royalty per sale | Older calculators use outdated 60% thresholds. |
-| Minimum price | Avoid a price that loses money on print | Cost-covering price floor | Rate-band changes make a single division misleading. |
-| Ebook pricing | Include file-size delivery cost | Delivery and effective rate | Delivery is often omitted or hidden. |
-| Ad decision | Know maximum spend per sale | Break-even spend and ACoS | Ad calculators can lose the publishing context. |
-| Monthly target | Translate income goal into unit sales | Copies at selected price | Many tools stop at per-sale royalty. |
-
-## User pain evidence
-
-| Repeated problem | Evidence | Product implication |
-| --- | --- | --- |
-| Print royalty rules changed by price bands and older calculators remain in circulation. | [Amazon print royalty rules](https://kdp.amazon.com/en_US/help/topic/G201834330); [Reddit KDP royalty search](https://www.reddit.com/r/selfpublish/search/?q=royalty%20rate&restrict_sr=1) | Version the constants and show the price band. |
-| Authors forget that printing cost is deducted from the percentage royalty. | [Amazon print cost rules](https://kdp.amazon.com/en_US/help/topic/G201834340); [KDP community royalty search](https://www.kdpcommunity.com/s/search?q=printing%20cost) | Make cost and royalty separate lead-supporting values. |
-| Ebook delivery cost varies with file size and affects the 70% result. | [Amazon ebook delivery rules](https://kdp.amazon.com/en_US/help/topic/G200634500); [Reddit Kindle delivery search](https://www.reddit.com/r/selfpublish/search/?q=delivery%20fee%20ebook&restrict_sr=1) | Ask for file size and expose the delivery calculation. |
-
-## Technical truth to verify
-
-| Claim | Authority | Build treatment |
-| --- | --- | --- |
-| US print royalties use 50% or 60% depending on list price and marketplace. | [Amazon print royalty rules](https://kdp.amazon.com/en_US/help/topic/G201834330) | Use the Amazon.com threshold and label the marketplace scope. |
-| Printing cost is fixed plus per-page and differs by trim, interior, paper, and binding. | [Amazon print costs](https://kdp.amazon.com/en_US/help/topic/G201834340) | Use current US cost branches in a pure engine. |
-| Hardcover has separate fixed and per-page costs. | [Amazon hardcover print costs](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H) | Keep hardcover cost data separate from paperback. |
-| Ebook 70% royalty uses price minus delivery cost, while 35% does not deduct delivery. | [Amazon ebook delivery rules](https://kdp.amazon.com/en_US/help/topic/G200634500) | Round delivery and royalty to cents. |
-| Amazon.com 70% ebook prices sit in the $2.99 to $12.99 band. | [Amazon ebook pricing](https://kdp.amazon.com/en_US/help/topic/G200634560) | Fall back to the effective 35% rate outside that band. |
-
-## Competitor reviews
-
-### Competitor 1: Amazon KDP royalty calculator
-
-URL: [kdp.amazon.com/royalty-calculator](https://kdp.amazon.com/royalty-calculator)
-
-- [Observed] The official calculator handles a royalty scenario with many publishing inputs.
-- [Documented] Amazon publishes print cost and royalty rules separately from the calculator.
-- [Observed] The workflow is scenario-first and does not focus on monthly targets or ad headroom.
-- [Inferred] A compact planner can answer pricing comparisons faster for a known setup.
-- [Unknown] The public calculator's internal data update timing is not visible as a version label.
-
-```text
-format -> trim -> pages -> price -> marketplace
-                    -> royalty result
-```
-
-### Competitor 2: Kindlepreneur KDP royalty calculator
-
-URL: [kindlepreneur.com KDP royalty calculator](https://kindlepreneur.com/kdp-royalty-calculator/)
-
-- [Observed] The page presents a simple pricing and royalty workflow for authors.
-- [Observed] It emphasizes a quick answer over a full cost receipt.
-- [Documented] A third-party calculator must follow current Amazon rate rules to stay correct.
-- [Inferred] Users benefit from a dated rate note and a comparison table.
-- [Unknown] The public page does not make every current branch and threshold auditable.
-
-```text
-format + pages + price -> estimated royalty
-```
-
-### Competitor 3: Bookow KDP royalty calculator
-
-URL: [bookow.com KDP royalty calculator](https://www.bookow.com/kdp-royalty-calculator/)
-
-- [Observed] Bookow provides a focused KDP calculator with fewer visible controls.
-- [Observed] The result is suitable for a single list-price check.
-- [Documented] Print cost depends on more fields than a price-only form exposes.
-- [Inferred] A price comparison table would reduce repeated submissions.
-- [Unknown] The page does not state a revision date beside its formula.
-
-```text
-pages + format + price -> one royalty number
-```
-
-### Competitor 4: IngramSpark rate calculator
-
-URL: [ingramspark.com rate calculator](https://www.ingramspark.com/plan-and-price/print-and-ship)
-
-- [Observed] IngramSpark positions its calculator around a different distribution service.
-- [Documented] Its print and distribution assumptions are not KDP assumptions.
-- [Observed] The pricing workflow includes product and shipping context.
-- [Inferred] It is useful as a contrast but should not be mixed into KDP output.
-- [Unknown] A visitor can mistake cross-platform costs for KDP costs without an explicit boundary.
-
-```text
-platform -> format -> quantity / ship -> cost
-KDP planner -> KDP rules only
-```
-
-### Competitor 5: Publisher Rocket keyword and book tools
-
-URL: [publisherrocket.com](https://publisherrocket.com/)
-
-- [Observed] Publisher Rocket focuses on market and keyword research around books.
-- [Observed] Pricing is not the primary visual answer on its public product page.
-- [Documented] Market research cannot replace a royalty formula.
-- [Inferred] A pricing planner should avoid demand estimates and fake sales forecasts.
-- [Unknown] The public product page does not expose current KDP print constants.
-
-```text
-market inputs -> demand research -> publishing decision
-royalty inputs -> cost / price -> unit economics
-```
-
-## Comparison matrix
-
-| Capability | Amazon | Kindlepreneur | Bookow | IngramSpark | Publisher Rocket | stack127 launch decision |
-| --- | --- | --- | --- | --- | --- | --- |
-| Paperback cost | Yes | Yes | Partial | Other platform | No | Current US branch |
-| Hardcover cost | Yes | Partial | Unknown | Other platform | No | Separate branches |
-| Ebook delivery fee | Yes | Partial | Unknown | No | No | File-size input |
-| Current rate threshold | Yes | Unknown | Unknown | Other platform | No | Show source date |
-| Minimum cost-covering price | No | Partial | Partial | Other platform | No | Compute by band |
-| Price comparison | One scenario | Partial | One scenario | Quantity | No | Four-point table |
-| Break-even ad spend | No | Partial | No | No | No | Royalty per sale |
-| Copies for target income | No | No | No | No | No | Optional target |
-
-## Formula and data disagreements
-
-The most important disagreement is not arithmetic but scope. Some tools mix Amazon marketplaces, Expanded Distribution, or another printer's cost model. This planner is US Amazon.com only and excludes Expanded Distribution. Print floors are solved piecewise because the rate changes at $9.99; dividing every cost by 60% would misstate cheaper books. Ebook delivery uses the current US per-MB rule and a rounded-KB input model, with VAT excluded because the planner does not have a tax jurisdiction input.
-
-## Evidence-backed opportunities
-
-- Keep print and ebook branches separate while sharing the price comparison result.
-- State the data date and source links next to a rate-sensitive answer.
-- Explain break-even ad spend as a ceiling, not a recommended ad budget.
-- Give a monthly copy count only when the user supplies a target and the royalty is positive.
-- Keep Expanded Distribution out of the launch scope so the output remains auditable.
-
-## Sources
-
-- [KDP print costs](https://kdp.amazon.com/en_US/help/topic/G201834340), checked 2026-09-16.
-- [KDP print royalties](https://kdp.amazon.com/en_US/help/topic/G201834330), checked 2026-09-16.
-- [KDP hardcover costs](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H), checked 2026-09-16.
-- [KDP ebook pricing](https://kdp.amazon.com/en_US/help/topic/G200634560), checked 2026-09-16.
-- [KDP ebook delivery](https://kdp.amazon.com/en_US/help/topic/G200634500), checked 2026-09-16.
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-# Edge cases and tests: KDP royalty calculator
-
-Status: ready
-Tool: KDP royalty calculator
-Route: /kdp-royalty-calculator
-Depends on: competitive-report.md, implementation-report.md, interface-contract.md, brief.md
-
-## Risk model
-
-| Priority | Meaning for this tool |
-| --- | --- |
-| P0 | A wrong cost, rate, floor, royalty, target count, or fallback could cause an author to price a book from false economics. A privacy leak, stale result, or inaccessible primary answer also belongs here. |
-| P1 | A common format change, invalid-input recovery, keyboard flow, copy action, responsive layout, publication check, or state transition fails while the engine's answer remains otherwise correct. |
-| P2 | An uncommon rendering, resilience, wording, theme, or performance issue makes a correct result harder to inspect without changing the calculation. |
-
-## Requirement traceability
-
-| Requirement ID | Implementation requirement | Covered by cases |
-| --- | --- | --- |
-| R1 | State Amazon.com and USD as fixed scope without a marketplace selector. | EC-034, EC-031 |
-| R2 | Show only compatible format fields and reset incompatible values. | EC-021 |
-| R3 | Resolve supported trim catalogs, regular or large class, and page limits. | EC-004, EC-005, FF-006 |
-| R4 | Normalize odd print pages to an even effective count and enforce the resulting limit. | EC-006, FF-006 |
-| R5 | Match every current US paperback cost branch. | EC-007, FF-001, FF-003, FF-004 |
-| R6 | Match hardcover cost branches and their page boundaries. | EC-008, FF-005 |
-| R7 | Use 50% at $9.98 and 60% at $9.99. | EC-009, FF-002 |
-| R8 | Solve the piecewise print price floor without under-covering cost. | EC-010, FF-007 |
-| R9 | Round eBook delivery by kilobyte, apply the minimum, and use it only in the 70% equation. | EC-011, FF-008 |
-| R10 | Apply eBook 70% only inside its inclusive price band and warn on fallback. | EC-012, FF-009 |
-| R11 | Enforce file-size-dependent eBook 35% floors and the maximum. | EC-013, FF-009 |
-| R12 | Clear invalid results and focus the first recovery point. | EC-001, EC-003, EC-005, EC-020 |
-| R13 | Lead with royalty per sale, then show the cost or delivery, floor, rate, and margin. | EC-019, EC-036 |
-| R14 | Produce unique valid boundary and selected-price comparison rows. | EC-016, FF-011 |
-| R15 | Show positive break-even ad spend and ACoS from the selected royalty. | EC-015, FF-001 |
-| R16 | Handle blank, zero, positive, and impossible monthly targets. | EC-002, EC-014, FF-010 |
-| R17 | Apply money, rate, margin, ACoS, version, and source-date display rules. | EC-034, FF-012 |
-| R18 | Clear stale results on edit, focus valid results, and restore defaults on reset. | EC-018, EC-019, EC-022 |
-| R19 | Preserve task order and table overflow behavior at required widths. | EC-028, EC-036 |
-| R20 | Keep all scenario data local and out of analytics payloads. | EC-029, EC-030 |
-| R21 | Keep the route unpublished until a separate publication decision. | EC-031, EC-032 |
-| UI-001 | Put one royalty-per-sale answer first and make it dominant. | EC-019, EC-036 |
-| UI-002 | Give each fact one standalone owner and allow repetition only in the comparison table. | EC-016, EC-036 |
-| UI-003 | Use a semantic exact-value table and omit misleading gauges, bars, and timelines. | EC-016, EC-036 |
-| UI-004 | Keep controls usable and allow only the comparison region to scroll at locked widths. | EC-028 |
-| UI-005 | Keep the clean route and browser history free of serialized scenario state. | EC-030, EC-035 |
-| UI-006 | Keep active inputs visible, compatible, and defaulted after format changes. | EC-021 |
-| UI-007 | Cover invalid, fallback, blank target, non-positive royalty, failure, retry, and reset states. | EC-015, EC-017, EC-020, EC-022, EC-035 |
-| UI-008 | Show fixed scope, formula version, and source date without a source-card grid. | EC-031, EC-034, EC-036 |
-
-## Coverage checklist
-
-Every applicable risk family has a concrete case below. The calculation has no runtime upstream service, so the network family is explicitly not applicable beyond checking that no request is made.
-
-| Family | Case IDs or specific non-applicability reason |
-| --- | --- |
-| Input grammar | EC-001, EC-002, EC-003 |
-| Numeric boundaries | EC-005, EC-006, EC-007, EC-008, EC-009, EC-010, EC-011, EC-012, EC-013, EC-014, EC-015 |
-| Configuration dependencies | EC-004, EC-005, EC-006, EC-021 |
-| Technical truth | EC-007, EC-008, EC-009, EC-010, EC-011, EC-012, EC-013, EC-016, EC-017 |
-| Submission and concurrency | EC-018, EC-019, EC-020, EC-021, EC-022, EC-023 |
-| Network and upstream | Not applicable: the formula runs synchronously from versioned local constants and makes no upstream request; EC-017 verifies closed failure if those constants are unavailable. |
-| Persistence and sharing | EC-024, EC-025, EC-030, EC-035 |
-| Accessibility | EC-018, EC-019, EC-020, EC-022, EC-026, EC-027, EC-028 |
-| Responsive and themes | EC-027, EC-028, EC-036 |
-| Security and privacy | EC-024, EC-025, EC-029, EC-030 |
-| SSR and SEO | EC-031, EC-032, EC-034, EC-035 |
-| Performance | EC-023, EC-033 |
-| Control mode, switching, parity, and hidden-state recovery | EC-037. Disclosure mode has one visible pricing input model; opening or closing calculation details preserves normalized economics, product-branch values stay explicit, and an invalid active field cannot be hidden in a collapsed region. |
-
-## Formula or resolution fixtures
-
-This is a formula contract. The primary oracles are the versioned implementation report and the official KDP pages for [paperback costs](https://kdp.amazon.com/en_US/help/topic/G201834340), [print royalties](https://kdp.amazon.com/en_US/help/topic/G201834330), [hardcover costs](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H), [eBook pricing](https://kdp.amazon.com/en_US/help/topic/G200634560), and [eBook delivery](https://kdp.amazon.com/en_US/help/topic/G200634500). All money expectations below are integer cents unless marked as a display string.
-
-| ID | Inputs or source responses | Expected exact output or classification | Oracle/source | Branches and invariants |
-| --- | --- | --- | --- | --- |
-| FF-001 | Paperback, 6x9, black ink, white paper, 300 pages, $14.99. | Effective pages 300; printing cost $4.60; rate 60%; royalty $4.39; floor $9.20; margin 29.3%; break-even ad spend $4.39; ACoS 29.3%. | fixed $1.00 + 300 times $0.012; round($14.99 times 60%) - $4.60; floor ceil($4.60 / 50%); official KDP paperback cost and royalty sources. | Print uses the 60% branch at or above $9.99; displayed royalty uses integer cents; floor must cover cost. |
-| FF-002 | The FF-001 scenario at list prices $9.98 and $9.99. | $9.98 yields rate 50% and royalty $0.39; $9.99 yields rate 60% and royalty $1.39. | round($9.98 times 50%) - $4.60 = $0.39; round($9.99 times 60%) - $4.60 = $1.39; official KDP print royalty source. | The threshold is inclusive on the 60% side at $9.99; comparisons recalculate each row. |
-| FF-003 | Regular paperback black ink at raw page counts 109, 110, and 111. | Effective pages are 110, 110, and 112. Printing costs are $2.30, $2.30, and $2.34. | Fixed $2.30 through 110 pages; after normalization, 112 times $0.012 + $1.00 = $2.344, displayed as $2.34; official KDP paperback cost source and the ready implementation report. | The overlapping 110-page source label resolves to fixed-only. Odd input never bypasses normalization. |
-| FF-004 | Regular paperback groundwood at 112 and 114 pages; regular premium color at 40 and 42 pages; regular standard color at 72 pages; repeat with a large trim. | Groundwood costs $2.23 at 112 and $2.30 at 114. Premium color costs $3.60 at 40 and $3.73 at 42. Standard color at 72 costs $2.84 regular and $3.89 large. | Direct application of the implementation-report cost table, rounded to cents at display. | Fixed and per-page branches are independent by profile and trim class. |
-| FF-005 | Hardcover 6x9 black and white at 108, 109, and 110 pages; large hardcover at 108 and 110; premium color at raw 75 pages. | Regular black costs $6.80 at 108 and $6.97 at normalized 110. Large black costs $7.49 at 108 and $7.52 at normalized 110. Raw 75 premium normalizes to 76 and costs $10.59. | Hardcover fixed branch through 108; after normalization, 5.65 + 110 times 0.012 = 6.97; premium uses 5.65 + 76 times 0.065 = 10.59; official KDP hardcover cost source. | Hardcover never uses paperback constants. Premium color has no short fixed-cost branch. |
-| FF-006 | Paperback page limits at raw 23, 24, 828, and 829 for a normal black-and-white trim; standard color at 72 and 71; hardcover at 75, 74, 550, and 551; unavailable large trim/profile combination. | Raw 23 normalizes to effective 24 and is valid; raw 24 and 828 are valid; raw 829 normalizes to 830 and is invalid. Standard color 72 is valid and 71 normalizes to 72, while values whose effective count is below 72 remain invalid. An unavailable combination is invalid before cost calculation. | Official KDP paperback submission source and the shared lib/kdp/specs.ts catalog. | Limit validation uses the effective even page count; distinguish a raw odd count that rounds into range from an effective count outside range. |
-| FF-007 | Derived printing costs of $4.60, $5.00, and a cost producing exactly $9.99 under the piecewise floor. | $4.60 floors at $9.20. $5.00 has a 50% candidate of $10.00, so it uses the 60% band and floors at $9.99. An exact $9.99 floor remains $9.99. | ceil(cost / 0.50) first, then max($9.99, ceil(cost / 0.60)); official KDP paperback cost and royalty sources. | The floor is a ceiling operation in cents, and no displayed floor can under-cover cost. |
-| FF-008 | eBook file sizes 0.001, 1, 3, 5, 10, and 650 MB with the 70% option. | Delivery costs are $0.01, $0.15, $0.45, $0.75, $1.50, and $97.50 respectively. Five MB at $9.99 yields royalty $6.47. | ceil(MB times 1024) KB, then round(KB times $0.15 / 1024) with $0.01 minimum; round(($9.99 - $0.75) times 70%) = $6.47; official KDP delivery source. | Delivery is rounded in cents and subtracted before applying the eligible 70% rate. |
-| FF-009 | eBook 70% at $2.98, $2.99, $12.99, $13.00; 35% floor sizes just below 3 MB, at 3 MB, just below 10 MB, and at 10 MB. | $2.98 and $13.00 use effective 35% with one fallback warning. $2.99 and $12.99 use effective 70%. 35% floors are $0.99, $1.99, and $2.99 for the three file-size bands. | Official KDP eBook pricing and delivery sources plus the implementation-report band table. | 70% eligibility is inclusive. A fallback remains a valid result but never displays a false 70% rate. |
-| FF-010 | Positive royalty $1.39, target $1,000; zero target; positive target with royalty zero or negative. | Positive target returns ceil(100000 / 139) = 720 copies. Zero returns 0. Positive target with non-positive royalty returns unknown with a reason. | Integer-cent target division from the implementation report. | Blank target is omitted. Never return infinity, a negative count, or a rounded-down count. |
-| FF-011 | Candidate price sets with duplicates, such as floor equal to selected price, selected equal to $9.98, and eBook candidates containing $2.99 twice. | Return unique ascending valid rows. Each row has its own effective rate, cost or delivery, royalty, and margin. Omit candidates outside the active maximum or floor. | uniquePricePoints behavior required by the implementation report comparison equation. | Row identity is price in cents; no duplicate formatted price or stale selected row. |
-| FF-012 | Money values with one, two, and more than two decimal places; margins and ACoS with whole, one-decimal, and repeating percentages. | Money displays two decimals. Rates display whole percentages. Margin and ACoS display one decimal place. Formula version is kdp-us-amazon-com-2026-09-16-v1 in the result details, with source date Sep 16, 2026. | Rounding and versioning section of implementation-report.md and official KDP source links. | Keep raw calculation precision until the currency boundary, then use the specified display precision. |
-| FF-013 | Valid result with blank target, zero target, and positive target; valid result with negative royalty. | Blank omits the target region. Zero shows 0 copies. Positive target uses displayed royalty cents. Negative royalty shows no positive ad headroom and no ACoS. | Invalid, unknown, absent, and partial state contract. | Optional data stays absent, unknown stays distinct from zero, and no result invents a forecast. |
-
-## Test plan
-
-### Pure engine and unit tests
-
-- tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs: add table-driven tests for EC-003 through EC-016 and EC-033. Use deterministic inputs, integer-cent assertions, exact issue codes, source arrays, rate branches, invariants, and FF-001 through FF-013. Include a property-style loop over supported trims and profiles to verify every valid page-limit edge and that every valid price floor covers the rounded integer-cent cost.
-- tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs: assert that invalid input always returns status invalid, values null, and no plausible partial economics. Assert that valid comparison rows are sorted, unique, within the active price range, and independently recalculated.
-- tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs: test formatKdpMoney and formatKdpPercent, target ceiling math, odd-page normalization, eBook kilobyte rounding, and non-positive economics. Avoid snapshot-only coverage because the risk is numeric truth.
-
-### API or route tests
-
-- No API or upstream-resolution test is required. The calculator is local and synchronous, has no fetch path, and does not accept remote pricing data. EC-017 is covered through deterministic local-constant failure or static source policy instead of a network mock.
-- tests/pages/kdp-royalty-calculator/page.test.mjs: verify the flat route source, shared server shell, engine isolation from browser globals and network calls, no page-owned metadata or publication mutation, and the unpublished manifest.
-
-### Browser tests
-
-- tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts: exercise the complete state matrix: clean, valid print, valid eBook, 70% fallback, invalid, non-positive royalty, positive target, blank target, copy success, copy failure, engine failure, retry, reset, format changes, refresh, and back/forward.
-- tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts: assert result order, one lead, receipt ownership, semantic table headers and selected row, source details, no duplicate standalone facts, and no omitted recovery message.
-- tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts: use mouse and keyboard for all actions. Assert first-invalid focus, result-heading focus, reset focus, live announcements, labels, descriptions, field errors, aria-invalid, reduced-motion behavior, and clipboard permission handling.
-- tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts: measure bounds and document overflow at 320, 375, 390, 760, 959, 960, and desktop widths in dark and light themes. Verify only the comparison table scrolls and that long values wrap.
-- tests/pages/tools/shared/tool-workbench.spec.ts: retain the shared workbench and no-document-overflow regression for the new route when it joins the representative tool coverage.
-
-### Static and SEO tests
-
-- tests/pages/kdp-royalty-calculator/page.test.mjs: validate the ownership manifest, route path, unpublished state and reason, referenced docs and tests, absence of page-owned SEO logic, absence of runtime persistence, and no broad global CSS change.
-- tests/stack127/seo.spec.ts: verify that the unpublished route is blocked by the deliberate local/production policy, absent from the sitemap, and not made indexable by a query-param variant. If the shared SEO policy renders an explicit noindex page instead of a 404, assert that exact policy rather than accepting both silently.
-- npm run test:static: verify route ownership, manifest references, publication-state syntax, content-doc ownership, and architecture policy.
-- Final handoff order: focused engine tests, focused route test, browser route spec, shared tool regressions, npm run test, node skills/stack127/stack127-tool-build/scripts/validate-pipeline.mjs content_docs/kdp-royalty-calculator --stage=test, then the full npm run quality gate. The full quality gate is a build-stage handoff check, not a reason to weaken this contract.
-
-## Manual verification
-
-| View/state | Viewport/theme | Exact check | Pass condition |
-| --- | --- | --- | --- |
-| Clean form | 1440px and 390px, dark and light | Identify the first decision, active fields, one primary action, and the absence of a result. | Format is first, only compatible controls are visible, Calculate royalty is the clear commit action, and no empty result shell competes with it. |
-| Valid print result | 1440px and 390px, dark and light | State what the lead answers, what the receipt answers, what the floor and margin answer, and where repeated prices are compared. | The selected royalty is the first answer. Each supporting region has one question and no duplicate standalone metric. |
-| eBook fallback | 390px, dark and light, with 70% selected outside its band | Check the effective rate, warning meaning, source details, and recovery path. | The result clearly uses 35%, the warning is readable without color, and changing price or rate remains easy. |
-| Non-positive royalty and target | 1440px and 390px, dark and light | Enter a positive target with zero or negative royalty and inspect ad headroom and target copy. | No negative ad budget, negative ACoS, infinity, or fake copy count appears. The limitation explains what to change. |
-| Invalid recovery | 320px and 390px, both themes, keyboard only | Submit multiple invalid values and observe focus, field errors, summary, and stale-result removal. | The first invalid field receives focus, errors are associated and readable, the result is absent, and entered values remain available for correction. |
-| Clipboard failure | 390px, both themes | Deny clipboard access and activate Copy royalty. | The result stays intact, no false success appears, and the user receives a concise manual-copy recovery. |
-| Long table and details | 320px, 760px, and desktop, both themes | Inspect the comparison table, source disclosure, long amounts, and official links. | Only the table scrolls, headers remain understandable, text wraps, and evidence follows the economics without a second result hierarchy. |
-| Unpublished route | Server response and browser at desktop and mobile | Open the clean route and a query-param variant, then inspect sitemap and page source. | The route follows the deliberate unpublished 404 or noindex policy, stays out of the sitemap, and no query parameter publishes it. |
-
-## Test data and mocks
-
-- Use a fixed formula version kdp-us-amazon-com-2026-09-16-v1, source date 2026-09-16, and the official KDP URLs in the implementation report. Do not use the current date or live price scraping in assertions.
-- Keep fixtures grouped by branch: regular and large paperback, each paperback profile, regular and large hardcover, eBook delivery, eBook floors, print threshold, floor solver, target math, invalid states, and formatted output. Give every fixture a stable FF ID or EC ID.
-- Use the exact trim and page-limit catalog from lib/kdp/specs.ts, including 5x8, 6x9, 6.14x9.21, 8.25x11, 8.27x11.69, and 8.5x11 edge cases. Do not invent unsupported trims or profiles.
-- Browser tests should mock only clipboard permission and deterministic local failure seams. They must fail if the page calls fetch, writes storage, changes history, sends analytics, or fetches pricing rules.
-- Use long values $250.00, $200.00, $1,000,000.00, 650 MB, and the longest supported labels. Use malicious strings such as <img src=x onerror=alert(1)>, javascript:alert(1), __proto__, control characters, and oversized decimal text only in browser injection checks.
-- Do not mock Amazon responses because v1 has no upstream request. A source-data failure fixture must remove or mismatch local versioned constants and assert a closed failure, not a guessed answer.
-- Clipboard success must capture the exact text written. Clipboard failure must reject the write or omit the API. Reset and refresh tests must inspect localStorage, sessionStorage, cookies, URL, history, and analytics spies after every state transition.
-
-## Plan completion criteria
-
-- [x] Every P0 and P1 case has an expected outcome, requirement ID, test level, file owner, and deterministic fixture or manual rationale.
-- [x] Every formula branch and invariant has an oracle fixture specification.
-- [x] Every UI- requirement covers hierarchy, distinct result purpose, truthful geometry, removal guards, and responsive behavior where applicable.
-- [x] The build stage has an ordered focused-test plan and a full-quality-gate plan.
-
-## Open questions and blockers
-
-- None. The product and interface contracts are ready and provide the formula, scope, hierarchy, states, privacy boundary, responsive behavior, and publication decision needed for implementation and test execution. Any failing case above is an implementation defect to fix against those contracts, not a new product decision.
-
-+
-## Edge-case matrix
-
-| ID | Priority | Category | Setup/input | Expected system outcome | Expected user experience | Side effects allowed | Test level/file | Requirement |
-| --- | --- | --- | --- | --- | --- | --- | --- | --- |
-| EC-001 | P0 | Input grammar | Submit with blank, whitespace, letters, punctuation, 14,99, $14.99, 1e2, +14.99, -1, 0014.99, 14.9, and 14.990 in list-price and money fields. Use decimal text in page-count and file-size fields. | Canonical positive decimal values may normalize to cents where the control grammar permits them. Blank, whitespace, signs that produce a negative value, locale separators, currency symbols, exponent notation, units, and other non-decimal text produce typed field errors. Page count accepts only a whole positive value. The engine never throws. | Preserve the edited value until submit, mark the invalid field, state the allowed input in the field error, remove any prior result, and focus the first invalid field on submit. | No request, URL update, storage write, analytics event, or clipboard access. | Browser input matrix in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts; pure parser assertions in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs. | R12, UI-006, UI-007 |
-| EC-002 | P1 | Input grammar | Leave monthly target blank, enter 0, 0.00, a positive decimal, a negative value, and a non-numeric string. | Blank omits the target result. Zero produces 0 copies. A positive target is retained for later division. Negative and malformed targets are invalid. | Blank is quiet and normal. Invalid target input gets a local field error without clearing other form values. | No request, URL, storage, or analytics change. | Unit plus browser state test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R16, UI-007 |
-| EC-003 | P0 | Input robustness | Call the engine with NaN, Infinity, -Infinity, Number.MAX_VALUE, negative zero, negative page count, zero file size, and a non-safe page integer. | Return status invalid with values null, a field-specific issue, and no thrown exception. Do not coerce overflow or non-finite values into a plausible scenario. | If reached through the form, show recovery beside the responsible field and no result region. | No console error, request, URL, storage, or analytics payload. | Pure Node test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs. | R12, UI-007 |
-| EC-004 | P0 | Configuration | Use unsupported format, trim, binding, interior, paper, eBook royalty option, and a paperback-only trim with hardcover. Use a valid-looking profile whose trim catalog has no page-limit branch. | Reject each unsupported enum or combination before calculation. Do not use a neighboring cost branch. Return a typed issue with the affected field or configuration. | Keep entered compatible values visible, identify the unsupported choice, clear the result, and provide a compatible selection. | No request, result, or side effect. | Unit fixture matrix in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs; control filtering in the browser spec. | R2, R3, R12, UI-006 |
-| EC-005 | P0 | Page boundaries | For each applicable paperback trim and profile, test minimum, minimum minus one, maximum, maximum plus one, standard-color 72-page minimum, and unavailable 8.27x11.69 standard-color. Test hardcover 75 and 550 pages with 74 and 551. | Accept the documented inclusive limits. Reject one page outside them and unavailable combinations with status invalid. The selected price must not be calculated from an invalid page count. | Show the exact allowed range near the page field, remove any stale result, and focus page count first when it is the first error. | No request, URL, storage, or analytics change. | Pure table-driven test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs; invalid recovery in browser spec. | R3, R4, R12 |
-| EC-006 | P0 | Page normalization | Use odd print counts at 23, 24, 25, 109, 110, 111, 599, 600, and a maximum odd count such as 827 where the selected profile allows it. | Normalize to 2 times ceil(pageCount / 2) before limits and cost. Expose both entered and effective counts when they differ. Reject when the normalized count exceeds the maximum, even if the raw odd count does not. | The receipt explains the even-page adjustment in one short note. Invalid normalization leaves no economics result. | No request, URL, storage, or analytics change. | Pure normalization and boundary fixtures in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs; receipt and error in browser spec. | R4, R5, R6, R12 |
-| EC-007 | P0 | Paperback formula | Cover regular and large trims for black and white, cream, groundwood, standard color, and premium color at every fixed/per-page branch boundary and a long valid book. | Match the versioned fixed and per-page costs in FF-001, FF-003, and FF-004. Use fixed-only rules through the documented boundary, including the overlapping 110-page black-ink label, then the per-page branch after normalization. Keep paperback cost data separate from hardcover data. | The receipt labels printing cost and, when needed, fixed cost and page cost. The lead royalty uses the selected price and effective rate, not a cost from another profile. | No request or runtime pricing fetch. | Pure fixture matrix in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs. | R5, R13 |
-| EC-008 | P0 | Hardcover formula | Cover regular and large trims, black and white or cream, premium color, 108, 109, 110, and long valid page counts. | Match FF-005. The fixed black-ink branch applies through 108 effective pages. Premium color always uses its per-page branch. Hardcover trim and profile tables never use paperback constants. | Show a hardcover receipt with the selected printing cost and no eBook delivery row. | No request or runtime pricing fetch. | Pure fixture matrix in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs. | R6, R13 |
-| EC-009 | P0 | Rate boundary | Submit the same valid print scenario at $9.98, $9.99, $9.989, $9.991, $0.01, and $250.00. | Parse to integer cents. Use 50% for $9.98 and below, 60% for $9.99 and above. Values that round to the same cents produce the same branch. Enforce the $250.00 maximum. | Show the effective rate beside the lead and in each comparison row. Do not label $9.98 as 60% or $9.99 as 50%. | No request, URL, storage, or analytics change. | Unit threshold tests and browser result assertion in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R7, R14 |
-| EC-010 | P0 | Price floor | Exercise a printing cost whose 50% floor is inside the 50% band, one whose 50% floor crosses $9.99, and a floor exactly at $9.99. Test one cent below the calculated floor, exactly at it, one cent above it, and above $250.00. | Compute ceil(integer-cent cost / 0.50) first. If that result is above $9.98, compute ceil(integer-cent cost / 0.60) and clamp to $9.99. The displayed floor covers the rounded integer-cent printing cost. A price below the floor blocks the calculation according to the ready product contract. | State the required minimum and keep the result region absent for a blocked price. Do not show a plausible royalty beside a below-floor input. | No request, URL, storage, or analytics change. | Pure floor fixtures in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs; browser invalid-state assertion. | R8, R12 |
-| EC-011 | P0 | eBook delivery | Test file sizes 0.001, 1, 3, 5, 9.999, 10, 650, and a value just above 650 MB. | Convert with ceil(MB times 1024) kilobytes. Apply $0.15 per MB, round delivery to cents, and clamp it to at least $0.01. The 70% equation subtracts delivery. The 35% equation does not. Reject values above 650 MB. | Show rounded file size and delivery cost only when relevant. Never subtract delivery from a 35% royalty or silently accept an oversized file. | No request, URL, storage, or analytics change. | Unit delivery fixtures in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs. | R9, R11 |
-| EC-012 | P0 | eBook rate fallback | Submit 70% eBook scenarios at $2.98, $2.99, $12.99, $13.00, and a 35% scenario at the same prices. | Effective 70% applies only inclusively from $2.99 through $12.99. An out-of-band 70% selection remains a valid calculation at 35% and returns one warning. The 35% selection has no fallback warning. | Keep the chosen option visible, show the effective 35% rate clearly beside the result, and explain the band once. | No request, URL, storage, or analytics change. | Unit band fixtures and browser warning assertion in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R9, R10, UI-007 |
-| EC-013 | P0 | eBook floor and maximum | Test 35% prices at file sizes just below 3 MB, exactly 3 MB, just below 10 MB, exactly 10 MB, and 650 MB. Test $0.98, $0.99, $1.98, $1.99, $2.98, $2.99, $200.00, and $200.01. | Use floors $0.99, $1.99, and $2.99 for the three file-size bands. Enforce the $200.00 maximum and the selected floor before calculating. | State the exact file-size-dependent minimum and keep the result empty for below-floor or above-maximum prices. | No request, URL, storage, or analytics change. | Pure eBook floor matrix plus browser recovery test. | R11, R12 |
-| EC-014 | P1 | Target math | Use a positive target with positive royalty, a target whose cents divide evenly, a target just over a multiple, a blank target, and zero target. | Use ceil(target cents / displayed royalty cents). Return exact zero for a zero target, omit the result for blank, and never use a floating-point remainder to lower the copy count. | Keep target math separate from the lead royalty. Show the target amount and copies only when requested. | No request, URL, storage, or analytics change. | Unit economics fixtures in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs; browser result-region assertion. | R16 |
-| EC-015 | P0 | Non-positive economics | Use a valid scenario with zero royalty and another with negative royalty. Enter a positive monthly target in both. | Preserve the exact royalty. Set break-even ad spend to zero or an explicit no-positive-headroom state. Omit ACoS. Return target copies as unknown with a reason when the target is positive. Never return infinity, a negative ad budget, or a negative ACoS. | Make the limitation readable without relying on color. Keep the form usable so the author can change price or format and recalculate. | No request, URL, storage, or analytics change. | Unit economics fixtures and browser state test. | R15, R16, UI-007 |
-| EC-016 | P1 | Comparison output | Choose a selected price equal to the floor, $9.98, $9.99, $12.99, or a boundary value so candidate rows duplicate. Include candidate rows outside the format's valid range. | Build unique rows in ascending order from the format's floor, selected price, and exact rate boundaries. Recalculate rate, cost or delivery, royalty, and margin for each row. Omit invalid candidates. Do not repeat a row or use a stale selected-price value. | Use one semantic table with a clear selected-row marker. Keep table headers in the accessibility tree and do not add duplicate metric cards. | No request, URL, storage, or analytics change. | Unit output fixture and browser table test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R14, UI-002, UI-003 |
-| EC-017 | P0 | Data integrity | Run with missing or mismatched versioned constants, a changed formula version, or an unavailable cost table through a deterministic fault-injection seam or static fixture. | Fail closed with values null, a short source-data error, and no old result. The client does not fetch replacement pricing rules at runtime. | Keep inputs intact, leave Calculate royalties available for retry, announce the failure, and do not replace the missing rule with a guessed fallback. | No network request, URL update, storage write, or analytics payload. | Static policy and deterministic failure test in tests/pages/kdp-royalty-calculator/page.test.mjs plus the engine test if a fault seam exists. | UI-007, R17 |
-| EC-018 | P1 | Stale state | Calculate a valid result, then edit format, trim, profile, pages, price, file size, royalty option, or target one at a time. | Clear the full old result immediately on every result-driving edit. Clear only resolved field errors and preserve the edited value. Do not recalculate implicitly. | Keep focus in the edited control and announce that the scenario needs calculation. No old royalty, table, warning, or target remains visible. | Local React state only. | Browser interaction test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R12, R18, UI-007 |
-| EC-019 | P1 | Submit and result focus | Submit a valid paperback, hardcover, and eBook scenario with mouse and keyboard. | Run the synchronous engine once, replace the result, and place focus on a focusable result heading after the result DOM exists. Announce the selected royalty once. | The result order is lead, receipt, floor and margin, comparison, ad headroom, optional target, and details. The primary answer is not hidden below the table. | One local calculation. No URL, storage, network, or analytics event. | Browser interaction and accessibility test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R13, R18, UI-001, UI-007 |
-| EC-020 | P1 | Invalid submit | Submit with multiple errors, including a malformed price, incompatible profile, out-of-range pages, below-floor price, or invalid eBook size. | Return typed errors and no values. Order errors by source order and do not leave a previous result. The first invalid active field is the recovery target. | Show field-level errors with programmatic association, one concise error summary, focus the first invalid field, and retain all entered values. | No request, URL, storage, or analytics change. | Browser validation test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R12, UI-007 |
-| EC-021 | P1 | Conditional controls | Start with paperback, change to hardcover, then eBook, then back to print. Switch print interior and inspect paper options. | Expose only compatible fields and options. Reset incompatible trim, interior, paper, page, eBook size, and royalty-option values to branch defaults. Clear results and errors. | Keep the selected format in focus, reveal the new controls in source order, and announce the new scenario fields without moving focus unexpectedly. | Local React state only. | Browser interaction matrix in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R2, UI-006 |
-| EC-022 | P1 | Reset | Activate Reset from clean, valid, invalid, warning, non-positive, copied, and expanded-details states. | Restore format-specific defaults, blank optional target, and the initial clean result state. Clear issues, warnings, status text, copied state, and disclosure state as specified by the component contract. | Focus Format and announce that defaults were restored. Do not change the URL or reload the page. | Local React state only. | Browser interaction test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R18, UI-007 |
-| EC-023 | P1 | Submission concurrency | Press Calculate with Enter and click rapidly, double-click the button, and submit while a render boundary or test scheduler is busy. | A synchronous calculation produces one committed result and never duplicates rows, status announcements, or clipboard actions. The button retains a stable hit area and does not expose a fake long-running request. | Keep the action usable and avoid duplicate announcements or layout jumps. | At most one local calculation per committed submit; no network or storage. | Browser interaction test and performance assertion in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | UI-007, UI-004 |
-| EC-024 | P1 | Copy success | Submit a valid result and activate Copy royalty with mouse, Enter, and Space while the clipboard permission succeeds. | Write only the documented summary fields: format, selected list price, royalty, effective rate, and printing or delivery cost. Preserve line breaks and two-decimal money formatting. | Announce Royalty copied once, keep focus on the copy action, and leave the result unchanged. | Clipboard write only after explicit activation. No URL, storage, analytics, or hidden input data. | Browser clipboard test with permission mock in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R13, R20, UI-007 |
-| EC-025 | P1 | Copy failure | Submit a valid result, deny clipboard permission, throw from navigator.clipboard.writeText, or run without a clipboard API. | Keep the result and copy control available. Do not claim success, leak the exception, or make clipboard failure invalidate the calculation. | State that copying failed and tell the user the result remains available to copy manually. Keep focus and do not move the result. | No successful clipboard write, URL, storage, network, or analytics event. | Browser permission and API-absence test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | UI-007, UI-008 |
-| EC-026 | P1 | Accessibility semantics | Inspect labels, required states, fieldsets, descriptions, error associations, table headers, result heading, copy/reset buttons, and live regions. Navigate without a pointer. | Every active control has an accessible name and compatible group semantics. Invalid fields expose aria-invalid and their error. Result and status announcements use the intended live semantics. Table headers and row relationships are semantic. | Tab order follows form order, then result order. Keyboard users can choose formats and rates, submit, reset, copy, inspect details, and scroll the table. | No focus trap, automatic scroll, or color-only status. | Browser accessibility assertions in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts; shared workbench regression in tests/pages/tools/shared/tool-workbench.spec.ts. | R12, R18, UI-001, UI-003, UI-007 |
-| EC-027 | P1 | Theme and zoom | Inspect clean, valid, warning, invalid, negative, copied, and table states in dark and light themes, with reduced motion and 200% and 400% browser zoom. | Preserve contrast, readable status words, visible focus, stable result hierarchy, and no animated geometry requirement. | Users can identify warning, failure, selected row, and no-headroom states without color alone. Long labels wrap without clipping. | No theme-specific data or state. | Browser visual and accessibility checks in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts; manual comprehension review. | UI-004, UI-007, UI-008 |
-| EC-028 | P1 | Responsive layout | Test 320, 375, 390, 760, 959, 960, and desktop widths with long labels, $250.00, $1,000,000.00, 650 MB, long errors, and the five-column comparison table. | Stack at narrow widths in DOM order. Keep form controls and source links inside the viewport. Only the labeled comparison-table viewport may scroll horizontally. No document-level horizontal overflow. | Buttons retain comfortable hit targets, long error text wraps, table headings remain available, and result lead remains quick to find. | No viewport, URL, or input change. | Responsive browser test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts and shared workbench test. | R19, UI-004 |
-| EC-029 | P0 | Security and privacy | Paste HTML, script-like strings, URL-like text, __proto__, oversized decimal strings, and control characters into every text-capable field and into a hostile clipboard response. | Reject invalid numeric input before calculation. Render no input as HTML, execute no script, create no URL, mutate no prototype, and avoid unbounded parsing or DOM growth. Clipboard content is treated as text. | Show an ordinary validation error and keep the interface responsive. Never echo dangerous text into a result or status as executable markup. | No request, storage, analytics payload, or navigation. | Static source review plus browser injection checks in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | R12, R20, UI-007 |
-| EC-030 | P0 | URL and storage | Inspect the URL, history, query string, hash, localStorage, sessionStorage, cookies, and analytics calls through edit, submit, copy, reset, refresh, and back/forward. | The clean canonical route remains unchanged. No scenario state or result is serialized, restored, or sent to analytics. Back and forward do not create an artificial result state. | A refresh starts clean with defaults. Users do not get a shareable URL that implies support the tool does not have. | None. An explicit copy action may use the clipboard only. | Browser history and side-effect test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts; static source assertions in page.test.mjs. | R20, UI-005 |
-| EC-031 | P0 | SSR and publication | Request the clean route with JavaScript disabled or before hydration, inspect the server HTML, then run the unpublished-route SEO checks and a query-param variant. | The route uses the shared server page and server-rendered tool content. It owns no metadata, canonical, robots, sitemap, or JSON-LD logic. While unpublished, the route is blocked with the repository's deliberate 404 or noindex behavior, excluded from the sitemap, and not made public by query parameters. | The publication reason remains in the manifest, and no client-only result is presented as server truth. Fixed scope and source details remain accurate when the page is intentionally visible in a local preview. | No publication-state write or runtime price request. | Route and SEO tests in tests/pages/kdp-royalty-calculator/page.test.mjs and tests/stack127/seo.spec.ts. | R1, R21, UI-005, UI-008 |
-| EC-032 | P1 | Ownership and architecture | Inspect the page manifest, route files, engine imports, global CSS, and public registry references. | The flat route has one ownership manifest, the manifest state is unpublished, docs and tests are listed, calculations stay in lib/kdp/royalty.ts, and the route adds no page-owned SEO metadata or global selectors. | No user-visible route is published as a side effect of test or build work. | No manifest, database, script, or publication mutation during these tests. | Static Node test in tests/pages/kdp-royalty-calculator/page.test.mjs plus npm run test:static. | R21, UI-008 |
-| EC-033 | P2 | Performance | Run 10,000 deterministic valid scenarios across print and eBook branches, including maximum file size and long page counts, on a mid-range test runner. Inspect render count and layout shift for one browser submission. | Each pure calculation completes within the implementation target of 50 ms for one submission. The suite remains deterministic. One submit does not add duplicate result regions or cause measurable page-wide layout shift. | The user sees a synchronous answer without a spinner, fake progress, or a button that changes width. | CPU and test memory only; no request or storage. | Benchmark/unit assertion in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs and browser observation in the route spec. | UI-004, UI-007 |
-| EC-034 | P1 | Evidence and formatting | Inspect a valid print result, a valid eBook result, fallback warning, and details disclosure. Check two-decimal money, whole-number rates, one-decimal margin and ACoS, formula version, source date, Amazon.com, USD, and standard distribution. | Format values once according to the display contract. Source links point to official KDP pages. Evidence appears after the economics and does not repeat the lead as a competing card. | The user can tell what the number means and which rule set supports it without reading a second result. | Official source links may navigate in a new context. No scenario data is sent. | Browser result assertion and static source review in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts and page.test.mjs. | R1, R13, R17, UI-008 |
-| EC-035 | P1 | Refresh and malformed state | Open the clean route, refresh after a result, append unsupported query or hash state, and use back/forward after edits. | Start clean with branch defaults and no restored values. Ignore unsupported query and hash input for calculation; do not show a stale or partial result. | No load announcement is needed. The form remains usable and the URL policy is clear. | No storage read or write, URL rewrite, request, or analytics event. | Browser state test in tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts. | UI-005, UI-007 |
-| EC-036 | P1 | Result hierarchy and comprehension | Review clean, valid, fallback, non-positive, and long-table states at desktop and narrow widths without reading internal implementation reports. Name the user question answered by each region and identify repeated facts or removable UI. | One lead answers the selected-sale question. Receipt answers deductions. Floor and margin answer price coverage. Table answers boundary comparison. Ad headroom answers spend ceiling. Target answers unit math. Details answer scope and source. No gauge, timeline, allocation bar, duplicate metric card, or unnecessary result region appears. | A reviewer can state the answer and purpose of each region in a two-second scan. Duplicate formatted facts appear only in the table's row schema or the required lead detail. | Human review only for comprehension; repeatable checklist recorded below. | Manual visual verification at locked viewports and both themes. | R13, R14, R19, UI-001, UI-002, UI-003, UI-004, UI-008 |
-| EC-037 | P1 | Control mode and hidden-state recovery | Calculate an ordinary print and eBook scenario, open and close Calculation details, then change format or price to an invalid dependent value and submit. Repeat each valid scenario with details open and closed. | This is disclosure mode, not Basic/Advanced mode. The same normalized input produces equivalent royalty, comparison rows, and warnings in both evidence states. Format-specific fields remain explicit; an invalid active field clears stale economics and cannot be hidden by the collapsed details. | The details trigger retains focus and does not re-announce the lead. Branch changes reveal the needed controls, focus the first invalid field on submit, and keep entered values for recovery. | No URL, storage, request, or analytics side effect. Clipboard is allowed only for explicit Copy royalty. | Pure parity plus Browser disclosure/branch recovery test in `tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs` and `kdp-royalty-calculator.spec.ts` | R2, R12, R18, UI-009 |
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-# Implementation report: KDP royalty calculator
-
-Status: ready
-Tool: KDP royalty calculator
-Route: `/kdp-royalty-calculator`
-Depends on: `competitive-report.md`
-Contract type: formula
-
-## Product decision
-
-- Primary user: A self-publishing author choosing a US KDP list price for a print book or Kindle eBook.
-- Job: Compare a list price with KDP costs and leave with royalty per sale, the minimum viable price, ad headroom, and the sales needed for a monthly target.
-- Product thesis: The planner earns preference by showing the current rate band and a small cost receipt beside the answer, instead of returning one opaque royalty number.
-- Evidence: `Search intent`, `User pain evidence`, `Technical truth to verify`, `Comparison matrix`, and `Formula and data disagreements` in `competitive-report.md`.
-
-## Scope
-
-### Table stakes
-
-- Calculate paperback, hardcover, and Kindle eBook scenarios.
-- Use current Amazon.com printing costs, royalty rates, price limits, and eBook delivery rules.
-- Show printing cost or delivery cost, the selected-price royalty, the minimum allowed price, and the royalty margin.
-- Show maximum break-even ad spend per sale, break-even ACoS, and optional copies for a monthly income target.
-- Show a compact price comparison that exposes the print rate threshold or the eBook 70% band.
-- Keep Expanded Distribution out of every result.
-
-### Launch differentiators
-
-- Use a dated US source contract and show the applicable rate beside the selected price.
-- Keep the calculation receipt visible: fixed cost, page cost, delivery cost where applicable, rate, and royalty.
-- Treat a selected eBook 70% option outside its price band as a 35% calculation with a clear warning, rather than silently applying 70%.
-- Explain ad headroom as a break-even ceiling, not as a recommended advertising budget.
-- Use a small comparison table with the exact price boundary rows that change the answer.
-
-### Deferred
-
-- Non-US marketplaces and currencies.
-- VAT, GST, withholding tax, price matching, refunds, and promotional pricing.
-- Expanded Distribution and other distribution channels.
-- KDP API or live price scraping.
-- Demand, sales, ranking, Kindle Unlimited, or advertising performance forecasts.
-- Saved scenarios, shareable URL state, and account-linked book data.
-
-### Non-goals
-
-- The result is not a guarantee of the royalty Amazon will report for every order.
-- The result is not net profit after editing, cover design, taxes, refunds, or ad spend.
-- The result does not recommend a book price or predict how many books will sell.
-- The result does not model a customer's discounted or price-matched sale price.
-
-## Formula and data contract
-
-### Inputs and normalization
-
-The launch scope is Amazon.com, USD, and standard Amazon distribution. Marketplace and currency are fixed display facts, not user inputs.
-
-| Input | Type and unit | Default | Valid range | Normalization |
-| --- | --- | --- | --- | --- |
-| `format` | enum | `paperback` | `paperback`, `hardcover`, `ebook` | Canonical string. Determines the remaining fields. |
-| `trimSizeId` | enum, inches | `6x9` for print | Official US KDP trim IDs supported by the selected binding | No free-text dimensions. Derive regular or large trim class from the preset. |
-| `printProfile` | enum | `bw-white` | `bw-white`, `bw-cream`, `groundwood`, `standard-color`, `premium-color` for paperbacks; `bw-white`, `bw-cream`, `premium-color` for hardcovers | Filter options by binding. `bw-white` and `bw-cream` share the black-ink cost branch. |
-| `pageCount` | integer pages | `300` | The selected trim and profile's KDP page range | Round up to the next even page for `effectivePageCount`; reject if the normalized count is outside the KDP range. |
-| `listPriceUsd` | decimal USD | `$14.99` print, `$4.99` eBook | Greater than `$0.00`; print maximum `$250.00`; eBook maximum `$200.00`; also above the calculated floor | Parse to integer cents. Do not use floating point values for money. |
-| `ebookRoyaltyOption` | enum percent | `70` | `35` or `70`, eBook only | Apply 70% only inside the Amazon.com `$2.99` to `$12.99` band. Otherwise use 35% and return a warning. |
-| `ebookFileSizeMb` | decimal MB | `1` | Greater than `0` and no more than `650` | Convert with `fileSizeKb = ceil(fileSizeMb * 1024)`. Only eBooks use this field. |
-| `monthlyTargetUsd` | optional decimal USD | blank | Blank or `0` to `$1,000,000` | Parse to cents. Blank omits the unit target; zero returns zero copies. |
-
-The print preset catalog is shared with the KDP setup work. Paperback IDs are `5x8`, `5.06x7.81`, `5.25x8`, `5.5x8.5`, `6x9`, `6.14x9.21`, `6.69x9.61`, `7x10`, `7.44x9.69`, `7.5x9.25`, `8x10`, `8.25x6`, `8.25x8.25`, `8.27x11.69`, `8.5x8.5`, and `8.5x11`. Hardcover IDs are `5.5x8.5`, `6x9`, `6.14x9.21`, `7x10`, and `8.25x11`. A trim is regular when it is no more than 6.12 inches wide and 9 inches high. A trim is large when either dimension is greater than that limit.
-
-The page-limit table is part of the versioned data contract. For paperback trims from `5x8` through `8x10`, the maximums are 828 pages for black ink with white paper, 776 for cream, 812 for groundwood, 600 for standard color, and 828 for premium color. For `8.25x6` and `8.25x8.25`, the maximums are 800, 750, 784, 600, and 800. For `8.27x11.69`, the maximums are 780, 730, 764, standard color unavailable, and 590. For `8.5x8.5` and `8.5x11`, the maximums are 590, 550, 578, 600, and 590. All paperback profiles have a 24-page minimum except standard color, which has a 72-page minimum. Hardcover profiles use the supported trim IDs above and a 75 to 550 page range.
-
-### Equations or resolution order
-
-1. Resolve the binding, trim preset, print profile, and effective page count. `effectivePageCount = 2 * ceil(pageCount / 2)`. The input count and effective count remain available to the result so an odd count is not hidden.
-2. Reject an unavailable print profile or any effective page count outside the selected trim's current KDP range. eBooks skip trim, profile, and page-cost steps.
-3. Select the US Amazon.com printing branch. Parse list price and optional target amounts into integer cents. Compute each printing or delivery cost in cents, rounding the source cost expression to the nearest cent at that cost boundary; use those integer cents for royalty, floor, comparison-row, margin, and target calculations. Do not claim microdollar or unrounded-cost precision.
-4. For a paperback, use `fixedCost + (effectivePageCount * perPageCost)` with these current US values:
-   - Black ink with white or cream paper: regular trim is `$2.30` fixed through 110 pages, then `$1.00 + $0.012 * pages`; large trim is `$2.84` fixed through 110 pages, then `$1.00 + $0.017 * pages`. At the source table's overlapping 110-page label, the fixed-only note wins. The normalized even-page input makes the following branch begin at 112 pages.
-   - Groundwood: regular trim is `$2.23` fixed through 112 pages, then `$1.00 + $0.0114 * pages`; large trim is `$2.75` fixed through 112 pages, then `$1.00 + $0.0162 * pages`.
-   - Premium color: regular trim is `$3.60` fixed through 40 pages, then `$1.00 + $0.065 * pages`; large trim is `$4.20` fixed through 40 pages, then `$1.00 + $0.080 * pages`.
-   - Standard color: regular trim is `$1.00 + $0.0255 * pages`; large trim is `$1.00 + $0.0402 * pages`.
-5. For a hardcover, use `fixedCost + (effectivePageCount * perPageCost)` with these current US values:
-   - Black ink with white or cream paper: regular trim is `$6.80` fixed through 108 pages, then `$5.65 + $0.012 * pages`; large trim is `$7.49` fixed through 108 pages, then `$5.65 + $0.017 * pages`.
-   - Premium color: regular trim is `$5.65 + $0.065 * pages`; large trim is `$5.65 + $0.080 * pages`.
-6. For print, select the royalty rate by list price. Prices at or below `$9.98` use 50%; prices at or above `$9.99` use 60%. Round the rate-times-list-price result to integer cents, then subtract the integer-cent printing cost: `printRoyaltyCents = round(rate * listPriceCents) - printingCostCents`.
-7. For print, solve the minimum cost-covering price by band from the rounded integer-cent printing cost. Let `floor50 = ceil(printingCostCents / 0.50)`. If `floor50 <= $9.98`, use `floor50`. Otherwise let `floor60 = ceil(printingCostCents / 0.60)` and use `max($9.99, floor60)`. Reject the configuration if the floor is above `$250.00`.
-8. For an eBook, round the file size up to the nearest kilobyte and calculate `deliveryCost = max($0.01, roundToCents(fileSizeKb * $0.15 / 1024))`. Delivery cost is zero for the 35% option.
-9. For an eBook, the effective rate is 70% only when the selected option is 70% and the list price is from `$2.99` through `$12.99`, inclusive. Otherwise the effective rate is 35%. `ebookRoyalty = roundToCents(0.70 * (listPrice - deliveryCost))` for an eligible 70% sale, or `roundToCents(0.35 * listPrice)` for a 35% sale. VAT is zero in this US-only model.
-10. For an eBook, the 35% floor is `$0.99` below 3 MB, `$1.99` from 3 MB through less than 10 MB, and `$2.99` at 10 MB or more. The 70% floor is `$2.99`. Validate the selected price against the floor and the applicable maximum before calculating.
-11. For every valid selected price, calculate `royaltyMargin = royalty / listPrice`, `maxBreakEvenAdSpend = max(0, royalty)`, and `breakEvenAcos = royalty / listPrice` when royalty is positive. If royalty is zero or negative, report no positive ad headroom instead of a negative advertising budget.
-12. If `monthlyTargetUsd` is present and royalty is positive, calculate `copiesForTarget = ceil(monthlyTargetCents / royaltyCents)`. If the target is blank, omit the value. If the target is positive and royalty is not positive, return `unknown` with the reason that no positive per-sale royalty exists.
-13. Build the comparison rows from unique, valid prices in ascending order. Print rows use `[minimumPrice, selectedPrice, $9.98, $9.99]`. eBook rows use `[minimumPrice, selectedPrice, $2.99, $12.99]`. Each row recalculates the effective rate, cost or delivery, royalty, and margin at that price. Rows outside the format's valid price range are omitted, and duplicates are shown once.
-
-### Rounding, display, and versioning
-
-- Parse and display monetary inputs in integer cents. Compute and round each printing or delivery cost to integer cents, then use those cents for royalty, floor, comparison, margin, and target math. Use a ceiling to choose a price floor so the integer-cent floor covers the integer-cent printing cost; this contract has no precision below cents.
-- Display USD with two decimal places, rates as whole percentages, margin and ACoS to one decimal place, and page counts as whole numbers. Show the entered page count and effective even page count when they differ.
-- Recalculate each comparison row from integer-cent inputs and costs, with the same cent-rounding rules as the selected result. Use integer-cent royalty for monthly-copy division because KDP reports royalty money to cents in this model.
-- Store the constants and formula contract under `formulaVersion: "kdp-us-amazon-com-2026-09-16-v1"`. Show `KDP US rules checked Sep 16, 2026` beside the source links.
-- There is no URL state in v1, so there is no durable serialized-input contract. If shared URLs are added later, add `schemaVersion: 1` and include `formulaVersion` in the encoded state.
-
-### Invalid, unknown, absent, and partial states
-
-- Missing or malformed required input produces an inline field error and no result. The previous result is cleared as soon as an input changes, so stale economics never sit beside new inputs.
-- An unavailable profile, unsupported trim, page count outside the selected KDP range, price below the calculated floor, or price above the applicable maximum blocks calculation. Show the allowed range and the field that needs correction.
-- Selecting 70% for an eBook outside `$2.99` to `$12.99` is a warning, not a failed calculation. Calculate at 35% and state that the 70% option is not eligible at the selected price.
-- A blank monthly target is normal and removes only the copies-for-target row. A zero target returns zero copies. A positive target with zero or negative royalty returns `unknown`, not infinity or a negative copy count.
-- A zero or negative royalty shows no positive ad headroom and no ACoS percentage. Do not display a negative amount as spendable ad budget.
-- Missing versioned constants or a data-contract mismatch fails closed with no result and a short source-data error. The client does not fetch pricing rules at runtime.
-- Taxes, VAT, refunds, price matching, promotions, and actual marketplace discounts are unknown to this contract and stay outside the result rather than being estimated.
-
-### Assumptions and exclusions
-
-- The scenario represents an Amazon.com sale in USD through standard KDP distribution.
-- Print royalty is list-price royalty minus KDP printing cost. It is not author profit.
-- eBook VAT is modeled as zero. The 70% delivery rate is the current US `$0.15/MB` rule with KDP's nearest-kilobyte rounding and `$0.01` minimum.
-- The monthly target assumes every unit sells at the selected price and earns the selected per-sale royalty. It is a unit-math result, not a sales forecast.
-- The tool excludes Expanded Distribution even though Amazon documents a separate 40% formula.
-- The current source table shows an overlapping paperback black-ink boundary at 110 pages. The source's fixed-only note takes precedence, and the boundary is covered by a dedicated regression test.
-
-### Primary sources
-
-- [KDP paperback printing costs](https://kdp.amazon.com/en_US/help/topic/G201834340), checked 2026-09-16. Fixed and per-page US paperback costs, regular and large trim definitions, and paperback price-floor formula.
-- [KDP paperback royalties](https://kdp.amazon.com/en_US/help/topic/G201834330), checked 2026-09-16. 50% and 60% Amazon.com rate bands, royalty equation, and price limits.
-- [KDP hardcover printing costs](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H), checked 2026-09-16. Hardcover fixed costs, per-page costs, page range, and price limits.
-- [KDP hardcover royalties](https://kdp.amazon.com/en_US/help/topic/G77F3WPD3KQLJTFS), checked 2026-09-16. Hardcover royalty rate bands and royalty equation.
-- [KDP eBook list price requirements](https://kdp.amazon.com/en_US/help/topic/G200634560), checked 2026-09-16. Amazon.com eBook price bands and file-size-dependent 35% floors.
-- [KDP digital book pricing](https://kdp.amazon.com/en_US/help/topic/G200634500), checked 2026-09-16. 35% and 70% equations, US delivery rate, kilobyte rounding, and minimum delivery cost.
-- [KDP paperback submission guidelines](https://kdp.amazon.com/en_US/help/topic/G201857950), checked 2026-09-16. US trim catalog, page-count limits, and even-page rounding used by the shared print preset data.
-
-## User flow
-
-```mermaid
-flowchart TD
-  A["Clean tool"] --> B["Choose format"]
-  B --> C["Enter format-specific inputs"]
-  C --> D["Calculate royalties"]
-  D --> E{"Inputs valid?"}
-  E -->|"No"| F["Show inline recovery and keep result empty"]
-  F --> C
-  E -->|"Yes"| G["Compute current US KDP scenario"]
-  G --> H["Show royalty-first result"]
-  H --> I["Change an input"]
-  I --> J["Clear stale result"]
-  J --> C
-  H --> K["Reset defaults"]
-  K --> A
-```
-
-The calculation is local and synchronous. The primary action is explicit so an author can finish the form before reading the answer. A new input clears the old result. A valid submission replaces the result and moves focus to its heading. An invalid submission keeps the user in the form, focuses the first invalid field, and announces the error summary. Reset restores format-specific defaults. There is no URL or browser-storage restoration in v1.
-
-## Interface wireframes
-
-### Desktop: clean
-
-```text
-┌──────────────────────────────────────────────────────────────────────────────┐
-│ KDP royalty calculator                                      US Amazon.com USD │
-├───────────────────────────────┬──────────────────────────────────────────────┤
-│ SCENARIO                      │ RESULT                                       │
-│ Format   [Paperback       v]  │ Choose a format and enter a price.           │
-│ Trim     [6 x 9           v]  │ The answer appears here after calculation.   │
-│ Interior [Black / white   v]  │                                              │
-│ Pages    [300              ]  │                                              │
-│ List price [$14.99         ]  │                                              │
-│ Monthly target [optional   ]  │                                              │
-│                               │                                              │
-│            [Calculate royalties]                                            │
-└───────────────────────────────┴──────────────────────────────────────────────┘
-```
-
-### Desktop: valid result
-
-```text
-┌──────────────────────────────────────────────────────────────────────────────┐
-│ SCENARIO                       │ ROYALTY PER SALE                             │
-│ Format [Paperback]             │ $4.39                                       │
-│ Trim [6 x 9]  Pages [300]      │ 60% rate at $14.99                          │
-│ Interior [Black / white]       │                                              │
-│ Price [$14.99]                 │ COST RECEIPT                                │
-│ Target [$1,000]                │ Printing cost        $4.60                 │
-│ [Calculate royalties] [Reset]  │ Minimum price        $9.20                 │
-│                                │ Royalty margin       29.3%                  │
-│                                │                                              │
-│                                │ PRICE COMPARISON                            │
-│                                │ Price | Rate | Cost | Royalty | Margin      │
-│                                │ ... rows at floor, threshold, and choice   │
-│                                │                                              │
-│                                │ AD HEADROOM       MONTHLY TARGET             │
-│                                │ $4.39 per sale    228 copies                │
-│                                │ Break-even ACoS 29.3%                      │
-│                                │                                              │
-│                                │ KDP US rules checked Sep 16, 2026          │
-└──────────────────────────────────────────────────────────────────────────────┘
-```
-
-### Narrow mobile
-
-```text
-┌─────────────────────────────┐
-│ KDP royalty calculator      │
-│ US Amazon.com · USD         │
-├─────────────────────────────┤
-│ Format [Paperback       v]  │
-│ Trim   [6 x 9           v]  │
-│ Interior [Black / white v]  │
-│ Pages  [300              ]  │
-│ Price  [$14.99           ]  │
-│ Target [optional        ]  │
-│ [ Calculate royalties ]      │
-├─────────────────────────────┤
-│ ROYALTY PER SALE            │
-│ $4.39                       │
-│ 60% rate at $14.99          │
-│                             │
-│ Cost receipt                │
-│ Printing cost  $4.60        │
-│ Minimum price  $9.20        │
-│                             │
-│ Price comparison            │
-│ [horizontal table scroll]   │
-│                             │
-│ Ad headroom and target      │
-│ Source and assumptions      │
-└─────────────────────────────┘
-```
-
-### Error, loading, partial, and restored states
-
-```text
-Error:   Price      [ $5.00 ]  Price must be at least $9.20.
-         [Calculate royalties]  Result is removed. Focus goes to Price.
-
-Loading: [Calculating royalties...]  No stale result is shown during submit.
-
-Partial: eBook at $14.99 with 70% selected.
-         Result uses 35% and says the 70% band ends at $12.99.
-         A blank target omits the copies row.
-
-Restored: v1 has no URL or storage state. Refresh starts with defaults.
-```
-
-## Interaction contract
-
-| Event | UI response | Result state | Focus/announcement | URL/persistence |
-| --- | --- | --- | --- | --- |
-| Change format | Show only relevant fields and reset incompatible values | Clear result | Announce the new scenario fields without moving focus | No persistence |
-| Edit any input after a result | Clear field-level error and mark the scenario uncalculated | Remove stale result | Keep focus in the edited field | No persistence |
-| Submit valid form | Run the pure engine and render the answer hierarchy | Replace with valid result or a non-fatal rate warning | Move focus to the result heading and announce the selected royalty | No persistence |
-| Submit invalid form | Show concise field errors and allowed ranges | Keep result empty | Focus the first invalid field and announce the error summary | No persistence |
-| Choose 70% eBook outside its band | Keep the input, use the 35% fallback, and show the reason beside the result | Valid with warning | Announce the fallback once | No persistence |
-| Enter a positive monthly target with non-positive royalty | Keep cost result and show target copies as unknown | Valid with limitation | Announce that no positive royalty exists for the target math | No persistence |
-| Reset | Restore format, trim, profile, page, price, file-size, and target defaults | Clear errors and result | Focus the format control and announce defaults restored | No persistence |
-
-## Page composition
-
-| Claim or task | Medium | Position | Why this medium |
-| --- | --- | --- | --- |
-| Enter one KDP pricing scenario | Tool UI | First surface in the workbench | The author must set the scenario before any number has meaning. |
-| What remains per sale | Tool UI result lead | First result region | A single money answer is the primary decision. |
-| What KDP deducted | Tool UI cost receipt | Directly below the lead | Fixed cost, page cost, and delivery cost are exact repeated fields. |
-| Which prices change the answer | Tool UI comparison table | Below the cost receipt | Repeated price, rate, cost, royalty, and margin values belong in a table. |
-| What can be spent on ads and how many copies meet a target | Tool UI economics block | After the comparison | These are derived decisions from the selected royalty, not separate calculators. |
-| Why the result has limits | Sentence with source links | Result footer and later supporting content | Taxes, price matching, and sales demand need connected explanation, not another number. |
-| KDP rate changes and source date | Sentence with source links | Beside the result footer | The date and primary source make rate-sensitive output reviewable. |
-
-No marker art or clean chart is planned. The exact relationship is clearer in the result lead, receipt, and comparison table.
-
-## Technical plan
-
-### Architecture and file ownership
-
-- `app/(site)/(tools)/kdp-royalty-calculator/page.tsx` will remain a thin server route. It will load the central tool row with `getRequiredToolPage`, render the shared shell, and keep metadata, canonical, robots, sitemap, and JSON-LD out of the route.
-- `app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.tsx` will be the smallest client island. It owns form state, conditional fields, validation messages, submit and reset behavior, focus, and the result announcement.
-- `app/(site)/(tools)/kdp-royalty-calculator/kdp-royalty-calculator.module.css` will own the workbench layout and responsive states. It will use shared tokens and avoid global CSS changes, gradients, shadows, and nested dashboard cards.
-- `lib/kdp/specs.ts` will own the shared US KDP trim and page-limit catalog. `lib/kdp/royalty.ts` will own the pure input types, versioned cost tables, normalization, validation, formulas, comparison rows, and typed result states.
-- `tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs` will cover the pure engine and boundary fixtures. `tests/pages/kdp-royalty-calculator/page.test.mjs` and `tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.spec.ts` will cover route ownership, the rendered workbench, accessibility, responsive layout, and invalid-result behavior.
-- `tests/pages/kdp-royalty-calculator/page.json` will own this route's docs, tests, skills, and publication state. The future implementation will keep `content_docs/kdp-royalty-calculator/` as the planning and content ownership directory.
-- No page-specific script or external pricing dependency is needed at launch. A future data refresh must update the source date, formula version, cost-table tests, and supporting record together.
-
-### Accessibility, privacy, security, and performance
-
-- Use explicit labels, fieldsets for format-dependent choices, keyboard-reachable controls, visible focus, an error summary, and a polite live result region. Never rely on color alone for warnings or negative economics.
-- Keep the comparison table semantic and horizontally scrollable on narrow screens without hiding its headings. Use the same order in the DOM as the mobile reading order.
-- Perform all calculations in the browser. Do not send prices, page counts, file sizes, or target income to a server. Do not add analytics events for input values.
-- Parse numeric input as bounded values before passing it to the engine. The engine must return typed validation errors rather than throwing on user input.
-- Ship no new runtime dependency for the formula. The scenario calculation should complete synchronously and stay below 50 ms for one submission on a mid-range device.
-
-### Publication state
-
-Unpublished. This plan does not add a route, database row, production registry entry, sitemap entry, or publication state. The eventual route must remain a 404 outside a deliberate local preview until `public.stack127_pages` and `public.stack127_tool_pages` are reviewed and updated through the normal workflow.
-
-## Acceptance criteria
-
-| ID | Observable acceptance criterion | Evidence at build time |
-| --- | --- | --- |
-| R1 | The tool states Amazon.com and USD as fixed scope and never offers a marketplace selector. | Unit fixture and rendered UI test |
-| R2 | Format selection exposes only compatible print or eBook fields and resets incompatible values. | Browser test |
-| R3 | The canonical US paperback and hardcover trim catalogs resolve to the correct regular or large class and page limits. | Unit table fixtures |
-| R4 | An odd print page count is rounded up to an even effective count, shown to the user, and rejected when that count exceeds the selected KDP maximum. | Unit boundary fixtures |
-| R5 | Paperback printing costs match every current US branch, including short black ink, groundwood, standard color, premium color, regular trim, and large trim. | Unit fixture matrix |
-| R6 | Hardcover printing costs match the current US black ink and premium color branches, including 108/110-page and regular/large boundaries. | Unit fixture matrix |
-| R7 | Print royalty uses 50% at `$9.98` and 60% at `$9.99`, with the rate visible in the result and comparison rows. | Unit threshold fixtures and Browser assertion |
-| R8 | Print minimum price uses the correct piecewise band algorithm and never displays a price below the cost-covering floor. | Unit floor fixtures around both rate bands |
-| R9 | eBook delivery rounds the file size up to kilobytes, uses `$0.15/MB`, applies the `$0.01` minimum, and affects only the 70% equation. | Unit delivery fixtures |
-| R10 | eBook 70% applies only from `$2.99` through `$12.99`; an out-of-band selection falls back to 35% with a warning and no false 70% result. | Unit band fixtures and Browser assertion |
-| R11 | eBook 35% minimum price follows the `<3 MB`, `3 to <10 MB`, and `>=10 MB` file-size bands, with the applicable maximum enforced. | Unit price-floor fixtures |
-| R12 | Invalid fields, unsupported combinations, page limits, and price limits clear the result and focus the first recovery point. | Browser validation test |
-| R13 | A valid result leads with royalty per sale, then shows cost or delivery, minimum price, selected rate, and royalty margin. | Browser result-order test |
-| R14 | The comparison table contains unique valid rows for the format's minimum, selected price, and rate-boundary prices, with recalculated rate, cost, royalty, and margin. | Unit output fixture and Browser table test |
-| R15 | Positive royalty shows maximum break-even ad spend equal to royalty per sale and break-even ACoS equal to royalty divided by list price. | Unit economics fixtures |
-| R16 | A positive monthly target returns ceiling copies from rounded royalty cents; blank target omits the row, zero returns zero, and non-positive royalty returns unknown. | Unit economics fixtures and Browser test |
-| R17 | Money uses two decimals, rates use whole percentages, margins and ACoS use one decimal place, and the result shows the formula version and source date. | Static and Browser assertions |
-| R18 | Editing an input removes the old result, valid resubmission focuses the result heading, and reset restores defaults. | Accessibility Browser test |
-| R19 | The workbench stays one surface at desktop and stacks in the same logical order on narrow screens. The comparison table can scroll without page overflow. | Responsive Browser test at 320, 760, and desktop widths |
-| R20 | No scenario input leaves the browser, enters storage, or creates analytics payload data. | Static source review |
-| R21 | The route and registry remain unpublished until a separate publication decision. | Page manifest and SEO registry test |
-
-## Open questions and blockers
-
-- None. The next stage should turn this contract into the interface contract, then the exhaustive edge-case and test contract, without adding a second pricing model.
diff --git a/content_docs/kdp-royalty-calculator/interface-contract.md b/content_docs/kdp-royalty-calculator/interface-contract.md
deleted file mode 100644
index 7cebbbd5..00000000
--- a/content_docs/kdp-royalty-calculator/interface-contract.md
+++ /dev/null
@@ -1,273 +0,0 @@
-# Interface contract: KDP royalty calculator
-
-Status: ready
-Feasibility: feasible. The existing engine and shared controls support this interface contract within the approved product scope. This planning update does not certify runtime behavior, external services, or publication readiness.
-Tool: KDP royalty calculator
-Route: `/kdp-royalty-calculator`
-Mode: pipeline
-Review scope: Contract refresh within the unfinished new-tool pipeline, using its ready research and product inputs. This refresh reviews planning and source evidence only. Runtime state operation, rendered component consistency, and final tool acceptance remain separate required checks.
-Depends on: `brief.md`, `implementation-report.md`
-
-## User task
-
-- Primary user: A self-publishing author choosing a US Amazon.com list price for a paperback, hardcover, or Kindle eBook.
-- Question: What will this KDP scenario leave per sale at the selected list price?
-- Lead answer: The royalty per sale in USD, with the effective rate and selected format beside it.
-- Next decision: Keep or change the list price, then use the price floor, ad ceiling, and optional monthly target to judge the scenario.
-
-## Information decisions
-
-| Item | User question | Source | Disposition | Reason | Duplicate guard |
-| --- | --- | --- | --- | --- | --- |
-| Format | Which KDP product is being priced? | `format` input | input | It selects the calculation branch and the fields that can affect the answer. | Keep the choice in the form. Mention the selected format once in the lead detail, not in a second summary. |
-| Trim size | Which print size and cost class apply? | `trimSizeId` input and shared KDP preset catalog | input | It changes print cost, page limits, and regular or large trim classification. | Show it only in the active print form and the compact lead detail. eBook has no trim control. |
-| Print profile | Which interior and paper cost branch applies? | `printProfile` input | input | Black ink, groundwood, standard color, and premium color use different KDP costs and compatible bindings. | Use one combined profile control; do not split it into separate interior and paper selectors. |
-| Page count | How many printed pages are charged? | `pageCount` input | input | It changes printing cost and can make the selected trim/profile invalid. | Keep page count in the form and show the effective even count only in the cost receipt when it differs. |
-| List price | What sale price should the selected scenario test? | `listPriceUsd` input | input | It changes the rate band, royalty, margin, floor validation, and comparison rows. | The input owns the entered value; the lead detail may identify the rate at that price, but no separate price metric is needed. |
-| eBook royalty option | Which digital royalty option is being attempted? | `ebookRoyaltyOption` input | input | It changes the eBook equation and can produce a clear 35% fallback warning. | Show it only for eBooks and state the effective rate once in the lead and warning. |
-| eBook file size | What file-size floor and delivery deduction apply? | `ebookFileSizeMb` input | input | It changes the eBook delivery cost and the 35% minimum price band. | Show the entered size in the eBook form and the rounded delivery detail only in the receipt. |
-| Monthly target | How many copies would reach an optional income target? | `monthlyTargetUsd` input | input | It enables a useful follow-on decision without changing the selected-price royalty. | Keep the field visible but optional; its result appears only in the monthly-target region. |
-| Calculate royalties | When should the current scenario produce an answer? | Form submission | input | An explicit action separates editing from a committed result and gives validation a clear recovery point. | Use one primary action. Do not calculate on every keystroke. |
-| Reset | How can the author return to known defaults? | Local form action | input | It clears errors and results and restores format-specific defaults. | Keep one quiet secondary action beside the primary action; do not repeat it below the result. |
-| Amazon.com, USD, standard distribution | Which market and channel does the number describe? | Fixed formula scope | evidence | The calculator is deliberately US-first and excludes Expanded Distribution, so the scope must be visible without becoming a control. | Show one short scope line near the scenario and one matching source note; do not add marketplace or currency selectors. |
-| Selected-price royalty | What does one sale earn under this scenario? | `selectedRoyaltyCents`, effective rate, and list price | lead | This is the answer the author came to get. | Render one dominant lead value. Do not repeat it as a metric card or prose sentence. The comparison table may repeat it only as the selected row in a multi-price comparison. |
-| Printing or delivery deduction | What KDP charge produced the royalty? | Fixed cost, page cost, printing cost, file-size KB, or delivery cost | supporting | The author needs a compact receipt to audit the result and find the cost driver. | The receipt owns all cost components. Do not add a second cost equation or cost chart. |
-| Minimum price and royalty margin | What is the cost-covering floor and what share remains at the selected price? | `minimumPrice`, `royaltyMargin` | supporting | These values guide the pricing decision after the lead royalty. | Show each once in one supporting region. The comparison table repeats them only as row fields needed for cross-price comparison. |
-| Price comparison | How do the exact boundary prices change the economics? | Unique valid floor, selected, and rate-band rows | supporting | Repeated price, rate, cost or delivery, royalty, and margin fields need aligned columns. | The table is the only repeated-price view. Do not add cards or a second chart for the same rows. |
-| Break-even ad headroom | How much advertising spend can one sale absorb before royalty reaches zero? | `maxBreakEvenAdSpend`, `breakEvenAcos` | supporting | It answers the ad decision without pretending to forecast performance. | Show one labeled value and ACoS. When royalty is non-positive, show no positive headroom and no negative ACoS. |
-| Copies for monthly target | How many sales reach the entered monthly amount? | `monthlyTargetCents`, rounded royalty cents, `copiesForTarget` | supporting | It turns the selected royalty into simple unit math when the author asks for it. | Render only when a target is entered. A non-positive royalty owns the `unknown` explanation. |
-| Rate warning and validation status | Can the result be used, and what assumption needs attention? | Typed validation issues and eBook fallback warning | supporting | A 70% eBook selection outside its band remains calculable only after a visible 35% fallback explanation. | Place each message at the smallest useful scope. Do not mirror the same warning in a banner, field, and result. |
-| Formula version and source date | Which current KDP rules support this answer? | Local formula constants, version, and official KDP links | evidence | Rate-sensitive output needs a quiet audit trail and a refresh date. | Keep it in a compact source/details region. Do not turn sources into competing result cards. |
-| Exclusions and assumptions | What does this number not claim? | Product contract | evidence | Taxes, VAT, refunds, price matching, promotions, demand, and author expenses are outside the model. | Use one short limitation sentence or details block. Do not add a caveat panel above the lead. |
-
-## Input contract
-
-| Order | Input or action | Requirement | Affects lead answer | Default source | Placement | Component | Why visible | Narrow layout |
-| --- | --- | --- | --- | --- | --- | --- | --- | --- |
-| 1 | Format | required and defaulted | yes — selects the pricing branch and active fields | Product default `paperback` | visible | `ToolChoiceGroup` with Paperback, Hardcover, and Kindle eBook | The three product branches are the first decision and should be comparable without opening a menu. | Wrap the three choices, then keep the selected branch fields below. |
-| 2 | Trim size | conditionally required and defaulted for print | yes — changes print cost and page limits | Shared KDP catalog, default `6 x 9` | conditional | `ToolSelect` | The trim catalog is long and format-dependent, so a bounded select is clearer than free text. | Full width below Format when Paperback or Hardcover is active. |
-| 3 | Interior and paper | conditionally required and defaulted for print | yes — selects the KDP cost and page-limit branch | Product default `Black ink / white` | conditional | `ToolSelect` | It keeps compatible profile choices together and prevents unsupported binding combinations. | Full width below Trim size; unavailable profiles never appear. |
-| 4 | Printed pages | conditionally required and defaulted for print | yes — changes cost and eligibility | Product default `300` pages | conditional | `ToolNumberField` with whole-number step | Page count is a direct cost input and needs bounded numeric editing. | Full width; the validation message stays below the field. |
-| 5 | List price (USD) | required and defaulted | yes — changes rate, royalty, margin, floor validation, and comparison | `$14.99` for print, `$4.99` for eBook | visible | `ToolTextField` with decimal input mode | Keeping the exact edited string allows clear currency validation without floating-point UI behavior. | Full width with a stable USD label; long invalid values wrap in the field error, not the page. |
-| 6 | eBook royalty option | conditionally required and defaulted for eBook | yes — selects the requested digital rate and possible fallback | Product default `70%` | conditional | `ToolChoiceGroup` with 35% and 70% | Both options are important pricing choices, and hiding them in a select would make the rate model harder to inspect. | Two choices stay in one row when they fit and wrap as one group otherwise. |
-| 7 | eBook file size (MB) | conditionally required and defaulted for eBook | yes — changes delivery cost and the eBook floor band | Product default `1 MB` | conditional | `ToolNumberField` with `MB` suffix | File size is an active pricing assumption, even for the 35% floor calculation. | Full width below the royalty option. |
-| 8 | Monthly target (USD) | optional | no — changes only the optional copies result | Blank by design | visible | `ToolTextField` with decimal input mode | It enables target math without cluttering the required scenario or changing the lead royalty. | Full width below the main price fields; blank remains a normal state. |
-| 9 | Calculate royalties | primary action | not applicable — commits the current inputs | No default | visible | `ToolButton` of type submit inside `ToolActionRow` | One explicit action makes the answer predictable and gives invalid input a single recovery path. | Full width before Reset. Keep its label stable during a synchronous calculation. |
-| 10 | Reset | secondary action | no — restores defaults and clears the result | Restores format-specific defaults | visible | `ToolButton` with ghost or secondary treatment | It is the direct recovery action after experimenting with prices or switching format. | Full width below Calculate royalties. |
-
-Required-field behavior: Format and every active branch input keep visible and programmatic required states. Changing Format resets incompatible fields to their branch defaults, clears any result, and reveals the newly active fields. Editing any result-driving field clears the old result immediately; it does not silently recalculate. Submit focuses the first invalid field in source order and keeps the entered strings intact. The clean canonical route has no query state, and no input or result is written to browser storage.
-
-## Result contract
-
-| Order | Region | Unique user question | Data | Treatment | Evidence or omission guard |
-| --- | --- | --- | --- | --- | --- |
-| 1 | Royalty per sale | How much does one selected-price sale earn? | Selected royalty cents, selected list price, effective rate, and format | `ToolPrimaryResult` with one dominant USD value and one short detail line | This is the only lead. Do not place the same royalty in a second standalone metric. |
-| 2 | Cost receipt | What KDP deduction produces that amount? | Print fixed cost, page cost, total printing cost, effective page count, or eBook file-size KB and delivery cost | `ToolKeyValueList` with conditional rows and a short odd-page note when needed | The receipt owns all exact cost components. Do not render a cost allocation bar or duplicate equation. |
-| 3 | Price floor and margin | What cost-covering floor and retained percentage apply? | Minimum valid price and royalty margin at the selected price | `ToolKeyValueList` directly after the receipt | Show the floor and margin once outside the comparison table. Do not add a recommendation or a price verdict. |
-| 4 | Price comparison | How do the exact boundary prices change the economics? | Unique valid price rows with price, effective rate, cost or delivery, royalty, and margin | Semantic `ToolDataTable`; mark the selected row with text, not color alone | The table is the only repeated-price region. Omit duplicate rows and prices outside the active format's valid range. |
-| 5 | Ad headroom | What is the most this sale can absorb in advertising? | Maximum break-even ad spend and break-even ACoS | Compact labeled values using `ToolKeyValueList` or a page-owned equivalent | If royalty is zero or negative, show `No positive ad headroom` and omit ACoS instead of displaying a negative budget. |
-| 6 | Monthly target | How many copies reach the entered monthly amount? | Target amount and copies from rounded royalty cents | Conditional `ToolKeyValueList` or one labeled result row | Omit the region for a blank target. Show zero for a zero target and `Unknown` with its reason when no positive royalty exists. |
-| 7 | Calculation details | Which rule set and exclusions define the answer? | Formula version, source date, official KDP links, Amazon.com and USD scope, standard-distribution boundary, and key exclusions | `ToolDisclosure` with quiet metadata and one concise limitation sentence | This evidence stays after the economics. It must not repeat the lead or become a source-card grid. |
-
-The result order is lead, receipt, floor and margin, comparison, ad headroom, monthly target, then details. On a valid submission the result heading is focusable and receives focus after the DOM update. The result remains local to the browser and never promises author profit, demand, or KDP acceptance.
-
-## Visual semantics
-
-| Candidate | Relationship to communicate | Does geometry encode truth? | Decision |
-| --- | --- | --- | --- |
-| Price comparison table | The same fields across the floor, selected price, and exact rate boundaries | Yes — aligned columns compare repeated exact values without inventing a continuous scale | Use `ToolDataTable` with Price, Rate, KDP cost or delivery, Royalty, and Margin columns. |
-| Royalty margin progress bar | A percentage of list price retained after KDP deductions | No — a bar would suggest a target or quality score and adds no decision beyond the exact percentage | Omit and use a labeled percentage value. |
-| Price-band timeline | Where the 50% and 60% print bands or 35% and 70% eBook bands apply | No — the result uses discrete thresholds and a table communicates the exact boundary values better than equal-spaced geometry | Replace with the semantic comparison table and rate labels. |
-| Cost allocation bar | How list price splits among KDP cost, royalty, and ad headroom | No — ad headroom is a ceiling, not an allocated part of a sale, and the eBook and print equations do not share one visual partition | Omit and keep the receipt plus exact economics rows. |
-| Ad-spend gauge | How close a chosen ad budget is to break-even | No — the tool has no ad budget input and must not imply campaign performance | Omit; show maximum spend and ACoS as labeled values. |
-
-## State contract
-
-| State | Inputs and actions | Lead result | Supporting result | Error or recovery | Focus or announcement |
-| --- | --- | --- | --- | --- | --- |
-| Initial clean | Branch defaults are visible, monthly target is blank, Calculate royalties and Reset are available | Absent | No receipt, comparison, or economics regions | No helper panel and no unsolicited announcement | Normal focus order begins at Format. The clean URL stays unchanged. |
-| Editing after a result | The author changes Format or any active field | Removed immediately so old economics cannot sit beside new inputs | Removed with the old result | Keep the edited value and clear only resolved field errors | Keep focus in the edited control and announce that the result needs recalculation. |
-| Invalid submission | A required value is missing or malformed, an unavailable profile is selected, a page limit is exceeded, or price is outside its valid range | Absent | No partial economics result | Inline errors state the allowed range or recovery. Preserve all inputs and focus the first invalid field. | Announce one concise error summary; do not duplicate it inside the result area. |
-| Calculating | The form is submitted with valid-looking inputs | No stale lead is shown during the action | No stale support is shown | The engine is synchronous. If a render boundary yields, keep the button width and label it `Calculating royalties...`; do not add a spinner or fake progress. | Keep focus on the submit action until the result is ready. Do not announce a loading state that users cannot observe. |
-| Success | A valid print or eBook scenario is submitted | Show the selected royalty first with effective rate and format | Show receipt, floor and margin, comparison, ad headroom, optional target, and details in that order | None | Focus the result heading and announce the selected royalty once through a polite status. |
-| eBook fallback warning | 70% is selected outside the `$2.99` to `$12.99` band | Show the royalty calculated at the effective 35% rate | Keep the receipt and comparison; show one warning beside the result explaining the fallback | The author can change price or choose 35%; do not block the valid calculation | Announce the fallback once. Color supplements the words `35% rate` and `70% option not eligible`. |
-| No monthly target | A valid result is submitted with the optional target blank | Normal selected royalty | Omit only the monthly-target region | The blank is normal and needs no error | Do not announce an absent optional region. |
-| Non-positive royalty or unknown target | The selected economics produce zero or negative royalty, or a positive target is entered with no positive royalty | Show the exact non-positive royalty without calling it profit | Show no positive ad headroom and `Unknown` target copies with the reason when applicable | Change list price, format, or print inputs and submit again | Announce the limitation once; never render a negative ad budget or infinite copy count. |
-| Calculation or data failure | The versioned local constants are unavailable or the engine throws unexpectedly | Absent; remove any stale result | Keep all form inputs visible | `ToolStatus` says the calculation could not finish and leaves Calculate royalties available for retry | Focus the retry action or Calculate royalties and announce the failure as an alert. Do not clear valid input. |
-| Expanded calculation details | The author opens the optional Calculation details disclosure | Lead stays unchanged | Source date, formula version, links, and exclusions appear below the economics | Closing the disclosure restores the quiet evidence state | Use native disclosure semantics. Keep focus on the trigger and do not move the lead. |
-| Reset | The author activates Reset from any editable or result state | Absent | All errors, warnings, and support regions clear | Restore the Format, trim, profile, page, price, eBook, file-size, and blank-target defaults | Focus Format and announce that defaults were restored. |
-| Refresh or explicit query state | The author opens the clean route or refreshes it | Starts clean with no restored result | Starts clean with defaults | No URL, storage, cookie, or server restoration exists in v1 | Leave the canonical URL unchanged through hydration and make no announcement on load. |
-
-## Optional mode and state visibility
-
-- Control mode: disclosure
-- Reason: Format and every active pricing assumption stay visible. Print and eBook fields are conditional product branches; only calculation evidence collapses.
-- Shared engine and normalized input mapping: The same royalty adapter receives the normalized format-specific input and optional monthly target. No second calculation path or alternate rules are introduced.
-- Active assumptions: Keep required and defaulted result-driving values in the input flow described above. Conditional fields appear beside the choice that activates them, before submission.
-- Retention and recovery: Evidence expansion never changes input or result state. Retain edited values until the existing Reset, example, or branch action explicitly replaces them. Reveal and focus any invalid active conditional field; no collapsed region may hide a blocking error.
-- URL, reload, and history restoration: Preserve the URL contract and existing explicit restoration behavior below. A clean canonical load must remain unchanged through hydration; this mode decision adds no query, storage, or history writes.
-- Equivalent-input parity: There is one input model and one engine. A basic/advanced parity fixture is not applicable; disclosure state must not alter normalized inputs or computed output.
-
-## Component contract
-
-- Generic or native-looking fallback allowed: no
-- Inspection: shared implementations in `app/tool-ui`, the source for `/tool-ui-lab`, this route, and sibling patterns in `/kdp-book-setup-calculator`, `/kdp-royalty-calculator`, and `/kdp-pdf-preflight-checker`. This is source inspection, not a new rendered-state verification receipt.
-- Native form, input, radio, table, and file semantics may remain underneath the approved stack127 presentation. Missing behavior must receive a complete shared or justified route-specific contract; it must not become a bare native control, generic upload box, or unrelated dashboard component.
-- All rows use `--text-body`, `--color-text`, `--color-border`, `--radius`, `--space-*`, and `--focus-ring` as applicable. Only metadata uses `--text-small`. Keep one accent primary action, semantic status text, both themes, and no colored left edges.
-- Route-specific choices retain the behavioral reason in their row and use the existing route stylesheet. They do not introduce new controls or public behavior. Shared components own their internal appearance; route styles own placement and any stated reflow.
-
-| Need | Existing component inspected | Disposition | Chosen component | States, accessibility, responsive behavior, and tokens | Why it fits; rejected alternative |
-| --- | --- | --- | --- | --- | --- |
-| Three product branches | `ToolChoiceGroup` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolChoiceGroup` | Keep the active value visible, expose label and selection to assistive technology, preserve keyboard selection and focus, and associate validation with the control. Wrap choice rows and constrain popovers to the viewport. Use shared control tokens. | All important format choices remain visible and retain radio semantics. Rejected: A select would hide the first decision and make branch changes harder to scan. |
-| Long trim and profile catalogs | `ToolSelect` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolSelect` | Keep the active value visible, expose label and selection to assistive technology, preserve keyboard selection and focus, and associate validation with the control. Wrap choice rows and constrain popovers to the viewport. Use shared control tokens. | Bounded compatible options are easier to maintain and filter by binding than free text. Rejected: Free-text dimensions and a generic combo box would permit unsupported KDP combinations. |
-| Page count and eBook file size | `ToolNumberField` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolNumberField` | Keep persistent labels, required semantics where applicable, exact entered values, field-associated errors, and first-error focus. Preserve native editing and numeric keyboard behavior; labels and errors wrap on narrow widths. Use shared control tokens. | Whole-page and bounded decimal inputs benefit from numeric semantics, step controls, and visible units. Rejected: Plain text without numeric input mode would weaken keyboard and validation behavior. |
-| eBook royalty choice | `ToolChoiceGroup` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolChoiceGroup` | Keep the active value visible, expose label and selection to assistive technology, preserve keyboard selection and focus, and associate validation with the control. Wrap choice rows and constrain popovers to the viewport. Use shared control tokens. | 35% and 70% are both central, conditional choices and should not be hidden. Rejected: A disclosure would hide an active rate assumption. |
-| Currency inputs | `ToolTextField` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolTextField` with decimal input mode | Keep persistent labels, required semantics where applicable, exact entered values, field-associated errors, and first-error focus. Preserve native editing and numeric keyboard behavior; labels and errors wrap on narrow widths. Use shared control tokens. | It preserves the edited string until submission and avoids presenting floating-point behavior as exact money. Rejected: A range slider or currency-only masked input would make boundary errors and pasted values harder to recover. |
-| Submit and reset | `ToolActionRow`, `ToolButton` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolActionRow` with `ToolButton` | One submit is primary. Keyboard activation, disabled or busy state, and reset retain clear labels and visible focus. Keep input after failure and stack actions at narrow widths. Use shared button tokens. | One primary Calculate royalties action and one quiet Reset action preserve hierarchy and keyboard behavior. Rejected: Auto-submit, icon-only reset, or a second primary action would make the commit point unclear. |
-| Dominant royalty answer | `ToolPrimaryResult` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolPrimaryResult` | One lead precedes support; announce result changes and focus the documented result target after submit. Invalid inputs create field recovery, not a fabricated answer. Long values wrap. Use shared result and text tokens. | One money value deserves a clear result lead and accessible heading. Rejected: Equal metric cards would compete with or repeat the answer. |
-| Receipt and economics values | `ToolKeyValueList` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolKeyValueList` | Use semantic labels and exact values with explicit unknowns. Supporting facts follow the lead, retain source order, and stack at narrow widths. Use shared text and metadata tokens. | Exact labeled values and conditional rows are clearer than decorative panels. Rejected: `ToolMetricGroup` would make unlike cost, floor, margin, and target values appear equivalent. |
-| Repeated price rows | `ToolDataTable` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolDataTable` | Retain column and row headers, full exact values, explicit unknowns, and text states. The inner table viewport owns overflow and remains keyboard reachable; required reflow preserves labels. Use shared table tokens. | The rows share a fixed schema and need aligned exact comparisons. Rejected: Cards, a chart, or a timeline would either repeat facts or imply a false continuous model. |
-| Warning and failure feedback | `ToolStatus` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolStatus` plus field-level errors | Expose textual status and one concise live announcement. Keep recovery beside its input; no duplicate alert. Long messages wrap and status uses semantic text color only. | Status words and focus behavior remain accessible without relying on color. Rejected: A colored callout edge or a duplicate result error panel is rejected. |
-| Sources and assumptions | `ToolDisclosure` in `app/tool-ui/tool-controls.tsx` | reuse shared | `ToolDisclosure` after the economics | Named evidence follows the answer. Enter or Space toggles disclosures with expanded state and retained focus. Escaped output remains selectable; a bounded inner viewport owns any code overflow. Use shared evidence and focus tokens. | Optional evidence stays available without competing with the pricing answer. Rejected: Source cards, raw JSON, or a second visible formula panel add noise without another decision. |
-
-## Responsive contract
-
-| Width or condition | Layout and reading order | Longest realistic value | Overflow owner |
-| --- | --- | --- | --- |
-| Desktop, wider than 960px | Keep the scenario form in the left workbench column and the result in the right column when a result exists. Form order is Format, print or eBook fields, price, target, actions. Result order is lead, receipt, floor and margin, comparison, ad headroom, target, details. | `KDP US rules checked Sep 16, 2026`, `$1,000,000.00`, and the full `No positive ad headroom` status | No page overflow. The comparison region has a minimum readable width and may own an inner viewport only if the real main column cannot fit its five columns. |
-| 760px to 959px | Stack the full form before the result in DOM order. Keep active conditional fields together and let the result use the full main column. | `Premium color`, `650 MB`, and `Minimum cost-covering price` | The comparison table owns horizontal scrolling; form controls and source links wrap within their regions. |
-| 375px | One column. Format choices wrap, active fields stack, Calculate royalties and Reset become full-width actions, and the result follows the desktop reading order. | `$250.00`, `70% option not eligible at this price`, and `KDP cost or delivery` | Only the comparison table scrolls inside its labeled viewport. No page-level horizontal overflow. |
-| 320px | Preserve the same order and labels. Long errors and details wrap; the price table keeps its headings and can be scrolled without covering sibling content. | `Black ink / white`, `1,000,000 copies`, and `The selected price is below the calculated floor.` | The route-owned comparison viewport handles its minimum table width. Every other region uses `min-width: 0` and wraps. |
-| Both themes and reduced motion | Keep the same layout, status words, focus ring, and semantic labels in dark and light themes. Do not use color as the only signal and do not animate result geometry. | Warning, failure, and non-positive royalty text must remain readable without color. | Shared tokens and the route stylesheet own contrast and spacing; `app/globals.css` is not changed. |
-
-Stable dimensions: buttons retain a comfortable shared hit target and stable width through status changes. The result focus target does not shift when warnings appear. Table headers remain in the accessibility tree, and the page itself never owns horizontal overflow.
-
-## Interface wireframes
-
-### Desktop result
-
-```text
-KDP royalty calculator
-Amazon.com · USD · standard KDP distribution
