Leanstral

Mistral Large 4

Mistral AI

Mistral Large 4, also called Le Chonk, is Mistral’s trillion-parameter multimodal flagship, first offered as a public API preview on October 6, 2026. It targets software engineering, long-running agents, visual grounding, and specialist enterprise work including finance, law, and cybersecurity. Training took place on Mistral’s European infrastructure. Its planned weight release is later in October; the preview available at the audit date does not include downloadable weights. Architecture and post-training details beyond the mixture-of-experts configuration remain limited.

MAI-Thinking-1

Microsoft

MAI-Thinking-1 is Microsoft AI’s medium-inference-footprint reasoning model, first announced at Build in June and made available in public preview on Microsoft Foundry on August 12, 2026. It uses a sparse mixture-of-experts architecture and was trained in-house without third-party model distillation. The model targets mathematical reasoning, software engineering, and complex enterprise questions. Clean-data and benchmark statements are provider claims rather than guarantees of domain correctness. June announcement-only exposure is not used as its public release date.

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.