Anthropic API streaming connection closes without message_stop event during tool_use

What this error means

Streaming responses interrupted mid-transmission — connection closes without message_stop event is a Anthropic API failure pattern reported for developers trying to fix anthropic api streaming responses that end abruptly without message_stop event when using tool_use with large json payloads. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub issue #842 (created 2025-11-11, 12 comments). Streaming from Anthropic API is prematurely terminated without message_stop event. Happens specifically with tool_use and large JSON payloads. SDK v0.68.0, Node.js/NestJS. Affects claude-3-5-haiku-latest and other models.

Common causes

• Developers building apps with Anthropic’s streaming API + tool_use experience incomplete responses — the connection closes mid-stream without a message_stop event, leaving the application in an inconsistent state. Particularly affects NestJS and large JSON payload scenarios
• GitHub issue #842 (created 2025-11-11, 12 comments). Streaming from Anthropic API is prematurely terminated without message_stop event. Happens specifically with tool_use and large JSON payloads. SDK v0.68.0, Node.js/NestJS. Affects claude-3-5-haiku-latest and other models.

Quick fixes

1. Confirm the exact error signature matches Streaming responses interrupted mid-transmission — connection closes without message_stop event.
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-typescript/issues/842

Evidence note: GitHub issue #842 (created 2025-11-11, 12 comments). Streaming from Anthropic API is prematurely terminated without message_stop event. Happens specifically with tool_use and large JSON payloads. SDK v0.68.0, Node.js/NestJS. Affects claude-3-5-haiku-latest and other models.

Related errors

• Anthropic streaming response incomplete
• Anthropic API stream disconnects unexpectedly
• message_stop event not received Anthropic

FAQ

What should I check first?

Start with the exact Streaming responses interrupted mid-transmission — connection closes without message_stop event 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 Streaming responses interrupted mid-transmission — connection closes without message_stop event.