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+# Running-Conversation Indicator — Design
+
+Date: 2026-08-12
+Status: Approved (approach A: wire existing infrastructure)
+
+## Goal
+
+A conversation whose run is executing gives no visual signal today. Add a
+lightweight pulsing "running" indicator in **two places**:
+
+1. **Thread list rows** — a dot next to the title of any thread with an active
+   run (including runs started by other tabs or scheduled tasks).
+2. **Global header** — a dot next to the logo/wordmark whenever the *currently
+   open* conversation is running, shown in **all views** (chat, Skills, Memory,
+   Schedule) so switching away doesn't hide that work is in flight.
+
+Decisions locked in during brainstorming:
+
+- **Style:** lightweight pulsing dot only — no banner text, no extra stop
+  button (the composer's stop affordance already exists).
+- **Approach:** wire up the already-built (but currently unconsumed) running
+  state infrastructure. No backend changes.
+
+## Existing infrastructure (why no backend work is needed)
+
+- `useChat.ts` already calls `setThreadRunning(threadId, isRunLoading)` on its
+  own run lifecycle — a zero-latency local store
+  (`useThreads.ts:99-126`, covered by `useThreads.running.test.ts`).
+- `useBusyThreadIds()` (`useThreads.ts:78-97`) polls
+  `/api/conversations?status=busy&limit=100` on a 10s heartbeat, covering runs
+  started out-of-band (other tabs, scheduled tasks).
+- Neither hook is consumed by any UI today — this feature is wiring + rendering.
+
+## Components
+
+### 1. `useRunningThreadIds()` — new hook in `src/app/hooks/useThreads.ts`
+
+Merges the two sources into one `ReadonlySet<string>`:
+
+```ts
+const local = useLocalRunningThreadIds();
+const busy = useBusyThreadIds();
+return useMemo(() => new Set([...busy, ...local]), [busy, local]);
+```
+
+Single call site per consumer; the merge is the only new logic. SWR dedupes
+the heartbeat request across multiple mounts, so calling this hook from both
+ThreadList and page.tsx is safe.
+
+### 2. `RunningDot` — new presentational component
+
+`src/app/components/RunningDot.tsx`. Standard ping pattern:
+
+- outer `span.relative.flex.size-2` with `role="status"`, i18n `aria-label`
+  and `title`;
+- inner `animate-ping absolute inline-flex h-full w-full rounded-full bg-blue-500 opacity-75`;
+- inner solid `relative inline-flex size-2 rounded-full bg-blue-500`.
+
+Blue matches the existing `STATUS_COLORS.busy` in ThreadList. The component
+takes the translated label as a prop so callers use their own i18n domain.
+
+### 3. Thread list row (`src/app/components/ThreadList.tsx`)
+
+- Call `useRunningThreadIds()` once at the top of `ThreadList`.
+- In `renderThreadCard`, render `<RunningDot />` inside the title `<h3>`,
+  after the pin icon and before the title text, when
+  `runningIds.has(thread.id)`.
+
+### 4. Global header (`src/app/[locale]/page.tsx`)
+
+- Call `useRunningThreadIds()` in `HomePageInner`.
+- Render `<RunningDot />` in the header's left cluster (after the logo/wordmark
+  block) when `threadId && runningIds.has(threadId)`.
+- No view gating: the dot shows in every view while the open thread runs.
+
+## i18n
+
+One new message per domain, both locales:
+
+- `threadList.running` — e.g. en "Running", zh "正在执行" (used by the row dot).
+- `header.running` — same text (used by the header dot).
+
+## Error handling
+
+Nothing new. A failed busy heartbeat yields an empty busy set (dot hides until
+the next successful poll); the local store still covers this client's own runs,
+so the common case never regresses on a heartbeat failure.
+
+## Testing
+
+- Extend the pattern of `useThreads.running.test.ts` with a unit test for
+  `useRunningThreadIds`: local-only, busy-only, and merged membership.
+- Existing suites (`useThreads.running.test.ts`, tsc, eslint) must stay green.
+
+## Out of scope
+
+- Banner/text prompts, header stop button.
+- Push/SSE real-time busy events (10s heartbeat is sufficient).
+- Per-row indicators for `interrupted`/`error` status (already surfaced via the
+  "Requiring Attention" group and status filter).