-
-Scenario                                      Royalty per sale
-Format *             [Paperback          v]   $4.39
-Trim size *          [6 x 9              v]   60% rate at $14.99
-Interior and paper * [Black ink / white  v]   Paperback · 300 pages
-Printed pages *      [300                  ]
-List price (USD) *   [$14.99               ]   Cost receipt
-Monthly target       [optional             ]   Fixed cost              $1.00
-                                                Page cost               $3.60
-[Calculate royalties] [Reset]                  Printing cost           $4.60
-
-                                                Price floor and margin
-                                                Minimum price            $9.20
-                                                Royalty margin           29.3%
-
-                                                Price comparison
-                                                Price | Rate | KDP cost | Royalty | Margin
-                                                $9.20 | 50%  | $4.60    | $0.00   | 0.0%
-                                                $9.98 | 50%  | $4.60    | $0.39   | 3.9%
-                                                $9.99 | 60%  | $4.60    | $1.39   | 13.9%
-                                                $14.99| 60%  | $4.60    | $4.39   | 29.3%  selected
-
-                                                Ad headroom
-                                                Break-even spend       $4.39 per sale
-                                                Break-even ACoS        29.3%
-
-                                                Monthly target
-                                                $1,000 target           228 copies
-
-                                                > Calculation details
-                                                KDP US rules checked Sep 16, 2026
-```
-
-### Narrow mobile result
-
-```text
-KDP royalty calculator
-Amazon.com · USD · standard KDP distribution
-
-Scenario
-Format *             [Paperback          v]
-Trim size *          [6 x 9              v]
-Interior and paper * [Black ink / white  v]
-Printed pages *      [300                  ]
-List price (USD) *   [$14.99               ]
-Monthly target       [optional             ]
-[ Calculate royalties ]
-[ Reset ]
-
-Royalty per sale
-$4.39
-60% rate at $14.99 · Paperback
-
-Cost receipt
-Fixed cost                         $1.00
-Page cost                          $3.60
-Printing cost                      $4.60
-
-Price floor and margin
-Minimum price                      $9.20
-Royalty margin                     29.3%
-
-Price comparison  [scroll table]
-Price | Rate | KDP cost | Royalty | Margin
-...
-
-Ad headroom
-Break-even spend                   $4.39 per sale
-Break-even ACoS                   29.3%
-
-Monthly target
-$1,000 target                      228 copies
-
-> Calculation details
-KDP US rules checked Sep 16, 2026
-```
-
-### Initial, invalid, partial, failure, and expanded references
-
-```text
-Initial:   Scenario defaults visible. No result region. Format is first focus.
-Invalid:   List price  [$5.00]
-           Price must be at least $9.20 for this scenario.
-           Result removed. Focus returns to List price (USD).
-Calculating: [Calculating royalties...] keeps the action width; no stale result.
-Partial:   eBook at $14.99 with 70% selected.
-           Warning: 70% is not eligible here. Result uses 35%.
-No target:  Lead and economics remain. Monthly target region is omitted.
-Failure:   The calculation could not finish. [Calculate royalties] remains available.
-Expanded:  Calculation details opens below the economics without moving the lead.
-```
-
-## Removed or rejected
-
-- Remove marketplace, currency, tax, VAT, and Expanded Distribution selectors from v1; the fixed US Amazon.com scope is the data contract, not a set of unsupported branches.
-- Remove separate spine, printing-cost, break-even-ad, and sales-target calculators; their outputs belong to this one pricing decision and should not become five competing primary actions.
-- Remove ad budget, demand, BSR, Kindle Unlimited, sales forecast, and price-recommendation controls; the engine cannot support those claims.
-- Remove saved scenarios, browser storage, and automatic URL state; v1 has no shareable state and the clean route must stay clean through hydration.
-- Remove automatic calculation on every field edit; a stale answer is more dangerous than one explicit Calculate royalties action.
-- Remove progress bars, margin gauges, price timelines, and allocation charts; none has a truthful denominator or adds more clarity than exact values and the comparison table.
-- Remove duplicate royalty, price-floor, cost, and target metric cards; each fact has one result owner, with repetition permitted only inside the comparison table's repeated row schema.
-- Remove a positive or negative verdict such as `good price` or `profitable`; the result is royalty math, not author profit or demand advice.
-- Remove a success claim about KDP acceptance; the calculator exposes current source rules but does not model every order, marketplace adjustment, or review decision.
-
-## Acceptance criteria
-
-| ID | Category | Observable interface requirement | Evidence |
-| --- | --- | --- | --- |
-| UI-001 | lead | A valid submission places one `Royalty per sale` result first, with one dominant USD value and its effective rate; no other standalone result is visually equal. | Browser inspection at desktop and narrow widths. |
-| UI-002 | deduplication | The selected royalty, price floor, and cost receipt each have one standalone owner; repeated values appear only where the comparison table needs them for row comparison. | DOM/text review and browser result assertions. |
-| UI-003 | visual-truth | The price comparison uses aligned semantic columns, while no progress bar, gauge, allocation bar, or timeline implies a false target or continuous scale. | Interface inspection and table semantics test. |
-| UI-004 | responsive | At desktop, 760px, 375px, and 320px widths, the workbench preserves task order, controls stay usable, and only the comparison table can scroll horizontally. | Browser bounds and overflow measurements. |
-| UI-005 | url | Opening `/kdp-royalty-calculator` leaves the URL unchanged through server render and hydration; editing, submitting, and resetting do not serialize state. | Browser history and URL assertion. |
-| UI-006 | inputs | Format changes expose only compatible fields, reset incompatible values, and keep every active result-driving defaulted input visible. | Browser interaction matrix and form inspection. |
-| UI-007 | states | Invalid input, eBook 70% fallback, blank target, non-positive royalty, engine failure, retry, and reset each preserve recovery and announce the relevant change once. | Browser state matrix and accessibility inspection. |
-| UI-008 | evidence | The result exposes Amazon.com, USD, standard-distribution scope and a quiet formula version/source date without adding a marketplace selector or source-card grid. | Rendered result and static source review. |
-
-| UI-009 | component-consistency | Every visible nontrivial control and result uses the component and disposition above. Compare labels, focus, selected state, field errors, busy or disabled state where applicable, and narrow layout with the shared lab in both themes. No bare native or generic fallback may appear. | Source mapping plus required browser and keyboard review; this planning pass does not mark those runtime checks passed. |
-
-## Open questions and blockers
-
-- None. The builder can implement the form, result hierarchy, responsive behavior, and states without inventing another pricing model or changing the prepared formula contract.
diff --git a/content_docs/kdp-royalty-calculator/research.md b/content_docs/kdp-royalty-calculator/research.md
new file mode 100644
index 00000000..8d654298
--- /dev/null
+++ b/content_docs/kdp-royalty-calculator/research.md
@@ -0,0 +1,259 @@
+# Research: KDP Royalty Calculator
+
+Route: `/kdp-royalty-calculator` | Checked: 2026-10-11 | Competitors used: 7 (Amazon KDP plus six independent tools)
+
+## Who uses it
+
+The main group is an independent author who is pricing a book or checking what one sale might earn. They usually know the format and a candidate list price. For print, many also know page count, but trim size, interior, and paper can take a lookup. For eBooks, people may know the retail price but need to find the converted file size. Community questions show confusion between a royalty, profit, tax, and production costs.
+
+| Group | Rough share | What they already know | Their questions, in their words |
+| --- | --- | --- | --- |
+| Authors pricing a first or next book | Most (qualitative; no share data found) | Book format, likely price, sometimes page count | "How much do I earn on a $12.99 paperback?" "Why does a $9.98 paperback earn less than $9.99?" |
+| Authors comparing formats or offers | Some (qualitative) | Candidate prices for eBook and print; may know page count and file size | "Which is better, 35% or 70%?" "What is the delivery fee?" "What is the minimum list price?" |
+| Publishers planning several editions or ad spend | Few (qualitative) | Print specs, prices, target income, and perhaps ad budget | "How many sales do I need for a monthly target?" "What royalty can cover an ad sale?" |
+
+These are qualitative groups inferred from the pages and discussions reviewed. No source found a representative share of calculator users.
+
+- **First few seconds:** authors want a per-copy estimate at a price they can choose, and need to know whether the price is above the KDP minimum.
+- **Inputs people may know offhand:** format, candidate list price, and a rough monthly sales or income target. Page count is often known for a finished book. Trim, ink, paper, eligible eBook royalty plan, converted file size, and marketplace may require checking book files or KDP settings.
+- **What experienced users need:** separate estimates for each format, print cost or digital delivery deduction, minimum price, eligibility caveats, and price comparisons. Ad headroom or sales needed for a target are useful planning arithmetic, but do not equal net profit.
+
+## Published comparison data
+
+None found that can serve as a defensible benchmark for this tool's per-copy estimate. Royalties vary with format, list price, page count, print setup, file size, marketplace, and eligibility. Forum anecdotes mix royalties with editing, illustration, advertising, taxes, and other platforms, so they do not form a comparable range.
+
+Amazon's KDP Select Author Earnings page showed a $69.4 million pool for August 2026 when checked. That is an aggregate Kindle Unlimited fund, not a typical per-copy royalty or a same-definition comparison, so it should not be presented as an expected earnings range. [KDP Royalty Calculator](https://kdp.amazon.com/en_US/royalty-calculator)
+
+There is no source agreement that supports showing one "normal" royalty or profit range. Use a worked calculation as an arithmetic check, not a market benchmark.
+
+## Scope
+
+The defensible initial scope is a US Amazon.com estimate in USD for Kindle eBooks, paperbacks, and hardcovers. The remaining shared code in `lib/kdp/royalty.ts` and `lib/kdp/specs.ts` already models these three formats, US print costs, print thresholds, eBook delivery costs and price limits, and optional planning values for royalty margin, ad headroom, and copies for a monthly target. Its spec and royalty tables are dated `2026-09-16`. This is a source-code observation, not validation that every table is still current.
+
+Keep "royalty" separate from profit. The calculation excludes editing, cover design, ad spend, income tax, refunds, and some KDP account conditions. It cannot guarantee KDP acceptance or the final amount in the author's account.
+
+Searches tried:
+
+- `KDP royalty calculator Amazon print eBook royalty calculator`
+- `KDP royalty calculator Kindlepreneur Bookow Self Publishing Titans`
+- `site:reddit.com/r/selfpublish KDP royalty calculator how much earn print cost 70%`
+- `Amazon KDP royalty calculator questions paperback ebook royalty 60% $9.99`
+- `KDP royalty calculator Bookow royalty calculation`
+- `KDP royalty calculator calculator 2026 Kindle eBook paperback hardcover tool`
+- `People also ask KDP royalty calculator how is paperback royalty calculated 35 70 rate`
+
+Recurring domains and sources included Amazon KDP, KDPBook.io, SmartKDP, Kindlepreneur, Royalties HQ, BookDraft, KDP Workspace, Reddit's `r/selfpublish` and `r/KDP`, plus a search result for Self Publishing Titans. The seven tools tested below were the official calculator and six independent calculators. Google did not surface a usable People also ask panel in the search results I could inspect. The questions below come from competitor FAQs and community posts; they should not be presented as verified PAA wording.
+
+## Search intent
+
+| Query | What the searcher wants | Answer they need | What current results miss |
+| --- | --- | --- | --- |
+| KDP royalty calculator | A royalty estimate without navigating KDP help pages | Format-specific inputs, rate, deductions, and estimated amount | Results vary in supported formats, marketplace coverage, validation, and freshness. |
+| KDP paperback royalty calculator | A per-copy estimate for a print setup | Rate, printing cost, royalty, and minimum price for trim, paper, ink, and pages | Some tools show only a final royalty or do not enforce KDP's minimum price. |
+| How much do I earn on a $12.99 KDP paperback? | A concrete estimate for a common retail price | Print specifications and the correct 50% or 60% tier are needed too | Several pages answer with a worked example, but assumptions vary. |
+| Why does a $9.98 paperback earn less than $9.99? | Explanation of the US print royalty threshold | The 50%/60% step at $9.99, plus the print cost deduction | The $0.01 boundary is easy to miss when a tool only shows the current price. |
+| KDP eBook 35% or 70% royalty | Which plan applies and what the sale earns | Price, file size, marketplace, territory, and eligibility affect the answer | Some pages still give the old $9.99 upper limit for the US 70% option. |
+| What is the KDP eBook delivery fee? | Why the 70% estimate differs from 70% of retail price | US delivery cost is based on converted file size and is deducted before the 70% share | A simple 35% vs 70% comparison can hide the fee and file-size input. |
+| What is the lowest KDP paperback list price? | Whether a desired price can cover production | Print cost and applicable royalty tier determine the minimum | Tools that accept zero or below-floor prices may show arithmetic for an unpublishable setup. |
+
+Competitor FAQ and forum questions also include "Does this include Kindle eBook royalties?", "What does expanded distribution pay?", "Can a royalty be negative?", and "Are royalties calculated on price with VAT?" The reviewed high-ranking pages do not all answer these together or make their exclusions equally visible.
+
+## User problems
+
+| Problem people repeat | Evidence link | What it means for the tool |
+| --- | --- | --- |
+| Confusion about whether the plan pays 35% or 70%, and what costs are deducted | [First-time author asks how to choose KDP royalties](https://www.reddit.com/r/selfpublish/comments/1jdp9va/can_someone_help_me_on_how_to_choose_royalities/) | Show the actual rate and deduction in the estimate; explain that eligibility and marketplace matter. Treat Reddit advice as anecdotal and potentially stale. |
+| "Normal profit margin" questions mix KDP royalty with expenses and other channels | [Authors compare how much they make per book](https://www.reddit.com/r/selfpublish/comments/1d8ut3t/how_much_do_you_make_per_book/) | Label the output as an estimated KDP royalty. Do not call it profit or use individual replies as an earnings benchmark. |
+| Long books can have a minimum list price above the price an author hoped to charge | [Pricing a long paperback on KDP](https://www.reddit.com/r/selfpublish/comments/1g2u9d5/pricing_on_kdp/) | Make the print-cost floor and retail-price decision separate. A floor calculation cannot establish what readers will pay. |
+| New authors ask whether "royalty" means profit after tax and why they would pick 35% or 70% | [Questions about KDP royalties and pay](https://www.reddit.com/r/KDP/comments/1impxag/royalties_and_pay/) | Define royalty narrowly and state the exclusions near the answer. Avoid implying tax or net income is included. |
+
+These discussions are dated and self-selected. They are evidence of the questions people ask, not measures of how common each problem is.
+
+## Facts to get right
+
+| Fact | Primary source | How the tool should treat it |
+| --- | --- | --- |
+| US paperback royalty is 50% below $9.99 and 60% at or above $9.99; standard formula is rate times list price minus print cost. | [Paperback Royalty](https://kdp.amazon.com/en_US/help/topic/G201834330) | Apply the US threshold at the exact cent boundary and show the print cost deduction. |
+| US hardcover uses the same $9.99 threshold and 50%/60% tiers, with print cost deducted. | [Hardcover Royalty](https://kdp.amazon.com/en_US/help/topic/G77F3WPD3KQLJTFS) | Keep hardcover separate from paperback print-cost inputs. |
+| Amazon.com print list prices have a $250 maximum; the minimum depends on print cost and royalty tier. | [Paperback Royalty](https://kdp.amazon.com/en_US/help/topic/G201834330), [Hardcover Royalty](https://kdp.amazon.com/en_US/help/topic/G77F3WPD3KQLJTFS) | Enforce the price bounds. Explain that the minimum is a platform floor, not a recommended market price. |
+| Print cost is a fixed amount plus page count times per-page cost, with cost tables varying by marketplace, trim, ink, paper, binding, and page count. | [Paperback Printing Cost](https://kdp.amazon.com/en_US/help/topic/G201834340), [Hardcover Printing Cost](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H) | Use the matching dated table and validate supported page/spec combinations. Example: US 6x9, black-and-white, white-paper paperback at 200 pages costs $3.40 under the current table. |
+| Expanded Distribution pays 40% of the list price effective in its sales channel, minus printing costs, applicable taxes, and withholding. KDP says the Expanded Distribution minimum differs, but its public help pages do not give a separate 40% minimum-price formula. The paperback printing-cost page gives the standard minimum formula as printing cost divided by the applicable 50% or 60% rate. | [Expanded Distribution](https://kdp.amazon.com/en_US/help/topic/GQTT4W3T5AYK7L45), [Paperback Printing Cost](https://kdp.amazon.com/en_US/help/topic/G201834340), [Print Book Pricing Page](https://kdp.amazon.com/en_US/help/topic/G8BKPU9AGVZSF9QF), [Official KDP calculator](https://kdp.amazon.com/en_US/royalty-calculator) | Treat printing cost divided by 40% as a math-derived break-even point before taxes and withholding, not a KDP-published minimum rule. The ED help page tells authors to check the KDP Rights & Pricing grid for its estimated royalty. The exact ED minimum remains unconfirmed from public help pages. |
+| Groundwood is a current Amazon.com paperback paper option for black ink. The US page limits are 24 to 812 pages for 5x8, 5.06x7.81, 5.25x8, 5.5x8.5, 6x9, 6.14x9.21, 6.69x9.61, 7x10, 7.44x9.69, 7.5x9.25, and 8x10; 24 to 784 for 8.25x6 and 8.25x8.25; 24 to 764 for 8.27x11.69; 24 to 578 for 8.5x8.5 and 8.5x11. Manuscript page counts round up to an even number. | [Paperback Submission Guidelines](https://kdp.amazon.com/en_US/help/topic/G201857950), [Paperback Printing Cost](https://kdp.amazon.com/en_US/help/topic/G201834340) | Keep groundwood limited to black ink and validate the maximum for the selected trim. `lib/kdp/specs.ts` matches these US limits and exposes groundwood only for black-and-white paperback interiors. |
+| US hardcover printing costs are fixed plus per page. Black ink costs $6.80 fixed for regular trim or $7.49 for large trim at 75 to 108 pages. At 110 to 550 pages, they are $5.65 fixed plus $0.012 per page for regular trim or $0.017 for large trim. Premium color at 75 to 550 pages is $5.65 fixed plus $0.065 per page regular or $0.080 large. KDP's hardcover page range is 75 to 550 pages. | [Hardcover Printing Cost](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H), [Hardcover options and page limits](https://kdp.amazon.com/en_US/help/topic/GAVW3FZZAKA2KY3B) | `lib/kdp/royalty.ts` uses these US rates and cutoffs. `lib/kdp/specs.ts` supports five hardcover trim sizes and sets the 75 to 550 page range. The rates, large-trim treatment, and limits match the current KDP pages reviewed. |
+| The eBook 35% plan pays 35% of list price less applicable VAT; it has no delivery charge. The 70% plan deducts applicable VAT and delivery costs before applying 70%. | [Digital Book Pricing](https://kdp.amazon.com/en_US/help/topic/G200634500) | Show the selected/effective rate and deduction. Do not describe 70% as 70% of the full retail price. |
+| For US sales, the eBook delivery rate is $0.15/MB. KDP bases it on converted file size rounded up to the nearest KB, with a $0.01 minimum. | [Digital Book Pricing](https://kdp.amazon.com/en_US/help/topic/G200634500) | Use converted file size as an estimate input and explain that the uploaded source file size may differ. The shared model rounds MB upward to KB. |
+| Effective July 7, 2026, the US 70% eBook price band is $2.99 to $12.99. The 35% minimum is $0.99 below 3 MB, $1.99 from 3 MB to under 10 MB, and $2.99 at 10 MB or higher. eBook maximum list price is $200. | [eBook List Price Requirements](https://kdp.amazon.com/en_US/help/topic/G200634560) | Keep the US 70% ceiling current at $12.99; use the size-based minimum for the 35% plan and the maximum. Add a checked date to the rule source. |
+| 70% eligibility depends on more than price, including territory and content/account conditions. KDP notes a requirement that the eBook price be at least 20% below the print edition in certain cases; price matching and promotions can also affect realized royalties. | [Digital Book Pricing](https://kdp.amazon.com/en_US/help/topic/G200634500), [eBook List Price Requirements](https://kdp.amazon.com/en_US/help/topic/G200634560) | Treat a calculator result as conditional. It cannot establish account or book eligibility, and actual reported earnings can differ. |
+| The official KDP print calculator estimates paperback and hardcover printing cost, minimum list price, and royalty; it does not estimate Expanded Distribution. | [Official KDP calculator](https://kdp.amazon.com/en_US/royalty-calculator) | Link to the official source for final verification and disclose the channel limitation. |
+| The existing shared tables use rule version `2026-09-16`; code includes US formulas, eBook threshold points, print minimums, and print page limits. | `lib/kdp/royalty.ts`, `lib/kdp/specs.ts` | Treat this as current repository behavior, not an official rule citation. Recheck the official sources before reusing or changing the tables. |
+
+KDP explicitly says paperback manuscript page counts round up to an even number. `lib/kdp/royalty.ts` and the shared setup calculations apply this rule before checking print page limits and cost.
+
+Code comparison for these checks: no groundwood page-limit or hardcover cost-table discrepancy was found. The shared royalty engine calculates standard Amazon print royalties; it does not implement Expanded Distribution. KDP does not confirm `printing cost / 40%` as the ED minimum-price formula in the public help pages reviewed. To confirm the actual ED minimum for a title, use its KDP Rights & Pricing grid.
+
+## Competitor reviews
+
+### 1. Amazon KDP Printing Costs and Royalty Calculator
+
+URL: [kdp.amazon.com/en_US/royalty-calculator](https://kdp.amazon.com/en_US/royalty-calculator)
+
+- **Observed** It asks for book type, interior, trim, marketplace, page count, and list price. Its print result table shows marketplace, list price, royalty rate, minimum list price, printing cost, and estimated royalty.
+- **Observed** Correct case: 200-page 6x9 black-and-white paperback at $12.99 returned $4.39 with $3.40 printing cost. Edge case: $9.98 returned the 50% tier and $1.59. Wrong input: $0 was rejected with "List price can't be 0 or empty."
+- **Documented** The page supports paperback and hardcover, many marketplaces, and says figures are estimates. It explicitly excludes Expanded Distribution estimates.
+- **Inferred** This is the reference source users can trust for print inputs, but its public calculator does not cover eBooks, so users need another page for the full KDP set.
+- **Unknown** I did not verify every marketplace and binding combination.
+
+```text
+200 pages, 6x9, black-and-white paperback, $12.99 -> $4.39 royalty
+$9.98 -> $1.59 at 50%; $0 -> price validation error
+```
+
+### 2. KDPBook.io
+
+URL: [kdpbook.io/kdp/royalty-calculator](https://kdpbook.io/kdp/royalty-calculator)
+
+- **Observed** It has paperback, hardcover, and eBook modes; marketplace options; print specifications; and an Expanded Distribution option for paperback. Print results show a cost breakdown, minimum price, royalty, and nearby price comparisons.
+- **Observed** Correct case: 200-page 6x9 black-and-white paperback at $12.99 returned $4.39 and $3.40 print cost. Edge case: $9.98 returned $1.59 at 50%; 201 pages was treated as 202. Wrong input: $0 produced a visible "Enter a list price above 0" validation message.
+- **Documented** The site displays source/update dates in September and October 2026 and its eBook section shows a $12.99 upper bound for the US 70% plan.
+- **Inferred** Its multiple-format, source-dated presentation is a strong competitor; it gives users more public market coverage than the current US-focused shared engine.
+- **Unknown** I did not validate every marketplace's rates or every Expanded Distribution case against KDP.
+
+```text
+200 pages, 6x9 paperback, $12.99 -> $4.39
+$9.98 -> $1.59; 201 pages -> 202; $0 -> validation error
+```
+
+### 3. SmartKDP
+
+URL: [smartkdp.com/tools/kdp-royalty-calculator](https://smartkdp.com/tools/kdp-royalty-calculator)
+
+- **Observed** It supports paperback, hardcover, and Kindle eBook, with multiple Amazon marketplaces, print costs, minimums, margin, and an Expanded Distribution option. It also shows a worked example and a market comparison table.
+- **Observed** Correct case: a 200-page 6x9 black-and-white paperback at $12.99 returned $4.39. Edge case: $9.98 returned $1.59. Wrong input: $0 returned a negative $3.40 amount and a "Below break-even" status instead of rejecting a price below KDP's $6.80 floor.
+- **Documented** Its page says tables were checked July 22, 2026.
+- **Inferred** Accepting zero can confuse equation output with an allowed KDP list price. The tool's coverage and dated table are useful strengths, but users still need to distinguish a modeled number from a publishable price.
+- **Unknown** I did not independently verify all listed marketplace tables or every eBook condition.
+
+```text
+200 pages, 6x9 paperback, $12.99 -> $4.39
+$9.98 -> $1.59; $0 -> -$3.40 and "Below break-even"
+```
+
+### 4. Kindlepreneur KDP Royalty Calculator
+
+URL: [kindlepreneur.com/kdp-royalty-calculator](https://kindlepreneur.com/kdp-royalty-calculator/)
+
+- **Observed** It offers eBook, paperback, and hardback inputs, including royalty plan, marketplace, price, eBook file size, or print details. The displayed result emphasizes effective royalty rate and a graph; an exact dollar result was not available as readable text in the test.
+- **Observed** Correct eBook case: $4.99, 5 MB, and 70% showed an effective rate of 59%, consistent with subtracting a $0.75 delivery charge before applying 70%. Edge paperback case: $9.98 showed an effective rate of 16%, consistent with $1.59 on $9.98. Wrong input: $0 showed "--" rather than a result.
+- **Documented** The page's guidance says the US 70% price band ends at $9.99. That ceiling became stale after KDP's July 7, 2026 increase to $12.99.
+- **Inferred** It is useful for comparing formats, but a rate-focused result is less direct for people asking "how many dollars do I earn?"
+- **Unknown** I could not confirm exact displayed dollar amounts from the accessible result text or test every print setting.
+
+```text
+$4.99 eBook, 5 MB, 70% -> 59% effective rate
+$9.98 paperback -> 16% effective rate; $0 -> "--"
+```
+
+### 5. Royalties HQ
+
+URL: [royaltieshq.com/kdp-royalty-calculator](https://royaltieshq.com/kdp-royalty-calculator/)
+
+- **Observed** It has eBook, paperback, and hardcover tabs and estimates per-sale plus total royalties for a chosen copy count. The print model says it assumes regular trim.
+- **Observed** Correct eBook case: $4.99, 2 MB, 70%, and 100 sales returned $0.30 delivery, $3.28 per sale, and $328.30 total. Edge case: $12.99 was forced to 35% and returned $4.55 per sale. Wrong input: $0 returned $0 with no visible validation.
+- **Documented** Its page says the 70% maximum is $9.99 and carries an April 13, 2026 checked date. Both are out of date for the US after the official July 7 increase.
+- **Inferred** The copy-count estimate is useful for planning, but an old cap can understate eligible eBook earnings for a $10 to $12.99 price.
+- **Unknown** I did not test all print settings or verify its formulas for other marketplaces.
+
+```text
+$4.99 eBook, 2 MB, 70%, 100 copies -> $3.28 each; $328.30 total
+$12.99 -> forced to 35%; $0 -> $0 with no visible validation
+```
+
+### 6. BookDraft KDP Royalty Calculator
+
+URL: [bookdraft.co/tools/kdp-royalty-calculator](https://bookdraft.co/tools/kdp-royalty-calculator)
+
+- **Observed** It covers Amazon.com paperback and eBook estimates, explains the formula, and shows a minimum print price and examples. It also has an Expanded Distribution selection for paperback.
+- **Observed** Correct case: 200-page 6x9 black-and-white paperback at $12.99 returned $4.39 and a $6.80 minimum. Edge case: $9.98 returned $1.59. Wrong input: at $0 the result section disappeared, with no visible input error in the test.
+- **Documented** The page was updated October 6, 2026 and uses the current $12.99 eBook band. Its stated scope is Amazon.com/USD; it does not include hardcover.
+- **Inferred** Its worked examples and formula explanation help readers audit the estimate. Users pricing a hardcover or another marketplace need a different calculator.
+- **Unknown** I did not verify the eBook estimate against an account-specific KDP case.
+
+```text
+200 pages, 6x9 paperback, $12.99 -> $4.39; minimum $6.80
+$9.98 -> $1.59; $0 -> result disappears
+```
+
+### 7. KDP Workspace Guide
+
+URL: [kdpworkspace.com/guides/royalty-calculator](https://kdpworkspace.com/guides/royalty-calculator/)
+
+- **Observed** This is a US paperback calculator with page count, paper, trim, and list price. It returns a royalty estimate and explains the formula. The guide points readers to a separate full calculator for other marketplaces.
+- **Observed** Correct case: 200-page black-and-white paperback at $12.99 returned $4.39. Edge case: $9.98 returned $1.59 at 50%. Wrong input: $0 returned negative $3.40 without enforcing the $6.80 minimum.
+- **Documented** Its page is limited to US paperback estimates; it does not calculate hardcover or eBook royalties.
+- **Inferred** The small scope keeps the estimate simple, but users with multiple formats must leave the page. A below-floor result needs clearer distinction from an allowed KDP price.
+- **Unknown** I did not test the guide's separate full calculator.
+
+```text
+200 pages, 6x9 paperback, $12.99 -> $4.39
+$9.98 -> $1.59; $0 -> -$3.40
+```
+
+## Comparison
+
+| Feature or answer | Amazon KDP | KDPBook.io | SmartKDP | Kindlepreneur | Royalties HQ | BookDraft | KDP Workspace | What stack127 should do |
+| --- | --- | --- | --- | --- | --- | --- | --- | --- |
+| eBook, paperback, hardcover | Print only | Yes | Yes | Yes | Yes | eBook and paperback | Paperback only | Match the three formats covered by shared KDP code. |
+| Marketplace coverage | Many print marketplaces | Many | Many | Several | Several | US only | US only | State the supported US scope clearly unless rules are researched and modeled for other marketplaces. |
+| US eBook $12.99 70% ceiling | Not an eBook tool | Current | Current in page | Stale at $9.99 | Stale at $9.99 | Current | Not an eBook tool | Use the July 7, 2026 official limit and date the source data. |
+| Cost detail | Print cost and minimum | Cost breakdown | Cost and minimum | Effective rate and graph | Delivery plus royalty | Formula and minimum | Formula | Make the amount and its deduction auditable. |
+| Below-floor or zero price | Rejects zero | Rejects zero | Calculates negative | Shows no result | Returns zero | Hides result | Shows negative | Keep invalid prices distinct from valid royalties. |
+| Expanded Distribution | Excluded | Paperback option | Option | Not confirmed | Not confirmed | Paperback option | Not included | Do not suggest the US standard-channel answer covers it. |
+| Price/target planning | No eBook or target model | Price comparisons | Market comparison | Graph | Copy-count total | Worked examples | Single estimate | Explain planning arithmetic and keep it separate from profit. |
+
+## Where competitors disagree
+
+The biggest live disagreement is the US eBook 70% ceiling. KDP's official price rules raised it from $9.99 to $12.99 effective July 7, 2026. Royalties HQ's page states the old $9.99 ceiling and was checked April 13; Kindlepreneur also states $9.99. KDPBook.io, SmartKDP, and BookDraft show the current upper bound. The official KDP date and current help page control. [KDP eBook List Price Requirements](https://kdp.amazon.com/en_US/help/topic/G200634560)
+
+Invalid-price behavior also differs. SmartKDP and KDP Workspace show a negative amount at zero, while the official KDP calculator and KDPBook.io reject zero. A negative formula result does not mean KDP accepts that list price or charges the author. For a print book, the tool should enforce the minimum list price derived from print cost and the applicable royalty rate.
+
+The word "royalty" is also used loosely in forum replies and competitor copy. KDP's royalty formula is a platform payout estimate before the author's publishing expenses and tax position. A per-sale royalty should not be relabeled as profit or take-home income.
+
+## How stack127 can win
+
+- Cover the three KDP formats the shared engine already supports in one US-focused estimate, and make it clear that the calculation is for Amazon.com in USD.
+- Make the result auditable: state the selected rate, print cost or delivery deduction, and estimated royalty. Include worked values around the exact $9.98/$9.99 print boundary and the current $12.99 eBook upper limit.
+- Keep the KDP list-price floor separate from a suggested retail price. Reject invalid or below-floor print prices instead of showing negative earnings as though the setup could be published.
+- Explain the difference between a royalty and profit. Be explicit about what is not included: production and marketing expenses, taxes, Expanded Distribution, and account-specific eligibility.
+- Keep a dated source ledger for the shared rules. The search results show that some competitor pages retain old price bands after policy changes; users benefit from seeing when the rules were checked.
+- Answer the questions that lead to support confusion: why print royalty changes by one cent at $9.99, why eBook 70% is reduced by delivery cost, why an eBook may be limited to 35%, and why the minimum print price may be higher than the author's intended price.
+- Avoid claiming typical earnings. No comparable public dataset supports such a range.
+
+The market is crowded: official KDP is authoritative for print, and several third-party tools already cover multiple formats, examples, or price comparisons. A credible edge is current US rules, clear assumptions, and reliable handling of price boundaries rather than adding a broader marketplace claim without verifying those rules.
+
+## Blockers
+
+None. Public KDP help pages are sufficient for the rules in the current US scope. Keep source dates current as Amazon changes rules; no paid API or outside dataset is needed.
+
+## Sources
+
+- [Paperback Royalty](https://kdp.amazon.com/en_US/help/topic/G201834330), checked 2026-10-11.
+- [Paperback Printing Cost](https://kdp.amazon.com/en_US/help/topic/G201834340), checked 2026-10-11.
+- [Expanded Distribution](https://kdp.amazon.com/en_US/help/topic/GQTT4W3T5AYK7L45), checked 2026-10-11.
+- [Paperback Submission Guidelines](https://kdp.amazon.com/en_US/help/topic/G201857950), checked 2026-10-11.
+- [Hardcover Royalty](https://kdp.amazon.com/en_US/help/topic/G77F3WPD3KQLJTFS), checked 2026-10-11.
+- [Hardcover Printing Cost](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H), checked 2026-10-11.
+- [Hardcover options and page limits](https://kdp.amazon.com/en_US/help/topic/GAVW3FZZAKA2KY3B), checked 2026-10-11.
+- [Print Book Pricing Page](https://kdp.amazon.com/en_US/help/topic/G8BKPU9AGVZSF9QF), checked 2026-10-11.
+- [Digital Book Pricing](https://kdp.amazon.com/en_US/help/topic/G200634500), checked 2026-10-11.
+- [eBook List Price Requirements](https://kdp.amazon.com/en_US/help/topic/G200634560), checked 2026-10-11.
+- [Official KDP Printing Costs and Royalty Calculator](https://kdp.amazon.com/en_US/royalty-calculator), interacted with 2026-10-11.
+- [KDPBook.io calculator](https://kdpbook.io/kdp/royalty-calculator), interacted with 2026-10-11.
+- [SmartKDP calculator](https://smartkdp.com/tools/kdp-royalty-calculator), interacted with 2026-10-11.
+- [Kindlepreneur calculator](https://kindlepreneur.com/kdp-royalty-calculator/), interacted with 2026-10-11.
+- [Royalties HQ calculator](https://royaltieshq.com/kdp-royalty-calculator/), interacted with 2026-10-11.
+- [BookDraft calculator](https://bookdraft.co/tools/kdp-royalty-calculator), interacted with 2026-10-11.
+- [KDP Workspace Guide calculator](https://kdpworkspace.com/guides/royalty-calculator/), interacted with 2026-10-11.
+- [Reddit: choosing KDP royalties](https://www.reddit.com/r/selfpublish/comments/1jdp9va/can_someone_help_me_on_how_to_choose_royalities/), checked 2026-10-11.
+- [Reddit: earnings per book](https://www.reddit.com/r/selfpublish/comments/1d8ut3t/how_much_do_you_make_per_book/), checked 2026-10-11.
+- [Reddit: pricing on KDP](https://www.reddit.com/r/selfpublish/comments/1g2u9d5/pricing_on_kdp/), checked 2026-10-11.
+- [Reddit: royalties and payment](https://www.reddit.com/r/KDP/comments/1impxag/royalties_and_pay/), checked 2026-10-11.
diff --git a/content_docs/kdp-royalty-calculator/tool-spec.md b/content_docs/kdp-royalty-calculator/tool-spec.md
new file mode 100644
index 00000000..7d18784f
--- /dev/null
+++ b/content_docs/kdp-royalty-calculator/tool-spec.md
@@ -0,0 +1,406 @@
+# KDP royalty calculator
+
+Route: `/kdp-royalty-calculator`
+
+Research: [research.md](research.md)
+
+## People and questions
+
+- Most users are: independent authors pricing a paperback, hardcover, or Kindle eBook for Amazon.com. They come with: the format, a price they have in mind, and for print, the page count and whether the inside is black and white or color.
+- Their top questions:
+  1. "How much do I earn on a $12.99 paperback?" (or a $4.99 eBook)
+  2. "Why does a $9.98 paperback earn less than $9.99?" and "Should I take 35% or 70%?"
+  3. "What's the lowest price KDP will let me set?"
+- Basic answers them with: format, list price, and for print, page count and interior. Four fields for print and two for an eBook. Everything else opens on a default the hint names.
+- Advanced holds:
+  - **Trim size**, for print authors who don't use 6 × 9 in. Large trims (wider than 6.12 in or taller than 9 in) cost more per page, and page limits differ. Default 6 × 9 in, the trim the research examples and KDP's own calculator test use.
+  - **Paper**, for print authors who chose cream or groundwood. Cream changes the page limit; groundwood changes the cost. Default white.
+  - **Sales channel** (paperback only): Amazon.com or Expanded Distribution, for authors who also sell to bookstores and libraries. Three of the six independent competitors offer it, and "What does Expanded Distribution pay?" is a repeated question. KDP publishes the 40% rate but not this channel's minimum price, so the tool shows the break-even price, where 40% just covers printing, and never calls it KDP's minimum. Default Amazon.com.
+  - **Converted file size** (eBook), for eBook authors who know their size from KDP's pricing page. It sets the 70% delivery cost and the 35% minimum price. Empty uses 2 MB, and the result names that size wherever it's used, so the default is never hidden.
+  - **Royalty plan** (eBook): 70% or 35%, for authors who must use 35%, such as for public-domain books or stores outside the 70% list. Default 70%, which KDP applies only from $2.99 to $12.99; outside that band the result pays 35% and says so.
+  - **Monthly royalty goal**, for publishers planning income or several editions. It turns the per-copy royalty into copies a month. The old tool had it. Empty means not used.
+- Left out:
+  - **Other Amazon stores and currencies.** Each store has its own print cost table, VAT, and price rules, and the research only verified Amazon.com. A wrong UK or EU number is worse than none.
+  - **Profit after editing, covers, ads, and tax.** The research's top confusion is royalty versus profit. This page answers one number, what KDP pays per copy, and labels it that way. The KDP price and profit calculator handles per-sale and one-time costs.
+  - **Kindle Unlimited page reads.** Paid from a monthly pool per page read, not per sale, with a different set of inputs. The Kindle Unlimited KENP earnings calculator covers it.
+  - **Price from a target royalty.** The reverse question, "what price earns me $3?", is the KDP minimum list price calculator's job. The chart here still shows the royalty at every nearby price.
+  - **Ad spend.** The break-even ACoS is a hint on "Share of list price", since it is the same number. Bids and targets stay with the KDP book ads bid check.
+- Opens with: a 200-page, 6 × 9 in, black-and-white paperback on white paper at $12.99. It earns $4.39, the same as the official KDP calculator and five competitors in the research. Typical for a novel, and a verified answer for the first thing people see.
+- Published comparison: none. The research found no source measuring a typical royalty, so the result shows no range.
+- Domain limits: the print minimum list price (from printing cost and rate), the Expanded Distribution break-even price (a math floor, since KDP doesn't publish that channel's minimum), the $250 print maximum, the eBook minimum by file size ($0.99, $1.99, or $2.99), the $200 eBook maximum, the 70% band of $2.99 to $12.99, KDP page limits per binding, trim, interior, and paper, and a 70% delivery cost larger than the 70% share. See States for how each answers.
+
+## Why people will choose this tool
+
+The searcher is deciding on a price. They want the dollars they'll earn per copy at that price, and whether a small change, such as a cent or a dollar, would earn more.
+
+Where the top results fail them:
+
+- KDP's own calculator has no eBooks. KDP Workspace has paperback only. BookDraft has no hardcover.
+- Kindlepreneur and Royalties HQ still use the old $9.99 top of the 70% band, so they understate eBooks priced $10 to $12.99.
+- SmartKDP and KDP Workspace show a negative royalty at $0. BookDraft's result disappears. Neither tells you the lowest price KDP allows.
+- Most show one number at one price, so the $9.98 to $9.99 step and the $12.99 to $13.00 drop stay invisible.
+- Kindlepreneur leads with a rate, not dollars.
+
+What this tool does better:
+
+1. All three formats in one tool, on the current Amazon.com rules, including the July 7, 2026 $12.99 band.
+2. Dollars first, with a bar that shows where the rest of the list price goes: printing or delivery, and Amazon's share. "70% isn't 70% of the price" becomes obvious.
+3. A chart of royalty at every nearby price, with the person's price marked. The $9.99 step and the $12.99 drop show up without reading anything.
+4. A price below KDP's minimum answers with the minimum and what it earns, never a negative number or a blank.
+5. For eBooks, both plans side by side, so "35% or 70%?" has a direct answer for the person's own price and file size.
+6. The next useful number when it matters: what $9.99 would earn when the price is just below it, or what $12.99 on 70% would earn when an eBook is priced above the band.
+
+## Product
+
+### Promise and scope
+
+- Primary user: an independent author pricing one book format on Amazon.com.
+- Main job: show the KDP royalty per copy sold at a chosen list price, and what changes nearby.
+- Delivered answer: royalty per copy in USD, how the list price splits, the applied rate, the KDP minimum list price, the royalty as a share of the price, one next-step comparison, copies a month for an optional goal, and royalty across nearby prices.
+- Launch scope: Amazon.com, USD, Kindle eBook, paperback, and hardcover. Standard channel for all three, plus Expanded Distribution for paperbacks.
+- Exclusions: other stores and currencies, profit and costs, tax, Kindle Unlimited, price matching and promotions, refunds, and account or book eligibility. The tool doesn't check whether a trim and paper can use Expanded Distribution, or whether a book qualifies for 70%. It doesn't know KDP's Expanded Distribution minimum or deduct that channel's taxes and withholding. The page content says so and points to the book's Rights & Pricing page in KDP.
+
+### Technical contract
+
+All money is whole cents inside the engine. The engine is a pure synchronous function. It runs in the browser with no network calls and stores nothing.
+
+**Inputs and parsing**
+
+| Input | Parsing and bounds | Empty |
+| --- | --- | --- |
+| Format | `paperback`, `hardcover`, or `ebook` | Error |
+| List price | Trimmed text. Optional leading `$`. Digits with up to 2 decimals: `12`, `12.5`, `$12.99`. Must be above $0. No upper bound at parse time; see limits. | Error |
+| Page count (print) | Whole number, 1 or more | Error |
+| Interior (print) | `black-white`, `standard-color`, `premium-color`. Hardcover allows `black-white` and `premium-color`. | Error |
+| Trim (print) | A trim ID from `getKdpTrimOptions(binding)` | `6x9` |
+| Paper (print) | From `getKdpPaperOptions(binding, interior)` | `white` |
+| Channel (paperback) | `amazon` or `expanded`. Ignored for hardcover and eBook. | `amazon` |
+| File size (eBook) | Number in MB, above 0 and at most 650 | 2 MB |
+| Plan (eBook) | `70` or `35` | `70` |
+| Monthly goal | Money, parsed like list price, above $0 and at most $10,000,000 | Not used |
+
+**Formulas.** Use the existing helpers in `lib/kdp/royalty.ts` so every KDP tool agrees.
+
+- Printed pages: an odd page count rounds up to the next even number, as KDP's paperback submission guidelines say.
+- Printing cost: `getKdpPrintCost` with the printed pages. Keep the unrounded cost to $0.0001 with `getKdpPrintingCostHundredthCents`, and use it in every print calculation. `getKdpPrintingCostCents` rounds it to whole cents only for display and the split.
+- Amazon.com print: rate 50% below $9.99 and 60% at $9.99 or more. Royalty = `round(price × rate − unrounded printing)`, rounded once to the nearest cent. Minimum = unrounded printing ÷ rate, rounded to the nearest cent, not always up, with `getKdpPrintFloorCents`. Maximum $250.
+- Expanded Distribution (paperback): rate 40%. Royalty = `round(price × 40% − unrounded printing)`, rounded once. Break-even price = unrounded printing ÷ 40%, always rounded up to the cent, the lowest price where the royalty isn't negative. This is arithmetic, not a KDP rule: KDP says this channel has its own minimum but doesn't publish how it's worked out, and its real minimum may be higher. The break-even price is always at or above the Amazon.com minimum, so it's the only lower bound for this channel. Maximum $250.
+- eBook delivery: `getKdpEbookDeliveryCents(fileSizeMB)`, which is $0.15 per MB on the size rounded up to the KB, $0.01 at least.
+- eBook 70%: applies only when the plan is 70 and the price is $2.99 to $12.99. Royalty = `round((price − delivery) × 70%)`. If that is 0 or less, the royalty is $0.00 and `deliveryExceedsShare` is true.
+- eBook 35%: royalty = `round(price × 35%)`, no delivery cost. Used when the plan is 35, or when the plan is 70 and the price is outside the band.
+- eBook minimum: `getKdpEbookFloorCents(fileSizeMB)`. Maximum $200.
+- Split: `royalty + cost + amazon = answered price`, where cost is printing rounded to whole cents, or delivery when 70% applies, else 0. `amazon` is the remainder. When `deliveryExceedsShare`, royalty is 0, cost is `min(delivery, price)`, and `amazon` is the remainder, never negative.
+- Share of list price = `round(royalty × 10,000 ÷ price)` basis points.
+- Copies a month = `ceil(goal ÷ royalty)`, or null when the royalty is $0.00.
+- Rounding: every amount the engine returns is whole cents. In-between print costs keep $0.0001. Each print royalty and the Amazon.com minimum round once, to the nearest cent. Only the Expanded Distribution break-even rounds up. eBook amounts round to the nearest cent with `Math.round`, as the helpers do. These match KDP's own calculator in ten checked cases.
+
+**Domain limits answer instead of failing.** A price below the minimum or above the maximum is not a field error. The engine answers at the nearest allowed price and reports which limit it hit. For Expanded Distribution, a price below the break-even answers at the break-even price with `limit.kind` `below-break-even`, so the result never shows a negative royalty and never claims KDP's minimum. Page counts outside KDP's range for the setup are field errors, because no nearby page count is a useful answer for the person's book.
+
+**Next-step comparison.** At most one, picked in this order:
+
+1. Amazon.com print, answered price below $9.99, and $9.99 within the maximum: the royalty at $9.99 (`rate-step`).
+2. Expanded Distribution: the Amazon.com royalty at the same price (`other-channel`). The Amazon.com minimum is always at or below the Expanded Distribution break-even price, so this always exists.
+3. eBook, 70% applied, or `deliveryExceedsShare`: the 35% royalty at the same price (`other-plan`).
+4. eBook, plan 35, price inside the band: the 70% royalty at the same price (`other-plan`).
+5. eBook, price outside the band (either plan): the 70% royalty at the nearest band edge, $2.99 or $12.99 (`seventy-band`). Skip if that edge is below the eBook minimum.
+6. Otherwise none.
+
+**Curve for the chart.** Built by the engine so the chart and the answer always agree.
+
+- Lower bound: the lowest minimum among the plotted series. Upper bound: the larger of the answered price × 1.5 rounded up to the next `.99`, and $14.99 for print or $15.99 for eBook, capped at the format maximum.
+- Prices: 48 evenly spaced whole-cent prices from lower to upper, plus the lower bound, upper bound, answered price, and every rule boundary in range ($9.98 and $9.99 for Amazon.com print; $2.98, $2.99, $12.99, and $13.00 for eBook). Sorted and unique.
+- Series, the person's selection first:
+  - Amazon.com print: one series, `amazon`, from the Amazon.com minimum.
+  - Expanded Distribution: `expanded` from its break-even price, then `amazon` from the Amazon.com minimum.
+  - eBook plan 70: `plan70` only for prices from $2.99 (or the minimum, if higher) to $12.99, floored at $0.00, then `plan35` across the range.
+  - eBook plan 35: `plan35`, then `plan70` as above.
+- Mark: the answered price and its royalty.
+
+**Unknowns and privacy.** No unknown values in a valid result. Nothing leaves the browser. A shared link holds only the inputs.
+
+### Backend contract
+
+New file `lib/kdp/royalty-calculator.ts`. The frontend calls only this.
+
+```ts
+export type KdpRoyaltyCalculatorField =
+  | "format" | "listPrice" | "pageCount" | "interior" | "trimId" | "paper"
+  | "channel" | "fileSize" | "plan" | "monthlyGoal";
+
+export type KdpRoyaltyCalculatorInput = Readonly<{
+  format: string;
+  listPriceText: string;
+  pageCountText: string;
+  interior: string;
+  trimId: string;        // "" → "6x9"
+  paper: string;         // "" → "white"
+  channel: string;       // "" → "amazon"; paperback only
+  fileSizeText: string;  // "" → 2 MB
+  plan: string;          // "" → "70"
+  monthlyGoalText: string; // "" → not used
+}>;
+
+export type KdpRoyaltyCalculatorResult =
+  | Readonly<{ status: "invalid"; fieldErrors: Partial<Record<KdpRoyaltyCalculatorField, string>> }>
+  | Readonly<{ status: "calculated"; values: KdpRoyaltyCalculatorValues; fieldErrors: Partial<Record<"monthlyGoal", string>> }>;
+
+export type KdpRoyaltyCalculatorValues = Readonly<{
+  format: "paperback" | "hardcover" | "ebook";
+  channel: "amazon" | "expanded" | null;      // null for eBook
+  plan: 35 | 70 | null;                       // selected plan; null for print
+  enteredPriceCents: number;
+  priceCents: number;                         // the answered price, after any limit
+  limit: null | Readonly<{ kind: "below-minimum" | "below-break-even" | "above-maximum"; priceCents: number }>;
+  rate: 35 | 40 | 50 | 60 | 70;               // applied rate
+  seventyOutsideBand: null | "below" | "above"; // plan 70 but price outside $2.99–$12.99
+  deliveryExceedsShare: boolean;
+  royaltyCents: number;                       // never negative
+  split: Readonly<{ royaltyCents: number; costCents: number; amazonCents: number }>;
+  costKind: "printing" | "delivery" | null;
+  printing: null | Readonly<{ enteredPages: number; printedPages: number; costCents: number; fixedCents: number; pageCents: number }>;
+  delivery: null | Readonly<{ fileSizeMB: number; defaultSize: boolean; costCents: number }>; // costCents even when 35% applies
+  minimumPriceCents: number;                  // lowest price for the selected channel or plan
+  minimumKind: "kdp" | "break-even";          // "break-even" only for Expanded Distribution
+  maximumPriceCents: number;
+  shareBasisPoints: number;
+  comparison: null | Readonly<{
+    kind: "rate-step" | "other-channel" | "other-plan" | "seventy-band";
+    priceCents: number;
+    rate: number;
+    royaltyCents: number;
+  }>;
+  goal: null | Readonly<{ goalCents: number; copies: number | null }>; // null when no goal or the goal is invalid
+  curve: Readonly<{
+    series: readonly Readonly<{ id: "amazon" | "expanded" | "plan70" | "plan35"; points: readonly (readonly [priceCents: number, royaltyCents: number])[] }>[];
+    mark: Readonly<{ priceCents: number; royaltyCents: number }>;
+  }>;
+  rulesVersion: string;                       // KDP_ROYALTY_VERSION
+}>;
+
+export function calculateKdpRoyaltyEstimate(input: KdpRoyaltyCalculatorInput): KdpRoyaltyCalculatorResult;
+```
+
+- Field errors are short sentences for the field, final wording from the writing round. Page-limit errors name the range and KDP, such as "KDP prints 24 to 828 pages for this setup." An interior, trim, or paper value the binding doesn't offer is a field error on that field.
+- An invalid monthly goal returns `calculated` with `goal: null` and the goal error. Every other field error returns `invalid`.
+- Series labels and all display words live in the frontend.
+- Remove the old `calculateKdpRoyalty` and the types and private helpers only it used from `lib/kdp/royalty.ts`. Keep every exported helper, constant, `KdpPricePoint`, and `KDP_ROYALTY_VERSION`, because `minimum-list-price.ts` and `price-profit.ts` use them. Don't change their results.
+- Don't change the shared US tables or `KDP_ROYALTY_VERSION`. Research rechecked groundwood, its page limits, and the hardcover cost table and page range on 2026-10-11, and they match KDP.
+
+### Known examples
+
+Worked from the KDP rules in the research. Rows marked "verified" match the official KDP calculator or competitors in the research.
+
+| Case | Inputs | Expected |
+| --- | --- | --- |
+| Opening example, verified | Paperback, 200 pages, black and white, $12.99 | Printing $3.40, rate 60%, royalty $4.39, Amazon $5.20, minimum $6.80, share 33.80% |
+| Rate step, verified | Same, $9.98 | Rate 50%, royalty $1.59, comparison `rate-step` at $9.99: $2.59 |
+| Below minimum | Same, $5.99 | `limit` below-minimum at $6.80, royalty $0.00 |
+| Odd pages, verified | Same, 201 pages, $12.99 | Printed pages 202, printing $3.42 (unrounded $3.424), royalty $4.37, minimum $6.85 |
+| Floor boundary | `getKdpPrintFloorCents(499)` and `(500)` | $9.98 and $9.99 |
+| Long book | Paperback, 600 pages, black and white, $12.99 | Printing $8.20, minimum $13.67, `limit` below-minimum, royalty at $13.67: $0.00 |
+| Large trim | Paperback, 8.5 × 11 in, 120 pages, black and white, $7.99 | Printing $3.04, rate 50%, royalty $0.96 |
+| Expanded Distribution | Paperback, 200 pages, $12.99, channel expanded | Rate 40%, royalty $1.80, minimum $8.50 with `minimumKind` `break-even`, comparison `other-channel` $4.39 |
+| Below ED break-even | Same, $7.99, channel expanded | `limit` below-break-even at $8.50, royalty $0.00, comparison `other-channel` at $8.50: $0.85 |
+| Hardcover | Hardcover, 6 × 9 in, 300 pages, black and white, $24.99 | Printing $9.25, minimum $15.42, royalty $5.74 |
+| eBook 70%, verified | eBook, $4.99, 2 MB | Delivery $0.30, royalty $3.28, comparison `other-plan` 35%: $1.75 |
+| eBook 70% at 5 MB, verified | eBook, $4.99, 5 MB | Delivery $0.75, royalty $2.97 |
+| Top of band | eBook, $12.99, 2 MB | Royalty $8.88 |
+| Above band, verified | eBook, $13.00, plan 70 | Rate 35%, royalty $4.55, `seventyOutsideBand` above, comparison `seventy-band` at $12.99 |
+| Above band | eBook, $13.99, 2 MB, plan 70 | Rate 35%, royalty $4.90, comparison $12.99 on 70%: $8.88 |
+| eBook minimum by size | eBook, $0.99, 5 MB | `limit` below-minimum at $1.99, rate 35%, royalty $0.70 |
+| Delivery exceeds share | eBook, $2.99, 30 MB, plan 70 | Delivery $4.50, royalty $0.00, `deliveryExceedsShare`, comparison 35%: $1.05 |
+| Goal | Opening example, goal $1,000 | 228 copies |
+| Invalid price | `abc`, `0`, `12.999` | `invalid`, listPrice error |
+| Invalid pages | Paperback, 6 × 9 in, white, 829 pages | `invalid`, pageCount error naming 24 to 828 |
+| Hardcover short | Hardcover, 60 pages | `invalid`, pageCount error naming 75 to 550 |
+| Invalid goal | Opening example, goal `-5` | `calculated`, royalty $4.39, `goal: null`, monthlyGoal error |
+
+### Ownership
+
+- Sol builds: `lib/kdp/royalty-calculator.ts`, the cleanup in `lib/kdp/royalty.ts`, and a rewrite of `tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs` with the examples above. The route's database rows and `layout.tsx` already exist, so no preview row or route file.
+- Opus builds: `app/(site)/(tools)/kdp-royalty-calculator/page.tsx`, `kdp-royalty-calculator.tsx`, `kdp-royalty-calculator-from-url.tsx`, a CSS module only if the shared workbench can't express the result grid, and later the `content/*.mdx` files. Card art: review the existing `kdp-royalty-calculator` art against the brief below and redraw only if it doesn't read.
+
+### Catalog placement
+
+- Primary: **KDP tools** (`/kdp-tools`). Its article already lists this tool under "Working out what you earn per sale."
+- Secondary: none. No other catalog serves authors.
+
+Card art (`toolSpot`, key `kdp-royalty-calculator`, already registered in `lib/card-art.ts`):
+
+- Takeaway: each copy sold pays the author a share of its price.
+- Focal subject: a closed book.
+- Supporting relationship: a small stack of coins beside it, the author's share.
+- Tone: neutral and practical. No price tags, numbers, or words.
+
+The existing art (`royaltyBook`, a book and coins) already matches this brief. The frontend round checks it at card size in both themes.
+
+## Interface
+
+### Flow
+
+- User question: "How much do I earn per copy at this price?"
+- Lead answer: royalty per copy, such as `$4.39`.
+- Opens with: Paperback, $12.99, 200 pages, black and white. Advanced empty. Result showing `$4.39`, marked `Example`.
+- Button: `Calculate royalty`, with a quiet `Reset` beside it.
+
+### Inputs
+
+| Input | Basic or Advanced | Required or optional | Hint, one sentence or none | What it changes in the result |
+| --- | --- | --- | --- | --- |
+| Format | Basic | Required | None | Which rules apply, which fields show, every number |
+| List price (suffix `USD`) | Basic | Required | "The price readers pay on Amazon.com, before any sale." | Royalty, rate, split, mark on the chart |
+| Page count (suffix `pages`, print) | Basic | Required | "Every page in your interior file, blanks included." | Printing cost, minimum, page limit |
+| Interior (print) | Basic | Required | "Standard color suits color photos; premium color suits picture books." | Printing cost, minimum, page limit |
+| Trim size (print) | Advanced | Optional, default 6 × 9 in | "Empty uses 6 × 9 in. Larger trims cost more per page." | Printing cost, page limit |
+| Paper (print, black and white only) | Advanced | Optional, default White | "Cream allows fewer pages. Groundwood costs less." | Page limit, printing cost (groundwood) |
+| Sales channel (paperback) | Advanced | Optional, default Amazon.com | "Expanded Distribution sells to bookstores and libraries at 40% minus printing." | Rate, royalty, break-even price, a second chart line |
+| Converted file size (suffix `MB`, eBook) | Advanced | Optional, empty uses 2 MB | "KDP shows it on the pricing page after you upload. Empty uses 2 MB." | Delivery cost on 70%, 35% minimum price |
+| Royalty plan (eBook) | Advanced | Optional, default 70% | "KDP pays 70% only from $2.99 to $12.99." | Which plan leads, comparison, chart order |
+| Monthly royalty goal (suffix `USD`) | Advanced | Optional, empty not used | "Shows how many copies a month earn this much." | Adds a copies-a-month number |
+
+Format, Interior, Paper, Sales channel, and Royalty plan are choice rows, since each has two or three options. Trim size is a select. Hint wording is a draft; the writing round finalizes it.
+
+Format shows different fields, which is a format's own inputs swapping, not a reveal. Values are kept when switching formats, so switching back restores them. If a trim, interior, or paper isn't offered for the new binding, it falls back to 6 × 9 in, black and white, or white.
+
+Advanced disclosure name, by format:
+
+- Paperback: `Trim, paper, channel, and goal`
+- Hardcover: `Trim, paper, and goal`
+- eBook: `File size, plan, and goal`
+
+Its closed summary is `uiSetSummary(count)`, counting fields that differ from their default or are filled.
+
+### Result
+
+Order: answer, split bar, supporting numbers, chart, actions.
+
+1. **Answer.** `UiPrimaryResult`, label `Royalty per copy`, value such as `$4.39`, detail `on a $12.99 paperback`. A `UiStatusWord` beside it only when something could mislead: `Example`, `Below KDP minimum`, `Below break-even`, `Above KDP maximum`, `Paid at 35%`, or `Delivery tops the 70% share`. When a limit applies, the value becomes the limit price, labeled `Lowest price KDP allows`, `Expanded Distribution break-even`, or `Highest price KDP allows`, and the detail says what it earns, such as `earns $0.00 a copy`.
+2. **Split bar.** `UiAllocationBar` of the answered price: `Your royalty` (first data color), `Printing` or `Delivery, 2 MB` (neutral medium), `Amazon` (neutral light). It shows what the numbers alone don't: where the rest of the price goes, and why 70% isn't 70% of the price. The delivery label names the file size, so the 2 MB default is visible. The 35% plan has two parts. When printed pages differ from entered pages, the label reads `Printing, 202 pages`.
+3. **Supporting numbers.** `UiMetricGroup`, three or four items:
+   - `Royalty rate`: `60%`, `40%`, `70%`, or `35%`. Hint for eBook 70%: "Taken after the delivery cost."
+   - `Lowest list price`: the KDP minimum for this setup. Hint: "KDP sets it so your share covers printing." (eBook: "KDP sets it by file size.") For Expanded Distribution the label is `Break-even price`, with the hint "Where 40% covers printing. KDP's minimum for this channel may be higher."
+   - `Share of list price`: `33.8%`. Hint: "This is also your break-even ACoS for Amazon ads."
+   - The comparison, when there is one: `At $9.99` → `$2.59`; `Amazon.com only` → `$4.39`; `On the 35% plan` → `$1.75`; `On the 70% plan` → `$X`; `At $12.99 on 70%` → `$8.88`.
+   - `Copies a month for $1,000` → `228`, when a goal is set. `—` when the royalty is $0.00.
+4. **Chart.** `UiLiveChart`, kind `line`, `format` and `xFormat` `currency`, title `Royalty at each list price`, height 280 (260 on phones). Series labels: `Amazon.com`, `Expanded Distribution`, `70% plan`, `35% plan`. One mark, `Your price`, at the answered price. The print line steps up at $9.99. The eBook 70% line stops at $12.99 while the 35% line runs on, so the drop is plain. It replaces the old price table: hover gives the royalty at any nearby price.
+5. **Actions.** `UiCopyAction` `Copy summary` (format, price, rate, royalty, printing or delivery with fixed and per-page cost, minimum, setup) and `UiShareAction` `Copy link`.
+
+No sources, dates, caveats, or advice in the result. They go in the page content.
+
+### Components
+
+Existing shared components:
+
+- `ToolWorkbench`, `ToolFieldRow`, `ToolResult` from `@/app/ui/tools/tool-workbench`
+- `UiChoiceGroup`, `UiTextField`, `UiNumberField`, `UiSelect`, `UiDisclosure`, `uiSetSummary`, `UiButton`, `UiCopyAction`, `UiShareAction`, `uiOption` from `@/app/ui/controls`
+- `UiPrimaryResult`, `UiStatusWord`, `UiStatus`, `UiAllocationBar`, `UiMetricGroup`, `UiActionRow` from `@/app/ui/display`
+- `UiLiveChart` from `@/app/ui/charts/chart-client`, using line `marks` for `Your price`
+- `useInitialQuery` from `@/app/ui/tools/use-initial-query`
+
+New or improved shared components: none. The line chart's `marks`, the step line (the gallery's "Line with a mark" example is a royalty curve), and the allocation bar's per-segment tones already cover this tool.
+
+Tool-specific components:
+
+- `KdpRoyaltyCalculator`: form state per field as text, the press-to-calculate flow, stale state, error focus, Advanced open on an Advanced error, and the result.
+- `KdpRoyaltyCalculatorFromUrl`: reads a shared link with `useInitialQuery()` and renders the tool with `key={query.key}`. Params: `format`, `price`, `pages`, `interior`, `trim`, `paper`, `channel`, `size`, `plan`, `goal`. An unknown value for a choice falls back to its default.
+
+### Layout
+
+Desktop, inside the 66rem working width:
+
+```
+[ Format: Paperback | Hardcover | Kindle eBook ]   [ List price ______ USD ]
+[ Page count ____ pages ]                          [ Interior: B&W | Standard | Premium ]
+> Trim, paper, channel, and goal                                    Not used
+    [ Trim size  6 × 9 in ▾ ]   [ Paper: White | Cream | Groundwood ]
+    [ Sales channel: Amazon.com | Expanded ]   [ Monthly royalty goal ____ USD ]
+[ Calculate royalty ]  Reset                                  Inputs changed
+──────────────────────────────────────────────────────────────────────────────
+Royalty per copy  [Example]        ████████████▒▒▒▒▒▒▒▒▒░░░░░░░░░░░░░░░░░
+$4.39                              ■ Your royalty $4.39  ■ Printing $3.40
+on a $12.99 paperback              ■ Amazon $5.20
+──
+Royalty rate 60% · Lowest list price $6.80 · Share of list price 33.8% · (comparison)
+──
+Royalty at each list price  (full width, 280px, Your price marked)
+[ Copy summary ] [ Copy link ]
+```
+
+- Basic: two `ToolFieldRow`s for print, one for an eBook (Format and List price). An eBook has no second Basic row.
+- Advanced: one `UiDisclosure` under the Basic rows, with two `ToolFieldRow`s. eBook: File size and Royalty plan, then the goal.
+- Result top: the answer and the split bar side by side, about 2 to 3, the bar vertically centered against the answer. Both hold their own: the answer is large, and the bar plus legend fills its column.
+- Supporting numbers: one full-width row of three or four.
+- Chart and actions: full width.
+
+Phones: every row stacks in reading order. The format choice row may wrap. The answer, then the bar, then the numbers in two columns, then the chart at 260px, then the actions. Nothing overflows the page.
+
+### States
+
+- **Example.** Opens on the example with its result and `Example`. The word goes away after the first press of `Calculate royalty`, even with unchanged values.
+- **Stale.** Any edit, including a format switch or an Advanced field, steps the result back with `ToolResult stale` and shows `Inputs changed` in `UiStatus`. The result never disappears.
+- **Invalid input.** On press, errors show under each field and focus moves to the first. If it's inside Advanced, Advanced opens first. The last good result stays, stepped back.
+- **Invalid goal only.** The main result updates. The goal field shows its error, Advanced opens, and the copies number is left out.
+- **Below the minimum.** The answer becomes the minimum price, `Lowest price KDP allows`, with what it earns. Status `Below KDP minimum`. The split bar, numbers, and chart mark use the minimum. No field error.
+- **Below the Expanded Distribution break-even.** The answer becomes the break-even price, `Expanded Distribution break-even`, with what it earns ($0.00). Status `Below break-even`. The comparison shows the Amazon.com royalty at that price. No field error, and nothing calls it KDP's minimum.
+- **Above the maximum.** Same, at $250 for print or $200 for eBook, `Highest price KDP allows`, status `Above KDP maximum`.
+- **70% outside the band.** Royalty at 35%, status `Paid at 35%`, comparison `At $12.99 on 70%` or `At $2.99 on 70%`.
+- **Delivery exceeds the 70% share.** Royalty `$0.00`, status `Delivery tops the 70% share`, comparison `On the 35% plan`.
+- **Page count outside KDP's range for the setup.** Field error naming the range and KDP. Also used for standard color under 72 pages and hardcover under 75. Last good result stays, stepped back.
+- **Shared link.** Opens and calculates right away. If a value is invalid, the errors show as on press, and the example result stays, stepped back.
+- **Reset.** Returns every field, including Advanced, to the example, and shows its result marked `Example`.
+
+## Content
+
+Written after the frontend. The tool was run with the opening paperback ($12.99, 200 pages), $9.98 and $9.99, a 600-page paperback, Expanded Distribution at $12.99 and $7.99, a $24.99 hardcover, and eBooks at $4.99, $12.99, $13.99, and $2.99 with a 30 MB file. Every number in the copy comes from those runs.
+
+### Search intent and title
+
+The searcher is picking a price and wants the dollars per copy at that price. Top results either skip a format, still use the old $9.99 top of the 70% band, or show a negative number at a price KDP won't allow. This page gives the dollars, where the rest of the price goes, and what nearby prices pay, on the current Amazon.com rules.
+
+- Visible title: keep `KDP royalty calculator: how much do you earn per book sale?`
+- SEO title: keep `KDP royalty calculator for paperbacks, hardcovers, and eBooks`.
+- SEO description, new: `See what you earn per Amazon.com sale of a paperback, hardcover, or Kindle eBook, the lowest price KDP allows, and what nearby prices pay.`
+- Card: keep the name `KDP royalty calculator` and the description `See what you earn per Amazon.com sale for a paperback, hardcover, or eBook.`
+
+### Reader questions
+
+| Question | Where it's answered |
+| --- | --- |
+| How much do I earn on a $12.99 paperback? | Tool answer. Article formula and worked example. |
+| How is KDP royalty calculated? | Article, formula and rate table. |
+| Why does $9.98 earn less than $9.99? | Tool comparison and chart step. Article section. |
+| Should I choose 35% or 70%? What is the delivery fee? | Tool comparison and chart. Article section. |
+| What's the lowest price I can set? | Tool number, and the answer itself when the price is too low. Article section. |
+| What does Expanded Distribution pay? | Tool channel choice. Article section. |
+| Is royalty the same as profit? | Article section. |
+| How many copies a month do I need? | Tool goal. Usage. |
+| What can I spend on ads per sale? | Share of list price hint. Usage. |
+
+### Outline
+
+- Intro: what you get, for which formats, and what to have ready. Two sentences.
+- Usage: what to enter where the form can't say it (page count, file size), how to read the bar, numbers, and chart, and one `Example` (the opening paperback, with a $1,000 goal).
+- Article:
+  - `How is KDP royalty calculated?` Formula, rate table, printing and delivery cost, links to KDP.
+  - `Why does one cent change a paperback royalty by $1?` The $9.98 and $9.99 pair.
+  - `Should you choose 35% or 70% for your eBook?` Delivery cost, the $13.99 drop, the 30 MB case.
+  - `What is the lowest list price KDP allows?` The minimum rule, the 600-page case, eBook minimums by size.
+  - `What does Expanded Distribution pay?` 40% minus printing, the break-even, the unpublished minimum.
+  - `Is a KDP royalty the same as profit?`
+  - `What doesn't this calculator cover?` Scope, rules date, exclusions, next tools.
+
+Left out: input format rules and limits (field errors cover them), odd-page rounding beyond one line, trim and paper cost tables (KDP's pages link them), and price advice (the research found no evidence for a good price).
+
+### Facts, limits, and sources
+
+- Print rates, $9.99 step, print formula, $250 maximum, minimum from printing cost: [Paperback Royalty](https://kdp.amazon.com/en_US/help/topic/G201834330), [Hardcover Royalty](https://kdp.amazon.com/en_US/help/topic/G77F3WPD3KQLJTFS).
+- Printing cost tables and even page counts: [Paperback Printing Cost](https://kdp.amazon.com/en_US/help/topic/G201834340), [Hardcover Printing Cost](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H), [Paperback Submission Guidelines](https://kdp.amazon.com/en_US/help/topic/G201857950).
+- 35% and 70% plans, delivery at $0.15 per MB rounded up to the KB with a $0.01 minimum, 70% eligibility conditions: [Digital Book Pricing](https://kdp.amazon.com/en_US/help/topic/G200634500).
+- $2.99 to $12.99 band from July 7, 2026, eBook minimums by size, $200 maximum: [eBook List Price Requirements](https://kdp.amazon.com/en_US/help/topic/G200634560).
+- Expanded Distribution at 40% minus printing, taxes, and withholding; minimum not published; Rights & Pricing grid: [Expanded Distribution](https://kdp.amazon.com/en_US/help/topic/GQTT4W3T5AYK7L45).
+- Rules checked: October 11, 2026.
+- Avoid: calling a price good or bad, a typical royalty or earnings figure (none exists), calling the break-even KDP's minimum, a 1.5 MB example (a rounding fix is pending), and saying the tool checks KDP acceptance or eligibility.
+
+### Next step
+
+`/kdp-price-profit-calculator` (costs and profit), `/kdp-minimum-list-price-calculator` (price for a target royalty), `/kdp-break-even-acos-calculator` (ad bids), `/kindle-unlimited-kenp-earnings-calculator` (page reads), `/kdp-page-count-estimator` (page count before the final file).
diff --git a/content_docs/kdp-royalty-calculator/writing-and-seo.md b/content_docs/kdp-royalty-calculator/writing-and-seo.md
deleted file mode 100644
index 3fedc318..00000000
--- a/content_docs/kdp-royalty-calculator/writing-and-seo.md
+++ /dev/null
@@ -1,184 +0,0 @@
-# Writing and SEO plan: KDP royalty calculator
-
-Follow `stack127_docs/writing-style.md` for all writing, visual choices, and SEO wording.
-
-Status: ready
-Feasibility: feasible
-Content review: 2026-09-19
-Acceptance path: Main-agent review, then the retained Astra writing session; Luna integrates only accepted words.
-Tool: KDP royalty calculator
-Route: `/kdp-royalty-calculator`
-Depends on: `competitive-report.md`, `implementation-report.md`, `interface-contract.md`, `edge-cases-and-tests.md`, `brief.md`
-SERP checked: 2026-09-16
-Primary medium: Tool UI
-Content depth: The tool answers the selected-price economics first. Supporting copy explains the formula branches, how to read the price floor and derived values, the local estimate boundary, and what to verify in KDP. It stops before demand forecasting, tax accounting, publishing guidance, or KDP submission advice.
-
-## Search intent
-
-| Priority | Query family | Immediate job | Expected result shape | Page response |
-| --- | --- | --- | --- | --- |
-| Primary | `KDP royalty calculator` | Estimate what a US Amazon.com paperback, hardcover, or Kindle eBook sale leaves after the applicable KDP deduction. | A scenario form followed by royalty per sale, cost receipt, price floor, and rate-aware comparison. | The tool UI leads. COPY-01 introduces the estimate and its fixed US scope. |
-| Secondary | `KDP paperback royalty calculator`, `KDP hardcover royalty calculator` | Check print cost, the 50% or 60% rate, and the minimum cost-covering price. | Print inputs and a comparison table at the floor, selected price, and $9.98 or $9.99 boundary. | The print branch and COPY-02 explain the rate band and cost receipt. |
-| Secondary | `KDP ebook royalty calculator`, `KDP ebook delivery fee calculator` | Check the 35% or 70% result after file-size delivery cost and price-band rules. | eBook inputs, effective rate, delivery cost, and a warning when a selected 70% option falls back to 35%. | The eBook branch, COPY-02, and the result details explain the boundary. |
-| Secondary | `KDP minimum price calculator` | Find a price that covers the modeled KDP printing cost or eBook floor. | A minimum valid price with the exact rate-band logic visible in the comparison. | The price floor result and COPY-03 explain that this is a cost-covering floor, not a recommendation. |
-| Secondary | `KDP royalty calculator monthly target` | Turn a positive royalty per sale into the number of copies needed for a chosen monthly amount. | Optional target input and ceiling copy count. | The monthly target region and COPY-03 explain unit math without forecasting demand. |
-
-### Search check record
-
-- Search backend: web connector.
-- Search engines: not individually available through the connector.
-- Queries checked: `KDP royalty calculator`, `KDP paperback printing cost calculator`, `KDP ebook royalty calculator delivery fee`, and `KDP royalty calculator monthly income target`.
-- Result shape: Amazon's official printing-cost and royalty pages appear for the broad and print queries. Third-party calculators appear for quick single-scenario estimates. eBook results surface delivery-cost documentation and rate-band explanations. The monthly-target query is adjacent intent, not the main page job.
-- Browser backend: blocked. Standalone Playwright 1.60.0 was installed, but Chromium launch failed with `sandbox_host_linux.cc:41: FATAL: Check failed. . shutdown: Operation not permitted (1)`. No direct-page Browser QA is claimed. The search check uses the connector results and the ready competitive report's source review.
-- Viewport requested for the blocked direct-page check: 1440 x 900.
-
-### Intent not targeted
-
-- `KDP sales forecast`, `KDP ranking calculator`, `Kindle Unlimited earnings calculator`, and ad performance forecasting: the implementation has no demand, ranking, KU, or campaign data.
-- Non-US marketplace, VAT, GST, withholding-tax, price-matching, promotional, refund, or Expanded Distribution queries: those inputs and formulas are outside the launch contract.
-- `Will KDP accept my book?`: this tool checks local arithmetic against a versioned US rule set. It does not submit a title, inspect files or metadata, or check KDP acceptance.
-
-## Page promise
-
-Use a US Amazon.com KDP scenario to estimate royalty per sale, the cost or delivery deduction behind it, the minimum modeled price, break-even ad headroom, and optional monthly copies. The result is a local estimate and rules check, not a guarantee of what KDP will report for every order and not a KDP acceptance check.
-
-Reading flow: The author chooses a format and enters only its relevant inputs. The result leads with one royalty value, then shows the receipt, floor and margin, exact boundary comparisons, ad ceiling, and optional target math. Supporting copy explains why print and eBook branches differ, then names the exclusions and the KDP checks that still belong in the real publishing workflow.
-
-## Content completeness map
-
-| User question | Where answered | Medium | Evidence | Repetition guard |
-| --- | --- | --- | --- | --- |
-| What is the tool and who is it for? | COPY-01 after the tool introduction | Sentences | `brief.md`; implementation report product decision | Name the self-publishing author and the US Amazon.com pricing task once. Do not restate the result value. |
-| Which inputs, modes, units, sources, or scope choices matter? | Active scenario form and COPY-02 | Tool UI plus Sentences | Interface input contract; implementation inputs and normalization | Let conditional controls carry the inventory. Explain only why format, pages or file size, price, and royalty option change the branch. |
-| How should someone choose meaningful inputs and use it for the real task? | Scenario form, result receipt, and COPY-02 | Tool UI plus Sentences | Brief; interface user task and input contract | Explain representative inputs and boundary checks, not ordinary button operation. |
-| How should the result and its important terms or uncertainty be interpreted? | Result regions and COPY-03 | Tool UI plus Sentences | Interface result contract; implementation assumptions | The UI owns exact values. Copy explains floor, margin, ad ceiling, and target math without repeating the table. |
-| Which concepts or edge cases commonly surprise users? | Rate-aware comparison, eBook fallback warning, odd-page receipt note, and COPY-02 | Table plus Sentences | Edge cases FF-002, FF-003, FF-009, FF-011 | Explain why the boundary changes the answer. Do not list every fixture or duplicate table rows in prose. |
-| What does the tool not inspect, calculate, prove, recommend, or guarantee? | COPY-04 | Sentences | Implementation non-goals and assumptions | State exclusions beside the claim they limit. Do not turn limitations into a large warning panel. |
-| How are user inputs handled? | COPY-04 or COPY-05, beside the scope note | Sentences | Implementation accessibility, privacy, and performance plan; edge cases EC-029 and EC-030 | Say that calculation is local and that v1 does not send inputs to a server, store them, or add them to analytics. Do not promise broader privacy properties. |
-| What should the reader verify or do next? | COPY-05 and calculation details | Sentences plus Tool UI | Official KDP sources; implementation source date and version | Point readers to the current KDP rules and their own KDP workflow. Do not say the tool checks acceptance or replaces KDP. |
-
-## Heading and media outline
-
-| Order | Level and proposed heading | User question | Takeaway, not draft prose | Medium | Evidence | Limit/repetition guard | Writer section ID |
-| --- | --- | --- | --- | --- | --- | --- | --- |
-| 1 | H1: KDP royalty calculator for US print books and eBooks | What does this tool calculate? | The page names the formats and the selected-sale answer. The workbench comes before supporting explanation. | Tool UI | `brief.md`; interface user task | The H1 must not promise profit, demand, or KDP acceptance. | n/a |
-| 2 | Result lead: Royalty per sale | What does one selected-price sale leave under this scenario? | Show one dominant USD royalty with the effective rate and format. | Tool UI | Interface result contract; implementation R13 | This is the primary answer. Do not add a second standalone royalty metric. | n/a |
-| 3 | Result details: Cost receipt and price floor | What KDP deduction produced the result, and what price covers it? | Keep exact fixed, page, printing, or delivery cost beside the minimum modeled price and margin. | Tool UI | Interface result contract; formula contract | The receipt owns cost components. The floor is not a price recommendation. | n/a |
-| 4 | Result details: Price comparison | Which exact price boundaries change the answer? | Compare unique valid rows at the floor, selected price, and relevant print or eBook boundaries. | Table | Implementation comparison equation; edge cases FF-011 | No chart, timeline, cards, or paragraph may repeat the rows. | n/a |
-| 5 | Result details: Ad headroom and monthly target | What can one sale absorb, and how many copies meet my target? | Show maximum break-even spend and ACoS when royalty is positive. Show optional ceiling copies only when a target is entered. | Tool UI | Interface result contract; edge cases FF-010 and FF-013 | Call ad spend a ceiling, not a budget recommendation. Do not call target copies a forecast. | n/a |
-| 6 | H2: What does this KDP royalty calculator estimate? | Who is this for, and what answer should appear first? | Identify the self-publishing pricing task, the three formats, and the local US Amazon.com estimate before the supporting explanation. | Sentences | COPY-01; brief and implementation product decision | Cue the tool without listing every input or promising KDP acceptance. | COPY-01 |
-| 7 | H2: How KDP royalty is calculated for print books and eBooks | Why do the print and eBook answers use different deductions? | Explain list price times the effective rate, then the print cost or eligible eBook delivery deduction. Tie the explanation to the active result. | Sentences | COPY-02; official KDP cost and royalty sources | Do not restate exact comparison values or narrate the form controls. | COPY-02 |
-| 8 | H2: How to read the price floor, ad headroom, and monthly target | What do the supporting numbers mean? | Explain cost coverage, the zero-or-negative royalty boundary, and ceiling unit math. | Sentences | COPY-03; implementation assumptions and partial states | Do not recommend a price, ad budget, or sales target. | COPY-03 |
-| 9 | H2: What this local KDP estimate does not cover | What should this number not be mistaken for? | Separate royalty math from author profit, taxes, refunds, promotions, price matching, demand, and KDP acceptance. | Sentences | COPY-04; implementation non-goals | Keep the limitation connected to the result. Do not add unsupported guarantees. | COPY-04 |
-| 10 | H2: What to verify in KDP before you price or publish | What should I check after using the calculator? | Use the dated official sources and the actual KDP title workflow for the final decision. | Sentences | COPY-05; official KDP sources; source date in implementation report | Say the tool checks a local versioned rule set. Do not imply submission, approval, or live price scraping. | COPY-05 |
-| 11 | Calculation details disclosure | Which rule set and sources support this result? | Keep formula version, source date, Amazon.com and USD scope, standard-distribution boundary, and official links after the economics. | Tool UI | Interface calculation-details contract; implementation source ledger | One quiet evidence region. Do not turn sources into result cards or repeat the lead. | n/a |
-| Usage | H2: Use the tool for your task | Which inputs should I bring, and what should I do with the outcome? | Use the closed Usage Markdown handoff below. | Sentences | Accepted technical artifacts and route behavior | Explain meaningful choices and next action; no button narration or duplicate live results. | COPY-06 |
-
-No marker art, clean chart, or screenshot is planned. The tool's exact comparison table carries repeated numbers more clearly than invented geometry. A screenshot would only be useful after a real published interface exists and would not explain the formula.
-
-## Formula explanation
-
-| Concept | What the reader needs | Presentation | Example/source | Caveat placement |
-| --- | --- | --- | --- | --- |
-| Print royalty | For paperback and hardcover, the modeled royalty is `effective rate x list price - printing cost`. Amazon.com print rates are 50% through $9.98 and 60% from $9.99. | Short connected explanation beside the result, with the exact rate and cost left to the receipt and table. | Implementation formula contract; [KDP print royalty rules](https://kdp.amazon.com/en_US/help/topic/G201834330) | State the rate boundary beside the explanation. |
-| Print cost | Fixed and per-page costs depend on binding, trim class, interior profile, and normalized even page count. | Explain the cost drivers once. Let the receipt show fixed cost, page cost, and total where applicable. | Implementation formula contract; [KDP paperback printing costs](https://kdp.amazon.com/en_US/help/topic/G201834340); [KDP hardcover printing costs](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H) | Explain odd-page rounding beside the effective-page detail, not in a repeated formula block. |
-| Print price floor | The floor is solved by rate band. Try the 50% cost-covering price first; if it crosses $9.98, solve in the 60% band and clamp to $9.99. | Explain the piecewise decision in COPY-02 or COPY-03. Show the resulting floor in the UI. | Implementation formula contract; FF-007; [KDP price guidance](https://kdp.amazon.com/en_US/help/topic/G200641280) | Call it the minimum modeled price, not the right price or a recommendation. |
-| eBook delivery and rate | An eligible 70% eBook uses `70% x (list price - delivery cost)`. Delivery uses the rounded-up file size and the versioned US rate, with a $0.01 minimum. The 35% equation does not subtract delivery. | Use the eBook receipt and one explanatory sentence. | Implementation formula contract; [KDP digital book pricing](https://kdp.amazon.com/en_US/help/topic/G200634500) | Place the 70% band warning beside the result when the selected price is outside $2.99 to $12.99 and the tool falls back to 35%. |
-| eBook price floor | The 35% floor changes with file size: $0.99 below 3 MB, $1.99 from 3 MB to less than 10 MB, and $2.99 at 10 MB or more. The 70% floor is $2.99. | State the bands only where a reader needs to understand a validation message or floor. | Implementation formula contract; [KDP eBook list price requirements](https://kdp.amazon.com/en_US/help/topic/G200634560) | Keep the exact floor with the invalid-input recovery. Do not imply that a floor predicts demand. |
-| Ad headroom and target math | Maximum break-even ad spend equals positive royalty per sale. Break-even ACoS is royalty divided by list price. Copies for a target use ceiling division of target cents by displayed royalty cents. | Explain as derived unit math after the table. | Interface result contract; FF-010 and FF-013 | If royalty is zero or negative, show no positive headroom, omit ACoS, and make a positive target unknown. |
-| Rounding and provenance | Money displays to two decimals, rates to whole percentages, and margin or ACoS to one decimal place. The answer uses `kdp-us-amazon-com-2026-09-16-v1` and the source date shown by the tool. | Put the version and date in calculation details. | Implementation rounding and versioning; FF-012 | Say the source date identifies the local rule set. It is not a live KDP response. |
-
-## Metadata proposal
-
-- Registry label: `kdp royalty calculator`
-- Meta title: `KDP royalty calculator for US print books and eBooks`
-- Meta description: `Estimate US KDP royalty per sale for a paperback, hardcover, or eBook. Compare rate bands, printing or delivery costs, price floors, ad headroom, and monthly copies. Local estimate, not KDP acceptance.`
-- Page type: `WebPage`
-- Publication recommendation: `Unpublished until separately approved. This content stage must not add a registry row, change publication state, or make the route indexable.`
-
-These are central-registry proposals. They are not instructions to add route-local metadata, canonicals, robots rules, sitemap logic, or JSON-LD.
-
-## Internal links
-
-Related KDP tools exist in the route inventory but remain unpublished. The conditional paths below can become links only after their exact registry routes are published. Do not publish a destination as part of content integration.
-
-| Direction | Destination | Reader reason | Anchor intent | Placement |
-| --- | --- | --- | --- | --- |
-| Outgoing, conditional | `/kdp-book-setup-calculator` | Prepare print dimensions after choosing a format and page count. | `KDP book setup calculator` | Final next-step section, only after publication. |
-| Outgoing, conditional | `/kdp-page-count-estimator` | Estimate a paperback page range before the final PDF exists. | `KDP page count estimator` | Input preparation, only after publication; estimated pages are not final print pricing evidence. |
-
-The official KDP links in the source ledger are outbound evidence links, not internal links.
-
-## Manual prose handoff
-
-### Sections reserved for later manual writing
-
-| Section ID | Heading | Purpose | Required facts and sources | Useful depth and stopping point | Banned claims or repetition |
-| --- | --- | --- | --- | --- | --- |
-| COPY-01 | How this KDP royalty calculator helps with a US pricing decision | Identify the self-publishing author, the three supported formats, the Amazon.com and USD scope, and the selected-sale question. | Use `brief.md`, the implementation product decision, and the fixed-scope assumptions. | One connected introduction that cues the tool and explains what answer appears first. Stop before describing every field or repeating the result. | Do not call it a profit calculator, forecast, recommendation engine, acceptance checker, or live KDP quote. |
-| COPY-02 | How KDP royalty is calculated for print books and eBooks | Explain the print cost and rate branches, eBook delivery deduction, 70% fallback, price floors, and even-page normalization only as needed to understand the UI. | Use implementation formula sections, interface input and result contracts, FF-002, FF-003, FF-008, FF-009, and the official KDP sources in the ledger. | Follow the reader from list price and format to the cost receipt and boundary table. Stop once the reader can explain why a rate or cost changes. | Do not restate all trim IDs, cost constants, comparison rows, or ordinary button steps. Do not present the local formula as KDP acceptance. |
-| COPY-03 | How to read the price floor, ad headroom, and monthly target | Explain the floor as cost coverage, ad headroom as a break-even ceiling, and target copies as ceiling unit math. | Use interface result contract, implementation assumptions, FF-007, FF-010, FF-013, and non-positive-state rules. | Cover the decisions the supporting result regions answer. Stop before demand, campaign performance, or price advice. | Do not recommend a list price or ad budget, call copies a sales forecast, or repeat the table's exact values. |
-| COPY-04 | What this local KDP estimate does not cover | Set the boundary around author profit, taxes, VAT, refunds, price matching, promotions, other marketplaces, Expanded Distribution, demand, and stored or transmitted input data. | Use implementation scope, non-goals, assumptions, technical privacy plan, and edge cases EC-017, EC-029, and EC-030. | Keep the caveats close to the claims they qualify. Stop after the reader understands that the calculation runs locally and is not a KDP acceptance check. | Do not make broader privacy claims, add legal or tax advice, imply a result is guaranteed, or build an oversized caveat panel. |
-| COPY-05 | What to verify in KDP before you price or publish | Tell the reader to use the dated official sources and the actual KDP workflow for final confirmation. | Use the five official KDP source pages in the ledger, the version string and source date, and the implementation publication boundary. | Give the next verification step and explain that rules can change. Stop before giving submission instructions or claiming that the tool submits or checks a book. | Do not say KDP accepted a price, title, file, or order. Do not claim live scraping, an API check, or current account-specific behavior. |
-| COPY-06 | Task-oriented usage | Explain input preparation, meaningful choices, states, and next verification. | Closed Usage Markdown handoff and accepted technical artifacts. | One concise connected guide; use steps only where order changes the outcome. | No live-result narration, unimplemented features, or duplicate supporting explanations. |
-
-### Page constraints
-
-- Keep the words estimate, local calculation, source date, and KDP acceptance distinct. A source-rule match is not a submission or acceptance result.
-- The tool UI owns exact economics and repeated price comparisons.
-- Leave unresolved future routes and publication decisions as review notes, not public copy.
-
-### Tool-build exclusion
-
-`$stack127-tool-build` must not draft or integrate these sections. The user supplies them in a later content pass.
-
-## Source ledger
-
-- [KDP paperback printing costs](https://kdp.amazon.com/en_US/help/topic/G201834340), checked 2026-09-16. Supports US paperback fixed and per-page costs, trim classes, page limits, and the printing-cost part of the print floor.
-- [KDP print royalty rules](https://kdp.amazon.com/en_US/help/topic/G201834330), checked 2026-09-16. Supports Amazon.com 50% and 60% print rate bands, the royalty equation, and print price limits.
-- [KDP hardcover printing costs](https://kdp.amazon.com/en_US/help/topic/GHT976ZKSKUXBB6H), checked 2026-09-16. Supports hardcover fixed and per-page cost branches and page limits.
-- [KDP hardcover royalty rules](https://kdp.amazon.com/en_US/help/topic/G77F3WPD3KQLJTFS), checked 2026-09-16. Supports the separate hardcover royalty contract.
-- [KDP eBook list price requirements](https://kdp.amazon.com/en_US/help/topic/G200634560), checked 2026-09-16. Supports the Amazon.com eBook price bands and file-size-dependent 35% floors.
-- [KDP digital book pricing](https://kdp.amazon.com/en_US/help/topic/G200634500), checked 2026-09-16. Supports 35% and 70% equations, US delivery cost, kilobyte rounding, and the minimum delivery cost.
-- [KDP price guidance](https://kdp.amazon.com/en_US/help/topic/G200641280), checked 2026-09-16. Supports the distinction between a calculated minimum list price and the author's final pricing decision.
-- Search result review via the web connector, checked 2026-09-16. Supports the current SERP shape recorded under Search intent. Search engines were not individually available, and no direct-page Browser QA is claimed because the standalone Playwright launch was blocked by the host sandbox.
-
-## Open questions and blockers
-
-- No content blocker remains. The page is ready for the later manual prose pass, but the tool and route remain unpublished until separately approved through the central publication workflow.
-
-## Usage Markdown handoff
-
-Disposition: Closed and feasible for the retained Astra writing session after main acceptance.
-
-### Assignment and reading order
-
-COPY-06 owns `usage_markdown`: explain the real task, inputs worth preparing, meaningful mode choices, important state distinctions, and the next verification. The existing manual assignments own the introduction, supporting explanations, metadata, and identified interface review only. Where an older assignment discusses how to choose an input, move that instruction into this usage assignment and retain only its conceptual explanation below. Do not repeat it in both fields. Interface inventories are review-only; this plan does not authorize implementation or rewriting dynamic findings.
-
-### Technical facts and meaningful inputs
-
-Choose paperback, hardcover, or eBook under the fixed Amazon.com USD scope. Print uses supported trim/interior/paper, even-normalized page count, and list price; invalid cost-table combinations block an answer. Print rate is 50% through $9.98 and 60% from $9.99. The cost-covering floor is solved across those two bands. eBook 70% price eligibility is $2.99–$12.99 in the checked US source; outside it the modeled result falls back to 35% with a warning. The 70% branch deducts delivery before multiplying, while 35% has no delivery deduction. Delivery uses rounded-up file KB, $0.15/MB, and a $0.01 minimum. Monthly target is optional; blank omits it, zero is zero, and positive targets use ceiling copies only for positive royalty.
-
-### State interpretation and recovery
-
-Distinguish unsupported inputs, invalid price or cost-table selection, eBook 70%-to-35% fallback, non-positive royalty, and an absent monthly target. Break-even ad spend is not a recommended budget; undefined target copies or ACoS must not be rendered as zero or infinity.
-
-### Limitations and next action
-
-Royalty is not author profit. Exclude taxes, refunds, promotions, price matching, demand, other marketplaces, and Expanded Distribution. Selecting 70% assumes other eligibility conditions; this tool does not verify public-domain status, account requirements, or the required relationship to a physical edition's price. The accepted contract uses integer cents: round each printing or delivery cost at its cost boundary, then use those cents for royalty, price floor, comparisons, and target math. Explain displayed USD estimates without claiming microdollar precision or coverage of an unrounded cost.
-
-### Input handling boundary
-
-Scenario arithmetic runs locally. Do not claim that the tool contacts an Amazon account, submits a price, or obtains a live account-specific quote. The implementation and accepted technical evidence support only these route-specific statements. Do not infer a general retention, logging, analytics, cookie, or anonymity policy.
-
-### Content, media, and list requirements
-
-Keep the interactive tool first. Preserve all outline tables and exact result media; their repeated fields belong in tables, not comparison paragraphs. Existing output values, counts, findings, formulas, and captions stay in the live result rather than a second narrative. No new screenshot, marker drawing, generated illustration, or chart is required. If an ordered list is used, it must represent dependent task steps; use an unordered list only for genuinely independent checks. Do not add a generic FAQ or a list-shaped summary of every control. Every retained table must ship with useful headers and its limitation, not merely a heading placeholder.
-
-### Source ledger and links
-
-Use the existing source ledger for attributable claims, with links at the point of explanation. The ready implementation, interface, edge-case, and brief artifacts govern what this tool actually does; official sources govern external rules. Local assumptions must be labeled rather than attributed to a standards body or platform. Preserve the ledger's checked dates; a content review is not a claim that every source was freshly reverified. Conditional internal destinations: /kdp-book-setup-calculator; /kdp-page-count-estimator. Include them only when the exact route is published at integration; all new batch tools remain unpublished. If a destination is unavailable, omit the link rather than invent a URL or publish its target.
-
-### Feasibility and ownership
-
-The accepted implementation can support this plan without new controls, engines, media, data sources, or implementation work. Astra supplies words only after acceptance. Luna performs content integration later. Neither this plan nor its validator result changes database content, registry publication, tool version, or deployment.
diff --git a/dev-space/simple-tools-plan.md b/dev-space/simple-tools-plan.md
new file mode 100644
index 00000000..27a9c5c1
--- /dev/null
+++ b/dev-space/simple-tools-plan.md
@@ -0,0 +1,141 @@
+# Simple tools plan
+
+Goal: every stack127 tool answers the questions most people bring to it in a few seconds, without reading. Pros still get accurate, robust options, but those stay optional and tucked away.
+
+The free trial conversion calculator showed the problem. It asks for cohorts, a follow-up window, and cohort age before giving a number, has about 90 words of helper text inside the tool, uses a checkbox to reveal more fields, and puts a sources table in the result. Competitors such as mowt.com and coachway.io answer "what's my rate" with three plain inputs.
+
+The same pattern shows up across the catalog: 19 of the 20 SaaS calculators have text under fields, 5 use checkboxes to reveal fields, and only 3 use a chart. Our own docs and skills produced this, so the fix starts there, not in one tool.
+
+## The system decides, not the user
+
+Each tool's plan settles three things on its own.
+
+1. **Who uses it and what they ask.** A written opinion: who most people are, their 2 or 3 questions, and what Basic answers. What Advanced adds, for whom, and what we leave out, with reasons.
+2. **When the result shows.**
+   - Live, for math that runs in the browser.
+   - After a button, for network lookups, rate limits, slow work, or long input, like the DNS tools.
+   - Shown on load, only when an example result teaches the tool without misleading anyone.
+3. **Comparison numbers, only where real data exists.** Research finds published ranges with source, date, and who was measured. The plan decides if they mean anything for this tool. The result shows where the person sits next to the range, never a grade. Niches differ, so we never call a number good or bad. If sources disagree too much, show nothing. Sources go in the article, not the result.
+
+## Phase 1: Docs and skills
+
+Opus writes, the user reviews.
+
+- [x] `stack127_docs/tool-interface.md`: Basic and Advanced by default with `UiDisclosure`, optional Advanced fields, every input changes the result, no checkbox reveals, `?` hints instead of field text, personal visual results with a share link, result timing, and neutral comparisons.
+- [x] `stack127_docs/shared-ui.md`: the hint, the comparison marker, the share link, and the Advanced summary.
+- [x] `stack127_docs/writing-style.md`: text inside a tool is labels and one-sentence hints, nothing else.
+- [x] `stack127_docs/tool-pipeline.md`: the user-needs gate and the rework path for existing tools.
+- [x] Tool research skill: user needs and comparison numbers first.
+- [x] Tool product plan skill: the written opinion, result timing, and comparison decision.
+- [x] Tool interface plan skill: Basic inputs, Advanced inputs, hints, and one visual result.
+- [x] Tool frontend skill: build to those rules.
+- [x] Tool writing skill: hint sentences, no text in the tool.
+- [x] Tool audit skill: the new checklist.
+- [x] Interface design and tool orchestrator skills: match the rework path.
+
+## Phase 2: Shared components
+
+Opus builds, Sol reviews.
+
+- [x] `?` hint: hover, keyboard focus, and tap. A `hint` option on every field type. `UiHint` in `app/ui/controls.tsx`.
+- [x] Advanced summary on `UiDisclosure`, such as "Not used" or "2 set", while closed. `uiSetSummary` in `app/ui/controls.tsx`.
+- [x] Comparison marker: the person's value on a published range, no grade. `UiRangeMarker` in `app/ui/display.tsx`.
+- [x] Share link action, built on the existing `useInitialQuery` URL pattern. `UiShareAction` in `app/ui/controls.tsx`.
+- [x] All of these on `/components-ui`.
+- [x] Sol review of the Phase 2 code. Passed on round 2 after five small accessibility and edge-case fixes.
+
+## Phase 2b: Lean docs and open visuals
+
+The first pass still boxed the model in. `tool-interface.md` was 3,800 words, mostly general UI advice a strong model already knows, and it listed a fixed menu of visuals. Skills repeated the docs. Rule: skills give a short path and make the model think; docs hold the facts, directly.
+
+- [x] `tool-interface.md` rewritten to the stack127-specific decisions only: 3,800 words down to about 1,100.
+- [x] Visuals are open: pick the form that makes the answer obvious, from any ECharts type, a shared component, or a custom SVG. Add a chart type when it's missing.
+- [x] Tool skills rewritten as short paths that link to the docs, about 530 lines removed. The version rules live once, in `tool-pages.md`.
+- [x] Chart wrapper: funnel, gauge, treemap, sankey, and radar added, with gallery examples. They load in the browser only on pages that draw one, so existing chart pages don't get heavier.
+- [x] Sol review of the chart code. Passed on round 4 after edge-case fixes for empty, invalid, and looping data.
+
+## Phase 2c: Examples, feel, and one writer
+
+- [x] One Opus session plans the tool, builds the frontend, and writes every word, including the page content. The audit gives the fresh read.
+- [x] Live tools open with realistic example values and their result, marked `Example` until the first edit. Button tools never run on their own.
+- [x] "How a stack127 tool feels": the same shared parts, order, accent use, and type, without a fixed layout.
+- [x] "Good and bad tools": three good sketches of different kinds (MRR goal, domain expiry, RAID planner) and three bad patterns. None of them is a pilot tool, so the pilots still test the docs.
+- [x] URLs never change on their own. Only Share puts state in a link, and opening the link restores it.
+- [x] Spec template: one short "States and layout" section instead of a state checklist.
+
+## Phase 3: Two pilots
+
+Agents run them with the new skills only, with no hand fixing.
+
+- [x] Free trial conversion calculator (SaaS). Two Basic inputs opening on an example (500 started, 40 paid), an optional `Follow-up window and MRR` section, and a 10 × 10 grid of who paid. No published range in the result, because the sources disagree. Audit passed on round 4.
+- [x] KDP royalty calculator (KDP). Format and price, plus page count and ink for print. The result is a split bar of where the price goes and a royalty-by-price line with "Your price" marked. No comparison, because none measures the same thing. Audit passed on round 2.
+- [ ] User checks both real pages.
+- [x] Fix the docs and skills wherever an agent went wrong:
+  - A live tool's blank or invalid state shows `—` and keeps its layout. One bad Advanced value hides only its own part of the result.
+  - Error timing: errors show on blur. An error comparing two fields waits for the edited field. A shared link focuses its first invalid field.
+  - Accent: result visuals use the data colors, not the accent fill. `design-system.md` and `tool-interface.md` now agree.
+  - `—` is allowed as an empty-value mark in tools.
+  - Research for an older tool with no `research.md` creates one.
+  - A rework deletes older planning docs that the spec replaces.
+
+What the pilots showed: workers given only "we changed the docs and skills, rework this tool" took a clear position on users, cut inputs, and each picked a different visual that fits its tool. The weak spot was error and focus timing in live forms. Five of the seven audit defects were there, all hand-written per tool.
+
+- [ ] Build a shared live-form helper for error timing and shared-link focus, so each tool stops hand-writing it.
+- [ ] Delete the older KDP planning docs the new spec replaces: `brief.md` and `interface-contract.md`.
+
+## Phase 3b: Fix the docs, then rebuild both pilots from scratch
+
+The first pilots looked simple but lost too much. The free trial tool deleted cohorts, trial type, and billing options, and drew a narrow layout with large empty space. The KDP tool blanked its result when a long book's price fell below KDP's minimum, which looked like a 666-page cap. Live updates added most of the audit defects. The causes were in our docs: "pros use specialist tools", "leave it out", no shared layout, and no rule for blocked results.
+
+- [x] Remove live results. Every tool opens on realistic example values with their result, and one named button recalculates. A changed result steps back instead of disappearing.
+- [x] Advanced holds the depth. A rebuild never removes a working capability; it moves it into Advanced or the page content.
+- [x] Shared layout: `ToolWorkbench`, `ToolFieldRow`, and `ToolResult` in `app/ui/tools/tool-workbench.tsx`, with the 66rem working width most tools already used. Tools stop writing their own.
+- [x] Empty and blocked results: the result keeps its place, and a domain limit answers instead of blanking.
+- [x] Detail restored where the lean docs cut too far: layout and whitespace, inputs, repeated rows, default state, and more good and bad examples.
+- [x] Pilots deleted: tool code, content, engine, tests, and planning docs. Kept: route layouts, card art, database rows, and the shared KDP engine, restored to the original.
+- [x] Free trial conversion calculator rebuilt from scratch through the full pipeline. Basic is trial type, starts, and paid. Advanced holds the window, activation, pricing, a target, and up to 12 cohorts. The result has the rate, a unit grid, a likely range, and published ranges by trial type, hidden when the window doesn't match. Audit passed on round 2, with one coordinator call: with no window set, the ranges show with "paid within 6 months" in their labels.
+- [x] KDP royalty calculator rebuilt from scratch through the full pipeline. Basic is format, price, page count, and interior. Advanced holds trim, paper, Expanded Distribution, file size, royalty plan, and a goal. The result has a price split, a royalty-by-price line, and limits that answer, such as "Lowest price KDP allows". Audit passed on round 2.
+- [x] Fixed on the way, in shared code: print rounding now matches KDP's official calculator in ten cases, and eBook delivery half cents round correctly. This also corrects the minimum list price and price-profit tools, so they need a version bump at release.
+- [x] Doc lessons from this round: a comparison must match the source's window, and shows with the window in its label when the person hasn't set one. Tracking parameters are never a shared link.
+- [x] Sol review of the shared UI built in these rounds (workbench, unit grid, range marker, chart marks, metric hints). Passed on round 2 after five edge-case fixes.
+- [ ] User checks both real pages.
+- [x] Polish: the range legend is now a vertical list, and funnel labels sit beside the shape in plain text.
+
+## Phase 3c: Scannable results and required marks
+
+The rebuilt free trial result stretched a few numbers across the full width and squeezed the range legend into three columns, so every label wrapped. The docs caused it: "fill the working width", "never an empty half", and a fixed result order.
+
+- [x] Docs and skills: no fixed result layout. Design the result for scanning with a clear hierarchy: the main answer and its visual first, smaller numbers clean and readable. The working width is room, not a quota. A vertical list beats squeezed columns.
+- [x] Every required field shows `*`, Basic and Advanced partners alike.
+- [x] Free trial result redone by hand to these rules: the answer and its grid of 100 lead, where the rate sits follows the answer, and the numbers read as a list under the grid.
+- [x] KDP: `*` on its four Basic fields only.
+- [x] Shared: `UiMetricGroup layout="list"`, a vertical `UiRangeMarker` legend, and funnel labels beside the shape.
+- [x] Sol review of these shared changes before release. Passed on round 2, after fixes for funnel labels on phones, blank cohort rows, and long values in the list.
+
+## Phase 3d: Focused writers, friendly voice, and a slow pace
+
+Tool copy read like a template: 14 intros start with "This calculator" and 13 with "Enter a". One Opus session writing several tools carries one tool's phrasing into the next.
+
+- [x] One Opus session per tool for plan, interface, and writing. It never gets a second tool or integration work.
+- [x] Integration is its own session: route and content wiring, card art, publishing, and the full checks.
+- [x] The writing skill is short and asks the writer to think about the reader and talk like a friend. `writing-style.md` opens with the friendly, direct voice.
+- [x] Default pace: one tool at a time, with one or two agents running, unless the user asks for speed.
+
+## Phase 4: Triage all tools
+
+76 tools: 20 SaaS, 13 storage, 10 domain, 7 DNS, and 26 others.
+
+- [ ] Sol audit of each tool against the new checklist, with a short verdict.
+- [ ] Order by search traffic from analytics, busiest first.
+
+## Phase 5: Rollout in batches of about 5 tools
+
+Each batch: Luna user needs and comparison numbers, Opus plan, Sol engine changes if needed, Opus frontend and words, Sol audit, pull request, release.
+
+One integration session at a time, browser checks one at a time, and main synced before each batch.
+
+- [ ] SaaS
+- [ ] Storage
+- [ ] Domain
+- [ ] DNS
+- [ ] Other tools
diff --git a/lib/free-trial-conversion-calculator/engine.ts b/lib/free-trial-conversion-calculator/engine.ts
index 1bfa1fab..19116bcf 100644
--- a/lib/free-trial-conversion-calculator/engine.ts
+++ b/lib/free-trial-conversion-calculator/engine.ts
@@ -1,130 +1,169 @@
 import {
-  isSaasEconomicsCurrency, parseMoneyCents, parseOptionalLabel, parseWholeNumber,
-  SAAS_ECONOMICS_MAX_MONEY_CENTS, type SaasEconomicsCurrency,
+  type SaasEconomicsCurrency,
+  SAAS_ECONOMICS_MAX_MONEY_CENTS,
+  divideCeil,
+  isSaasEconomicsCurrency,
+  parseMoneyCents,
+  parseOptionalLabel,
+  parsePercentHundredths,
+  parseWholeNumber,
 } from "../saas-economics/shared.ts";
 import {
-  addExact, divideExact, exactFraction, isWholeAtScale, multiplyExact, roundExact,
   type ExactFraction,
+  addExact,
+  divideExact,
+  exactFraction,
+  isWholeAtScale,
+  multiplyExact,
+  roundExact,
 } from "../saas-economics/unit-economics.ts";
 
