fix: notify displaced tab when user joins voice from another session

When a user joins a voice channel while already connected from another
tab, the server now sends a 'displaced' reason on voice_disconnected.
The client tears down LiveKit and shows an informational toast.

packages/server/src/ws/events.ts

@@ -537,6 +537,14 @@ function handleVoiceJoin(event: Record<string, unknown>, userId: string): void {
   const left = connectionManager.leaveCurrentRoom(userId);
   if (left) {
     broadcastRoomLeave(left.roomId, left.room, userId);
+
+    // Notify all of the user's tabs so the displaced tab tears down LiveKit
+    connectionManager.sendToUser(userId, {
+      type: 'voice_disconnected',
+      userId,
+      channelId: left.roomId,
+      reason: 'displaced',
+    });
   }
 
   // Cancel any ringing DM rooms where this user is the caller

packages/shared/src/types.ts

@@ -330,7 +330,7 @@ export type ServerEvent =
   | { type: 'voice_space_deafened'; userId: string; channelId: string; spaceId: string; deafened: boolean }
   | { type: 'voice_permission_muted'; userId: string; spaceId: string; muted: boolean }
   | { type: 'voice_moved'; userId: string; oldChannelId: string; newChannelId: string }
-  | { type: 'voice_disconnected'; userId: string; channelId: string }
+  | { type: 'voice_disconnected'; userId: string; channelId: string; reason?: 'displaced' }
   | { type: 'user_updated'; user: User }
   | { type: 'member_banned'; spaceId: string; reason: string | null }
   | { type: 'category_created'; category: ChannelCategory; spaceId: string }

packages/web/src/hooks/useWebSocket.ts

@@ -9,6 +9,8 @@ import type { ServerEvent, ClientEvent, ActiveCallInfo } from '@backspace/shared
 import { resolveAssetUrl, normalizeUserAssets, normalizeMessageAssets } from '../utils/assetUrls';
 import { broadcastVoiceStatus, broadcastDeafenViaLiveKit } from '../utils/voice';
 import { registerSelfId } from '../utils/identity';
+import { getActiveRoom } from './useLiveKit';
+import { useUIStore } from '../stores/uiStore';
 
 // ─── Connection state ─────────────────────────────────────────────────────────
 
@@ -428,7 +430,14 @@ function handleEvent(origin: string, event: ServerEvent): void {
     case 'voice_disconnected': {
       const myDisconnectId = isHome ? useAuthStore.getState().user?.id : getMyUserIdForOrigin(origin);
       if (event.userId === myDisconnectId) {
+        const { currentVoiceChannelId } = useVoiceStore.getState();
+        if (event.channelId === currentVoiceChannelId) {
           useVoiceStore.getState().handleForceDisconnect();
+          getActiveRoom()?.disconnect();
+          if (event.reason === 'displaced') {
+            useUIStore.getState().addToast('Voice disconnected — joined from another session', 'info');
+          }
+        }
       }
       break;
     }