Updated 6:50 a.m. Eastern on September 15, 2026
Claude says intermittent error spikes affecting Claude Mythos 5.1 and Claude Fable 5.1 are being monitored after a fix was deployed, according to the latest official update.
What is affected
The official incident covers intermittent error spikes on requests to Claude Mythos 5.1 and Claude Fable 5.1, with claude.ai, Claude API, Claude Code, and Claude Cowork listed as components.
Official update timeline
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.
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.
A fix has been deployed for Claude Mythos 5.1 and Claude Fable 5.1 and we are monitoring to ensure it has resolved the issue.
