Anthropic Investigating Elevated Errors Across Multiple Claude Models

Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 experiencing service issues.

By The Downtime · Sep 3, 2026 · 1:32 PM ·Updated 5 days ago

Anthropic is investigating elevated error rates affecting requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. The company has classified the incident as major impact and is currently in the investigating phase.

Anthropovic develops Claude, an AI assistant widely used by developers, enterprises, and researchers for a range of applications.

The incident was first reported as under investigation with no additional details provided. Anthropic stated it will publish updates as the investigation progresses.

This is a developing story. The Downtime will continue monitoring for updates from Anthropic's status page.

🕒 Live updates (7)

resolved Sep 3, 4:23 PM

The issue affecting Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 has been resolved. Impact has ended as of 9:16 PT / 16:16 UTC.

monitoring Sep 3, 4:06 PM

A fix has been deployed for Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 and we are monitoring for recovery.

identified Sep 3, 3:25 PM

The only affected models right now are Opus 4.8 and Opus 5. The rest of the models have recovered to baseline error rate.

identified Sep 3, 2:49 PM

We are continuing to work on a fix for this issue.

identified Sep 3, 1:50 PM

An exhaustive list of affected models: Mythos/Fable 5.1, Mythos/Fable 5, Opus 5, Opus 4.8, Opus 4.6.

identified Sep 3, 1:41 PM

We have identified the cause of elevated errors on requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 and are working on a fix. We will provide an update as soon as possible.

investigating Sep 3, 1:26 PM

We are investigating elevated errors on requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. We will provide an update as soon as possible.

📎 Sources

Anthropic status ↗

Outage details are aggregated from official provider status pages. The Downtime reports them as a public service and is not affiliated with the providers named.