Fermat's Last Theorem: complete Lean proof written by Claude
Status
Formally verified
Recorded on · anthropic.com
- Announced
- Recordedformally verified
What this status means
Source reading : Source read word for word (level 3 of 3)
A named third party has checked a machine proof. Lean supplied by the claimant alone is not enough.
The gist
Anthropic announced on 4 September 2026 a Lean proof of Fermat's Last Theorem, written by Claude and checked by the Lean kernel. Status: formally verified. It is a machine check of existing mathematics, not a new result.
Cite this entry
A single status snapshot since Oct 11, 2026: a citation always points to a dated snapshot.
Cite snapshot 1, Oct 11, 2026
APA citation with the dated link
BibTeX @misc, key discoveria-claude-flt-formalization-2026-09-04-r1
@misc{discoveria-claude-flt-formalization-2026-09-04-r1,
author = {{DiscoverIA}},
title = {Fermat's Last Theorem: complete Lean proof written by Claude},
howpublished = {DiscoverIA registry, entry claude-flt-formalization-2026-09-04},
note = {Status « Formally verified », snapshot 1, recorded on October 11, 2026. formalisation of a known result},
year = {2026},
url = {https://discoveria.ai/en/fiche/claude-flt-formalization-2026-09-04/#releve-1},
urldate = {2026-10-11}
}Dated link opens this snapshot in the history
Text written by an AI (DiscoverIA pipeline), on Reviewed by: nobody yetReport an error
What has not been reviewed?
The status and its sources come from the registry; only the explanatory text has not been reviewed. A reported error is corrected, then the text is reviewed.
The status and its sources come from the registry; only the explanatory text has not been reviewed. A reported error is corrected, then the text is reviewed.
Key facts
- Claimed by
- Anthropic
announced on Sep 4, 2026 - Nature
- formalisation of a known result
- Field
- Mathematics (formalisation / number theory)
- Checked by
- Lean; comparator; Kevin Buzzard quoted by the Anthropic page (not re-checked elsewhere)
- Sources (domains)
- 1 : 1 links only
- This entry
- AI draft, not reviewed
To understand
Analogy
It is like having a very long contract read by software that checks every clause: the contract itself does not change, but every line is verified.
What it changes
This proof establishes nothing new: it is a machine check of existing mathematics. According to Anthropic, Claude wrote it in 11 days, amounting to 13 M lines of Lean code, a language in which a computer checks every step of a proof.
What remains unclear
Kevin Buzzard's review is cited only by Anthropic's page and has not been rechecked elsewhere. Anthropic calls it the first complete computer-checked proof: that is its own claim. The fidelity of the formalised statement is not assessed here.
1 source.
For experts
Sources(domains)
- primaireanthropic.comlink only, reading not recorded
Method
Status “formally verified” recorded on 11 October 2026 from anthropic.com (page read, quotation checked word for word). Checked by a named third party: Kevin Buzzard.
Limits
Nature: formalisation, that is a machine check of an already known result, not a discovery.
It is like having a very long contract read by software that checks every clause: the contract itself does not change, but every line is verified.
Status history
Only one observation so far.
- 01
First observation:Formally verifiedCurrent status
verification of existing mathematics, not a new result; covered by Nature (linked article title)
Source: anthropic.comread word for word
An observation is added; none is ever erased.
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