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Anthropic: Elevated errors for Claude Mythos 5.1 and Claude Fable 5.1

claude.com
September 2026 11 Major incident

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

Started

14:19 UTC

Duration

Lasted 19m

Source

IsDown

Next time

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Affected components: claude.ai, api.anthropic.com

What happened?

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

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