A 529 means Anthropic is out of capacity, not that your key or quota is at fault. Retry with backoff, then fail over to another provider or fallback model to keep agents running.
Key takeaways · AI-distilled
A 529 overloaded_error means Anthropic's API lacks capacity for that model across all users, so it is not about your key or plan and does not count against quota. A higher tier prevents 429 rate-limit errors, which come from your own usage, but not 529s.
Anthropic's SDKs already retry 5xx errors with exponential backoff, twice by default, and Claude Code retries up to 10 times before showing Repeated 529 Overloaded errors. OpenRouter notes more retries only lengthen the wait when a model stays busy.
Because Anthropic tracks capacity per model, switching models with /model is the quickest no-setup fix in Claude Code. OpenRouter lists Sonnet, Opus and Haiku 5.5 on five providers each, with Sonnet 5.5 input at $2.00 per million on every global endpoint.
On OpenRouter, setting a provider order disables default load balancing, while allow_fallbacks false or a restrictive only list stops failover entirely; model fallbacks trigger on any error from the first model, including rate limits and context windowThe maximum amount of text a model can consider at once — its working memory for the current conversation or task.Full definition →-length errors.
Terms in this piece · Glossary
context window — The maximum amount of text a model can consider at once — its working memory for the current conversation or task.
