diff --git a/packages/web/src/components/voice/PictureInPicture.tsx b/packages/web/src/components/voice/PictureInPicture.tsx
index 1a2e839a..43955f58 100644
--- a/packages/web/src/components/voice/PictureInPicture.tsx
+++ b/packages/web/src/components/voice/PictureInPicture.tsx
@@ -122,17 +122,26 @@ export function PictureInPicture() {
     return 'Call';
   }, [currentVoiceChannelId, channels]);
 
-  // Video track attachment
+  // Derive the LiveKit Track from the selected stream's participant
+  const lkTrack = selectedStream
+    ? (selectedStream.type === 'screen'
+        ? selectedStream.participant.lkScreenTrack
+        : selectedStream.participant.lkVideoTrack)
+    : null;
+
+  // Video track attachment — use LiveKit's track.attach() to register the element
+  // with the adaptive stream observer (enables SFU layer switching by viewport size)
   // shouldShow in deps ensures re-run when PiP becomes visible (videoRef was null before)
   useEffect(() => {
     const videoEl = videoRef.current;
     if (!videoEl) return;
-    if (selectedStream?.track) {
-      videoEl.srcObject = new MediaStream([selectedStream.track]);
+    if (lkTrack) {
+      lkTrack.attach(videoEl);
+      return () => { lkTrack.detach(videoEl); };
     } else {
       videoEl.srcObject = null;
     }
-  }, [selectedStream?.track, shouldShow]);
+  }, [lkTrack, shouldShow]);
 
   // Initialize position to bottom-right
   useEffect(() => {
diff --git a/packages/web/src/components/voice/StreamTile.tsx b/packages/web/src/components/voice/StreamTile.tsx
index c679a500..b4236887 100644
--- a/packages/web/src/components/voice/StreamTile.tsx
+++ b/packages/web/src/components/voice/StreamTile.tsx
@@ -29,6 +29,7 @@ export function StreamTile({ tile, large }: StreamTileProps) {
   const isStreamMuted = streamMutes.get(userId) ?? false;
 
   const liveScreenTrack = tile.screenTrack?.readyState === 'live' ? tile.screenTrack : null;
+  const liveLkScreenTrack = liveScreenTrack ? tile.lkScreenTrack : null;
 
   // Quality badge state
   const [qualityBadge, setQualityBadge] = useState<string>('');
@@ -37,16 +38,18 @@ export function StreamTile({ tile, large }: StreamTileProps) {
   const [contextMenu, setContextMenu] = useState<{ x: number; y: number } | null>(null);
   const [qualityPopoverOpen, setQualityPopoverOpen] = useState(false);
 
-  // --- VIDEO ---
+  // --- VIDEO --- use LiveKit's track.attach() to register the element
+  // with the adaptive stream observer (enables SFU layer switching by viewport size)
   useEffect(() => {
     const videoEl = videoRef.current;
     if (!videoEl) return;
-    if (liveScreenTrack) {
-      videoEl.srcObject = new MediaStream([liveScreenTrack]);
+    if (liveLkScreenTrack) {
+      liveLkScreenTrack.attach(videoEl);
+      return () => { liveLkScreenTrack.detach(videoEl); };
     } else {
       videoEl.srcObject = null;
     }
-  }, [liveScreenTrack]);
+  }, [liveLkScreenTrack]);
 
   // Quality badge (poll every 3s)
   useEffect(() => {
diff --git a/packages/web/src/components/voice/VoiceUser.tsx b/packages/web/src/components/voice/VoiceUser.tsx
index cd022ecc..85a25f34 100644
--- a/packages/web/src/components/voice/VoiceUser.tsx
+++ b/packages/web/src/components/voice/VoiceUser.tsx
@@ -34,16 +34,19 @@ export function VoiceUser({ tile, large }: VoiceUserProps) {
     return () => tile.videoTrack?.removeEventListener('ended', onEnded);
   }, [tile.videoTrack]);
 
