MistralAI-User: Robots.txt & Crawl Policy Reference

AI Summary: MistralAI-User is an on-demand, user-triggered fetcher operated by Mistral AI. It is used exclusively when a user of Mistral's products (like Le Chat) requests the AI to browse a specific webpage. It is not used for background AI training.

Role and policy boundary

MistralAI-User serves as a live browsing agent. When a user asks Mistral's Le Chat to summarize an article or extract data from a URL, this User-Agent makes the HTTP request. Mistral explicitly states this bot is not used to crawl content for training their foundation models.

A robots rule is a declaration of intent; it does not replace authentication, authorization, or rate limiting. Start with a dedicated group:

User-agent: MistralAI-User
Allow: /
Disallow: /staging/
Disallow: /internal/

To stop access for the entire site, use:

User-agent: MistralAI-User
Disallow: /

Avoid assuming that User-agent: * expresses the same business intent. A wildcard can affect assistant and training crawlers too, and it makes later audits harder because the source of the decision is less specific.

Layered verification

Verify the same URL through each control plane instead of assuming that one green signal represents the whole request path. Compare the bot-specific robots group, the page-level metadata, and the response headers captured at the public edge.

Mistral AI is known for strictly respecting robots.txt directives for MistralAI-User. If you block this User-Agent, Mistral's AI assistants will refuse to read your pages when prompted by users, protecting your content from real-time AI summarization.

The Policy Engine evaluates the selected user-agent, path scope, and the other supplied layers independently. It can therefore explain why a bot is allowed while another is blocked, rather than returning one blended website score.

Page-level directives can still override the intended outcome for indexing:

<meta name="robots" content="noai, noimageai">

X-Robots-Tag: noai, noimageai

If a response uses these tags, the report marks the result as blocked or conflicting even if the crawler-specific robots group is permissive. This is especially important for canonical pages served through an edge cache where headers may differ from the origin response.

WAF and Nginx remediation examples

{
  "description": "Observe mistralai-user candidates",
  "expression": "lower(http.user_agent) contains \"mistralai-user\"",
  "action": "log"
}

While robots.txt is generally effective for MistralAI-User, you can add a WAF rule for defense-in-depth observability or hard blocking:

if ($http_user_agent ~* "MistralAI-User") {
    return 403;
}

Use your platform's actual middleware response pattern rather than copying this simplified example without review. Never place a secret, verification token, or internal policy identifier in a public response header.

Review checklist

Use this checklist after every policy change and after a CDN or WAF migration. Record the request URL, User-Agent, HTTP status, final redirect, and the exact evidence used to reach the decision.

Verify that the dedicated group appears before relying on a wildcard, test a representative public and private path, and compare live response headers with robots.txt. Keep the policy close to the content owner's intent and record whether the site wants discovery, citation, or no access at all.

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