diff --git a/mobile/src/session/mobile-session-route-parity.test.ts b/mobile/src/session/mobile-session-route-parity.test.ts
index d269aee1896..87204d0aa34 100644
--- a/mobile/src/session/mobile-session-route-parity.test.ts
+++ b/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)
diff --git a/mobile/src/session/session-tab-activation-source-race.test.ts b/mobile/src/session/session-tab-activation-source-race.test.ts
new file mode 100644
index 00000000000..6b2ec7fbad1
--- /dev/null
+++ b/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())
+      }
+    }
+  )
+})
diff --git a/mobile/src/session/use-mobile-session-tab-application.ts b/mobile/src/session/use-mobile-session-tab-application.ts
index dca02767a71..ea27a3b0940 100644
--- a/mobile/src/session/use-mobile-session-tab-application.ts
+++ b/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]