Android/iOS Chrome grey out audio files when the document provider reports a generic MIME (e.g. application/octet-stream for mp3 in Downloads), so accept="audio/*,video/*" alone hid them. Add explicit extension tokens (.mp3, .m4a, …) which mobile pickers honour by filename, un-greying them. Also surface upload success/failure on the button instead of silently resetting. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>