Leanstral

Leanstral

Mistral AI
Leanstral 1.5

Leanstral 1.5

Mistral AI
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About

Leanstral is an open-source code agent developed by Mistral AI specifically designed to work with the Lean 4 proof assistant. The model focuses on generating code while also formally verifying its correctness against strict mathematical or software specifications. Unlike traditional coding assistants, Leanstral integrates directly with formal proof systems to ensure that generated code satisfies defined logical requirements. Its architecture is optimized for proof engineering tasks and operates efficiently with sparse model parameters. Leanstral is released under the Apache 2.0 license, making it freely accessible for developers, researchers, and organizations to use and customize. The model is designed to operate within real-world formal repositories rather than isolated problem environments. By combining code generation with formal verification, Leanstral aims to reduce the need for manual human review in complex software and mathematical development.

About

Leanstral 1.5 is an Apache-2.0 licensed model for practical proof engineering in Lean 4, built to make formal verification more powerful and accessible. With 119B total parameters and only 6B active parameters, it delivers a major performance upgrade for theorem proving, agentic proof engineering, and real-world code verification. Leanstral 1.5 was trained through a three-stage process: mid-training, supervised fine-tuning, and reinforcement learning with CISPO. In the multiturn environment, the model receives a theorem statement, submits a proof, gets Lean compiler feedback, and refines its approach until the proof compiles or the budget is exhausted. In the code agent environment, Leanstral works like a developer in a raw filesystem: it edits files, runs bash commands, and uses the Lean language server to inspect goals, errors, and type information in real time.

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Audience

AI researchers, software engineers, and developers working with formal verification, proof assistants, and mathematically rigorous software development

Audience

Formal methods engineers and Lean 4 researchers who need an open model for theorem proving, proof debugging, and real-world code verification

Support

Phone Support
24/7 Live Support
Online

Support

Phone Support
24/7 Live Support
Online

API

Offers API

API

Offers API

Screenshots and Videos

Screenshots and Videos

Pricing

Free
Free Version
Free Trial

Pricing

Free
Free Version
Free Trial

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Training

Documentation
Webinars
Live Online
In Person

Training

Documentation
Webinars
Live Online
In Person

Company Information

Mistral AI
Founded: 2023
France
mistral.ai

Company Information

Mistral AI
Founded: 2023
France
mistral.ai/news/leanstral-1-5/

Alternatives

Alternatives

Leanstral

Leanstral

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Claude Opus 4.6

Claude Opus 4.6

Anthropic
DeepSWE

DeepSWE

Agentica Project
Leanstral 1.5

Leanstral 1.5

Mistral AI
SWE-1.5

SWE-1.5

Cognition
Command R+

Command R+

Cohere AI

Categories

Categories

Integrations

Mistral AI
Mistral AI Studio
Mistral Vibe

Integrations

Mistral AI
Mistral AI Studio
Mistral Vibe
Claim Leanstral and update features and information
Claim Leanstral and update features and information
Claim Leanstral 1.5 and update features and information
Claim Leanstral 1.5 and update features and information