Hi HN - author here.

Problem I kept hitting: ask the agent for a 15-line fix, get a 500-line renovation that still compiles and passes tests.

Boffin is a small control layer for AI coding agents. Before an edit, it feeds the agent only the architectural constraints for the file it is about to touch, then makes it verify the result. Not another static AGENTS.md for the whole repo.

On DuckDB, a guided refactor landed at +17 / -17 lines with 2,104 assertions passing. Same shape of cases also on FastAPI and LangChain (in the repo examples/).

Try it: npx boffinit cursor

Also works with Claude Code, Codex, and OpenCode.

Happy to answer questions — especially if you have a place where the agent keeps "improving" load-bearing code.

To be blunt the degree to which I take these projects seriously is basically the same as how extensive their eval suite is. A single guided refactor is better than nothing, but one success could just be a fluke. I want to see hundreds, if not thousands, of evals to convince me you’re a project worth looking into.

The AI generated text is also not doing you any favors.

So your headliner case is that it managed to edit 17 lines in DuckDB? Why is the line count relevant here? What is the 17-line change even about?