-  // Attach Video
+  // Attach Video — use LiveKit's track.attach() to register the element
+  // with the adaptive stream observer (enables SFU layer switching by viewport size)
   useEffect(() => {
     const videoEl = videoRef.current;
     if (!videoEl) return;
-    if (activeVideoTrack) {
-      videoEl.srcObject = new MediaStream([activeVideoTrack]);
+    const lkTrack = tile.lkVideoTrack;
+    if (lkTrack) {
+      lkTrack.attach(videoEl);
+      return () => { lkTrack.detach(videoEl); };
     } else {
       videoEl.srcObject = null;
     }
-  }, [activeVideoTrack]);
+  }, [tile.lkVideoTrack]);
 
   // Context Menu
   const [volumeMenu, setVolumeMenu] = useState<{
diff --git a/packages/web/src/hooks/useLiveKit.ts b/packages/web/src/hooks/useLiveKit.ts
index 6cc57014..c442a321 100644
--- a/packages/web/src/hooks/useLiveKit.ts
+++ b/packages/web/src/hooks/useLiveKit.ts
@@ -46,6 +46,8 @@ export interface ParticipantInfo {
   videoTrack: MediaStreamTrack | null;
   screenTrack: MediaStreamTrack | null;
   screenAudioTrack: MediaStreamTrack | null;
+  lkVideoTrack: Track | null;   // LiveKit Track for attach/detach (adaptive stream)
+  lkScreenTrack: Track | null;  // LiveKit Track for attach/detach (adaptive stream)
 }
 
 export interface UserTile {
@@ -54,6 +56,7 @@ export interface UserTile {
   participant: ParticipantInfo;
   videoTrack: MediaStreamTrack | null; // camera only
   audioTrack: MediaStreamTrack | null; // mic
+  lkVideoTrack: Track | null;         // LiveKit Track for attach/detach
 }
 
 export interface StreamTile {
@@ -62,6 +65,7 @@ export interface StreamTile {
   participant: ParticipantInfo;
   screenTrack: MediaStreamTrack | null;
   screenAudioTrack: MediaStreamTrack | null;
+  lkScreenTrack: Track | null;        // LiveKit Track for attach/detach
 }
 
 export type GridTile = UserTile | StreamTile;
@@ -69,12 +73,14 @@ export type GridTile = UserTile | StreamTile;
 export function deriveGridTiles(participants: ParticipantInfo[]): GridTile[] {
   const tiles: GridTile[] = [];
   for (const p of participants) {
+    const hasLiveVideo = p.isCameraOn && p.videoTrack?.readyState === 'live';
     tiles.push({
       kind: 'user',
       key: p.identity,
       participant: p,
-      videoTrack: (p.isCameraOn && p.videoTrack?.readyState === 'live') ? p.videoTrack : null,
+      videoTrack: hasLiveVideo ? p.videoTrack : null,
       audioTrack: p.audioTrack,
+      lkVideoTrack: hasLiveVideo ? p.lkVideoTrack : null,
     });
     if (p.isScreenSharing) {
       tiles.push({
@@ -83,6 +89,7 @@ export function deriveGridTiles(participants: ParticipantInfo[]): GridTile[] {
         participant: p,
         screenTrack: p.screenTrack,
         screenAudioTrack: p.screenAudioTrack,
+        lkScreenTrack: p.lkScreenTrack,
       });
     }
   }
@@ -149,6 +156,8 @@ export function useLiveKit() {
       let videoTrack: MediaStreamTrack | null = null;
       let screenTrack: MediaStreamTrack | null = null;
       let screenAudioTrack: MediaStreamTrack | null = null;
+      let lkVideoTrack: Track | null = null;
+      let lkScreenTrack: Track | null = null;
       let hasScreenSharePublication = false;
       p.trackPublications.forEach((pub) => {
         // Detect screen share publication even if unsubscribed
@@ -164,8 +173,8 @@ export function useLiveKit() {
         if (!mt || mt.readyState !== 'live') return;
 