-export const TRIAL_MODELS = ["trialNoCard", "trialCardRequired", "freemium"] as const;
-export type TrialModel = (typeof TRIAL_MODELS)[number];
-export const TRIAL_MRR_METHODS = ["average", "split"] as const;
-export type TrialMrrMethod = (typeof TRIAL_MRR_METHODS)[number];
+export const TRIAL_TYPES = ["noCard", "cardUpfront", "freePlan"] as const;
+export type TrialType = (typeof TRIAL_TYPES)[number];
 export const TRIAL_MAX_COHORTS = 12;
 
-export type TrialCohortInput = { label: string; starts: string; paid: string; ageDays: string };
-export type TrialCohortField = keyof TrialCohortInput;
-export type FreeTrialConversionInput = {
-  model: string;
+export type TrialCohortRowInput = { id: string; name: string; starts: string; paid: string; ageDays: string };
+export type FreeTrialInput = {
+  trialType: string;
+  starts: string;
+  paid: string;
   windowDays: string;
-  cohorts: TrialCohortInput[];
-  includeMrr: boolean;
-  currency: string;          // ignored when includeMrr is false
-  mrrMethod: string;         // ignored when includeMrr is false
-  averageMonthly: string;    // used by "average"
-  monthlyCustomers: string;  // used by "split"
+  ageDays: string;
+  activated: string;
+  targetRate: string;
+  currency: string;
   monthlyPrice: string;
-  annualCustomers: string;
   annualPrice: string;
+  annualAccounts: string;
+  cohorts: TrialCohortRowInput[];
 };
 
