Elevated errors for Claude Mythos 5.1 and Claude Fable 5.1

Incident Report for Claude

Resolved

The issue affecting Claude Mythos 5.1 and Claude Fable 5.1 has been resolved. Impact occurred from 05:40 PT / 12:40 UTC to 06:10 PT / 13:10 UTC.
Posted Oct 05, 2026 - 13:21 UTC

Investigating

We are investigating elevated errors on requests to Claude Mythos 5.1 and Claude Fable 5.1. We will provide an update as soon as possible.
Posted Oct 05, 2026 - 13:05 UTC
This incident affected: claude.ai, Claude API (api.anthropic.com), Claude Code, and Claude Cowork.