Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5

Summary

Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5

The issue affecting Claude models has been resolved. Impact occurred from 16:28 PT / 23:28 UTC on October 23 to 16:59 PT / 23:59 UTC on October 23.

• Started

  Oct 23, 2026 · 11:37 PM

• Resolved

  Oct 24, 2026 · 12:11 AM

• Duration

  33m

• Severity

  Critical

• ◐

  Investigating

  Oct 23 · 11:37 PM Claude

  We are investigating elevated errors on requests to Claude Fable 5.1. We will provide an update as soon as possible.

• ◆

  Identified

  Oct 23 · 11:39 PM Claude

  We have identified the cause of elevated errors on requests to Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5, as well as fast mode requests to Opus 5.5 and are working on a fix. We will provide an update as soon as possible.

• ◉

  Monitoring

  Oct 23 · 11:54 PM Claude

  We are seeing success rates return to normal for all affected models, and are continuing to monitor to ensure no further issues.

• ✓

  Resolved

  Oct 24 · 12:11 AM Claude

  The issue affecting Claude models has been resolved. Impact occurred from 16:28 PT / 23:28 UTC on October 23 to 16:59 PT / 23:59 UTC on October 23.