We have proof automation now

Adam Langley explores using LLMs to automate proof generation in Lean, a dependently-typed programming language, by building a Zstandard decompressor. The post explains Zstandard's FSE entropy encoder in detail, then demonstrates how Lean's dependent types can encode and enforce subtle invariants — like array bounds safety — that would otherwise be mere comments in conventional languages. The key insight is that LLMs can now automatically discharge complex proof obligations in ~20 minutes for a fraction of a $20/month subscription, potentially making dependent-type systems practical for everyday software engineering. The post also covers Lean's practical features (strictness, monadic do-notation, in-place mutation optimization) and briefly explores verified assembly via AWS's LNSym project.

Source: https://www.imperialviolet.org/2026/07/26/zstd-lean.html. 8sync News only summarizes and links out; content copyright belongs to the authors and original sources.