diff --git a/frontend/packages/agent/src/Root.tsx b/frontend/packages/agent/src/Root.tsx
index b586c428..d18c7546 100644
--- a/frontend/packages/agent/src/Root.tsx
+++ b/frontend/packages/agent/src/Root.tsx
@@ -11,6 +11,7 @@ import { useApplyThemeOverride } from '@hive/shared/theme-apply.js';
 import { useApplyMotionOverride } from '@hive/shared/motion-apply.js';
 import { Header } from './components/Header.js';
 import { MetaNav } from './components/MetaNav.js';
+import { ExpandDetailsSetting } from './components/ExpandDetailsSetting.js';
 import { StatusChips } from './components/StatusChips.js';
 import { LiveStream, type LiveStreamHandle } from './components/LiveStream.js';
 import { HeaderPill } from './components/HeaderPill.js';
@@ -113,7 +114,9 @@ export function Root() {
           dashboardBase={resolveDashboardBase(state.dashboard_port)}
         />
       ) : null}
-      <SettingsMenu themeKey={THEME_KEY} motionKey={MOTION_KEY} />
+      <SettingsMenu themeKey={THEME_KEY} motionKey={MOTION_KEY}>
+        <ExpandDetailsSetting />
+      </SettingsMenu>
     </>
   );
   // Kept mounted regardless of `openPanel` (open/closed toggles just the
diff --git a/frontend/packages/agent/src/components/ExpandDetailsSetting.tsx b/frontend/packages/agent/src/components/ExpandDetailsSetting.tsx
new file mode 100644
index 00000000..3a7a939b
--- /dev/null
+++ b/frontend/packages/agent/src/components/ExpandDetailsSetting.tsx
@@ -0,0 +1,35 @@
+// Agent-terminal-only settings-menu row: "expand tool output panels".
+// Rendered as a `<SettingsMenu>` child (`@hive/shared/settings-menu.js`)
+// rather than a prop on that shared component — `SettingsMenu` is also
+// used by swarm-ui, which has no terminal to apply this to, and a prior
+// attempt to gate it behind a boolean prop (`showExpandDetails`) on the
+// shared component drew mara's review: "you cannot just add it like
+// this - if we have more and more options there in different places we
+// will keep accumulating cruft in the shared component." This file owns
+// its own state/storage entirely; `SettingsMenu` just renders it as a
+// child, no different from any other consumer's markup.
+import { useState } from 'preact/hooks';
+import { getExpandDetailsPref, setExpandDetailsPref } from '@hive/shared/prefs.js';
+
+export function ExpandDetailsSetting() {
+  // Plain localStorage read, not a hook-managed override like
+  // theme/motion — `getExpandDetailsPref`/`setExpandDetailsPref`
+  // (`@hive/shared/prefs.js`) are the existing shared-storage-key pair
+  // the terminal itself already reads live (no round-trip needed here
+  // beyond re-rendering this row's own checkbox state on toggle).
+  const [expandDetails, setExpandDetailsState] = useState(() => getExpandDetailsPref());
+  return (
+    <label class="settings-menu-row">
+      <span>expand tool output</span>
+      <input
+        type="checkbox"
+        checked={expandDetails}
+        onChange={(e) => {
+          const v = (e.target as HTMLInputElement).checked;
+          setExpandDetailsPref(v);
+          setExpandDetailsState(v);
+        }}
+      />
+    </label>
+  );
+}
diff --git a/frontend/packages/agent/src/lib/classifyEvent.ts b/frontend/packages/agent/src/lib/classifyEvent.ts
index 07aa5784..48d49544 100644
--- a/frontend/packages/agent/src/lib/classifyEvent.ts
+++ b/frontend/packages/agent/src/lib/classifyEvent.ts
@@ -15,6 +15,7 @@
 // text loses its client-side tick. Revisit if that's missed in practice.
 import type { StreamRow, StreamRowMeta } from './streamRow.js';
 import { fmtAge, fmtClock } from './format.js';
+import { getExpandDetailsPref } from '@hive/shared/prefs.js';
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any -- stream-json
 // content is dynamically-shaped JSON, same as app.js's untyped handling.
@@ -171,15 +172,23 @@ function classifyStream(v: AnyEvent, fromHistory: boolean, ctx: ClassifyCtx): St
 }
 
