The Discover tab fanned out its whole request set twice on every cold
start and replayed slow rows on a shrinking timeout ladder, so a healthy
remote server produced anywhere from 4s to 15s of loading.
Measured against a remote Jellyfin server with four libraries, 24
interleaved cold-start samples per side:
requests 19 -> 9 payload 219 KB -> 94 KB
settled 5231ms -> 2502ms median, 13222ms -> 5927ms p95
Four independent causes:
- Retry policy. `Client.send` resolves on response headers, so the
connect budget covers the server's think time and a slow-but-alive
query raises `connectionTimeout`. Replaying it made the server re-run
the query with a shorter budget than the one it just missed; the
`[10s, 8s, 5s]` ladder turned an 11s answer into an empty row after
23s. Hub surfaces now get one whole-request deadline, retry only
immediate connection errors, and the deadline bounds the whole call
including the request still in flight.
- Request shape. `/Items/Latest` groups a TV library by series, so its
rows are Series folder dtos and `RecursiveItemCount`/`ChildCount` cost
a DB count each, per row. Hub rows now ask for `Overview` only; watch
state survives because Jellyfin derives `UserData.Played` from
`UnplayedItemCount` when the count fields are absent. `/Shows/NextUp`
sends `NextUpDateCutoff` to bound the server's series-key scan, and
`Thumb` leaves `EnableImageTypes` since nothing reads it. `UserData`
and `PremiereDate` leave the browse set: neither is an `ItemFields`
member, so the server dropped them anyway.
- Fan-out. Per-library hubs ran in batches of three separated by a
barrier, so one slow library stalled every library behind it. A
sliding window keeps the same peak concurrency without head-of-line
blocking. Concurrent `fetchLibraries` calls now share one `/Views`
instead of racing two identical round trips, Plex's global and music
hub legs start together, and Jellyfin gets Plex's pool tuning.
- Duplicate pass. `DiscoverScreen.initState` starts a load and the
online-entry hook asked for a full refresh on top of it, which
`CoalescedLoadCoordinator` correctly queued as a trailing pass. The
hook now calls `primeRefresh`, which rides along with a load already
in flight; profile switches still go through `fullRefresh`.
Refs #1784
edde746