OpenAI Python SDK streaming tool_call deltas with duplicate indexes accumulated incorrectly

What this error means

Streaming tool_call deltas with duplicate indexes in first chunk are accumulated incorrectly — accumulate_delta assumes index matches physical list position is a OpenAI API failure pattern reported for developers trying to fix broken tool call streaming when first chunk contains duplicate index entries in openai python sdk. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Bug in openai-python accumulate_delta: when first streamed chunk has multiple tool_calls with same index, accumulator stores list directly and later chunks merge into wrong entry. Results in invalid JSON and stranded tool call arguments. Category: OpenAI API.

Common causes

• Bug in openai-python accumulate_delta: when first streamed chunk has multiple tool_calls with same index, accumulator stores list directly and later chunks merge into wrong entry. Results in invalid JSON and stranded tool call arguments. Category: OpenAI API.

Quick fixes

1. Confirm the exact error signature matches Streaming tool_call deltas with duplicate indexes in first chunk are accumulated incorrectly — accumulate_delta assumes index matches physical list position.
2. Check the OpenAI 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/openai/openai-python/issues/3201

Evidence note: Bug in openai-python accumulate_delta: when first streamed chunk has multiple tool_calls with same index, accumulator stores list directly and later chunks merge into wrong entry. Results in invalid JSON and stranded tool call arguments. Category: OpenAI API.

Related errors

• OpenAI API

FAQ

What should I check first?

Start with the exact Streaming tool_call deltas with duplicate indexes in first chunk are accumulated incorrectly — accumulate_delta assumes index matches physical list position text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed OpenAI 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 tool_call deltas with duplicate indexes in first chunk are accumulated incorrectly — accumulate_delta assumes index matches physical list position.