Claude 529 overloaded errors: what they mean and how to fix them
AIA 529 overloaded_error means Anthropic's API lacks capacity for a Claude model across all users, not that the caller's usage is at fault. The OpenRouter Blog recommends retrying with exponential backoff first, then sending the same model to another provider, since Claude Sonnet, Opus and Haiku 5.5 are each served by five providers on OpenRouter.
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OpenRouter Blog · openrouter.aiPublished · added here
Original title: Claude 529 Overloaded: What It Means and How to Fix It