Devstral Small

Devstral Small is an open-weights agentic language model purpose-built for software engineering work, developed jointly by Mistral AI and All Hands AI. It is fine-tuned from Mistral-Small-3.1, with the vision encoder removed before fine-tuning so that the resulting model operates purely on text. This lineage keeps the model focused on code reasoning, tool use, and multi-file editing rather than multimodal perception, and it preserves a long context window inherited from its base, which makes it well suited to navigating and modifying large codebases in a single pass.

At a compact scale of around 24 billion parameters, Devstral Small is light enough to run locally or on modest hardware, while still delivering strong results on the SWE-bench software engineering benchmark, where it is positioned as the leading open-source model. The release improves on the earlier Devstral Small 1.0 with better generalization across prompts and coding environments, and it works naturally with OpenHands and Mistral's function-calling format. Practically, this makes it a good fit for developers who want a self-hosted coding agent that can explore repositories, chain tool calls, and act as the reasoning core of an automated software engineering workflow.