Anthropic: Claude agents produce the first complete computer-verified formalization of Fermat's Last Theorem

Anthropic reports the first complete, computer-checked proof of Fermat's Last Theorem formalized in Lean, produced largely autonomously by dozens of Claude agents over 11 days (13M lines of Lean, ~29,500 intermediate theorems, ~6B output tokens from an internal model comparable to Claude Fable 5.1). The proof uses only Lean's three standard axioms, was reviewed by Kevin Buzzard, and is published on GitHub via the open Prove2Me formalization platform.