Media sent in a conversation had nowhere to go: the composer capped every
file at 10 MiB and pushed it through a base64 RPC, video and audio blocks
did not render, and downloads decoded whole files in the page.
- Video and audio blocks play inline through MediaPlayer, which loads
nothing until the player is near the viewport, sizes the frame from the
block's dimensions (vertical clips stay within the column) and uses the
poster when one exists. Files the browser cannot play fall back to their
name with a download action.
- Images load straight from the artifact route; the lightbox gains a
download action.
- File cards, the Markdown preview and downloads read from the artifact
route instead of decoding base64.
- The composer accepts each kind up to its cap and names the computed
limit when it skips a file; video, audio and anything above the inline
cap upload as a raw stream, small files keep the inline RPC.
- MediaPlayer and artifactUrl are what the media card builds on.
Tests: MediaPlayer laziness, sizing and fallback, the upload helper, and an
E2E that uploads a tiny MP4 fixture (VP9, since Playwright's Chromium has
no H.264 decoder), plays it from the artifact route and captures
media-video-block, plus the image lightbox download.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MRtGG9ARfqqhma3t85Ro2u
979034a8a6