Mistral AI releases open-source Leanstral 1.5

Mistral AI released Leanstral 1.5, an open-source Apache 2.0 model for Lean 4 formal verification. It scores 100% on miniF2F, solves 587 of 672 PutnamBench problems, and set state-of-the-art results on FATE-H and FATE-X algebra benchmarks. In a code scan of 57 repositories, it caught five previously unknown bugs, including an overflow in the Rust library varinteger.