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Models / Mistral

Leanstral 1.5

Deprecated

Specialist model for Lean 4 formal proof engineering, automated theorem proving and autoformalization -> not a general chat model. Labs tier, sparse MoE 119B total / 6.5B active. FREE during the Labs preview: pricing.free=true, $0/M in and out per the official docs model schema. Open weights: Apache 2.0 (huggingface.co/mistralai/Leanstral-1.5-119B-A6B). Text + image in, text out; 256K context, 128K max output. DEPRECATED: the docs schema file (platform-docs-public, src/schema/models/models/leanstral-1-5.ts, read 2026-10-02) now reads status 'Deprecated', legacy true, metadata deprecationDate 2026-09-29 and retirementDate 2026-09-30, with no replacement named. The retirement date has passed but Mistral still states Deprecated rather than Retired, so the status follows what the provider declares. Until 2026-10-02 the row was preview: Mistral marked it Active in its experimental Labs tier, which this catalog normalizes to preview (a Labs model is not a GA production model, and that also kept the catalog's first $0 model out of the GA 'cheapest' rankings where a free specialist would rank misleadingly). Knowledge cutoff not published -> null.

Leanstral 1.5 by Mistral costs Free per 1M input tokens and Free per 1M output tokens (Free/1M blended), with a 256K (256.000-token) context window. It is deprecated, shutting down 30 Sep 2026. Its weights are publicly downloadable, so it can be self-hosted on your own infrastructure.

Last verified: 24 Oct 2026 · sourced from official provider documentation

Retired on 30 Sep 2026 · deprecated since 29 Sep 2026

Lifecycle warning

This model is deprecated.

Read the Leanstral 1.5 migration guide → replacement & cheapest alternatives

Provider
Mistral
Status
Deprecated
Input price
Free / 1M tokens
Output price
Free / 1M tokens
Cached input
—
Blended price
Free / 1M tokens
Context window
256.000 tokens (256K)
Max output
128.000 tokens
Modality
text, vision
Open weights
Yes — self-hostable
Knowledge cutoff
—
Released
30 Jun 2026
API string
labs-leanstral-1-5

Source: Mistral official documentation ↗

See also

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FAQ

Leanstral 1.5 — questions & answers

How much does Leanstral 1.5 cost?

Leanstral 1.5 is priced at Free per 1M input tokens and Free per 1M output tokens (Free/1M blended at a 3:1 input-to-output ratio).

What is the context window of Leanstral 1.5?

Leanstral 1.5 has a 256.000-token context window (256K), with up to 128.000 output tokens per request.

Is Leanstral 1.5 being deprecated or retired?

Leanstral 1.5 is deprecated. Its scheduled shutdown date is 30 Sep 2026.

Does Leanstral 1.5 support image or vision input?

Yes — Leanstral 1.5 accepts image input. Listed modalities: text, vision.

Can I self-host Leanstral 1.5?

Yes — Leanstral 1.5 is an open-weight model: its weights are publicly downloadable, so you can run it on your own infrastructure (subject to its license) instead of only calling Mistral's API.

What is the API model string for Leanstral 1.5?

The API model identifier for Leanstral 1.5 is "labs-leanstral-1-5" when calling Mistral's API.