Levent Alpoge (Anthropic researcher; formerly Harvard Society of Fellows Junior Fellow) posted on X a C³→C³ polynomial map counterexample to the Jacobian conjecture, thanking “fable” (Claude Fable 5). Jacobian determinant constant -2; three distinct inputs map to same output (-1/4,0,0). Verifiable by hand/Wolfram Alpha.
Keller 1939; on Smale’s 21st-century problems list. Two-variable case may remain open. Alpoge Anthropic affiliation disclosed. Peer-reviewed paper not yet published. Context: AI-assisted math discovery wave; Fable 5 export-control history.