Mistral AI Releases Leanstral 1.5: An Apache-2.0 Lean 4 Code Agent Model Solving 587 of 672 PutnamBench Problems

Mistral AI has released Leanstral 1.5, an open-source model specialized in writing code for the Lean 4 mathematical proof assistant. By successfully solving 587 of 672 problems from the PutnamBench dataset, the 119B parameter mixture-of-experts model demonstrates significant progress in automated formal verification and theorem proving.