Formally verifying the Claude Agent SDK with Lean via Opus yields 16 bug-fix PRs
jfiance · x · 2026-09-24
Boris Cherny used Opus 5.5 to formally verify the Claude Agent SDK with Lean: a couple of short prompts produced 16 PRs fixing bugs and race conditions. He also pairs Lean with TLA+ to probe data flow, concurrency, and state management, noting Claude excels at both languages despite him not knowing them well. The reposter calls it the clearest case yet that formal verification is now a practical engineering tool, with the loop running on production engines.
Related event: Opus 5.5 with Lean formally verifies Agent SDK(18 posts)→
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