❯ Anthropic says Claude wrote the first complete machine-checked proof of Fermat’s Last Theorem in 11 days: 13 million lines of Lean

the proofAccording to Anthropic’s research note, Claude produced the first end-to-end computer-checked proof of Fermat’s Last Theorem in 11 days, working largely autonomously, in Lean 4 — 13 million lines of code in total, proving 29,500 intermediate theorems along the way. The company calls it the largest Lean proof ever written; the code is public on GitHub.

historyAndrew Wiles’s human proof in 1995 came more than 350 years after the conjecture, and in the three decades since no one had fully formalized it — formalizing a major theorem by hand is measured in years. Per Anthropic’s write-up, the proof spans several areas of mathematics never previously formalized, and a substantial share of those 29,500 intermediate theorems are new formalization results in their own right.

verification costWhat actually changes is the cost of verifying mathematical proofs. Checking a major proof can take years; formalization hands that to a machine, but the bottleneck has been the labor of translating human reasoning into Lean. Compressing that step from years to 11 days turns formal verification from expert handcraft into a process that can be run at scale.

the fieldThe question to watch is whether top journals make formal verification a default requirement — once the bar drops to two weeks, “not machine-verified” turns from normal into a defect. The people feeling it first are formal mathematics research teams, whose core skill just got substantially automated.

▪ SIGNALA formalization nobody finished in thirty years took a machine 11 days — mathematical proof has a new floor for acceptance.