Anthropic API / Anthropic API

Anthropic SDK: Mid-stream SSE errors return HTTP 200 instead of correct error status code

Fix incorrect status code for streaming errors in Anthropic Python SDK so retry/fallback logic based on status_code works correctly Includes evidence for Anthropic API troubleshooting demand.

Source-backed Last updated May 21, 2026 1 source Needs local verification

Category: Anthropic API
Error signature: APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event)
Quick fix: Reduce request pressure, check quota or plan limits, and retry with backoff instead of immediate repeated requests.
Updated: May 21, 2026
Verification status: Source-backed
Evidence: 1 public source URL

Before you change production

This page includes public source URLs in the imported troubleshooting record. Compare those references with your version and environment before applying changes.

Reproduce the smallest failing action and save non-secret logs before changing configuration.
Check versions for Anthropic API, related SDKs, package managers, CI runners, and hosting providers.
Change one setting or dependency at a time, then rerun the same failing command or request.
Avoid destructive commands, credential rotation, billing changes, or security relaxations without a rollback plan.

What this error means

APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event) is a Anthropic API failure pattern reported for developers trying to fix incorrect status code for streaming errors in anthropic python sdk so retry/fallback logic based on status_code works correctly. 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 in anthropics/anthropic-sdk-python (sarth6, Mar 2026). When API returns HTTP 200 (streaming started fine) but then sends an SSE error event like overloaded_error, the SDK creates an APIStatusError with status_code=200 instead of 529. This breaks pydantic-ai FallbackModel which checks status_code >= 500 to decide whether to try the next model. Severity was confirmed by official collaborator dtmeadows and fixed in v0.87.0. High commercial value — impacts production AI workflow reliability.

Common causes

GitHub issue #1258 in anthropics/anthropic-sdk-python (sarth6, Mar 2026). When API returns HTTP 200 (streaming started fine) but then sends an SSE error event like overloaded_error, the SDK creates an APIStatusError with status_code=200 instead of 529. This breaks pydantic-ai FallbackModel which checks status_code >= 500 to decide whether to try the next model. Severity was confirmed by official collaborator dtmeadows and fixed in v0.87.0. High commercial value — impacts production AI workflow reliability.

Quick fixes

Confirm the exact error signature matches APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event).
Check the Anthropic API account, local tool state, and provider configuration involved in the failing workflow.
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

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

Diagnostic flow for this page

Match APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event) exactly before applying the quick fix.
Compare the failing environment with Anthropic API versions, account scope, provider settings, and deployment context.
Check the listed common causes in order, starting with the cause that best matches your logs.
Use the evidence status below to decide whether to confirm against public sources or official documentation.
Apply one reversible change, rerun the smallest failing action, and keep rollback notes.

FAQ

What does APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event) mean in Anthropic API?

APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event) indicates the workflow described by "Anthropic SDK: Mid-stream SSE errors return HTTP 200 instead of correct error status code" failed in a Anthropic API context. Start by confirming the exact signature and the component that emitted it.

What should I check first for APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event)?

Check whether this cause matches your environment: GitHub issue #1258 in anthropics/anthropic-sdk-python (sarth6, Mar 2026). When API returns HTTP 200 (streaming started fine) but then sends an SSE error event like overloaded_error, the SDK creates an APIStatusError with status_code=200 instead of 529. This breaks pydantic-ai FallbackModel which checks status_code >= 500 to decide whether to try the next model. Severity was confirmed by official collaborator dtmeadows and fixed in v0.87.0. High commercial value — impacts production AI workflow reliability.

Is the APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event) guidance source-backed?

The "Anthropic SDK: Mid-stream SSE errors return HTTP 200 instead of correct error status code" page is labeled source-backed. It has 1 public source URL from github.com, so use that evidence status when deciding how much additional verification you need.

When should I avoid the quick fix for APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event)?

For "Anthropic SDK: Mid-stream SSE errors return HTTP 200 instead of correct error status code", avoid applying "Reduce request pressure, check quota or plan limits, and retry with backoff instead of immediate repeated requests." when the error text differs, the affected version or provider is different, or the change would touch credentials, billing, DNS, production deploy settings, or irreversible data.

What should I collect before debugging APIStatusError with status_code=200 when Anthropic API returns overloaded_error / rate_limit_error during streaming (SSE event)?

For "Anthropic SDK: Mid-stream SSE errors return HTTP 200 instead of correct error status code", collect the failing Anthropic API command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.