fix(notification): replace repeated desktop status toasts

- Add optional replaceId to showDesktopNotification; a repeated id closes the prior toast instead of stacking a new one
- Character dictionary auto-sync now shares one replaceId across checking/generating/importing/ready phases
- Startup OSD sequencer passes its lane id as replaceId so each startup lane keeps a single live notification

src/core/utils/notification.ts

@@ -52,9 +52,15 @@ function resolveRuntimeDefaultNotificationIconPath(): string | null {
   });
 }
 
+/**
+ * Live notifications keyed by `replaceId`. Electron exposes no native "replace this notification"
+ * flag, so a repeated status closes its predecessor instead of stacking a fresh toast per update.
+ */
+const notificationsByReplaceId = new Map<string, Electron.Notification>();
+
 export function showDesktopNotification(
   title: string,
-  options: { body?: string; icon?: string },
+  options: { body?: string; icon?: string; replaceId?: string },
 ): void {
   const notificationOptions: {
     title: string;
@@ -98,5 +104,15 @@ export function showDesktopNotification(
   }
 
   const notification = new Notification(notificationOptions);
+  const replaceId = options.replaceId?.trim();
+  if (replaceId) {
+    notificationsByReplaceId.get(replaceId)?.close();
+    notificationsByReplaceId.set(replaceId, notification);
+    notification.once('close', () => {
+      if (notificationsByReplaceId.get(replaceId) === notification) {
+        notificationsByReplaceId.delete(replaceId);
+      }
+    });
+  }
   notification.show();
 }

src/main/runtime/character-dictionary-auto-sync-notifications.test.ts

@@ -214,3 +214,69 @@ test('auto sync notifications let startup sequencer own osd-system desktop deliv
 
   assert.deepEqual(calls, ['osd:importing', 'desktop:SubMiner:importing']);
 });
+
+test('auto sync desktop notifications reuse one replace id across every phase', () => {
+  const replaceIds: Array<string | undefined> = [];
+  const deps = {
+    getNotificationType: () => 'system' as const,
+    showOsd: () => undefined,
+    showDesktopNotification: (_title: string, options: { body?: string; replaceId?: string }) => {
+      replaceIds.push(options.replaceId);
+    },
+  };
+
+  for (const phase of ['checking', 'generating', 'importing', 'ready'] as const) {
+    notifyCharacterDictionaryAutoSyncStatus(makeEvent(phase, phase), deps);
+  }
+
+  assert.deepEqual(replaceIds, [
+    'character-dictionary-auto-sync',
+    'character-dictionary-auto-sync',
+    'character-dictionary-auto-sync',
+    'character-dictionary-auto-sync',
+  ]);
+});
+
+test('overlay-unavailable desktop fallback shares the same replace id', () => {
+  const replaceIds: Array<string | undefined> = [];
+
+  notifyCharacterDictionaryAutoSyncStatus(makeEvent('generating', 'generating'), {
+    getNotificationType: () => 'overlay',
+    showOsd: () => undefined,
+    showDesktopNotification: (_title, options) => {
+      replaceIds.push(options.replaceId);
+    },
+  });
+
+  assert.deepEqual(replaceIds, ['character-dictionary-auto-sync']);
+});
+
+test('startup lanes keep one desktop notification per lane', () => {
+  const calls: Array<{ body?: string; replaceId?: string }> = [];
+  const sequencer = createStartupOsdSequencer({
+    getNotificationType: () => 'system',
+    showOsd: () => undefined,
+    showDesktopNotification: (_title, options) => {
+      calls.push(options);
+    },
+  });
+
+  sequencer.markTokenizationReady();
+  notifyCharacterDictionaryAutoSyncStatus(makeEvent('generating', 'generating one'), {
+    getNotificationType: () => 'osd',
+    showOsd: () => undefined,
+    showDesktopNotification: () => undefined,
+    startupOsdSequencer: sequencer,
+  });
+  notifyCharacterDictionaryAutoSyncStatus(makeEvent('generating', 'generating two'), {
+    getNotificationType: () => 'osd',
+    showOsd: () => undefined,
+    showDesktopNotification: () => undefined,
+    startupOsdSequencer: sequencer,
+  });
+
+  assert.deepEqual(
+    calls.map((call) => call.replaceId),
+    ['startup-status', 'startup-status'],
+  );
+});

src/main/runtime/character-dictionary-auto-sync-notifications.ts

@@ -9,7 +9,7 @@ export interface CharacterDictionaryAutoSyncNotificationDeps {
   getNotificationType: () => NotificationType | undefined;
   showOsd: (message: string) => boolean | void;
   showOverlayNotification?: (payload: OverlayNotificationPayload) => void;
-  showDesktopNotification: (title: string, options: { body?: string }) => void;
+  showDesktopNotification: (title: string, options: { body?: string; replaceId?: string }) => void;
   startupOsdSequencer?: {
     notifyCharacterDictionaryStatus: (
       event: StartupOsdSequencerCharacterDictionaryEvent,
@@ -17,6 +17,10 @@ export interface CharacterDictionaryAutoSyncNotificationDeps {
   };
 }
 
+// One live desktop notification for the whole sync: progress updates replace each other and the
+// terminal ready/failed message replaces the last progress one, matching the overlay toast.
+const CHARACTER_DICTIONARY_DESKTOP_NOTIFICATION_ID = 'character-dictionary-auto-sync';
+
 function isTerminalPhase(phase: CharacterDictionaryAutoSyncNotificationEvent['phase']): boolean {
   return phase === 'ready' || phase === 'failed';
 }
@@ -53,7 +57,10 @@ export function notifyCharacterDictionaryAutoSyncStatus(
         persistent: !isTerminalPhase(event.phase),
       });
     } else if (!shouldShowDesktop(type)) {
-      deps.showDesktopNotification('SubMiner', { body: event.message });
+      deps.showDesktopNotification('SubMiner', {
+        body: event.message,
+        replaceId: CHARACTER_DICTIONARY_DESKTOP_NOTIFICATION_ID,
+      });
     }
   }
 
@@ -69,6 +76,9 @@ export function notifyCharacterDictionaryAutoSyncStatus(
   }
 
   if (shouldShowDesktop(type) && !startupSequencerShown) {
-    deps.showDesktopNotification('SubMiner', { body: event.message });
+    deps.showDesktopNotification('SubMiner', {
+      body: event.message,
+      replaceId: CHARACTER_DICTIONARY_DESKTOP_NOTIFICATION_ID,
+    });
   }
 }

src/main/runtime/startup-osd-sequencer.ts

@@ -10,7 +10,7 @@ export interface StartupOsdSequencerDeps {
   getNotificationType?: () => NotificationType | undefined;
   showOsd: (message: string) => boolean | void;
   showOverlayNotification?: (payload: OverlayNotificationPayload) => void;
-  showDesktopNotification?: (title: string, options: { body?: string }) => void;
+  showDesktopNotification?: (title: string, options: { body?: string; replaceId?: string }) => void;
 }
 
 interface StartupStatusNotificationOptions {
@@ -62,7 +62,11 @@ export function createStartupOsdSequencer(deps: StartupOsdSequencerDeps): {
       shown = deps.showOsd(options.message) !== false || shown;
     }
     if (options.desktop !== false && shouldShowDesktop(type)) {
-      deps.showDesktopNotification?.('SubMiner', { body: options.message });
+      // Each startup lane keeps one live desktop notification instead of one per update.
+      deps.showDesktopNotification?.('SubMiner', {
+        body: options.message,
+        replaceId: options.id,
+      });
       shown = true;
     }
     return shown;