Leanstral 1.5

Leanstral 1.5

Mistral AI
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About

Grok 4.1 Fast is an xAI model designed to deliver advanced tool-calling capabilities with a massive 2-million-token context window. It excels at complex real-world tasks such as customer support, finance, troubleshooting, and dynamic agent workflows. The model pairs seamlessly with the new Agent Tools API, which enables real-time web search, X search, file retrieval, and secure code execution. This combination gives developers the power to build fully autonomous, production-grade agents that plan, reason, and use tools effectively. Grok 4.1 Fast is trained with long-horizon reinforcement learning, ensuring stable multi-turn accuracy even across extremely long prompts. With its speed, cost-efficiency, and high benchmark scores, it sets a new standard for scalable enterprise-grade AI agents.

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

This content is ideal for developers, enterprises, and technical teams seeking to build advanced AI agents that require real-time data access, long-context reasoning, and reliable tool-calling capabilities

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

No information available.
Free Version
Free Trial

Pricing

Free
Free Version
Free Trial

Reviews/Ratings

Overall 5.0 / 5
ease 5.0 / 5
features 5.0 / 5
design 5.0 / 5
support 5.0 / 5

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:

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Training

Documentation
Webinars
Live Online
In Person

Training

Documentation
Webinars
Live Online
In Person

Company Information

xAI
Founded: 2023
United States
grok.com

Company Information

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

Alternatives

Alternatives

Leanstral

Leanstral

Mistral AI
DeepSWE

DeepSWE

Agentica Project
SWE-1.5

SWE-1.5

Cognition
Ring 2.6

Ring 2.6

Ant Group
Command R+

Command R+

Cohere AI

Categories

Categories

Integrations

C#
F#
FastRouter
Go
Grok
HTML
Java
JavaScript
Laravel
LaunchLemonade
Microsoft Foundry
PHP
Python
R
Ruby
SQL
TypeScript
Visual Basic
Zo Computer
iMini

Integrations

C#
F#
FastRouter
Go
Grok
HTML
Java
JavaScript
Laravel
LaunchLemonade
Microsoft Foundry
PHP
Python
R
Ruby
SQL
TypeScript
Visual Basic
Zo Computer
iMini
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