GET/PUT /api/admin/library/reacquisition, so every knob the sweeper reads is editable without a restart (rule #25). Routed under /library beside the missing-files list it governs rather than under /lidarr: Lidarr is the mechanism, but missing files are the problem the operator came to solve, and that is the surface they meet it on. The payload carries one thing the settings table doesn't: the count of albums with missing files that can never be auto-requested, because neither they nor their artist has an MBID. Nothing can be asked of Lidarr for a release MusicBrainz cannot name, and a feature that silently does nothing for part of its input reads as broken -- so the card states the number instead of leaving it to be inferred. Counted best-effort: the settings are the point of the endpoint, and failing the whole card because a count query hiccuped would be the wrong trade. Range errors come back as 400 naming the field. The Go-side validation mirrors migration 0056's CHECKs precisely so the operator reads "grace_hours must be 1-720" rather than a constraint-violation string surfacing as a 500.