Major incident

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

Affected: claude.ai, Claude API (api.anthropic.com), Claude Code, Claude Cowork

Current status of Anthropic (Claude): Operational — live Anthropic (Claude) status

Timeline

1. Sep 11, 2026, 14:19 UTC
   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. Sep 11, 2026, 14:21 UTC
   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. Sep 11, 2026, 14:28 UTC
   monitoring
   A fix has been deployed for Claude Mythos 5.1 and Claude Fable 5.1 and we are monitoring for recovery.
4. Sep 11, 2026, 14:28 UTC
   monitoring
   A fix has been deployed for the issue affecting Claude services and we are monitoring for recovery.
5. Sep 11, 2026, 14:37 UTC
   resolved
   The issue affecting Claude services has been resolved. Impact occurred from 13:57 to 14:20 UTC

Updates as published by Anthropic (Claude) (original).