Does Labs Leanstral 1.5.1 support zero data retention?

Not by default. See the per-route data-handling section for each route's logging stance and retention window.

Where is Labs Leanstral 1.5.1 hosted?

Labs Leanstral 1.5.1 runs on EU hosting routes through the Opper gateway, with contractually enforced residency on supported providers.

Is Labs Leanstral 1.5.1 trained on prompts and outputs?

No. Every hosting route for Labs Leanstral 1.5.1 is configured so customer prompts and outputs are not used to train models by default.

Is a GDPR DPA available for Labs Leanstral 1.5.1?

Yes. A GDPR Data Processing Agreement is available on at least one route serving Labs Leanstral 1.5.1. Contact hello@opper.ai to receive it.

Labs Leanstral 1.5.1

by Mistral

The point release of Mistral's experimental proof engineering line, Labs Leanstral 1.5.1 supersedes the initial Leanstral 1.5 endpoint while keeping its recipe intact, a mixture-of-experts design with 119 billion total parameters, 6.5 billion active per token, and a 256K context window. Like 1.5 it writes and checks Lean 4 proofs, translating informal mathematics into machine-checkable statements and searching for proofs autonomously. As the current revision it carries the refinements accumulated since the June 2026 debut of 1.5, making it the endpoint to reach for when staying on the freshest build of the line matters. The workload profile is unchanged, automated theorem proving, autoformalization, and formal verification of program correctness.

Open in playground Try in chat Compare

Key info

Input

Output

Features

Context window

262K

Max output

—

Input price

— /1M

Output price

— /1M

EU residency available
No training by default
GDPR DPA available

Available routes

Labs Leanstral 1.5.1 runs on 1 route through the Opper gateway. Compare residency, ZDR, and training posture at a glance — full data-handling detail per route below.

Provider	Region	Zero data retention	Training	Input	Output
Mistral	EU	Not by default	No	—	—

Uptime and availability

Labs Leanstral 1.5.1 runs on a single route through the Opper gateway today, so its availability is that provider's availability.

100%route uptime, last 30 days

Single route, no failover target within this model.

Name a second model in the same request and the gateway tries it on retriable errors, so a busy hour never has to reach your users. Set up a fallback chain.

Measured over the last 30 days from each provider's official status feed via StatusGator. Refreshed hourly. See uptime for every provider Opper monitors.

Data handling per route

Each route hosting Labs Leanstral 1.5.1 has its own privacy posture, residency, and GDPR terms. Postures are maintained by Opper with a last-verification timestamp.

Mistral — France🇫🇷

Zero data retention is not on by default — abuse monitoring, 30-day retention. No training on customer data. EU; DPA available.

Zero data retention: Not by default — abuse monitoring, 30-day retention. Derived from the logging and moderation facts.
Training: No training on customer data.
Logging: Abuse monitoring (30-day retention)
Moderation: Not established
Caching: Not established
Subprocessor access: Not established
GDPR DPA: DPA available
Transfer mechanism: Not applicable — data stays in EU

Get started

Call Labs Leanstral 1.5.1 through the Opper gateway with one API key. Let your coding agent set it up, or call it directly — Opper is drop-in compatible with the OpenAI, Anthropic, and Google AI SDKs.

Set it up with your agent

Copy this and paste it into a coding agent like Claude Code, Cursor or Codex and it'll wire up Opper for you.

Or call it directly

1import OpenAI from "openai";
2
3const client = new OpenAI({
4  apiKey: process.env.OPPER_API_KEY,
5  baseURL: "https://api.opper.ai/v3/compat",
6});
7
8const completion = await client.chat.completions.create({
9  model: "mistral/labs-leanstral-1-5-1",
10  messages: [{ role: "user", content: "Hello" }],
11});
12console.log(completion.choices[0].message.content);