diff --git a/apps/web/src/app.css b/apps/web/src/app.css
index 3b8e7d2566..6bc5ac588e 100644
--- a/apps/web/src/app.css
+++ b/apps/web/src/app.css
@@ -3709,7 +3709,10 @@ tr.insights-row-clickable:hover {
 }
 .chat-thread-body {
   min-width: 0;
-  font-size: 0.9rem;
+  /* 16px minimum: keeps the transcript readable and matches the composer
+     below, and avoids mobile Safari's zoom-on-focus threshold. */
+  font-size: max(var(--text-base), 16px);
+  font-weight: var(--font-weight-medium);
   line-height: 1.55;
 }
 .chat-thread-error {
@@ -3725,14 +3728,84 @@ tr.insights-row-clickable:hover {
   font-size: 0.82rem;
   color: var(--muted-foreground);
 }
+
+/* Shared composer: transcript-matched text field on the left, a grouped
+   action rail (Send only — no turn cancellation exists yet) on the right. */
 .chat-composer {
   display: flex;
-  flex-direction: column;
-  gap: 0.5rem;
   align-items: flex-end;
-}
-.chat-composer > textarea {
+  gap: 0.5rem;
   width: 100%;
+  padding: 0.5rem 0.75rem;
+  border: 1px solid var(--border);
+  border-radius: var(--radius-lg, 0.75rem);
+  background: var(--card, var(--background));
+}
+.chat-composer:focus-within {
+  border-color: var(--ring, var(--primary));
+}
+.chat-composer-input {
+  flex: 1;
+  min-width: 0;
+  resize: none;
+  border: 0;
+  background: transparent;
+  padding: 0.35rem 0;
+  font: inherit;
+  font-size: max(var(--text-base), 16px);
+  font-weight: var(--font-weight-medium);
+  line-height: 1.5;
+  color: var(--foreground);
+}
+.chat-composer-input:focus {
+  outline: none;
+}
+.chat-composer-input::placeholder {
+  color: var(--muted-foreground);
+}
+.chat-composer-input:disabled {
+  cursor: not-allowed;
+  opacity: 0.6;
+}
+.chat-composer-rail {
+  display: flex;
+  align-items: center;
+  gap: 0.25rem;
+  flex-shrink: 0;
+  padding-bottom: 0.35rem;
+}
+.chat-composer-send {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 2rem;
+  height: 2rem;
+  border: 0;
+  border-radius: 999px;
+  background: var(--primary);
+  color: var(--primary-foreground);
+  cursor: pointer;
+}
+.chat-composer-send:disabled {
+  cursor: not-allowed;
+  background: var(--muted);
+  color: var(--muted-foreground);
+}
+.chat-composer-send-spinner {
+  animation: chat-composer-spin 0.8s linear infinite;
+}
+@keyframes chat-composer-spin {
+  from {
+    transform: rotate(0deg);
+  }
+  to {
+    transform: rotate(360deg);
+  }
+}
+@media (prefers-reduced-motion: reduce) {
+  .chat-composer-send-spinner {
+    animation-duration: 1e-6ms;
+  }
 }
 
 /* A workbench room: a left info column (activity, artifacts, approvals,
diff --git a/apps/web/src/chat/composer.tsx b/apps/web/src/chat/composer.tsx
new file mode 100644
index 0000000000..93f12ef248
--- /dev/null
+++ b/apps/web/src/chat/composer.tsx
@@ -0,0 +1,63 @@
+// The one composer surface for a chat thread and a workbench room alike:
+// Enter sends, Shift+Enter inserts a newline, and a right-hand action rail
+// carries Send. There is no Stop action — neither `threads-api.ts` nor the
+// hub API expose a way to cancel a running turn, so cancellation is not
+// wired up here; add it to this rail once that capability exists upstream.
+import { ArrowUp, CircleNotch } from "@/lib/icons";
+import { useState } from "react";
+
+export function Composer({
+  placeholder,
+  busy,
+  disabled,
+  onSend,
+}: {
+  readonly placeholder: string;
+  readonly busy: boolean;
+  readonly disabled?: boolean;
+  readonly onSend: (text: string) => void;
+}) {
+  const [text, setText] = useState("");
+  const canSend = text.trim() !== "" && !busy && !disabled;
+  const send = () => {
+    const trimmed = text.trim();
+    if (trimmed === "" || busy || disabled) return;
+    setText("");
+    onSend(trimmed);
+  };
+  return (
+    <div className="chat-composer">
+      <textarea
+        className="chat-composer-input"
+        value={text}
+        rows={3}
+        placeholder={placeholder}
+        aria-label={placeholder}
+        disabled={disabled}
+        onChange={(event) => setText(event.target.value)}
+        onKeyDown={(event) => {
+          if (event.key === "Enter" && !event.shiftKey) {
+            event.preventDefault();
+            send();
+          }
+        }}
+      />
+      <div className="chat-composer-rail">
+        <button
+          type="button"
+          className="chat-composer-send"
+          disabled={!canSend}
+          onClick={send}
+          aria-label={busy ? "Sending…" : "Send"}
+          title={busy ? "Sending…" : "Send"}
+        >
+          {busy ? (
+            <CircleNotch className="chat-composer-send-spinner" aria-hidden="true" />
+          ) : (
+            <ArrowUp aria-hidden="true" />
+          )}
+        </button>
+      </div>
+    </div>
+  );
+}
diff --git a/apps/web/src/pages/chat-thread-page.tsx b/apps/web/src/pages/chat-thread-page.tsx
index d0320b7b29..4323a516a8 100644
--- a/apps/web/src/pages/chat-thread-page.tsx
+++ b/apps/web/src/pages/chat-thread-page.tsx
@@ -2,11 +2,12 @@
 // first message (agent picked in the select, or by @tagging one in the
 // message itself); `/chats/:id` is the transcript plus a reply box.
 
