perf(mobile): cap the scheduled-notification map + tap-dedup set (#7646)

scheduledNotificationsByHostAndNotificationId (mobile-notifications.ts)
retained one entry per scheduled desktop notification. The key embeds
notificationId, which carries a per-completion timestamp
(buildAgentNotificationId), so every agent-task-complete inserts a new,
never-reused key. Entries are removed only when the desktop sends a
matching dismiss — which a remote mobile user (not sitting at the
desktop) frequently never receives — so the module-level map grew for
the app's whole lifetime. Small per entry, but genuinely unbounded.

Fix: bound the map to the 256 most-recent SETTLED entries (never evict
one mid-schedule). A settled entry only retains a small identifier used
for later programmatic dismissal, which is unnecessary for long-past
completions, so eviction has no user-visible effect.

Also FIFO-cap RootLayout's handledNotificationIdsRef tap-dedup Set
(RootLayout never unmounts, so it otherwise grew one id per tapped
notification forever).

Test (red->green): with the cap at 1, scheduling a second notification
evicts the first, so a later dismiss for the evicted id is a no-op while
the retained one still dismisses; without the cap the old entry survives.

mobile/app/_layout.tsx

@@ -102,6 +102,14 @@ export default function RootLayout() {
         return
       }
       handledNotificationIdsRef.current.add(notificationId)
+      // Why: RootLayout never unmounts, so cap this tap-dedup set (FIFO) rather
+      // than letting it grow one id per notification tapped for the app's life.
+      if (handledNotificationIdsRef.current.size > 256) {
+        const oldest = handledNotificationIdsRef.current.values().next().value
+        if (oldest !== undefined) {
+          handledNotificationIdsRef.current.delete(oldest)
+        }
+      }
 
       const path = await getNavigationPath(response.notification.request.content.data)
       clearLastNotificationResponse()

mobile/src/notifications/mobile-notifications.test.ts

@@ -1,6 +1,9 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 import * as Notifications from 'expo-notifications'
-import { subscribeToDesktopNotifications } from './mobile-notifications'
+import {
+  setScheduledNotificationsMaxForTests,
+  subscribeToDesktopNotifications
+} from './mobile-notifications'
 import type { RpcClient } from '../transport/rpc-client'
 import { loadPushNotificationsEnabled } from '../storage/preferences'
 
@@ -268,4 +271,48 @@ describe('subscribeToDesktopNotifications', () => {
 
     expect(Notifications.dismissNotificationAsync).not.toHaveBeenCalled()
   })
+
+  // Why: notificationId is unique per completion, so the map grew unbounded when
+  // the desktop never sent a dismiss (the remote-mobile case). It is now capped.
+  it('evicts the oldest scheduled entry once the cap is exceeded', async () => {
+    setScheduledNotificationsMaxForTests(1)
+    try {
+      vi.mocked(loadPushNotificationsEnabled).mockResolvedValue(true)
+      vi.mocked(Notifications.getPermissionsAsync).mockResolvedValue({
+        status: 'granted',
+        canAskAgain: true
+      } as never)
+      vi.mocked(Notifications.scheduleNotificationAsync)
+        .mockResolvedValueOnce('scheduled-old')
+        .mockResolvedValueOnce('scheduled-new')
+      vi.mocked(Notifications.dismissNotificationAsync).mockResolvedValue(undefined)
+      let onEvent: ((data: unknown) => void) | null = null
+      const client = {
+        subscribe: vi.fn((_method, _params, callback: (data: unknown) => void) => {
+          onEvent = callback
+          return vi.fn()
+        }),
+        getState: vi.fn(() => 'connected'),
+        sendRequest: vi.fn()
+      } as unknown as RpcClient
+
+      subscribeToDesktopNotifications(client, 'host-1')
+      onEvent?.({ type: 'notification', title: 't', body: 'b', notificationId: 'agent:old' })
+      await flushAsync()
+      onEvent?.({ type: 'notification', title: 't', body: 'b', notificationId: 'agent:new' })
+      await flushAsync()
+
+      // The older entry was evicted by the cap: dismissing it is a no-op...
+      onEvent?.({ type: 'dismiss', notificationId: 'agent:old' })
+      await flushAsync()
+      expect(Notifications.dismissNotificationAsync).not.toHaveBeenCalledWith('scheduled-old')
+
+      // ...while the most-recent entry is retained and still dismissable.
+      onEvent?.({ type: 'dismiss', notificationId: 'agent:new' })
+      await flushAsync()
+      expect(Notifications.dismissNotificationAsync).toHaveBeenCalledWith('scheduled-new')
+    } finally {
+      setScheduledNotificationsMaxForTests()
+    }
+  })
 })

mobile/src/notifications/mobile-notifications.ts

@@ -31,10 +31,42 @@ type ScheduledNotificationState = {
 
 const scheduledNotificationsByHostAndNotificationId = new Map<string, ScheduledNotificationState>()
 
+// Why: notificationId embeds a per-completion timestamp (buildAgentNotificationId),
+// so every agent-task-complete inserts a new, never-reused key. Entries are only
+// removed when the desktop sends a matching dismiss — which a remote mobile user
+// (not at the desktop) frequently never gets — so the map grew for the app's whole
+// life. Bound it; a settled entry only retains a small identifier used for later
+// programmatic dismissal, unnecessary for long-past completions.
+const MAX_SCHEDULED_NOTIFICATIONS = 256
+let maxScheduledNotifications = MAX_SCHEDULED_NOTIFICATIONS
+
 function getStoredNotificationKey(hostId: string, notificationId: string): string {
   return `${encodeURIComponent(hostId)}:${encodeURIComponent(notificationId)}`
 }
 
+// Evict the oldest SETTLED entries (never one mid-schedule) until within the cap.
+// Map iteration is insertion order, so the first match is the oldest.
+function boundScheduledNotifications(): void {
+  while (scheduledNotificationsByHostAndNotificationId.size > maxScheduledNotifications) {
+    let evicted = false
+    for (const [key, state] of scheduledNotificationsByHostAndNotificationId) {
+      if (!state.pending) {
+        scheduledNotificationsByHostAndNotificationId.delete(key)
+        evicted = true
+        break
+      }
+    }
+    if (!evicted) {
+      break
+    }
+  }
+}
+
+/** Test-only: override the cap (pass no arg to restore the default). */
+export function setScheduledNotificationsMaxForTests(max?: number): void {
+  maxScheduledNotifications = max ?? MAX_SCHEDULED_NOTIFICATIONS
+}
+
 export type NotificationPermissionState = {
   granted: boolean
   status: string
@@ -155,6 +187,7 @@ async function showLocalNotification(event: NotificationEvent, hostId: string):
       return
     }
     notificationState.identifier = scheduledIdentifier
+    boundScheduledNotifications()
   } finally {
     if (notificationState.pending === pending) {
       notificationState.pending = undefined