Simon Willison’s Weblog

Devstral. New Apache 2.0 licensed LLM release from Mistral, this time specifically trained for code.

Devstral achieves a score of 46.8% on SWE-Bench Verified, outperforming prior open-source SoTA models by more than 6% points. When evaluated under the same test scaffold (OpenHands, provided by All Hands AI 🙌), Devstral exceeds far larger models such as Deepseek-V3-0324 (671B) and Qwen3 232B-A22B.

I'm always suspicious of small models like this that claim great benchmarks against much larger rivals, but there's a Devstral model that is just 14GB on Ollama to it's quite easy to try out for yourself.

I fetched it like this:

ollama pull devstral

Then ran it in a llm chat session with llm-ollama like this:

llm install llm-ollama
llm chat -m devstral

Initial impressions: I think this one is pretty good! Here's a full transcript where I had it write Python code to fetch a CSV file from a URL and import it into a SQLite database, creating the table with the necessary columns. Honestly I need to retire that challenge, it's been a while since a model failed at it, but it's still interesting to see how it handles follow-up prompts to demand things like asyncio or a different HTTP client library.

It's also available through Mistral's API. llm-mistral 0.13 configures the devstral-small alias for it:

llm install -U llm-mistral
llm keys set mistral
# paste key here
llm -m devstral-small 'HTML+JS for a large text countdown app from 5m'