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Anthropic: Elevated errors for Claude Mythos 5.1 and Claude Fable 5.1

Impact: majorStatus: resolvedStarted Resolved (17 min)5 updatesSource: stspg.io (opens in new tab)
Summary

Anthropic reported major elevated errors for Claude Mythos 5.1 and Claude Fable 5.1 across claude.ai, Claude API (api.anthropic.com), Claude Code and Claude Cowork. The incident started 2026-09-11 14:19 UTC, lasted 17 min and was resolved after a fix was deployed; Anthropic separately reported impact from 13:57 to 14:20 UTC.

Machine-written from the archived incident (Sol). Check the timeline before relying on it.

Affected components: Claude CoworkClaude API (api.anthropic.com)claude.aiClaude Code

Timeline of updates

  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

Rewindex changes for this incident

Impact, status and times are the vendor’s own, as last archived. View on stspg.io (opens in new tab). Anthropic profile · Recent Anthropic incidents · Markdown · JSON