Devstral is an agentic LLM for software engineering tasks built under a collaboration between Mistral AI and All Hands AI 🙌. Devstral excels at using tools to explore codebases, editing multiple files and power software engineering agents. The model achieves remarkable performance on SWE-bench which positions it as the #1 open source model on the benchmark results below.

mistralai/devstral-small-2507 is the newest version of this model.

It is finetuned from Mistral-Small-3.1, therefore it has a long context window of up to 128k tokens. As a coding agent, Devstral is text-only and before fine-tuning from Mistral-Small-3.1 the vision encoder was removed.

Updates compared to Devstral Small 1.0:

• Improved performance, please refer to the benchmark results.
• Devstral Small 1.1 is still great when paired with OpenHands. This new version also generalizes better to other prompts and coding environments.
• Supports function calling and tool use

Benchmark Results - SWE-Bench

Devstral Small 1.1 achieves a score of 53.6% on SWE-Bench Verified, outperforming Devstral Small 1.0 by +6,8% and the second best state of the art model by +11.4%.

Model	Agentic Scaffold	SWE-Bench Verified (%)
Devstral Small 1.1	OpenHands Scaffold	53.6
Devstral Small 1.0	OpenHands Scaffold	46.8
GPT-4.1-mini	OpenAI Scaffold	23.6
Claude 3.5 Haiku	Anthropic Scaffold	40.6
SWE-smith-LM 32B	SWE-agent Scaffold	40.2
Skywork SWE	OpenHands Scaffold	38.0
DeepSWE	R2E-Gym Scaffold	42.2

When evaluated under the same test scaffold (OpenHands, provided by All Hands AI 🙌), Devstral exceeds far larger models such as Deepseek-V3-0324 and Qwen3 232B-A22B.

License

Devstral is available under the Apache-2.0 license.