Anthropic repository reports Lean-checked Fermat proof

An Anthropic GitHub repository reports a complete machine-checked proof of Fermat's Last Theorem in Lean 4. The repository says its default build checks the theorem against Lean's three standard axioms, with no added axioms, sorry declarations or native_decide. It also says the build was checked against a comparator and accepted by nanoda, an independent Lean kernel written in Rust. Anthropic describes the project as a research artifact, not maintained and not accepting contributions, and says its Lean sources were produced by AI agents using human-written open-source Lean.