Major incident

Anthropic (Claude): Intermittent error spikes 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 15, 2026, 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. Sep 15, 2026, 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. Sep 15, 2026, 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. Sep 15, 2026, 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.

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