fix(mobile): fence tab activation replies to their source

Ignore activation snapshots after the host, workspace, operation binding, or mounted route changes. Expo reuses session state across workspaces, so applying a late activation could repopulate the next route with the previous workspace's tabs. Cover the four invalidations and an unchanged source with React hook tests, and update the existing parity digest for the intentional guard.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

mobile/src/session/mobile-session-route-parity.test.ts

@@ -66,11 +66,12 @@ const HOST_COMPONENT_NAMES = new Set([
   'View'
 ])
 
-const HEAD_MAIN_HOOK_SHA256 = '4fae0d13d86c343b380969797051a376a101176cfaed2f945b4fb13e86b7fc25'
-const HEAD_HOOK_BINDING_SHA256 = 'f4405cb67d0879c66e87260653f68fbe8c51de6e386e75c3bdc793012cb15c4d'
+// Activation source fencing adds two hooks; session-tab-activation-source-race tests the behavior.
+const HEAD_MAIN_HOOK_SHA256 = '8a65c402639980ffda9132ce3dba84da8d85998f5c6b933a8c8eb09817a04783'
+const HEAD_HOOK_BINDING_SHA256 = 'e43ab1ae9e6fd0eb126558207868f1da6322ba50bdeb4a6f7132e6a1f29a9474'
 const HEAD_CALLBACK_IDENTITY_SHA256 =
   '3ad3c833aa99bbfd3a4038bae70a0247192f51fb938a2fe3df86626dcfa3386e'
-const HEAD_CALLBACK_BODY_SHA256 = '7da7b4dd9a184f3e583213e30e77383b5ecda1360ec53a59f16fbdbdae2d0257'
+const HEAD_CALLBACK_BODY_SHA256 = '9168096f0e16c9bfe39e6c24b2365254c18f6d5a7b0611082b8723ee826fedfc'
 const HEAD_EFFECT_SHA256 = 'f81ef4b4794875643dd429e9dfb6cffab037feb68a334e260c0045a258c07d51'
 const HEAD_CONTENT_HOOK_SHA256 = 'd74431115b27c22dd38c29a510604554ca767cdd2585beaa73ec2e2dae0c5de4'
 const HEAD_NESTED_FUNCTION_SHA256 =
@@ -479,7 +480,7 @@ describe('mobile session route extraction parity', () => {
     const contentBindings = CONTENT_COMPONENT_NAMES.flatMap(
       (name) => readHookFacts(name, definitions).bindings
     )
-    expect(main.hooks).toHaveLength(288)
+    expect(main.hooks).toHaveLength(290)
     expect(hash(main.hooks)).toBe(HEAD_MAIN_HOOK_SHA256)
     expect(hash(main.bindings)).toBe(HEAD_HOOK_BINDING_SHA256)
     expect(main.callbacks).toHaveLength(84)

