# Claude's Fable 5 just solved an 87-year-old math problem, and it matters for bitcoin

_Wednesday, July 22, 2026 at 8:00 AM EDT · AI · Latest · Tier 2 — Notable_

![Claude's Fable 5 just solved an 87-year-old math problem, and it matters for bitcoin — Primary](https://cdn.sanity.io/images/s3y3vcno/production/401bfec40039dbd71d0f355d9682b235969fc70b-6808x4539.jpg?auto=format&w=960&h=540&crop=focalpoint&fit=clip&q=75&fm=jpg)

An Anthropic AI model, Claude Fable 5, helped disprove the 87-year-old Jacobian conjecture, a famous open problem in mathematics dating to 1939.

Levent Alpöge, a number theorist who works at Anthropic and previously held a fellowship at Harvard, posted the result on X on Sunday night, crediting the company's Claude Fable 5 model. The model produced a concrete counterexample that mathematicians could verify by hand within a day, showing that a certain kind of mathematical "machine" can pass standard checks yet still not be reversible.

The breakthrough underscores how rapidly advancing AI capabilities are drawing speculative capital and attention away from crypto and toward computing power, chips and model builders.

## Sources

- [CoinDesk](https://www.coindesk.com/tech/2026/07/21/claude-s-fable-5-just-solved-an-87-year-old-math-problem-and-it-matters-for-bitcoin)

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Retrieved: 2026-07-22T08:01:01.145Z
Publisher: Tech & Business (techandbusiness.org)