fix(countdown): prevent overlapping timers with in-flight lock

- Add countdownInProgress flag in IPC handler to reject concurrent starts
- Add countdownActive state in renderer to block re-entry
- Disable Record button while countdown is active

electron/ipc/handlers.ts

@@ -81,6 +81,7 @@ let cachedSystemCursorAssets: Record<string, SystemCursorAsset> | null = null
 let cachedSystemCursorAssetsSourceMtimeMs: number | null = null
 let countdownTimer: ReturnType<typeof setInterval> | null = null
 let countdownCancelled = false
+let countdownInProgress = false
 
 type SystemCursorAsset = {
   dataUrl: string
@@ -2767,6 +2768,11 @@ export function registerIpcHandlers(
   })
 
   ipcMain.handle('start-countdown', async (_, seconds: number) => {
+    if (countdownInProgress) {
+      return { success: false, error: 'Countdown already in progress' }
+    }
+
+    countdownInProgress = true
     countdownCancelled = false
 
     const countdownWin = createCountdownWindow()
@@ -2789,6 +2795,7 @@ export function registerIpcHandlers(
             countdownTimer = null
           }
           closeCountdownWindow()
+          countdownInProgress = false
           resolve({ success: false, cancelled: true })
           return
         }
@@ -2801,6 +2808,7 @@ export function registerIpcHandlers(
             countdownTimer = null
           }
           closeCountdownWindow()
+          countdownInProgress = false
           resolve({ success: true })
         } else {
           const win = getCountdownWindow()
@@ -2814,6 +2822,7 @@ export function registerIpcHandlers(
 
   ipcMain.handle('cancel-countdown', () => {
     countdownCancelled = true
+    countdownInProgress = false
     if (countdownTimer) {
       clearInterval(countdownTimer)
       countdownTimer = null

src/components/launch/LaunchWindow.tsx

@@ -31,6 +31,7 @@ export function LaunchWindow() {
   const LOCALE_LABELS: Record<string, string> = { en: "EN", es: "ES", "zh-CN": "中文" };
   const {
     recording,
+    countdownActive,
     toggleRecording,
     microphoneEnabled,
     setMicrophoneEnabled,
@@ -283,7 +284,7 @@ export function LaunchWindow() {
             variant="link"
             size="sm"
             onClick={hasSelectedSource ? toggleRecording : openSourceSelector}
-            disabled={!hasSelectedSource && !recording}
+            disabled={countdownActive || (!hasSelectedSource && !recording)}
             className={`gap-1 text-white bg-transparent hover:bg-transparent px-0 text-xs ${styles.electronNoDrag}`}
           >
             {recording ? (

src/hooks/useScreenRecorder.ts

@@ -28,6 +28,7 @@ const MIC_GAIN_BOOST = 1.4;
 
 type UseScreenRecorderReturn = {
   recording: boolean;
+  countdownActive: boolean;
   toggleRecording: () => void;
   preparePermissions: (options?: { startup?: boolean }) => Promise<boolean>;
   isMacOS: boolean;
@@ -44,6 +45,7 @@ type UseScreenRecorderReturn = {
 export function useScreenRecorder(): UseScreenRecorderReturn {
   const [recording, setRecording] = useState(false);
   const [starting, setStarting] = useState(false);
+  const [countdownActive, setCountdownActive] = useState(false);
   const [isMacOS, setIsMacOS] = useState(false);
   const [microphoneEnabled, setMicrophoneEnabled] = useState(false);
   const [microphoneDeviceId, setMicrophoneDeviceId] = useState<string | undefined>(undefined);
@@ -570,7 +572,7 @@ export function useScreenRecorder(): UseScreenRecorderReturn {
   };
 
   const toggleRecording = async () => {
-    if (starting) {
+    if (starting || countdownActive) {
       return;
     }
 
@@ -581,9 +583,14 @@ export function useScreenRecorder(): UseScreenRecorderReturn {
 
     // Start recording with optional countdown
     if (countdownDelay > 0) {
-      const result = await window.electronAPI.startCountdown(countdownDelay);
-      if (!result.success || result.cancelled) {
-        return;
+      setCountdownActive(true);
+      try {
+        const result = await window.electronAPI.startCountdown(countdownDelay);
+        if (!result.success || result.cancelled) {
+          return;
+        }
+      } finally {
+        setCountdownActive(false);
       }
     }
 
@@ -592,6 +599,7 @@ export function useScreenRecorder(): UseScreenRecorderReturn {
 
   return {
     recording,
+    countdownActive,
     toggleRecording,
     preparePermissions,
     isMacOS,