Anthropic's large language model, Claude Fable 5, discovered a definitive counterexample to the "Jacobian Conjecture" in three-dimensional space, overturning the 87-year-old algebraic geometry problem. Anthropic employee and mathematician Levent Alpöge shared the finding on social media on July 19, 2026, without a formal paper.
Frontier AI models are now capable of disproving long-standing mathematical conjectures, demonstrating a new class of reasoning capability.