-export type TrialFieldKey =
-  | "form" | "model" | "windowDays" | "cohorts"
-  | `cohorts.${number}.${TrialCohortField}`
-  | "currency" | "mrrMethod" | "averageMonthly"
-  | "monthlyCustomers" | "monthlyPrice" | "annualCustomers" | "annualPrice";
-
-export type TrialConversionRate =
-  | { kind: "finite"; hundredths: bigint; exact: ExactFraction; isRounded: boolean; roundedToZero: boolean }
-  | { kind: "notAvailable"; reason: "noStarts" };
-// hundredths = percent × 100. 1322n means 13.22%. exact is the percent as a fraction.
+export const FREE_TRIAL_EXAMPLE_INPUT: FreeTrialInput = {
+  trialType: "noCard", starts: "500", paid: "40", windowDays: "", ageDays: "",
+  activated: "", targetRate: "", currency: "USD", monthlyPrice: "", annualPrice: "",
+  annualAccounts: "", cohorts: [],
+};
 
+export type TrialFieldKey =
+  | "form" | "trialType" | "starts" | "paid"
+  | "windowDays" | "ageDays" | "activated" | "targetRate"
+  | "currency" | "monthlyPrice" | "annualPrice" | "annualAccounts"
+  | "cohorts" | `cohorts.${number}.${"name" | "starts" | "paid" | "ageDays"}`;
+export type TrialRate =
+  | { kind: "rate"; hundredths: bigint; exact: ExactFraction; isRounded: boolean; roundedToZero: boolean }
+  | { kind: "none" };
+export type TrialLikelyRange = { lowHundredths: bigint; highHundredths: bigint } | null;
 export type TrialMaturity =
   | { status: "complete" }
-  | { status: "maturing"; daysLeft: bigint };
-
+  | { status: "provisional"; daysLeft: bigint }
+  | { status: "unknown" };
 export type TrialCohortResult = {
-  index: number;             // position in the input
-  label: string;             // trimmed; "" when blank. The UI shows "Cohort 1" etc.
+  inputIndex: number | null;
+  name: string;
   starts: bigint;
   paid: bigint;
-  notPaid: bigint;           // starts - paid
-  ageDays: bigint;
-  rate: TrialConversionRate;
+  rate: TrialRate;
+  likely: TrialLikelyRange;
   maturity: TrialMaturity;
 };
-
-export type TrialCombined = {
-  basis: "complete" | "all";
-  status: "complete" | "provisional";
-  includedIndexes: number[]; // cohorts in the basis, in input order
-  excludedMaturing: number;  // maturing cohorts left out (0 when basis is "all")
-  starts: bigint;            // over the basis
+export type FreeTrialValues = {
+  trialType: TrialType;
+  starts: bigint;
   paid: bigint;
   notPaid: bigint;
-  rate: TrialConversionRate;
-};
-
-export type TrialNewMrr = {
-  currency: SaasEconomicsCurrency;
-  method: TrialMrrMethod;
-  paidCustomers: bigint;               // across all cohorts
-  averageMonthlyCents: bigint | null;  // "average" only
-  monthlyPlan: { customers: bigint; priceCents: bigint; mrrCents: bigint } | null; // "split" only, exact
-  annualPlan: { customers: bigint; annualPriceCents: bigint; mrrCents: bigint; isRounded: boolean } | null; // "split" only, ÷12 rounded
-  mrrCents: bigint;                    // rounded from the exact total
-  mrrIsRounded: boolean;
-  runRateArrCents: bigint;             // exact MRR × 12, rounded (always whole in practice)
-};
-
-export type FreeTrialConversionValues = {
-  model: TrialModel;
-  windowDays: bigint;
-  cohorts: TrialCohortResult[];
-  combined: TrialCombined;
-  newMrr: TrialNewMrr | null;
+  rate: TrialRate;
+  likely: TrialLikelyRange;
+  trialsPerPaidTenths: bigint | null;
+  windowDays: bigint | null;
+  maturity: TrialMaturity;
+  activation: { activated: bigint; activationRate: TrialRate; activatedToPaid: TrialRate } | null;
+  revenue: {
+    currency: SaasEconomicsCurrency;
+    monthlyAccounts: bigint;
+    annualAccounts: bigint;
+    mrrCents: bigint;
+    mrrIsRounded: boolean;
+    arrRunRateCents: bigint;
+  } | null;
+  target: {
+    hundredths: bigint;
+    paidAtTarget: bigint;
+    extraPaid: bigint;
+    extraMrrCents: bigint | null;
+  } | null;
+  cohorts: {
+    rows: TrialCohortResult[];
+    combined: {
+      basis: "settled" | "all";
+      status: "complete" | "provisional" | "unknown";
+      leftOut: number;
+      starts: bigint;
+      paid: bigint;
+      rate: TrialRate;
+    };
+  } | null;
 };
+export type FreeTrialErrors = Partial<Record<TrialFieldKey, string>>;
+export type FreeTrialCalculation =
+  | { status: "valid"; values: FreeTrialValues; errors: FreeTrialErrors }
+  | { status: "invalid"; values: null; errors: FreeTrialErrors };
 
-export type FreeTrialConversionErrors = Partial<Record<TrialFieldKey, string>>;
-
-export type FreeTrialConversionCalculation =
-  | { status: "valid"; values: FreeTrialConversionValues; errors: Record<string, never> }
-  | { status: "invalid"; values: null; errors: FreeTrialConversionErrors };
-
-const formError = "Something in the form is out of date. Reset and try again.";
-const optionError = "Choose one of the listed options.";
-const maximumCount = 10_000_000n;
+const FORM_ERROR = "Something in the form is out of date. Reset and try again.";
+const MAX_COUNT = 10_000_000n;
+const COHORT_FIELDS = ["name", "starts", "paid", "ageDays"] as const;
 
 function asRecord(value: unknown): Record<string, unknown> | null {
   return value !== null && typeof value === "object" && !Array.isArray(value)
     ? value as Record<string, unknown> : null;
 }
 
-function conversionRate(starts: bigint, paid: bigint): TrialConversionRate {
-  if (starts === 0n) return { kind: "notAvailable", reason: "noStarts" };
-  const exact = multiplyExact(divideExact(exactFraction(paid), exactFraction(starts)), exactFraction(100n));
+function isBlank(value: unknown): boolean {
+  return typeof value === "string" && value.trim() === "";
+}
+
+function blankRow(row: Record<string, unknown>): boolean {
+  return COHORT_FIELDS.every(field => isBlank(row[field]));
+}
+
+function rate(numerator: bigint, denominator: bigint): TrialRate {
+  if (denominator === 0n) return { kind: "none" };
+  // The exact fraction is in percent, before rounding to hundredths.
+  const exact = exactFraction(numerator * 100n, denominator);
   const hundredths = roundExact(exact, 100n);
   return {
-    kind: "finite", hundredths, exact, isRounded: !isWholeAtScale(exact, 100n),
-    roundedToZero: paid > 0n && hundredths === 0n,
+    kind: "rate", hundredths, exact, isRounded: !isWholeAtScale(exact, 100n),
+    roundedToZero: numerator > 0n && hundredths === 0n,
   };
 }
 
-export function calculateFreeTrialConversion(inputValue: unknown): FreeTrialConversionCalculation {
+function likely(starts: bigint, paid: bigint): TrialLikelyRange {
+  if (starts === 0n) return null;
+  const n = Number(starts);
+  const p = Number(paid) / n;
+  const zSquared = 1.96 ** 2;
+  const d = 1 + zSquared / n;
+  const c = p + zSquared / (2 * n);
+  const s = 1.96 * Math.sqrt(p * (1 - p) / n + zSquared / (4 * n * n));
+  return {
+    lowHundredths: BigInt(Math.floor(Math.max(0, (c - s) / d) * 10000)),
+    highHundredths: BigInt(Math.ceil(Math.min(1, (c + s) / d) * 10000)),
+  };
+}
+
+function maturity(window: bigint | null, age: bigint | null, hasError: boolean): TrialMaturity {
+  if (hasError || window === null || age === null) return { status: "unknown" };
+  return age >= window ? { status: "complete" } : { status: "provisional", daysLeft: window - age };
+}
+
+export function calculateFreeTrialConversion(inputValue: unknown): FreeTrialCalculation {
   const input = asRecord(inputValue);
-  const errors: FreeTrialConversionErrors = {};
-  if (!input) return { status: "invalid", values: null, errors: { form: formError } };
-  if (typeof input.includeMrr !== "boolean") errors.form = formError;
-  const model = input.model;
-  if (typeof model !== "string" || !TRIAL_MODELS.includes(model as TrialModel)) errors.model = optionError;
-
-  const parsedWindow = parseWholeNumber(input.windowDays, { min: 1n, max: 730n });
-  if (!parsedWindow.ok) errors.windowDays = parsedWindow.reason === "missing"
-    ? "Enter the follow-up window in days." : "Enter whole days from 1 to 730.";
-
-  function count(raw: unknown, key: TrialFieldKey): bigint | null {
-    const parsed = parseWholeNumber(raw, { min: 0n, max: maximumCount });
+  if (!input || !Array.isArray(input.cohorts)) {
+    return { status: "invalid", values: null, errors: { form: FORM_ERROR } };
+  }
+  const errors: FreeTrialErrors = {};
+  function count(raw: unknown, key: TrialFieldKey, optional = false): bigint | null {
+    if (optional && isBlank(raw)) return null;
+    const parsed = parseWholeNumber(raw, { min: 0n, max: MAX_COUNT });
     if (parsed.ok) return parsed.value;
     errors[key] = typeof raw === "string" && raw.trim().startsWith("-")
       ? "Counts can't be negative."
@@ -133,106 +172,187 @@ export function calculateFreeTrialConversion(inputValue: unknown): FreeTrialConv
       : "Use a whole number with no commas or decimals.";
     return null;
   }
-
+  function days(raw: unknown, key: TrialFieldKey, window = false): bigint | null {
+    if (isBlank(raw)) return null;
+    const parsed = parseWholeNumber(raw, { min: window ? 1n : 0n, max: window ? 730n : 3650n });
+    if (parsed.ok) return parsed.value;
+    errors[key] = window ? "Enter whole days from 1 to 730." : "Enter whole days from 0 to 3,650.";
+    return null;
+  }
   function money(raw: unknown, key: TrialFieldKey): bigint | null {
+    if (isBlank(raw)) return null;
     const parsed = parseMoneyCents(raw, { min: 0n, max: SAAS_ECONOMICS_MAX_MONEY_CENTS });
     if (parsed.ok) return parsed.value;
-    errors[key] = parsed.reason === "missing" ? "Enter an amount."
-      : parsed.reason === "range" ? "Enter an amount up to 1,000,000,000.00."
+    errors[key] = parsed.reason === "range" ? "Enter an amount up to 1,000,000,000.00."
       : "Use digits with up to two decimals. No signs, commas, or currency symbols.";
     return null;
   }
 
-  const cohorts: TrialCohortResult[] = [];
-  let paidCustomers = 0n;
-  let allCohortCountsParsed = true;
-  if (!Array.isArray(input.cohorts)) {
-    errors.form = formError;
-    allCohortCountsParsed = false;
-  } else {
-    if (input.cohorts.length === 0) errors.cohorts = "Add at least one cohort.";
-    if (input.cohorts.length > TRIAL_MAX_COHORTS) errors.cohorts = "Use up to 12 cohorts.";
-    for (let index = 0; index < input.cohorts.length; index += 1) {
-      const row = asRecord(input.cohorts[index]);
-      if (!row) {
-        errors.form = formError;
-        allCohortCountsParsed = false;
-        continue;
-      }
-      const label = parseOptionalLabel(row.label, 40);
-      if (!label.ok) errors[`cohorts.${index}.label`] = "Use a name up to 40 characters on one line.";
-      const starts = count(row.starts, `cohorts.${index}.starts`);
-      const paid = count(row.paid, `cohorts.${index}.paid`);
-      if (starts === null || paid === null) allCohortCountsParsed = false;
-      if (paid !== null) paidCustomers += paid;
-      if (starts !== null && paid !== null && paid > starts) {
-        errors[`cohorts.${index}.paid`] = "Paid can't be more than starts. Count only accounts from this cohort.";
-      }
-      const age = parseWholeNumber(row.ageDays, { min: 0n, max: 3650n });
-      if (!age.ok) errors[`cohorts.${index}.ageDays`] = age.reason === "missing"
-        ? "Enter the days since this cohort's last start." : "Enter whole days from 0 to 3,650.";
-      if (label.ok && starts !== null && paid !== null && paid <= starts && age.ok && parsedWindow.ok) {
-        cohorts.push({
-          index, label: label.value, starts, paid, notPaid: starts - paid, ageDays: age.value,
-          rate: conversionRate(starts, paid),
-          maturity: age.value >= parsedWindow.value ? { status: "complete" }
-            : { status: "maturing", daysLeft: parsedWindow.value - age.value },
-        });
-      }
+  const trialType = typeof input.trialType === "string" ? input.trialType.trim() : input.trialType;
+  if (!TRIAL_TYPES.includes(trialType as TrialType)) errors.trialType = "Choose one of the listed options.";
+  const starts = count(input.starts, "starts");
+  const paid = count(input.paid, "paid");
+  if (starts !== null && paid !== null && paid > starts) {
+    errors.paid = "Paid can't be more than trial starts. Count only accounts from this cohort.";
+  }
+
+  const windowDays = days(input.windowDays, "windowDays", true);
+  const ageDays = days(input.ageDays, "ageDays");
+  let hasAge = !isBlank(input.ageDays);
+  const activated = count(input.activated, "activated", true);
+  if (activated !== null) {
+    if (starts !== null && activated > starts) errors.activated = "Activated can't be more than trial starts.";
+    else if (paid !== null && activated < paid) {
+      errors.activated = `Activated must include everyone who paid, so it can't be less than ${paid}.`;
     }
   }
 
