Mistral AI · Coding
Leanstral 1.5
Free Labs endpoint for Lean 4 formal proof engineering, autoformalization and automated theorem proving — genuinely $0 while Mistral gathers feedback, but it is a research preview with no availability guarantee, so don't build production on it. (The older labs-leanstral-2603 still shown on the marketing pricing page was retired 30 Jun 2026.)
Open weights · Permissive (Apache, MIT, OpenMDW) · Data checked September 6, 2026 · Not a hands-on evaluation
Model ID labs-leanstral-1-5
- Parameters
- 119B total · 6.5B active119B-A6.5B MoE
- Architecture
- Mixture of experts
- Context window
- 256,000 tokensMaximum input
- Max output
- 128,000 tokensPer response
- Input price
- $0.00 per 1M tokens
- Output price
- $0.00 per 1M tokens
- Cached input
- $0.00 per 1M tokens
- Blended price
- $0.00 per 1M tokens3:1 input to output
- Knowledge cutoff
- Not recorded
- Released
- 2026-06-30
- Status
- preview
- Size band
- 40B to 120B
License and openness
Leanstral 1.5 is released under the Apache-2.0. This is a permissive license. It generally allows use, modification and redistribution, including commercial use, subject to attribution and notice requirements. License terms can change between versions; confirm the text published with the weights you download.
Capabilities
| Input modalities | text, image |
|---|---|
| Output modalities | text |
What it is for
(The older labs-leanstral-2603 still shown on the marketing pricing page was retired 30 Jun 2026.)
At a three-to-one input-to-output ratio, Leanstral 1.5 costs $0.00 per million tokens blended. A workload of one million input and 330,000 output tokens per day would run about $0.00 per month at list price, before caching or batch discounts.
Cost at list price
| Input | $0.00 per 1M tokens |
|---|---|
| Output | $0.00 per 1M tokens |
| Cached input | $0.00 per 1M tokens |
| Blended, 3:1 | $0.00 per 1M tokens |
A recorded $0.00 is preserved from the reference as recorded. It does not promise free access; check the provider’s current terms.
Estimate a workload across all models ↗Sources
- Source: docs.mistral.ai ↗
- Mistral AI pricing ↗
- API docs ↗
- Full reference record for Leanstral 1.5 ↗
- Mistral AI in the reference ↗
Sources checked September 6, 2026. Specifications and prices change without notice; confirm against the provider before you commit.
Other open-weight models from Mistral AI
- Mistral Medium 3.5 · 128B dense
- Mistral Large 3 · 675B total · 41B active
- Mistral Small 4 · 119B total · 6.5B active
- Ministral 3 14B · 14B dense
- Ministral 3 8B · 8B dense
- Ministral 3 3B · 3B dense
- Z.ai GLM 5.2 · Not recorded
- Voxtral Small · 24B dense
- Voxtral Mini Transcribe Realtime · 4B dense
- Voxtral TTS · 4B dense
- Shieldstral 1.0 · 3.8B dense