Mistral Medium 3.5 is a flagship 128B dense model that merges instruction-following, reasoning, and coding into a single set of weights. It has a 256K context window, configurable reasoning effort, multimodal input, strong agentic capabilities, and is built for long-horizon tasks that require reliable multi-tool use and structured outputs. The model powers remote agents in Mistral Vibe, allowing coding sessions to run in the cloud, work through long tasks independently, and execute multiple sessions in parallel. Agents can be launched from the Vibe CLI or Le Chat, with local CLI sessions moved to the cloud while preserving history, task state, and approvals. Users can inspect file diffs, tool calls, progress states, and questions as work proceeds. Each coding session runs in an isolated sandbox and can handle module refactors, test generation, dependency upgrades, CI investigations, and bug fixes, then open a GitHub pull request for review.