Anthropic PBC used its Claude model to create a computer-verifiable version of the proof for Fermat's Last Theorem. ^[1] Anthropic announced that one of its internal models, using the prove2.me platform, formalized a complete proof of Fermat's Last Theorem in Lean, completing Freek Wiedijk's list of 100 formalization challenges. ^[2] Anthropic's researchers completed the task of formalizing Andrew Wiles' 1995 proof in 11 days using an internal research model. ^[3] The formalized proof was written in the programming language Lean and comprises 13 million lines of code, making it the largest-ever file of its kind. ^[4] The codebase for the formalization is over 13.4 million lines of code and takes nearly 20 times as long to compile as Lean's mathematics library, according to the article's author who compiled it. ^[5] The formalized proof follows the Darmon-Diamond-Taylor 1995 exposition of the Wiles-Taylor-Wiles argument, using the Langlands-Tunnell theorem and Ribet's level-lowering theorem. ^[6] Kevin Buzzard, a mathematician whose work Claude used to generate the formalized proof, stated that AI autoformalization artifacts are now robust enough to be built upon. ^[7] The article's author, funded by the EPSRC to formalize a proof of Fermat's Last Theorem, said the Anthropic work does not make his project redundant because he also promised to make pull requests to Lean's mathematics library and create a dynamic document for humans to explore the modern proof. ^[8]