[ENHANCEMENT]Update Instrumentation LC React

[arizedatngo]

Issue:

• When using create_react_agent from LangChain with Arize Phoenix tracing, the final AI message (agent's answer) is missing from the Phoenix trace data.

Root Cause:

• Instrumentation Gap: Arize Phoenix (via OpenInference) doesn’t currently capture the final AgentFinish event from LangChain as a distinct span.
• Callback Missing: The on_agent_finish method in the Arize callback isn’t implemented, so the final AI response is not logged.
• New API Limitation: create_react_agent is a newer interface, and its tracing support is not fully mature in Phoenix/OpenInference yet.
• Confirmed by Sean’s Output: The span data pulled via px.Client().query_spans() includes:
• A HumanMessage (user question)
• An AIMessage (tool call)
• A ToolMessage (tool response) ❌ But no span for the final assistant answer.

thanks! just to give you some more context here’s what I got from pulling the spans via px.Client().query_spans it doesn’t have the last AIMessage as a span that’s available in the response.

[arizedatngo]

[arizedatngo]

thanks! just to give you some more context here’s what I got from pulling the spans via px.Client().query_spans it doesn’t have the last AIMessage as a span that’s available in the response.

sean_lee.txt

[mikeldking]

Let's add this to triage - @caroger

[satyadevai]

I haven't hered from @arizedatngo or @sean_lee in slack. I am closing this ticket for now. feel free to reopen this ticket if required any workaround.