Anthropic incident

Elevated errors for Claude Mythos 5.1 and Claude Fable 5.1

Major Resolved Upstream link ↗

Started

September 11, 2026 at 02:19 PM UTC

Duration

17 min

Resolved

September 11, 2026 at 02:37 PM UTC

Updates timeline

  1. Investigating

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

  2. Identified

    We have identified the cause of elevated errors on requests to Claude Mythos 5.1 and Claude Fable 5.1 and are working on a fix. We will provide an update as soon as possible.

  3. Monitoring

    A fix has been deployed for Claude Mythos 5.1 and Claude Fable 5.1 and we are monitoring for recovery.

  4. Monitoring

    A fix has been deployed for the issue affecting Claude services and we are monitoring for recovery.

  5. Resolved

    The issue affecting Claude services has been resolved. Impact occurred from 13:57 to 14:20 UTC

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