diff --git a/src/renderer/src/hooks/agent-hook-completion-notifications.test.ts b/src/renderer/src/hooks/agent-hook-completion-notifications.test.ts
index 3fa220ffaff..75487c039b9 100644
--- a/src/renderer/src/hooks/agent-hook-completion-notifications.test.ts
+++ b/src/renderer/src/hooks/agent-hook-completion-notifications.test.ts
@@ -824,6 +824,37 @@ describe('agent hook completion notifications', () => {
     expect(_getAgentHookCompletionNotificationCoordinatorCountForTest()).toBe(3)
   })
 
+  it('gates cosmetic store updates but still prunes after a pane closes', async () => {
+    const {
+      _getAgentHookCompletionNotificationCoordinatorCountForTest,
+      observeAgentHookCompletionForNotification,
+      syncAgentHookCompletionNotificationsForStoreUpdate
+    } = await import('./agent-hook-completion-notifications')
+
+    observeAgentHookCompletionForNotification({
+      paneKey,
+      worktreeId: 'wt-1',
+      payload: hookStatus('working')
+    })
+
+    const beforeCosmeticUpdate = { ...mockStoreState }
+    mockStoreState.tabsByWorktree = {
+      'wt-1': [{ id: 'tab-1', ptyId: 'pty-1' }]
+    }
+    expect(
+      syncAgentHookCompletionNotificationsForStoreUpdate(mockStoreState, beforeCosmeticUpdate)
+    ).toBe(false)
+    expect(_getAgentHookCompletionNotificationCoordinatorCountForTest()).toBe(1)
+
+    const beforeClose = { ...mockStoreState }
+    mockStoreState.tabsByWorktree = { 'wt-1': [] }
+    mockStoreState.ptyIdsByTabId = {}
+    expect(syncAgentHookCompletionNotificationsForStoreUpdate(mockStoreState, beforeClose)).toBe(
+      true
+    )
+    expect(_getAgentHookCompletionNotificationCoordinatorCountForTest()).toBe(0)
+  })
+
   it('skips tab scans until a pane-liveness slice changes', async () => {
     seedManyLivePanes()
     const {
diff --git a/src/renderer/src/hooks/agent-hook-completion-notifications.ts b/src/renderer/src/hooks/agent-hook-completion-notifications.ts
index 0154d5d0d4a..125c0994514 100644
--- a/src/renderer/src/hooks/agent-hook-completion-notifications.ts
+++ b/src/renderer/src/hooks/agent-hook-completion-notifications.ts
@@ -10,6 +10,10 @@ import { dispatchTerminalNotification } from '@/components/terminal-pane/use-not
 import { collectLeafIdsInOrder } from '@/components/terminal-pane/layout-serialization'
 import { createCodexAutoApprovalHookCompletionSuppressor } from '@/components/terminal-pane/codex-auto-approval-notification-suppression'
 import { dispatchAgentHookTerminalLifecycle } from '@/components/terminal-pane/agent-hook-terminal-lifecycle'
+import {
+  shouldSyncAgentHookCompletionForStoreUpdate,
+  type AgentHookCompletionStoreSnapshot
+} from './agent-hook-completion-store-sync'
 
 type CoordinatorEntry = {
   worktreeId: string
@@ -19,7 +23,8 @@ type CoordinatorEntry = {
 type StoreSnapshot = ReturnType<typeof useAppStore.getState>
 type WorktreeTab = NonNullable<StoreSnapshot['tabsByWorktree']>[string][number]
 // Why: a paneKey resolves to a tab by id. Prebuilding this index once per prune
-// pass avoids re-flattening tabsByWorktree per coordinator (O(coordinators x tabs)).
+// pass avoids re-flattening tabsByWorktree per coordinator (O(coordinators x
+// tabs)) when a liveness or notification-setting update requires a prune.
 type TabIndex = ReadonlyMap<string, WorktreeTab>
 type PaneCoordinatorLivenessSnapshot = Pick<
   StoreSnapshot,
@@ -119,6 +124,19 @@ export function syncAgentHookCompletionNotificationSettings(): boolean {
   return enabled
 }
 
+export function syncAgentHookCompletionNotificationsForStoreUpdate(
+  current: AgentHookCompletionStoreSnapshot,
+  previous: AgentHookCompletionStoreSnapshot
+): boolean {
+  // Why: Zustand also publishes high-rate title/status writes that cannot make
+  // module-scoped completion coordinators stale.
