Leanstral 1.5
API ID labs-leanstral-1-5
Leanstral 1.5 was a preview Mistral model. It had a 256,000-token context window and up to 128,000 output tokens. It took image input and supported function calling and structured outputs.
An updated Lean 4 formal proof engineering model optimised for automated theorem proving and autoformalization. 119B total parameters, 6.5B active.
- Status
- Retired
- Released
- —
- Shutdown
- Sep 30, 2026
- Replacement
- —
labs-leanstral-1-5 stopped serving on September 30, 2026.
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 |
| Max output tokensThe longest reply the model can write in one response, in tokens. A token is about three-quarters of an English word. | 128,000 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.
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