Chromium throttles requestAnimationFrame in deeply nested cross-origin
iframes. In Claude desktop (Electron), the composition iframe's own rAF
loop stalls, so GSAP is never seeked and animation freezes even when
TransportClock.isPlaying() is true.
The correct fix is to drive ticks from the widget-frame rAF, which lives
one level up and is not subject to the same throttling. When play() takes
the runtime bridge path (no direct timeline adapter), the player now starts
a parent-frame rAF loop that sends "tick" postMessages to the composition
iframe on every frame. The runtime's control bridge handles "tick" by calling
seekTimelineAndAdapters(clock.now()) if the clock is playing — identical to
what transportTick does on each rAF, just driven from outside.
The composition iframe's own rAF loop is unchanged and keeps running
normally in standard browsers. Seeking GSAP twice per frame is idempotent,
so there is no regression on claude.ai or any other non-throttled environment.
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
The postMessage state path set `_currentTime` without clamping, while the
direct timeline path already used `Math.min(currentTime, _duration)`. A
final-frame state message with a frame count slightly past the end would
set `_currentTime > _duration`, causing the progress bar (position:
absolute, no overflow guard) to bleed out of the scrubber track and
visually cover the volume button, and the time display to show values
like "0:05 / 0:04".
- Clamp `_currentTime` in `_onMessage` to match the direct timeline path
- Clamp defensively in `updateTime` so the display layer never overflows
- Add `overflow: hidden` + `min-width: 0` to `.hfp-scrubber` as a CSS
safety net; remove now-redundant `border-radius` from `.hfp-progress`
(parent `overflow: hidden` handles clipping to the rounded shape)
- Apply the same `overflow: hidden` fix to `.hfp-volume-slider` for
consistency; remove redundant `border-radius` from `.hfp-volume-fill`
- Add regression test covering the postMessage over-duration case
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
