Devstral Small (July 2025), specifically version 1.1, is an open-weight language model optimized for agentic software engineering tasks. Developed by Mistral AI in collaboration with All Hands AI, the model is fine-tuned from Mistral Small 3.1 and released under the Apache 2.0 license. It is designed to power coding agents capable of navigating complex repositories, editing multiple files, and executing tool-based workflows autonomously.
The model features a 24-billion parameter architecture and a 128,000-token context window. It utilizes the Tekken tokenizer with a 131,000-token vocabulary, which is optimized for efficiency in code-heavy environments. Compared to the initial May 2025 release, the July update introduced improved generalization across various prompt structures and agentic scaffolds.
On the SWE-bench Verified benchmark, Devstral Small 1.1 achieved a score of 53.6%, representing a significant improvement over the previous iteration. It supports both Mistral-style function calling and XML output formats, facilitating integration into autonomous development frameworks.