fix(call): volume>100% crash, picker UI freeze, native-path diagnostics

Volume crash:
- setParticipantVolume / setScreenShareVolume propagated values up to 2.0
(200%) to the per-track GainNode, but also called applyToAttachedElements
which set the raw HTMLAudioElement.volume — that property is hard-clamped
to [0, 1] and throws IndexSizeError above 1. Clip the element-path apply
at 1.0. WebAudio GainNode keeps doing the actual amplification.

Picker freeze:
- Firing ~20 captureScreenSourceThumbnail invokes in parallel caused
perceptible input freezes while each ~100KB base64 result arrived and
triggered a setState. Bounded the worker pool to 4 concurrent captures
with a queue — overall wall-clock is nearly identical and the grid stays
scrollable / clickable throughout the load.

Native-path diagnostics:
- Previous logs only fired on non-NativeCaptureUnavailable errors, so
users couldn't tell whether the native path was skipped (audio toggle
on, no sourceId) or attempted-and-failed. Added explicit info logs for
each skip reason plus an always-on warn with the underlying error when
the try block throws. Makes the next debug pass on screenshare much
quicker.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop/src/components/ScreenSourcePicker.tsx

@@ -49,10 +49,11 @@ export function ScreenSourcePicker({ open, onClose, onStart }: Props) {
   const [error, setError] = useState<string | null>(null);
 
   // Two-phase load: (1) fast list returns names + placeholders so the grid
-  // paints instantly, (2) fire one thumbnail capture per source in
-  // parallel. Thumbnails fill in as each capture completes — Tauri's
-  // command thread pool runs them concurrently so wall-clock is bounded
-  // by the slowest source, not the sum.
+  // paints instantly, (2) capture thumbnails in a bounded worker-pool so
+  // Tauri IPC returns don't starve the JS main thread. Firing all ~20
+  // captures at once caused perceptible input freezes while the base64
+  // blobs arrived — limiting concurrency to 4 keeps the grid scrollable
+  // throughout and doesn't meaningfully slow overall completion.
   useEffect(() => {
     if (!open) {
       setSources(null);
@@ -61,18 +62,18 @@ export function ScreenSourcePicker({ open, onClose, onStart }: Props) {
       return;
     }
     let cancelled = false;
+    const CONCURRENCY = 4;
     void (async () => {
       const list = await listScreenSources();
       if (cancelled) return;
       setSources(list);
-      // Fan out thumbnail captures. No Promise.all — we want each result
-      // to render as it lands, not wait for the full batch. The id-based
-      // setState patch means the slowest source can still be in flight
-      // while the user already picked one of the fast ones.
-      for (const src of list) {
+
+      const queue = [...list];
+      const pickOne = (src: typeof list[number]) => {
         void (async () => {
           const png = await captureScreenSourceThumbnail(src.id);
-          if (cancelled || png === null) return;
+          if (cancelled) return;
+          if (png !== null) {
             setSources((prev) => {
               if (!prev) return prev;
               const idx = prev.findIndex((s) => s.id === src.id);
@@ -81,7 +82,14 @@ export function ScreenSourcePicker({ open, onClose, onStart }: Props) {
               next[idx] = { ...prev[idx]!, thumbnailPng: png };
               return next;
             });
+          }
+          const nextSrc = queue.shift();
+          if (nextSrc) pickOne(nextSrc);
         })();
+      };
+      for (let i = 0; i < Math.min(CONCURRENCY, queue.length); i++) {
+        const s = queue.shift();
+        if (s) pickOne(s);
       }
     })();
     return () => {

apps/desktop/src/context/CallContext.tsx

@@ -1196,8 +1196,18 @@ export function CallProvider({ children }: { children: ReactNode }) {
       // completely skips the OS picker. Video-only (no system audio yet);
       // if the user asked for audio we fall through to the legacy paths
       // below so audio still works via getDisplayMedia.
+      if (!sourceId) {
+        console.info(
+          'screen-share: no sourceId supplied by picker, OS picker will open',
+        );
+      } else if (settings.includeSystemAudio) {
+        console.info(
+          'screen-share: system audio requested — native path unavailable (needs WASAPI/ScreenCaptureKit), OS picker will open',
+        );
+      }
       if (sourceId && !settings.includeSystemAudio) {
         try {
+          console.info('screen-share: trying native capture path', { sourceId, fps });
           const { Track: LkTrack } = await import('livekit-client');
           const maxWidth = ssParams.dims?.width ?? 1920;
           const maxHeight = ssParams.dims?.height ?? 1080;
@@ -1236,6 +1246,7 @@ export function CallProvider({ children }: { children: ReactNode }) {
               setIsScreenSharing(false);
             })();
           });
+          console.info('screen-share: native capture active');
           setIsScreenSharing(true);
           return;
         } catch (err: unknown) {
@@ -1246,9 +1257,10 @@ export function CallProvider({ children }: { children: ReactNode }) {
             await nativeCaptureRef.current.stop().catch(() => undefined);
             nativeCaptureRef.current = null;
           }
-          if (!(err instanceof NativeCaptureUnavailable)) {
-            console.warn('native screen-capture failed, falling back', err);
-          }
+          console.warn(
+            'screen-share: native path failed, falling back',
+            err instanceof Error ? err.message : err,
+          );
         }
       }
 

apps/desktop/src/lib/participantVolumes.ts

@@ -78,12 +78,18 @@ export function subscribeParticipantVolumes(fn: Listener): () => void {
 
 // Apply a volume to any audio elements already attached for this user.
 // Attached elements are tagged with `data-participant` in attachTrack.
+// HTMLMediaElement.volume is hard-clamped to [0, 1] — anything above 1
+// throws IndexSizeError. Values above 1 are only meaningful on the
+// WebAudio path (remoteAudioPipelines' GainNode handles them); on the
+// plain-element fallback path we clip at 1.0 so the user just hears the
+// loudest level the element supports rather than an exception.
 function applyToAttachedElements(userId: string, volume: number): void {
+  const elVolume = Math.min(1, Math.max(0, volume));
   const nodes = document.querySelectorAll<HTMLAudioElement>(
     'audio[data-participant="' + cssEscape(userId) + '"]',
   );
   nodes.forEach((el) => {
-    el.volume = volume;
+    el.volume = elVolume;
   });
 }
 

apps/desktop/src/lib/screenShareVolumes.ts

@@ -60,15 +60,18 @@ export function clearScreenShareVolumes(): void {
 // elements are tagged by attachTrack in CallContext with
 // `data-participant="<identity>"` + `data-track-source="screenshare"` — the
 // combined selector makes sure we don't retarget the mic audio for the same
-// user (different track-source).
+// user (different track-source). HTMLMediaElement.volume caps at 1.0, so
+// clip here — the WebAudio GainNode on the live pipeline handles values
+// above 1.
 function applyToAttachedElements(userId: string, volume: number): void {
+  const elVolume = Math.min(1, Math.max(0, volume));
   const nodes = document.querySelectorAll<HTMLAudioElement>(
     'audio[data-participant="' +
       cssEscape(userId) +
       '"][data-track-source="screenshare"]',
   );
   nodes.forEach((el) => {
-    el.volume = volume;
+    el.volume = elVolume;
   });
 }