Elevated errors for multiple models

Timeline

1. Sep 3, 2026, 4:23 PM UTC

   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.

2. Sep 3, 2026, 4:06 PM UTC

   A fix has been deployed for Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 and we are monitoring for recovery.

3. Sep 3, 2026, 3:25 PM UTC

   The only affected models right now are Opus 4.8 and Opus 5. The rest of the models have recovered to baseline error rate.

4. Sep 3, 2026, 2:49 PM UTC

   We are continuing to work on a fix for this issue.

5. Sep 3, 2026, 1:50 PM UTC

   An exhaustive list of affected models: Mythos/Fable 5.1, Mythos/Fable 5, Opus 5, Opus 4.8, Opus 4.6.

6. Sep 3, 2026, 1:41 PM UTC

   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.

7. Sep 3, 2026, 1:26 PM UTC

   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.