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All agents  /  Claude API  /  History  /  Sep 15, 2026

Claude API outage on Sep 15, 2026: intermittent error spikes for Claude Mythos 5.1 and Claude Fable 5.1

Resolved after 1 h 26 min.

09:48 UTC to 11:14 UTC your time. Anthropic: “Intermittent error spikes for Claude Mythos 5.1 and Claude Fable 5.1.” 0 reports here during the incident.

Claude APIUpRight now Claude API is up. See live status

Reports during the incident

Every 15 minutes, 08:45 UTC to 12:15 UTC. Grey: normal. Red line: official incident.
08:45 UTC09:48 UTC11:14 UTC12:15 UTC

What people reported

0 reports during the incident

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Anthropic's updates

Quoted from status.claude.com

  1. 09:48 UTC

    Investigating

    We are investigating elevated errors on requests to Claude Mythos 5.1 and Claude Fable 5.1. We will provide an update as soon as possible.

  2. 09:52 UTC

    Investigating

    We are investigating elevated errors on requests to Claude Mythos 5.1 and Claude Fable 5.1. We will provide an update as soon as possible.

  3. 10:50 UTC

    Monitoring

    A fix has been deployed for Claude Mythos 5.1 and Claude Fable 5.1 and we are monitoring to ensure it has resolved the issue.

  4. 11:14 UTC

    Resolved

    A fix has been deployed for Claude Mythos 5.1 and Claude Fable 5.1 and we are monitoring to ensure it has resolved the issue.

Other Claude API incidents

Nov 826 minDegraded performance for Claude Fable 5.1Details
Oct 2741 minElevated errors for Claude Sonnet 5.5Details
Oct 2742 minElevated errors for Claude Sonnet 5.5Details
All Claude API incidents

Other agents

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