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

Incident Report for Claude

Resolved

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.

Posted Oct 24, 2026 - 00:11 UTC

Monitoring

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

Posted Oct 23, 2026 - 23:54 UTC

Identified

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.

Posted Oct 23, 2026 - 23:39 UTC

Investigating

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

Posted Oct 23, 2026 - 23:37 UTC

This incident affected: claude.ai, Claude API (api.anthropic.com), Claude Code, and Claude Cowork.