Elevated errors for multiple models

Summary

Elevated errors for multiple models

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.

• Started

  Sep 3, 2026 · 1:26 PM

• Resolved

  Sep 3, 2026 · 4:23 PM

• Duration

  2h 57m

• Severity

  Major

• ◐

  Investigating

  Sep 3 · 1:26 PM Claude

  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.

• ◆

  Identified

  Sep 3 · 1:41 PM Claude

  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.

• ◆

  Identified

  Sep 3 · 1:50 PM Claude

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

• ◆

  Identified

  Sep 3 · 2:49 PM Claude

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

• ◆

  Identified

  Sep 3 · 3:25 PM Claude

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

• ◉

  Monitoring

  Sep 3 · 4:06 PM Claude

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

• ✓

  Resolved

  Sep 3 · 4:23 PM Claude

  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.