sqlite-utils 4.0rc2 was written almost entirely by Claude Fable

Category: Agentic coding
Status: discussion
Sources: Simon Willison, HN discussion
Summary: Simon Willison published a 2026-07-05 write-up of shipping sqlite-utils 4.0rc2, a release that reworks transaction handling (automatic commits for writes, db.begin()/db.commit()/db.rollback(), transactional migrations) and was built across 37 prompts, 34 commits, and roughly 1,321 added and 190 removed lines over 30 files. He reports the run cost 149.25 US dollars tracked through the API, prompted the model to do a final pre-ship review that surfaced five bugs including a data-loss defect in delete_where(), and used GPT-5.5 to review the model's own changes.
Comments: Willison states that having one model review another model's work does help in practice and that he should have pushed more work onto cheaper subagent models to cut cost.
Why it matters: It is a documented, costed account from a practitioner of an agent carrying most of a real library release, including a cross-model review step that caught a data-loss bug.
Follow-up: Watch whether cross-model review as a ship gate and per-session cost accounting become standard practice in agent-assisted releases.