Leanstral 1.5

Leanstral 1.5

Mistral AI
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+

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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.

About

Patronus AI provides frontier AI labs with training data, tasks, and simulated environments for reinforcement learning. The company builds RL environments that replicate real-world digital workflows across software engineering, computer use, customer support, and financial services. Each environment pairs simulated applications with tasks and reward signals, so models can practice long-horizon, multi-step work under realistic conditions such as latency, interface changes, and unexpected pop-ups. Patronus AI also develops Digital World Models, AI models trained to predict how digital environments behave, which are used to generate and evolve training environments at scale as models improve. Its work spans reinforcement learning environments and digital world models for agents operating in software, supporting post-training, benchmarking, and evaluation of frontier AI models and agents.

Platforms Supported

Windows Not Supported
Mac Not Supported
Linux Not Supported
Cloud Supported
On-Premises Not Supported
iPhone Not Supported
iPad Not Supported
Android Not Supported
Chromebook Not Supported

Platforms Supported

Windows Not Supported
Mac Not Supported
Linux Not Supported
Cloud Supported
On-Premises Supported
iPhone Not Supported
iPad Not Supported
Android Not Supported
Chromebook Not Supported

Audience

Engineers and researchers who need an open model for theorem proving, proof debugging, and real-world code verification

Audience

Frontier AI labs training and evaluating AI models and agents

Support

Phone Support Not Supported
24/7 Live Support Not Supported
Online Supported

Support

Phone Support Not Supported
24/7 Live Support Not Supported
Online Supported

API

Offers API Supported

API

Offers API Supported

Screenshots and Videos

Screenshots and Videos

Pricing

Free
Free Version Supported
Free Trial Not Supported

Pricing

Custom pricing based on project scope. Contact Patronus AI to discuss.
Free Version Not Supported
Free Trial Not Supported

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 Supported
Webinars Not Supported
Live Online Not Supported
In Person Not Supported

Training

Documentation Supported
Webinars Not Supported
Live Online Not Supported
In Person Not Supported

Company Information

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

Company Information

Patronus AI
Founded: 2023
United States
www.patronus.ai/

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Categories

AI Models Supported

Categories

Artificial Intelligence Features

Chatbot Not Supported
For eCommerce Not Supported
For Healthcare Not Supported
For Sales Not Supported
Image Recognition Not Supported
Machine Learning Supported
Multi-Language Not Supported
Natural Language Processing Supported
Predictive Analytics Not Supported
Process/Workflow Automation Not Supported
Rules-Based Automation Not Supported
Virtual Personal Assistant (VPA) Not Supported

Integrations

No info available.

Integrations

No info available.
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