-import { Button, EmptyState, PageShell, Select, Textarea } from "@corbits/react-ui";
+import { Button, EmptyState, PageShell, Select } from "@corbits/react-ui";
 import { WarningCircle } from "@/lib/icons";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { useEffect, useMemo, useState } from "react";
 
+import { Composer } from "@/chat/composer";
 import { Markdown } from "@/chat/markdown";
 import {
   agentFromMention,
@@ -26,47 +27,6 @@ function errorText(cause: unknown): string {
   return cause instanceof Error ? cause.message : String(cause);
 }
 
-function Composer({
-  placeholder,
-  busy,
-  disabled,
-  onSend,
-}: {
-  readonly placeholder: string;
-  readonly busy: boolean;
-  readonly disabled?: boolean;
-  readonly onSend: (text: string) => void;
-}) {
-  const [text, setText] = useState("");
-  const send = () => {
-    const trimmed = text.trim();
-    if (trimmed === "" || busy || disabled) return;
-    setText("");
-    onSend(trimmed);
-  };
-  return (
-    <div className="chat-composer">
-      <Textarea
-        value={text}
-        rows={3}
-        placeholder={placeholder}
-        aria-label={placeholder}
-        disabled={disabled}
-        onChange={(event) => setText(event.target.value)}
-        onKeyDown={(event) => {
-          if (event.key === "Enter" && !event.shiftKey) {
-            event.preventDefault();
-            send();
-          }
-        }}
-      />
-      <Button variant="primary" disabled={busy || disabled || text.trim() === ""} onClick={send}>
-        {busy ? "Sending…" : "Send"}
-      </Button>
-    </div>
-  );
-}
-
 function NewChat({
   tenantId,
   navigate,
diff --git a/apps/web/src/pages/workbench-room-page.tsx b/apps/web/src/pages/workbench-room-page.tsx
index 78336385fb..2d42a7b49d 100644
--- a/apps/web/src/pages/workbench-room-page.tsx
+++ b/apps/web/src/pages/workbench-room-page.tsx
@@ -11,7 +11,6 @@ import {
   EmptyState,
   PageShell,
   Skeleton,
-  Textarea,
   formatRelativeTime,
   toast,
 } from "@corbits/react-ui";
@@ -19,6 +18,7 @@ import { WarningCircle } from "@/lib/icons";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { useEffect, useRef, useState } from "react";
 
+import { Composer } from "@/chat/composer";
 import { Markdown } from "@/chat/markdown";
 import {
   agentInitials,
@@ -45,47 +45,6 @@ function errorText(cause: unknown): string {
   return cause instanceof Error ? cause.message : String(cause);
 }
 
-function RoomComposer({
-  placeholder,
-  busy,
-  disabled,
-  onSend,
-}: {
-  readonly placeholder: string;
-  readonly busy: boolean;
-  readonly disabled?: boolean;
-  readonly onSend: (text: string) => void;
-}) {
-  const [text, setText] = useState("");
-  const send = () => {
-    const trimmed = text.trim();
-    if (trimmed === "" || busy || disabled) return;
-    setText("");
-    onSend(trimmed);
-  };
-  return (
-    <div className="chat-composer">
-      <Textarea
-        value={text}
-        rows={3}
-        placeholder={placeholder}
-        aria-label={placeholder}
-        disabled={disabled}
-        onChange={(event) => setText(event.target.value)}
-        onKeyDown={(event) => {
-          if (event.key === "Enter" && !event.shiftKey) {
-            event.preventDefault();
-            send();
-          }
-        }}
-      />
-      <Button variant="primary" disabled={busy || disabled || text.trim() === ""} onClick={send}>
-        {busy ? "Sending…" : "Send"}
-      </Button>
-    </div>
-  );
-}
-
 function RoomMessageRow({
   message,
   participants,
@@ -417,7 +376,7 @@ function Room({ roomTenantId }: { readonly roomTenantId: string }) {
           </div>
           <div className="room-main-composer">
             <PageShell width="prose" className="page-fill">
-              <RoomComposer
+              <Composer
                 placeholder={
                   startingAgent === undefined
                     ? "Message this workbench"
@@ -447,7 +406,7 @@ function Room({ roomTenantId }: { readonly roomTenantId: string }) {
                 />
               ))}
             </div>
-            <RoomComposer
+            <Composer
               placeholder={
                 startingAgent === undefined
                   ? "Reply in this thread"