fix(resume): hydrate only the retained transcript tail

A larger disk window then a host-side slice left the dropped-rows
notice unpainted. Resume now reads the same tail the transcript
keeps, and overflow still goes through retention eviction.

Author: TheGreatAxios

src/tui/product-host.test.ts

@@ -17,6 +17,7 @@ import { buildModelsFirstCatalog, modelOptionId } from "./model-catalog.js";
 import { hydrateHistoryRows } from "./history-hydrate.js";
 import { MAX_RETAINED_STREAM_ROWS } from "./long-log.js";
 import { enterSubagentObserve } from "./shell/observe.js";
+import { transcriptMarker } from "./shell/transcript.js";
 
 function makeFakeSessionPort(): {
   readonly sends: string[];
@@ -146,9 +147,9 @@ describe("mountProductHost", () => {
         role: "assistant",
         text: `row-${total - 1}`,
       });
-      // Pre-sliced to the cap, so the append loop never trips retention
-      // eviction: no churn, no dropped-rows marker on resume.
-      expect(host.shell.streamLogBase).toBe(0);
+      const dropped = total - MAX_RETAINED_STREAM_ROWS;
+      expect(host.shell.streamLogBase).toBe(dropped);
+      expect(transcriptMarker(host.shell)).toBeDefined();
     } finally {
       host.dispose();
     }
@@ -173,6 +174,7 @@ describe("mountProductHost", () => {
         text: `small-${total - 1}`,
       });
       expect(host.shell.streamLogBase).toBe(0);
+      expect(transcriptMarker(host.shell)).toBeUndefined();
     } finally {
       host.dispose();
     }
@@ -200,12 +202,12 @@ describe("mountProductHost", () => {
         },
       ];
       emitter.emit("history.hydrate", blocks);
-      // Folding merges the pair inside hydration, so the row-level slice keeps
-      // and drops whole merged rows: 605 texts + 1 merged row → newest 600.
-      // A block-level slice would split the pair and paint 599 rows instead.
-      const expected = hydrateHistoryRows(blocks).slice(
-        -MAX_RETAINED_STREAM_ROWS,
-      );
+      // Folding merges the pair inside hydration, so retention evicts whole
+      // merged rows: 605 texts + 1 merged row → newest 600. A block-level
+      // slice would split the pair and paint 599 rows instead.
+      const allRows = hydrateHistoryRows(blocks);
+      const expected = allRows.slice(-MAX_RETAINED_STREAM_ROWS);
+      const dropped = allRows.length - expected.length;
       expect(expected.length).toBe(MAX_RETAINED_STREAM_ROWS);
       expect(host.shell.streamLog).toEqual(expected);
       expect(host.shell.streamLog[0]).toEqual({
@@ -215,7 +217,9 @@ describe("mountProductHost", () => {
       const last = host.shell.streamLog[host.shell.streamLog.length - 1];
       expect(last?.pending).not.toBe(true);
       expect(last?.text).toBe("done cut-1");
-      expect(host.shell.streamLogBase).toBe(0);
+      expect(dropped).toBeGreaterThan(0);
+      expect(host.shell.streamLogBase).toBe(dropped);
+      expect(transcriptMarker(host.shell)).toBeDefined();
     } finally {
       host.dispose();
     }
@@ -246,7 +250,11 @@ describe("mountProductHost", () => {
       );
       expect(host.shell.parentStreamLog).toEqual(expected);
       expect(host.shell.parentStreamLog?.length).toBe(MAX_RETAINED_STREAM_ROWS);
-      expect(host.shell.parentStreamLogBase).toBe(0);
+      expect(host.shell.parentStreamLogBase).toBe(
+        total - MAX_RETAINED_STREAM_ROWS,
+      );
+      expect(host.shell.streamLogBase).toBe(0);
+      expect(transcriptMarker(host.shell)).toBeUndefined();
     } finally {
       host.dispose();
     }

