Claude formalizes Fermat's Last Theorem: 13M lines of Lean in 11 days
Dozens of agents coordinated via the open Prove2Me platform; the full proof is a public repo — plus a Spotify plugin that cuts Claude Code tokens 90%.
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13M lines, 30,300 theorems, 11 days
Anthropic set dozens of Claude agents loose on the full Lean formalization of Fermat's Last Theorem: roughly 30,000 intermediate theorems proved (29,500 in the final proof), 13 million lines of code, and about 6 billion output tokens — done in 11 days, largely autonomously. The driving model was a research build "roughly comparable to Claude Fable 5.1."
The builder lesson: agents need a shared to-do list
Solo agents made progress but "lost track of the larger project and stopped coordinating." The fix was Prove2Me — an open coordination platform (Anthropic's Tianyi Peng plus Columbia) that tracks proof interdependencies and lets agents reuse finished results — wired to a Claude Code multi-agent workflow. That orchestration pattern, not the math, is the transferable part.
The proof is public — go read it
The complete proof and a written walkthrough are open on GitHub at anthropics/fermats-last-theorem. Lean verified it using only its three standard axioms, and the codebase runs over 5x the size of Mathlib, the main community library. Imperial's Kevin Buzzard called it "an extraordinary autoformalization achievement."
Elsewhere: a plugin that cuts Claude Code tokens 90%
Spotify's open "shunt" plugin uses Claude Code's PreToolUse hooks to intercept big file reads (over 350 lines) and route them to cheaper worker models, keeping I/O off the frontier model's context — about 90% fewer tokens on bulk reads in a Java monorepo. The hook-routing pattern is replicable even without Spotify's Portal.