The incident affected Claude, a service with language models, as well as claude.ai, the Claude API, Claude Code, and Claude Cowork.
Elevated errors occurred in requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. By 01:35 UTC, successful-request rates for Claude Fable 5 and 5.1 and Claude Mythos 5 and 5.1 had returned to normal, while errors affecting Claude Opus 5 were still being fixed.
Claim check:
- The incident affected claude.ai, the Claude API, Claude Code, and Claude Cowork. (confirmed by the publication itself: evidence; «This incident affects: claude.ai, Claude API (api.anthropic.com), Claude Code, and Claude Cowork.»)
- Elevated errors occurred in requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. (confirmed by the publication itself: evidence; «We are investigating elevated errors on requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5.»)
- By 01:35 UTC, successful-request rates for Claude Fable 5 and 5.1 and Claude Mythos 5 and 5.1 had returned to normal, while errors affecting Claude Opus 5 were still being fixed. (confirmed by the publication itself: evidence; «At this time, requests to Claude Fable 5 and 5.1 and Mythos 5 and 5.1 have returned to normal success rates. We are working to resolve remaining errors affecting Claude Opus 5»)
Primary sources:
score 58.9 out of 100 · kind: incident