frontend/angular/src/app/features/player/player-shell.component.spec.ts

@@ -351,6 +351,37 @@ describe('PlayerShellComponent gameplay wiring', () => {
     component.ngOnDestroy();
   });
 
+  it('silences active media elements when secondary-device audio guard is installed', () => {
+    const pauseAudio = vi.fn();
+    const pauseVideo = vi.fn();
+    const audioElement = { muted: false, pause: pauseAudio };
+    const videoElement = { muted: false, pause: pauseVideo };
+    const querySelectorAll = vi.fn().mockReturnValue([audioElement, videoElement]);
+
+    vi.stubGlobal('document', { querySelectorAll });
+    vi.stubGlobal('window', {
+      location: { hash: '', search: '' },
+      history: { state: null, replaceState: vi.fn() },
+      localStorage: { getItem: vi.fn().mockReturnValue('en'), setItem: vi.fn(), removeItem: vi.fn() },
+      sessionStorage: { getItem: vi.fn().mockReturnValue(null), setItem: vi.fn(), removeItem: vi.fn() },
+      HTMLMediaElement: { prototype: { play: vi.fn().mockResolvedValue(undefined) } },
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+    });
+    vi.stubGlobal('navigator', { language: 'en-US', onLine: true });
+
+    const component = new PlayerShellComponent();
+    component.ngOnInit();
+
+    expect(querySelectorAll).toHaveBeenCalledWith('audio,video');
+    expect(audioElement.muted).toBe(true);
+    expect(videoElement.muted).toBe(true);
+    expect(pauseAudio).toHaveBeenCalledTimes(1);
+    expect(pauseVideo).toHaveBeenCalledTimes(1);
+
+    component.ngOnDestroy();
+  });
+
   it('installs secondary-device audio guard while player shell is mounted', async () => {
     const originalPlay = vi.fn().mockRejectedValue(new Error('original play'));
     const mediaPrototype = { play: originalPlay };

frontend/angular/src/app/features/player/player-shell.component.ts

@@ -24,6 +24,11 @@ type MediaPrototypeWithGuardState = {
   };
 };
 
+type GuardableMediaElement = {
+  muted?: boolean;
+  pause?: () => void;
+};
+
 function resolveLocalStorage(): Storage | undefined {
   if (typeof window === 'undefined') {
     return undefined;
@@ -202,6 +207,8 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
       return;
     }
 
+    this.silenceExistingMediaElements();
+
     const mediaPrototype = (window as Window & { HTMLMediaElement?: { prototype?: MediaPrototypeWithGuardState } }).HTMLMediaElement
       ?.prototype;
 
@@ -235,6 +242,26 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     };
   }
 
+  private silenceExistingMediaElements(): void {
+    if (typeof document === 'undefined' || typeof document.querySelectorAll !== 'function') {
+      return;
+    }
+
+    const activeElements = document.querySelectorAll('audio,video') as
+      | NodeListOf<GuardableMediaElement>
+      | GuardableMediaElement[]
+      | undefined;
+
+    if (!activeElements || typeof (activeElements as { forEach?: unknown }).forEach !== 'function') {
+      return;
+    }
+
+    activeElements.forEach((element) => {
+      element.muted = true;
+      element.pause?.();
+    });
+  }
+
   private scheduleStateSync(): void {
     this.clearStateSyncTimer();