-  let newMrr: TrialNewMrr | null = null;
-  if (input.includeMrr === true) {
-    const currency = input.currency;
-    const method = input.mrrMethod;
-    if (!isSaasEconomicsCurrency(currency)) errors.currency = optionError;
-    if (typeof method !== "string" || !TRIAL_MRR_METHODS.includes(method as TrialMrrMethod)) errors.mrrMethod = optionError;
-    let averageMonthlyCents: bigint | null = null;
-    let monthlyPlan: TrialNewMrr["monthlyPlan"] = null;
-    let annualPlan: TrialNewMrr["annualPlan"] = null;
-    let exactMrr: ExactFraction | null = null;
-    if (method === "average") {
-      averageMonthlyCents = money(input.averageMonthly, "averageMonthly");
-      if (averageMonthlyCents !== null) exactMrr = multiplyExact(exactFraction(paidCustomers), exactFraction(averageMonthlyCents));
-    } else if (method === "split") {
-      const monthlyCustomers = count(input.monthlyCustomers, "monthlyCustomers");
-      const monthlyPrice = money(input.monthlyPrice, "monthlyPrice");
-      const annualCustomers = count(input.annualCustomers, "annualCustomers");
-      const annualPrice = money(input.annualPrice, "annualPrice");
-      if (allCohortCountsParsed && monthlyCustomers !== null && annualCustomers !== null
-        && monthlyCustomers + annualCustomers !== paidCustomers) {
-        const formattedPaid = paidCustomers.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
-        errors.monthlyCustomers = `Monthly and annual customers must add up to ${formattedPaid}, the paid customers above.`;
-      }
-      if (monthlyCustomers !== null && monthlyPrice !== null && annualCustomers !== null && annualPrice !== null) {
-        monthlyPlan = { customers: monthlyCustomers, priceCents: monthlyPrice, mrrCents: monthlyCustomers * monthlyPrice };
-        const annualMrr = divideExact(multiplyExact(exactFraction(annualCustomers), exactFraction(annualPrice)), exactFraction(12n));
-        annualPlan = { customers: annualCustomers, annualPriceCents: annualPrice, mrrCents: roundExact(annualMrr), isRounded: !isWholeAtScale(annualMrr, 1n) };
-        exactMrr = addExact(exactFraction(monthlyPlan.mrrCents), annualMrr);
-      }
+  let targetRate: bigint | null = null;
+  if (!isBlank(input.targetRate)) {
+    const parsed = parsePercentHundredths(input.targetRate, { min: 1n, max: 10000n });
+    if (parsed.ok) targetRate = parsed.value;
+    else errors.targetRate = "Enter a rate from 0.01 to 100%.";
+  }
+
+  const currency = isBlank(input.currency) ? "USD"
+    : typeof input.currency === "string" ? input.currency.trim() : input.currency;
+  if (!isSaasEconomicsCurrency(currency)) errors.currency = "Choose one of the listed options.";
+  const monthlyPrice = money(input.monthlyPrice, "monthlyPrice");
+  const annualPrice = money(input.annualPrice, "annualPrice");
+  const annualAccounts = count(input.annualAccounts, "annualAccounts", true);
+  const bothPricesSet = !isBlank(input.monthlyPrice) && !isBlank(input.annualPrice);
+  if (!errors.annualAccounts && !isBlank(input.annualAccounts) && !bothPricesSet) {
+    errors.annualAccounts = "Enter a monthly and an annual price to split paid accounts by plan.";
+  } else if (!errors.annualAccounts && bothPricesSet && isBlank(input.annualAccounts)) {
+    errors.annualAccounts = "Enter how many paid accounts are on annual plans.";
+  } else if (!errors.annualAccounts && annualAccounts !== null && paid !== null && annualAccounts > paid) {
+    errors.annualAccounts = `Annual accounts can't be more than ${paid}, the paid count.`;
+  }
+
+  const parsedRows: { index: number; name: string; starts: bigint; paid: bigint; age: bigint | null }[] = [];
+  if (input.cohorts.length > TRIAL_MAX_COHORTS) errors.cohorts = "Use up to 12 other cohorts.";
+  input.cohorts.forEach((raw: unknown, index: number) => {
+    const row = asRecord(raw);
+    if (!row) { errors.form = FORM_ERROR; return; }
+    if (blankRow(row)) return;
+    const name = parseOptionalLabel(row.name, 40);
+    if (!name.ok) errors[`cohorts.${index}.name`] = "Use a name up to 40 characters on one line.";
+    const rowStarts = count(row.starts, `cohorts.${index}.starts`);
+    const rowPaid = count(row.paid, `cohorts.${index}.paid`);
+    const age = days(row.ageDays, `cohorts.${index}.ageDays`);
+    hasAge ||= !isBlank(row.ageDays);
+    if (rowStarts !== null && rowPaid !== null && rowPaid > rowStarts) {
+      errors[`cohorts.${index}.paid`] = "Paid can't be more than starts in this cohort.";
     }
-    if (isSaasEconomicsCurrency(currency) && (method === "average" || method === "split") && exactMrr !== null) {
-      newMrr = {
-        currency, method, paidCustomers, averageMonthlyCents, monthlyPlan, annualPlan,
-        mrrCents: roundExact(exactMrr), mrrIsRounded: !isWholeAtScale(exactMrr, 1n),
-        runRateArrCents: roundExact(multiplyExact(exactMrr, exactFraction(12n))),
-      };
+    if (name.ok && rowStarts !== null && rowPaid !== null) {
+      parsedRows.push({ index, name: name.value || `Cohort ${index + 2}`, starts: rowStarts, paid: rowPaid, age });
     }
+  });
+  if (hasAge && isBlank(input.windowDays)) {
+    errors.windowDays = "Enter the follow-up window to compare cohort age against.";
+  }
+  if (errors.form || errors.trialType || errors.starts || errors.paid || starts === null || paid === null) {
+    return { status: "invalid", values: null, errors };
+  }
+
+  const maturityError = Boolean(errors.windowDays || errors.ageDays
+    || Object.keys(errors).some(key => /^cohorts\.\d+\.ageDays$/.test(key)));
+  const mainMaturity = maturity(windowDays, ageDays, maturityError);
+  const activation = activated === null || errors.activated ? null : {
+    activated, activationRate: rate(activated, starts), activatedToPaid: rate(paid, activated),
+  };
+
+  let revenue: FreeTrialValues["revenue"] = null;
+  let exactMrr: ExactFraction | null = null;
+  if (!errors.currency && !errors.monthlyPrice && !errors.annualPrice && !errors.annualAccounts
+    && isSaasEconomicsCurrency(currency) && (monthlyPrice !== null || annualPrice !== null)) {
+    const annual = monthlyPrice === null ? paid : annualPrice === null ? 0n : annualAccounts!;
+    const monthly = paid - annual;
+    exactMrr = addExact(exactFraction(monthly * (monthlyPrice ?? 0n)), exactFraction(annual * (annualPrice ?? 0n), 12n));
+    revenue = {
+      currency, monthlyAccounts: monthly, annualAccounts: annual,
+      mrrCents: roundExact(exactMrr), mrrIsRounded: !isWholeAtScale(exactMrr, 1n),
+      arrRunRateCents: roundExact(multiplyExact(exactMrr, exactFraction(12n))),
+    };
+  }
+
+  let target: FreeTrialValues["target"] = null;
+  if (targetRate !== null) {
+    const paidAtTarget = divideCeil(targetRate * starts, 10000n);
+    const extraPaid = paidAtTarget > paid ? paidAtTarget - paid : 0n;
+    const perPaid = exactMrr === null ? null : paid > 0n ? divideExact(exactMrr, exactFraction(paid))
+      : monthlyPrice !== null ? exactFraction(monthlyPrice) : exactFraction(annualPrice!, 12n);
+    target = {
+      hundredths: targetRate, paidAtTarget, extraPaid,
+      extraMrrCents: perPaid === null ? null : roundExact(multiplyExact(perPaid, exactFraction(extraPaid))),
+    };
   }
-  if (Object.keys(errors).length > 0 || !parsedWindow.ok) return { status: "invalid", values: null, errors };
-
-  const complete = cohorts.filter(row => row.maturity.status === "complete");
-  const useComplete = complete.reduce((sum, row) => sum + row.starts, 0n) > 0n;
-  const included = useComplete ? complete : cohorts;
-  const starts = included.reduce((sum, row) => sum + row.starts, 0n);
-  const paid = included.reduce((sum, row) => sum + row.paid, 0n);
-  const combined: TrialCombined = {
-    basis: useComplete ? "complete" : "all",
-    status: useComplete || cohorts.every(row => row.maturity.status === "complete") ? "complete" : "provisional",
-    includedIndexes: included.map(row => row.index),
-    excludedMaturing: useComplete ? cohorts.length - complete.length : 0,
-    starts, paid, notPaid: starts - paid, rate: conversionRate(starts, paid),
+
+  let cohorts: FreeTrialValues["cohorts"] = null;
+  if (parsedRows.length && !Object.keys(errors).some(key => key === "cohorts" || key.startsWith("cohorts."))) {
+    const rows: TrialCohortResult[] = [
+      { inputIndex: null, name: "This cohort", starts, paid, rate: rate(paid, starts), likely: likely(starts, paid), maturity: mainMaturity },
+      ...parsedRows.map(row => ({
+        inputIndex: row.index, name: row.name, starts: row.starts, paid: row.paid,
+        rate: rate(row.paid, row.starts), likely: likely(row.starts, row.paid),
+        maturity: maturity(windowDays, row.age, maturityError),
+      })),
+    ];
+    const settled = rows.filter(row => row.maturity.status !== "provisional");
+    const useSettled = settled.reduce((sum, row) => sum + row.starts, 0n) > 0n;
+    const basisRows = useSettled ? settled : rows;
+    const combinedStarts = basisRows.reduce((sum, row) => sum + row.starts, 0n);
+    const combinedPaid = basisRows.reduce((sum, row) => sum + row.paid, 0n);
+    cohorts = {
+      rows,
+      combined: {
+        basis: useSettled ? "settled" : "all",
+        status: basisRows.some(row => row.maturity.status === "provisional") ? "provisional"
+          : basisRows.every(row => row.maturity.status === "complete") ? "complete" : "unknown",
+        leftOut: useSettled ? rows.length - settled.length : 0,
+        starts: combinedStarts, paid: combinedPaid, rate: rate(combinedPaid, combinedStarts),
+      },
+    };
+  }
+  return {
+    status: "valid", errors,
+    values: {
+      trialType: trialType as TrialType, starts, paid, notPaid: starts - paid,
+      rate: rate(paid, starts), likely: likely(starts, paid),
+      trialsPerPaidTenths: paid === 0n ? null : roundExact(exactFraction(starts, paid), 10n),
+      windowDays, maturity: mainMaturity, activation, revenue, target, cohorts,
+    },
   };
-  return { status: "valid", errors: {}, values: { model: model as TrialModel, windowDays: parsedWindow.value, cohorts, combined, newMrr } };
+}
+
+const SHARE_FIELDS = {
+  type: "trialType", starts: "starts", paid: "paid", window: "windowDays", age: "ageDays",
+  activated: "activated", target: "targetRate", currency: "currency", monthly: "monthlyPrice",
+  annual: "annualPrice", annualPaid: "annualAccounts",
+} as const;
+
+export function freeTrialShareParams(input: FreeTrialInput): Record<string, string> {
+  const params: Record<string, string> = {};
+  for (const [key, field] of Object.entries(SHARE_FIELDS)) {
+    const value = input[field].trim();
+    if (value && (key !== "currency" || input.monthlyPrice.trim() || input.annualPrice.trim())) params[key] = value;
+  }
+  const rows = input.cohorts.filter(row => !blankRow(row));
+  if (rows.length) params.cohorts = rows.map(row => [
+    row.name.replace(/[~|]/g, "").trim(), row.starts.trim(), row.paid.trim(), row.ageDays.trim(),
+  ].join("~")).join("|");
+  return params;
+}
+
+export function freeTrialInputFromQuery(get: (key: string) => string): FreeTrialInput {
+  const input: FreeTrialInput = { ...FREE_TRIAL_EXAMPLE_INPUT, cohorts: [] };
+  for (const [key, field] of Object.entries(SHARE_FIELDS)) {
+    input[field] = get(key) || FREE_TRIAL_EXAMPLE_INPUT[field];
+  }
+  const rows = get("cohorts");
+  if (rows) input.cohorts = rows.split("|").slice(0, TRIAL_MAX_COHORTS).map((raw, index) => {
+    const [name = "", starts = "", paid = "", ageDays = ""] = raw.split("~");
+    return { id: `shared-${index}`, name, starts, paid, ageDays };
+  });
+  return input;
 }
diff --git a/lib/kdp/minimum-list-price.ts b/lib/kdp/minimum-list-price.ts
index 42a066fa..8cf4df7a 100644
--- a/lib/kdp/minimum-list-price.ts
+++ b/lib/kdp/minimum-list-price.ts
@@ -11,6 +11,7 @@ import {
   getKdpPrintFloorCents,
   getKdpPrintPricePoint,
   getKdpPrintingCostCents,
+  getKdpPrintingCostHundredthCents,
   type KdpEbookRoyaltyOption,
   type KdpRoyaltyFormat,
 } from "./royalty.ts";
@@ -225,11 +226,12 @@ function calculatePrint(input: KdpMinimumPriceInput, goalCents: number | null):
   const printCost = getKdpPrintCost(format, input.trimId, effectivePageCount, interior, paper);
   if (!printCost) return unavailable("A US KDP print cost rule is missing for this setup. Check the KDP rules and try again.");
   const printingCostCents = getKdpPrintingCostCents(printCost, effectivePageCount);
+  const costHundredthCents = getKdpPrintingCostHundredthCents(printCost, effectivePageCount);
   if (!Number.isSafeInteger(printingCostCents) || printingCostCents < 0) {
     return unavailable("A US KDP print cost rule could not be calculated. Check the KDP rules and try again.");
   }
 
-  const minimumPriceCents = getKdpPrintFloorCents(printingCostCents);
+  const minimumPriceCents = getKdpPrintFloorCents(printingCostCents, costHundredthCents);
   if (!Number.isSafeInteger(minimumPriceCents) || minimumPriceCents > KDP_PRINT_MAX_PRICE_CENTS) {
     return unavailable("This print setup's modeled minimum exceeds KDP's $250.00 maximum. Change the print setup.");
   }
@@ -238,13 +240,13 @@ function calculatePrint(input: KdpMinimumPriceInput, goalCents: number | null):
   if (goalCents !== null) {
     priceCents = 0;
     for (let candidate = minimumPriceCents; candidate <= KDP_PRINT_MAX_PRICE_CENTS; candidate += 1) {
-      if (getKdpPrintPricePoint(candidate, printingCostCents).royaltyCents >= goalCents) {
+      if (getKdpPrintPricePoint(candidate, printingCostCents, costHundredthCents).royaltyCents >= goalCents) {
         priceCents = candidate;
         break;
       }
     }
     if (priceCents === 0) {
-      const highest = getKdpPrintPricePoint(KDP_PRINT_MAX_PRICE_CENTS, printingCostCents);
+      const highest = getKdpPrintPricePoint(KDP_PRINT_MAX_PRICE_CENTS, printingCostCents, costHundredthCents);
       return {
         status: "unreachable",
         values: {
@@ -255,7 +257,7 @@ function calculatePrint(input: KdpMinimumPriceInput, goalCents: number | null):
     }
   }
 
-  const point = getKdpPrintPricePoint(priceCents, printingCostCents);
+  const point = getKdpPrintPricePoint(priceCents, printingCostCents, costHundredthCents);
   return {
     status: "available",
     values: {
diff --git a/lib/kdp/price-profit.ts b/lib/kdp/price-profit.ts
index c923b14a..35bdb513 100644
--- a/lib/kdp/price-profit.ts
+++ b/lib/kdp/price-profit.ts
@@ -5,6 +5,7 @@ import {
   getKdpPrintFloorCents,
   getKdpPrintPricePoint,
   getKdpPrintingCostCents,
+  getKdpPrintingCostHundredthCents,
 } from "./royalty.ts";
 import {
   KDP_SOURCES,
@@ -305,10 +306,11 @@ export function calculateKdpPriceProfit(input: KdpPriceProfitInput): KdpPricePro
       return unavailable("A KDP printing cost rule is missing for one of these options. Check the current KDP tables and try again.");
     }
     const printingCostCents = getKdpPrintingCostCents(printCost, option.effectivePageCount);
+    const costHundredthCents = getKdpPrintingCostHundredthCents(printCost, option.effectivePageCount);
     if (!Number.isSafeInteger(printingCostCents) || printingCostCents < 0) {
       return unavailable("A print cost could not be calculated from the current KDP rules. Reload and try again.");
     }
-    const minimumPriceCents = getKdpPrintFloorCents(printingCostCents);
+    const minimumPriceCents = getKdpPrintFloorCents(printingCostCents, costHundredthCents);
     if (!Number.isSafeInteger(minimumPriceCents) || minimumPriceCents < 1) {
       return unavailable("A KDP minimum price could not be calculated for one of these options. Reload and try again.");
     }
@@ -317,7 +319,7 @@ export function calculateKdpPriceProfit(input: KdpPriceProfitInput): KdpPricePro
     }
 
     const eligible = priceCents >= minimumPriceCents;
-    const point = eligible ? getKdpPrintPricePoint(priceCents, printingCostCents) : null;
+    const point = eligible ? getKdpPrintPricePoint(priceCents, printingCostCents, costHundredthCents) : null;
     const profitCents = input.includeCosts && eligible
       ? (plannedCopies as number) * ((point as NonNullable<typeof point>).royaltyCents - (option.otherCostPerSaleCents as number)) - (option.oneTimeCostCents as number)
       : null;
diff --git a/lib/kdp/royalty-calculator.ts b/lib/kdp/royalty-calculator.ts
new file mode 100644
index 00000000..973dc3e3
--- /dev/null
+++ b/lib/kdp/royalty-calculator.ts
@@ -0,0 +1,310 @@
+import {
+  KDP_EBOOK_MAX_PRICE_CENTS,
+  KDP_EBOOK_SEVENTY_MAX_CENTS,
+  KDP_EBOOK_SEVENTY_MIN_CENTS,
+  KDP_PRINT_MAX_PRICE_CENTS,
+  KDP_ROYALTY_RATES,
+  KDP_ROYALTY_VERSION,
+  getKdpEbookDeliveryCents,
+  getKdpEbookFloorCents,
+  getKdpEbookPricePoint,
+  getKdpPrintCost,
+  getKdpPrintFloorCents,
+  getKdpPrintPricePoint,
+  getKdpPrintRoyaltyCents,
+  getKdpPrintingCostCents,
+  getKdpPrintingCostHundredthCents,
+} from "./royalty.ts";
+import {
+  KDP_MAX_FILE_MB,
+  getKdpInteriorOptions,
+  getKdpPageLimit,
+  getKdpPaperOptions,
+  getKdpTrimOptions,
+  type KdpInterior,
+  type KdpPaper,
+} from "./specs.ts";
+
+export type KdpRoyaltyCalculatorField =
+  | "format" | "listPrice" | "pageCount" | "interior" | "trimId" | "paper"
+  | "channel" | "fileSize" | "plan" | "monthlyGoal";
+
+export type KdpRoyaltyCalculatorInput = Readonly<{
+  format: string;
+  listPriceText: string;
+  pageCountText: string;
+  interior: string;
+  trimId: string;        // "" → "6x9"
+  paper: string;         // "" → "white"
+  channel: string;       // "" → "amazon"; paperback only
+  fileSizeText: string;  // "" → 2 MB
+  plan: string;          // "" → "70"
+  monthlyGoalText: string; // "" → not used
+}>;
+
+export type KdpRoyaltyCalculatorResult =
+  | Readonly<{ status: "invalid"; fieldErrors: Partial<Record<KdpRoyaltyCalculatorField, string>> }>
+  | Readonly<{ status: "calculated"; values: KdpRoyaltyCalculatorValues; fieldErrors: Partial<Record<"monthlyGoal", string>> }>;
+
+export type KdpRoyaltyCalculatorValues = Readonly<{
+  format: "paperback" | "hardcover" | "ebook";
+  channel: "amazon" | "expanded" | null;      // null for eBook
+  plan: 35 | 70 | null;                       // selected plan; null for print
+  enteredPriceCents: number;
+  priceCents: number;                         // the answered price, after any limit
+  limit: null | Readonly<{ kind: "below-minimum" | "below-break-even" | "above-maximum"; priceCents: number }>;
+  rate: 35 | 40 | 50 | 60 | 70;               // applied rate
+  seventyOutsideBand: null | "below" | "above"; // plan 70 but price outside $2.99–$12.99
+  deliveryExceedsShare: boolean;
+  royaltyCents: number;                       // never negative
+  split: Readonly<{ royaltyCents: number; costCents: number; amazonCents: number }>;
+  costKind: "printing" | "delivery" | null;
+  printing: null | Readonly<{ enteredPages: number; printedPages: number; costCents: number; fixedCents: number; pageCents: number }>;
+  delivery: null | Readonly<{ fileSizeMB: number; defaultSize: boolean; costCents: number }>; // costCents even when 35% applies
+  minimumPriceCents: number;                  // lowest price for the selected channel or plan
+  minimumKind: "kdp" | "break-even";          // "break-even" only for Expanded Distribution
+  maximumPriceCents: number;
+  shareBasisPoints: number;
+  comparison: null | Readonly<{
+    kind: "rate-step" | "other-channel" | "other-plan" | "seventy-band";
+    priceCents: number;
+    rate: number;
+    royaltyCents: number;
+  }>;
+  goal: null | Readonly<{ goalCents: number; copies: number | null }>; // null when no goal or the goal is invalid
+  curve: Readonly<{
+    series: readonly Readonly<{ id: "amazon" | "expanded" | "plan70" | "plan35"; points: readonly (readonly [priceCents: number, royaltyCents: number])[] }>[];
+    mark: Readonly<{ priceCents: number; royaltyCents: number }>;
+  }>;
+  rulesVersion: string;                       // KDP_ROYALTY_VERSION
+}>;
+
+type FieldErrors = Partial<Record<KdpRoyaltyCalculatorField, string>>;
+type Values = KdpRoyaltyCalculatorValues;
+type CurveSeries = Values["curve"]["series"][number];
+
+function parseMoneyCents(text: string): number | null {
+  const match = /^\$?(\d+)(?:\.(\d{1,2}))?$/.exec(text.trim());
+  if (!match) return null;
+  const cents = Number(match[1]) * 100 + Number((match[2] ?? "").padEnd(2, "0"));
+  return Number.isSafeInteger(cents) && cents > 0 ? cents : null;
+}
+
+function answerPrice(
+  entered: number,
+  minimum: number,
+  maximum: number,
+  minimumKind: Values["minimumKind"],
+): Pick<Values, "priceCents" | "limit"> {
+  if (entered < minimum) {
+    return {
+      priceCents: minimum,
+      limit: { kind: minimumKind === "break-even" ? "below-break-even" : "below-minimum", priceCents: minimum },
+    };
+  }
+  if (entered > maximum) return { priceCents: maximum, limit: { kind: "above-maximum", priceCents: maximum } };
+  return { priceCents: entered, limit: null };
+}
+
+function curveFor(
+  priceCents: number,
+  royaltyCents: number,
+  maximum: number,
+  ebook: boolean,
+  definitions: readonly Readonly<{
+    id: CurveSeries["id"];
+    minimum: number;
+    maximum: number;
+    royaltyAt: (price: number) => number;
+  }>[],
+): Values["curve"] {
+  const lower = Math.min(...definitions.map((series) => series.minimum));
+  const upper = Math.min(maximum, Math.max(
+    Math.ceil((priceCents * 1.5 - 99) / 100) * 100 + 99,
+    ebook ? 1_599 : 1_499,
+  ));
+  const boundaries = ebook
+    ? [KDP_EBOOK_SEVENTY_MIN_CENTS - 1, KDP_EBOOK_SEVENTY_MIN_CENTS, KDP_EBOOK_SEVENTY_MAX_CENTS, KDP_EBOOK_SEVENTY_MAX_CENTS + 1]
+    : [KDP_ROYALTY_RATES.printThresholdCents - 1, KDP_ROYALTY_RATES.printThresholdCents];
+  const prices = [...new Set([
+    ...Array.from({ length: 48 }, (_, index) => Math.round(lower + (upper - lower) * index / 47)),
+    lower, upper, priceCents, ...boundaries, ...definitions.map((series) => series.minimum),
+  ].filter((price) => price >= lower && price <= upper))].sort((a, b) => a - b);
+  return {
+    series: definitions.map((series) => ({
+      id: series.id,
+      points: prices.filter((price) => price >= series.minimum && price <= series.maximum)
+        .map((price) => [price, Math.max(0, series.royaltyAt(price))] as const),
+    })),
+    mark: { priceCents, royaltyCents },
+  };
+}
+
+function goalFor(goalCents: number | null, royaltyCents: number): Values["goal"] {
+  return goalCents === null ? null : { goalCents, copies: royaltyCents > 0 ? Math.ceil(goalCents / royaltyCents) : null };
+}
+
+function calculateEbook(
+  input: KdpRoyaltyCalculatorInput,
+  enteredPriceCents: number,
+  goalCents: number | null,
+  fieldErrors: FieldErrors,
+): KdpRoyaltyCalculatorResult {
+  const sizeText = input.fileSizeText.trim();
+  const fileSizeMB = sizeText === "" ? 2 : /^\d+(?:\.\d+)?$/.test(sizeText) ? Number(sizeText) : Number.NaN;
+  if (!Number.isFinite(fileSizeMB) || fileSizeMB <= 0 || fileSizeMB > KDP_MAX_FILE_MB) {
+    fieldErrors.fileSize = "Enter a file size above 0 and at most 650 MB.";
+  }
+  const planText = input.plan || "70";
+  if (planText !== "35" && planText !== "70") fieldErrors.plan = "Choose the 35% or 70% plan.";
+  if (fieldErrors.fileSize || fieldErrors.plan) return { status: "invalid", fieldErrors };
+
+  const plan = planText === "35" ? 35 : 70;
+  const minimumPriceCents = getKdpEbookFloorCents(fileSizeMB);
+  const answered = answerPrice(enteredPriceCents, minimumPriceCents, KDP_EBOOK_MAX_PRICE_CENTS, "kdp");
+  const { priceCents } = answered;
+  const point = getKdpEbookPricePoint(priceCents, plan, fileSizeMB);
+  const rate = point.royaltyRate === 70 ? 70 : 35;
+  const royaltyCents = Math.max(0, point.royaltyCents);
+  const deliveryExceedsShare = rate === 70 && point.royaltyCents <= 0;
+  const deliveryCents = getKdpEbookDeliveryCents(fileSizeMB);
+  const costCents = rate === 70 ? Math.min(deliveryCents, priceCents) : 0;
+  const inBand = priceCents >= KDP_EBOOK_SEVENTY_MIN_CENTS && priceCents <= KDP_EBOOK_SEVENTY_MAX_CENTS;
+  const bandSide = priceCents < KDP_EBOOK_SEVENTY_MIN_CENTS ? "below" : "above";
+  let comparison: Values["comparison"] = null;
+  if (inBand) {
+    const otherRate = rate === 70 ? 35 : 70;
+    comparison = {
+      kind: "other-plan", priceCents, rate: otherRate,
+      royaltyCents: Math.max(0, getKdpEbookPricePoint(priceCents, otherRate, fileSizeMB).royaltyCents),
+    };
+  } else {
+    const edge = bandSide === "below" ? KDP_EBOOK_SEVENTY_MIN_CENTS : KDP_EBOOK_SEVENTY_MAX_CENTS;
+    if (edge >= minimumPriceCents) comparison = {
+      kind: "seventy-band", priceCents: edge, rate: 70,
+      royaltyCents: Math.max(0, getKdpEbookPricePoint(edge, 70, fileSizeMB).royaltyCents),
+    };
+  }
+  const plan70 = {
+    id: "plan70" as const,
+    minimum: Math.max(minimumPriceCents, KDP_EBOOK_SEVENTY_MIN_CENTS),
+    maximum: KDP_EBOOK_SEVENTY_MAX_CENTS,
+    royaltyAt: (price: number) => getKdpEbookPricePoint(price, 70, fileSizeMB).royaltyCents,
+  };
+  const plan35 = {
+    id: "plan35" as const, minimum: minimumPriceCents, maximum: KDP_EBOOK_MAX_PRICE_CENTS,
+    royaltyAt: (price: number) => getKdpEbookPricePoint(price, 35, fileSizeMB).royaltyCents,
+  };
+  return {
+    status: "calculated",
+    fieldErrors: fieldErrors.monthlyGoal ? { monthlyGoal: fieldErrors.monthlyGoal } : {},
+    values: {
+      format: "ebook", channel: null, plan, enteredPriceCents, ...answered, rate,
+      seventyOutsideBand: plan === 70 && !inBand ? bandSide : null,
+      deliveryExceedsShare, royaltyCents,
+      split: { royaltyCents, costCents, amazonCents: priceCents - royaltyCents - costCents },
+      costKind: rate === 70 ? "delivery" : null,
+      printing: null, delivery: { fileSizeMB, defaultSize: sizeText === "", costCents: deliveryCents },
+      minimumPriceCents, minimumKind: "kdp", maximumPriceCents: KDP_EBOOK_MAX_PRICE_CENTS,
+      shareBasisPoints: Math.round(royaltyCents * 10_000 / priceCents), comparison,
+      goal: goalFor(goalCents, royaltyCents),
+      curve: curveFor(priceCents, royaltyCents, KDP_EBOOK_MAX_PRICE_CENTS, true, plan === 70 ? [plan70, plan35] : [plan35, plan70]),
+      rulesVersion: KDP_ROYALTY_VERSION,
+    },
+  };
+}
+
+export function calculateKdpRoyaltyEstimate(input: KdpRoyaltyCalculatorInput): KdpRoyaltyCalculatorResult {
+  const fieldErrors: FieldErrors = {};
+  const format = input.format;
+  if (format !== "paperback" && format !== "hardcover" && format !== "ebook") {
+    fieldErrors.format = "Choose paperback, hardcover, or Kindle eBook.";
+  }
+  const enteredPriceCents = parseMoneyCents(input.listPriceText);
+  if (enteredPriceCents === null) fieldErrors.listPrice = "Enter a price above $0 with at most two decimal places.";
+  const goalText = input.monthlyGoalText.trim();
+  let goalCents = goalText === "" ? null : parseMoneyCents(goalText);
+  if (goalText !== "" && (goalCents === null || goalCents > 1_000_000_000)) {
+    fieldErrors.monthlyGoal = "Enter a goal above $0 and at most $10,000,000.";
+    goalCents = null;
+  }
+  if (fieldErrors.format || enteredPriceCents === null) return { status: "invalid", fieldErrors };
+  if (format === "ebook") return calculateEbook(input, enteredPriceCents, goalCents, fieldErrors);
+  if (format !== "paperback" && format !== "hardcover") return { status: "invalid", fieldErrors };
+
+  const pageText = input.pageCountText.trim();
+  const enteredPages = /^\d+$/.test(pageText) ? Number(pageText) : Number.NaN;
+  const validPages = Number.isSafeInteger(enteredPages) && enteredPages > 0;
+  if (!validPages) fieldErrors.pageCount = "Enter a whole page count above 0.";
+  const printedPages = enteredPages + enteredPages % 2;
+  const trimId = input.trimId || "6x9";
+  const paper = (input.paper || "white") as KdpPaper;
+  const interior = input.interior as KdpInterior;
+  if (!getKdpTrimOptions(format).some((trim) => trim.id === trimId)) {
+    fieldErrors.trimId = "Choose a trim size KDP offers for this binding.";
+  }
+  if (!getKdpInteriorOptions(format).includes(interior)) {
+    fieldErrors.interior = "Choose an interior KDP offers for this binding.";
+  } else if (!getKdpPaperOptions(format, interior).includes(paper)) {
+    fieldErrors.paper = "Choose a paper KDP offers for this interior and binding.";
+  }
+  const channel = format === "hardcover" ? "amazon" : input.channel || "amazon";
+  if (channel !== "amazon" && channel !== "expanded") fieldErrors.channel = "Choose Amazon.com or Expanded Distribution.";
+  if (!fieldErrors.trimId && !fieldErrors.interior && !fieldErrors.paper) {
+    const pageLimit = getKdpPageLimit(trimId, format, interior, paper);
+    if (!pageLimit) fieldErrors.interior = "KDP doesn't offer this interior at this trim size.";
+    else if (validPages && (printedPages < pageLimit.min || printedPages > pageLimit.max)) {
+      fieldErrors.pageCount = `KDP prints ${pageLimit.min} to ${pageLimit.max} pages for this setup.`;
+    }
+  }
+  if (Object.keys(fieldErrors).some((field) => field !== "monthlyGoal")) return { status: "invalid", fieldErrors };
+
+  // The validated trim has a printing cost in the shared US table.
+  const printCost = getKdpPrintCost(format, trimId, printedPages, interior, paper)!;
+  const printingCents = getKdpPrintingCostCents(printCost, printedPages);
+  const costHundredthCents = getKdpPrintingCostHundredthCents(printCost, printedPages);
+  const amazonMinimum = getKdpPrintFloorCents(printingCents, costHundredthCents);
+  const expandedMinimum = Math.ceil(costHundredthCents / 40);
+  const minimumPriceCents = channel === "expanded" ? expandedMinimum : amazonMinimum;
+  const minimumKind = channel === "expanded" ? "break-even" : "kdp";
+  const answered = answerPrice(enteredPriceCents, minimumPriceCents, KDP_PRINT_MAX_PRICE_CENTS, minimumKind);
+  const { priceCents } = answered;
+  const amazonAt = (price: number) => getKdpPrintPricePoint(price, printingCents, costHundredthCents);
+  const expandedAt = (price: number) => getKdpPrintRoyaltyCents(price, 40, costHundredthCents);
+  const rate = channel === "expanded" ? 40 : priceCents >= KDP_ROYALTY_RATES.printThresholdCents ? 60 : 50;
+  const royaltyCents = Math.max(0, channel === "expanded" ? expandedAt(priceCents) : amazonAt(priceCents).royaltyCents);
+  let comparison: Values["comparison"] = null;
+  if (channel === "amazon" && priceCents < KDP_ROYALTY_RATES.printThresholdCents) {
+    comparison = {
+      kind: "rate-step", priceCents: KDP_ROYALTY_RATES.printThresholdCents, rate: 60,
+      royaltyCents: Math.max(0, amazonAt(KDP_ROYALTY_RATES.printThresholdCents).royaltyCents),
+    };
+  } else if (channel === "expanded") comparison = {
+    kind: "other-channel", priceCents, rate: amazonAt(priceCents).royaltyRate,
+    royaltyCents: Math.max(0, amazonAt(priceCents).royaltyCents),
+  };
+  const amazonSeries = {
+    id: "amazon" as const, minimum: amazonMinimum, maximum: KDP_PRINT_MAX_PRICE_CENTS,
+    royaltyAt: (price: number) => amazonAt(price).royaltyCents,
+  };
+  return {
+    status: "calculated",
+    fieldErrors: fieldErrors.monthlyGoal ? { monthlyGoal: fieldErrors.monthlyGoal } : {},
+    values: {
+      format, channel: channel === "expanded" ? "expanded" : "amazon", plan: null,
+      enteredPriceCents, ...answered, rate, seventyOutsideBand: null, deliveryExceedsShare: false,
+      royaltyCents, split: { royaltyCents, costCents: printingCents, amazonCents: priceCents - royaltyCents - printingCents },
+      costKind: "printing",
+      printing: { enteredPages, printedPages, costCents: printingCents, fixedCents: printCost.fixedCents, pageCents: printingCents - printCost.fixedCents },
+      delivery: null, minimumPriceCents, minimumKind, maximumPriceCents: KDP_PRINT_MAX_PRICE_CENTS,
+      shareBasisPoints: Math.round(royaltyCents * 10_000 / priceCents), comparison,
+      goal: goalFor(goalCents, royaltyCents),
+      curve: curveFor(priceCents, royaltyCents, KDP_PRINT_MAX_PRICE_CENTS, false, channel === "expanded" ? [
+        { id: "expanded", minimum: expandedMinimum, maximum: KDP_PRINT_MAX_PRICE_CENTS, royaltyAt: expandedAt },
+        amazonSeries,
+      ] : [amazonSeries]),
+      rulesVersion: KDP_ROYALTY_VERSION,
+    },
+  };
+}
+
diff --git a/lib/kdp/royalty.ts b/lib/kdp/royalty.ts
index 73076467..09dc5867 100644
--- a/lib/kdp/royalty.ts
+++ b/lib/kdp/royalty.ts
@@ -1,7 +1,5 @@
 import {
-  KDP_SOURCES,
   findKdpTrim,
-  getKdpPageLimit,
   round,
   type KdpBinding,
   type KdpInterior,
@@ -11,25 +9,6 @@ import {
 export type KdpRoyaltyFormat = KdpBinding | "ebook";
 export type KdpEbookRoyaltyOption = 35 | 70;
 
-export type KdpRoyaltyInput = Readonly<{
-  format: KdpRoyaltyFormat;
-  trimId?: string;
-  pageCount?: number;
-  interior?: KdpInterior;
-  paper?: KdpPaper;
-  listPrice: number;
-  ebookFileSizeMB?: number;
-  ebookRoyaltyOption?: KdpEbookRoyaltyOption;
-  monthlyTarget?: number;
-}>;
-
-export type KdpRoyaltyIssue = Readonly<{
-  code: string;
-  field?: string;
-  severity: "warning" | "error";
-  message: string;
-}>;
-
 export type KdpPricePoint = Readonly<{
   listPriceCents: number;
   royaltyCents: number;
@@ -39,36 +18,6 @@ export type KdpPricePoint = Readonly<{
   marginBasisPoints: number;
 }>;
 
-export type KdpRoyaltyValues = Readonly<{
-  format: KdpRoyaltyFormat;
-  listPriceCents: number;
-  effectivePageCount: number | null;
-  minimumListPriceCents: number;
-  printingCostCents: number | null;
-  fixedCostCents: number | null;
-  pageCostCents: number | null;
-  deliveryCostCents: number | null;
-  royaltyRate: number;
-  effectiveRoyaltyRate: number;
-  royaltyCents: number;
-  royaltyMarginBasisPoints: number;
-  breakEvenAdSpendCents: number;
-  breakEvenAcosBasisPoints: number | null;
-  copiesForMonthlyTarget: number | null;
-  monthlyTargetStatus: "omitted" | "calculated" | "unavailable";
-  monthlyTargetCents: number | null;
-  pricePoints: readonly KdpPricePoint[];
-  ebookFileSizeMB: number | null;
-  ebookDeliveryRateCentsPerMB: number | null;
-  sources: readonly string[];
-}>;
-
-export type KdpRoyaltyResult = Readonly<{
-  status: "valid" | "invalid";
-  values: KdpRoyaltyValues | null;
-  issues: readonly KdpRoyaltyIssue[];
-}>;
-
 export type KdpPrintCost = Readonly<{ fixedCents: number; perPageDollars: number }>;
 
 /** KDP royalty rates, shared with the platform fee reference so both stay in step. */
@@ -91,16 +40,6 @@ export const KDP_EBOOK_MAX_PRICE_CENTS = EBOOK_MAX_PRICE_CENTS;
 export const KDP_EBOOK_SEVENTY_MIN_CENTS = EBOOK_SEVENTY_MIN_CENTS;
 export const KDP_EBOOK_SEVENTY_MAX_CENTS = EBOOK_SEVENTY_MAX_CENTS;
 
-function issue(code: string, message: string, severity: KdpRoyaltyIssue["severity"] = "error", field?: string): KdpRoyaltyIssue {
-  return { code, field, severity, message };
-}
-
-function dollarsToCents(value: number): number | null {
-  if (!Number.isFinite(value)) return null;
-  const cents = Math.round(value * 100);
-  return cents >= 1 ? cents : null;
-}
-
 export function parseKdpRoyaltyMoney(raw: string): number {
   const value = raw.trim();
   return /^\$?\d+(?:\.\d{1,2})?$/.test(value) ? Number(value.replace(/^\$/, "")) : Number.NaN;
@@ -129,13 +68,13 @@ function printCost(format: KdpBinding, trimId: string, pageCount: number, interi
 }
 
 function printingCostCents(cost: KdpPrintCost, pageCount: number): number {
-  return cost.fixedCents + Math.round(cost.perPageDollars * 100 * pageCount);
+  return Math.floor((getKdpPrintingCostHundredthCents(cost, pageCount) + 50) / 100);
 }
 
-function minimumPrintPriceCents(costCents: number): number {
-  const fiftyPercentPrice = Math.ceil(costCents * 100 / KDP_ROYALTY_RATES.printBelowThreshold);
+function minimumPrintPriceCents(costHundredthCents: number): number {
+  const fiftyPercentPrice = Math.round(costHundredthCents / KDP_ROYALTY_RATES.printBelowThreshold);
   if (fiftyPercentPrice <= PRINT_ROYALTY_THRESHOLD_CENTS - 1) return fiftyPercentPrice;
-  return Math.max(PRINT_ROYALTY_THRESHOLD_CENTS, Math.ceil(costCents * 100 / KDP_ROYALTY_RATES.printAtOrAboveThreshold));
+  return Math.max(PRINT_ROYALTY_THRESHOLD_CENTS, Math.round(costHundredthCents / KDP_ROYALTY_RATES.printAtOrAboveThreshold));
 }
 
 function ebookMinimumPriceCents(fileSizeMB: number): number {
@@ -146,7 +85,8 @@ function ebookMinimumPriceCents(fileSizeMB: number): number {
 
 function ebookDeliveryCostCents(fileSizeMB: number): number {
   const roundedKilobytes = Math.ceil(fileSizeMB * 1024);
-  return Math.max(1, Math.round((roundedKilobytes * 0.15 / 1024) * 100));
+  // 15 cents per 1,024 KB. Add half the denominator before integer division.
+  return Math.max(1, Math.floor((roundedKilobytes * 15 + 512) / 1024));
 }
 
 /** Shared print rules used by the forward and inverse calculators. */
@@ -158,8 +98,14 @@ export function getKdpPrintingCostCents(cost: KdpPrintCost, pageCount: number):
   return printingCostCents(cost, pageCount);
 }
 
-export function getKdpPrintFloorCents(costCents: number): number {
-  return minimumPrintPriceCents(costCents);
+/** Preserve the US table's four decimal places through the print calculations. */
+export function getKdpPrintingCostHundredthCents(cost: KdpPrintCost, pageCount: number): number {
+  return cost.fixedCents * 100 + Math.round(cost.perPageDollars * 10_000) * pageCount;
+}
+
+/** Pass the exact table cost separately from its rounded display value. */
+export function getKdpPrintFloorCents(costCents: number, costHundredthCents = costCents * 100): number {
+  return minimumPrintPriceCents(costHundredthCents);
 }
 
 export function getKdpEbookFloorCents(fileSizeMB: number): number {
@@ -170,9 +116,13 @@ export function getKdpEbookDeliveryCents(fileSizeMB: number): number {
   return ebookDeliveryCostCents(fileSizeMB);
 }
 
-export function getKdpPrintPricePoint(priceCents: number, printingCents: number): KdpPricePoint {
+export function getKdpPrintRoyaltyCents(priceCents: number, royaltyRate: number, costHundredthCents: number): number {
+  return Math.floor((priceCents * royaltyRate - costHundredthCents + 50) / 100);
+}
+
+export function getKdpPrintPricePoint(priceCents: number, printingCents: number, costHundredthCents = printingCents * 100): KdpPricePoint {
   const royaltyRate = priceCents >= PRINT_ROYALTY_THRESHOLD_CENTS ? KDP_ROYALTY_RATES.printAtOrAboveThreshold : KDP_ROYALTY_RATES.printBelowThreshold;
-  const royaltyCents = Math.round(priceCents * royaltyRate / 100) - printingCents;
+  const royaltyCents = getKdpPrintRoyaltyCents(priceCents, royaltyRate, costHundredthCents);
   return {
     listPriceCents: priceCents,
     royaltyRate,
@@ -194,136 +144,6 @@ export function getKdpEbookPricePoint(priceCents: number, selectedRate: KdpEbook
   return { listPriceCents: priceCents, royaltyRate: effectiveRate, printingCostCents: null, deductionCents, royaltyCents, marginBasisPoints: Math.round(royaltyCents * 10_000 / priceCents) };
 }
 
-function uniquePricePoints(values: number[], min: number, max: number): number[] {
-  return [...new Set(values.filter((value) => Number.isInteger(value) && value >= min && value <= max))].sort((a, b) => a - b);
-}
-
-function copiesForTarget(target: number | undefined, royaltyCents: number): number | null {
-  if (target === undefined || !Number.isFinite(target)) return null;
-  if (target === 0) return 0;
-  if (target < 0 || royaltyCents <= 0) return null;
-  return Math.ceil(target * 100 / royaltyCents);
-}
-
-function monthlyTargetStatus(target: number | undefined, royaltyCents: number): KdpRoyaltyValues["monthlyTargetStatus"] {
-  if (target === undefined) return "omitted";
-  return target === 0 || royaltyCents > 0 ? "calculated" : "unavailable";
-}
-
-export function calculateKdpRoyalty(input: KdpRoyaltyInput): KdpRoyaltyResult {
-  const issues: KdpRoyaltyIssue[] = [];
-  const format = input?.format;
-  if (format !== "paperback" && format !== "hardcover" && format !== "ebook") issues.push(issue("format-invalid", "Choose paperback, hardcover, or ebook.", "error", "format"));
-  const listPriceCents = dollarsToCents(input?.listPrice);
-  if (listPriceCents === null) issues.push(issue("price-invalid", "Enter a positive list price.", "error", "listPrice"));
-  const monthlyTarget = input?.monthlyTarget;
-  if (monthlyTarget !== undefined && (!Number.isFinite(monthlyTarget) || monthlyTarget < 0)) issues.push(issue("target-invalid", "Enter a zero or positive monthly target.", "error", "monthlyTarget"));
-  if (issues.length) return { status: "invalid", values: null, issues };
-
-  if (format === "ebook") {
-    const fileSizeMB = input.ebookFileSizeMB;
-    const selectedRate = input.ebookRoyaltyOption ?? 70;
-    if (!Number.isFinite(fileSizeMB) || (fileSizeMB ?? 0) <= 0) issues.push(issue("file-size-invalid", "Enter the ebook file size in MB.", "error", "ebookFileSizeMB"));
-    if (selectedRate !== 35 && selectedRate !== 70) issues.push(issue("ebook-rate-invalid", "Choose the 35% or 70% rate.", "error", "ebookRoyaltyOption"));
-    if (issues.length) return { status: "invalid", values: null, issues };
-    const size = fileSizeMB as number;
-    const minimumPriceCents = ebookMinimumPriceCents(size);
-    if ((listPriceCents as number) < minimumPriceCents) issues.push(issue("ebook-price-too-low", `This file size needs a list price of at least $${(minimumPriceCents / 100).toFixed(2)}.`, "error", "listPrice"));
-    if ((listPriceCents as number) > EBOOK_MAX_PRICE_CENTS) issues.push(issue("ebook-price-too-high", "Ebook list price cannot exceed $200.", "error", "listPrice"));
-    const eligibleFor70 = (listPriceCents as number) >= EBOOK_SEVENTY_MIN_CENTS && (listPriceCents as number) <= EBOOK_SEVENTY_MAX_CENTS;
-    if (selectedRate === 70 && !eligibleFor70 && !issues.some((next) => next.severity === "error")) issues.push(issue("ebook-70-price-band", "This price uses the 35% rate instead of the selected 70% band.", "warning", "listPrice"));
-    if (issues.some((next) => next.severity === "error")) return { status: "invalid", values: null, issues };
-    const currentPoint = getKdpEbookPricePoint(listPriceCents as number, selectedRate, size);
-    const deliveryCents = currentPoint.deductionCents;
-    const effectiveRate = currentPoint.royaltyRate;
-    const royaltyCents = currentPoint.royaltyCents;
-    if (royaltyCents < 0) issues.push(issue("ebook-negative-royalty", "The delivery cost exceeds this price. This negative estimate does not mean KDP will charge you. Compare 35% or raise the price.", "warning"));
-    const pointPrices = uniquePricePoints([minimumPriceCents, 299, 1_299, 1_300, listPriceCents as number, (listPriceCents as number) + 100], minimumPriceCents, EBOOK_MAX_PRICE_CENTS);
-    const pricePoints = pointPrices.map((price) => getKdpEbookPricePoint(price, selectedRate, size));
-    return {
-      status: "valid",
-      values: {
-        format,
-        listPriceCents: listPriceCents as number,
-        effectivePageCount: null,
-        minimumListPriceCents: minimumPriceCents,
-        printingCostCents: null,
-        fixedCostCents: null,
-        pageCostCents: null,
-        deliveryCostCents: deliveryCents,
-        royaltyRate: selectedRate,
-        effectiveRoyaltyRate: effectiveRate,
-        royaltyCents,
-        royaltyMarginBasisPoints: Math.round(royaltyCents * 10_000 / (listPriceCents as number)),
-        breakEvenAdSpendCents: Math.max(0, royaltyCents),
-        breakEvenAcosBasisPoints: royaltyCents > 0 ? Math.round(royaltyCents * 10_000 / (listPriceCents as number)) : null,
-        copiesForMonthlyTarget: copiesForTarget(monthlyTarget, royaltyCents),
-        monthlyTargetStatus: monthlyTargetStatus(monthlyTarget, royaltyCents),
-        monthlyTargetCents: monthlyTarget === undefined ? null : Math.round(monthlyTarget * 100),
-        pricePoints,
-        ebookFileSizeMB: size,
-        ebookDeliveryRateCentsPerMB: 15,
-        sources: [KDP_SOURCES.ebookPricing, KDP_SOURCES.ebookDelivery],
-      },
-      issues,
-    };
-  }
-
-  const trimId = input.trimId;
-  const pageCount = input.pageCount;
-  const interior = input.interior;
-  const paper = input.paper;
-  if (typeof trimId !== "string" || !findKdpTrim(trimId)) issues.push(issue("trim-invalid", "Choose a supported trim size.", "error", "trimId"));
-  if (!Number.isSafeInteger(pageCount) || (pageCount as number) <= 0) issues.push(issue("page-count-invalid", "Enter a positive whole page count.", "error", "pageCount"));
-  if (interior !== "black-white" && interior !== "standard-color" && interior !== "premium-color") issues.push(issue("interior-invalid", "Choose a supported interior type.", "error", "interior"));
-  if (paper !== "white" && paper !== "cream" && paper !== "groundwood") issues.push(issue("paper-invalid", "Choose a supported paper type.", "error", "paper"));
-  if (issues.length) return { status: "invalid", values: null, issues };
-  const effectivePageCount = (pageCount as number) + ((pageCount as number) % 2);
-  const limit = getKdpPageLimit(trimId as string, format as KdpBinding, interior as KdpInterior, paper as KdpPaper);
-  if (!limit) issues.push(issue("trim-not-supported", "That trim and interior combination is not available for this binding.", "error", "trimId"));
-  if (limit && (effectivePageCount < limit.min || effectivePageCount > limit.max)) issues.push(issue("page-count-out-of-range", `Use ${limit.min} to ${limit.max} effective pages for this setup.`, "error", "pageCount"));
-  const trim = findKdpTrim(trimId as string);
-  const print = trim && printCost(format as KdpBinding, trimId as string, effectivePageCount, interior as KdpInterior, paper as KdpPaper);
-  if (!print) issues.push(issue("printing-cost-unavailable", "Printing cost is unavailable for this setup.", "error"));
-  if (issues.length) return { status: "invalid", values: null, issues };
-  const printingCents = printingCostCents(print as KdpPrintCost, effectivePageCount);
-  const minimumPriceCents = minimumPrintPriceCents(printingCents);
-  if ((listPriceCents as number) > PRINT_MAX_PRICE_CENTS) issues.push(issue("print-price-too-high", "Print list price cannot exceed $250.", "error", "listPrice"));
-  if ((listPriceCents as number) < minimumPriceCents) issues.push(issue("below-print-cost-floor", `Set the list price to at least $${(minimumPriceCents / 100).toFixed(2)} so your share of the price covers printing.`, "error", "listPrice"));
-  if (issues.some((next) => next.severity === "error")) return { status: "invalid", values: null, issues };
-  const pointPrices = uniquePricePoints([minimumPriceCents, 998, 999, listPriceCents as number, (listPriceCents as number) + 100], minimumPriceCents, PRINT_MAX_PRICE_CENTS);
-  const pricePoints = pointPrices.map((price) => getKdpPrintPricePoint(price, printingCents));
-  const royaltyRate = (listPriceCents as number) >= PRINT_ROYALTY_THRESHOLD_CENTS ? 60 : 50;
-  const royaltyCents = Math.round((listPriceCents as number) * royaltyRate / 100) - printingCents;
-  return {
-    status: "valid",
-    values: {
-      format,
-      listPriceCents: listPriceCents as number,
-      effectivePageCount,
-      minimumListPriceCents: minimumPriceCents,
-      printingCostCents: printingCents,
-      fixedCostCents: (print as KdpPrintCost).fixedCents,
-      pageCostCents: printingCents - (print as KdpPrintCost).fixedCents,
-      deliveryCostCents: null,
-      royaltyRate,
-      effectiveRoyaltyRate: royaltyRate,
-      royaltyCents,
-      royaltyMarginBasisPoints: Math.round(royaltyCents * 10_000 / (listPriceCents as number)),
-      breakEvenAdSpendCents: Math.max(0, royaltyCents),
-      breakEvenAcosBasisPoints: royaltyCents > 0 ? Math.round(royaltyCents * 10_000 / (listPriceCents as number)) : null,
-      copiesForMonthlyTarget: copiesForTarget(monthlyTarget, royaltyCents),
-      monthlyTargetStatus: monthlyTargetStatus(monthlyTarget, royaltyCents),
-      monthlyTargetCents: monthlyTarget === undefined ? null : Math.round(monthlyTarget * 100),
-      pricePoints,
-      ebookFileSizeMB: null,
-      ebookDeliveryRateCentsPerMB: null,
-      sources: [format === "hardcover" ? KDP_SOURCES.hardcoverCosts : KDP_SOURCES.printCosts, format === "hardcover" ? KDP_SOURCES.hardcoverRoyalties : KDP_SOURCES.paperbackRoyalties],
-    },
-    issues,
-  };
-}
-
 export function formatKdpMoney(cents: number): string {
   return `$${(cents / 100).toFixed(2)}`;
 }
diff --git a/skills/stack127/tools/stack127-tool-audit/SKILL.md b/skills/stack127/tools/stack127-tool-audit/SKILL.md
index c8b64012..06b5aaab 100644
--- a/skills/stack127/tools/stack127-tool-audit/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-audit/SKILL.md
@@ -1,19 +1,20 @@
 ---
 name: stack127-tool-audit
-description: Independently check one complete stack127 tool for correct answers, usable interaction, responsive rendering, clear content, and release readiness.
+description: Independently check one complete stack127 tool for correct answers, a simple Basic flow for most people, usable interaction, responsive rendering, clear content, and release readiness.
 ---
 
 # stack127 tool audit
 
-Audit-only requests are read-only. In the tool pipeline, report confirmed defects with their owner (backend, frontend, or copy) and do not fix them; the main agent sends backend defects to Sol, data defects to Luna, frontend defects to the Opus planning session, and copy to the Opus writing session.
+Judge the tool as its users would, without relying on the builder's explanation. Audits are read-only. Report each defect with its owner: backend to Sol, data to Luna, design, plan, or copy to the Opus planning session, and wiring or card art to integration.
 
-1. Read the tool spec, engine, route, the route's `content/*.mdx` files, focused tests, styles, and scripts. Use `stack127_docs/writing-style.md` when reviewing copy, `stack127_docs/page-content.md` for the content rules, and `stack127_docs/shared-ui.md` when checking components. Check that the content follows those rules: no h1 in content, headings that step down one level at a time, no eyebrows, the tool section order, only the listed blocks, and no placeholder text left in any content file.
-2. Check several independent normal, boundary, and invalid examples against primary sources or hand calculations.
-3. Use the real development page at desktop and mobile width. Follow `skills/stack127/references/homelab-browser-and-search.md` for a local headless browser when needed. Check the primary action, answer, recovery, keyboard use, focus, overflow, shared tables, charts, callouts, links, and content order where present. For each chart, check both themes, that no label is clipped, that the legend toggles and tooltip work, and that the page HTML stays well under 2 MB.
-4. Check basic privacy, escaping, untrusted output, timeouts, unknown versus zero, units, and rounding where they apply.
-5. Confirm development publication and version state. Check that the tool has one rank-1 primary catalog, appears once with the right card in every planned published catalog, has working links and sensible ordering, and does not appear while unpublished. For a new tool, confirm its tool-specific marker drawing is present and recognizable at the rendered card size on desktop and mobile in both themes; an `icon` fallback, unclear subject, overlap, or clipped art blocks release. When the tool is unpublished, inspect the generated art at card size and flag the public-card check for publication. If a publish manifest exists, run its `prepare` and `preview` against development and confirm its readiness checks pass and its values match what you checked. Report a mismatch as an integration defect. Never write production data without authorization.
-6. List wrong answers, broken common flows, accessibility failures, and responsive failures with their owner. After the owners fix them, rerun only the affected focused test or interaction.
+Read the spec, engine, route, `content/*.mdx`, and tests. Check against `stack127_docs/tool-interface.md`, `writing-style.md`, `page-content.md`, and `shared-ui.md`.
 
-Return the verdict, real defects and their owners, focused rechecks, and anything still blocking release. Do not create evidence folders, screenshots by default, hashes, receipts, or a second full test run.
+1. **Answers.** Check normal, boundary, and invalid examples against primary sources or hand calculations. Include unknown versus zero, units, rounding, timeouts, and escaping of untrusted output where they apply.
+2. **First use and depth.** Open the real development page as the first-time visitor in the spec's "People and questions", then as a pro in this domain. Does it open on an example with its result? Can the visitor get the answer from Basic without reading? Would the pro find what serious competitors offer in Advanced? Can they scan the result, with the main answer first and smaller numbers readable? Does every required field show `*`? Does every limit answer instead of blanking? Use the Review list in `tool-interface.md`.
+3. **Interaction.** Check desktop and mobile width in both themes: keyboard and focus, hints, overflow, charts, tables, links, and recovery from errors.
+4. **Content.** Content follows `page-content.md`, with no placeholders left.
+5. **Publication.** Development publication and version. One rank-1 primary catalog, and one card in each planned catalog. The tool-specific card art reads at real size in both themes, and an `icon` fallback blocks release. If a publish manifest exists, run its `prepare` and `preview` against development. Never write production data.
 
-For an existing tool, a change to inputs, results, calculations, validation, or other user-visible behavior needs a `tool_version` increase. Use a patch for a compatible fix, a minor version for compatible new behavior, and a major version for an incompatible contract change. Confirm the version with the coordinator before integration. The database moves the public date when the version changes. MDX content changes leave the version and the date alone; a date move for content-only tool changes comes later. Card-only edits refresh catalogs and keep the tool date unchanged. See `stack127_docs/tool-pages.md`.
+See `skills/stack127/references/homelab-browser-and-search.md` for a headless browser. After owners fix things, recheck only what changed.
+
+Return the verdict, the defects with owners, and anything still blocking release. Don't create evidence folders, screenshots by default, or hashes.
diff --git a/skills/stack127/tools/stack127-tool-backend/SKILL.md b/skills/stack127/tools/stack127-tool-backend/SKILL.md
index 826d29c7..2d546ab8 100644
--- a/skills/stack127/tools/stack127-tool-backend/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-backend/SKILL.md
@@ -20,4 +20,4 @@ Do not build the page, client components, styles, or card art. Do not write page
 
 Return the files you built, the exported functions or endpoints, the test result, and any contract gap.
 
-For an existing tool, a change to inputs, results, calculations, validation, or other user-visible behavior needs a `tool_version` increase. Use a patch for a compatible fix, a minor version for compatible new behavior, and a major version for an incompatible contract change. Confirm the version with the coordinator before integration. The database moves the public date when the version changes. MDX content changes leave the version and the date alone; a date move for content-only tool changes comes later. Card-only edits refresh catalogs and keep the tool date unchanged. See `stack127_docs/tool-pages.md`.
+For an existing tool, a behavior change needs a `tool_version` bump. See `stack127_docs/tool-pages.md`, and confirm the version with the coordinator.
diff --git a/skills/stack127/tools/stack127-tool-content-integration/SKILL.md b/skills/stack127/tools/stack127-tool-content-integration/SKILL.md
index 376c0b04..671972b4 100644
--- a/skills/stack127/tools/stack127-tool-content-integration/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-content-integration/SKILL.md
@@ -1,20 +1,21 @@
 ---
 name: stack127-tool-content-integration
-description: Integrate drafted or user-supplied tool copy and SEO text into the development page, then verify the result.
+description: Wire a finished stack127 tool into its development page, with its route, content, card art, catalogs, and publishing, then run the full checks. Also integrates user-supplied tool copy.
 ---
 
 # stack127 tool content integration
 
-Use this skill after `$stack127-tool-writing` in the normal pipeline, or when a user supplies replacement copy. Read the draft files or supplied words, the spec, `stack127_docs/page-content.md`, `stack127_docs/page-publishing.md`, `stack127_docs/tool-pages.md`, `stack127_docs/tool-catalogs.md`, `stack127_docs/seo.md`, the route, and current development rows. The introduction, usage, and article go in the route's `content/*.mdx` files. The visible title, search title and description, and shared catalog card copy go to the database through the publisher. Interface words live in frontend code, which the Opus writing session updates; do not edit UI code. Use `stack127_docs/writing-style.md` for any wording edits. If a required field is missing or a claim conflicts with the tool or sources, return it to the main agent for the writing session or resolve it with the user; do not invent replacement copy.
+Use this skill after `$stack127-tool-writing` in the normal pipeline, or when a user supplies replacement copy. You run in your own session, so the Opus planning session can stay on design and words. Connect and check; don't redesign or rewrite. Read the draft files or supplied words, the spec, `stack127_docs/page-content.md`, `stack127_docs/page-publishing.md`, `stack127_docs/tool-pages.md`, `stack127_docs/tool-catalogs.md`, `stack127_docs/seo.md`, the route, and current development rows. The introduction, usage, and article go in the route's `content/*.mdx` files. The visible title, search title and description, and shared catalog card copy go to the database through the publisher. Interface words and the tool component belong to the Opus planning session; edit only the route page, content wiring, and card art. Use `stack127_docs/writing-style.md` for any wording edits. If a required field is missing or a claim conflicts with the tool or sources, return it to the main agent for the planning session or resolve it with the user; do not invent replacement copy.
 
