fix(desktop): clear stale compaction status across session switches (#64127)

* fix(desktop): clear stale compaction status

Clear the compaction phase when a turn resumes with model or tool activity, and key response timers by session and turn so switching chats preserves elapsed time.\n\nSupersedes #48115 by porting its resumed-content approach to the current split stream hook and covering tool-first resumptions.\n\nCo-authored-by: liuhao1024 <sunsky.lau@gmail.com>

* fix(desktop): resume after thinking activity

* fix(desktop): clear turn timer on stop

apps/desktop/src/app/session/hooks/use-message-stream/compaction-event.test.tsx

@@ -0,0 +1,82 @@
+import { QueryClient } from '@tanstack/react-query'
+import { act, cleanup, render, waitFor } from '@testing-library/react'
+import { useEffect, useRef } from 'react'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import type { ClientSessionState } from '@/app/types'
+import { createClientSessionState } from '@/lib/chat-runtime'
+import { $compactingSessions, setSessionCompacting } from '@/store/compaction'
+import type { RpcEvent } from '@/types/hermes'
+
+import { useMessageStream } from './index'
+
+const SID = 'session-1'
+const OTHER_SID = 'session-2'
+let handleEvent: ((event: RpcEvent) => void) | null = null
+
+function Harness() {
+  const activeSessionIdRef = useRef<string | null>(SID)
+  const sessionStateByRuntimeIdRef = useRef(new Map<string, ClientSessionState>())
+  const queryClientRef = useRef(new QueryClient())
+
+  const stream = useMessageStream({
+    activeSessionIdRef,
+    hydrateFromStoredSession: vi.fn(async () => undefined),
+    queryClient: queryClientRef.current,
+    refreshHermesConfig: vi.fn(async () => undefined),
+    refreshSessions: vi.fn(async () => undefined),
+    sessionStateByRuntimeIdRef,
+    updateSessionState: (sessionId, updater) => {
+      const current = sessionStateByRuntimeIdRef.current.get(sessionId) ?? createClientSessionState()
+      const next = updater(current)
+      sessionStateByRuntimeIdRef.current.set(sessionId, next)
+
+      return next
+    }
+  })
+
+  useEffect(() => {
+    handleEvent = stream.handleGatewayEvent
+  }, [stream.handleGatewayEvent])
+
+  return null
+}
+
+async function mountStream() {
+  render(<Harness />)
+  await waitFor(() => expect(handleEvent).not.toBeNull())
+}
+
+function emit(type: RpcEvent['type'], payload: RpcEvent['payload'] = {}) {
+  act(() => handleEvent!({ payload, session_id: SID, type }))
+}
+
+describe('useMessageStream compaction lifecycle', () => {
+  beforeEach(() => {
+    handleEvent = null
+    $compactingSessions.set({})
+  })
+
+  afterEach(() => {
+    cleanup()
+    $compactingSessions.set({})
+    vi.restoreAllMocks()
+  })
+
+  it.each([
+    ['message.delta', { text: 'resumed' }],
+    ['thinking.delta', { text: 'still working' }],
+    ['reasoning.delta', { text: 'thinking again' }],
+    ['tool.start', { name: 'terminal', tool_id: 'tool-1' }]
+  ] as const)('clears the stale compaction phase when %s resumes the turn', async (type, payload) => {
+    await mountStream()
+    setSessionCompacting(OTHER_SID, true)
+
+    emit('status.update', { kind: 'compacting' })
+    expect($compactingSessions.get()).toEqual({ [OTHER_SID]: true, [SID]: true })
+
+    emit(type, payload)
+
+    expect($compactingSessions.get()).toEqual({ [OTHER_SID]: true })
+  })
+})

apps/desktop/src/app/session/hooks/use-message-stream/gateway-event.ts

@@ -50,6 +50,19 @@ import type { ClientSessionState } from '../../../types'
 
 import { hasSessionInfoStatePatch, sessionInfoStatePatch, SUBAGENT_EVENT_TYPES, toTodoPayload } from './utils'
 
