# Known gaps

Honest limits of release `2026-09.2`.

- **Changelog is empty.** First load. [`GET /v1/changes`](/docs/changes) will start filling on the next release.
- **Authors are sparse.** Some editions still return `authors: []`. Open Library keys are resolved to names on read when we can.
- **Subjects and edition metadata are sparse.** `publisher`, `publication_date`, `page_count`, `format` are often null.
- **Synopses cover a slice.** About **8.4M** of **78.2M** works have `description`.
- **Split works.** Open Library split some popular titles into several work ids. Match and search collapse those when the title is an exact hit.
- **One source.** Open Library only. Library of Congress and BookBrainz are not in this release.
- **Recommendations are content similarity**, not other readers’ shelves. About **1.28M** ISBN+synopsis works have embedding neighbors (~64M rows). Open Library ratings/reading-log counts bias ranking; that is not collaborative filtering. Seeds with no neighbor rows return `{ results: [] }` — no subject-keyword fallback.
- **Genre browse uses edition subjects.** `genre=fantasy` works when subjects mention fantasy/magic/etc. `Fiction, general` does not map to a facet.
- **Work merge is incremental.** Split `fds_wk_*` collapse in the fetch window today; aliases land in hash buckets, not a 78M re-ER.
- **Resale is prohibited.** Bulk dumps are for your own systems.

## What is solid

- ISBN-10 / ISBN-13 lookup
- Stable ids + 301 redirects
- Title resolution with article/apostrophe fold and summary/study-guide demotion
- Author search and content-based recommend
- MCP and REST sharing one key
- Check record: `9780593135204` *Project Hail Mary*