The user-triggered "get full history" (backfill_channel_now) capped at
max_pages=60 = 3000 videos. A channel just over that (BBC Earth: 3403
uploads = 69 pages) stopped one page short, so its tail dribbled in over
the scheduler's paced 10-minute ticks (250 videos/tick) and the button
spinner looked stuck for ~18 minutes with no visible progress.
- Raise the immediate cap to max_pages=400 (20 000 videos) so any
realistic channel completes in the single background run.
- Make a high cap safe: backfill_channel_deep now re-checks the shared
quota before each page and yields at the backfill reserve (previously
quota was checked once by the caller before the whole run), and commits
the advanced cursor after every page so a restart resumes instead of
re-fetching — and re-charging quota for — pages already stored.
- Channel page: while loading, the button shows the live stored/total
count and a tooltip explaining the tail finishes in the background, so a
very large channel's paced remainder reads as progress, not a hang.
Adds deep-backfill paging tests (per-page cursor commit + resume, and the
per-page quota yield).
- Make the immediate-backfill guard SYMMETRIC: run_deep_backfill now also
registers the channel it pages in _backfill_in_progress, so it and
backfill_channel_now mutually exclude per-channel and never advance the
same cursor concurrently (whichever started first). The interactive cap
moves to a separate _immediate_running counter so the scheduler's channels
don't false-trip it.
- Attribute the immediate backfill's spend: wrap it in
quota.attribute(user_id, VIDEOS_BACKFILL_FULL) (route passes user.id), so
it shows under the user's full-backfill action, not the OTHER/system bucket.
- Tests: the update_channel->background-task wiring + the demo guard
(scheduled for a real user, NOT for demo); distinct N/S/L counts (2 short
+ 1 live) so a short/live swap fails; extracted channelDetailPollMs with a
pure unit test of the poll-or-stop predicate.
- a11y: role="img" on the fully-synced charm so screen readers announce it.
- list_channels no longer computes the Normal/Shorts/Live aggregation the
frontend stopped reading when R14 dropped the N/S/L table column; the dead
ManagedChannel.count_* fields are gone too.
- Immediate "get full history" backfill now coordinates with the paced
scheduler via a small in-flight set: capped at 2 concurrent + per-channel
dedup, and run_deep_backfill skips a channel an immediate backfill owns —
killing the cursor race and bounding the quota-drain burst, without losing
the speed win.
- Add test_channel_backfill.py: the channelDetail N/S/L counts + the guard's
no-op / cap / scheduler-skip behaviour.
- Inline the syncedChannels useMemo (its dep is a fresh array each render, so
it never cached); fix the stale "~2-min ticks" comment (it's 10 minutes).
peter