Leanstral
API ID labs-leanstral-2603
Leanstral was a preview Mistral model, released March 2026. It had a 256,000-token context window. It took image input and supported function calling and structured outputs.
Our first open-source code agent designed for Lean 4, built for formal proof engineering in realistic repositories. 119B parameters with 6.5B active.
- Status
- Retired
- Released
- March 2026
- Shutdown
- Jun 30, 2026
- Replacement
- Leanstral 1.5labs-leanstral-1-5
labs-leanstral-2603 stopped serving on June 30, 2026. Recommended replacement: labs-leanstral-1-5.
How to migrate to Leanstral 1.5
Features
Compare models| Feature | Value | Since | Source |
|---|---|---|---|
| Structured outputsThe model can be held to a JSON schema you supply, so every reply parses without retries or cleanup. | Supported | in place when tracking began (October 6, 2026) | source |
| Function callingAlso called tool use. You describe functions; the model replies with a function name and arguments for your code to run, then uses the result. | Supported | in place when tracking began (October 6, 2026) | source |
| Image inputImages such as screenshots, photos and charts can go in the prompt for the model to read. | Supported | in place when tracking began (October 6, 2026) | source |
| Context windowThe most the model can work with in one request, in tokens: your prompt, conversation history and files. A token is about three-quarters of an English word. | 256,000 tokens | in place when tracking began (October 6, 2026) | source |
Not published by Mistral: Prompt caching, Batch API, PDF input, Reasoning / thinking, Fine-tuning, Built-in web search, temperature parameter, top_p parameter, logprobs, Max output tokens.
Price history
USD per 1M tokens, standard tierWe started recording this model's prices on Oct 5, 2026. The history grows with each daily check.
Show as a table
| From | Type | Price |
|---|---|---|
| Oct 5, 2026 | Input | $0.00 |
| Oct 5, 2026 | Output | $0.00 |
Prices
USD per 1M tokens, every type and band, by tier| Type | Price $/1M | In effect |
|---|---|---|
| Standard | ||
| input | $0.00 | |
| output | $0.00 | |
Changelog
Changes we detected on Mistral's pagesNo changes recorded yet.
Last checked · Sources: Mistral models