flteval-c8576f1b·2 events·first seen Aliases: FLTEval
Mistral AI released Leanstral 1.5, an Apache-2.0 licensed mixture-of-experts model with 119B total and 6B active parameters, specialized for formal verification in Lean 4. The model saturates miniF2F (100%), solves 587/672 PutnamBench problems, and achieves new state-of-the-art results on FATE-H (87%) and FATE-X (34%), while costing roughly $4 per problem versus ~$300 for comparable systems. Trained via mid-training, supervised fine-tuning, and reinforcement learning with CISPO, it demonstrates strong test-time scaling and practical code verification capabilities, uncovering 5 previously unknown bugs across 57 open-source repositories.
Mistral AI has released Leanstral, an open-source code agent built on a sparse 120B/6B-active-parameter architecture, designed specifically for formal proof engineering in Lean 4. The model targets realistic proof engineering workflows rather than isolated math competition problems, and is benchmarked on FLTEval, a new evaluation suite tied to the Fermat's Last Theorem formalization project. Leanstral is released under Apache 2.0 with a free API endpoint and MCP support, and demonstrates competitive performance against Claude Sonnet 4.6 at roughly 1/15th the cost. The release positions formal verification as a scalable alternative to human code review for high-stakes software and mathematics.