Since a Facebook cookie was added on prod, every reel came down titled
"Video": measured on dev, a signed-in read gives yt-dlp the placeholder
"Video" (an 18+ reel read as Chrome gives "Facebook") while the post's text
is still in the description. A new SourceAdapter.title hook takes the whole
first line of the description in that case, and both title writes (the early
fill and the finished download) go through it, so the row, the file name and
the share preview carry the post's text again. The line is not cut with an
ellipsis: normalize_title's NFKC turns "…" into "..." and collapses it to
".", which read as a finished sentence (seen in dev UAT).
The "Audio (MP3)" profile's extracted .mp3 was remuxed into an .mp4 by the
browser-safe step (the audio spec is clamped to container mp4 too) and served
as video/mp4, which iPad's WebKit will not play (prod job 268). Audio mode now
skips that step, so an .mp3 is served as audio/mpeg and an .m4a as audio/mp4.
Audio downloads version their cache identity on their own (v5), so a cached
remuxed audio re-derives without re-downloading every cached video.
peter
6169e32ca5