Problem

I am using Phoenix and connect Smolagents to it via OTLP.

With latest dependencies, I am seeing the following spans:

• FinalAnswerTool (type tool, no parent)
• MCPAdaptTool (type tool, no parent)
• CodeAgent.run (type agent)
  • Step 1 (type chain)
    • OpenAIModel.generate (type llm)
  • Step 2 (type chain)
    • OpenAIModel.generate (type llm)

i.e. the tools are missing the parent and are therefore considered root spans

Previously recorded spans have the following structure:

• CodeAgent.run (type agent)
  • MCPAdaptTool (type tool)
  • FinalAnswerTool (type tool)

i.e. previously tool spans have the agent span as the parent

Steps to reproduce
Please provide a minimal, self-contained, and reproducible example of the bug.

import logging
import os

from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import SimpleSpanProcessor

from openinference.instrumentation.smolagents import SmolagentsInstrumentor
import smolagents


LOGGER = logging.getLogger(__name__)


def configure_otlp(otlp_endpoint: str):
    LOGGER.info('Configuring OTLP: %r', otlp_endpoint)
    trace_provider = TracerProvider()
    trace_provider.add_span_processor(SimpleSpanProcessor(OTLPSpanExporter(otlp_endpoint)))
    SmolagentsInstrumentor().instrument(tracer_provider=trace_provider)


def get_model() -> smolagents.Model:
    return smolagents.OpenAIModel(
        model_id='gpt-5-mini',
        api_key=os.environ['OPENAI_API_KEY']
    )


@smolagents.tool
def today_tool() -> str:
    """
    Provides the current date.
    """
    return "Today is 2026-01-29."


def create_agent() -> smolagents.CodeAgent:
    tools = [
        today_tool
    ]
    return smolagents.CodeAgent(
        tools=tools,
        max_steps=3,
        model=get_model()
    )


def main():
    configure_otlp('http://0.0.0.0:6006/v1/traces')
    agent = create_agent()
    agent.run("What is today's date?")


if __name__ == '__main__':
    logging.basicConfig(level=logging.INFO)
    main()

Actual behavior and error logs

The following spans are created:

• FinalAnswerTool (type tool, no parent)
• SimpleTool (type tool, no parent)
• CodeAgent.run (type agent)
  • Step 1 (type chain)
    • OpenAIModel.generate (type llm)

i.e. the tools are missing the parent and are therefore considered root spans

Expected behavior
A clear and concise description of what you expected to happen.

Expected spans:

• CodeAgent.run (type agent)
  • Step 1 (type chain)
    • OpenAIModel.generate (type llm)
    • SimpleTool (type tool)
    • FinalAnswerTool (type tool)

i.e. the tool spans should have a parent of the corresponding step

Environment:
Please complete the following information:

• OS: [e.g., Linux, macOS, Windows]
• Python version: [e.g., 3.10]
• Package version: (output of pip show smolagents)

OS: Linux
Python version: 3.12.3
Package version: 1.24.0

$ pip list | grep -P 'opentelemetry|openinference|smol|phoenix'
arize-phoenix                            12.33.0
arize-phoenix-client                     1.28.0
arize-phoenix-evals                      2.8.0
arize-phoenix-otel                       0.14.0
openinference-instrumentation            0.1.43
openinference-instrumentation-smolagents 0.1.21
openinference-semantic-conventions       0.1.25
opentelemetry-api                        1.39.1
opentelemetry-exporter-otlp              1.39.1
opentelemetry-exporter-otlp-proto-common 1.39.1
opentelemetry-exporter-otlp-proto-grpc   1.39.1
opentelemetry-exporter-otlp-proto-http   1.39.1
opentelemetry-instrumentation            0.60b1
opentelemetry-proto                      1.39.1
opentelemetry-sdk                        1.39.1
opentelemetry-semantic-conventions       0.60b1
smolagents                               1.24.0

Additional context (optional)
Add any other context, screenshots, or links about the bug here.

screenshot of previous agent span

screenshot of new agent span

screenshot of new root spans

This is working correctly when using the ToolCallingAgent (instead of CodeAgent).

screenshot of ToolCallingAgent.run span with correct hierarchy

Checklist

• I have searched the existing issues and have not found a similar bug report.
• I have provided a minimal, reproducible example.
• I have provided the full traceback of the error.
• I have provided my environment details.
• I am willing to work on this issue and submit a pull request. (optional)

(I didn't tick the last box because I don't really understand how the telemetry works)