-1. Put the content in the route's `content/` folder: `intro.mdx`, `usage.mdx` when there is usage, and `article.mdx`. The writing session usually writes them. For supplied words, write them yourself with the blocks and rules in `page-content.md`. The page must import its MDX content before publishing.
-2. Wire the route as `/cac-payback-calculator` does: pass `<Intro />` to `ToolPageHeader`'s `intro`, and put `<Usage />` and `<Article />` inside `ToolPageArticle`. Run `node scripts/stack127/content/check-mdx.mjs` and fix what it reports.
+1. Put the content in the route's `content/` folder: `intro.mdx`, `usage.mdx` when there is usage, and `article.mdx`. The Opus planning session usually writes them. For supplied words, write them yourself with the blocks and rules in `page-content.md`. The page must import its MDX content before publishing.
+2. Wire the route as `/cac-payback-calculator` does, with `ToolPageShell` and the fetched `toolPage`. Pass `<Intro />` to `ToolPageHeader`'s `intro`, and put `<Usage />` and `<Article />` inside `ToolPageArticle`. Run `node scripts/stack127/content/check-mdx.mjs` and fix what it reports.
 3. Write the tool's publish manifest in `tmp/page-publishing/<slug>/`. Put the visible title in `content.title` and `meta_title` and `meta_description` in the registry patch when the draft changes them. A new tool also needs the content fields the publisher still requires; see "Content fields" in `page-publishing.md`. An unpublished page returns 404, and the publisher's check expects that 404. For a new tool in the pipeline, set `registry.is_published` to `true` explicitly so the development page can be previewed. Its catalogs must be published too. The same value carries to production at release. For other edits, leave publication fields alone unless the main agent asks.
 4. Read the spec's Catalog placement and the current catalog memberships. Confirm that the primary and every secondary catalog exist. Choose an unused display order for each new placement and the approved card icon and registered tool-specific art key. A new tool cannot use the `icon` art fallback. Put the card fields and the complete ordered catalog list in the manifest. Do not put cards in route code. If a new catalog is required and the main agent has not supplied it, return that work before using a substitute placement.
-5. Add the readiness requirements: the route file, the registered art file, any read-only SQL checks the tool needs, and smoke paths with expected visible text.
-6. Start `npm run dev` and `npm run stack127:cache:watch:local` as background services. Run the tools publisher's `prepare` and `preview` against development and review the result, then run `apply`. It also checks the public page. If it says the batch committed but the check failed, run `verify` with the same plan. Catalog card edits and membership changes do not change `tool_version`. Set a new version only when the main agent names one.
-7. Run `npm run quality`. Run only focused renderer, link, figure, or data checks when the changed code needs them.
-8. Open the actual development tool page and every assigned catalog, using the headless fallback in `skills/stack127/references/homelab-browser-and-search.md` when needed. Confirm the content renders in the right order, with its headings, blocks, and links, and that the card words, search metadata, and primary tool action work. For a published new tool, inspect its drawing at the real card size at desktop and mobile width in dark and light themes; simplify the spec and regenerate if its subject, spacing, or contrast fails. Unpublished tools stay out of public catalog cards until their registry row is published; inspect the generated art at card size and flag the public-card check for publication.
+5. Make the card art. Use `$marker-art-draw` with the spec's brief to make the `toolSpot` in `app/ui/art/`, register its key in `lib/card-art.ts`, and check it at card size. A new tool never uses the `icon` fallback.
+6. Add the readiness requirements: the route file, the registered art file, any read-only SQL checks the tool needs, and smoke paths with expected visible text.
+7. Start `npm run dev` and `npm run stack127:cache:watch:local` as background services. Run the tools publisher's `prepare` and `preview` against development and review the result, then run `apply`. It also checks the public page. If it says the batch committed but the check failed, run `verify` with the same plan. Catalog card edits and membership changes do not change `tool_version`. Set a new version only when the main agent names one.
+8. Run `npm run quality`. Run only focused renderer, link, figure, or data checks when the changed code needs them.
+9. Open the actual development tool page and every assigned catalog, using the headless fallback in `skills/stack127/references/homelab-browser-and-search.md` when needed. Use the tool at desktop and mobile width in both themes, with one correct example, one invalid example, and one value past a domain limit. Change each input and confirm the result moves. Open a hint by tap and by keyboard. Fix broken wiring yourself. Send design, layout, and copy problems to the main agent for the planning session. Confirm the content renders in the right order, with its headings, blocks, and links, and that the card words, search metadata, and primary tool action work. For a published new tool, inspect its drawing at the real card size at desktop and mobile width in dark and light themes; simplify the spec and regenerate if its subject, spacing, or contrast fails. Unpublished tools stay out of public catalog cards until their registry row is published; inspect the generated art at card size and flag the public-card check for publication.
 
 When content fixes come back, edit the MDX files. When title, search text, or card fixes come back, update the manifest and run the publisher in development again, so the manifest always matches what was checked. The single-purpose tool-page commands are fine for a quick development check of cards, version, or repository fields.
 
@@ -22,4 +23,4 @@ If the main agent wants a public page kept out of search while it is still being
 
 Do not calculate hashes, write receipts, or run a browser matrix. This integration task permits guarded development updates and the route and content file edits above. Production data, commits, pushes, and deployment need a separate coordinator-approved task under the rules in `AGENTS.md` and the release skill. Report the MDX files, the manifest path, changed fields, catalog ranks and orders, version, focused checks, and remaining issues.
 
-For an existing tool, a change to inputs, results, calculations, validation, or other user-visible behavior needs a `tool_version` increase. Use a patch for a compatible fix, a minor version for compatible new behavior, and a major version for an incompatible contract change. Confirm the version with the coordinator before integration. The database moves the public date when the version changes. MDX content changes leave the version and the date alone; a date move for content-only tool changes comes later. Card-only edits refresh catalogs and keep the tool date unchanged. See `stack127_docs/tool-pages.md`.
+For an existing tool, a behavior change needs a `tool_version` bump. See `stack127_docs/tool-pages.md`, and confirm the version with the coordinator.
diff --git a/skills/stack127/tools/stack127-tool-frontend/SKILL.md b/skills/stack127/tools/stack127-tool-frontend/SKILL.md
index 6dcd85a5..46c82277 100644
--- a/skills/stack127/tools/stack127-tool-frontend/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-frontend/SKILL.md
@@ -1,25 +1,17 @@
 ---
 name: stack127-tool-frontend
-description: Build the page, interface, tool components, styles, and card art for one stack127 tool on top of its finished backend, then check it at desktop and mobile width.
+description: Design and build the interface for one stack127 tool on top of its finished backend, the inputs, result, and every word in them, so people get their answer fast.
 ---
 
 # stack127 tool frontend
 
-In the tool pipeline, Opus runs this skill in the same planning session that wrote the spec, after Sol finishes the backend.
+Opus runs this in the planning session, after Sol finishes the backend. Your job is the people using this tool. Build the interface the spec planned so they get their answer fast and want to share it. A separate integration session wires the route, content, card art, and publishing after you and runs the full checks, so keep your attention on the user.
 
-Read the spec, the backend files Sol built, `stack127_docs/tool-pages.md`, `stack127_docs/page-content.md`, `stack127_docs/tool-interface.md`, `stack127_docs/shared-ui.md`, `stack127_docs/design-system.md`, and `stack127_docs/css-architecture.md`.
+Read the spec, the backend, and `stack127_docs/tool-interface.md`. Dig into `shared-ui.md`, `design-system.md`, and `css-architecture.md` when you need them. Call the backend only through its contract. If the backend is wrong, report it for Sol instead of patching it.
 
-Build the interface you planned. Call the backend only through its contract. If the backend does not match the contract or has a bug, do not patch it. Report it to the main agent so it goes back to Sol.
+1. **Interface.** Build what the spec planned inside `ToolWorkbench`, `ToolFieldRow`, and `ToolResult` from `app/ui/tools/tool-workbench.tsx`, with every word final: labels, hints, and buttons. It opens on the example and its result. Make the result something the person would want to share. Keep the client island small and the styles beside the route. Don't write your own workbench band, width, or section gaps. The page stays static, so read shared links in a `<slug>-from-url.tsx` client wrapper with `useInitialQuery()`. If the route doesn't exist yet, add a bare page with `ToolPageShell`, as `/cac-payback-calculator` does, so you can see your work.
+2. **Look at it.** Open the page at desktop and mobile width as a first-time visitor. Does the eye land on the answer? Can you scan the smaller numbers without labels wrapping? Try a few values and one invalid one. Fix what feels wrong. See `skills/stack127/references/homelab-browser-and-search.md` for a headless browser.
 
-1. Build the route page. Use `ToolPageShell` from `app/ui/tools/tool-page-shell.tsx` with the fetched `toolPage`. It resolves the primary catalog and sidebar from database memberships. Do not add a route-owned tool sidebar. Create `content/intro.mdx` and `content/article.mdx` beside the route with one clearly marked placeholder line each. Pass `<Intro />` to `ToolPageHeader`'s `intro` and put `<Article />` inside `ToolPageArticle`, as `/cac-payback-calculator` does. The writing session replaces the placeholders.
-2. Build the interface with the components named in the spec, one primary action, and one lead answer. Add only the tool-specific components the spec lists. Draw result charts with `UiLiveChart`. Charts in the page's own content use `UiStaticChart`, or `UiChart` when the reader needs hover, toggles, or ranges. Keep the client island small and colocate styles. The route page stays static: read shared-link values in a client wrapper with `useInitialQuery()` from `app/ui/tools/use-initial-query.ts`, never `searchParams` on the server page. See `stack127_docs/caching.md`.
-3. Handle every state in the spec: initial, valid, invalid, loading, empty, partial, failure, retry, reset, restored, and long values, as they apply.
-4. Use `$marker-art-draw` and the card art brief to create the tool's `toolSpot` in `app/ui/art/`. Generate its `.svg` and `.ts`, register a tool-specific key in `lib/card-art.ts`, and check it at card size. Do not use the `icon` fallback for a new tool.
-5. Start or reuse the homelab server. Use `skills/stack127/references/homelab-browser-and-search.md` for the local headless browser. Check the real page at desktop and mobile width in both themes with one correct example and one invalid example. Check keyboard use, focus, and overflow.
-6. Run `npm run quality`.
+For an existing tool, a behavior change needs a `tool_version` bump. See `stack127_docs/tool-pages.md`, and confirm the version with the coordinator.
 
-Leave the production build to the main agent. Do not write page content, publish production data, commit, push, or deploy.
-
-Return the files you built, what you checked, and any backend problem you found.
-
-For an existing tool, a change to inputs, results, calculations, validation, or other user-visible behavior needs a `tool_version` increase. Use a patch for a compatible fix, a minor version for compatible new behavior, and a major version for an incompatible contract change. Confirm the version with the coordinator before integration. The database moves the public date when the version changes. MDX content changes leave the version and the date alone; a date move for content-only tool changes comes later. Card-only edits refresh catalogs and keep the tool date unchanged. See `stack127_docs/tool-pages.md`.
+Don't write page content, make card art, publish data, commit, push, or deploy. Return the files, what you looked at, and any backend problem.
diff --git a/skills/stack127/tools/stack127-tool-interface-design/SKILL.md b/skills/stack127/tools/stack127-tool-interface-design/SKILL.md
index b6af0041..0de53f1d 100644
--- a/skills/stack127/tools/stack127-tool-interface-design/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-interface-design/SKILL.md
@@ -1,20 +1,16 @@
 ---
 name: stack127-tool-interface-design
-description: Refine an existing stack127 tool's controls, result hierarchy, states, responsiveness, and usability without changing its engine or article content.
+description: Refine an existing stack127 tool's inputs, result, and layout so it's simple for most people, without changing its engine or article content.
 ---
 
 # stack127 tool interface design
 
-Read the tool spec, `stack127_docs/tool-interface.md`, `stack127_docs/shared-ui.md`, `stack127_docs/writing-style.md`, the `/components-ui` gallery in development, and rendered page. Use the local headless fallback in `skills/stack127/references/homelab-browser-and-search.md` if the in-app browser is unavailable.
+Read the tool spec, `stack127_docs/tool-interface.md`, and the rendered page. Look at it as a first-time visitor would. Where does it make them read, dig for a number, or wonder what the result means? Fix that:
 
-- Make the next action and lead answer obvious.
-- Keep one primary action and visible labels.
-- Keep result-driving assumptions visible.
-- Remove repeated facts and regions that answer no new question.
-- Reuse shared controls when their behavior fits. Keep route-specific presentation local.
-- Keep overflow inside the content that needs it. Check long values and open disclosures at desktop and mobile width.
-- Preserve formulas, APIs, publication state, and the page's `content/*.mdx` files unless the request includes them.
+- Move refinements most people skip into Advanced, and turn helper text into hints.
+- Make the result about the person's own numbers, with a visual that makes it obvious.
+- Move sources and caveats out of the result and into the page content.
 
-Run only focused checks for changed behavior. Verify the actual page after editing.
+Keep formulas, APIs, publication state, and `content/*.mdx` unless the request includes them. If simplifying needs an engine change, such as a required field becoming optional, stop and report it for Sol. A bigger rework follows "Rework an existing tool" in `stack127_docs/tool-pipeline.md`.
 
-For an existing tool, a change to inputs, results, calculations, validation, or other user-visible behavior needs a `tool_version` increase. Use a patch for a compatible fix, a minor version for compatible new behavior, and a major version for an incompatible contract change. Confirm the version with the coordinator before integration. The database moves the public date when the version changes. MDX content changes leave the version and the date alone; a date move for content-only tool changes comes later. Card-only edits refresh catalogs and keep the tool date unchanged. See `stack127_docs/tool-pages.md`.
+Check the real page at desktop and mobile width after editing. A behavior change needs a `tool_version` bump. See `stack127_docs/tool-pages.md`.
diff --git a/skills/stack127/tools/stack127-tool-interface-plan/SKILL.md b/skills/stack127/tools/stack127-tool-interface-plan/SKILL.md
index 1d3587ba..a509476c 100644
--- a/skills/stack127/tools/stack127-tool-interface-plan/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-interface-plan/SKILL.md
@@ -1,36 +1,24 @@
 ---
 name: stack127-tool-interface-plan
-description: Define the controls, result hierarchy, states, shared components, and responsive behavior for one stack127 tool in tool-spec.md, and build any new or improved shared components it needs.
+description: Plan a stack127 tool's Basic and Advanced inputs, hints, result timing, visual result, and components in tool-spec.md, and build any new shared components it needs.
 ---
 
 # stack127 tool interface plan
 
-Edit the Interface section of `content_docs/<slug>/tool-spec.md`, plus shared components in `app/ui/` and their `/components-ui` gallery entries when the plan needs them.
+Opus runs this in the same planning session as `$stack127-tool-product-plan`. Fill the Interface section of `content_docs/<slug>/tool-spec.md`.
 
-In the tool pipeline, Opus runs this skill in the same Claude Code planning session as `$stack127-tool-product-plan`.
+Read "People and questions", `stack127_docs/tool-interface.md` (especially "How a stack127 tool feels" and "Good and bad tools"), and `stack127_docs/shared-ui.md`. Look at the `/components-ui` gallery and a few sibling tools.
 
-Read `research.md`, the "Why people will choose this tool" and Product sections, `stack127_docs/tool-interface.md`, `stack127_docs/shared-ui.md`, the `/components-ui` gallery in development, and relevant sibling tools.
+Picture two people using it: the first-time visitor from "People and questions", and a pro who knows this domain well. Plan what each of them sees, and make the calls a designer with taste would make:
 
-Decide:
+- **Inputs.** Fill the Inputs table: Basic, Advanced, required or optional, the final label and hint wording, and what each input changes. Cut any input that changes nothing, and keep every option the pro needs.
+- **Default state.** The example values it opens with, the result they produce, and the button's name.
+- **Result.** The answer, then the visual that makes it obvious for this tool. Think about the relationship you're showing and pick the best form from any ECharts type, a shared component, or a custom SVG. Then the supporting numbers, any detail Advanced adds, and a share action if it's worth sharing.
+- **Layout.** How the inputs group into `ToolFieldRow`s, and how the result reads at desktop and on phones. Ask where the eye lands first, and what someone who wants to dig in reads next.
+- **States.** Stale results after an edit, invalid input, each domain limit answering instead of blanking, and anything else this tool can really hit.
 
-- one user question, one lead answer, and one primary action;
-- the minimum visible inputs and which advanced choices genuinely change the answer;
-- distinct result regions with no repeated facts;
-- shared, new shared, or route-specific components for nontrivial controls;
-- initial, valid, invalid, loading, empty, partial, failure, retry, reset, restored, and long-value states that apply;
-- desktop and mobile order, containment, table behavior, keyboard flow, focus, and announcements;
-- any chart: its `UiLiveChart` kind, series, number format, and whether hover, toggles, or ranges help. See the Charts section of `stack127_docs/shared-ui.md`. A chart type that isn't registered yet gets added to `app/ui/charts/` now, with a gallery example.
+Sketch the desktop and phone layouts in words in the spec before building.
 
-## Components
+If a component or chart type you need doesn't exist, build it now as a shared piece with a gallery example. Check it at desktop and mobile width in both themes, and run `npm run quality`. Name each new piece in the spec.
 
-List every existing shared component the frontend will use. When no shared component fits, or an existing one falls short, build or improve it now:
-
-- Put it in `app/ui/` and follow `stack127_docs/shared-ui.md`, `stack127_docs/design-system.md`, and `stack127_docs/css-architecture.md`.
-- Make it useful beyond this one tool. Keep calculations, data sources, and tool-specific behavior out of it.
-- Add an example to the `/components-ui` gallery, in the section for its component type. See `stack127_docs/shared-ui.md`.
-- When changing an existing component, keep the pages that use it working.
-- Check it in the gallery and on the page types that use it, at desktop and mobile width in both themes. Run `npm run quality`.
-
-Name each new or improved component in the Interface section with its import path and what it is for.
-
-Use `stack127_docs/writing-style.md` for interface wording. Do not build the tool route, backend, or tool-specific components yet. Sol builds the backend next, then you build the frontend with `$stack127-tool-frontend` in this same session. Do not create a separate interface contract.
+Don't build the tool route or backend. Sol builds the backend next, then you build the frontend with `$stack127-tool-frontend` in this session.
diff --git a/skills/stack127/tools/stack127-tool-orchestrator/SKILL.md b/skills/stack127/tools/stack127-tool-orchestrator/SKILL.md
index 59247685..f3d61b6e 100644
--- a/skills/stack127/tools/stack127-tool-orchestrator/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-orchestrator/SKILL.md
@@ -5,25 +5,25 @@ description: Run a stack127 tool from research through writing, development inte
 
 # stack127 tool orchestrator
 
-Read `AGENTS.md` and `stack127_docs/tool-pipeline.md`. The main agent starts each worker, checks its result, returns real gaps to the same worker, and moves on. Follow "Agent roles" in `AGENTS.md`. Luna researches and integrates data. Sol builds the backend and audits. Opus plans, builds the frontend, and writes. Start each round with T3's `delegate_task` unless it is in your own lane, as described in the pipeline's Sessions section. Do not repeat specialist work or load every worker skill into the main context.
+You're the coordinator. Read `AGENTS.md` for the lanes and `stack127_docs/tool-pipeline.md` for the rounds, sessions, and checks. Start each worker with `delegate_task` unless the round is your own lane, read what comes back, and send real gaps back to the same worker. Don't redo a worker's job or load every worker skill yourself.
 
-## Run the pipeline
+Give each tool its own Opus planning session, and never hand that session a second tool or integration work. Other workers usually get one tool each too; share one across tools only when the work is small and alike.
 
-1. Confirm the tool name, flat route, primary job, repository, existing work, publication state, and likely catalog placement.
-2. Start research with `$stack127-tool-research`. Check that `content_docs/<slug>/research.md` is deep: real competitor use on 5 to 8 tools, search intent, user problems with links, verified facts, a comparison table, and a concrete list of how stack127 can win. Send thin research back to the same worker.
-3. Start one Claude Code planning session with Opus. It reads `research.md` and starts `tool-spec.md` from the template. Have it follow `skills/stack127/tools/stack127-tool-product-plan/SKILL.md`, then `skills/stack127/tools/stack127-tool-interface-plan/SKILL.md`. Read the spec against the research. Confirm it says why people will choose this tool, the plan is concrete enough to build without guessing, Product includes a specific tool card art brief, Product has a precise backend contract, and Interface names the existing components to use and any new or improved shared components Opus built and checked. Send suggestions and gaps back to the same session.
-4. Start `$stack127-tool-backend` with Sol. It builds the backend contract with a focused correctness test and, for a new database-backed route, a development preview row with a clearly marked placeholder title. It builds no UI. Send backend gaps back to Sol and contract gaps to the planning session.
-5. Resume the planning session at high effort with `skills/stack127/tools/stack127-tool-frontend/SKILL.md`. Opus builds the page, interface, tool components, styles, and registered card art on top of the backend, then checks the real page at desktop and mobile width. Send backend problems it reports to Sol, then back to Opus once fixed.
-6. Run `npm run quality` once after the backend and frontend are done. The full build runs in pull request CI on GitHub at release. Don't build on the homelab.
-7. Start one Claude Code writing session with Opus. Have it follow `skills/stack127/tools/stack127-tool-writing/SKILL.md`: plan the Content section of the spec first, then write the copy in the same session. Return factual or missing-copy corrections to that session. Once corrected, ask the same session for a final pass that makes all page copy simple and easy for a general reader to follow while keeping its details. Collect the final title, the route's `content/*.mdx` files, interface words, SEO text, card copy, and source notes. Do not pause for manual writing.
-8. Confirm the planned primary and secondary catalogs exist. If the spec calls for a new catalog, coordinate its registry row, content, art, and page review through the catalog page workflow before tool integration. Start `$stack127-tool-content-integration` with the final draft and registered art key. It writes the tool's publish manifest with `registry.is_published` set to `true`, because an unpublished route returns 404 and can't be previewed. It wires the MDX content into the route and runs the content check. It then applies the title, search metadata, card fields, memberships, and development publication with the tools publisher. Read the rendered tool and catalog pages. Check card art at its real size in both themes and desktop and mobile layouts. Check that copy makes sense as public-facing text, with no stray research notes, citation markers, or insider wording. Keep useful source links. Send copy problems to the writing session, have integration apply its corrections, and check the affected pages again.
-9. Start one independent `$stack127-tool-audit` worker after integration. Send backend defects to Sol, data defects to Luna, frontend and component problems to the planning session at high effort, and copy problems to the writing session. Rerun only affected checks. Run a new build only if integration or fixes changed route, runtime, or SEO code.
-10. Give the user the complete `content_docs/<slug>/tool-spec.md`, current Tailscale preview URL, what the finished tool does, and the audit verdict.
+Unless the user asks for speed, go slow: one tool at a time, with at most one or two agents running at once. Build shared work, such as one engine several tools use, once up front. See "Pace" in `tool-pipeline.md`.
 
-The local tool is complete when its known examples are correct, the actual page works at desktop and mobile width, its generated card art and catalog memberships are integrated, its publish manifest runs cleanly in development, the audit has no release blocker, and the minimum gate passes.
+To rework an existing tool, follow "Rework an existing tool" in `tool-pipeline.md` instead.
 
-Do not create acceptance receipts, evidence folders, file hashes, ownership manifests, stage validators, or a full browser suite.
+1. **Confirm** the tool name, flat route, job, existing work, publication state, and likely catalog.
+2. **Research**, with Luna and `$stack127-tool-research`. Send it back if it doesn't clearly say who uses the tool and what they ask, or if competitors weren't actually used.
+3. **Plan**, with the Opus planning session: `$stack127-tool-product-plan`, then `$stack127-tool-interface-plan`. Read the spec against the research. Does it take a real position on who it serves, keep Basic small and Advanced optional, give a precise backend contract, and plan a result worth sharing? Send gaps back.
+4. **Backend**, with Sol and `$stack127-tool-backend`. Contract gaps go to the planning session.
+5. **Interface**, back in the planning session, with `$stack127-tool-frontend`. Backend problems go to Sol.
+6. Run `npm run quality` once both are done. CI runs the build. Don't build on the homelab.
+7. **Writing**, back in the planning session, with `$stack127-tool-writing`. The session that planned the tool writes its page. After corrections, ask for one more pass that makes the copy plain for a general reader.
+8. **Integration**, in its own Luna session with `$stack127-tool-content-integration`, once every planned catalog exists. It wires the route and content, makes the card art, publishes to development, and runs the full checks. Read the rendered tool and catalog pages yourself, and send copy problems back to the planning session.
+9. **Audit**, with a fresh Sol worker and `$stack127-tool-audit`. Route each defect to its owner, and recheck only what changed.
+10. **Report**: the spec, the Tailscale preview URL, what the tool does, and the audit verdict.
 
-If production publication, commit, push, and deployment are already authorized after the final audit, invoke `$stack127-release-e2e`. It ships the code and page content first, then publishes the tool's database side with its manifest through the page publication workflow. Otherwise stop after the integrated development preview, give the manifest location, and ask once for release authorization.
+The tool is done when its examples are right, the real page works at desktop and mobile width, card art and catalogs are integrated, the publish manifest runs clean in development, and the audit has no blocker.
 
-For an existing tool, a change to inputs, results, calculations, validation, or other user-visible behavior needs a `tool_version` increase. Use a patch for a compatible fix, a minor version for compatible new behavior, and a major version for an incompatible contract change. Confirm the version with the coordinator before integration. The database moves the public date when the version changes. MDX content changes leave the version and the date alone; a date move for content-only tool changes comes later. Card-only edits refresh catalogs and keep the tool date unchanged. See `stack127_docs/tool-pages.md`.
+If release is already authorized, run `$stack127-release-e2e`. Otherwise stop at the development preview and ask once.
diff --git a/skills/stack127/tools/stack127-tool-orchestrator/references/research-template.md b/skills/stack127/tools/stack127-tool-orchestrator/references/research-template.md
index 9ec7bd26..701d51e5 100644
--- a/skills/stack127/tools/stack127-tool-orchestrator/references/research-template.md
+++ b/skills/stack127/tools/stack127-tool-orchestrator/references/research-template.md
@@ -4,6 +4,31 @@ Route: `/<slug>`
 Checked: <YYYY-MM-DD>
 Competitors used: <number>
 
+## Who uses it
+
+Who searches for this tool, and what they want to know. Base it on search results, "People also ask", competitor pages, and forums. Name the main group first.
+
+| Group | Rough share | What they already know | Their questions, in their words |
+| --- | --- | --- | --- |
+| Most people, such as a founder with one number from Stripe | Most | | |
+| Pros, such as a growth lead with cohort data | Few | | |
+
+Then answer in a few lines:
+
+- What do most people want in the first few seconds?
+- Which inputs can most people give offhand, and which need digging or a specialist?
+- What do pros need that most people would skip?
+
+## Published comparison data
+
+Published ranges people use to judge their number, if any exist. Write "None" for tools where no comparison makes sense, such as most lookups.
+
+| Figure | Source and date | Who was measured | Same definition as the tool? |
+| --- | --- | --- | --- |
+| | | | |
+
+Say whether the sources agree closely enough to show one range in the tool, and which one. If they don't, say so.
+
 ## Scope
 
 What job this tool covers and what it leaves out. List the search queries you tried and the domains that keep showing up.
diff --git a/skills/stack127/tools/stack127-tool-orchestrator/references/tool-spec-template.md b/skills/stack127/tools/stack127-tool-orchestrator/references/tool-spec-template.md
index a05c0927..9e1fd3b5 100644
--- a/skills/stack127/tools/stack127-tool-orchestrator/references/tool-spec-template.md
+++ b/skills/stack127/tools/stack127-tool-orchestrator/references/tool-spec-template.md
@@ -6,6 +6,16 @@ Research: [research.md](research.md)
 
 Opus starts this file from the research. Link to research instead of copying it.
 
+## People and questions
+
+Take a position from the research's "Who uses it" section. Write it as decisions, not a survey:
+
+- Most users are: <who>. They come with: <what they know>.
+- Their top questions: <2 or 3, in their words>.
+- Basic answers them with: <the fewest inputs most people know offhand>.
+- Advanced holds: <each option pros need>, for <who>, because <reason>. Cover what serious competitors offer and what the old tool did, if there was one.
+- Left out: <what>, because <reason a user would agree with>.
+
 ## Why people will choose this tool
 
 What the searcher is really trying to decide. Where the top results fail them. The specific things this tool does better, such as a clearer answer, honest unknowns, edge cases handled, worked examples, or dated sources. Keep it to a short list the builders and writer can check against.
@@ -22,7 +32,7 @@ Define inputs, parsing, units, bounds, formulas or source precedence, rounding,
 
 ### Backend contract
 
-The exact handoff between Luna's backend and Opus's frontend. List each exported function or API route with its file path, inputs and types, output shape, errors and unknown values, and timeouts or caching. Name any data script, migration, or dataset. The frontend calls the backend only through this contract.
+The exact handoff between Sol's backend and Opus's frontend. List each exported function or API route with its file path, inputs and types, output shape, errors and unknown values, and timeouts or caching. Name any data script, migration, or dataset. The frontend calls the backend only through this contract.
 
 ### Known examples
 
@@ -30,7 +40,7 @@ Add a small set of independently calculated normal, boundary, and invalid exampl
 
 ### Ownership
 
-List the backend files Luna builds (engine, API routes, scripts, focused test, preview row) and the frontend files Opus builds (route page, components, styles, card art).
+List the backend files Sol builds (engine, API routes, scripts, focused test, preview row) the interface files Opus builds (components and styles), and what integration adds (route page, content wiring, card art).
 
 ### Catalog placement
 
@@ -42,23 +52,35 @@ For a new tool, brief its catalog `toolSpot` marker art: one visual takeaway, a
 
 ### Flow
 
-State the user question, minimum inputs, primary action, lead answer, and supporting result order.
+State the user question, the lead answer, the example values the tool opens with, and the button's name.
+
+### Inputs
+
+| Input | Basic or Advanced | Required or optional | Hint, one sentence or none | What it changes in the result |
+| --- | --- | --- | --- | --- |
+| | | | | |
+
+Every Advanced input is optional. Name the Advanced disclosure for what's inside. If an input changes nothing in the result, cut it.
+
+### Result
+
+The answer, the visual that shows it, the few supporting numbers, and share or copy actions. Everything in the result comes from the person's inputs. Say what comparison shows, if any, and which published range it uses. No grade words.
 
 ### Components
 
 List every existing shared component the frontend uses, with its import path. List any new or improved shared components built during planning, with what each one is for. List the tool-specific components the frontend will build, with a short description.
 
-### States
+### Layout
 
-List the initial, valid, invalid, loading, empty, partial, failure, retry, reset, restored, and long-value states that apply.
+How the inputs group into rows, where Advanced sits, and how the result reads at desktop and on phones: what the eye lands on first, and where the smaller numbers and detail sit.
 
-### Responsive and accessible behavior
+### States
 
-Describe desktop and mobile order, containment, table or chart behavior, keyboard flow, focus, and announcements.
+The example it opens with, stale results after an edit, invalid input, and how each domain limit answers instead of blanking. Add any other state this tool can really hit.
 
 ## Content
 
-The writing session fills this section with `skills/stack127/tools/stack127-tool-writing/SKILL.md`. Page copy uses existing components only.
+The planning session fills this section, after the frontend, with `skills/stack127/tools/stack127-tool-writing/SKILL.md`. Page copy uses existing components only.
 
 ### Search intent and title
 
diff --git a/skills/stack127/tools/stack127-tool-product-plan/SKILL.md b/skills/stack127/tools/stack127-tool-product-plan/SKILL.md
index e49a5779..7fb29791 100644
--- a/skills/stack127/tools/stack127-tool-product-plan/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-product-plan/SKILL.md
@@ -1,37 +1,39 @@
 ---
 name: stack127-tool-product-plan
-description: Start a stack127 tool-spec.md from research.md and write the reasons people will choose the tool and its concrete product and technical contract, without implementing it.
+description: Start a stack127 tool-spec.md from research.md and write who the tool serves, why people will choose it, and its concrete product and technical contract, without implementing it.
 ---
 
 # stack127 tool product plan
 
-In the tool pipeline, Opus runs this skill in the Claude Code planning session, then continues with `$stack127-tool-interface-plan` in the same session.
+Opus runs this in the planning session, then continues with `$stack127-tool-interface-plan`.
 
-Read `content_docs/<slug>/research.md` in full. Create `content_docs/<slug>/tool-spec.md` from `skills/stack127/tools/stack127-tool-orchestrator/references/tool-spec-template.md`, or continue the existing spec. Write the "Why people will choose this tool" and Product sections.
+Read `content_docs/<slug>/research.md` and `stack127_docs/tool-interface.md`. Create or continue `content_docs/<slug>/tool-spec.md` from `skills/stack127/tools/stack127-tool-orchestrator/references/tool-spec-template.md`.
 
-## Plan the tool people want
+## Decide who it's for
 
-Before writing the contract, answer three questions from the research:
+Write "People and questions" first. Everything else follows from it. Take a position, the way a good product lead would:
 
-1. What is the searcher really trying to decide or produce?
-2. Where do the current top results fail them?
-3. What will this tool do better?
+- Who most users are, and the 2 or 3 questions they bring.
+- What Basic answers, with the fewest inputs those people know offhand.
+- What Advanced holds, for whom, and why. This is where the depth lives: everything a pro would expect from a serious tool in this space, from the research's competitors and forum questions, and everything the old tool did if there was one. Every Advanced input is optional, so say what empty means, such as "no discount entered: use the list price."
+- What you're leaving out, with a reason a user would agree with. "Pros can use another tool" isn't one.
+- The realistic example values the tool opens with, and whether a published comparison fits.
+- The domain's real limits, such as a platform's maximum or minimum, and how the result answers when someone hits one.
 
-Plan the tool a person would pick over every current result: more useful, faster to a clear answer, and honest about unknowns. Do not copy a competitor's layout or add features only because others have them. Where research is thin or a key competitor is missing, use a few more competitors and add your findings to `research.md`.
+Then write "Why people will choose this tool": where the top results fail these people, and what this tool does better. Don't copy a competitor's layout or add features because others have them.
 
 ## Write the contract
 
-Define:
+Make it concrete enough that Sol and the frontend can each build to it without guessing:
 
-- the primary user, job, promise, and reason to use this tool;
-- launch scope and clear exclusions;
-- inputs, units, bounds, parsing, formulas or source precedence, rounding, and output;
-- invalid, unknown, partial, failure, privacy, and security behavior;
-- one primary action and the important state changes;
-- a backend contract: each exported function or API route with its file path, inputs, output shape, errors, unknown values, and any timeouts, caching, scripts, or datasets. Sol builds to it and the frontend calls only through it;
-- a few independently calculated examples that the backend test can use for correctness checks;
-- which files Sol builds for the backend and which files Opus builds for the frontend;
-- one primary catalog and any secondary catalogs, with a short reason for each; flag a missing catalog for the main agent to create through the catalog page workflow;
-- a `toolSpot` brief for the new tool's catalog card: one visual takeaway, recognizable focal subject, at most one supporting object or relationship, semantic tone, and tool-specific art key. Keep it wordless and legible at card size in both themes.
+- Scope and exclusions.
+- Inputs with units, bounds, and parsing. Formulas or source precedence, rounding, and output.
+- Invalid, unknown, partial, and failure behavior.
+- The backend contract: each exported function or API route, with its path, inputs, output shape, and errors.
+- A few independently calculated examples for the backend test.
+- Which files Sol builds and which Opus builds.
+- Catalog placement, and a `toolSpot` card art brief. See the template.
 
-Make the plan concrete enough to build without guessing. Do not create requirement IDs, fingerprints, validators, receipts, code, or tests.
+For a rework, update "People and questions" from the new research and list the engine changes Sol must make. Keep what's still right.
+
+Don't write code, tests, IDs, or validators.
diff --git a/skills/stack127/tools/stack127-tool-research/SKILL.md b/skills/stack127/tools/stack127-tool-research/SKILL.md
index 7ce33de2..6df5925f 100644
--- a/skills/stack127/tools/stack127-tool-research/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-research/SKILL.md
@@ -1,20 +1,20 @@
 ---
 name: stack127-tool-research
-description: Research one stack127 tool in depth, use competitors for real, check search intent and user problems, verify facts with primary sources, and write content_docs/<slug>/research.md.
+description: Research one stack127 tool in depth, find who uses it and what they ask, use competitors for real, check search intent and user problems, verify facts with primary sources, and write content_docs/<slug>/research.md.
 ---
 
 # stack127 tool research
 
-Write only `content_docs/<slug>/research.md`. Use `skills/stack127/tools/stack127-tool-orchestrator/references/research-template.md`. Do not create or edit `tool-spec.md`; Opus starts it from this research.
+Write `content_docs/<slug>/research.md` from `skills/stack127/tools/stack127-tool-orchestrator/references/research-template.md`. The planner builds the tool from it, so give them what they need to decide well.
 
-The goal is to know the topic, the searcher, and the competition well enough that the planner can build the tool people would pick over every current result.
+1. **Start with the people.** Who searches for this, what do they already know, and what do they want answered in the first few seconds? Find out from search results, "People also ask", competitor pages, and forum threads, not guesses. Say which inputs most people can give offhand and which need digging.
+2. **Find published comparison data**, if any: figures people use to judge their own number, with source, date, who was measured, and whether it measures the same thing. Say whether the sources agree well enough to show one range.
+3. **Use 5 to 8 competitors for real**: the official tool, the top results, and tools people recommend. Try a correct example, an edge case, and a wrong input on each. Note what they get right, where people get stuck, and the options the serious ones offer that pros rely on. Those become Advanced.
+4. **Verify the facts** that drive answers (formulas, limits, units, data dates) with official docs or source code, including the domain's hard limits, such as a platform's maximum. Mark anything unverified as unknown.
+5. **Say how stack127 can win**, concretely, and flag anything that needs approval, such as paid APIs or maintained datasets.
 
-1. Confirm the user job, flat route, and whether a stack127 tool already covers it.
-2. Search the exact tool name, the user's job in plain words, specialist terms, and common problems. Record what the searcher wants for each query, the "People also ask" questions, and what the top results miss.
-3. Find real user problems in forums, Reddit, communities, support threads, and reviews. Link each one.
-4. Use 5 to 8 competitors for real: the official tool if one exists, the top search results, and tools people recommend. Try one correct example, one edge case, and one wrong input on each. Use `skills/stack127/references/homelab-browser-and-search.md` for the local headless browser when the in-app browser is unavailable. Stop early only when new competitors repeat known patterns.
-5. Verify formulas, standards, limits, units, data dates, and security facts with official documentation or source code. Mark unsupported facts as unknown.
-6. Fill the comparison table, note where competitors disagree and which answer is right, and write a concrete list of how stack127 can win.
-7. Flag paid APIs, maintained datasets, background jobs, accounts, or other work that needs approval.
+For a headless browser, see `skills/stack127/references/homelab-browser-and-search.md`.
 
-Do not plan the interface, write public copy, implement code, create evidence files, or add hashes. Return the research file path and any blocker.
+For a rework of an existing tool, add only "Who uses it" and "Published comparison data" to the existing file. If an older tool has no `research.md`, create one with those two sections and link the older docs in its folder.
+
+Don't plan the interface, write page copy, or write code. Return the file path and any blocker.
diff --git a/skills/stack127/tools/stack127-tool-writing/SKILL.md b/skills/stack127/tools/stack127-tool-writing/SKILL.md
index 28d6338c..ced3e30b 100644
--- a/skills/stack127/tools/stack127-tool-writing/SKILL.md
+++ b/skills/stack127/tools/stack127-tool-writing/SKILL.md
@@ -5,129 +5,28 @@ description: Plan and write, or rewrite, the content, title, page copy, interfac
 
 # stack127 tool writing
 
-Read `stack127_docs/writing-style.md` for how to write and search wording, and `stack127_docs/page-content.md` for the content files, the MDX blocks, and the content rules. Read `content_docs/<slug>/research.md` and `tool-spec.md` when they exist. Check every claim against the tool and its sources.
+You're writing for one person: someone who just searched for this tool because something is bugging them. Talk to them like a friend who knows the subject. Get what they're stuck on, explain it simply, and clear up every doubt they'd still have. Then stop.
 
-## When to use it
+Before you write, read the research and spec, and use the finished tool with a real example. Think about this person. What's going on for them? What are they trying to decide? What would they still wonder after seeing the answer? Read the intros of two or three other tools in the same catalog, so this page sounds like its own and not like theirs.
 
-In the tool pipeline, Opus runs this skill in its own Claude Code writing session after the tool is built. Plan the Content section first, then write in the same session.
+Read `stack127_docs/writing-style.md` for the voice and `stack127_docs/page-content.md` for the files and MDX blocks. Check every claim against the tool and its sources.
 
-It also handles rewrites of live tool pages. Read the current content in the route's `content/*.mdx` files, and the title and search text on the page. Read and edit its MDX files. Tools, directories, and catalogs have no database-content fallback. Use the tool once and read its code for the exact rules and messages. Keep the facts, limits, and sources a reader needs, and cut what goes beyond the core of the tool. Skip the spec step for a rewrite.
+## The page
 
-It also covers catalog pages, such as `/dns-tools`: the title, the intro above the cards, the article below them, and the search text. A catalog's content lives in a folder named for its slug under `app/(site)/(catalogs)/[slug]/content/`. See `page-content.md`.
+| Part | Lives in | Its job |
+| --- | --- | --- |
+| Intro | `content/intro.mdx` | Meet the reader where they are, hook them with their own problem, and point them to the tool. |
+| Usage | `content/usage.mdx` | Walk a new user through the tool as if you're sitting beside them: what each input means, what to try, and how to read the result. A conversation, not a glossary. |
+| Content | `content/article.mdx` | What helps them next. Mention related stack127 tools where they naturally come up, linked inside the sentence, never as a list. Leave out anything this reader doesn't need. Published figures and their sources go here, never in the result. Never call a number good or bad. |
+| Interface words | Frontend code | Labels and one-sentence hints. See "Words inside a tool" in `writing-style.md`. |
+| Title, SEO title, description, card copy | Database, through the publisher | "Tool name: the question it answers", in the words people search. |
 
-## Win the search
+In the pipeline, the Opus session that planned the tool writes its page, after planning the spec's Content section. Use this skill for rewrites of live tool pages too, editing the route's MDX directly, and for catalog pages such as `/dns-tools`, whose content lives in `app/(site)/(catalogs)/[slug]/content/`.
 
-The page should be the best answer for the searcher. Before planning, answer three questions from the research or, for a rewrite, from a quick look at the top results:
+## Hand off
 
-1. What is the searcher really trying to decide or produce?
-2. Where do the top results fail them?
-3. What will this page do better?
+Run `node scripts/stack127/content/check-mdx.mjs`. In the pipeline, apply interface word changes in the frontend code yourself. For a standalone rewrite, list them instead.
 
-Then:
+Return the MDX paths with word counts, the title, SEO title and description, the card name and description, the interface words, and sources for factual claims.
 
-- Put the tool and its answer before explanations.
-- Answer the questions people really ask that the top results answer badly.
-- Show a worked example with real numbers.
-- Be honest about limits. Say what the tool can't tell you and when a result is an estimate.
-- Use primary sources and say when the data was checked.
-- Add at least one useful thing the top results don't have.
-
-## Stay on the core
-
-A tool page has two jobs: help the reader understand the idea behind the tool, and help them use it and trust the result. Write only what serves those jobs. Typical topics:
-
-- what the thing is and why it matters;
-- what to enter and where to find each number;
-- how to read the result, with one worked example;
-- the formula or rule;
-- the few questions people search and ask about it.
-
-There is no fixed list of sections. Judge each one by asking whether a typical reader of this tool would want it. If not, cut it.
-
-Leave out:
-
-- How the tool handles rare inputs, such as calculation limits, very small amounts, rounding, or extreme values. The result messages and the spec cover these. Explain an unusual result only when ordinary readers often see it.
-- Input format rules. These belong in field hints and error messages.
-- Tables or walkthroughs of special cases that exist to show the tool is correct.
-- Second sections that repeat a rule already given.
-- Background that doesn't help the reader use the tool or understand the result.
-
-Longer is not better. A focused page that answers the searcher quickly beats a long page that covers everything.
-
-## Plan first
-
-In the pipeline, write the plan in the Content section of `content_docs/<slug>/tool-spec.md`.
-
-1. Use the finished tool once with a real example. Note what the result shows and what a reader might misread.
-2. List the questions searchers ask, from research. Keep only the ones a typical reader of this tool would ask. Drop rare cases and questions that only matter for testing the tool.
-3. Map each question to where it is answered: the tool result, intro, usage, or content.
-4. Outline the page with the structure below. Name each content heading as the question it answers, and pick a format for each from `writing-style.md`.
-5. List what you left out on purpose, and say where it is handled instead, such as a result message, a field hint, or the spec.
-6. Note the facts the page states, their sources, claims to avoid, and the next stack127 pages to link.
-
-Refer to facts in the research instead of copying them.
-
-## Page structure
-
-| Part | Where it shows | Where it lives | What to write |
-| --- | --- | --- | --- |
-| Title | Page heading | Database, through the publisher | "Tool name: the question it answers", in words people search for. Example: "KDP payment date calculator: when will KDP pay you?" |
-| Intro | Above the tool | `content/intro.mdx` | 2 to 3 sentences. What you get, and what to have ready. No history or filler. |
-| Usage | After the tool | `content/usage.mdx` | Steps that need explaining, how to read the result, and one worked example. |
-| Content | After usage | `content/article.mdx` | Short sections with `##` question headings, each answered in its first sentence. |
-
-The SEO title, SEO description, and card copy also go to the database through the publisher.
-
-### Usage steps
-
-Every step must tell the reader something the form doesn't.
-
-- Cut: "Pick the format." "Select Calculate."
-- Keep: where to find a number, what a term means, which choice to pick when unsure.
-
-Beginners should be able to follow along without reading steps that only name buttons.
-
-### Content sections
-
-Pick only what this tool's readers need. This order is a guide, not a checklist:
-
-1. How it works: the rule or formula, with an example. For lookups and checks, what is checked and where the data comes from.
-2. What the result means, including good and bad results. Use benchmarks only with a source.
-3. Common mistakes people actually make.
-4. Related questions people search, from research.
-5. What the tool doesn't cover, in a line or two, and next stack127 tools.
-
-Keep each section to 1 to 3 short paragraphs, or one table, list, or visual with a line or two around it.
-
-## Keep it short and visual
-
-- Show first. Use a table, list, chart, example, formula, note, or warning when it shows the idea better than a paragraph. See the format table in `writing-style.md`.
-- Use marker art only for a concept that needs a picture, such as a flow or a rough relationship. Use at most one or two per page. Request it through the marker art skills; don't invent figure references.
-- Use only the blocks `page-content.md` lists. Page copy never needs a new one.
-- Say each idea once. The intro, usage, and content must not repeat each other.
-- Say whether a number is exact, an estimate, or a rule of thumb.
-- For lookups and checks, say what the result can and cannot tell the reader.
-- A rewrite should not be longer than the current page unless it adds something the reader was missing. Say what you added in the handoff.
-
-## Final pass
-
-After corrections, reread everything as a first-time visitor. Cut repetition, padding, steps that only name buttons, and any section that goes beyond the core of the tool. Keep the details and limits a typical reader needs. Remove research notes, source labels, citation markers, and insider wording. Keep source links that help the reader.
-
-If the main agent finds a problem on the rendered page, fix it in the same session and return the corrected words.
-
-## Hand off the copy
-
-Write the intro, usage, and content into the route's `content/intro.mdx`, `content/usage.mdx`, and `content/article.mdx`, following the rules in `page-content.md`. Run `node scripts/stack127/content/check-mdx.mjs` and fix what it reports. The content ships with a code release. Integration puts the title, search text, and card copy in the publish manifest. In the pipeline, apply interface-word changes in the frontend code yourself, since Opus owns the frontend. For a standalone rewrite, list suggested interface words instead.
-
-Return:
-
-- the MDX file paths and word counts before and after;
-- the visible title, SEO title, and SEO description;
-- a short card name and task-focused card description, which appear in every assigned catalog;
-- interface words changed or suggested;
-- any marker art you suggest;
-- sources for factual claims.
-
-Keep the spec as planning. The MDX files are the page content.
-
-A tool's public date moves with its version, title, and search text. Content edits leave `tool_version` and the date alone; a date move for content-only tool changes comes later. Card-only edits refresh catalogs and keep the tool date unchanged. Functional tool changes use the version workflow in `stack127_docs/tool-pages.md`.
+Content edits leave `tool_version` and the public date alone. See `stack127_docs/tool-pages.md`.
diff --git a/stack127_docs/design-system.md b/stack127_docs/design-system.md
index c4d5bde9..494b7b30 100644
--- a/stack127_docs/design-system.md
+++ b/stack127_docs/design-system.md
@@ -36,7 +36,7 @@ The old token scale is gone. That includes `--text-sm`, `--color-accent-soft`, `
 
 ## Color rules
 
-- The accent is a spotlight, not a paint bucket. Per view, `--color-accent` fills at most these: the h1 mark phrase, one primary button, the active pagination page, the focus ring, and the active tab underline. Anything else that needs attention uses `--color-accent-text` or a border.
+- The accent is a spotlight, not a paint bucket. Per view, `--color-accent` fills at most these: the h1 mark phrase, one primary button, the active pagination page, the focus ring, and the active tab underline. Anything else that needs attention uses `--color-accent-text` or a border. Charts and result visuals are data, not accent: they use the `--color-data-*` palette, whose first color is also chartreuse.
 - Text on an accent fill always uses `--color-accent-contrast`. Never white on chartreuse.
 - Accent-colored text always uses `--color-accent-text`. Raw `#bafc3c` fails contrast as text on the light background.
 - Semantic color only colors words, and only when the meaning is real. Use `--color-success-text`, `--color-warning-text`, and `--color-danger-text`. No tinted panels, no colored left edges, no badge soup.
diff --git a/stack127_docs/shared-ui.md b/stack127_docs/shared-ui.md
index 87dbfbef..026c76b4 100644
--- a/stack127_docs/shared-ui.md
+++ b/stack127_docs/shared-ui.md
@@ -10,7 +10,7 @@ The Components UI gallery is at `/components-ui` in development. That route retu
 | --- | --- |
 | Text, search, dates, numbers, choices, sliders, and actions | `app/ui/controls.tsx` |
 | File selection and file lists | `app/ui/uploads.tsx` |
-| Results, metrics, key-value lists, tables, progress, allocation bars, steps, and timelines | `app/ui/display.tsx` |
+| Results, metrics, key-value lists, tables, progress, allocation bars, range markers, unit grids, steps, and timelines | `app/ui/display.tsx` |
 | Interactive charts on pages | `UiChart` in `app/ui/charts/chart.tsx` |
 | Charts nobody needs to interact with, such as in articles | `UiStaticChart` in `app/ui/charts/chart-static.tsx` |
 | Charts of data computed in the browser, such as tool results | `UiLiveChart` in `app/ui/charts/chart-client.tsx` |
@@ -56,6 +56,23 @@ Show each look once. When a thin wrapper renders the same thing as another compo
 - Keep calculations, data sources, and unusual interactions with the page or tool that owns them.
 - Static displays go in server-renderable modules. Interactive controls go in client modules.
 
+## Tool inputs and results
+
+These pieces carry the rules in [tool-interface.md](tool-interface.md): simple Basic inputs, optional Advanced inputs, no text under fields, and personal visual results.
+
+| Need | Use |
+| --- | --- |
+| The tool's band, working width, field rows, and result region | `ToolWorkbench`, `ToolFieldRow`, and `ToolResult` in `app/ui/tools/tool-workbench.tsx`. Every tool uses them instead of its own workbench CSS. `ToolResult stale` turns a result's visuals gray when its inputs changed; pair it with an `Inputs changed` status. |
+| A required field | The `required` prop on any field, choice group, or select. It shows `*` beside the label, and screen readers hear `Required`. |
+| Explain a label in one sentence | The `hint` prop on any field, choice group, select, slider, or date control. It draws a small `?` beside the label. The sentence shows on hover, keyboard focus, and tap, and screen readers hear it as the field's description. |
+| Optional refinements | `UiDisclosure` below the Basic inputs, named for what's inside. Pass `summary={uiSetSummary(count)}` so the closed row says `Not used` or `2 set`. Control `isExpanded` to open it when a field inside has an error. |
+| Your value against a published range | `UiRangeMarker` in `app/ui/display.tsx`. It draws a neutral track, the published bands, and a `You` marker. It never grades. Each band can carry a `hint` naming its source. An optional `range` draws where the person's own value probably sits, such as a likely range at a small sample size. Its legend is a vertical list, one row per range with its value on the right. |
+| A share of people or items, such as 8 of every 100 who started a trial | `UiUnitGrid` in `app/ui/display.tsx`. It fills units out of 100, row by row, with a partly filled last unit. An optional `target` outlines the units up to a goal. |
+| Supporting result numbers | `UiMetricGroup` in `app/ui/display.tsx`. The default lays numbers out in columns. `layout="list"` gives one row per number, label on the left and value on the right, for numbers people read down. Each item can carry a `hint`. |
+| A link that reopens the tool with the same inputs | `UiShareAction` in `app/ui/controls.tsx`. Pass the inputs as `params`. It copies the link without changing the address bar, and falls back to a selectable link when copying fails. |
+
+Don't use `description` on tool fields. It stays for forms outside tools, such as feedback forms, where a visible line under the field is the right choice.
+
 ## Navigation and feedback
 
 `Pagination` takes `currentPage`, `totalPages`, an accessible `ariaLabel`, and `hrefForPage(page)`. The page owns the URL builder, so active filters and sorting stay in the links. Page one uses the clean listing URL. Previous and next turn into inactive text at the ends.
@@ -74,6 +91,8 @@ Show each look once. When a thin wrapper renders the same thing as another compo
 
 Every chart is Apache ECharts through one wrapper. Pass data; the wrapper draws it in the site style, in both themes. Give every chart a useful title.
 
+Any ECharts chart type can be used. The kinds below are already in the wrapper. When a different type shows the data better, such as a sunburst, boxplot, calendar, or pictorial bar, add it. See [Add a chart type](#add-a-chart-type).
+
 | Component | Use |
 | --- | --- |
 | `UiChart` | Interactive charts on pages. The server draws the chart as SVG, so it shows before scripts load and search engines see it. The browser then adds hover, toggles, and ranges. |
@@ -93,6 +112,11 @@ All three take a `spec`: the chart's `kind`, its data, a `title`, an optional `c
 | `donut` | Parts of one total, with the total in the middle. |
 | `scatter` | Two measures for each item. |
 | `heatmap` | A value across two categories, such as hour and weekday. |
+| `funnel` | Stages that narrow, in order, such as visitors to trials to paid. |
+| `gauge` | One value against a scale, such as progress toward a goal. |
+| `treemap` | Parts of a total as blocks. Better than a donut for many parts. |
+| `sankey` | Amounts flowing from one group to the next, such as MRR movements. |
+| `radar` | Several measures compared as shapes. |
 
 `format` is `number`, `compact`, `bytes`, `currency`, `percent`, `date`, or `datetime`. Line and scatter charts also take `xFormat`. Line x values are dates as milliseconds, numbers, or labels. Labels give a category axis and are read by position: list every series' points in the same order. A label may repeat.
 
@@ -102,7 +126,7 @@ In `UiChart` and `UiLiveChart`, each series name toggles its line, and a dim nam
 
 `UiStaticChart` draws on the server only and sends no chart script. Use it for articles and reference pages where nobody needs hover or ranges. Static charts sit at reading width. Its file never imports the interactive chart, so a page that uses only static charts loads no chart code.
 
-Interactive charts load about 170 to 190 KB of compressed script on the pages that use them. Use a static chart unless hover, toggles, or ranges help the reader.
+Interactive charts load about 170 to 190 KB of compressed script on the pages that use them. Funnel, gauge, treemap, sankey, and radar load their extra script only on a page that draws one. Use a static chart unless hover, toggles, or ranges help the reader.
 
 ### Page weight
 
@@ -117,8 +141,8 @@ Charts with up to 60 values carry a visually hidden data table. Larger charts ge
 
 ### Add a chart type
 
-1. Register it in `app/ui/charts/echarts.ts`. Only registered types reach the browser.
-2. Add its data shape and settings in `app/ui/charts/chart-option.ts`.
+1. Register it. `app/ui/charts/echarts-more.ts` loads in the browser only for charts that need it, so most new types go there. Add the kind to `moreKinds` in `chart-option.ts`. Use `app/ui/charts/echarts.ts` only for a type most chart pages will draw.
+2. Add its data shape, option, legend, and hidden data table in `app/ui/charts/chart-option.ts`.
 3. Add a gallery example in the Charts section, and check it at desktop and mobile width in both themes.
 