         if (pub.source === Track.Source.Microphone) audioTrack = mt;
-        else if (pub.source === Track.Source.Camera && p.isCameraEnabled) videoTrack = mt;
-        else if (pub.source === Track.Source.ScreenShare) screenTrack = mt;
+        else if (pub.source === Track.Source.Camera && p.isCameraEnabled) { videoTrack = mt; lkVideoTrack = track; }
+        else if (pub.source === Track.Source.ScreenShare) { screenTrack = mt; lkScreenTrack = track; }
         else if (pub.source === Track.Source.ScreenShareAudio) screenAudioTrack = mt;
       });
 
@@ -194,6 +203,8 @@ export function useLiveKit() {
         videoTrack,
         screenTrack,
         screenAudioTrack,
+        lkVideoTrack,
+        lkScreenTrack,
       });
     };
     processParticipant(r.localParticipant, true);
diff --git a/packages/web/src/utils/screenShare.ts b/packages/web/src/utils/screenShare.ts
index 4c7f19a4..bb8851bc 100644
--- a/packages/web/src/utils/screenShare.ts
+++ b/packages/web/src/utils/screenShare.ts
@@ -18,7 +18,7 @@ export interface OverdriveOptions {
 
 export interface ScreenShareBuildResult {
   capture: { width: number; height: number; frameRate: number };
-  publish: { videoCodec: 'h264'; videoEncoding: { maxBitrate: number; maxFramerate: number }; simulcast: false };
+  publish: { videoCodec: 'vp9'; videoEncoding: { maxBitrate: number; maxFramerate: number }; simulcast: false };
   overdrive: OverdriveOptions;
   contentHint: 'motion' | 'detail';
 }
@@ -63,7 +63,7 @@ export function buildScreenShareOptions(config: ScreenShareConfig): ScreenShareB
   return {
     capture: { width, height, frameRate: fps },
     publish: {
-      videoCodec: 'h264',
+      videoCodec: 'vp9',
       videoEncoding: { maxBitrate, maxFramerate: fps },
       simulcast: false,
     },
@@ -99,14 +99,19 @@ export async function applyOverdrive(
     if (!sender) return;
 
     const params = sender.getParameters();
-    if (!params.encodings?.[0]) return;
+    if (!params.encodings?.length) return;
 
-    params.encodings[0].maxBitrate = options.maxBitrate;
-    params.encodings[0].maxFramerate = options.maxFramerate;
-    params.encodings[0].networkPriority = 'high';
+    // Target the highest-quality layer. With simulcast, encodings[0] is the
+    // lowest layer; our overdrive must hit the top layer so the custom bitrate
+    // slider controls the full-resolution stream, not the quarter-res one.
+    // For non-simulcast tracks (single encoding), length - 1 === 0.
+    const idx = params.encodings.length - 1;
+    params.encodings[idx]!.maxBitrate = options.maxBitrate;
+    params.encodings[idx]!.maxFramerate = options.maxFramerate;
+    params.encodings[idx]!.networkPriority = 'high';
     (params as any).degradationPreference = options.degradationPreference;
     if (options.minBitrate > 0) {
-      (params.encodings[0] as any).minBitrate = options.minBitrate;
+      (params.encodings[idx] as any).minBitrate = options.minBitrate;
     }
 
     await sender.setParameters(params);
@@ -134,9 +139,9 @@ export async function startScreenShare(room: Room): Promise<boolean> {
       // @ts-ignore — LiveKit accepts frameRate at capture level
       frameRate: opts.capture.frameRate,
     }, {
-      videoCodec: 'h264',
+      videoCodec: opts.publish.videoCodec,
       videoEncoding: opts.publish.videoEncoding,
-      simulcast: false,
+      simulcast: opts.publish.simulcast,
     } as any);
 
     if (!track) {