Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

langchain: an agent run is reported as invoke_workflow, with no invoke_agent span

Open
  • Is something wrong?
#387 2 comments 0 reactions 1 assignee View on GitHub

Maintainers usually reply within 1 day

@AgentGymLeader is already working on this.

Since Aug 14, 2026.

Assessment

This issue has not been assessed yet.

Description

opentelemetry-instrumentation-genai-langchain 1.0b0 emits no invoke_agent span for an idiomatic LangChain agent run. The agent invocation is reported as invoke_workflow instead, so an agent application produces no agent telemetry at all.

Repro

from langchain.agents import create_agent
from langchain_openai import ChatOpenAI

agent = create_agent(
    model=ChatOpenAI(model="gpt-4o-mini", max_tokens=100),
    tools=[],
    system_prompt="You are a helpful assistant.",
    name="weather_assistant",
)
agent.invoke({"messages": [HumanMessage(content="hi")]})

with from langchain_core.messages import HumanMessage, run under
opentelemetry-instrument. (Passing the message as a plain
{"role": ..., "content": ...} dict instead raises inside the callback and
loses the span entirely — that is a separate bug, filed alongside this one.)

Expected: an invoke_agent weather_assistant span, per the GenAI semantic conventions.

Actual: invoke_workflow weather_assistant, with the chat span beneath it. The agent name resolves correctly — it is only the operation that is wrong.

The span does appear if the caller passes an OpenTelemetry-specific metadata key:

agent.invoke(
    {"messages": [HumanMessage(content="hi")]},
    config={"metadata": {"agent_name": "weather_assistant"}},
)

which emits invoke_agent weather_assistant as expected.

Why it happens

LangChain already tells the callback that this is an agent, and what it is called. Dumping every on_chain_start for the run above gives:

root=True   serialized.name=None  kwargs.name='weather_assistant'
            metadata_keys=['lc_agent_name', 'ls_integration']
root=False  serialized.name=None  kwargs.name='model'
            metadata_keys=[..., 'langgraph_node', 'lc_agent_name', ...]

So the root chain carries the agent name twice: as kwargs["name"] and as metadata["lc_agent_name"].

classify_chain_run in operation_mapping.py does not look at either:

  1. _has_agent_signals(metadata) accepts only metadata["otel_agent_span"], metadata["agent_name"] and metadata["agent_type"]. LangChain sets none of these, so the agent branch is never taken.
  2. _looks_like_workflow is reached next. serialized is empty here, so it falls through to its final return True and the run is classified as a workflow.

resolve_agent_name would already return "weather_assistant" from kwargs["name"], but it is only consulted for suppression and inside the agent branch that is never entered.

Requiring metadata["agent_name"] means the instrumentation reports agents only for applications modified to describe themselves to it, which defeats zero-code instrumentation.

Suggested fix

Treat metadata["lc_agent_name"] as an agent signal in _has_agent_signals. Note that nested LangGraph nodes carry lc_agent_name too, so the root needs distinguishing — parent_run_id is None, or the absence of langgraph_node, both separate it from the model node in the trace above.

Context

Found while adding LangChain conformance scenarios in
https://github.com/open-telemetry/semantic-conventions-conformance/pull/33.
The scenarios there deliberately stay idiomatic and record the missing agent
span as a gap.

Dominant language
Python
Stars
42
Forks
74
Avg merge
1d 23h
Merged PRs (30d)
122

Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from open-telemetry/opentelemetry-python-genai

All issues in open-telemetry/opentelemetry-python-genai

Similar issues

More Python issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.