+  if (!shouldSyncAgentHookCompletionForStoreUpdate(current, previous)) {
+    return false
+  }
+  syncAgentHookCompletionNotificationSettings()
+  return true
+}
+
 function getPtyIdForPaneKey(paneKey: string): string | null {
   const parsed = parsePaneKey(paneKey)
   if (!parsed) {
diff --git a/src/renderer/src/hooks/agent-hook-completion-store-sync.test.ts b/src/renderer/src/hooks/agent-hook-completion-store-sync.test.ts
new file mode 100644
index 00000000000..de1f22eca11
--- /dev/null
+++ b/src/renderer/src/hooks/agent-hook-completion-store-sync.test.ts
@@ -0,0 +1,190 @@
+import { describe, expect, it } from 'vitest'
+import {
+  _measureAgentHookCompletionStoreSyncForTest,
+  shouldSyncAgentHookCompletionForStoreUpdate,
+  type AgentHookCompletionStoreSnapshot
+} from './agent-hook-completion-store-sync'
+
+function createState(
+  overrides: Partial<AgentHookCompletionStoreSnapshot> = {}
+): AgentHookCompletionStoreSnapshot {
+  return {
+    settings: {
+      experimentalTerminalAttention: false,
+      notifications: { enabled: true, agentTaskComplete: true }
+    },
+    tabsByWorktree: {
+      'wt-1': [{ id: 'tab-1', ptyId: 'pty-1', title: 'Terminal 1' }]
+    },
+    ptyIdsByTabId: { 'tab-1': ['pty-1'] },
+    terminalLayoutsByTabId: {},
+    suppressedPtyExitIds: {},
+    ...overrides
+  }
+}
+
+describe('agent hook completion store sync', () => {
+  it('ignores unrelated and title-only writes at accumulated-workspace scale', () => {
+    const tabCount = 100
+    const coordinatorCount = 100
+    const updateCount = 600
+    const tabsByWorktree = Object.fromEntries(
+      Array.from({ length: tabCount }, (_, index) => [
+        `wt-${index}`,
+        [{ id: `tab-${index}`, ptyId: `pty-${index}`, title: `Terminal ${index}` }]
+      ])
+    )
+    let previous = createState({ tabsByWorktree })
+    let syncPasses = 0
+    let tabVisits = 0
+
+    for (let index = 0; index < updateCount; index += 1) {
+      const current = { ...previous }
+      const measurement = _measureAgentHookCompletionStoreSyncForTest(current, previous)
+      syncPasses += Number(measurement.shouldSync)
+      tabVisits += measurement.tabVisits
+      previous = current
+    }
+
+    for (let index = 0; index < updateCount; index += 1) {
+      const targetTabs = previous.tabsByWorktree['wt-99']
+      if (!targetTabs) {
+        throw new Error('Expected title-update fixture tab')
+      }
+      const current = createState({
+        ...previous,
+        tabsByWorktree: {
+          ...previous.tabsByWorktree,
+          'wt-99': targetTabs.map((tab) => ({ ...tab, title: `Agent frame ${index}` }))
+        }
+      })
+      const measurement = _measureAgentHookCompletionStoreSyncForTest(current, previous)
+      syncPasses += Number(measurement.shouldSync)
+      tabVisits += measurement.tabVisits
+      previous = current
+    }
+
+    const previousFullPassCost = {
+      tabVisits: updateCount * 2 * tabCount,
+      coordinatorVisits: updateCount * 2 * coordinatorCount
+    }
+    const gatedCost = {
+      tabVisits,
+      coordinatorVisits: syncPasses * coordinatorCount
+    }
+    expect(previousFullPassCost).toEqual({ tabVisits: 120_000, coordinatorVisits: 120_000 })
+    expect(gatedCost).toEqual({ tabVisits: 600, coordinatorVisits: 0 })
+  })
+
+  it('keeps every coordinator-liveness input reactive', () => {
+    const previous = createState()
+    const titleOnly = createState({
+      ...previous,
+      tabsByWorktree: {
+        'wt-1': [{ id: 'tab-1', ptyId: 'pty-1', title: 'Codex working' }]
+      }
+    })
+    expect(shouldSyncAgentHookCompletionForStoreUpdate(titleOnly, previous)).toBe(false)
+
+    const tabCreated = createState({
+      ...previous,
+      tabsByWorktree: {
+        ...previous.tabsByWorktree,
+        'wt-2': [{ id: 'tab-2', ptyId: null }]
+      }
+    })
+    expect(shouldSyncAgentHookCompletionForStoreUpdate(tabCreated, previous)).toBe(true)
+
+    const tabRemoved = createState({ ...previous, tabsByWorktree: {} })
+    expect(shouldSyncAgentHookCompletionForStoreUpdate(tabRemoved, previous)).toBe(true)
+
+    const tabPtyChanged = createState({
+      ...previous,
+      tabsByWorktree: { 'wt-1': [{ id: 'tab-1', ptyId: 'pty-2' }] }
+    })
+    expect(shouldSyncAgentHookCompletionForStoreUpdate(tabPtyChanged, previous)).toBe(true)
+
+    expect(
+      shouldSyncAgentHookCompletionForStoreUpdate(
+        createState({ ...previous, ptyIdsByTabId: { 'tab-1': ['pty-2'] } }),
+        previous
+      )
+    ).toBe(true)
+    expect(
+      shouldSyncAgentHookCompletionForStoreUpdate(
