Formal Verification Veteran Slams AI Circle: Garbage Semantics In, Garbage Proofs Out

tianyin_xu · x · 2026-09-20

Grigore Rosu, a formal verification expert, observes that his field—dating back to the 1960s—keeps getting "rediscovered" by hotter domains, first blockchain and now AI, each time accompanied by newcomers' ignorance and arrogance.

He skewers a recurring pattern: newcomers claim Lean-based formal verification guarantees correctness, yet can't answer basic questions like "what's your trust base?" or "does your language even have a formal semantics?" His verdict: garbage (formal semantics) in, garbage (formal verification) out—Lean only guarantees code matches the semantics you wrote, not that the semantics is right.

He recommends Runtime Verification's blog for doing FV properly, which covers AI-assisted fuzzing that found a real bug in the WAMR WebAssembly runtime, a Rust-rewrite-and-verify workflow for Linux C code with Lean proofs, and end-to-end Lean 4 machine-checked verification of Android's Binder driver deserializer.

Related event: Formal verification veteran warns Lean proofs don't guarantee code correctness(2 posts)→

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