 Rules for every chart setting:
@@ -128,6 +152,7 @@ Rules for every chart setting:
 - Draw SVG only. A canvas can't follow the theme.
 - Chart text uses the mono font. `echarts.ts` measures text by it, so labels never clip.
 - Keep server and browser drawings the same: fixed `en-US` formats and UTC dates.
+- Text drawn on colored shapes uses the `onShape` style, which outlines it in the page color so it reads in both themes.
 
 ## Tables
 
@@ -137,7 +162,7 @@ Content tables written in Markdown use a scrollable `TableFrame`. Keep tables re
 
 ## Steps and timelines
 
-`UiSteps` shows ordered stages and which one is done, current, or next. `UiTimeline` shows dated events. Use a timeline only when its axis is time. `UiAllocationBar` shows parts of a total and is often easier to compare than a donut.
+`UiSteps` shows ordered stages and which one is done, current, or next. `UiTimeline` shows dated events. Use a timeline only when its axis is time. `UiAllocationBar` shows parts of a total and is often easier to compare than a donut. Its `neutral` palette suits a two-part split, `accent` puts focus on one part, and `categorical` keeps three or more parts distinct. Never color parts red, yellow, or green by position, because that implies a verdict.
 
 ## Content blocks
 
diff --git a/stack127_docs/tool-catalogs.md b/stack127_docs/tool-catalogs.md
index 4d77be81..ef41bbb2 100644
--- a/stack127_docs/tool-catalogs.md
+++ b/stack127_docs/tool-catalogs.md
@@ -68,8 +68,8 @@ Each step has an owner:
 | Step | Owner |
 | --- | --- |
 | Name the primary catalog, any secondary catalogs, and a specific card art brief | Product plan |
-| Generate and register the drawing | Opus frontend step |
-| Write one card name and description, shared across catalogs | Opus writing session |
+| Generate and register the drawing | Integration worker |
+| Write one card name and description, shared across catalogs | Opus planning session, in its writing step |
 | Apply the card fields and memberships to development together | Integration worker |
 
 The integration worker runs:
diff --git a/stack127_docs/tool-interface.md b/stack127_docs/tool-interface.md
index 335dd80f..1eddd7fe 100644
--- a/stack127_docs/tool-interface.md
+++ b/stack127_docs/tool-interface.md
@@ -1,329 +1,150 @@
-# Tool interface system
+# Tool interface
 
-Use [writing-style.md](writing-style.md) for all interface wording and visual choices.
+A stack127 tool is a visual instrument, not something to read. A first-time visitor gets their answer in a few seconds, and a pro finds every option they need one click away. The result should be clear enough that people want to share it.
 
-stack127 tools should feel like focused instruments. A person should see what to enter, what to press, and what the answer means without reading a manual first.
+This doc holds the decisions and taste specific to stack127. Good general UI practice still applies, and isn't repeated here. Words follow [writing-style.md](writing-style.md). Tokens follow [design-system.md](design-system.md). Components are in [shared-ui.md](shared-ui.md).
 
-This doc is the source of truth for tool layout, control order, and shared interaction patterns. `stack127_docs/design-system.md` still owns sitewide color, type, radius, spacing, and theme rules.
+## Serve both people
 
-## Start with the task
+Most people who use a tool want one or two plain answers fast, such as "what's my number?" and "how does it compare?" A smaller group needs depth: per-period breakdowns, extra plans, different methods, edge settings. A great tool serves both. Never make the common user wade through depth, and never drop the depth a pro needs just to look simple.
 
-Before you change a tool, boil its flow down to five parts:
+- **Basic** answers the common questions with the fewest inputs most people know offhand. It's always visible.
+- **Advanced** holds the depth. It's where pros find everything they'd expect from a serious tool in this space. Research tells you what that is: what competitors offer, what forum users ask for, and what the old tool did.
+- Rebuilding or reworking a tool never removes a working capability. Move it into Advanced, or into the page content if it's reference material. Leave something out only when nobody you named would use it, and write down why.
 
-1. The question the person came to answer.
-2. The minimum input needed to answer it.
-3. The one action that produces the answer.
-4. The first result the person needs to see.
-5. Optional detail, verification, or recovery.
+Every tool's plan takes a position: who most users are and their top questions, what Basic answers, what Advanced holds and for whom, and what's left out and why. Add an input because those people need it, not because a competitor has it. Cut one only for a reason a user would agree with.
 
-The interface follows that order. Don't give intro copy, secondary settings, or implementation details more visual weight than the task.
+## Inputs
 
-## Plan before you build
-
-Every new tool and every major redesign needs a ready Interface section in `content_docs/<tool-slug>/tool-spec.md` before UI code changes. Create it with `skills/stack127/tools/stack127-tool-interface-plan/SKILL.md`.
-
-A small fix can skip updating that section only if it doesn't change the visible inputs, result regions, hierarchy, visual format, or responsive order.
-
-The interface contract must decide:
-
-- The one user question and the one lead answer.
-- Which available facts are inputs, supporting context, evidence, or left out.
-- Why each control and result region exists.
-- Which formatted facts must not repeat.
-- Whether each proposed visual shows a true relationship.
-- Behavior for real states, long values, desktop, and narrow screens.
-- Observable `UI-` acceptance criteria.
-
-In the full tool pipeline, the Opus planning session plans the interface. Later it builds the frontend itself, on top of the backend Luna builds. It doesn't add controls, result regions, explanatory sentences, or visuals outside the reviewed plan without updating the spec. The independent audit judges the rendered result without relying on the builder's explanation.
-
-## Reading order
-
-A tool page has three visual levels:
-
-| Level | Contains |
-| --- | --- |
-| Page header | Identity icon, tool name, and at most one short sentence when the name doesn't explain the job. |
-| Workbench | Required inputs, one primary action, status, and results. |
-| Supporting content | Interpretation, limits, and related checks, after the workbench. |
-
-Inside the workbench, the eye should find the main input before the main action, and the answer before supporting data. Guide the eye with position and spacing first, size and weight second, and accent last.
-
-## Cut text, keep clarity
-
-- Keep visible labels. Placeholder text is an example, never the only label.
-- Default to no helper text inside the workbench. Add it only when it prevents a likely error, explains a hidden consequence, or clarifies an unfamiliar value the label and control can't express.
-- Remove sentences that repeat a field label, button label, heading, or visible result.
-- Don't describe familiar providers, options, units, or control behavior under a field. If that's still useful, it goes in the supporting content.
-- When a field truly needs guidance, keep it short and beside the field. Don't add a paragraph above the form for it.
-- Show common choices directly. Put optional advanced or rare choices behind a clearly named disclosure.
-- Use a diagram, relationship, scale, timeline, table, or grouped result when it gets the point across faster than prose. Don't replace one sentence with decorative art.
-- Results start with the answer. Method, provider, timing, and raw data come after.
-
-Less text never means unlabeled controls, unexplained errors, hidden limits, or mystery icon-only actions.
-
-## Workbench structure
-
-The workbench is the full-width band defined in `stack127_docs/design-system.md`. Its background and top and bottom rules span the whole main column beside the sidebar. Its interactive contents line up to a calm inner measure.
-
-Use this structure when the tool allows it:
-
-```text
-required input or query
-visible common choices
-secondary settings, only when needed
-primary action   quiet secondary action
------------------------------------------
-answer
-visual or structured result
-verification and metadata
-```
-
-Don't wrap the form, action area, result, table, or visual in separate nested cards. Use alignment, space, and a single divider to group things.
-
-On wide screens, fields may share a row when they belong to one decision. Don't use columns just to fill empty width. On narrow screens, keep the task order and stack controls without shrinking their hit areas.
-
-When a select or input shares a row with its primary button, line the button up with the control itself. The label stays above the control and must not push the action out of line. On narrow screens, stack the button under the control at full width.
+- Basic inputs sit at the top of the workbench. Advanced is one `UiDisclosure` below them, closed by default, named for what's inside, such as `Cohorts and billing` or `Resolver settings`. Its closed summary says what's set, with `uiSetSummary`.
+- Mark every required field with `required`, which shows `*` beside its label. Basic inputs are usually all required and Advanced ones all optional, and the mark still goes on, because people expect it. A field that becomes required when its partner is filled gets the mark then.
+- Every Advanced input is optional. Empty means not applied, or a default the hint names, such as "Empty uses 6 × 9 in." With Advanced empty, the answer matches Basic. Don't hide a default that changes the answer without naming it.
+- When a refinement needs values together, such as a customer count and a price, ask for them together inside Advanced. Filling one makes its partner required.
+- Repeated rows, such as one row per month or per drive, belong in Advanced with `UiRepeatableList` unless most people need them. Each row stays on one line on wide screens. Remove stays in a fixed last column.
+- Every input must change the result. If it doesn't, cut it.
+- Never use a checkbox or switch to reveal more fields. Never build mode switches or tabs for Basic and Advanced.
+- No text under fields, headings, options, or buttons. When a label needs explaining, give it a `hint`: one sentence behind a small `?`.
+- Accept the real range of the domain. Don't cap an input below what real people enter. When the domain itself has a limit, such as a maximum the platform allows, the error names the limit and who sets it.
+- Units go in a suffix or a unit select. Short important choices, up to about four, show as a visible choice row, not a dropdown.
 
-## Control rules
+## Default state and the button
 
-All bounded controls use `--radius`, which is 2px. Controls use `--text-body`, the shared focus ring, and the site color tokens. Keep them compact enough for technical work, but never below a comfortable pointer target.
+Every tool opens with realistic example values filled in and their result showing, so the first thing anyone sees is a finished answer. Pick typical values, not extreme ones, so the first result and any comparison don't mislead. Mark the result `Example` until the person calculates their own.
 
-### Buttons
+One primary button, named for the result, such as `Calculate royalty` or `Look up DNS`, sits below the inputs with a quiet `Reset` beside it. The result changes only when the person presses it.
 
-| Type | Rule |
-| --- | --- |
-| Primary | One per workbench state. Accent fill. Name the result, such as `Look up DNS` or `Calculate capacity`. |
-| Secondary | Bordered surface, for useful nearby actions such as reset, copy, download, or load example. |
-| Ghost | Unboxed, for low-priority actions you can undo. |
-| Icon-only | Only for a familiar action in tight space. Needs an accessible name, and a visible tooltip when the icon could be unclear. |
-| Loading | Keeps the button width, says what's happening, and blocks double submits. |
-| Disabled | Only when the reason is obvious. Prefer an enabled submit that shows exact validation when that's clearer. |
-| Copy | Reports success only after the clipboard API or a verified fallback works. If both fail, keep the source value selectable and show one local failure state. |
+- When inputs change after a result, the old result stays but steps back (`ToolResult stale`), and a short status says `Inputs changed`. It never disappears.
+- Errors show when the person presses the button: under each field, with focus on the first one. If that field is inside Advanced, open it first.
+- A shared link opens and calculates right away. If a value in it is invalid, show the error the same way.
+- Reset returns to the example and its result.
+- Network tools, such as DNS lookups, show an example input but run only when the person presses the button, never on load.
 
-Don't give primary styling to reset, share, copy, download, or navigation actions.
+## Empty and blocked results
 
-### Text, search, and number fields
+The result region keeps its size and place in every state, so the page never jumps or turns into an empty band.
 
-- Use a persistent label, plus a realistic example when one helps.
-- Mark every required field with a visible `*`. Keep the required state in code as well.
-- Pick the right input type, input mode, autocomplete, capitalization, and spellcheck.
-- Use `UiNumberField` when whole or decimal values benefit from keyboard-safe increment and decrement buttons.
-- Join a value and its unit with `UiQuantityField` or `UiQuantityInput`. They're one decision, so they shouldn't float as separate controls.
-- Units go in the attached unit selector or a fixed suffix, not in helper paragraphs.
-- Search fields search or filter a collection. Don't call a single-value lookup field "search" just because it has a magnifying-glass icon.
-- Put errors right under the field. After submit, focus the first invalid field.
-- Show a validation or request error once, at the narrowest useful scope. Don't repeat the same message under a field, above the action, and in the result area.
-- Field validation doesn't create a result. Don't add an error result panel or a `Fix input` button when the error can show beside the field with focus moved there. Use a retry action only for a failed request or operation the person can repeat without changing the input.
-- When a field and action share a row, keep separate rows for label, control, and error. A new error must not knock the action out of line with the control.
+- **Invalid input:** the last good result stays, stepped back, while the errors point at the fields.
+- **A domain rule blocks the answer:** answer with the rule instead of going blank. If the price is below the platform's minimum, the answer is that minimum, and what you'd earn at it. If a value is past a hard limit, say the limit, who sets it, and the nearest result you can give.
+- **Nothing to show yet,** such as a network lookup before its first run: show the shape of the result with `—` in place of values, never a blank band or a paragraph of instructions.
+- **Partial results:** one bad Advanced value hides only the part of the result it feeds, never the main answer.
 
-### Selects and visible choices
+## The result
 
-- Use `UiSelect` for a fixed set of choices. It renders the stack127 trigger and listbox, and keeps a visually hidden native select for mobile and form accessibility.
-- Use `UiComboBox` only when the person benefits from typing to filter a longer list.
-- Use a compact radio or segmented row when seeing all common options helps the decision.
-- Keep real radio semantics, and one shared hit target for each label and control.
-- A selected option gets stronger contrast and the allowed accent treatment. Unselected options stay quiet.
-- Don't use a dropdown to hide two or three important choices.
+The result is personal. It shows only what the person's own inputs produced.
 
-### Checkboxes and switches
+Design it so people can scan it with a clear hierarchy. Guide the eye: the main answer is big and prominent, with its visual, where the eye lands first. Smaller numbers stay clean and readable for the people who want to dig in. Detail pros asked for in Advanced, such as a per-row table, comes after. Arrange it for this tool's answer; there is no fixed layout.
 
-- Use a checkbox for an independent choice, or a group where several items can apply.
-- Use a switch only when the change takes effect right away. A setting sent with a form is a checkbox.
-- Write labels as the state or choice, not as an instruction to click.
+Add Share, copy, or download when useful. `UiShareAction` copies a link that reopens the same inputs. For lookups and checks, put the person's raw records in a closed disclosure.
 
-### Disclosures
+Sources, published-figure tables, method notes, definitions, caveats, and advice go in the page content, never in the result. A short status word is fine when a number alone could mislead, such as `Provisional` with `15 days left`. Each result region answers a different question, so don't show a value twice.
 
-- Advanced sections say what's inside, such as `Resolver settings`, not `More options`.
-- Keep values chosen inside a collapsed disclosure visible in a short summary.
-- Never hide required fields, the primary action, an error, or the main result.
-- Never hide a default input that changes the main answer. A prefilled value is an active assumption, not permission to hide it.
-- A disclosure may hold optional refinements that do nothing when off, optional evidence, or diagnostics. If turning an option on makes another field required, show that field in the main flow next to the option.
-- During testing, change every input that drives the result and confirm the answer changes as documented. If it doesn't, remove the control or document what else it does.
+### Make it visual
 
-### Optional Basic and Advanced modes
+Pick the visual that makes this person's answer obvious. Think about the relationship you're showing: a share of a whole, a flow from one stage to the next, progress toward a goal, a ranking, a change over time, a breakdown, a position on a range. Then pick the form that shows it best.
 
-Record one control-mode decision for every tool:
+Any Apache ECharts chart type works through our chart wrapper. If the type you need isn't in the wrapper yet, add it. See Charts in [shared-ui.md](shared-ui.md). Shared result components, a custom SVG, or marker art for a concept are fine too.
 
-| Mode | Use it when |
-| --- | --- |
-| `single` | The default. Use this unless one of the others clearly fits. |
-| `disclosure` | One mode, with optional evidence or refinement tucked away. Active assumptions that drive the result stay visible. |
-| `basic-advanced` | A complete common task can run on a small, explicit set of assumptions, and a separate group of refinements would otherwise swamp it. |
+A visual must show something the numbers alone don't. A chart that repeats one number is decoration. Size a visual for reading, not to fill space. Charts are at least 260px tall.
 
-Basic and Advanced use the same engine and the same normalized input contract. Basic shows every active assumption that affects the answer, with its source and a way to edit it. Advanced shows the extra controls. A simpler screen must not mean a different calculation or a hidden default.
+### Comparisons
 
-When someone switches modes:
+Show a published comparison only when the research found data that measures the same thing, the same way: the same definition, unit, and time window. When the person's own settings differ, such as a 30-day window against a six-month benchmark, hide the comparison. When they haven't set it, show the comparison with the source's window in its visible label, such as `Median, paid within 6 months`.
 
-- Keep their values.
-- If custom Advanced values stay active in Basic, show a short customized-assumptions summary with an edit action.
-- Replacing them with Basic defaults needs an explicit reset.
-- If a hidden value becomes invalid, show its control, move focus to it, and announce the error. Never leave someone with an error they can't see or fix.
+- Show where the person sits next to the range, such as with `UiRangeMarker`. Put the source's name in a hint.
+- Never grade. No `good`, `bad`, `below typical`, scores, or red, yellow, and green that imply a verdict. Niches differ.
+- If sources disagree or measure something else, show none. Unknown beats fake precision.
 
-The interface contract must define:
+## Layout and whitespace
 
-- Labels and the mode explanation.
-- Input mapping.
-- Basic assumptions and their sources.
-- Value retention and reset.
-- Invalid-state recovery.
-- Focus and announcements.
-- URL, reload, back, and forward restoration.
+Every tool uses `ToolWorkbench`, `ToolFieldRow`, and `ToolResult` from `app/ui/tools/tool-workbench.tsx`. Don't write your own workbench band, width, or section gaps.
 
-Tests must prove that equal normalized inputs return the same result in both modes. They must cover switching in both directions with custom, invalid, and restored state.
+- The workbench is a full-width band. Its content uses the shared 66rem working width. That width is room, not a quota. Don't stretch a few results across it; leftover whitespace is fine when the result reads well.
+- Inputs first, then the action row, then the result below one divider, all on the same left edge.
+- Fields that belong to one decision share a row with `ToolFieldRow`. Unrelated fields don't share a row just to fill space. On phones every row stacks, in reading order.
+- Readability beats filling space. When labels and values squeezed into columns start wrapping, use a vertical list instead.
+- Spacing comes from the shared gaps: wider between regions, tighter inside a group. Group with space and alignment, not nested cards or extra borders.
+- A table or chart keeps its overflow inside its own frame. Nothing causes page-level overflow.
 
-Don't add modes just to make a crowded form look shorter.
+## How a stack127 tool feels
 
-### Repeated rows and add actions
+Every tool should feel made by the same hand, while its inputs and visual fit its own job:
 
-- Put `Add` beside the group heading when it creates another group. Put it after the current rows when it adds a row to that group.
-- After adding a row, focus its first useful control. After removing the focused row, return focus to a stable nearby action.
-- Keep row actions in a fixed last column. Don't let long values push remove, duplicate, or reorder actions onto a second line.
-- On narrow screens, keep row order and use a set breakpoint. Don't wait for the browser to wrap controls unpredictably.
+- The same band, working width, and spacing from `ToolWorkbench`, and the same tokens, typography, and 2px radius from [design-system.md](design-system.md). Dark by default.
+- The same pieces for the same jobs: `hint` for explanations, one `UiDisclosure` for Advanced, `UiShareAction` for links, and the chart wrapper for charts.
+- The same order: inputs, the action, then the result.
+- Accent fill only on the primary button. Result visuals use the data colors, with the first one on the person's own value and nothing competing with it.
+- Numbers in the mono font, words in the sans font, and no decoration that doesn't carry meaning.
 
-## Result hierarchy
+## Good and bad tools
 
-Results answer before they document. The order:
+These show the quality bar, not a template. Each good tool looks different because its job is different. Don't copy their layouts.
 
-1. One plain answer or status, at `--text-body` or a fitting heading size.
-2. The useful visual relationship or structured values.
-3. Raw records, calculation steps, or diagnostic detail.
-4. Provider, timing, version, and source metadata, in `--text-small`.
-5. A next action, only when it helps check or continue the task.
+**Good: an MRR goal calculator.** It opens with an example: $4,000 MRR now, a $10,000 goal, and 8% monthly growth, with the result already showing. The answer reads `12 months`, with the goal month under it. A line chart shows the MRR path rising to meet a flat goal line. Two small numbers answer the next questions: the growth needed to get there 6 months sooner, and the new MRR needed each month. Advanced, `Churn, expansion, and monthly targets`, holds what a growth lead models, including a different growth rate per quarter.
 
-Don't put every fact in an equal card. Group related facts and make the main finding stand out.
+**Good: a domain expiry check.** One field with an example domain, and `Check expiry`. Before the first run, the result shows its shape with `—`. After it, the answer reads `Expires in 43 days`, with the date. A bar runs from the registration date to the expiry date, with a marker for today. The registrar and auto-renew status sit below as two small facts. The raw RDAP response is in a closed disclosure.
 
-| Content | Use |
-| --- | --- |
-| Repeated fields | Table |
-| Exact comparisons and trends | `UiLiveChart` |
-| Conceptual relationships | Marker art |
+**Good: a RAID capacity planner.** It opens with four 8 TB drives in RAID 5 and its result. The answer reads `24 TB usable`, and a bar beside it splits the raw space into usable, parity, and reserve, with `Survives 1 drive failure` as a status. Advanced, `Mixed drives and reserve`, lets a pro list each drive's size and set a free-space reserve, and the result adds a per-drive table.
 
-Each result region answers a different question. Don't repeat a visible value in a second metric row, card, or summary unless the second view shows a needed relationship. Compare the formatted values the reader actually sees. If two source timestamps display as the same date, don't render an identical two-value comparison.
+**Bad: the form you have to read.** A sentence under every field. A checkbox that reveals five more required fields. An input most people would have to work out by hand before they get any number.
 
-Use a timeline only when its axis is time. Don't place variable, conditional, or unknown stages at equal distances on a line. Use an ordered stage list or table that names each duration and consequence.
+**Bad: the gutted tool.** It looks simple because the options pros relied on were deleted, such as mixed drive sizes in a RAID planner. Pros leave, and the page has less to say than its competitors.
 
-A repeated-field table needs enough width for its columns and real values. Put it beside another region only when both stay readable with long content. Otherwise, stack the regions on purpose. On narrow screens, a table may scroll inside its own viewport. Sibling content must never cover a column or cause page-level overflow.
+**Bad: the stretched result.** Three short results spread across the full width. A legend squeezed into three columns, so every label wraps onto two lines and the eye zigzags to find its value.
 
-When a result maps to a small fixed set of states, show one label and one value instead of a paragraph. Put the longer caveat in supporting content or an accessible description, as long as the visible value is accurate on its own.
+**Bad: the blank error.** A retention period past the provider's limit makes the whole result disappear. The person has to guess the limit, and the page jumps.
 
-## States are part of the design
+**Bad: the report in the result.** The number, then three sentences explaining it, a table of published studies, and method notes.
 
-Every tool must handle each state that can happen:
+**Bad: the dashboard.** Eight equal cards with no lead answer. A donut with one slice. A green `Good` badge based on someone else's average.
 
-- Initial.
-- Incomplete or invalid input.
-- Loading.
-- Success.
-- Empty or no match.
-- Partial result.
-- Service or network failure.
-- Retry or recovery.
-- Disabled controls.
-- Long content and narrow screens.
+## URL state
 
-Announce status changes to assistive technology. A failure names the problem and the next useful action. Don't clear valid input after a failure.
+A tool lives at one clean URL, such as `/raid-calculator`. The tool never changes the URL on its own: not on load, not after a result, and not when someone presses Share.
 
-### URL state
+Sharing is the only way state gets into a URL. `UiShareAction` copies a link with the current inputs. Opening that link restores them and calculates. A link counts as shared only when it carries the tool's own parameters. Ignore anything else, such as `utm_source`, and open on the normal example.
 
-The canonical route is the initial state, not a blank query string waiting to be filled. A clean tool URL must stay unchanged through server render and hydration. Never call `replaceState` or `pushState` on mount to write defaults, derived values, or a first result into the URL.
+Tool pages stay static, so the server page never reads `searchParams`. A small client wrapper, `<slug>-from-url.tsx`, reads a shared link with `useInitialQuery()` from `app/ui/tools/use-initial-query.ts` and renders the tool with `key={query.key}`. `dns-lookup` is the reference. See [caching.md](caching.md).
 
-The page stays static, so the server page never reads `searchParams`. A small client wrapper, `<slug>-from-url.tsx`, reads the query with `useInitialQuery()` from `app/ui/tools/use-initial-query.ts` and renders the tool with `key={query.key}`. `dns-lookup` is the reference. The first render shows the default state, then fills in from the URL. A tool that runs from a shared link starts after hydration. See `stack127_docs/caching.md`.
+## Components
 
-A tool may restore state from a query string the person opened on purpose. When shareable state helps, prefer an explicit Share action that creates or copies the URL. If a tool updates the URL as the person edits, that must be part of the documented task, and it must start only after a deliberate change by the person.
+Use the shared components in `app/ui/` and the `/components-ui` gallery. When nothing fits, build a shared component that more than one tool can use, with a gallery example. Keep tool-specific behavior in the route. Never fall back to an unstyled native control because the stack127 piece doesn't exist yet.
 
-## Shared components
-
-Prefer a small set of semantic components over visual copies inside each tool. Components keep native HTML behavior and take ordinary labels, descriptions, errors, and state props.
-
-Shared fields may take an outer placement class, so the tool can put them in an explicit grid or subgrid. Page styles may position the component, but must not replace its internal control styling.
-
-### Missing components
-
-Before naming a component, planning must check `app/ui`, `/components-ui`, and related sibling tools. For every nontrivial control or result, record one decision:
-
-- Reuse an existing shared component.
-- Add a new shared component.
-- Use a route-specific component because its behavior is unique.
-
-Then describe the component's parts, all its states, keyboard and screen-reader behavior, error and recovery behavior, responsive behavior, and design tokens.
-
-Don't fall back to an unstyled native control, a generic browser upload box, a generic dashboard pattern, or an unrelated third-party component because the stack127 piece doesn't exist yet. Keep native semantics underneath when they're useful or required. For example, a file upload can keep an accessible `input type="file"`, while a stack127 dropzone, browse action, file status, rejection, remove, and retry interface handles what people see.
-
-Build the approved component in the shared UI when its look and behavior can serve more than one page. Keep it in the route when the interaction is specific to that tool. If the missing component can't be built and checked within scope, return the decision to the main agent.
-
-The intended primitives:
-
-- `UiTextField`
-- `UiSearchField`
-- `UiTextArea`
-- `UiSelect`
-- `UiComboBox`
-- `UiDatePicker`, `UiTimeField`, and `UiDateTimePicker`. Times use 12 hours; pass `hourCycle={24}` when the tool needs 24 hours.
-- `UiNumberField`
-- `UiQuantityField`
-- `UiQuantityInput`
-- `UiSlider`
-- `UiRangeSlider`
-- `UiChoiceGroup` (one choice) and `UiMultiChoiceGroup` (several)
-- `UiCheckbox`
-- `UiSwitch`
-- `UiButton`
-- `UiActionRow`
-- `UiDisclosure`
-- `UiRepeatableList`
-- `UiStatus`
-- `UiResultLead`
-- `UiPrimaryResult`
-- `UiProgressBar`
-- `UiAllocationBar`
-- `UiMetricGroup`
-- `UiTimeline`
-- `UiKeyValueList`
-- `UiDataTable`
-- `UiRawOutput`
-- `UiCodeOutput`
-- `UiCopyAction`
-- `UiDownloadAction`
-- `UiFileDropzone`
-- `UiFileList`
-
-### Allocation color
-
-`UiAllocationBar` has three palettes:
-
-| Palette | Use it when |
-| --- | --- |
-| `neutral` | A plain two-part split. |
-| `accent` | One part needs focus against a neutral remainder. |
-| `categorical` | Three or more named parts must stay distinct. |
-
-Set explicit segment tones when a category must keep the same color across related views.
-
-Don't assign red, yellow, or green by position when they'd suggest danger, warning, or success. Color is never the only label. Keep every segment name and exact value in the legend. A zero or tiny value keeps its legend entry but gets no made-up minimum width in the bar.
-
-The canonical code lives in `app/ui/controls.tsx`, `app/ui/display.tsx`, and focused modules such as `app/ui/uploads.tsx`, with styles beside them. Read [shared-ui.md](shared-ui.md) for use across pages, and [page-content.md](page-content.md) for content blocks. `/components-ui` is the development-only gallery and returns `404` in production.
-
-Pull out a primitive when pages share its behavior and look. Don't create a component that only renames one HTML element or makes an unusual tool harder to understand.
-
-## Visual review
-
-Review the rendered tool, not just its CSS.
+## Plan before you build
 
-- At first glance, can a person point to the required input, main action, and result?
-- Is there one obvious primary action?
-- Can any sentence go because the layout already says it?
-- Are related controls grouped more tightly than unrelated ones?
-- Does the result look more important than metadata and options?
-- Do loading, error, empty, and recovery states keep the same hierarchy?
-- Does the task order hold on mobile?
-- Can you reach every table header and cell without sibling content covering it?
-- Can every action be done with a keyboard, with focus always visible?
-- Do dark and light themes both keep contrast and grouping?
-- Does the workbench span the main column while its controls stay comfortably measured?
-- Does a clean canonical URL stay unchanged after hydration?
+New tools and major redesigns need the Interface section of `content_docs/<slug>/tool-spec.md` first, from `skills/stack127/tools/stack127-tool-interface-plan/SKILL.md`. Small fixes that don't change inputs, results, or layout can skip it.
 
-Fix visible hierarchy or usability problems before polishing decoration.
+## Review
 
----
+Look at the rendered tool at desktop and mobile width, in both themes.
 
-_Internal doc. Created 2026-09-04._
+- Does it open on a realistic example with its result showing?
+- Can a first-time visitor get their answer without reading anything but labels?
+- Would a pro find what they expect in Advanced? Did any capability the research or the old tool had go missing?
+- Can someone scan the result: the main answer and its visual first, smaller numbers readable, and no label squeezed until it wraps?
+- Does every required field show `*`?
+- Does the result keep its place when inputs change, are invalid, or hit a domain limit? Does a limit answer instead of blanking?
+- Does every input change the result?
+- Is everything in the result about the person's own inputs, shown so it's obvious at a glance?
+- Is any word in the workbench more than a label, hint, option, button, value, error, or status?
+- Does the URL stay clean until someone presses Share?
+- Does it work with a keyboard, with visible focus, and without page overflow?
diff --git a/stack127_docs/tool-pipeline.md b/stack127_docs/tool-pipeline.md
index 90b9cc8b..228578cd 100644
--- a/stack127_docs/tool-pipeline.md
+++ b/stack127_docs/tool-pipeline.md
@@ -12,27 +12,35 @@ Lanes and models follow "Agent roles" in `AGENTS.md`. The main agent is the coor
 
 | Round | Work | Lane | Effort | Output |
 | --- | --- | --- | --- | --- |
-| 1 | Deep research and competitor review | Luna | `max` | `research.md` |
+| 1 | Who uses the tool, deep research, and competitor review | Luna | `max` | `research.md` |
 | 2 | Product, interface, and component plan | Opus, planning session | `medium` | New `tool-spec.md` with why people will choose it, Product with backend contract, Interface, catalog placement, card art brief, and new or improved shared components |
 | 3 | Backend build | Sol | `high`, or `xhigh` for risky logic | Engine, API routes, data scripts, development preview row, and focused correctness test. No UI. |
-| 4 | Frontend build | Opus, same planning session | `high` | Route page, interface, tool components, styles, card art, and desktop and mobile checks |
-| 5 | Content plan and writing | Opus, writing session | `medium` | Content section, title, the route's `content/*.mdx` files, interface words, SEO text, and catalog card copy |
-| 6 | Development content integration | Luna | `xhigh` | Publish manifest, integrated development page, and catalog memberships |
+| 4 | Interface build | Opus, same planning session | `high` | Tool components, styles, and every word in them |
+| 5 | Content plan and writing | Opus, same planning session | `medium` | Content section, title, the route's `content/*.mdx` files, interface words, SEO text, and catalog card copy |
+| 6 | Integration | Luna, its own session | `xhigh` | Route and content wiring, card art, publish manifest, development page, catalog memberships, and the full desktop and mobile checks |
 | 7 | Independent audit | Sol | `high` | Release verdict and defects routed to their owner |
 
-Sol builds the backend. Opus builds everything people see: the page, interface, components, styles, card art, and copy.
+Sol builds the backend. The Opus planning session plans the tool, designs and builds what people see, and writes every word. Integration connects it all and checks it.
 
 Workers don't delegate. Start each worker without unrelated conversation context.
 
 Once the Content section and copy are ready, pass the draft to integration. Don't wait for copy from the user.
 
+## Pace
+
+The homelab hardware is limited, so go slow unless the user asks for speed. Work on one tool at a time, with no more than one or two agents running at once. Take a tool through its audit before starting the next. Work that several tools share, such as one engine they all use, can be built once up front.
+
+When the user asks to go fast, tools can run in parallel, but browser checks still run one at a time.
+
 ## Sessions
 
 Each round's worker keeps its session, so follow-ups go back to the worker that did the work.
 
 `delegate_task` returns a `childThreadId`. Send follow-ups to that thread with `t3_thread_send`, wait for them with `t3_thread_wait`, then read the reply with `task_status`.
 
-Planning and frontend share one Opus session. Writing gets its own. Keep the thread IDs until the audit passes.
+Planning, interface, and writing share one Opus session. The session that plans the tool writes every word in it and on its page, so labels, hints, and content agree. That session works on one tool only, so all its attention goes to that tool's users and searchers. Never give it a second tool, and never give it integration work: route wiring, card art, publishing, and check runs make it mechanical.
+
+Research, backend, integration, and audit workers usually get one tool each too. The main agent can share one across tools when the work is small and alike. The independent audit gives the fresh read. Keep the thread IDs until the audit passes.
 
 The prompt names the skill files to follow, the tool, route, spec path, allowed files, and stop condition.
 
@@ -49,6 +57,12 @@ For each round:
 
 After planning, read the spec against the research. Check that the plan:
 
+- Takes a clear position on who most users are and their top 2 or 3 questions. Send back a spec that treats every input as equally important.
+- Answers those questions in Basic with the fewest inputs most people know offhand.
+- Keeps every Advanced field optional, and gives each one a reason and an audience.
+- Opens on realistic example values with their result, and names the button for the result.
+- Keeps the depth pros need in Advanced, and drops no capability the research or the old tool had without a reason.
+- Shows a published comparison only where the research found matching data, and never grades.
 - Answers what searchers need.
 - Beats the competitors in specific ways.
 - Names the components to use.
@@ -61,22 +75,22 @@ Route each problem to its owner:
 | --- | --- |
 | Suggestions, planning gaps, missing component work, weak product decisions | Planning session |
 | Contract gaps | Planning session |
-| Frontend, layout, interaction, and card art problems | Planning session, at high effort |
+| Design, layout, and interaction problems | Planning session, at high effort |
 | Backend defects and wrong answers | Sol |
-| Data and integration bugs | Luna |
-| Copy problems | Writing session |
+| Data, wiring, and card art bugs | Integration session |
+| Copy problems | Planning session |
 
 Sol builds the backend to the contract. If the contract has gaps, Sol reports them instead of redesigning.
 
 ### Checking the writing
 
-Send factual fixes and missing copy back to the writing session first. Then ask that session to make the full page copy easier for a general reader to follow.
+Send factual fixes and missing copy back to the planning session first. Then ask it to make the full page copy easier for a general reader to follow.
 
 The rewrite keeps every useful detail and qualification. It explains hard ideas plainly, with a short example where it helps, without dragging the page out. Check the revised draft before integration.
 
 After integration, read the rendered page from start to finish. Every sentence should make sense as public copy.
 
-Send these back to the writing session, then reintegrate and check the affected copy:
+Send these back to the planning session, then reintegrate and check the affected copy:
 
 - Stray research notes or source labels.
 - Insider wording.
@@ -101,18 +115,19 @@ If integration or audit later changes code, rerun only the checks that change af
 
 Page copy uses existing components only.
 
-Luna writes `research.md` from `skills/stack127/tools/stack127-tool-orchestrator/references/research-template.md`. It records scope, search intent, user problems, verified facts, 5 to 8 competitor reviews, a comparison table, disagreements, how stack127 can win, blockers, and sources.
+Luna writes `research.md` from `skills/stack127/tools/stack127-tool-orchestrator/references/research-template.md`. It starts with who uses the tool and the questions they bring. Then it records scope, search intent, user problems, verified facts, published comparison data, 5 to 8 competitor reviews, a comparison table, disagreements, how stack127 can win, blockers, and sources.
 
 Opus starts `tool-spec.md` from `skills/stack127/tools/stack127-tool-orchestrator/references/tool-spec-template.md`. The spec links to the research instead of copying it.
 
-In the writing session, Opus first completes the Content section. Then, in the same session, it drafts from the finished spec and the actual tool.
+After the interface, the same Opus session completes the Content section, then drafts from the finished spec and the actual tool.
 
 | Spec section | Records |
 | --- | --- |
+| People and questions | Who most users are and their top questions, what Basic answers, what Advanced holds and for whom, and what's left out and why. A position, with reasons. |
 | Why people will choose this tool | What the searcher is trying to decide, where top results fail, and what this tool does better. |
 | Product | The job, scope, technical contract, important states, and independently known examples. |
 | Product: catalogs and card art | One primary catalog and any secondary catalogs, in rank order, each with a reason based on the reader's task. One visual takeaway, focal subject, and supporting relationship for the new card's `toolSpot` marker drawing. A missing catalog is a separate catalog page task for the main agent. |
-| Interface | Controls, result order, components, states, accessibility, and responsive behavior. It names the existing shared components the frontend uses and the new or improved shared components the planner built. |
+| Interface | Basic and Advanced inputs with their hints, when the result shows, the visual result, any comparison, controls, result order, components, states, accessibility, and responsive behavior. It names the existing shared components the frontend uses and the new or improved shared components the planner built. |
 | Content | Search intent and title, reader questions and where each is answered, the intro, usage, and content outline, facts and limits, and next steps. |
 
 Keep the spec short. Add detail only when it changes the product or prevents a wrong answer. Don't create IDs, fingerprints, duplicate contracts, or status machinery.
@@ -124,9 +139,10 @@ Keep the spec short. Add detail only when it changes the product or prevents a w
 | Calculation, parser, and resolution logic | A small focused unit test with independent examples. |
 | Planner | Each new or changed shared component in the `/components-ui` gallery and on the page types that already use it, at desktop and mobile width in both themes. |
 | Backend | One focused test, plus a direct check of one correct and one invalid example. |
-| Frontend | The actual page at desktop and mobile width in both themes, with one correct and one invalid example. |
+| Interface | The planning session looks at the real page at desktop and mobile width as a first-time visitor. |
+| Integration | The actual page and its catalogs at desktop and mobile width in both themes, with one correct and one invalid example. |
 
-The frontend step also makes the card art. It uses `$marker-art-draw` to create a spec-backed `toolSpot`, generates its SVG and TypeScript export, and registers a tool-specific key in `lib/card-art.ts` before the main build. The drawing must be recognizable at card size. A generic icon isn't finished art for a new tool.
+Integration also makes the card art. It uses `$marker-art-draw` to create a spec-backed `toolSpot`, generates its SVG and TypeScript export, and registers a tool-specific key in `lib/card-art.ts` before the main build. The drawing must be recognizable at card size. A generic icon isn't finished art for a new tool.
 
 When the in-app browser isn't available over SSH, use the local headless browser in `skills/stack127/references/homelab-browser-and-search.md`. That applies to these checks and the later audit.
 
@@ -148,10 +164,25 @@ Content fixes after integration edit the MDX files. Title, search text, and card
 
 The auditor checks accuracy, content, catalog cards and placement, and the common user flow. That includes whether the new tool's marker drawing reads clearly at its rendered size in both themes.
 
-The auditor reports each defect with its owner: backend, data, frontend, or copy. The main agent sends each one to Sol, Luna, the planning session, or the writing session, then reruns only the affected checks.
+The auditor reports each defect with its owner: backend, data, wiring, design, or copy. The main agent sends each one to Sol, the integration session, or the planning session, then reruns only the affected checks.
 
 Don't run a full-site browser suite for one tool.
 
+## Rework an existing tool
+
+Use this path when a live tool breaks the rules in [tool-interface.md](tool-interface.md), such as too many required inputs, text under fields, checkbox reveals, or sources in the result. The engine's math stays right. What changes is who the tool serves first and how it shows the answer.
+
+| Round | Work | Lane | Output |
+| --- | --- | --- | --- |
+| 1 | Add "Who uses it" and "Published comparison data" to the existing `research.md`. Don't redo the rest. | Luna, `xhigh` | Updated `research.md` |
+| 2 | Rewrite People and questions, then the Interface section. List the engine changes needed, such as making a required field optional. | Opus planning session, `medium` | Updated `tool-spec.md` |
+| 3 | Engine changes and their focused test, only if round 2 needs any. | Sol, `high` | Engine and test |
+| 4 | Rebuild the interface with `$stack127-tool-frontend`. | Opus planning session, `high` | Tool component and styles |
+| 5 | Update the page content with `$stack127-tool-writing`. Move anything cut from the tool into it. Put the published figures and sources in the article. | Opus planning session, `medium` | Updated `content/*.mdx` and interface words |
+| 6 | Independent audit. | Sol, `high` | Release verdict |
+
+A rework changes inputs and results, so it's a minor `tool_version` increase. Delete older planning docs in `content_docs/<slug>/` that the new spec replaces, such as `brief.md` or `interface-contract.md`. Work through the list one tool at a time, as "Pace" describes. Give each tool its own Opus planning session, and sync with main before you start.
+
 ## Publication and release
 
 You can publish a development preview inside an authorized tool pipeline, so the real database-backed route can be reviewed. Memberships can be set up before publication. Catalog cards appear only for published tools.
diff --git a/stack127_docs/writing-style.md b/stack127_docs/writing-style.md
index 8f36ffe3..d0a4ea0a 100644
--- a/stack127_docs/writing-style.md
+++ b/stack127_docs/writing-style.md
@@ -1,6 +1,8 @@
 # Writing on stack127
 
-Write like you're helping one person next to you. Plain words, short sentences, no filler. Anyone should get it on the first read.
+Talk like a friend explaining something to another friend, whatever the situation. Don't overcomplicate it. Keep it simple enough that your friend gets it on the first read. Let it move the way talking does, one thought leading to the next. A short line that just talks to the reader is fine now and then, but never fluff up the page. Stay on the topic, and keep the writing direct and short.
+
+Conversational, but not chatty. Talk to the reader in full sentences, with accurate facts. No jokes, no hype, no filler. Engaging doesn't mean longer; most pages should get shorter.
 
 This guide covers how to write, which format to use, and search wording, for every page, doc, and chat. Where page content lives, and how to write each block in MDX, is in [page-content.md](page-content.md). Components are in [shared-ui.md](shared-ui.md). What goes on a tool page lives in `skills/stack127/tools/stack127-tool-writing/SKILL.md`.
 
@@ -40,7 +42,8 @@ Don't repeat a visual's values in the text. A caption gives the takeaway. Alt te
 
 | Instead of | Write |
 | --- | --- |
-| This calculator enables users to leverage accurate royalty estimations. | Enter your price and page count to see what you earn per sale. |
+| This calculator enables users to leverage accurate royalty estimations. | Amazon takes its cut and the printing cost before you see a cent. Put in your price and page count to see what's left for you. |
+| **Trials started:** the number of users who began a free trial. | Start with how many people began a trial in the month you're checking. Then add how many of them paid. |
 | It is important to note that results may vary. | Results are estimates. Amazon's printing cost can change. |
 | Net revenue retention is a crucial metric in today's SaaS landscape. | Net revenue retention shows how much revenue you keep from existing customers. |
 | Whether you're a beginner or an expert, this tool has you covered. | (Cut it.) |
@@ -73,9 +76,19 @@ Write for the person searching. If they finish their task and don't go back to s
 - No clickbait, keyword stuffing, or padding.
 - Link when it helps the reader check a claim or take the next step. Link related stack127 pages where they're the natural next step.
 
+## Words inside a tool
+
+A tool is something people use, not something they read. The only words inside it are labels, hints, option names, button names, values, errors, and short status words. Everything else goes in the page content.
+
+- Labels use the words people use, like `Trials started`, not `Trial starts in cohort`.
+- A hint is one plain sentence, ideally under 12 words. It says what the input means or where to find the number. Example: `Everyone who started a trial in the same month.`
+- No sentences under fields, headings, options, cards, or buttons.
+- Result labels name the value. Don't explain the result in sentences.
+- Never call a result good or bad. Show it next to a published range when one fits. See [tool-interface.md](tool-interface.md).
+
 ## Clean wording
 
 - `stack127` in lowercase. Sentence case headings. Product names as their owners write them.
-- Straight quotes. No em or en dashes. Ranges use "to".
+- Straight quotes. No em or en dashes in sentences. Ranges use "to". A lone `—` is fine in a tool as the mark for a value it can't calculate yet.
 - No emojis, decorative labels, or extra bold.
 - Buttons name the action, like `Check domain age`.
diff --git a/tests/pages/free-trial-conversion-calculator/free-trial-conversion-calculator.test.mjs b/tests/pages/free-trial-conversion-calculator/free-trial-conversion-calculator.test.mjs
index fc3747ea..5f0f06c7 100644
--- a/tests/pages/free-trial-conversion-calculator/free-trial-conversion-calculator.test.mjs
+++ b/tests/pages/free-trial-conversion-calculator/free-trial-conversion-calculator.test.mjs
@@ -1,218 +1,308 @@
 import assert from "node:assert/strict";
 import test from "node:test";
-import { calculateFreeTrialConversion } from "../../../lib/free-trial-conversion-calculator/engine.ts";
+import {
+  FREE_TRIAL_EXAMPLE_INPUT,
+  TRIAL_MAX_COHORTS,
+  TRIAL_TYPES,
+  calculateFreeTrialConversion,
+  freeTrialInputFromQuery,
+  freeTrialShareParams,
+} from "../../../lib/free-trial-conversion-calculator/engine.ts";
 
-const cohort = (overrides = {}) => ({ label: "", starts: "1180", paid: "156", ageDays: "45", ...overrides });
-const input = (overrides = {}) => ({
-  model: "trialNoCard", windowDays: "30", cohorts: [cohort()], includeMrr: false,
-  currency: "USD", mrrMethod: "average", averageMonthly: "49",
-  monthlyCustomers: "", monthlyPrice: "", annualCustomers: "", annualPrice: "", ...overrides,
-});
+function input(overrides = {}) {
+  return { ...FREE_TRIAL_EXAMPLE_INPUT, cohorts: [], ...overrides };
+}
 function valid(overrides = {}) {
   const result = calculateFreeTrialConversion(input(overrides));
   assert.equal(result.status, "valid", JSON.stringify(result.errors));
+  return result;
+}
+function clean(overrides = {}) {
+  const result = valid(overrides);
   assert.deepEqual(result.errors, {});
   return result.values;
 }
-function invalid(overrides, field, message) {
-  const result = calculateFreeTrialConversion(input(overrides));
-  assert.equal(result.status, "invalid");
-  assert.equal(result.values, null);
-  assert.equal(result.errors[field], message);
+function row(name, starts, paid, ageDays = "", id = "row") {
+  return { id, name, starts, paid, ageDays };
+}
+function read(params) {
+  return freeTrialInputFromQuery(key => params[key] ?? "");
 }
 
-test("one completed cohort returns its exact rate and optional new MRR", () => {
-  const values = valid();
-  assert.equal(values.windowDays, 30n);
-  assert.deepEqual(values.cohorts[0], {
-    index: 0, label: "", starts: 1180n, paid: 156n, notPaid: 1024n, ageDays: 45n,
-    rate: { kind: "finite", hundredths: 1322n, exact: { numerator: 780n, denominator: 59n }, isRounded: true, roundedToZero: false },
-    maturity: { status: "complete" },
-  });
-  assert.deepEqual(values.combined, {
-    basis: "complete", status: "complete", includedIndexes: [0], excludedMaturing: 0,
-    starts: 1180n, paid: 156n, notPaid: 1024n, rate: values.cohorts[0].rate,
-  });
-  assert.equal(values.newMrr, null);
-  assert.deepEqual(valid({ includeMrr: true }).newMrr, {
-    currency: "USD", method: "average", paidCustomers: 156n, averageMonthlyCents: 4900n,
-    monthlyPlan: null, annualPlan: null, mrrCents: 764400n, mrrIsRounded: false, runRateArrCents: 9172800n,
+test("opens with the specified example and exact rate", () => {
+  const values = clean();
+  assert.deepEqual(values.rate, {
+    kind: "rate", hundredths: 800n, exact: { numerator: 8n, denominator: 1n },
+    isRounded: false, roundedToZero: false,
   });
+  assert.equal(values.notPaid, 460n);
+  assert.equal(values.trialsPerPaidTenths, 125n);
+  assert.deepEqual(values.likely, { lowHundredths: 592n, highHundredths: 1072n });
+  assert.deepEqual(values.maturity, { status: "unknown" });
+  for (const key of ["windowDays", "activation", "revenue", "target", "cohorts"]) assert.equal(values[key], null);
+  for (const trialType of TRIAL_TYPES) assert.equal(clean({ trialType }).trialType, trialType);
 });
 
-test("cohort age determines maturity, including the exact window boundary", () => {
-  const complete = valid({ cohorts: [cohort({ starts: "100", paid: "20", ageDays: "30" })] });
-  assert.equal(complete.combined.rate.hundredths, 2000n);
-  assert.deepEqual(complete.cohorts[0].maturity, { status: "complete" });
-  const maturing = valid({ windowDays: "14", cohorts: [cohort({ starts: "200", paid: "30", ageDays: "10" })] });
-  assert.equal(maturing.cohorts[0].rate.hundredths, 1500n);
-  assert.deepEqual(maturing.cohorts[0].maturity, { status: "maturing", daysLeft: 4n });
-  assert.equal(maturing.combined.basis, "all");
-  assert.equal(maturing.combined.status, "provisional");
-});
-
-test("combined rate divides complete-cohort totals, while MRR includes all paid customers", () => {
-  const values = valid({ includeMrr: true, averageMonthly: "20", cohorts: [
-    cohort({ label: " Jul ", starts: "400", paid: "60", ageDays: "75" }),
-    cohort({ label: "Aug", starts: "500", paid: "70", ageDays: "45" }),
-    cohort({ label: "Sep", starts: "450", paid: "30", ageDays: "10" }),
-  ] });
-  assert.deepEqual(values.cohorts.map(row => row.rate.hundredths), [1500n, 1400n, 667n]);
-  assert.equal(values.cohorts[0].label, "Jul");
-  assert.deepEqual(values.cohorts[2].maturity, { status: "maturing", daysLeft: 20n });
-  assert.deepEqual(values.combined, {
-    basis: "complete", status: "complete", includedIndexes: [0, 1], excludedMaturing: 1,
-    starts: 900n, paid: 130n, notPaid: 770n,
-    rate: { kind: "finite", hundredths: 1444n, exact: { numerator: 130n, denominator: 9n }, isRounded: true, roundedToZero: false },
-  });
-  assert.equal(values.newMrr.paidCustomers, 160n);
-  assert.equal(values.newMrr.mrrCents, 320000n);
-});
-
-test("all cohorts are used provisionally when complete cohorts have no starts", () => {
-  const maturing = valid({ cohorts: [
-    cohort({ starts: "100", paid: "5", ageDays: "5" }),
-    cohort({ starts: "200", paid: "10", ageDays: "12" }),
-  ] });
-  assert.deepEqual(maturing.cohorts.map(row => row.rate.hundredths), [500n, 500n]);
-  // The spec's 1500n disagrees with its formula: 15 / 300 * 100 = 5%, or 500n.
-  assert.equal(maturing.combined.rate.hundredths, 500n);
-  assert.equal(maturing.combined.basis, "all");
-  assert.equal(maturing.combined.status, "provisional");
-  assert.deepEqual(maturing.combined.includedIndexes, [0, 1]);
-  assert.equal(maturing.combined.excludedMaturing, 0);
-  const emptyComplete = valid({ cohorts: [
-    cohort({ starts: "0", paid: "0", ageDays: "40" }),
-    cohort({ starts: "100", paid: "10", ageDays: "5" }),
-  ] });
-  assert.deepEqual(emptyComplete.cohorts[0].rate, { kind: "notAvailable", reason: "noStarts" });
-  assert.equal(emptyComplete.combined.basis, "all");
-  assert.equal(emptyComplete.combined.status, "provisional");
-  assert.equal(emptyComplete.combined.rate.hundredths, 1000n);
-});
-
-test("zero starts, exact percentages, and tiny rounded rates remain distinct", () => {
-  const zero = valid({ cohorts: [cohort({ starts: "0", paid: "0", ageDays: "40" })] });
-  assert.deepEqual(zero.combined.rate, { kind: "notAvailable", reason: "noStarts" });
-  assert.equal(zero.combined.basis, "all");
-  assert.equal(zero.combined.status, "complete");
-  const maturingZero = valid({ cohorts: [cohort({ starts: "0", paid: "0", ageDays: "0" })] });
-  assert.equal(maturingZero.combined.status, "provisional");
-  for (const [starts, paid, hundredths, isRounded, roundedToZero] of [
-    ["3", "1", 3333n, true, false], ["3", "2", 6667n, true, false],
-    ["1", "1", 10000n, false, false], ["2000000", "1", 0n, true, true],
-    ["100", "0", 0n, false, false], ["20000", "1", 1n, true, false],
-  ]) {
-    const rate = valid({ cohorts: [cohort({ starts, paid })] }).combined.rate;
-    assert.equal(rate.hundredths, hundredths);
-    assert.equal(rate.isRounded, isRounded);
-    assert.equal(rate.roundedToZero, roundedToZero);
+test("matches independently known rates, Wilson bounds, and trials per paid account", () => {
+  const examples = [
+    ["160", "3", 188n, 63n, 537n, 533n, true, false],
+    ["42", "30", 7143n, 5643n, 8284n, 14n, true, false],
+    ["1180", "156", 1322n, 1140n, 1528n, 76n, true, false],
+    ["50", "0", 0n, 0n, 714n, null, false, false],
+    ["50", "50", 10000n, 9286n, 10000n, 10n, false, false],
+    ["2000000", "1", 0n, 0n, 1n, 20000000n, true, true],
+  ];
+  for (const [starts, paid, hundredths, low, high, tenths, isRounded, roundedToZero] of examples) {
+    const values = clean({ starts, paid });
+    assert.equal(values.rate.hundredths, hundredths, `${paid}/${starts}`);
+    assert.equal(values.rate.isRounded, isRounded);
+    assert.equal(values.rate.roundedToZero, roundedToZero);
+    assert.deepEqual(values.likely, { lowHundredths: low, highHundredths: high }, `${paid}/${starts}`);
+    assert.equal(values.trialsPerPaidTenths, tenths);
   }
 });
 