 // `_category === 'rich'` tools get an expandable row: diff body (Edit),
-// default-open markdown body (send/ask/answer/recv-shaped), or a plain
-// collapsed body — all pre-computed server-side, no per-tool JS needed.
+// default-open markdown body (send/ask/answer/recv-shaped, always open
+// regardless of the preference below — matches app.js), or a plain
+// body (collapsed unless the operator's "expand tool output" preference
+// says otherwise — @hive/shared/prefs.js's getExpandDetailsPref(), read
+// fresh per row so a mid-session preference change applies going
+// forward without a reload) — all pre-computed server-side, no per-tool
+// JS needed.
 function classifyToolUse(c: AnyEvent, fromHistory: boolean, ctx: ClassifyCtx): StreamRow {
   const icon = c._icon || '🔧';
   const name = c.name || '';
   if (c._category === 'rich' && c._body != null) {
     const summary = c._summary || name || '?';
     if (c._body_type === 'diff') {
-      return { key: nextKey(ctx), cssClass: 'tool-use', fromHistory, details: true, icon, text: summary, diffBody: c._body };
+      return {
+        key: nextKey(ctx), cssClass: 'tool-use', fromHistory, details: true, defaultOpen: getExpandDetailsPref(),
+        icon, text: summary, diffBody: c._body,
+      };
     }
     if (c._body_type === 'markdown') {
       return {
@@ -187,7 +196,10 @@ function classifyToolUse(c: AnyEvent, fromHistory: boolean, ctx: ClassifyCtx): S
         icon, text: summary, markdownBody: c._body,
       };
     }
-    return { key: nextKey(ctx), cssClass: 'tool-use', fromHistory, details: true, icon, text: summary, plainBody: c._body };
+    return {
+      key: nextKey(ctx), cssClass: 'tool-use', fromHistory, details: true, defaultOpen: getExpandDetailsPref(),
+      icon, text: summary, plainBody: c._body,
+    };
   }
   return { key: nextKey(ctx), cssClass: 'tool-use', fromHistory, icon, text: c._summary || name || '?' };
 }
@@ -214,7 +226,10 @@ function classifyToolResult(c: AnyEvent, fromHistory: boolean, ctx: ClassifyCtx)
     if (!txt.trim() || txt.length <= 120) {
       return { key: nextKey(ctx), cssClass: 'tool-result error', fromHistory, text: '✗  ' + summaryBody };
     }
-    return { key: nextKey(ctx), cssClass: 'tool-result-block error', fromHistory, details: true, text: summaryBody, plainBody: txt };
+    return {
+      key: nextKey(ctx), cssClass: 'tool-result-block error', fromHistory, details: true,
+      defaultOpen: getExpandDetailsPref(), text: summaryBody, plainBody: txt,
+    };
   }
   if (isMessageBearing && txt.trim()) {
     return {
@@ -225,7 +240,10 @@ function classifyToolResult(c: AnyEvent, fromHistory: boolean, ctx: ClassifyCtx)
   if (!txt.trim() || txt.length <= 120) {
     return { key: nextKey(ctx), cssClass: 'tool-result', fromHistory, text: '←  ' + summaryBody };
   }
-  return { key: nextKey(ctx), cssClass: 'tool-result-block', fromHistory, details: true, text: summaryBody, plainBody: txt };
+  return {
+    key: nextKey(ctx), cssClass: 'tool-result-block', fromHistory, details: true,
+    defaultOpen: getExpandDetailsPref(), text: summaryBody, plainBody: txt,
+  };
 }
 
 // Subagent (claude `Task`-tool) activity — dead path for agents today
diff --git a/frontend/packages/dashboard/src/settings.html b/frontend/packages/dashboard/src/settings.html
index d1fd0fbd..a7ea4da1 100644
--- a/frontend/packages/dashboard/src/settings.html
+++ b/frontend/packages/dashboard/src/settings.html
@@ -32,11 +32,6 @@
       <span id="notif-status" class="meta" hidden></span>
     </div>
 
-    <h3>◇ agent terminal</h3>
-    <p class="meta">applies to every agent's terminal viewed in this browser — whether otherwise-collapsed tool-output panels (long results, Write/Edit diffs, …) default open. rows that already default open (send/ask/answer/recv) are unaffected either way.</p>
-    <div id="verbosity-row" class="notif-row">
-      <button type="button" id="expand-details-toggle" class="btn btn-notif" role="switch"></button>
-    </div>
   </main>
 
   <script type="module" src="/static/settings.js" defer></script>
diff --git a/frontend/packages/dashboard/src/settings.js b/frontend/packages/dashboard/src/settings.js
index aad5c1e6..298378d1 100644
--- a/frontend/packages/dashboard/src/settings.js
+++ b/frontend/packages/dashboard/src/settings.js
@@ -7,31 +7,9 @@
 // browser-level permission, so firing still works from the dashboard
 // even though the toggle UI now lives on its own page.
 //
-// The agent-terminal-verbosity toggle below is a second, unrelated
-// browser-local preference — @hive/shared/prefs.js owns the key name +
-// get/set so this page and every per-agent page's app.js agree on it
-// without a backend field. Both preferences are per-origin localStorage,
-// so they only apply within this browser (per the page's own copy).
-//
 // initServerWarnings() renders the shared top-of-page warnings banner,
 // matching the other stand-alone pages (FL0W / L0GS / H0M3).
 import { NOTIF, initServerWarnings } from './common.js';
-import { getExpandDetailsPref, setExpandDetailsPref } from '@hive/shared/prefs.js';
 
