Dev uses Opus 5.5 with Lean to formally verify Claude Agent SDK, shipping 16 bug-fix PRs
jimmykoppel · x · 2026-09-23
bcherny used Opus 5.5 with Lean to formally verify the Claude Agent SDK: a few short prompts yielded 16 PRs fixing bugs and race conditions. He also combines Lean and TLA+ to probe data flow, concurrency and state management, noting Claude excels at both even for non-experts.
Mike Knoop adds that while formal verification is becoming practical for security, it doesn't automatically build human understanding—which he sees as the bigger alignment problem.
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