Updated 12:23 p.m. Eastern on September 3, 2026
Claude reports that the incident involving elevated errors for multiple models has been resolved. Impact ended at 16:16 UTC. The issue affected Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5.
What is affected
The incident affected requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. Later updates also listed Mythos/Fable 5, Opus 4.8, and Opus 4.6 as affected, with Opus 4.8 and Opus 5 remaining affected until recovery.
Official update timeline
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.
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.
An exhaustive list of affected models: Mythos/Fable 5.1, Mythos/Fable 5, Opus 5, Opus 4.8, Opus 4.6.
We are continuing to work on a fix for this issue.
The only affected models right now are Opus 4.8 and Opus 5. The rest of the models have recovered to baseline error rate.
A fix has been deployed for Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 and we are monitoring for recovery.
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.
