en.Wedoany.com Reported - Simon Willison, a Django co-developer and creator of Datasette, has released version 4.0rc2 of the popular SQLite tool library sqlite-utils, the second release candidate of this tool. The majority of code modifications in this release were completed by the AI model Claude Fable 5. Willison recently disclosed in detail the entire process of this AI-assisted development and calculated the associated costs.
The entire testing task began with a prompt sent via Claude Code on an iPhone. Willison asked the model to conduct a final review before the stable release of version 4.0, identifying all issues that would constitute breaking changes. The entire process involved 37 prompts and 34 commits, with the model modifying 30 files, adding 1,321 lines of code, and deleting 190 lines. While the Fable model took 10 to 15 minutes to process each task, Willison took time off to attend the July 4th parade in Half Moon Bay, occasionally checking progress via his phone.
During this AI-driven review, the model identified five critical defects classified as release blockers. The most severe issue was that the delete_where() method did not commit transactions, causing database connections to remain open and all subsequent write operations to silently roll back upon closure. Willison admitted he had never discovered this vulnerability before and was relieved it was not released in a stable version, as it would have led to user data loss.
The final review was delegated to another company's AI model—GPT-5.5 running via Codex. This model found two additional P1-level issues in the new code, which Fable subsequently confirmed and fixed through experiments in a new session. Willison noted that this cross-model review practice has consistently identified real problems and has thus become part of his daily workflow.
Using the AgentsView tool within the same environment, Willison calculated the session costs: the main Fable 5 session cost $141, plus a few dollars for sub-agents, totaling $149.25, based on API rates. Willison has upgraded his Max subscription plan from $100 per month to $200 per month and is purposefully consuming the quota. He mentioned that starting July 7, Fable 5 will no longer be included in the subscription quota, and the model will then require separate payment in credits based on API costs.