+const COMPACTION_RESUME_EVENT_TYPES = new Set([
+  'message.delta',
+  'thinking.delta',
+  'reasoning.delta',
+  'reasoning.available',
+  'moa.reference',
+  'moa.aggregating',
+  'tool.start',
+  'tool.progress',
+  'tool.generating',
+  'tool.complete'
+])
+
 interface GatewayEventDeps {
   activeSessionIdRef: MutableRefObject<string | null>
   compactedTurnRef: MutableRefObject<Set<string>>
@@ -118,6 +131,18 @@ export function useGatewayEventHandler(deps: GatewayEventDeps) {
       const sessionId = route.sessionId
       const isActiveEvent = !!sessionId && sessionId === activeSessionIdRef.current
 
+      // Mid-turn compaction does not emit another message.start. The first
+      // model output or tool event proves summarization has finished and the
+      // turn has resumed, so retire the phase label without waiting for the
+      // whole turn to complete.
+      if (
+        sessionId &&
+        COMPACTION_RESUME_EVENT_TYPES.has(event.type) &&
+        compactedTurnRef.current.has(sessionId)
+      ) {
+        setSessionCompacting(sessionId, false)
+      }
+
       if (event.type === 'gateway.ready') {
         return
       } else if (event.type === 'session.info') {

apps/desktop/src/app/session/hooks/use-prompt-actions/index.test.tsx

@@ -5,7 +5,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { textPart } from '@/lib/chat-messages'
 import { $composerAttachments, $composerDraft, type ComposerAttachment, setComposerDraft } from '@/store/composer'
-import { $busy, $connection, $messages, $sessions, setSessions } from '@/store/session'
+import { $busy, $connection, $messages, $sessions, $turnStartedAt, setSessions } from '@/store/session'
 import type { SessionInfo } from '@/types/hermes'
 
 import { uploadComposerAttachment, usePromptActions } from '.'
@@ -1075,6 +1075,7 @@ describe('usePromptActions sleep/wake session recovery', () => {
 
   afterEach(() => {
     cleanup()
+    $turnStartedAt.set(null)
     vi.restoreAllMocks()
   })
 
@@ -1168,6 +1169,32 @@ describe('usePromptActions sleep/wake session recovery', () => {
     expect(calls[2]?.params).toEqual({ session_id: RECOVERED_SESSION_ID })
   })
 
+  it('clears the active and cached turn clocks when stopping a turn', async () => {
+    const states: Record<string, unknown>[] = []
+    const requestGateway = vi.fn(async () => ({}) as never)
+    $turnStartedAt.set(1_700_000_000_000)
+
+    let handle: HarnessHandle | null = null
+    await actRender(
+      <Harness
+        onReady={h => (handle = h)}
+        onSeedState={state => states.push(state)}
+        refreshSessions={async () => undefined}
+        requestGateway={requestGateway}
+      />
+    )
+
+    await handle!.cancelRun()
+
+    expect($turnStartedAt.get()).toBeNull()
+    expect(states.at(-1)).toMatchObject({
+      awaitingResponse: false,
+      busy: false,
+      interrupted: true,
+      turnStartedAt: null
+    })
+  })
+
   it('surfaces the original error (no resume) when the failure is not "session not found"', async () => {
     const calls: string[] = []
     const states: Record<string, unknown>[] = []

apps/desktop/src/app/session/hooks/use-prompt-actions/index.ts

@@ -21,7 +21,15 @@ import { resetSessionBackground } from '@/store/composer-status'
 import { clearNotifications, notify, notifyError } from '@/store/notifications'
 import { clearPreviewArtifacts } from '@/store/preview-status'
 import { clearAllPrompts } from '@/store/prompts'
-import { $busy, $connection, $messages, setAwaitingResponse, setBusy, setMessages } from '@/store/session'
+import {
+  $busy,
+  $connection,
+  $messages,
+  setAwaitingResponse,
+  setBusy,
+  setMessages,
+  setTurnStartedAt
+} from '@/store/session'
 import { clearSessionSubagents } from '@/store/subagents'
 import { clearSessionTodos } from '@/store/todos'
 
@@ -501,6 +509,7 @@ export function usePromptActions({
     }
 
     setAwaitingResponse(false)
+    setTurnStartedAt(null)
 
     const finalizeMessages = (messages: ChatMessage[], streamId?: string | null) =>
       messages
@@ -526,7 +535,8 @@ export function usePromptActions({
         streamId: null,
         pendingBranchGroup: null,
         needsInput: false,
-        interrupted: true
+        interrupted: true,
+        turnStartedAt: null
       }
     })