Compose row gains a 📎 attach button that uploads the file via /api/blob and calls mesh.send-content for the selected peer. Received content_ref bubbles render as a caption+filename card with either an inline image preview or a Download button that calls mesh.fetch-content and swaps in the returned local_url. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>