Leanstral 1.5 - Mistral AI

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June 30, 2026

Labs v 1.5

Leanstral 1.5

An updated Lean 4 formal proof engineering model optimised for automated theorem proving and autoformalization. 119B total parameters, 6.5B active.

labs-leanstral-1-5

Speed

Performance

Modalities

Context

i

256k

Price

i

$0

Speed

Performance

Modalities

Context

256k

Price

$0

FEATURES WEIGHTS

Features

Chat Completions /v1/chat/completions

Function Calling /v1/chat/completions/v1/conversations

Agents & Conversations /v1/agents/v1/conversations

Built-In Tools /v1/agents/v1/conversations

Structured Outputs /v1/chat/completions/v1/conversations

Predicted Outputs /v1/chat/completions/v1/conversations

Prefix /v1/chat/completions/v1/conversations

OCR /v1/ocr

Annotations - Structured /v1/ocr

BBox Extraction /v1/ocr

Document QnA /v1/chat/completions/v1/conversations

FIM /v1/fim/completions

Embeddings /v1/embeddings

Moderations /v1/moderations

Chat Moderations /v1/chat/moderations

Transcriptions /v1/audio/transcriptions

Text to Speech /v1/audio/speech

Timestamps /v1/audio/transcriptions

Batching /v1/batch

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