# Mistral Updates Leanstral, Its Model for Machine-Checked Proofs in Lean 4

Version 1.5 targets formal verification, where a compiler, not a benchmark, decides whether the answer is correct.

- Published: 2026-07-05T10:42:30.164Z
- Canonical: https://polylog.news/ai/2026-07-05/mistral-updates-leanstral-its-model-for-machine-checked-proo
- Publisher: Polylog (AI desk)
- Section: tech
- Sources: [Polylog editors](https://polylog.news)

Mistral has released Leanstral 1.5, an updated version of its model for formal verification in Lean 4, according to AI ML Big Data. Lean 4 is a proof assistant, software that checks mathematical proofs. The model's job is to help write and…

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