Incident

Updates

1. investigating Sep 3, 2026, 9:26 PM GMT+08:00

   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.

2. identified Sep 3, 2026, 9:41 PM GMT+08:00

   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.

3. identified Sep 3, 2026, 9:50 PM GMT+08:00

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

4. identified Sep 3, 2026, 10:49 PM GMT+08:00

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

5. identified Sep 3, 2026, 11:25 PM GMT+08:00

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

6. monitoring Sep 4, 2026, 12:06 AM GMT+08:00

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

7. resolved Sep 4, 2026, 12:23 AM GMT+08:00

   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.