Leanstral 1.5 (retired)
Leanstral 1.5 is a retired experimental Mistral AI Labs model for Lean 4 formal proofs; Mistral set its retirement for September 30, 2026.
- Lab
- Mistral
- Release date
- Status
- Retired
- API model ID
- labs-leanstral-1-5
- Shutdown date
Mistral released Leanstral 1.5 (labs-leanstral-1-5), an experimental Labs model for Lean 4 formal proof engineering, on June 30, 2026, with a planned retirement date of September 30, 2026. Its changelog entry of September 29, 2026 marks the model as deprecated, retiring on September 30, 2026.
- Availability
- Experimental Labs model; retired September 30, 2026.
- Official source
- docs.mistral.ai
- Last checked
Questions
When did Leanstral 1.5 retire?
Mistral set its retirement for September 30, 2026.
What was Leanstral 1.5?
An experimental Mistral Labs model for Lean 4 formal proof engineering, released on June 30, 2026.
Was the retirement planned?
Yes. Mistral announced the September 30, 2026 retirement date when it released the model.
Source
Release dates, model IDs and limits come from each lab’s own announcement, changelog, documentation or deprecations page, linked on every model with the date it was last checked. How we pick and check sources: editorial standards.