🐛 fix: config race conditions, quit safety, update data loss

- Config write serialization via _writeQueue prevents concurrent
  read-modify-write races between settings/queue/history saves
- Cancel active uploads on app quit (prevents zombie processes)
- Persist queue before update install (prevents queue loss)
- Sync IPC save in beforeunload (guarantees save before close)
- Fix double configStore.load() call
- Guard against status regression in handleProgress (done→uploading)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/config-store.js

@@ -94,6 +94,7 @@ class ConfigStore {
       ? app.getPath('userData')
       : path.join(__dirname, '..');
     this.filePath = path.join(dir, 'electron-config.json');
+    this._writeQueue = Promise.resolve(); // Serializes all writes to prevent race conditions
 
     // Migrate config from old location if current doesn't exist
     if (!fs.existsSync(this.filePath) && app && app.isPackaged) {
@@ -208,12 +209,19 @@ class ConfigStore {
     }
   }
 
+  _enqueueWrite(fn) {
+    this._writeQueue = this._writeQueue.then(fn, fn);
+    return this._writeQueue;
+  }
+
   save(config) {
-    const current = this.load();
-    if (config.hosters) current.hosters = config.hosters;
-    if (config.hosterSettings) current.hosterSettings = config.hosterSettings;
-    if (config.globalSettings) current.globalSettings = config.globalSettings;
-    return this._atomicWrite(JSON.stringify(current, null, 2));
+    return this._enqueueWrite(() => {
+      const current = this.load();
+      if (config.hosters) current.hosters = config.hosters;
+      if (config.hosterSettings) current.hosterSettings = config.hosterSettings;
+      if (config.globalSettings) current.globalSettings = config.globalSettings;
+      return this._atomicWrite(JSON.stringify(current, null, 2));
+    });
   }
 
   loadHistory() {
@@ -242,18 +250,22 @@ class ConfigStore {
   }
 
   appendHistory(entry) {
-    const config = this.load();
-    config.history.push(entry);
-    if (config.history.length > MAX_HISTORY) {
-      config.history = config.history.slice(-MAX_HISTORY);
-    }
-    return this._atomicWrite(JSON.stringify(config, null, 2));
+    return this._enqueueWrite(() => {
+      const config = this.load();
+      config.history.push(entry);
+      if (config.history.length > MAX_HISTORY) {
+        config.history = config.history.slice(-MAX_HISTORY);
+      }
+      return this._atomicWrite(JSON.stringify(config, null, 2));
+    });
   }
 
   clearHistory() {
-    const config = this.load();
-    config.history = [];
-    return this._atomicWrite(JSON.stringify(config, null, 2));
+    return this._enqueueWrite(() => {
+      const config = this.load();
+      config.history = [];
+      return this._atomicWrite(JSON.stringify(config, null, 2));
+    });
   }
 }
 

main.js

@@ -502,7 +502,8 @@ app.whenReady().then(() => {
 
   // Auto-start remote server if enabled
   try {
-    const remoteConfig = configStore.load().globalSettings && configStore.load().globalSettings.remote;
+    const _remCfg = configStore.load();
+    const remoteConfig = _remCfg.globalSettings && _remCfg.globalSettings.remote;
     if (remoteConfig && remoteConfig.enabled) {
       startRemoteServer().catch(err => {
         debugLog(`remote-server auto-start failed: ${err.message}`);
@@ -540,6 +541,7 @@ app.on('window-all-closed', () => {
 });
 
 app.on('before-quit', () => {
+  if (uploadManager) try { uploadManager.cancel(); } catch {}
   try { folderMonitor.stop(); } catch {}
   try {
     if (remoteServer) { remoteServer.stop(); remoteServer = null; }
@@ -874,6 +876,16 @@ ipcMain.handle('save-global-settings', async (_event, globalSettings) => {
   return true;
 });
 
+// Synchronous save for beforeunload — blocks renderer until write completes
+ipcMain.on('save-global-settings-sync', (event, globalSettings) => {
+  try {
+    const current = configStore.load();
+    current.globalSettings = globalSettings;
+    fs.writeFileSync(configStore.filePath, JSON.stringify(current, null, 2));
+  } catch {}
+  event.returnValue = true;
+});
+
 // --- Folder Monitor ---
 function startFolderMonitor(settings) {
   try {

preload.js

@@ -14,6 +14,7 @@ contextBridge.exposeInMainWorld('api', {
   // Global settings
   getGlobalSettings: () => ipcRenderer.invoke('get-global-settings'),
   saveGlobalSettings: (settings) => ipcRenderer.invoke('save-global-settings', settings),
+  saveGlobalSettingsSync: (settings) => ipcRenderer.sendSync('save-global-settings-sync', settings),
 
   // Always on top
   setAlwaysOnTop: (value) => ipcRenderer.invoke('set-always-on-top', value),

renderer/app.js

@@ -1487,6 +1487,9 @@ function handleProgress(data) {
     indexJob(job);
   }
 
+  // Don't regress from terminal states (stale callbacks can arrive after completion)
+  if (job.status === 'done' || job.status === 'skipped') return;
+
   // Update job state
   job.status = data.status;
   job.bytesUploaded = data.bytesUploaded || 0;
@@ -3041,14 +3044,16 @@ function sortHistoryRows(rows) {
   });
 }
 
-// Flush pending queue state on window close
+// Flush pending queue state on window close (sync IPC — blocks until save completes)
 window.addEventListener('beforeunload', () => {
-  if (queuePersistTimer) {
-    clearTimeout(queuePersistTimer);
-    queuePersistTimer = null;
-    // Synchronous-ish: fire and forget since window is closing
-    persistQueueStateNow().catch(() => {});
-  }
+  clearTimeout(queuePersistTimer);
+  queuePersistTimer = null;
+  const globalSettings = {
+    ...(config.globalSettings || {}),
+    pendingQueue: buildPersistedQueueState()
+  };
+  config.globalSettings = globalSettings;
+  window.api.saveGlobalSettingsSync(globalSettings);
 });
 
 // --- Setup Listeners ---
@@ -3252,6 +3257,7 @@ function showUpdateBanner(info) {
   document.getElementById('installUpdateBtn').onclick = async () => {
     msg.textContent = 'Update wird heruntergeladen...';
     document.getElementById('installUpdateBtn').disabled = true;
+    await persistQueueStateNow().catch(() => {}); // Save queue before update restart
     await window.api.installUpdate();
   };
   document.getElementById('dismissUpdateBtn').onclick = () => { banner.style.display = 'none'; };