Anthropic outage: Intermittent error spikes 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 15, 2026, 11:14 UTC

   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.

2. monitoringSep 15, 2026, 10:50 UTC

   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.

3. investigatingSep 15, 2026, 09:52 UTC

   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.

4. investigatingSep 15, 2026, 09:48 UTC

   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.

What APIStatus.watch saw

• Sep 15, 2026, 09:50 UTCoperational → degraded
• Sep 15, 2026, 11:15 UTCdegraded → operational

Other services with incidents at the same time

Overlapping incidents aren't necessarily related.

• 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
• Twilio: Voice Call Failures from a Subset of Twilio Phone Numbers to Hong KongMinor · Sep 12, 2026, 00:16 UTC
• GitHub: Disruption with some GitHub servicesMinor · Sep 15, 2026, 09:47 UTC
• Grafana Cloud: Increased Execution Time for Browser Checks in Synthetic MonitoringMinor · Sep 15, 2026, 10:00 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