Mistral Large 4

Leanstral 1.5

Mistral AI

Leanstral 1.5 is Mistral’s open-weight specialist model for Lean 4 formal mathematics and program verification. The 1.5 update improves proof engineering through mid-training, supervised tuning, and reinforcement learning in theorem-proving and code-agent environments. Its first API release is dated June 30 in the changelog, before the July 2 announcement. It edits proof files, runs tools, and revises proofs after compiler feedback within an agent scaffold. Apache-2.0 weights permit local deployment and adaptation. Published success rates involve explicit inference budgets and multiple attempts; a long agent run is not the same as a single context window.

Mistral Medium 3.5

Mistral AI

Mistral Medium 3.5 is a dense open-weight multimodal model that combines instruction following, coding, and adjustable reasoning in a single checkpoint. It launched in public preview as the default model in Le Chat and Mistral Vibe, supporting long-running software and productivity tasks, parallel tool calls, and structured outputs. A newly trained vision encoder handles variable image dimensions and aspect ratios. The modified MIT license must be checked for commercial restrictions; the published four-GPU deployment is a configuration example rather than a universal memory requirement.

Leanstral

Mistral AI

Leanstral is Mistral’s open-weight specialist model for Lean 4 formal mathematics and program verification. The first Leanstral release focuses on realistic formal repositories and uses Lean compiler feedback as a correctness check. It edits proof files, runs tools, and revises proofs after compiler feedback within an agent scaffold. Apache-2.0 weights permit local deployment and adaptation. Published success rates involve explicit inference budgets and multiple attempts; a long agent run is not the same as a single context window.