What changed
Anthropic reported degraded performance across claude.ai, the Claude API, Claude Code, and Claude Cowork on August 18. An intermediate update named Mythos 5, Fable 5, Opus 5, Sonnet 5, Haiku 4.5, and other models; the final report confirms Opus 5 impact from 16:11 to 18:23 UTC.
Why it matters
A shared model-service incident can disrupt consumer, API, coding-agent, and workplace-agent surfaces together. Teams need provider-independent task state and recovery controls instead of treating each client as a separate availability boundary.
What to do
Persist prompts, tool state, approvals, and external writes outside the model session; use bounded retries and fallback models; pause consequential agents during provider degradation; and reconcile partial actions before resuming after recovery.
Caveat
The final notice names only Opus 5 for the confirmed 16:11–18:23 UTC window, while an intermediate update names several models. Anthropic gives no root cause, error rate, customer count, or model-specific duration for the wider set.