Issue evidence · AI API · BerriAI/litellm

OpenTelemetry callback records tool-call responses as an empty message

GitHub issue: https://github.com/BerriAI/litellm/issues/45796

Reproduced

A response that is a tool call is exported to the trace with no parts, losing the call id, name and arguments.

What Badgr ran

Ran both of the issue's mocked OpenAI + OpenTelemetry scripts (non-streaming and streaming) against LiteLLM main.

What came back

  • The application received the tool call (lookup).
  • The exported span carried gen_ai.output.messages = [{"role": "assistant", "parts": [], "finish_reason": "tool_calls"}].

Checked 2026-10-11 in Badgr’s local development environment.

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