Sqlite-utils 4.0: Simon Willison Prepped the Release with Claude Fable

Simon Willison, the author of the popular sqlite-utils library, has described how he prepared the stable 4.0 release with the help of the Claude Fable model. He had previously written about the 4.0rc1 release candidate.

According to Willison, his access to Claude Fable under the Max subscription had only a few days left, so he decided to use that time to bring the library to a stable version he could feel fully confident in. Willison follows semantic versioning and tries to ship incompatible major versions as rarely as possible.

The work began with a prompt in Claude Code for the web, sent from an iPhone: a final review before shipping the stable 4.0 release, with an emphasis on finding changes that would turn into breaking changes down the line if they were fixed later.

In response, the model produced a report that surfaced five problems classified as release blockers. One of the most serious turned out to be a bug in the Table.delete_where() method. Unlike the correctly implemented Table.delete(), this method runs its DELETE query through self.db.execute() without an atomic() wrapper. As a result, the connection is left in an in_transaction=True state, which causes all subsequent atomic() calls to take the savepoint branch and likewise fail to commit their changes.

Willison offered an end-to-end example reproducing the problem: after a call to delete_where(), subsequent operations that insert data into tables are not saved, and when the database is reopened, not only the deleted rows are lost but also the data added afterward — including an entire separate table.

According to the author, the cost of bringing Claude Fable in to work on the release came to about $149.25.

Source: Simon Willison