Leanstral 1.5
Leanstral 1.5 (119B, 6B active) saturates miniF2F at 100% and solves 587 of 672 PutnamBench problems under Apache 2.0.
Large leap over Leanstral 1: 100% on miniF2F validation and test, 587/672 PutnamBench at a 4M-token budget, 87% on FATE-H and 34% on FATE-X. Mistral also reports it found 5 previously unknown bugs across 57 open-source repos.
- Date
- Thursday, 2 July 2026
- Lab
- Mistral AI
- Kind
- open-weights
- Access
- open weights
Figures
| Measure | Value | Measured by |
|---|---|---|
| PutnamBench | 587 / 672 solved 4M token budget | company |
| miniF2F | 100% validation and test | company |
Mistral's changelog lists 2026-06-30 (public preview); the blog post is 2026-07-02.
Sources
This record was checked against its sources on 6 October 2026. How we check