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

Affected components

• Claude API (api.anthropic.com)
• Claude Code
• Claude Cowork
• claude.ai

1. resolvedSep 11, 2026, 14:37 UTC

   The issue affecting Claude services has been resolved. Impact occurred from 13:57 to 14:20 UTC

2. monitoringSep 11, 2026, 14:28 UTC

   A fix has been deployed for the issue affecting Claude services and we are monitoring for recovery.

3. monitoringSep 11, 2026, 14:28 UTC

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

4. identifiedSep 11, 2026, 14:21 UTC

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

5. investigatingSep 11, 2026, 14:19 UTC

   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.

What APIStatus.watch saw

Our 5-minute checks didn't record a change in Anthropic's overall status around this incident. Smaller or regional incidents often leave a provider's overall status green.

Other services with incidents at the same time

Overlapping incidents aren't necessarily related.

• Elasticsearch: Replication bug causing slow recoveriesMajor · Sep 1, 2026, 08:16 UTC
• MongoDB Atlas: Impaired Cluster operations in AWS me-central-1 and AWS me-south-1Major · Sep 3, 2026, 16:44 UTC
• Elasticsearch: Elastic Agent enrollment/check-in failures on 9.5.3 (and 9.4.6) with Fleet remote Elasticsearch outputMajor · Sep 9, 2026, 20:44 UTC
• Supabase: Unresponsive ProjectsMajor · Sep 10, 2026, 15:26 UTC
• Claude: Degraded functionality for Claude Cowork on WindowsMajor · Sep 10, 2026, 15:54 UTC
• OVHcloud: [SBG5/7][Compute - Instance] - Some Instances Incident NotificationMajor · Sep 10, 2026, 22:22 UTC
• Telnyx: Intermittent delays for some outbound messagesMinor · Sep 2, 2026, 21:33 UTC
• Shippo: Elevated error rate on USPS QR code generationMinor · Sep 11, 2026, 01:33 UTC

How often does Anthropic have incidents?

Anthropic reported 47 incidents in the last 90 days, 21 of them major or critical. A typical incident lasted 1h 4m. See Anthropic's uptime and incident history