The issue affecting Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 has been resolved. Impact has ended as of 9:16 PT / 16:16 UTC.
Posted Sep 03, 2026 - 16:23 UTC
Monitoring
A fix has been deployed for Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 and we are monitoring for recovery.
Posted Sep 03, 2026 - 16:06 UTC
Update
The only affected models right now are Opus 4.8 and Opus 5. The rest of the models have recovered to baseline error rate.
Posted Sep 03, 2026 - 15:25 UTC
Update
We are continuing to work on a fix for this issue.
Posted Sep 03, 2026 - 14:49 UTC
Update
An exhaustive list of affected models: Mythos/Fable 5.1, Mythos/Fable 5, Opus 5, Opus 4.8, Opus 4.6.
Posted Sep 03, 2026 - 13:50 UTC
Identified
We have identified the cause of elevated errors on requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 and are working on a fix. We will provide an update as soon as possible.
Posted Sep 03, 2026 - 13:41 UTC
Investigating
We are investigating elevated errors on requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. We will provide an update as soon as possible.
Posted Sep 03, 2026 - 13:26 UTC
This incident affected: claude.ai, Claude API (api.anthropic.com), Claude Code, and Claude Cowork.