Anthropic mid-stream TransportError not wrapped as APIConnectionError in SSE streaming

What this error means

httpx.TransportError (RemoteProtocolError, ReadError, ConnectError) leaked during SSE body iteration instead of APIConnectionError is a Anthropic API failure pattern reported for developers trying to fix streaming connection drops causing unhandled httpx exceptions instead of apiconnectionerror, breaking standard retry logic in production applications. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub PR #1552 in anthropics/anthropic-sdk-python (created 2026-05-16). Mid-stream transport failures leak as bare httpx exceptions bypassing the SDK’s retry wrapper. Customers’ try/except for APIConnectionError miss these drops entirely. Critical for production AI agent workloads using streaming. Category: Anthropic API — paid API service error.

Common causes

• GitHub PR #1552 in anthropics/anthropic-sdk-python (created 2026-05-16). Mid-stream transport failures leak as bare httpx exceptions bypassing the SDK’s retry wrapper. Customers’ try/except for APIConnectionError miss these drops entirely. Critical for production AI agent workloads using streaming. Category: Anthropic API — paid API service error.

Quick fixes

1. Confirm the exact error signature matches httpx.TransportError (RemoteProtocolError, ReadError, ConnectError) leaked during SSE body iteration instead of APIConnectionError.
2. Check the Anthropic API account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

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/pull/1552

Evidence note: GitHub PR #1552 in anthropics/anthropic-sdk-python (created 2026-05-16). Mid-stream transport failures leak as bare httpx exceptions bypassing the SDK’s retry wrapper. Customers’ try/except for APIConnectionError miss these drops entirely. Critical for production AI agent workloads using streaming. Category: Anthropic API — paid API service error.

Related errors

• Anthropic API

FAQ

What should I check first?

Start with the exact httpx.TransportError (RemoteProtocolError, ReadError, ConnectError) leaked during SSE body iteration instead of APIConnectionError 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 httpx.TransportError (RemoteProtocolError, ReadError, ConnectError) leaked during SSE body iteration instead of APIConnectionError.