Dev uses Opus 5.5 with Lean to formally verify Claude Agent SDK, yielding 16 bug-fix PRs
bcherny · x · 2026-09-23
Developer bcherny shared a hands-on workflow: he used Opus 5.5 to formally verify the Claude Agent SDK in Lean, and a couple of short prompts produced 16 PRs fixing bugs and race conditions.
- TLA+ also works well; he often combines Lean and TLA+ to probe data flow, concurrency, and state management issues
- He doesn't know either language well, but Claude is excellent at both—dramatically lowering the barrier to formal verification
- The approach is useful for formally modeling your own code and surfacing bugs a human would likely miss
- He poses the question: is formal verification the future of coding, or at least of bug finding?
Related event: Developer Uses Opus to Formally Verify Agent SDK in Lean(2 posts)→
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