From 77dcdcd907d8c3049bb4b7aed33dfcb0e9a07b7e Mon Sep 17 00:00:00 2001
From: Anthony Ettinger <anthony@chovy.com>
Date: Tue, 23 Jun 2026 10:53:07 +0000
Subject: [PATCH] fix(web): disable adaptiveStream so the screen-share video
 isn't paused
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Web SFU viewers got the host's audio but a black screen for the screen share.
The room was created with adaptiveStream:true, which pauses video tracks that
livekit doesn't see attached to a visible element via track.attach(). The
viewer renders through a manually built MediaStream on a <video> srcObject, so
livekit never registers the element and paused the video at the SFU — audio
(unaffected by adaptiveStream) kept flowing, video stayed black.

Disable adaptiveStream: the viewer always shows the single presenter stream,
so there's nothing to adaptively pause. (Pairs with the prior fresh-MediaStream
-reference fix so Firefox actually re-binds srcObject when the video arrives.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 apps/web/src/hooks/useWebRTCSFU.test.ts | 18 +++++++++++++++++-
 apps/web/src/hooks/useWebRTCSFU.ts      | 10 ++++++++--
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/apps/web/src/hooks/useWebRTCSFU.test.ts b/apps/web/src/hooks/useWebRTCSFU.test.ts
index 2ec820d..d782df9 100644
--- a/apps/web/src/hooks/useWebRTCSFU.test.ts
+++ b/apps/web/src/hooks/useWebRTCSFU.test.ts
@@ -64,8 +64,12 @@ class MockRoom {
 
 let mockRoomInstance: MockRoom;
 
+// Capture the Room constructor options so we can assert adaptiveStream is off.
+const { roomCtorSpy } = vi.hoisted(() => ({ roomCtorSpy: vi.fn() }));
+
 vi.mock('livekit-client', () => ({
-  Room: vi.fn().mockImplementation(() => {
+  Room: vi.fn().mockImplementation((opts: unknown) => {
+    roomCtorSpy(opts);
     mockRoomInstance = new MockRoom();
     return mockRoomInstance;
   }),
@@ -167,4 +171,16 @@ describe('useWebRTCSFU', () => {
     expect(thirdStream?.getAudioTracks()).toHaveLength(0);
     expect(thirdStream?.getVideoTracks()).toHaveLength(1);
   });
+
+  it('creates the room with adaptiveStream disabled so screen-share video is not paused', async () => {
+    await act(async () => {
+      renderHook(() => useWebRTCSFU({ sessionId: 'session-1', participantId: 'viewer-1' }));
+      await Promise.resolve();
+      await Promise.resolve();
+      await Promise.resolve();
+      await Promise.resolve();
+    });
+
+    expect(roomCtorSpy).toHaveBeenCalledWith(expect.objectContaining({ adaptiveStream: false }));
+  });
 });
diff --git a/apps/web/src/hooks/useWebRTCSFU.ts b/apps/web/src/hooks/useWebRTCSFU.ts
index 39e86e0..eb276dd 100644
--- a/apps/web/src/hooks/useWebRTCSFU.ts
+++ b/apps/web/src/hooks/useWebRTCSFU.ts
@@ -357,9 +357,15 @@ export function useWebRTCSFU({
         data: { token: string; url: string; roomName: string };
       };
 
-      // Create and connect room
+      // Create and connect room.
+      // adaptiveStream pauses video tracks that livekit doesn't see attached to
+      // a visible element via track.attach(). We render through a manually built
+      // MediaStream on a <video> srcObject, so livekit never registers the
+      // element and would pause the screen-share video — audio keeps flowing,
+      // video stays black. Disable it: the viewer always shows the one presenter
+      // stream, so there's nothing to adaptively pause.
       const room = new Room({
-        adaptiveStream: true,
+        adaptiveStream: false,
         dynacast: true,
       });