Building a better Bugbot

4 months ago

Bugbot is a code review agent designed to analyze pull requests for logic bugs, performance issues, and security vulnerabilities before they reach production.
The development of Bugbot started with qualitative assessments and evolved into a systematic approach using a custom AI-driven metric to improve quality.
Bugbot's resolution rate increased from 52% to over 70%, and the average number of bugs flagged per run rose from 0.4 to 0.7.
Early improvements included running multiple bug-finding passes in parallel and using majority voting to filter out false positives.
Bugbot's production readiness involved foundational systems like a rebuilt Git integration in Rust, rate-limit monitoring, and proxy-based infrastructure.
The resolution rate metric was introduced to quantitatively assess Bugbot's performance by determining which bugs were actually resolved by the author.
Switching to a fully agentic design led to significant gains, allowing Bugbot to reason over diffs and call tools dynamically.
Bugbot now reviews over two million PRs monthly for customers and is used internally at Cursor.
Future enhancements include Bugbot Autofix, running code to verify bug reports, and continuous codebase scanning.
Key contributors to Bugbot's development include Lee Danilek, Vincent Marti, and others.

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