Anthropic reports Claude produced a computer-checked proof of Fermat’s Last Theorem

Anthropic reports Claude produced a computer-checked proof of Fermat’s Last Theorem

Anthropic’s article published September 4, 2026, reports that Claude produced a computer-checked proof of Fermat’s Last Theorem using Lean, a proof assistant that checks mathematical reasoning. Anthropic says the work followed a simplified version of Andrew Wiles’s proof and used Prove2Me, a platform for coordinating agents’ formalization work. Anthropic says the project took 11 days and produced 13 million lines of Lean code. Kevin Buzzard, whose team had worked on formalizing the theorem, described the result as an autoformalization achievement. Anthropic presents formalization—encoding proofs so software can check them—as a way to help reviewers assess mathematical work, while saying it should not replace an explanation written for people. The article argues that this approach could reduce the burden of checking future mathematical results. Whether it can do so broadly, and how much human review such proofs will still require, remain open questions.

Publication: 8bfd2c63-dd26-d2ab-c2f9-334719a262e7

attribution — pass: The reading attributes the proof claims, the 11-day timeline, Prove2Me's role and the outlook on formalization to Anthropic. Buzzard's quoted characterization is correctly attributed to him. The source describes Buzzard as having kicked off the community formalization effort, which reasonably supports 'whose team had worked on formalizing the theorem.'

a multi-year community effort kicked off in 2024 by Kevin Buzzard at Imperial College London to complete the formalization using the Lean proof assistant

summary — pass: The summary leads with the actor (Anthropic and Claude) and the development. It explains Lean and formalization in plain language and notes the role of Prove2Me. It conveys the argued significance, reducing the review burden, along with the caveat that formal proofs should not replace human exposition. The question is a genuine open issue that follows from the source. Fermat's Last Theorem is not restated, but it is widely known and its absence does not block understanding.

Proof assistants like Lean verify the logic of a proof algorithmically, demonstrating its correctness beyond a doubt.

date — pass: evidence.originalPublished is the instant 2026-09-04, and the reading states September 4, 2026, which matches the UTC day. Nothing is presented as happening after that date; the dated passage in the source, the Aug-18 thinking excerpt, comes earlier. The page was edited on 2026-10-14, but the claims rely on core body text that is plainly part of the article, and the limitations disclose the edit. The source is a publisher page, so no archive disclosure is required. Forecasts are framed as Anthropic's arguments.

The FLT root reads PROVED on prove2me at 02:00:57Z Aug-18 (10:00:57pm ET Aug-17).

support — pass: Each claim matches the source text. The source supports the 11-day, largely autonomous end-to-end proof, the 13 million lines of Lean, and Prove2Me's coordination and reuse functions (the DAG and natural-language descriptions). It also supports the argument about reducing the review burden and the caveat about human exposition. The implied benefits are kept as Anthropic's argument, and the open questions are labeled as unknown.

Enabling search and reuse by maintaining a natural-language description of each theorem statement, resulting in a simpler proof path.

media — pass: No media candidates were supplied, and the reading selects none, which is appropriate.