perf: clean mobile live input focus timer (#4050)

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

@@ -70,8 +70,10 @@ import {
   loadTerminalAccessoryLayout
 } from '../../../../src/terminal/terminal-accessory-layout'
 import {
+  clearTerminalLiveInputFocusTimer,
   getTerminalLiveSpecialKeyBytes,
-  isTerminalLiveInputWithinByteLimit
+  isTerminalLiveInputWithinByteLimit,
+  scheduleTerminalLiveInputFocus
 } from '../../../../src/terminal/terminal-live-input'
 import { countTerminalGestureInputSequences } from '../../../../src/terminal/terminal-gesture-input'
 import { MobileBrowserPane, type MobileBrowserTab } from '../../../../src/browser/MobileBrowserPane'
@@ -1048,6 +1050,7 @@ export default function SessionScreen() {
   const viewportMeasuredRef = useRef(false)
   const terminalRefs = useRef<Map<string, TerminalWebViewHandle>>(new Map())
   const liveInputRef = useRef<TextInput>(null)
+  const liveInputFocusTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
   const terminalUnsubsRef = useRef<Map<string, () => void>>(new Map())
   const subscribingHandlesRef = useRef<Set<string>>(new Set())
   const initializedHandlesRef = useRef<Set<string>>(new Set())
@@ -1132,6 +1135,7 @@ export default function SessionScreen() {
       // so pending animation callbacks cannot clear a newer/unmounted surface.
       toastSeqRef.current += 1
       clearToastHideTimer()
+      clearTerminalLiveInputFocusTimer(liveInputFocusTimerRef)
     }
   }, [clearToastHideTimer])
 
@@ -2714,8 +2718,9 @@ export default function SessionScreen() {
     })
     setLiveInputCapture('')
     if (nextEnabled) {
-      setTimeout(() => liveInputRef.current?.focus(), 50)
+      scheduleTerminalLiveInputFocus(liveInputFocusTimerRef, () => liveInputRef.current?.focus())
     } else {
+      clearTerminalLiveInputFocusTimer(liveInputFocusTimerRef)
       liveInputRef.current?.blur()
     }
   }, [activeHandle, liveInputTerminalHandles])

mobile/src/terminal/terminal-live-input.test.ts

@@ -1,11 +1,22 @@
-import { describe, expect, it } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 import {
   TERMINAL_LIVE_INPUT_MAX_BYTES,
+  clearTerminalLiveInputFocusTimer,
   getTerminalLiveSpecialKeyBytes,
-  isTerminalLiveInputWithinByteLimit
+  isTerminalLiveInputWithinByteLimit,
+  scheduleTerminalLiveInputFocus,
+  type TerminalLiveInputFocusTimerRef
 } from './terminal-live-input'
 
+function createTimerRef(): TerminalLiveInputFocusTimerRef {
+  return { current: null }
+}
+
 describe('terminal live input', () => {
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
   it('maps phone keyboard special keys to PTY bytes', () => {
     expect(getTerminalLiveSpecialKeyBytes('Backspace')).toBe('\x7f')
     expect(getTerminalLiveSpecialKeyBytes('Enter')).toBeNull()
@@ -22,4 +33,32 @@ describe('terminal live input', () => {
       isTerminalLiveInputWithinByteLimit('é'.repeat(TERMINAL_LIVE_INPUT_MAX_BYTES / 2 + 1))
     ).toBe(false)
   })
+
+  it('replaces pending deferred focus work', () => {
+    vi.useFakeTimers()
+    const timerRef = createTimerRef()
+    const staleFocus = vi.fn()
+    const nextFocus = vi.fn()
+
+    scheduleTerminalLiveInputFocus(timerRef, staleFocus)
+    scheduleTerminalLiveInputFocus(timerRef, nextFocus)
+    vi.runOnlyPendingTimers()
+
+    expect(staleFocus).not.toHaveBeenCalled()
+    expect(nextFocus).toHaveBeenCalledTimes(1)
+    expect(timerRef.current).toBeNull()
+  })
+
+  it('clears pending deferred focus work', () => {
+    vi.useFakeTimers()
+    const timerRef = createTimerRef()
+    const focus = vi.fn()
+
+    scheduleTerminalLiveInputFocus(timerRef, focus)
+    clearTerminalLiveInputFocusTimer(timerRef)
+    vi.runOnlyPendingTimers()
+
+    expect(focus).not.toHaveBeenCalled()
+    expect(timerRef.current).toBeNull()
+  })
 })

mobile/src/terminal/terminal-live-input.ts

@@ -2,6 +2,10 @@ const TERMINAL_LIVE_INPUT_MAX_BYTES = 256 * 1024
 
 const encoder = new TextEncoder()
 
+export type TerminalLiveInputFocusTimerRef = {
+  current: ReturnType<typeof setTimeout> | null
+}
+
 export function getTerminalLiveSpecialKeyBytes(key: string): string | null {
   if (key === 'Backspace') {
     return '\x7f'
@@ -16,4 +20,26 @@ export function isTerminalLiveInputWithinByteLimit(
   return encoder.encode(text).byteLength <= maxBytes
 }
 
+export function clearTerminalLiveInputFocusTimer(timerRef: TerminalLiveInputFocusTimerRef): void {
+  if (timerRef.current === null) {
+    return
+  }
+  clearTimeout(timerRef.current)
+  timerRef.current = null
+}
+
+export function scheduleTerminalLiveInputFocus(
+  timerRef: TerminalLiveInputFocusTimerRef,
+  focus: () => void,
+  delayMs = 50
+): void {
+  // Why: live input can be toggled during route changes; replacing the pending
+  // focus timer prevents stale native TextInput focus after unmount/disable.
+  clearTerminalLiveInputFocusTimer(timerRef)
+  timerRef.current = setTimeout(() => {
+    timerRef.current = null
+    focus()
+  }, delayMs)
+}
+
 export { TERMINAL_LIVE_INPUT_MAX_BYTES }