fix(mobile): clear state after closing final tab

mobile/app/h/[hostId]/session/[worktreeId].tsx

@@ -4131,6 +4131,7 @@ export default function SessionScreen() {
         reason: 'user'
       })
       if (response.ok) {
+        const remainingTabs = sessionTabsRef.current.filter((candidate) => candidate.id !== tab.id)
         if (tab.type === 'browser' && tab.browserPageId === pendingBrowserFocusPageIdRef.current) {
           pendingBrowserFocusPageIdRef.current = null
         }
@@ -4141,14 +4142,16 @@ export default function SessionScreen() {
           initializedHandlesRef.current.delete(terminalHandle)
           clearTerminalLiveInputDefault(terminalHandle)
         }
-        setSessionTabs((prev) => prev.filter((candidate) => candidate.id !== tab.id))
+        sessionTabsRef.current = remainingTabs
+        setSessionTabs(remainingTabs)
         // Why: tombstone the closed tab and rely on the snapshot, not a blind refetch that often re-added the not-yet-closed tab.
         closedTabTombstonesRef.current.set(tab.id, Date.now() + 10_000)
         // Why: bulk close re-activates the anchor before awaiting each close;
         // the render-synced ref sees that switch while this closure would not,
         // so comparing against the ref keeps the anchor from being nulled out.
-        if (activeSessionTabIdRef.current === tab.id) {
+        if (activeSessionTabIdRef.current === tab.id || remainingTabs.length === 0) {
           activeSessionTabTypeRef.current = null
+          activeSessionTabIdRef.current = null
           setActiveSessionTabId(null)
           activeHandleRef.current = null
           setActiveHandle(null)

mobile/src/session/mobile-session-last-tab-close.test.ts

@@ -0,0 +1,21 @@
+import { readFileSync } from 'node:fs'
+import { describe, expect, it } from 'vitest'
+
+const sessionRouteSource = readFileSync(
+  new URL('../../app/h/[hostId]/session/[worktreeId].tsx', import.meta.url),
+  'utf8'
+)
+
+describe('mobile session last-tab close', () => {
+  it('clears stale active identity when closing leaves no tabs', () => {
+    const start = sessionRouteSource.indexOf('async function handleCloseSessionTab')
+    const end = sessionRouteSource.indexOf('const bulkCloseActions', start)
+    const block = sessionRouteSource.slice(start, end)
+
+    expect(block).toContain(
+      'activeSessionTabIdRef.current === tab.id || remainingTabs.length === 0'
+    )
+    expect(block).toContain('activeSessionTabIdRef.current = null')
+    expect(block).toContain('activeHandleRef.current = null')
+  })
+})