+        createState({ ...previous, terminalLayoutsByTabId: { 'tab-1': { root: null } } }),
+        previous
+      )
+    ).toBe(true)
+    expect(
+      shouldSyncAgentHookCompletionForStoreUpdate(
+        createState({ ...previous, suppressedPtyExitIds: { 'pty-1': true } }),
+        previous
+      )
+    ).toBe(true)
+
+    const trackingDisabled = createState({
+      ...previous,
+      settings: {
+        experimentalTerminalAttention: false,
+        notifications: { enabled: false, agentTaskComplete: false }
+      }
+    })
+    expect(shouldSyncAgentHookCompletionForStoreUpdate(trackingDisabled, previous)).toBe(true)
+  })
+
+  it('treats tab order and duplicate-id worktree precedence as liveness inputs', () => {
+    const previous = createState({
+      tabsByWorktree: {
+        'wt-1': [{ id: 'tab-shared', ptyId: 'pty-first' }],
+        'wt-2': [{ id: 'tab-shared', ptyId: 'pty-second' }]
+      }
+    })
+    const reorderedWorktrees = createState({
+      ...previous,
+      tabsByWorktree: {
+        'wt-2': previous.tabsByWorktree['wt-2'] ?? [],
+        'wt-1': previous.tabsByWorktree['wt-1'] ?? []
+      }
+    })
+    expect(shouldSyncAgentHookCompletionForStoreUpdate(reorderedWorktrees, previous)).toBe(true)
+
+    const twoTabPrevious = createState({
+      tabsByWorktree: {
+        'wt-1': [
+          { id: 'tab-1', ptyId: 'pty-1' },
+          { id: 'tab-2', ptyId: 'pty-2' }
+        ]
+      }
+    })
+    const reorderedTabs = createState({
+      ...twoTabPrevious,
+      tabsByWorktree: {
+        'wt-1': [
+          { id: 'tab-2', ptyId: 'pty-2' },
+          { id: 'tab-1', ptyId: 'pty-1' }
+        ]
+      }
+    })
+    expect(shouldSyncAgentHookCompletionForStoreUpdate(reorderedTabs, twoTabPrevious)).toBe(true)
+  })
+
+  it('compares effective tracking state instead of unrelated settings identity', () => {
+    const previous = createState({
+      settings: {
+        experimentalTerminalAttention: true,
+        notifications: { enabled: false, agentTaskComplete: false }
+      }
+    })
+    const stillTrackedByNotifications = createState({
+      ...previous,
+      settings: {
+        experimentalTerminalAttention: false,
+        notifications: { enabled: true, agentTaskComplete: true }
+      }
+    })
+    expect(shouldSyncAgentHookCompletionForStoreUpdate(stillTrackedByNotifications, previous)).toBe(
+      false
+    )
+  })
+})
diff --git a/src/renderer/src/hooks/agent-hook-completion-store-sync.ts b/src/renderer/src/hooks/agent-hook-completion-store-sync.ts
new file mode 100644
index 00000000000..e900c5b0c5d
--- /dev/null
+++ b/src/renderer/src/hooks/agent-hook-completion-store-sync.ts
@@ -0,0 +1,112 @@
+type CompletionNotificationSettings = {
+  readonly enabled?: boolean
+  readonly agentTaskComplete?: boolean
+}
+
+type CompletionStoreSettings = {
+  readonly notifications?: CompletionNotificationSettings
+  readonly experimentalTerminalAttention?: boolean
+}
+
+type CompletionTerminalTab = {
+  readonly id: string
+  readonly ptyId?: string | null
+  readonly title?: string
+}
+
+export type AgentHookCompletionStoreSnapshot = {
+  readonly settings: CompletionStoreSettings | null
+  readonly tabsByWorktree: Readonly<Record<string, readonly CompletionTerminalTab[]>>
+  readonly ptyIdsByTabId: Readonly<Record<string, readonly string[]>>
+  readonly terminalLayoutsByTabId: Readonly<Record<string, unknown>>
+  readonly suppressedPtyExitIds: Readonly<Record<string, boolean>>
+}
+
+type TabVisit = () => void
+
+function isTrackingEnabled(state: AgentHookCompletionStoreSnapshot): boolean {
+  const notifications = state.settings?.notifications
+  const notificationEnabled =
+    notifications?.enabled !== false && notifications?.agentTaskComplete !== false
+  return notificationEnabled || state.settings?.experimentalTerminalAttention === true
+}
+
+function terminalTabLivenessMatches(
+  current: AgentHookCompletionStoreSnapshot['tabsByWorktree'],
+  previous: AgentHookCompletionStoreSnapshot['tabsByWorktree'],
+  visitTab?: TabVisit
+): boolean {
+  if (current === previous) {
+    return true
+  }
+
+  const currentWorktreeIds = Object.keys(current)
+  const previousWorktreeIds = Object.keys(previous)
+  if (currentWorktreeIds.length !== previousWorktreeIds.length) {
+    return false
+  }
+
+  for (const [worktreeIndex, worktreeId] of currentWorktreeIds.entries()) {
+    // Why: duplicate tab ids use first-worktree-wins lookup semantics, so a
+    // worktree-key reorder is a liveness change even when every array is reused.
