Mathematician Levent Alpoge reportedly found a counterexample to most versions of the Jacobian conjecture, a puzzle first proposed in two dimensions in 1884, with the all-dimension version posed in 1939. He credited an AI model called Claude Fable 5 as his tool. Alpoge shared his result on X (formerly Twitter), posting, "Hello there the Jacobian conjecture is false," along with his counterexample.