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 this benchmark.
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.
For enterprises requiring specialized capabilities (increased context, domain-specific knowledge, etc.), we will release commercial models beyond what Mistral AI contributes to the community.
Agentic coding: Devstral is designed to excel at agentic coding tasks, making it a great choice for software engineering agents.
lightweight: with its compact size of just 24 billion parameters, Devstral is light enough to run on a single RTX 4090 or a Mac with 32GB RAM, making it an appropriate model for local deployment and on-device use.
Apache 2.0 License: Open license allowing usage and modification for both commercial and non-commercial purposes.
Context Window: A 128k context window.
Tokenizer: Utilizes a Tekken tokenizer with a 131k vocabulary size.
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.
In a bash terminal, run lms import Devstral-Small-2507-Q4_K_M.gguf in the directory where you've downloaded the model checkpoint (e.g. Devstral-Small-2507_gguf)
Open the LM Studio application, click the terminal icon to get into the developer tab. Click select a model to load and select Devstral Small 2507. Toggle the status button to start the model, in setting toggle Serve on Local Network to be on.
On the right tab, you will see an API identifier which should be devstral-small-2507 and an api address under API Usage. Keep note of this address, this is used for OpenHands or Cline.
Make sure you launched an OpenAI-compatible server such as vLLM or Ollama as described above. Then, you can use OpenHands to interact with Devstral Small 1.1.
In the case of the tutorial we spineed up a vLLM server running the command:
When accessing the OpenHands UI, you will be prompted to connect to a server. You can use the advanced mode to connect to the server you launched earlier.
Make sure you launched an OpenAI-compatible server such as vLLM or Ollama as described above. Then, you can use OpenHands to interact with Devstral Small 1.1.
In the case of the tutorial we spineed up a vLLM server running the command:
OpenHands:Understanding Test Coverage of Mistral Common#
We can start the OpenHands scaffold and link it to a repo to analyze test coverage and identify badly covered files. Here we start with our public mistral-common repo.
After the repo is mounted in the workspace, we give the following instruction
Check the test coverage of the repo and then create a visualization of test coverage. Try plotting a few different types of graphs and save them to a png.
The agent will first browse the code base to check test configuration and structure.
First initialize Cline inside VSCode and connect it to the server you launched earlier.
We give the following instruction to builde the video game:
Create a video game that mixes Space Invaders and Pong for the web.
Follow these instructions:
- There are two players one at the top and one at the bottom. The players are controling a bar to bounce a ball.
- The first player plays with the keys "a" and "d", the second with the right and left arrows.
- The invaders are located at the center of the screen. They shoud look like the ones in Space Invaders. Their goal is to shoot on the players randomly. They cannot be destroyed by the ball that pass through them. This means that invaders never die.
- The players goal is to avoid shootings from the space invaders and send the ball to the edge of the over player.
- The ball bounces on the left and right edges.
- Once the ball touch one of the player's edge, the player loses.
- Once a player is touched 3 times or more by a shooting, the player loses.
- The player winning is the last one standing.
- Display on the UI, the number of times a player touched the ball, and the remaining health.