7Mistral AI News·
Mistral releases Leanstral 1.5, a state-of-the-art open-source formal verification model
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.
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Mistral Releases Leanstral: First Open-Source Code Agent for Lean 4 Formal Verification
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.
Mistral AI Releases Devstral: Apache 2.0 Agentic Coding Model with SWE-Bench SOTA
Mistral AI, in collaboration with All Hands AI, releases Devstral, an agentic LLM specialized for software engineering tasks under the Apache 2.0 license. The model achieves 46.8% on SWE-Bench Verified, surpassing prior open-source state-of-the-art by over 6 percentage points and outperforming larger models like DeepSeek-V3-0324 (671B) and Qwen3 232B-A22B under the same OpenHands scaffold. Devstral is small enough to run on a single RTX 4090 or a Mac with 32GB RAM, and is available via Mistral's API at $0.1/M input tokens, as well as on HuggingFace, Ollama, and other platforms. Mistral indicates a larger agentic coding model is in development.
Mistral Small 4: Unified Multimodal, Reasoning, and Coding MoE Model Released Under Apache 2.0
Mistral AI has released Mistral Small 4, a 119B-parameter Mixture-of-Experts model (6B active per token) that unifies capabilities previously split across Magistral (reasoning), Pixtral (multimodal), and Devstral (coding agents) into a single open-weights model. The model features a 256k context window, configurable reasoning effort via a `reasoning_effort` parameter, native text and image input support, and is released under Apache 2.0. Mistral claims 40% latency reduction and 3x throughput improvement over Mistral Small 3, with benchmark results showing competitive performance against GPT-OSS 120B and Qwen models while producing significantly shorter outputs. The release includes day-0 availability as an NVIDIA NIM and support across vLLM, llama.cpp, SGLang, and Transformers.
Mistral Small 3: 24B Latency-Optimized Open-Weight Model Released Under Apache 2.0
Mistral AI has released Mistral Small 3, a 24B-parameter instruction-tuned model optimized for low latency, achieving over 81% on MMLU at 150 tokens/s on a single GPU. The model is competitive with Llama 3.3 70B and Qwen 32B while being more than 3x faster on equivalent hardware, and is released under Apache 2.0 for both pretrained and instruction-tuned checkpoints. It is explicitly not trained with RL or synthetic data, positioning it as a base model for community fine-tuning and reasoning capability development. Deployment targets include local inference on consumer hardware (RTX 4090, MacBook 32GB RAM), agentic function calling, and domain-specific fine-tuning.
Mistral AI Founding Manifesto and Mistral 7B Release
Mistral AI published its founding mission statement alongside the release of Mistral 7B, a 7-billion-parameter open-weights language model released under Apache 2.0. The model claims to outperform all available open models up to 13B parameters on standard English and code benchmarks, produced in three months from a standing start. The post articulates Mistral's strategic thesis: open-weight models will outcompete proprietary black-box APIs for most enterprise use cases, drawing analogies to Linux, WebKit, and Kubernetes. The company signals intent to release progressively larger frontier models while building a commercial offering around on-premise and VPC deployment.
Mistral AI Releases Mathstral 7B: Math-Specialized Model with SOTA Reasoning in Size Category
Mistral AI has released Mathstral 7B, a math and STEM-specialized model built on Mistral 7B, developed in collaboration with Project Numina. The model achieves 56.6% on MATH and 63.47% on MMLU in standard evaluation, improving to 74.59% on MATH with a reward model over 64 candidates using inference-time compute scaling. Weights are open on HuggingFace and compatible with mistral-inference and mistral-finetune tooling.
Mistral Medium 3: Frontier-Class Performance at 8x Lower Cost
Mistral AI has released Mistral Medium 3, a new enterprise-focused language model priced at $0.4/$2 per million input/output tokens. The model claims to achieve 90%+ of Claude Sonnet 3.7's benchmark performance while undercutting cost leaders like DeepSeek v3, and outperforming open models including Llama 4 Maverick. It supports hybrid, on-premises, and in-VPC deployment on as few as four GPUs, and is available immediately on Mistral La Plateforme and Amazon SageMaker, with additional cloud platforms coming soon. The announcement also teases an upcoming large open-weights model release.
Mistral AI Releases Mixtral 8x22B Under Apache 2.0
Mistral AI has released Mixtral 8x22B, a sparse Mixture-of-Experts model with 141B total parameters but only 39B active parameters, under the permissive Apache 2.0 license. The model features a 64K token context window, native function calling, multilingual support across five European languages, and strong math and coding performance. Mistral claims it outperforms all other open-weight models on standard benchmarks while being faster than dense 70B models due to sparse activation. An instructed version achieves 90.8% on GSM8K maj@8.