+    if (previousWorktreeIds[worktreeIndex] !== worktreeId) {
+      return false
+    }
+    const currentTabs = current[worktreeId]
+    const previousTabs = previous[worktreeId]
+    if (currentTabs === previousTabs) {
+      continue
+    }
+    if (!currentTabs || !previousTabs || currentTabs.length !== previousTabs.length) {
+      return false
+    }
+    for (const [tabIndex, currentTab] of currentTabs.entries()) {
+      visitTab?.()
+      const previousTab = previousTabs[tabIndex]
+      if (
+        !previousTab ||
+        currentTab.id !== previousTab.id ||
+        currentTab.ptyId !== previousTab.ptyId
+      ) {
+        return false
+      }
+    }
+  }
+  return true
+}
+
+function shouldSync(
+  current: AgentHookCompletionStoreSnapshot,
+  previous: AgentHookCompletionStoreSnapshot,
+  visitTab?: TabVisit
+): boolean {
+  if (isTrackingEnabled(current) !== isTrackingEnabled(previous)) {
+    return true
+  }
+  if (
+    current.ptyIdsByTabId !== previous.ptyIdsByTabId ||
+    current.terminalLayoutsByTabId !== previous.terminalLayoutsByTabId ||
+    current.suppressedPtyExitIds !== previous.suppressedPtyExitIds
+  ) {
+    return true
+  }
+  return !terminalTabLivenessMatches(current.tabsByWorktree, previous.tabsByWorktree, visitTab)
+}
+
+export function shouldSyncAgentHookCompletionForStoreUpdate(
+  current: AgentHookCompletionStoreSnapshot,
+  previous: AgentHookCompletionStoreSnapshot
+): boolean {
+  return shouldSync(current, previous)
+}
+
+export function _measureAgentHookCompletionStoreSyncForTest(
+  current: AgentHookCompletionStoreSnapshot,
+  previous: AgentHookCompletionStoreSnapshot
+): { shouldSync: boolean; tabVisits: number } {
+  let tabVisits = 0
+  const requiresSync = shouldSync(current, previous, () => {
+    tabVisits += 1
+  })
+  return { shouldSync: requiresSync, tabVisits }
+}
diff --git a/src/renderer/src/hooks/useIpcEvents.test.ts b/src/renderer/src/hooks/useIpcEvents.test.ts
index 7abf34a6d3e..28d2aa993dd 100644
--- a/src/renderer/src/hooks/useIpcEvents.test.ts
+++ b/src/renderer/src/hooks/useIpcEvents.test.ts
@@ -4299,7 +4299,7 @@ describe('useIpcEvents agent status snapshot integration', () => {
     stateStartedAt: number
   }
   type StoreLike = Record<string, unknown>
-  type StoreSubscribeListener = (state: StoreLike) => void
+  type StoreSubscribeListener = (state: StoreLike, previousState: StoreLike) => void
   type MobileFitEvent = {
     ptyId: string
     mode: 'mobile-fit' | 'desktop-fit'
@@ -4799,6 +4799,7 @@ describe('useIpcEvents agent status snapshot integration', () => {
     expect(setAgentStatus).not.toHaveBeenCalled()
     expect(getSnapshot).not.toHaveBeenCalled()
 
+    const previousStoreState = { ...storeState }
     storeState.workspaceSessionReady = true
     storeState.tabsByWorktree = {
       'wt-1': [{ id: 'tab-future', ptyId: 'pty-1', worktreeId: 'wt-1', title: 'Future Tab' }]
@@ -4813,7 +4814,7 @@ describe('useIpcEvents agent status snapshot integration', () => {
     if (typeof subscribeListenerRef.current !== 'function') {
       throw new Error('Expected useAppStore.subscribe listener to be registered')
     }
-    subscribeListenerRef.current(storeState)
+    subscribeListenerRef.current(storeState, previousStoreState)
     await Promise.resolve()
 
     expect(setAgentStatus).toHaveBeenCalledTimes(1)