mobile/src/session/session-tab-activation-source-race.test.ts

@@ -0,0 +1,107 @@
+import { createElement } from 'react'
+import { act, create } from 'react-test-renderer'
+import { describe, expect, it, vi } from 'vitest'
+import { useMobileSessionTabApplication } from './use-mobile-session-tab-application'
+import type { MobileSessionTerminalListModel } from './use-mobile-session-terminal-list'
+import type { SessionTabsResult } from './mobile-session-route-types'
+
+function scope() {
+  const ref = <T>(current: T) => ({ current })
+  return {
+    hostId: 'host-a',
+    worktreeId: 'workspace-a',
+    sessionTabOperations: { activate: vi.fn() },
+    setWorkspaceTransportState: vi.fn(),
+    setTerminals: vi.fn(),
+    terminalsRef: ref([]),
+    setSessionTabs: vi.fn(),
+    sessionTabsRef: ref([]),
+    appliedSnapshotMarkerRef: ref({ epoch: null, version: -1 }),
+    appliedSessionTabsRevisionRef: ref(0),
+    closedTabTombstonesRef: ref(new Map()),
+    reconcileBufferedDraftsRef: ref(vi.fn()),
+    setTerminalsLoaded: vi.fn(),
+    defaultTerminalHandlesToLiveInput: vi.fn(),
+    setActiveHandle: vi.fn(),
+    setActiveSessionTabId: vi.fn(),
+    activeSessionTabIdRef: ref(null),
+    selectedSessionTabIdRef: ref(null),
+    markdownDocsRef: ref(new Map()),
+    initializedHandlesRef: ref(new Set()),
+    terminalDiagnosticsRef: ref({ tabsApplied: vi.fn() }),
+    activeHandleRef: ref(null),
+    activeSessionTabTypeRef: ref(null),
+    pendingActiveSessionTabIdRef: ref(null),
+    pendingActiveTerminalHandleRef: ref(null),
+    pendingBrowserFocusPageIdRef: ref(null),
+    initialSessionAutoCreateRef: ref({ sawSessionTabs: false }),
+    unsubscribeTerminal: vi.fn(),
+    subscribeToTerminal: vi.fn(),
+    lastKnownTerminalCountRef: ref(0),
+    setFileDocs: vi.fn(),
+    setMarkdownDocs: vi.fn(),
+    fileDocLifecycleRef: ref({ reconcile: vi.fn() }),
+    markdownDocLifecycleRef: ref({ reconcile: vi.fn() })
+  }
+}
+
+describe('session tab activation source ownership', () => {
+  it.each(['workspace', 'host', 'operations', 'unmount', 'unchanged'] as const)(
+    'handles a delayed activation after %s changes',
+    async (change) => {
+      const initial = scope()
+      let resolveActivation: (snapshot: SessionTabsResult) => void = () => {}
+      initial.sessionTabOperations.activate.mockReturnValue(
+        new Promise<SessionTabsResult>((resolve) => {
+          resolveActivation = resolve
+        })
+      )
+      let actions: ReturnType<typeof useMobileSessionTabApplication> | undefined
+      function Harness({ value }: { value: typeof initial }) {
+        actions = useMobileSessionTabApplication(value as unknown as MobileSessionTerminalListModel)
+        return null
+      }
+      let renderer: ReturnType<typeof create> | undefined
+      try {
+        act(() => {
+          renderer = create(createElement(Harness, { value: initial }))
+        })
+        const activation = actions!.activateSessionTab('tab-a')
+        act(() => {
+          if (change === 'unmount') {
+            renderer?.unmount()
+          } else {
+            renderer?.update(
+              createElement(Harness, {
+                value: {
+                  ...initial,
+                  ...(change === 'workspace' ? { worktreeId: 'workspace-b' } : {}),
+                  ...(change === 'host' ? { hostId: 'host-b' } : {}),
+                  ...(change === 'operations'
+                    ? { sessionTabOperations: { activate: vi.fn() } }
+                    : {})
+                }
+              })
+            )
+          }
+        })
+        const snapshot = {
+          snapshotVersion: 1,
+          tabs: [],
+          activeTabId: null
+        } as unknown as SessionTabsResult
+        await act(async () => {
+          resolveActivation(snapshot)
+          await activation
+        })
+        expect(initial.setSessionTabs).toHaveBeenCalledTimes(change === 'unchanged' ? 1 : 0)
+        expect(initial.setWorkspaceTransportState).toHaveBeenCalledTimes(
+          change === 'unchanged' ? 1 : 0
+        )
+        expect(await activation).toBe(change === 'unchanged')
+      } finally {
+        act(() => renderer?.unmount())
+      }
+    }
+  )
+})

mobile/src/session/use-mobile-session-tab-application.ts

@@ -1,4 +1,4 @@
-import { useCallback } from 'react'
+import { useCallback, useLayoutEffect, useRef } from 'react'
 import {
   getTerminalRecordsFromSessionTabs,
   mergeTerminalRecordsByCurrentOrder,
@@ -18,6 +18,7 @@ import type { MobileSessionTerminalListModel } from './use-mobile-session-termin
 
 export function useMobileSessionTabApplication(scope: MobileSessionTerminalListModel) {
   const {
+    hostId,
     worktreeId,
     sessionTabOperations,
     setTerminals,
@@ -52,6 +53,13 @@ export function useMobileSessionTabApplication(scope: MobileSessionTerminalListM
     markdownDocLifecycleRef,
     setWorkspaceTransportState
   } = scope
+  const activationGenerationRef = useRef(0)
+  useLayoutEffect(() => {
+    activationGenerationRef.current += 1
+    return () => {
+      activationGenerationRef.current += 1
+    }
+  }, [hostId, worktreeId, sessionTabOperations])
   const applySessionTabs = useCallback(
     (result: SessionTabsResult): SessionTabsApplyOutcome<MobileSessionTab> => {
       const diagnostics = terminalDiagnosticsRef.current
@@ -225,7 +233,13 @@ export function useMobileSessionTabApplication(scope: MobileSessionTerminalListM
       if (!sessionTabOperations) {
         return false
       }
-      applySessionTabs(await sessionTabOperations.activate(worktreeId, tabId, leafId))
+      const generation = activationGenerationRef.current
+      const snapshot = await sessionTabOperations.activate(worktreeId, tabId, leafId)
+      // Expo reuses the route; an old activation cannot publish into its replacement workspace.
+      if (generation !== activationGenerationRef.current) {
+        return false
+      }
+      applySessionTabs(snapshot)
       return true
     },
     [applySessionTabs, sessionTabOperations, worktreeId]