Anthropic researcher Levent Alpöge credited the company’s AI model, Claude Fable 5, with helping him find a counterexample to the 87-year-old Jacobian conjecture, announcing on X: "Hello there the Jacobian conjecture is false." The discovery, if confirmed by the wider mathematics community, overturns most versions of the conjecture and highlights AI’s growing role in new mathematical discoveries. The counterexample is reportedly simple enough to fit into a single social media post, making it easier for mathematicians to verify. The Jacobian conjecture was first proposed in two dimensions in 1884 by Czech mathematician Ludwig Kraus and later extended to all dimensions by German mathematician Ott-Heinrich Keller in 1939. The conjecture suggests that if a polynomial function has a constant, non-zero Jacobian determinant, then it should always have another polynomial function that reverses it. According to the reported discovery, the counterexample works in three dimensions and has a constant Jacobian determinant of -2. However, the function maps multiple input points to the same output point, meaning it cannot be reversed. The finding suggests the Jacobian conjecture is false for dimensions higher than two, while the original two-dimensional version remains unsolved.