Anthropic Streaming SDK Returns HTTP 200 Instead of 529 for Overloaded Errors

What this error means

OverloadedError status_code=200 (should be 529) in mid-stream SSE error handling is a Anthropic API failure pattern reported for developers trying to debug why anthropic streaming api reports http 200 status for overloaded/sse_error events instead of correct 529 status code. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub issue #1258 on anthropics/anthropic-sdk-python (closed via PRs). Reports mid-stream SSE overloaded_error wrapped with wrong status_code=200, breaking retry logic in LangChain and other integrations. Affects paid API billing and production reliability. Mapping reason: Anthropic SDK-level API behavior error.

Common causes

• GitHub issue #1258 on anthropics/anthropic-sdk-python (closed via PRs). Reports mid-stream SSE overloaded_error wrapped with wrong status_code=200, breaking retry logic in LangChain and other integrations. Affects paid API billing and production reliability. Mapping reason: Anthropic SDK-level API behavior error.

Quick fixes

1. Confirm the exact error signature matches OverloadedError status_code=200 (should be 529) in mid-stream SSE error handling.
2. Check the Anthropic API account, local tool state, and provider configuration involved in the failing workflow.
3. Reduce request pressure, check quota or plan limits, and retry with backoff instead of immediate repeated requests.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/anthropics/anthropic-sdk-python/issues/1258

Evidence note: GitHub issue #1258 on anthropics/anthropic-sdk-python (closed via PRs). Reports mid-stream SSE overloaded_error wrapped with wrong status_code=200, breaking retry logic in LangChain and other integrations. Affects paid API billing and production reliability. Mapping reason: Anthropic SDK-level API behavior error.

Related errors

• Anthropic API

FAQ

What should I check first?

Start with the exact OverloadedError status_code=200 (should be 529) in mid-stream SSE error handling text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Anthropic API workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without OverloadedError status_code=200 (should be 529) in mid-stream SSE error handling.