src/tui/product-host.ts

@@ -65,7 +65,6 @@ import {
 import { surfaceSystemNotice } from "./shell/prompt.js";
 import type { DeliverySettle, QueueKind } from "./delivery-queue.js";
 import { hydrateHistoryRows } from "./history-hydrate.js";
-import { MAX_RETAINED_STREAM_ROWS } from "./long-log.js";
 import type { StreamRow } from "./stream.js";
 
 import type { PendingImageAttachment } from "./image-attachments.js";
@@ -542,9 +541,7 @@ export async function mountProductHost(
 
   function onHistory(blocks: unknown): void {
     if (disposed) return;
-    const rows = hydrateHistoryRows(blocks);
-    const tail = rows.slice(-MAX_RETAINED_STREAM_ROWS);
-    for (const row of tail) {
+    for (const row of hydrateHistoryRows(blocks)) {
       appendStreamRow(shell, row);
     }
   }

src/tui/runner/wiring.ts

@@ -501,9 +501,10 @@ export function wirePostStartup(
   // Hydrate a resumed session's transcript after first paint. Reading history and
   // mapping it to content blocks is pure I/O with no bearing on the shell, so the
   // App renders empty immediately and fills in the past turns once they are ready.
-  // Only the tail needed to fill RESUME_TRANSCRIPT_BLOCK_LIMIT blocks is read from
-  // disk — a long session's full history is not needed just to paint a transcript
-  // that itself caps how much it displays.
+  // Only the retained transcript tail is read from disk — a long session's
+  // full history is not needed just to paint a display that itself caps how
+  // much it keeps. Agent conversation state still loads in full via
+  // ContextStore.load(); this path is display-only.
   void loadRecentTurns(state.workdir, RESUME_TRANSCRIPT_BLOCK_LIMIT)
     .then((turns) => {
       const blocks = turnsToContentBlocks(turns, {

src/tui/turns-to-blocks.test.ts

@@ -1,7 +1,11 @@
 import { describe, test, expect } from "bun:test";
 import type { ConversationTurn } from "@intx/types/runtime";
 import { buildMailboxMailPrompt } from "../subagent/mailbox-mail-drive.js";
-import { turnsToContentBlocks } from "./turns-to-blocks.js";
+import {
+  RESUME_TRANSCRIPT_BLOCK_LIMIT,
+  turnsToContentBlocks,
+} from "./turns-to-blocks.js";
+import { MAX_RETAINED_STREAM_ROWS } from "./long-log.js";
 import { hydrateTasksFromTurns } from "../agent/director.js";
 
 function manageTasksTurn(
@@ -115,6 +119,12 @@ describe("turnsToContentBlocks marks occupancy wakes with system origin", () =>
   });
 });
 
+describe("RESUME_TRANSCRIPT_BLOCK_LIMIT", () => {
+  test("matches the retained stream tail, not a larger pre-slice", () => {
+    expect(RESUME_TRANSCRIPT_BLOCK_LIMIT).toBe(MAX_RETAINED_STREAM_ROWS);
+  });
+});
+
 describe("hydrateTasksFromTurns", () => {
   test("derives the task list from manage_tasks tool calls in a transcript", () => {
     const turns = [manageTasksTurn("m1", "doing"), toolResultTurn("m1", false)];

src/tui/turns-to-blocks.ts

@@ -4,6 +4,7 @@ import type {
 } from "@intx/types/runtime";
 
 import { isPersistedOccupancyWakeText } from "../subagent/mailbox-mail-drive.js";
+import { MAX_RETAINED_STREAM_ROWS } from "./long-log.js";
 import { validateView } from "./view/validate.js";
 import type { ViewNode } from "./view/spec.js";
 
@@ -209,7 +210,9 @@ function finalizeResumeToolBlocks(
   return out;
 }
 
-export const RESUME_TRANSCRIPT_BLOCK_LIMIT = 2000;
+// Resume paints into the same retained log live turns use, so the disk/block
+// window is the retention cap rather than a larger pre-slice.
+export const RESUME_TRANSCRIPT_BLOCK_LIMIT = MAX_RETAINED_STREAM_ROWS;
 
 interface TurnsToContentBlocksOptions {
   maxBlocks?: number;