Anthropic API 529 overloaded
Anthropic API 529: Overloaded Error
TL;DR: Anthropic 529 overloaded_error is normally a provider-side capacity signal. Your request may be valid, but the service cannot process it right now.
What this error means
Anthropic API 529 means the provider is overloaded or temporarily unable to serve your request at normal capacity.
provider_overload provider/server side
Is it code, key, rate limit, or server-side?
| Signal | Diagnosis |
|---|---|
| Provider | Anthropic |
| Error | 529 |
| Likely category | provider_overload |
| Likely fault area | provider/server side |
Immediate checklist
- Confirm whether the response type is overloaded_error.
- Retry with exponential backoff and a low max retry count.
- Check whether only one model is affected or all Anthropic models are affected.
- Use a fallback provider or queue non-interactive jobs until the overload clears.
cURL test command
curl https://api.anthropic.com/v1/messages \
-H "x-api-key: $ANTHROPIC_API_KEY" \
-H "anthropic-version: 2023-06-01" \
-H "content-type: application/json" \
-d '{"model":"claude-3-5-haiku-latest","max_tokens":16,"messages":[{"role":"user","content":"ping"}]}' Run this from your server or terminal. llmping does not collect API keys and does not send this command for you.
Common fixes
- Do not treat 529 as a bad API key. It is usually not an auth problem.
- Add backoff, jitter, circuit breaking, and a fallback route for production workloads.
- Lower max_tokens for interactive retries so the fallback path returns quickly.
- Move batch work to a queue and retry later instead of blocking user requests.