 initServerWarnings();
 NOTIF.bind();
-
-(function bindExpandDetailsToggle() {
-  const btn = document.getElementById('expand-details-toggle');
-  if (!btn) return;
-  function render() {
-    const on = getExpandDetailsPref();
-    btn.textContent = on ? '☑ expand tool output panels' : '☐ expand tool output panels';
-    btn.setAttribute('aria-checked', String(on));
-  }
-  btn.addEventListener('click', () => {
-    setExpandDetailsPref(!getExpandDetailsPref());
-    render();
-  });
-  render();
-})();
diff --git a/frontend/packages/shared/package.json b/frontend/packages/shared/package.json
index 69b3859d..6f157263 100644
--- a/frontend/packages/shared/package.json
+++ b/frontend/packages/shared/package.json
@@ -21,7 +21,7 @@
     "./chrome.css": "./src/chrome.css",
     "./pill.css": "./src/pill.css",
     "./forms.js": "./src/forms.js",
-    "./prefs.js": "./src/prefs.js",
+    "./prefs.js": "./src/prefs.ts",
     "./dom.js": "./src/dom.js",
     "./modal.js": "./src/modal.js",
     "./shadow-css.js": "./src/shadow-css.js",
diff --git a/frontend/packages/shared/src/prefs.js b/frontend/packages/shared/src/prefs.ts
similarity index 71%
rename from frontend/packages/shared/src/prefs.js
rename to frontend/packages/shared/src/prefs.ts
index f73fb005..de4fa5bf 100644
--- a/frontend/packages/shared/src/prefs.js
+++ b/frontend/packages/shared/src/prefs.ts
@@ -13,15 +13,20 @@ const EXPAND_DETAILS_KEY = 'hive-agent-expand-details';
 // client-side — no backend field, nothing round-trips through
 // `/api/*`. Read live (not cached) by the shared terminal factory's
 // `expandDetails` option — see docs/web-ui/shape.md::Shared terminal
-// pane — so a preference change on /settings.html applies to the next
-// rendered row in any already-open agent tab without a reload.
-export function getExpandDetailsPref() {
-  try { return localStorage.getItem(EXPAND_DETAILS_KEY) === '1'; }
-  catch { return false; }
+// pane — so a preference change applies to the next rendered row in
+// any already-open agent tab without a reload.
+export function getExpandDetailsPref(): boolean {
+  try {
+    return localStorage.getItem(EXPAND_DETAILS_KEY) === '1';
+  } catch {
+    return false;
+  }
 }
-export function setExpandDetailsPref(v) {
+export function setExpandDetailsPref(v: boolean): void {
   try {
     if (v) localStorage.setItem(EXPAND_DETAILS_KEY, '1');
     else localStorage.removeItem(EXPAND_DETAILS_KEY);
-  } catch { /* localStorage unavailable — preference is session-only */ }
+  } catch {
+    /* localStorage unavailable — preference is session-only */
+  }
 }
diff --git a/frontend/packages/shared/src/settings/SettingsMenu.tsx b/frontend/packages/shared/src/settings/SettingsMenu.tsx
index ac643132..233d5677 100644
--- a/frontend/packages/shared/src/settings/SettingsMenu.tsx
+++ b/frontend/packages/shared/src/settings/SettingsMenu.tsx
@@ -24,6 +24,7 @@
 // component, so the two stay in sync without this component owning any
 // page-specific naming decision.
 import { useEffect, useRef, useState } from 'preact/hooks';
+import type { ComponentChildren } from 'preact';
 import { Badge } from '../badge/Badge.js';
 import { GearIcon } from '../icons.js';
 import { useThemeOverride, type ThemeOverride } from './theme-apply.js';
@@ -36,9 +37,21 @@ const MOTION_OPTIONS: MotionOverride[] = ['system', 'allow', 'reduce'];
 export interface SettingsMenuProps {
   themeKey: string;
   motionKey: string;
+  /**
+   * Consumer-owned extra row(s), rendered inside the popover after the
+   * built-in theme/motion rows. Not a named boolean prop per setting —
+   * a `showExpandDetails?: boolean` attempt drew mara's review: "you
+   * cannot just add it like this - if we have more and more options
+   * there in different places we will keep accumulating cruft in the
+   * shared component." A caller owns its row(s) entirely (state,
+   * storage key, markup); this component never learns they exist. Use
+   * `settings-menu-row` (this file's CSS) on each row's outer element
+   * to match spacing/typography — see `Root.tsx` for a worked example.
+   */
+  children?: ComponentChildren;
 }
 
-export function SettingsMenu({ themeKey, motionKey }: SettingsMenuProps) {
+export function SettingsMenu({ themeKey, motionKey, children }: SettingsMenuProps) {
   const [open, setOpen] = useState(false);
   const rootRef = useRef<HTMLDivElement>(null);
   const [theme, setTheme] = useThemeOverride(themeKey);
@@ -98,6 +111,7 @@ export function SettingsMenu({ themeKey, motionKey }: SettingsMenuProps) {
               ))}
             </select>
           </label>
+          {children}
         </div>
       ) : null}
     </div>