fix(tts): stop stale engine playback on switch

packages/core/src/stores/tts-store.test.ts

@@ -28,6 +28,7 @@ function createMockPlayer(): MockTTSPlayer {
   });
   player.stop = vi.fn(() => {
     player.onStateChange?.("stopped");
+    player.onEnd?.();
   });
   return player;
 }
@@ -235,4 +236,30 @@ describe("useTTSStore — re-speak on synth change (#370)", () => {
     expect(edgePlayer.speak).not.toHaveBeenCalled();
     expect(systemPlayer.speak).not.toHaveBeenCalled();
   });
+
+  it("[engine-switch] stops active playback without firing reader onEnd", () => {
+    const onEnd = vi.fn();
+    startEdge();
+    useTTSStore.getState().setOnEnd(onEnd);
+    edgePlayer.stop.mockClear();
+
+    useTTSStore.getState().updateConfig({ engine: "system" });
+
+    expect(edgePlayer.stop).toHaveBeenCalledOnce();
+    expect(edgePlayer.onEnd).toBeUndefined();
+    expect(onEnd).not.toHaveBeenCalled();
+    expect(useTTSStore.getState().playState).toBe("stopped");
+    expect(useTTSStore.getState().config.engine).toBe("system");
+  });
+
+  it("[engine-switch] does not stop playback for non-engine synth updates", () => {
+    startEdge();
+    edgePlayer.stop.mockClear();
+
+    useTTSStore.getState().updateConfig({ rate: 1.3 });
+
+    expect(edgePlayer.stop).not.toHaveBeenCalled();
+    expect(useTTSStore.getState().playState).toBe("playing");
+    expect(useTTSStore.getState().config.rate).toBe(1.3);
+  });
 });

packages/core/src/stores/tts-store.ts

@@ -373,10 +373,19 @@ export const useTTSStore = create<TTSState>()(
       updateConfig: (updates) => {
         const previousConfig = normalizeTTSConfig(get().config);
         const nextConfig = normalizeTTSConfig({ ...previousConfig, ...updates });
+        const engineChanged =
+          updates.engine !== undefined && nextConfig.engine !== previousConfig.engine;
+        const wasPlaying = isActivePlay(get().playState);
         set({ config: nextConfig });
 
-        // [占位 · #427/#349] engine 变化 + 播放中 → 停播。合并 #427 时在此插入，
-        // 并在该分支内调用 clearRespeakTimer()。
+        if (engineChanged && wasPlaying) {
+          clearRespeakTimer();
+          _sessionGeneration += 1;
+          detachAndStopAllPlayers();
+          _dashscopeActiveVoice = undefined;
+          set({ playState: "stopped" });
+          return;
+        }
 
         if (
           shouldRespeakForSynthChange(previousConfig, nextConfig) &&