diff --git a/src/main/services/infrastructure/NotificationManager.ts b/src/main/services/infrastructure/NotificationManager.ts
index cadf289a..3ebc49e6 100644
--- a/src/main/services/infrastructure/NotificationManager.ts
+++ b/src/main/services/infrastructure/NotificationManager.ts
@@ -174,10 +174,99 @@ async function selectLegacyNotificationData(): Promise<LegacyNotificationData |
 }
 
 function isNotificationHistoryJson(data: string): boolean {
+  return parseNotificationHistory(data) !== null;
+}
+
+interface NotificationHistoryParseResult {
+  notifications: StoredNotification[];
+  recovered: boolean;
+}
+
+function parseNotificationHistory(data: string): NotificationHistoryParseResult | null {
+  const parsed = parseNotificationHistoryArray(data);
+  if (parsed) {
+    return { notifications: parsed, recovered: false };
+  }
+
+  const firstArrayEnd = findFirstJsonArrayEnd(data);
+  if (firstArrayEnd === null) {
+    return null;
+  }
+
+  const recovered = parseNotificationHistoryArray(data.slice(0, firstArrayEnd));
+  return recovered ? { notifications: recovered, recovered: true } : null;
+}
+
+function parseNotificationHistoryArray(data: string): StoredNotification[] | null {
   try {
-    return Array.isArray(JSON.parse(data));
+    const parsed = JSON.parse(data) as unknown;
+    return Array.isArray(parsed) ? (parsed as StoredNotification[]) : null;
   } catch {
-    return false;
+    return null;
+  }
+}
+
+function findFirstJsonArrayEnd(data: string): number | null {
+  const start = data.search(/\S/u);
+  if (start === -1 || data[start] !== '[') {
+    return null;
+  }
+
+  let depth = 0;
+  let inString = false;
+  let escaped = false;
+
+  for (let index = start; index < data.length; index++) {
+    const char = data[index];
+
+    if (inString) {
+      if (escaped) {
+        escaped = false;
+      } else if (char === '\\') {
+        escaped = true;
+      } else if (char === '"') {
+        inString = false;
+      }
+      continue;
+    }
+
+    if (char === '"') {
+      inString = true;
+      continue;
+    }
+
+    if (char === '[') {
+      depth += 1;
+      continue;
+    }
+
+    if (char === ']') {
+      depth -= 1;
+      if (depth === 0) {
+        return index + 1;
+      }
+    }
+  }
+
+  return null;
+}
+
+async function writeNotificationsFileAtomically(filePath: string, data: string): Promise<void> {
+  const dir = path.dirname(filePath);
+  const tempPath = path.join(
+    dir,
+    `.${path.basename(filePath)}.${process.pid}.${Date.now()}.${Math.random()
+      .toString(16)
+      .slice(2)}.tmp`
+  );
+
+  try {
+    await fsp.mkdir(dir, { recursive: true });
+    await fsp.writeFile(tempPath, data, 'utf8');
+    await fsp.rename(tempPath, filePath);
+  } catch (error) {
+    await fsp.rm(tempPath, { force: true }).catch(() => undefined);
+    throw error;
   }
 }
 
@@ -204,6 +293,7 @@ export class NotificationManager extends EventEmitter {
    *  before writing, preventing a race where save overwrites unloaded data. */
   private initPromise: Promise<void> | null = null;
   private notificationsPath = NOTIFICATIONS_PATH;
+  private saveChain: Promise<void> = Promise.resolve();
 
   constructor(configManager?: ConfigManager) {
     super();
@@ -281,13 +371,18 @@ export class NotificationManager extends EventEmitter {
   private async loadNotifications(): Promise<void> {
     try {
       const data = await fsp.readFile(this.notificationsPath, 'utf8');
-      const parsed = JSON.parse(data) as unknown;
+      const parsed = parseNotificationHistory(data);
 
