An Error 529 from the Anthropic API is an overloaded_error. Unlike a 429 error (which means you are sending too many requests), a 529 error means Anthropic’s servers are currently at maximum capacity and cannot process your request.
Why you are seeing this right now
This is almost certainly caused by the active service incident affecting Claude Opus 4.5.
Current Status: There is an ongoing “Elevated Error Rates” incident for the Opus 4.5 model specifically.
Symptoms: Requests hang or return
529 Overloadedimmediately.Meaning: This is a global issue, not a problem with your API key or code.
Immediate Fixes
1. Switch Models (Recommended)
If you are using Opus 4.5 in your API calls or “Claude Code” tool, switch to Claude 3.5 Sonnet (claude-3-5-sonnet-20241022). It is currently operational and not affected by the specific Opus outage.
2. Implement Exponential Backoff
If you are writing a script/app and must use the overloaded model, you cannot just retry immediately (that will just fail again). You must use “exponential backoff”:
Attempt 1: Fail.
Wait 1 second -> Retry.
Wait 2 seconds -> Retry.
Wait 4 seconds -> Retry.
Note: Most official SDKs handle this automatically, but during a severe outage like today’s, they will eventually time out.
529 vs. 429 Cheatsheet
Error Code | Name | Whose fault is it? | Solution |
| 529 | overloaded_error | Anthropic’s | Wait or switch models. |
| 429 | rate_limit_error | Yours | Slow down your requests or buy more credits. |
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