@@ -4937,7 +4938,7 @@ describe('useIpcEvents agent status snapshot integration', () => {
     vi.doMock('./agent-hook-completion-notifications', () => ({
       observeAgentHookCompletionForNotification,
       resetAgentHookCompletionNotificationCoordinators: vi.fn(),
-      syncAgentHookCompletionNotificationSettings: vi.fn()
+      syncAgentHookCompletionNotificationsForStoreUpdate: vi.fn()
     }))
     stubAuxiliaryModules()
     vi.stubGlobal(
@@ -5014,7 +5015,7 @@ describe('useIpcEvents agent status snapshot integration', () => {
     vi.doMock('./agent-hook-completion-notifications', () => ({
       observeAgentHookCompletionForNotification,
       resetAgentHookCompletionNotificationCoordinators: vi.fn(),
-      syncAgentHookCompletionNotificationSettings: vi.fn()
+      syncAgentHookCompletionNotificationsForStoreUpdate: vi.fn()
     }))
     stubAuxiliaryModules()
     vi.stubGlobal(
@@ -5169,7 +5170,7 @@ describe('useIpcEvents agent status snapshot integration', () => {
     vi.doMock('./agent-hook-completion-notifications', () => ({
       observeAgentHookCompletionForNotification,
       resetAgentHookCompletionNotificationCoordinators: vi.fn(),
-      syncAgentHookCompletionNotificationSettings: vi.fn()
+      syncAgentHookCompletionNotificationsForStoreUpdate: vi.fn()
     }))
     stubAuxiliaryModules()
     vi.stubGlobal(
@@ -5978,6 +5979,7 @@ describe('useIpcEvents agent status snapshot integration', () => {
       reason: 'unknown_tab_id'
     })
 
+    const previousStoreState = { ...storeState }
     storeState.terminalLayoutsByTabId = {
       'tab-future': {
         root: { type: 'leaf', leafId: FUTURE_LEAF_ID },
@@ -5988,7 +5990,7 @@ describe('useIpcEvents agent status snapshot integration', () => {
     if (typeof subscribeListenerRef.current !== 'function') {
       throw new Error('Expected useAppStore.subscribe listener to be registered')
     }
-    subscribeListenerRef.current(storeState)
+    subscribeListenerRef.current(storeState, previousStoreState)
 
     expect(setAgentStatus).toHaveBeenCalledTimes(2)
     expect(setAgentStatus).toHaveBeenNthCalledWith(
diff --git a/src/renderer/src/hooks/useIpcEvents.ts b/src/renderer/src/hooks/useIpcEvents.ts
index 219f8dca783..2eb7f545d2b 100644
--- a/src/renderer/src/hooks/useIpcEvents.ts
+++ b/src/renderer/src/hooks/useIpcEvents.ts
@@ -116,7 +116,7 @@ import {
 import {
   observeAgentHookCompletionForNotification,
   resetAgentHookCompletionNotificationCoordinators,
-  syncAgentHookCompletionNotificationSettings
+  syncAgentHookCompletionNotificationsForStoreUpdate
 } from './agent-hook-completion-notifications'
 import { shouldSuppressCodexAutoApprovalStatus } from '@/components/terminal-pane/codex-auto-approval-notification-suppression'
 import { showTerminalShortcutCaptureNotification } from '@/lib/terminal-shortcut-capture-notification'
@@ -3212,10 +3212,10 @@ export function useIpcEvents(): void {
     // renderer state.
     requestAgentStatusSnapshotIfReady()
     unsubs.push(
-      useAppStore.subscribe(() => {
+      useAppStore.subscribe((state, previousState) => {
         requestAgentStatusSnapshotIfReady()
         flushPendingAgentStatuses()
-        syncAgentHookCompletionNotificationSettings()
+        syncAgentHookCompletionNotificationsForStoreUpdate(state, previousState)
       })
     )