-      if (Array.isArray(parsed)) {
-        this.notifications = parsed as StoredNotification[];
-      } else {
+      if (!parsed) {
         logger.warn('Invalid notifications file format, starting fresh');
         this.notifications = [];
+        return;
+      }
+
+      this.notifications = parsed.notifications;
+      if (parsed.recovered) {
+        logger.info('Recovered notifications from a corrupted history file, compacting storage');
+        this.saveNotifications();
       }
     } catch (error) {
       // ENOENT is expected on first run — no file to load
@@ -305,11 +400,11 @@ export class NotificationManager extends EventEmitter {
    */
   private saveNotifications(): void {
     const data = JSON.stringify(this.notifications, null, 2);
-    const dir = path.dirname(this.notificationsPath);
+    const notificationsPath = this.notificationsPath;
 
-    fsp
-      .mkdir(dir, { recursive: true })
-      .then(() => fsp.writeFile(this.notificationsPath, data, 'utf8'))
+    this.saveChain = this.saveChain
+      .catch(() => undefined)
+      .then(() => writeNotificationsFileAtomically(notificationsPath, data))
       .catch((error) => {
         logger.error('Error saving notifications:', error);
       });
diff --git a/test/main/services/infrastructure/NotificationManager.migration.test.ts b/test/main/services/infrastructure/NotificationManager.migration.test.ts
index 57fc549c..b4ceeb60 100644
--- a/test/main/services/infrastructure/NotificationManager.migration.test.ts
+++ b/test/main/services/infrastructure/NotificationManager.migration.test.ts
@@ -47,21 +47,23 @@ describe('NotificationManager storage migration', () => {
     return tempHome;
   }
 
+  function makeStoredNotification(id: string) {
+    return {
+      id,
+      title: id,
+      message: 'Copied',
+      timestamp: new Date().toISOString(),
+      type: 'error',
+      isRead: false,
+      createdAt: Date.now(),
+    };
+  }
+
   it('copies legacy notification history to the new Agent Teams filename', async () => {
     const home = useTempHome();
     const legacyPath = path.join(home, '.claude', 'claude-devtools-notifications.json');
     const currentPath = path.join(home, '.claude', 'agent-teams-notifications.json');
-    const legacyNotifications = [
-      {
-        id: 'legacy-notification',
-        title: 'Legacy',
-        message: 'Copied',
-        timestamp: new Date().toISOString(),
-        type: 'error',
-        isRead: false,
-        createdAt: Date.now(),
-      },
-    ];
+    const legacyNotifications = [makeStoredNotification('legacy-notification')];
     fs.mkdirSync(path.dirname(legacyPath), { recursive: true });
     fs.writeFileSync(legacyPath, JSON.stringify(legacyNotifications), 'utf8');
 
@@ -82,17 +84,7 @@ describe('NotificationManager storage migration', () => {
     const home = useTempHome();
     const legacyPath = path.join(home, '.claude', 'claude-devtools-notifications.json');
     const currentPath = path.join(home, '.claude', 'agent-teams-notifications.json');
-    const currentNotifications = [
-      {
-        id: 'current-notification',
-        title: 'Current',
-        message: 'Kept',
-        timestamp: new Date().toISOString(),
-        type: 'error',
-        isRead: false,
-        createdAt: Date.now(),
-      },
-    ];
+    const currentNotifications = [makeStoredNotification('current-notification')];
     fs.mkdirSync(path.dirname(currentPath), { recursive: true });
     fs.writeFileSync(
       legacyPath,
@@ -117,17 +109,7 @@ describe('NotificationManager storage migration', () => {
     const home = useTempHome();
     const legacyPath = path.join(home, '.claude', 'claude-code-context-notifications.json');
     const currentPath = path.join(home, '.claude', 'agent-teams-notifications.json');
-    const legacyNotifications = [
-      {
-        id: 'pre-devtools-notification',
-        title: 'Old',
-        message: 'Copied',
-        timestamp: new Date().toISOString(),
-        type: 'error',
-        isRead: false,
-        createdAt: Date.now(),
-      },
-    ];
+    const legacyNotifications = [makeStoredNotification('pre-devtools-notification')];
     fs.mkdirSync(path.dirname(legacyPath), { recursive: true });
     fs.writeFileSync(legacyPath, JSON.stringify(legacyNotifications), 'utf8');
 
