Mistral's new flagship, Mistral Medium 3.5, merges what used to be separate models for chat, reasoning, and code into a single product. The French company is also adding asynchronous cloud agents to its coding tool Vibe and giving Le Chat a new agent mode.
Per the model card, Mistral Medium 3.5 is a dense model with 128 billion parameters and a 256,000-token context window. "Dense" means all 128 billion parameters get loaded and activated for every token generated. That makes inference expensive, but it's also simpler to run and tends to hold up better in production.
Mistral knows there are cheaper approaches. Mistral Large 3 uses a Mixture of Experts (MoE) setup with 675 billion total parameters but only activates 41 billion per token. Mistral Small 4 has 119 billion parameters and activates just 6 billion. Competitors like Deepseek and Qwen have been moving their top models toward MoE for a while, since it delivers cheaper inference at similar quality.
Against that backdrop, building the new flagship as a pure dense model is a conservative call: less optimized for inference cost, but easier to ship as one unified model for chat, reasoning, code, and agents.
Mistral says the model can be self-hosted on four GPUs. In practice, that's likely still out of reach for most users outside well-equipped data centers.
