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Anthropic: Intermittent error spikes for Claude Mythos 5.1 and Claude Fable 5.1

claude.com
September 2026 15 Major incident

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.

Started

09:48 UTC

Duration

Lasted 1h 29m

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 Mythos 5.1 and Claude Fable 5.1. We will provide an update as soon as possible.

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