@@ -153,17 +135,7 @@ describe('NotificationManager storage migration', () => {
       'claude-code-context-notifications.json'
     );
     const currentPath = path.join(home, '.claude', 'agent-teams-notifications.json');
-    const legacyNotifications = [
-      {
-        id: 'older-valid-notification',
-        title: 'Old',
-        message: 'Copied',
-        timestamp: new Date().toISOString(),
-        type: 'error',
-        isRead: false,
-        createdAt: Date.now(),
-      },
-    ];
+    const legacyNotifications = [makeStoredNotification('older-valid-notification')];
     fs.mkdirSync(path.dirname(invalidNewerLegacyPath), { recursive: true });
     fs.writeFileSync(invalidNewerLegacyPath, '', 'utf8');
     fs.writeFileSync(validOlderLegacyPath, JSON.stringify(legacyNotifications), 'utf8');
@@ -179,4 +151,61 @@ describe('NotificationManager storage migration', () => {
     ]);
     expect(JSON.parse(fs.readFileSync(currentPath, 'utf8'))).toEqual(legacyNotifications);
   });
+
+  it('recovers and compacts a notification history file with concatenated JSON', async () => {
+    const home = useTempHome();
+    const currentPath = path.join(home, '.claude', 'agent-teams-notifications.json');
+    const currentNotifications = [makeStoredNotification('current-valid-notification')];
+    const trailingNotifications = [makeStoredNotification('trailing-garbage-notification')];
+    fs.mkdirSync(path.dirname(currentPath), { recursive: true });
+    fs.writeFileSync(
+      currentPath,
+      `${JSON.stringify(currentNotifications, null, 2)}\n${JSON.stringify(trailingNotifications)}`,
+      'utf8'
+    );
+
+    const { NotificationManager } =
+      await import('../../../../src/main/services/infrastructure/NotificationManager');
+    const manager = new NotificationManager(createConfigManagerStub() as never);
+    await manager.initialize();
+
+    const result = await manager.getNotifications({ limit: 10 });
+    expect(result.notifications.map((notification) => notification.id)).toEqual([
+      'current-valid-notification',
+    ]);
+
+    await vi.waitFor(() => {
+      expect(JSON.parse(fs.readFileSync(currentPath, 'utf8'))).toEqual(currentNotifications);
+    });
+  });
+
+  it('keeps notification history valid after rapid consecutive saves', async () => {
+    const home = useTempHome();
+    const currentPath = path.join(home, '.claude', 'agent-teams-notifications.json');
+
+    const { NotificationManager } =
+      await import('../../../../src/main/services/infrastructure/NotificationManager');
+    const manager = new NotificationManager(createConfigManagerStub() as never);
+    await manager.initialize();
+
+    await Promise.all(
+      Array.from({ length: 20 }, (_, index) =>
+        manager.addTeamNotification({
+          teamEventType: 'user_inbox',
+          teamName: 'team-a',
+          teamDisplayName: 'Team A',
+          from: 'alice',
+          summary: `Message ${index}`,
+          body: `Message ${index}`,
+          dedupeKey: `rapid-save-${index}`,
+          suppressToast: true,
+        })
+      )
+    );
+
+    await vi.waitFor(() => {
+      const parsed = JSON.parse(fs.readFileSync(currentPath, 'utf8')) as Array<{ id: string }>;
+      expect(parsed).toHaveLength(20);
+    });
+  });
 });
diff --git a/test/main/services/infrastructure/NotificationManager.team.test.ts b/test/main/services/infrastructure/NotificationManager.team.test.ts
index 5b5236ae..2bddcc92 100644
--- a/test/main/services/infrastructure/NotificationManager.team.test.ts
+++ b/test/main/services/infrastructure/NotificationManager.team.test.ts
@@ -28,6 +28,8 @@ vi.mock('electron', () => ({
 vi.mock('fs/promises', () => ({
   readFile: vi.fn().mockRejectedValue({ code: 'ENOENT' }),
   writeFile: vi.fn().mockResolvedValue(undefined),
+  rename: vi.fn().mockResolvedValue(undefined),
+  rm: vi.fn().mockResolvedValue(undefined),
   mkdir: vi.fn().mockResolvedValue(undefined),
 }));