diff --git a/src/lib/webrtc/broadcaster.ts b/src/lib/webrtc/broadcaster.ts
index 4a0fb54..d4aa4a3 100644
--- a/src/lib/webrtc/broadcaster.ts
+++ b/src/lib/webrtc/broadcaster.ts
@@ -97,10 +97,18 @@ export async function startBroadcast(stream: MediaStream): Promise<BroadcasterHa
 
   channel = joinSignalingChannel(code, handleMessage);
 
+  // Track the active stream so we can swap it on the fly
+  let activeStream: MediaStream = stream;
+
   // Stop when the underlying stream ends
-  stream.getTracks().forEach((t) => {
-    t.addEventListener('ended', () => stop());
-  });
+  const attachEndedListeners = (s: MediaStream) => {
+    s.getTracks().forEach((t) => {
+      t.addEventListener('ended', () => {
+        if (s === activeStream) stop();
+      });
+    });
+  };
+  attachEndedListeners(stream);
 
   let stopped = false;
   const stop = async () => {
@@ -113,9 +121,27 @@ export async function startBroadcast(stream: MediaStream): Promise<BroadcasterHa
     await supabase.from('share_rooms').update({ is_active: false, viewer_count: 0 }).eq('code', code);
   };
 
+  const replaceVideoTrack = async (newStream: MediaStream) => {
+    const newVideo = newStream.getVideoTracks()[0];
+    if (!newVideo) return;
+    activeStream = newStream;
+    attachEndedListeners(newStream);
+    for (const pc of peers.values()) {
+      const sender = pc.getSenders().find((s) => s.track && s.track.kind === 'video');
+      if (sender) {
+        try {
+          await sender.replaceTrack(newVideo);
+        } catch (e) {
+          console.warn('[broadcaster] replaceTrack failed', e);
+        }
+      }
+    }
+  };
+
   return {
     code,
     stop,
+    replaceVideoTrack,
     onViewerCountChange: (cb) => {
       listeners.add(cb);
       cb(peers.size);