Anthropic Reports Elevated Error Rates for Claude Opus and Mythos 5.1
September 21, 2026
Anthropic is experiencing increased error rates across Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. The incident affects the Claude API, claude.ai, Claude Code, and Claude Cowork.
HOW THIS AFFECTS YOU
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builderYou may experience increased latency or request failures in your production workflows using these models.
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founderReliability issues in core model APIs can impact your product's SLA and user retention.