Courses flagged Hide in API Response in the Courses List sheet (hideinapi), and all of their lessons, are omitted from every /api/library/* response and from its counts; single-item lookups answer 404 for them. Only the session-gated internal endpoints see the full catalog.

GET /api/library/meta says when the canonicalization columns were last recomputed and by what (see Catalog Meta). Near-duplicate candidate groups (duplicate_reason: near_duplicate) sit in Commune's internal review queue until a human merges them or rules them distinct; nothing is merged automatically.