-test("annual MRR rounds once and ARR uses the exact monthly amount", () => {
-  const mrr = valid({ includeMrr: true, mrrMethod: "split", averageMonthly: "garbage",
-    cohorts: [cohort({ starts: "4", paid: "4" })],
-    monthlyCustomers: "3", monthlyPrice: "10", annualCustomers: "1", annualPrice: "100",
-  }).newMrr;
-  assert.deepEqual(mrr, {
-    currency: "USD", method: "split", paidCustomers: 4n, averageMonthlyCents: null,
-    monthlyPlan: { customers: 3n, priceCents: 1000n, mrrCents: 3000n },
-    annualPlan: { customers: 1n, annualPriceCents: 10000n, mrrCents: 833n, isRounded: true },
-    mrrCents: 3833n, mrrIsRounded: true, runRateArrCents: 46000n,
-  });
-  assert.equal(valid({ includeMrr: true, cohorts: [cohort({ paid: "0" })] }).newMrr.mrrCents, 0n);
-  const zeroSplit = valid({ includeMrr: true, mrrMethod: "split", cohorts: [cohort({ starts: "0", paid: "0" })],
-    monthlyCustomers: "0", monthlyPrice: "0", annualCustomers: "0", annualPrice: "0",
-  }).newMrr;
-  assert.equal(zeroSplit.mrrCents, 0n);
-  assert.equal(zeroSplit.mrrIsRounded, false);
-});
-
-test("all models share the math and maximum amounts use bigint without overflow", () => {
-  for (const model of ["trialNoCard", "trialCardRequired", "freemium"]) {
-    const values = valid({ model, windowDays: "180", cohorts: [cohort({ starts: "5000", paid: "150", ageDays: "200" })] });
-    assert.equal(values.model, model);
-    assert.equal(values.combined.rate.hundredths, 300n);
-    assert.equal(values.combined.status, "complete");
+test("zero starts has no rate or interval and never divides by zero", () => {
+  const values = clean({ starts: "0", paid: "0", activated: "0", monthlyPrice: "29", targetRate: "10" });
+  assert.deepEqual(values.rate, { kind: "none" });
+  assert.equal(values.likely, null);
+  assert.equal(values.notPaid, 0n);
+  assert.equal(values.trialsPerPaidTenths, null);
+  assert.deepEqual(values.activation.activationRate, { kind: "none" });
+  assert.deepEqual(values.activation.activatedToPaid, { kind: "none" });
+  assert.equal(values.revenue.mrrCents, 0n);
+  assert.equal(values.target.extraMrrCents, 0n);
+});
+
+test("maturity is complete at the window boundary and otherwise provisional or unknown", () => {
+  for (const ageDays of ["30", "45"]) assert.deepEqual(clean({ windowDays: "30", ageDays }).maturity, { status: "complete" });
+  assert.deepEqual(clean({ windowDays: "30", ageDays: "12" }).maturity, { status: "provisional", daysLeft: 18n });
+  assert.deepEqual(clean({ windowDays: "30", ageDays: "0" }).maturity, { status: "provisional", daysLeft: 30n });
+  const windowOnly = clean({ windowDays: "30" });
+  assert.equal(windowOnly.windowDays, 30n);
+  assert.deepEqual(windowOnly.maturity, { status: "unknown" });
+  assert.deepEqual(clean({ windowDays: "730", ageDays: "3650" }).maturity, { status: "complete" });
+});
+
+test("activation uses nested counts and preserves a zero denominator", () => {
+  const activation = clean({ activated: "200" }).activation;
+  assert.equal(activation.activated, 200n);
+  assert.equal(activation.activationRate.hundredths, 4000n);
+  assert.equal(activation.activatedToPaid.hundredths, 2000n);
+  const zero = clean({ paid: "0", activated: "0" }).activation;
+  assert.equal(zero.activationRate.hundredths, 0n);
+  assert.deepEqual(zero.activatedToPaid, { kind: "none" });
+});
+
+test("revenue calculates monthly, annual, and mixed plans without rounding MRR before ARR", () => {
+  const cases = [
+    [{ monthlyPrice: "29" }, 40n, 0n, 116000n, false, 1392000n],
+    [{ annualPrice: "290" }, 0n, 40n, 96667n, true, 1160000n],
+    [{ monthlyPrice: "29", annualPrice: "290", annualAccounts: "10" }, 30n, 10n, 111167n, true, 1334000n],
+  ];
+  for (const [fields, monthlyAccounts, annualAccounts, mrrCents, mrrIsRounded, arrRunRateCents] of cases) {
+    assert.deepEqual(clean(fields).revenue, { currency: "USD", monthlyAccounts, annualAccounts, mrrCents, mrrIsRounded, arrRunRateCents });
+  }
+  for (const currency of ["USD", "EUR", "GBP", "INR", "CAD", "AUD", ""]) {
+    assert.equal(clean({ monthlyPrice: "0", currency }).revenue.currency, currency || "USD");
   }
-  const maximum = valid({ windowDays: "730", includeMrr: true, averageMonthly: "1000000000",
-    cohorts: [cohort({ starts: "10000000", paid: "10000000", ageDays: "3650" })],
+  assert.equal(clean({ paid: "1", annualPrice: "0.06" }).revenue.mrrCents, 1n);
+  assert.equal(clean({ monthlyPrice: "0", annualPrice: "0", annualAccounts: "40" }).revenue.mrrCents, 0n);
+});
+
+test("targets round required paid accounts up, avoid negative extras, and use exact revenue per account", () => {
+  assert.deepEqual(clean({ targetRate: "10" }).target, { hundredths: 1000n, paidAtTarget: 50n, extraPaid: 10n, extraMrrCents: null });
+  assert.equal(clean({ targetRate: "10", monthlyPrice: "29" }).target.extraMrrCents, 29000n);
+  assert.equal(clean({ targetRate: "10", monthlyPrice: "29", annualPrice: "290", annualAccounts: "10" }).target.extraMrrCents, 27792n);
+  const fractional = clean({ starts: "333", paid: "20", targetRate: "7.5" }).target;
+  assert.equal(fractional.paidAtTarget, 25n);
+  assert.equal(fractional.extraPaid, 5n);
+  for (const targetRate of ["5", "8"]) assert.equal(clean({ targetRate }).target.extraPaid, 0n);
+  assert.equal(clean({ paid: "0", targetRate: "10", monthlyPrice: "29" }).target.extraMrrCents, 145000n);
+  assert.equal(clean({ paid: "0", targetRate: "10", annualPrice: "290" }).target.extraMrrCents, 120833n);
+  assert.equal(clean({ paid: "0", targetRate: "10", monthlyPrice: "29", annualPrice: "290", annualAccounts: "0" }).target.extraMrrCents, 145000n);
+  assert.equal(clean({ starts: "10000", paid: "0", targetRate: "0.01" }).target.extraPaid, 1n);
+});
+
+test("99 starts and 9 paid need one extra paid account to reach a 10% target", () => {
+  const fields = { starts: "99", paid: "9", targetRate: "10" };
+  assert.deepEqual(clean(fields).target, {
+    hundredths: 1000n, paidAtTarget: 10n, extraPaid: 1n, extraMrrCents: null,
   });
-  assert.equal(maximum.combined.rate.hundredths, 10000n);
-  assert.equal(maximum.newMrr.mrrCents, 1000000000000000000n);
-  assert.equal(maximum.newMrr.runRateArrCents, 12000000000000000000n);
-  const twelve = valid({ cohorts: Array.from({ length: 12 }, () => cohort()) });
-  assert.equal(twelve.cohorts.length, 12);
-  assert.equal(twelve.combined.starts, 14160n);
-});
-
-test("counts reject negatives, fractions, decorated numbers, blanks, and impossible paid totals", () => {
-  for (const [raw, message] of [
-    ["-5", "Counts can't be negative."], ["", "Enter a count. Use 0 if there were none."],
-    ["2.5", "Use a whole number with no commas or decimals."], ["1,180", "Use a whole number with no commas or decimals."],
-    ["1e3", "Use a whole number with no commas or decimals."], ["+1", "Use a whole number with no commas or decimals."],
-    ["1 0", "Use a whole number with no commas or decimals."], ["10000001", "Enter a number up to 10,000,000."],
-  ]) {
-    for (const field of ["starts", "paid"]) invalid({ cohorts: [cohort({ [field]: raw })] }, `cohorts.0.${field}`, message);
+  assert.equal(clean({ ...fields, monthlyPrice: "29" }).target.extraMrrCents, 2900n);
+  assert.equal(clean({ ...fields, annualPrice: "290" }).target.extraMrrCents, 2417n);
+});
+
+test("large money totals stay exact beyond the safe integer range", () => {
+  const values = clean({ starts: "10000000", paid: "10000000", monthlyPrice: "1000000000", targetRate: "100" });
+  assert.equal(values.rate.hundredths, 10000n);
+  assert.equal(values.revenue.mrrCents, 1000000000000000000n);
+  assert.equal(values.revenue.arrRunRateCents, 12000000000000000000n);
+  assert.equal(values.target.extraPaid, 0n);
+});
+
+test("cohorts combine counts and leave provisional cohorts out when settled starts exist", () => {
+  const cohorts = clean({ windowDays: "30", ageDays: "45", cohorts: [row("Jul", "400", "36", "75"), row("Sep", "450", "18", "10")] }).cohorts;
+  assert.deepEqual(cohorts.rows.map(r => [r.inputIndex, r.name, r.rate.hundredths, r.maturity]), [
+    [null, "This cohort", 800n, { status: "complete" }],
+    [0, "Jul", 900n, { status: "complete" }],
+    [1, "Sep", 400n, { status: "provisional", daysLeft: 20n }],
+  ]);
+  assert.equal(cohorts.combined.basis, "settled");
+  assert.equal(cohorts.combined.status, "complete");
+  assert.equal(cohorts.combined.leftOut, 1);
+  assert.equal(cohorts.combined.starts, 900n);
+  assert.equal(cohorts.combined.paid, 76n);
+  assert.equal(cohorts.combined.rate.hundredths, 844n);
+});
+
+test("all provisional cohorts combine when none is settled", () => {
+  const combined = clean({ windowDays: "30", ageDays: "5", cohorts: [row("Aug", "300", "17", "8")] }).cohorts.combined;
+  assert.equal(combined.basis, "all");
+  assert.equal(combined.status, "provisional");
+  assert.equal(combined.leftOut, 0);
+  assert.equal(combined.starts, 800n);
+  assert.equal(combined.paid, 57n);
+  assert.equal(combined.rate.hundredths, 713n);
+  const zeroSettled = clean({ starts: "0", paid: "0", windowDays: "30", ageDays: "30", cohorts: [row("Aug", "300", "17", "8")] }).cohorts.combined;
+  assert.equal(zeroSettled.basis, "all");
+  assert.equal(zeroSettled.starts, 300n);
+});
+
+test("unknown maturity counts as settled and row positions survive blank rows", () => {
+  const cohorts = clean({ cohorts: [row("", "300", "17")] }).cohorts;
+  assert.equal(cohorts.rows[1].name, "Cohort 2");
+  assert.equal(cohorts.rows[1].rate.hundredths, 567n);
+  assert.equal(cohorts.combined.basis, "settled");
+  assert.equal(cohorts.combined.status, "unknown");
+  assert.equal(cohorts.combined.rate.hundredths, 713n);
+  assert.equal(clean({ cohorts: [row("", "", "")] }).cohorts, null);
+  const withBlank = clean({ cohorts: [row(" ", " ", " ", " "), row(" ", "100", "10")] }).cohorts;
+  assert.equal(withBlank.rows[1].inputIndex, 1);
+  assert.equal(withBlank.rows[1].name, "Cohort 3");
+  const zero = clean({ starts: "0", paid: "0", cohorts: [row("Empty", "0", "0")] }).cohorts.combined;
+  assert.equal(zero.basis, "all");
+  assert.deepEqual(zero.rate, { kind: "none" });
+});
+
+test("basic errors invalidate the calculation and collect Advanced errors in the same call", () => {
+  for (const [starts, paid] of [["100", "120"], ["0", "1"]]) {
+    const result = calculateFreeTrialConversion(input({ starts, paid }));
+    assert.equal(result.status, "invalid");
+    assert.equal(result.values, null);
+    assert.ok(result.errors.paid);
   }
-  for (const [starts, paid] of [["100", "101"], ["0", "1"]]) {
-    invalid({ cohorts: [cohort({ starts, paid })] }, "cohorts.0.paid", "Paid can't be more than starts. Count only accounts from this cohort.");
+  const result = calculateFreeTrialConversion(input({ trialType: "other", starts: "-5", paid: "", activated: "2.5", monthlyPrice: "$29", targetRate: "0", cohorts: [row("Bad", "100", "120")] }));
+  assert.equal(result.status, "invalid");
+  for (const key of ["trialType", "starts", "paid", "activated", "monthlyPrice", "targetRate", "cohorts.0.paid"]) assert.ok(result.errors[key], key);
+});
+
+test("strict count parsing accepts outer spaces and rejects malformed or excessive counts", () => {
+  assert.equal(clean({ starts: " 00500 ", paid: " 040 " }).rate.hundredths, 800n);
+  for (const starts of ["", " ", "-5", "+5", "2.5", "1,180", "1e3", "1 000", "10000001", "9".repeat(1000), 500, null]) {
+    const result = calculateFreeTrialConversion(input({ starts }));
+    assert.equal(result.status, "invalid", String(starts));
+    assert.ok(result.errors.starts);
   }
+  assert.match(calculateFreeTrialConversion(input({ starts: "-5" })).errors.starts, /negative/);
+  assert.match(valid({ annualAccounts: "-1" }).errors.annualAccounts, /negative/);
+});
+
+test("Advanced errors hide only their dependent values", () => {
+  const fields = { windowDays: "30", ageDays: "45", activated: "200", monthlyPrice: "29", targetRate: "10", cohorts: [row("Jul", "400", "36", "75")] };
+  const activation = valid({ ...fields, activated: "30" });
+  assert.equal(activation.values.activation, null);
+  assert.ok(activation.errors.activated);
+  assert.equal(activation.values.revenue.mrrCents, 116000n);
+  assert.ok(activation.values.cohorts);
+  const revenue = valid({ ...fields, monthlyPrice: "$29" });
+  assert.equal(revenue.values.revenue, null);
+  assert.equal(revenue.values.target.extraMrrCents, null);
+  assert.equal(revenue.values.target.extraPaid, 10n);
+  assert.ok(revenue.values.activation);
+  const target = valid({ ...fields, targetRate: "0" });
+  assert.equal(target.values.target, null);
+  assert.ok(target.values.revenue);
+  const cohorts = valid({ ...fields, cohorts: [row("Sep", "100", "120")] });
+  assert.equal(cohorts.values.cohorts, null);
+  assert.ok(cohorts.errors["cohorts.0.paid"]);
+  assert.equal(cohorts.values.rate.hundredths, 800n);
+  const window = valid({ ...fields, windowDays: "0" });
+  assert.deepEqual(window.values.maturity, { status: "unknown" });
+  assert.ok(window.values.cohorts.rows.every(r => r.maturity.status === "unknown"));
+  assert.ok(window.values.revenue);
 });
 
-test("window, age, label, cohort limits, and model return their field errors", () => {
-  for (const raw of ["0", "731", "2.5", "-1", "1e2"]) invalid({ windowDays: raw }, "windowDays", "Enter whole days from 1 to 730.");
-  invalid({ windowDays: "" }, "windowDays", "Enter the follow-up window in days.");
-  for (const raw of ["-1", "3651", "0.5"]) invalid({ cohorts: [cohort({ ageDays: raw })] }, "cohorts.0.ageDays", "Enter whole days from 0 to 3,650.");
-  invalid({ cohorts: [cohort({ ageDays: "" })] }, "cohorts.0.ageDays", "Enter the days since this cohort's last start.");
-  for (const label of ["x".repeat(41), "name\n", "\tname", "a\u007fb", "a\u0085b"]) {
-    invalid({ cohorts: [cohort({ label })] }, "cohorts.0.label", "Use a name up to 40 characters on one line.");
+test("validates days, activation, targets, currency, money, and annual-plan counts", () => {
+  const cases = [
+    [{ ageDays: "20" }, "windowDays"],
+    [{ cohorts: [row("Sep", "100", "12", "20")] }, "windowDays"],
+    ...["-1", "731", "1.5", "1e2"].map(windowDays => [{ windowDays }, "windowDays"]),
+    ...["-1", "3651", "2.5"].map(ageDays => [{ windowDays: "30", ageDays }, "ageDays"]),
+    ...["30", "501", "-1", "10000001"].map(activated => [{ activated }, "activated"]),
+    ...["0", "101", "abc", "0.001", "1%", "+1"].map(targetRate => [{ targetRate }, "targetRate"]),
+    [{ currency: "JPY", monthlyPrice: "29" }, "currency"],
+    ...["$29", "-1", "+1", "1,000", "1e3", "1 000", "1.234", "1000000000.01"].map(monthlyPrice => [{ monthlyPrice }, "monthlyPrice"]),
+    [{ annualPrice: "1000000000.01" }, "annualPrice"],
+    [{ monthlyPrice: "29", annualAccounts: "5" }, "annualAccounts"],
+    [{ annualPrice: "290", annualAccounts: "0" }, "annualAccounts"],
+    [{ annualAccounts: "0" }, "annualAccounts"],
+    [{ monthlyPrice: "29", annualPrice: "290" }, "annualAccounts"],
+    [{ monthlyPrice: "29", annualPrice: "290", annualAccounts: "41" }, "annualAccounts"],
+    [{ monthlyPrice: "29", annualPrice: "290", annualAccounts: "-1" }, "annualAccounts"],
+  ];
+  for (const [fields, key] of cases) {
+    const result = valid(fields);
+    assert.ok(result.errors[key], JSON.stringify(fields));
+    assert.equal(result.values.rate.hundredths, 800n);
   }
-  assert.equal(valid({ cohorts: [cohort({ label: "x".repeat(40) })] }).cohorts[0].label.length, 40);
-  invalid({ cohorts: [] }, "cohorts", "Add at least one cohort.");
-  invalid({ cohorts: Array.from({ length: 13 }, () => cohort()) }, "cohorts", "Use up to 12 cohorts.");
-  invalid({ model: "optIn" }, "model", "Choose one of the listed options.");
-});
-
-test("MRR checks only active fields and validates the split against every parsed count", () => {
-  assert.equal(valid({ currency: "bad", mrrMethod: "bad", averageMonthly: "$49", monthlyCustomers: "bad",
-    monthlyPrice: "bad", annualCustomers: "bad", annualPrice: "bad" }).newMrr, null);
-  assert.equal(valid({ includeMrr: true, monthlyCustomers: "bad", monthlyPrice: "bad", annualCustomers: "bad", annualPrice: "bad" }).newMrr.mrrCents, 764400n);
-  invalid({ includeMrr: true, currency: "JPY" }, "currency", "Choose one of the listed options.");
-  invalid({ includeMrr: true, mrrMethod: "blend" }, "mrrMethod", "Choose one of the listed options.");
-  invalid({ includeMrr: true, averageMonthly: "" }, "averageMonthly", "Enter an amount.");
-  for (const raw of ["$49", "-1", "+1", "1e3", "1,000", "1 0", "1.001"]) {
-    invalid({ includeMrr: true, averageMonthly: raw }, "averageMonthly", "Use digits with up to two decimals. No signs, commas, or currency symbols.");
+});
+
+test("validates filled cohort rows, names, and the twelve-row boundary", () => {
+  for (const [r, key] of [
+    [row("Sep", "", ""), "starts"], [row("Sep", "100", ""), "paid"],
+    [row("x".repeat(41), "100", "10"), "name"], [row("Sep\n", "100", "10"), "name"],
+    [row("Sep\u007f", "100", "10"), "name"], [row("Sep", "100", "10", "3651"), "ageDays"],
+  ]) {
+    const result = valid({ windowDays: "30", cohorts: [row("", "", ""), r] });
+    assert.ok(result.errors[`cohorts.1.${key}`]);
+    assert.equal(result.values.cohorts, null);
   }
-  invalid({ includeMrr: true, averageMonthly: "1000000000.01" }, "averageMonthly", "Enter an amount up to 1,000,000,000.00.");
-  const split = { includeMrr: true, mrrMethod: "split", monthlyCustomers: "100", monthlyPrice: "10", annualCustomers: "50", annualPrice: "100" };
-  invalid(split, "monthlyCustomers", "Monthly and annual customers must add up to 156, the paid customers above.");
-  invalid({ ...split, annualPrice: "-1" }, "annualPrice", "Use digits with up to two decimals. No signs, commas, or currency symbols.");
-  invalid({ ...split, monthlyCustomers: "-1" }, "monthlyCustomers", "Counts can't be negative.");
-  const badCohortCount = calculateFreeTrialConversion(input({ ...split, cohorts: [cohort({ starts: "bad" })] }));
-  assert.equal(badCohortCount.status, "invalid");
-  assert.equal(badCohortCount.errors.monthlyCustomers, undefined);
-  const badSplitCount = calculateFreeTrialConversion(input({ ...split, annualCustomers: "bad" }));
-  assert.equal(badSplitCount.errors.monthlyCustomers, undefined);
-  invalid({ ...split, cohorts: [cohort({ starts: "2000", paid: "1180" })] }, "monthlyCustomers", "Monthly and annual customers must add up to 1,180, the paid customers above.");
-});
-
-test("malformed payloads never throw and collect independent errors in one pass", () => {
-  for (const raw of [null, undefined, [], 3, "form", input({ cohorts: {} }), input({ cohorts: [null] }),
-    input({ cohorts: [[]] }), input({ cohorts: Array(1) }), input({ includeMrr: "yes" })]) {
-    const result = calculateFreeTrialConversion(raw);
+  assert.equal(clean({ cohorts: [row("🙂".repeat(40), "100", "10")] }).cohorts.rows[1].name, "🙂".repeat(40));
+  const rows = Array.from({ length: TRIAL_MAX_COHORTS }, (_, i) => row(`Cohort ${i}`, "10000000", "10000000"));
+  assert.equal(clean({ cohorts: rows }).cohorts.rows.length, 13);
+  const excess = valid({ cohorts: [...rows, row("Extra", "1", "0")] });
+  assert.ok(excess.errors.cohorts);
+  assert.equal(excess.values.cohorts, null);
+});
+
+test("rejects malformed payloads without throwing", () => {
+  for (const payload of [null, undefined, 1, "500", [], {}, input({ cohorts: null }), input({ cohorts: {} }), input({ cohorts: [null] })]) {
+    const result = calculateFreeTrialConversion(payload);
     assert.equal(result.status, "invalid");
     assert.equal(result.values, null);
-    assert.equal(result.errors.form, "Something in the form is out of date. Reset and try again.");
+    assert.ok(result.errors.form);
   }
-  const result = calculateFreeTrialConversion(input({ model: "optIn", windowDays: "", includeMrr: true,
-    currency: "JPY", averageMonthly: "$49", cohorts: [
-      cohort({ label: "x".repeat(41), starts: "-5", paid: "1e3", ageDays: "-1" }),
-      cohort({ starts: "100", paid: "101", ageDays: "" }),
-    ],
-  }));
+});
+
+test("share links omit empty values and sanitize cohort delimiters", () => {
+  const source = input({ windowDays: "30", ageDays: "45", cohorts: [row("Jul", "400", "36", "75"), row("Sep~|26", "450", "18", "10")] });
+  const params = freeTrialShareParams(source);
+  assert.deepEqual(params, { type: "noCard", starts: "500", paid: "40", window: "30", age: "45", cohorts: "Jul~400~36~75|Sep26~450~18~10" });
+  assert.deepEqual(read(params), { ...source, cohorts: [row("Jul", "400", "36", "75", "shared-0"), row("Sep26", "450", "18", "10", "shared-1")] });
+  assert.deepEqual(read({}), input());
+  assert.deepEqual(freeTrialShareParams(input({ cohorts: [row("", "", "")] })), { type: "noCard", starts: "500", paid: "40" });
+});
+
+test("share links round trip all fields and pass invalid text through for field errors", () => {
+  const source = input({ trialType: "cardUpfront", starts: "500", paid: "40", windowDays: "30", ageDays: "12", activated: "200", targetRate: "10", currency: "EUR", monthlyPrice: "29", annualPrice: "290", annualAccounts: "10", cohorts: [row("Jul", "400", "36", "75")] });
+  assert.deepEqual(read(freeTrialShareParams(source)), { ...source, cohorts: [{ ...source.cohorts[0], id: "shared-0" }] });
+  assert.equal(freeTrialShareParams(input({ currency: "EUR" })).currency, undefined);
+  assert.equal(freeTrialShareParams(input({ monthlyPrice: "0", currency: "EUR" })).currency, "EUR");
+  const bad = read({ starts: "1,180", monthly: "$29", cohorts: "Bad~100~120~" });
+  assert.equal(bad.starts, "1,180");
+  const result = calculateFreeTrialConversion(bad);
   assert.equal(result.status, "invalid");
-  assert.deepEqual(Object.keys(result.errors).sort(), ["model", "windowDays", "currency", "averageMonthly",
-    "cohorts.0.label", "cohorts.0.starts", "cohorts.0.paid", "cohorts.0.ageDays", "cohorts.1.paid", "cohorts.1.ageDays"].sort());
+  for (const key of ["starts", "monthlyPrice", "cohorts.0.paid"]) assert.ok(result.errors[key]);
+  assert.equal(read({ cohorts: Array.from({ length: 13 }, (_, i) => `${i}~100~10~`).join("|") }).cohorts.length, 12);
 });
diff --git a/tests/pages/kdp-minimum-list-price-calculator/minimum-list-price.test.mjs b/tests/pages/kdp-minimum-list-price-calculator/minimum-list-price.test.mjs
index b942238e..5fa4f7a6 100644
--- a/tests/pages/kdp-minimum-list-price-calculator/minimum-list-price.test.mjs
+++ b/tests/pages/kdp-minimum-list-price-calculator/minimum-list-price.test.mjs
@@ -60,7 +60,7 @@ test("uses the fixed-only hardcover cost and searches cent boundaries", () => {
     pageCountText: "100",
   })));
   assert.equal(values.deductionCents, 680);
-  assert.equal(values.minimumPriceCents, 1_134);
+  assert.equal(values.minimumPriceCents, 1_133);
   assert.equal(getKdpPrintPricePoint(1_299, 680).royaltyCents, 99);
   assert.equal(values.priceCents, 1_300);
   assert.equal(values.royaltyCents, 100);
diff --git a/tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs b/tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs
index 52794139..f733841a 100644
--- a/tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs
+++ b/tests/pages/kdp-royalty-calculator/kdp-royalty-calculator.test.mjs
@@ -1,232 +1,356 @@
 import assert from "node:assert/strict";
 import test from "node:test";
-import { calculateKdpRoyalty, parseKdpRoyaltyMoney } from "../../../lib/kdp/royalty.ts";
+import { calculateKdpRoyaltyEstimate } from "../../../lib/kdp/royalty-calculator.ts";
+import { calculateKdpMinimumListPrice } from "../../../lib/kdp/minimum-list-price.ts";
+import { calculateKdpPriceProfit } from "../../../lib/kdp/price-profit.ts";
+import {
+  KDP_ROYALTY_VERSION,
+  getKdpEbookDeliveryCents,
+  getKdpEbookPricePoint,
+  getKdpPrintFloorCents,
+  parseKdpRoyaltyMoney,
+} from "../../../lib/kdp/royalty.ts";
+import { getKdpPageLimit, getKdpTrimOptions } from "../../../lib/kdp/specs.ts";
 
-test("accepts one optional leading dollar sign for price and target", () => {
-  for (const text of ["19.99", "$19.99", " $19.99 "]) {
-    assert.equal(parseKdpRoyaltyMoney(text), 19.99);
-  }
-  assert.equal(parseKdpRoyaltyMoney("$0"), 0);
-  for (const text of ["", "$", "$$19.99", "19.99$", "$ 19.99", "1,000", "1e2", "-1", "1.009"]) {
-    assert.ok(Number.isNaN(parseKdpRoyaltyMoney(text)), text);
-  }
-  const result = calculateKdpRoyalty({
-    format: "paperback", trimId: "6x9", pageCount: 300, interior: "black-white", paper: "white",
-    listPrice: parseKdpRoyaltyMoney("$14.99"), monthlyTarget: parseKdpRoyaltyMoney("$500"),
+function input(overrides = {}) {
+  return {
+    format: "paperback", listPriceText: "12.99", pageCountText: "200", interior: "black-white",
+    trimId: "", paper: "", channel: "", fileSizeText: "", plan: "", monthlyGoalText: "",
+    ...overrides,
+  };
+}
+
+function calculate(overrides = {}) {
+  const result = calculateKdpRoyaltyEstimate(input(overrides));
+  assert.equal(result.status, "calculated", JSON.stringify(result));
+  return result.values;
+}
+
+const examples = [
+  ["opening paperback", {}, 1_299, 60, 439, 680, 340],
+  ["50% rate just below the step", { listPriceText: "9.98" }, 998, 50, 159, 680, 340],
+  ["60% rate at the step", { listPriceText: "9.99" }, 999, 60, 259, 680, 340],
+  ["price below the print minimum", { listPriceText: "5.99" }, 680, 50, 0, 680, 340],
+  ["odd pages", { pageCountText: "201" }, 1_299, 60, 437, 685, 342],
+  ["long book above the entered price", { pageCountText: "600" }, 1_367, 60, 0, 1_367, 820],
+  ["large trim", { trimId: "8.5x11", pageCountText: "120", listPriceText: "7.99" }, 799, 50, 96, 608, 304],
+  ["Expanded Distribution", { channel: "expanded" }, 1_299, 40, 180, 850, 340],
+  ["price below Expanded Distribution break-even", { channel: "expanded", listPriceText: "7.99" }, 850, 40, 0, 850, 340],
+  ["hardcover", { format: "hardcover", pageCountText: "300", listPriceText: "24.99" }, 2_499, 60, 574, 1_542, 925],
+  ["eBook at 70% with default size", { format: "ebook", listPriceText: "4.99" }, 499, 70, 328, 99, 30],
+  ["eBook at 70% with 5 MB", { format: "ebook", listPriceText: "4.99", fileSizeText: "5" }, 499, 70, 297, 199, 75],
+  ["top of the 70% band", { format: "ebook", listPriceText: "12.99" }, 1_299, 70, 888, 99, 30],
+  ["one cent above the 70% band", { format: "ebook", listPriceText: "13.00" }, 1_300, 35, 455, 99, 0],
+  ["above the 70% band", { format: "ebook", listPriceText: "13.99" }, 1_399, 35, 490, 99, 0],
+  ["eBook minimum by size", { format: "ebook", listPriceText: "0.99", fileSizeText: "5" }, 199, 35, 70, 199, 0],
+  ["delivery above the share", { format: "ebook", listPriceText: "2.99", fileSizeText: "30" }, 299, 70, 0, 299, 299],
+];
+
+for (const [name, overrides, price, rate, royalty, minimum, cost] of examples) {
+  test(name, () => {
+    const values = calculate(overrides);
+    assert.equal(values.priceCents, price);
+    assert.equal(values.rate, rate);
+    assert.equal(values.royaltyCents, royalty);
+    assert.equal(values.minimumPriceCents, minimum);
+    assert.equal(values.split.costCents, cost);
+    assert.equal(values.split.royaltyCents + values.split.costCents + values.split.amazonCents, price);
+    assert.equal(values.rulesVersion, KDP_ROYALTY_VERSION);
+    assert.deepEqual(values.curve.mark, { priceCents: price, royaltyCents: royalty });
+  });
+}
+
+// Observed on https://kdp.amazon.com/en_US/royalty-calculator on 2026-10-11.
+const officialPrintCases = [
+  ["paperback", "black-white", "202", "12.98", 342, 685, 436],
+  ["paperback", "black-white", "202", "12.99", 342, 685, 437],
+  ["paperback", "standard-color", "110", "12.98", 381, 761, 398],
+  ["paperback", "standard-color", "110", "12.99", 381, 761, 399],
+  ["paperback", "standard-color", "130", "12.99", 432, 863, 348],
+  ["paperback", "standard-color", "102", "12.98", 360, 720, 419],
+  ["paperback", "standard-color", "200", "12.98", 610, 1_017, 169],
+  ["paperback", "black-white", "332", "9.97", 498, 997, 0],
+  ["hardcover", "black-white", "100", "12.98", 680, 1_133, 99],
+  ["hardcover", "black-white", "202", "24.98", 807, 1_346, 691],
+];
+
+for (const [format, interior, pageCountText, listPriceText, cost, minimum, royalty] of officialPrintCases) {
+  test(`matches KDP for ${format}, ${interior}, ${pageCountText} pages at $${listPriceText}`, () => {
+    const values = calculate({ format, interior, pageCountText, listPriceText });
+    assert.equal(values.printing.costCents, cost);
+    assert.equal(values.minimumPriceCents, minimum);
+    assert.equal(values.royaltyCents, royalty);
+    assert.deepEqual(values.curve.series[0].points.find(([price]) => price === values.priceCents), [values.priceCents, royalty]);
+    const minimumResult = calculateKdpMinimumListPrice({
+      format, interior, pageCountText, trimId: "6x9", paper: "white",
+      ebookRoyaltyOption: 70, ebookFileSizeText: "", desiredRoyaltyText: "",
+    });
+    assert.equal(minimumResult.status, "available");
+    assert.equal(minimumResult.values.minimumPriceCents, minimum);
+    assert.equal(minimumResult.values.deductionCents, cost);
+    assert.ok(Number.isInteger(minimumResult.values.royaltyCents));
+    assert.ok(minimumResult.values.royaltyCents >= 0);
   });
-  assert.equal(result.status, "valid");
-  assert.equal(result.values?.royaltyCents, 439);
-  assert.equal(result.values?.copiesForMonthlyTarget, 114);
+}
+
+test("print profit and target-price calculations use the same unrounded printing cost", () => {
+  const result = calculateKdpPriceProfit({
+    listPriceText: "12.98", includeCosts: true, plannedCopiesText: "100",
+    options: [
+      { id: "black", binding: "paperback", trimId: "6x9", interior: "black-white", paper: "white", pageCountText: "202", otherCostPerSaleText: "1", oneTimeCostText: "100" },
+      { id: "color", binding: "paperback", trimId: "6x9", interior: "standard-color", paper: "white", pageCountText: "110", otherCostPerSaleText: "1", oneTimeCostText: "100" },
+    ],
+  });
+  assert.equal(result.status, "calculated");
+  assert.deepEqual(result.values.rows.map((row) => [row.printingCostCents, row.minimumPriceCents, row.royaltyCents, row.profitCents]), [
+    [342, 685, 436, 23_600], [381, 761, 398, 19_800],
+  ]);
+  const target = calculateKdpMinimumListPrice({
+    format: "paperback", interior: "black-white", pageCountText: "202", trimId: "6x9", paper: "white",
+    ebookRoyaltyOption: 70, ebookFileSizeText: "", desiredRoyaltyText: "4.37",
+  });
+  assert.equal(target.status, "available");
+  assert.equal(target.values.priceCents, 1_299);
+  assert.equal(target.values.royaltyCents, 437);
 });
 
-test("reports only the applied ebook delivery deduction at 35 percent", () => {
-  for (const [listPrice, ebookRoyaltyOption] of [[12.99, 35], [13, 70], [1.99, 70]]) {
-    const result = calculateKdpRoyalty({ format: "ebook", ebookFileSizeMB: 5, ebookRoyaltyOption, listPrice });
-    assert.equal(result.status, "valid");
-    assert.equal(result.values?.effectiveRoyaltyRate, 35);
-    assert.equal(result.values?.deliveryCostCents, 0);
-    assert.equal(result.values?.royaltyCents, Math.round(listPrice * 100 * 0.35));
-    assert.equal(result.values?.pricePoints.find((point) => point.listPriceCents === Math.round(listPrice * 100))?.deductionCents, 0);
-  }
+test("opening answer includes its printing breakdown and share", () => {
+  const values = calculate();
+  assert.deepEqual(values.printing, { enteredPages: 200, printedPages: 200, costCents: 340, fixedCents: 100, pageCents: 240 });
+  assert.deepEqual(values.split, { royaltyCents: 439, costCents: 340, amazonCents: 520 });
+  assert.equal(values.shareBasisPoints, 3_380);
+  assert.equal(values.limit, null);
+  assert.equal(values.comparison, null);
+  assert.equal(values.channel, "amazon");
+  assert.equal(values.plan, null);
+  assert.equal(values.costKind, "printing");
+  assert.equal(values.delivery, null);
+  assert.equal(calculate({ pageCountText: "201" }).printing.printedPages, 202);
 });
 
-test("explains a negative ebook royalty without treating it as invalid", () => {
-  const base = { format: "ebook", ebookFileSizeMB: 20, ebookRoyaltyOption: 70, listPrice: 2.99, monthlyTarget: 100 };
-  const result = calculateKdpRoyalty(base);
-  assert.equal(result.status, "valid");
-  assert.equal(result.values?.royaltyCents, -1);
-  assert.equal(result.values?.deliveryCostCents, 300);
-  assert.equal(result.values?.breakEvenAdSpendCents, 0);
-  assert.equal(result.values?.breakEvenAcosBasisPoints, null);
-  assert.equal(result.values?.monthlyTargetStatus, "unavailable");
-  assert.ok(result.issues.some((issue) => issue.code === "ebook-negative-royalty" && issue.severity === "warning"));
-  for (const overrides of [{ listPrice: 3 }, { listPrice: 3.01 }, { ebookRoyaltyOption: 35 }]) {
-    assert.ok(!calculateKdpRoyalty({ ...base, ...overrides }).issues.some((issue) => issue.code === "ebook-negative-royalty"));
+test("price limits answer at the boundary and preserve the entered price", () => {
+  for (const [overrides, entered, answered, kind] of [
+    [{ listPriceText: "5.99" }, 599, 680, "below-minimum"],
+    [{ channel: "expanded", listPriceText: "7.99" }, 799, 850, "below-break-even"],
+    [{ listPriceText: "300" }, 30_000, 25_000, "above-maximum"],
+    [{ format: "hardcover", pageCountText: "300", listPriceText: "300" }, 30_000, 25_000, "above-maximum"],
+    [{ format: "ebook", listPriceText: "250" }, 25_000, 20_000, "above-maximum"],
+    [{ format: "ebook", listPriceText: "0.01" }, 1, 99, "below-minimum"],
+  ]) {
+    const values = calculate(overrides);
+    assert.equal(values.enteredPriceCents, entered);
+    assert.equal(values.priceCents, answered);
+    assert.deepEqual(values.limit, { kind, priceCents: answered });
   }
+  assert.equal(calculate({ listPriceText: "250" }).limit, null);
+  assert.equal(calculate({ format: "ebook", listPriceText: "200" }).limit, null);
+  assert.equal(calculate({ listPriceText: "999999999" }).priceCents, 25_000);
+  assert.equal(getKdpPrintFloorCents(499), 998);
+  assert.equal(getKdpPrintFloorCents(500), 999);
 });
 
-test("FF-010 calculates current US paperback print cost and 60 percent royalty", () => {
-  const result = calculateKdpRoyalty({
-    format: "paperback",
-    trimId: "6x9",
-    pageCount: 300,
-    interior: "black-white",
-    paper: "white",
-    listPrice: 9.99,
-    monthlyTarget: 100,
-  });
-  assert.equal(result.status, "valid");
-  assert.ok(result.values);
-  assert.equal(result.values.printingCostCents, 460);
-  assert.equal(result.values.royaltyRate, 60);
-  assert.equal(result.values.royaltyCents, 139);
-  assert.equal(result.values.minimumListPriceCents, 920);
-  assert.equal(result.values.breakEvenAdSpendCents, 139);
-  assert.equal(result.values.breakEvenAcosBasisPoints, 1391);
+test("comparisons use the answered price and the specified priority", () => {
+  for (const [overrides, expected] of [
+    [{ listPriceText: "9.98" }, { kind: "rate-step", priceCents: 999, rate: 60, royaltyCents: 259 }],
+    [{ channel: "expanded" }, { kind: "other-channel", priceCents: 1_299, rate: 60, royaltyCents: 439 }],
+    [{ channel: "expanded", listPriceText: "7.99" }, { kind: "other-channel", priceCents: 850, rate: 50, royaltyCents: 85 }],
+    [{ format: "ebook", listPriceText: "4.99" }, { kind: "other-plan", priceCents: 499, rate: 35, royaltyCents: 175 }],
+    [{ format: "ebook", listPriceText: "4.99", plan: "35" }, { kind: "other-plan", priceCents: 499, rate: 70, royaltyCents: 328 }],
+    [{ format: "ebook", listPriceText: "13.99" }, { kind: "seventy-band", priceCents: 1_299, rate: 70, royaltyCents: 888 }],
+    [{ format: "ebook", listPriceText: "1.99" }, { kind: "seventy-band", priceCents: 299, rate: 70, royaltyCents: 188 }],
+    [{ format: "ebook", listPriceText: "13.99", plan: "35" }, { kind: "seventy-band", priceCents: 1_299, rate: 70, royaltyCents: 888 }],
+    [{ format: "ebook", listPriceText: "2.99", fileSizeText: "30" }, { kind: "other-plan", priceCents: 299, rate: 35, royaltyCents: 105 }],
+  ]) assert.deepEqual(calculate(overrides).comparison, expected);
+  assert.equal(calculate({ format: "ebook", listPriceText: "1.99" }).seventyOutsideBand, "below");
+  assert.equal(calculate({ format: "ebook", listPriceText: "13" }).seventyOutsideBand, "above");
+  assert.equal(calculate({ format: "ebook", listPriceText: "13", plan: "35" }).seventyOutsideBand, null);
 });
 
-test("FF-011 uses short-run and large-trim pricing branches", () => {
-  const short = calculateKdpRoyalty({
-    format: "paperback",
-    trimId: "6x9",
-    pageCount: 100,
-    interior: "black-white",
-    paper: "white",
-    listPrice: 9.98,
-  });
-  assert.equal(short.values?.printingCostCents, 230);
-  assert.equal(short.values?.royaltyRate, 50);
-  assert.equal(short.values?.royaltyCents, 269);
-
-  const largeColor = calculateKdpRoyalty({
-    format: "paperback",
-    trimId: "8.5x11",
-    pageCount: 300,
-    interior: "standard-color",
-    paper: "white",
-    listPrice: 24.99,
-  });
-  assert.equal(largeColor.values?.printingCostCents, 1306);
-  assert.equal(largeColor.values?.royaltyRate, 60);
+test("delivery retains the supplied cost at 35% and reports the default size", () => {
+  const defaultSize = calculate({ format: "ebook", listPriceText: "4.99" });
+  assert.deepEqual(defaultSize.delivery, { fileSizeMB: 2, defaultSize: true, costCents: 30 });
+  assert.equal(defaultSize.channel, null);
+  assert.equal(defaultSize.plan, 70);
+  for (const overrides of [{ plan: "35" }, { listPriceText: "13" }]) {
+    const values = calculate({ format: "ebook", listPriceText: "4.99", fileSizeText: "5", ...overrides });
+    assert.deepEqual(values.delivery, { fileSizeMB: 5, defaultSize: false, costCents: 75 });
+    assert.equal(values.split.costCents, 0);
+    assert.equal(values.costKind, null);
+  }
+  for (const [size, minimum] of [["2.999", 99], ["3", 199], ["9.999", 199], ["10", 299], ["650", 299]]) {
+    assert.equal(calculate({ format: "ebook", fileSizeText: size }).minimumPriceCents, minimum);
+  }
+  assert.equal(calculate({ format: "ebook", fileSizeText: "0.001", listPriceText: "4.99" }).delivery.costCents, 1);
+  assert.equal(calculate({ format: "ebook", fileSizeText: "1.0001", listPriceText: "4.99" }).delivery.costCents, 15);
+  for (const [price, size, exceeds] of [["2.99", "30", true], ["3", "20", true], ["3.01", "20", false]]) {
+    const values = calculate({ format: "ebook", listPriceText: price, fileSizeText: size });
+    assert.equal(values.deliveryExceedsShare, exceeds);
+    assert.ok(values.split.amazonCents >= 0);
+    assert.ok(values.royaltyCents >= 0);
+  }
 });
 
-test("FF-012 calculates ebook delivery and falls back from an ineligible 70 percent price", () => {
-  const valid = calculateKdpRoyalty({
-    format: "ebook",
-    ebookFileSizeMB: 5,
-    ebookRoyaltyOption: 70,
-    listPrice: 9.99,
-    monthlyTarget: 100,
+test("eBook delivery rounds an exact half cent up before calculating royalties and minimum prices", () => {
+  assert.equal(getKdpEbookDeliveryCents(1.5), 23);
+  assert.equal(getKdpEbookDeliveryCents(1_535 / 1_024), 22);
+  assert.equal(getKdpEbookDeliveryCents(1_537 / 1_024), 23);
+  const values = calculate({ format: "ebook", listPriceText: "12.99", fileSizeText: "1.5" });
+  assert.equal(values.delivery.costCents, 23);
+  assert.equal(values.royaltyCents, 893);
+  assert.deepEqual(values.curve.series[0].points.at(-1), [1_299, 893]);
+  const minimum = calculateKdpMinimumListPrice({
+    format: "ebook", trimId: "6x9", interior: "black-white", paper: "white", pageCountText: "200",
+    ebookRoyaltyOption: 70, ebookFileSizeText: "1.5", desiredRoyaltyText: "2.00",
   });
-  assert.equal(valid.status, "valid");
-  assert.equal(valid.values?.deliveryCostCents, 75);
-  assert.equal(valid.values?.effectiveRoyaltyRate, 70);
-  assert.equal(valid.values?.royaltyCents, 647);
-
-  const fallback = calculateKdpRoyalty({
-    format: "ebook",
-    ebookFileSizeMB: 5,
-    ebookRoyaltyOption: 70,
-    listPrice: 1.99,
-  });
-  assert.equal(fallback.status, "valid");
-  assert.equal(fallback.values?.effectiveRoyaltyRate, 35);
-  assert.equal(fallback.values?.royaltyCents, 70);
-  assert.ok(fallback.issues.some((issue) => issue.code === "ebook-70-price-band"));
+  assert.equal(minimum.status, "available");
+  assert.equal(minimum.values.deductionCents, 23);
+  assert.equal(minimum.values.priceCents, 308);
+  assert.equal(minimum.values.royaltyCents, 200);
+  assert.equal(getKdpEbookPricePoint(307, 70, 1.5).royaltyCents, 199);
 });
 
-test("FF-014 keeps the black-ink fixed cost through 110 effective pages", () => {
-  for (const pageCount of [109, 110]) {
-    const result = calculateKdpRoyalty({
-      format: "paperback",
-      trimId: "6x9",
-      pageCount,
-      interior: "black-white",
-      paper: "white",
-      listPrice: 9.99,
-    });
-    assert.equal(result.values?.effectivePageCount, 110);
-    assert.equal(result.values?.printingCostCents, 230);
+test("money parsing accepts cents without rounding excess decimals", () => {
+  for (const [text, cents] of [["12", 1_200], ["12.5", 1_250], [" $12.99 ", 1_299], ["0.29", 29]]) {
+    assert.equal(calculate({ listPriceText: text }).enteredPriceCents, cents);
+  }
+  for (const text of ["abc", "0", "12.999", "", "$", "$$12.99", "12.99$", "$ 12.99", "1,000", "1e2", "Infinity", "-1", "NaN", "9".repeat(400)]) {
+    const result = calculateKdpRoyaltyEstimate(input({ listPriceText: text }));
+    assert.equal(result.status, "invalid", text);
+    assert.ok(result.fieldErrors.listPrice, text);
   }
+  assert.equal(parseKdpRoyaltyMoney(" $12.99 "), 12.99);
+  assert.ok(Number.isNaN(parseKdpRoyaltyMoney("12.999")));
+});
 
-  const next = calculateKdpRoyalty({
-    format: "paperback",
-    trimId: "6x9",
-    pageCount: 111,
-    interior: "black-white",
-    paper: "white",
-    listPrice: 9.99,
-  });
-  assert.equal(next.values?.effectivePageCount, 112);
-  assert.equal(next.values?.printingCostCents, 234);
+test("monthly goals never block an otherwise valid royalty", () => {
+  assert.deepEqual(calculate({ monthlyGoalText: "$1000" }).goal, { goalCents: 100_000, copies: 228 });
+  assert.deepEqual(calculate({ listPriceText: "5.99", monthlyGoalText: "1000" }).goal, { goalCents: 100_000, copies: null });
+  assert.equal(calculate().goal, null);
+  assert.equal(calculate({ monthlyGoalText: "10000000" }).goal.goalCents, 1_000_000_000);
+  for (const text of ["-5", "0", "abc", "1.999", "10000000.01"]) {
+    const result = calculateKdpRoyaltyEstimate(input({ monthlyGoalText: text }));
+    assert.equal(result.status, "calculated");
+    assert.equal(result.values.royaltyCents, 439);
+    assert.equal(result.values.goal, null);
+    assert.deepEqual(Object.keys(result.fieldErrors), ["monthlyGoal"]);
+  }
 });
 
-test("FF-017 normalizes odd hardcover premium pages before cent arithmetic", () => {
-  const result = calculateKdpRoyalty({
-    format: "hardcover",
-    trimId: "6x9",
-    pageCount: 75,
-    interior: "premium-color",
-    paper: "white",
-    listPrice: 24.99,
-  });
-  assert.equal(result.status, "valid");
-  assert.equal(result.values?.effectivePageCount, 76);
-  assert.equal(result.values?.printingCostCents, 1059);
+test("invalid choices and fields report their own errors", () => {
+  for (const [overrides, field] of [
+    [{ format: "audio" }, "format"],
+    [{ interior: "" }, "interior"],
+    [{ format: "hardcover", interior: "standard-color" }, "interior"],
+    [{ trimId: "8.25x11" }, "trimId"],
+    [{ format: "hardcover", trimId: "5x8" }, "trimId"],
+    [{ trimId: "unknown" }, "trimId"],
+    [{ paper: "unknown" }, "paper"],
+    [{ format: "hardcover", paper: "groundwood" }, "paper"],
+    [{ interior: "premium-color", paper: "cream" }, "paper"],
+    [{ interior: "standard-color", trimId: "8.27x11.69" }, "interior"],
+    [{ channel: "unknown" }, "channel"],
+    [{ format: "ebook", plan: "60" }, "plan"],
+    ...["0", "-1", "650.01", "abc", "Infinity"].map((fileSizeText) => [{ format: "ebook", fileSizeText }, "fileSize"]),
+    ...["", "0", "-1", "200.5", "1e2", "abc"].map((pageCountText) => [{ pageCountText }, "pageCount"]),
+  ]) {
+    const result = calculateKdpRoyaltyEstimate(input(overrides));
+    assert.equal(result.status, "invalid", JSON.stringify(overrides));
+    assert.ok(result.fieldErrors[field], JSON.stringify(overrides));
+  }
+  assert.equal(calculate({ format: "hardcover", channel: "unknown" }).channel, "amazon");
+  assert.equal(calculate({ format: "paperback", fileSizeText: "invalid", plan: "invalid" }).royaltyCents, 439);
+  assert.equal(calculate({ format: "ebook", listPriceText: "4.99", pageCountText: "invalid", interior: "invalid", trimId: "invalid", paper: "invalid", channel: "invalid" }).royaltyCents, 328);
 });
 
-test("FF-018 accepts raw 23 pages when the normalized count is valid and rejects 829", () => {
-  const minimum = calculateKdpRoyalty({
-    format: "paperback",
-    trimId: "6x9",
-    pageCount: 23,
-    interior: "black-white",
-    paper: "white",
-    listPrice: 9.99,
-  });
-  assert.equal(minimum.status, "valid");
-  assert.equal(minimum.values?.effectivePageCount, 24);
-
-  const overMaximum = calculateKdpRoyalty({
-    format: "paperback",
-    trimId: "6x9",
-    pageCount: 829,
-    interior: "black-white",
-    paper: "white",
-    listPrice: 9.99,
-  });
-  assert.equal(overMaximum.status, "invalid");
-  assert.equal(overMaximum.values, null);
-  assert.equal(overMaximum.values?.effectivePageCount, undefined);
-  assert.ok(overMaximum.issues.some((issue) => issue.code === "page-count-out-of-range"));
+test("page limits use printed pages and name the KDP range", () => {
+  for (const [overrides, range] of [
+    [{ pageCountText: "829" }, /24 to 828/],
+    [{ format: "hardcover", pageCountText: "60" }, /75 to 550/],
+    [{ interior: "standard-color", pageCountText: "70" }, /72 to 600/],
+    [{ paper: "cream", pageCountText: "777" }, /24 to 776/],
+    [{ paper: "groundwood", pageCountText: "813" }, /24 to 812/],
+  ]) {
+    const result = calculateKdpRoyaltyEstimate(input(overrides));
+    assert.equal(result.status, "invalid");
+    assert.match(result.fieldErrors.pageCount, /KDP/);
+    assert.match(result.fieldErrors.pageCount, range);
+  }
+  assert.equal(calculate({ pageCountText: "23" }).printing.printedPages, 24);
+  assert.equal(calculate({ pageCountText: "828" }).printing.printedPages, 828);
+  assert.equal(calculate({ format: "hardcover", pageCountText: "75", interior: "premium-color", listPriceText: "24.99" }).printing.costCents, 1_059);
 });
 
-test("FF-015 distinguishes blank, zero, and unavailable monthly targets", () => {
-  const base = {
-    format: "ebook",
-    ebookFileSizeMB: 5,
-    ebookRoyaltyOption: 70,
-    listPrice: 9.99,
-  };
-  assert.equal(calculateKdpRoyalty(base).values?.monthlyTargetStatus, "omitted");
-  assert.equal(calculateKdpRoyalty({ ...base, monthlyTarget: 0 }).values?.copiesForMonthlyTarget, 0);
-  assert.equal(calculateKdpRoyalty({ ...base, monthlyTarget: 0 }).values?.monthlyTargetStatus, "calculated");
+test("short print runs keep the shared fixed-cost boundaries", () => {
+  for (const [overrides, cost] of [
+    [{ pageCountText: "109" }, 230],
+    [{ pageCountText: "111" }, 234],
+    [{ paper: "groundwood", pageCountText: "112" }, 223],
+    [{ paper: "groundwood", pageCountText: "113" }, 230],
+    [{ interior: "premium-color", pageCountText: "40" }, 360],
+    [{ interior: "premium-color", pageCountText: "41" }, 373],
+    [{ format: "hardcover", pageCountText: "108", listPriceText: "24.99" }, 680],
+    [{ format: "hardcover", pageCountText: "109", listPriceText: "24.99" }, 697],
+    [{ trimId: "8.5x11", interior: "standard-color", pageCountText: "300", listPriceText: "24.99" }, 1_306],
+  ]) assert.equal(calculate(overrides).printing.costCents, cost);
+  // Other tools retain their signed estimate instead of this calculator's zero floor.
+  assert.equal(getKdpEbookPricePoint(299, 70, 650).royaltyCents, -6_616);
 });
 
-test("FF-016 comparison prices stay unique and within the active format bounds", () => {
-  const result = calculateKdpRoyalty({
-    format: "ebook",
-    ebookFileSizeMB: 5,
-    ebookRoyaltyOption: 70,
-    listPrice: 200,
-  });
-  const prices = result.values?.pricePoints.map((point) => point.listPriceCents) ?? [];
-  assert.deepEqual(prices, [...new Set(prices)]);
-  assert.ok(prices.every((price) => price >= 199 && price <= 20_000));
+test("curves include limits, selected price, and the rule boundaries", () => {
+  const opening = calculate();
+  assert.equal(opening.curve.series[0].points.at(-1)[0], 1_999);
+  assert.equal(opening.curve.series[0].points[0][0], 680);
+  assert.deepEqual(opening.curve.series[0].points.find(([price]) => price === 998), [998, 159]);
+  assert.deepEqual(opening.curve.series[0].points.find(([price]) => price === 999), [999, 259]);
+  const expanded = calculate({ channel: "expanded" });
+  assert.deepEqual(expanded.curve.series.map((series) => series.id), ["expanded", "amazon"]);
+  assert.deepEqual(expanded.curve.series[0].points[0], [850, 0]);
+  assert.deepEqual(expanded.curve.series[1].points[0], [680, 0]);
+  const ebook = calculate({ format: "ebook", listPriceText: "4.99" });
+  assert.deepEqual(ebook.curve.series.map((series) => series.id), ["plan70", "plan35"]);
+  assert.deepEqual(ebook.curve.series[0].points.at(-1), [1_299, 888]);
+  assert.deepEqual(ebook.curve.series[1].points.find(([price]) => price === 1_300), [1_300, 455]);
+  assert.ok(ebook.curve.series[1].points.some(([price]) => price === 298));
+  assert.equal(ebook.curve.series[1].points.at(-1)[0], 1_599);
+  assert.deepEqual(calculate({ format: "ebook", plan: "35" }).curve.series.map((series) => series.id), ["plan35", "plan70"]);
+  assert.equal(calculate({ listPriceText: "250" }).curve.series[0].points.at(-1)[0], 25_000);
+  assert.equal(calculate({ format: "ebook", listPriceText: "200" }).curve.series[0].points.at(-1)[0], 1_299);
+  assert.equal(calculate({ format: "ebook", listPriceText: "200" }).curve.series[1].points.at(-1)[0], 20_000);
 });
 
-test("FF-013 computes copies to target and rejects impossible print configurations", () => {
-  const target = calculateKdpRoyalty({
-    format: "hardcover",
-    trimId: "6x9",
-    pageCount: 300,
-    interior: "black-white",
-    paper: "white",
-    listPrice: 24.99,
-    monthlyTarget: 500,
-  });
-  assert.equal(target.values?.printingCostCents, 925);
-  assert.equal(target.values?.royaltyCents, 574);
-  assert.equal(target.values?.copiesForMonthlyTarget, 88);
-
-  const invalid = calculateKdpRoyalty({
-    format: "hardcover",
-    trimId: "5x8",
-    pageCount: 300,
-    interior: "black-white",
-    paper: "white",
-    listPrice: 20,
-  });
-  assert.equal(invalid.status, "invalid");
-  assert.ok(invalid.issues.some((issue) => issue.code === "trim-not-supported"));
+test("curve points agree with direct answers and serialize without missing or nonfinite values", () => {
+  for (const overrides of [{}, { channel: "expanded" }, { format: "hardcover" }, { format: "ebook" }, { format: "ebook", plan: "35" }, { format: "ebook", fileSizeText: "650", listPriceText: "2.99" }]) {
+    const values = calculate(overrides);
+    assert.deepEqual(JSON.parse(JSON.stringify(values)), values);
+    for (const series of values.curve.series) {
+      assert.ok(series.points.length >= 2);
+      const prices = series.points.map(([price]) => price);
+      assert.deepEqual(prices, [...new Set(prices)].sort((a, b) => a - b));
+      for (const [price, royalty] of series.points) {
+        assert.ok(Number.isSafeInteger(price) && Number.isSafeInteger(royalty) && royalty >= 0);
+        const selection = series.id.startsWith("plan") ? { plan: series.id.slice(4) } : { channel: series.id };
+        const direct = calculate({ ...overrides, ...selection, listPriceText: (price / 100).toFixed(2) });
+        assert.equal(direct.royaltyCents, royalty);
+      }
+    }
+  }
+});
+
+test("every supported print setup stays calculable at its page limits", () => {
+  for (const format of ["paperback", "hardcover"]) {
+    for (const trim of getKdpTrimOptions(format)) {
+      for (const interior of ["black-white", "standard-color", "premium-color"]) {
+        for (const paper of ["white", "cream", "groundwood"]) {
+          const limit = getKdpPageLimit(trim.id, format, interior, paper);
+          if (!limit) continue;
+          for (const pageCount of [limit.min, limit.max]) {
+            const values = calculate({ format, trimId: trim.id, interior, paper, pageCountText: String(pageCount), listPriceText: "0.01" });
+            assert.ok(values.minimumPriceCents <= values.maximumPriceCents);
+            assert.ok(values.split.amazonCents >= 0 && values.royaltyCents >= 0);
+            assert.equal(values.split.royaltyCents + values.split.costCents + values.split.amazonCents, values.priceCents);
+          }
+        }
+      }
+    }
+  }
 });