How to use the python LangChainInstrumentor to trace LangChain
Phoenix has first-class support for LangChain applications.
pip install openinference-instrumentation-langchain langchain_openaiUse the register function to connect your application to Phoenix:
from phoenix.otel import register
# configure the Phoenix tracer
tracer_provider = register(
project_name="my-llm-app", # Default is 'default'
auto_instrument=True # Auto-instrument your app based on installed OI dependencies
)By instrumenting LangChain, spans will be created whenever a chain is run and will be sent to the Phoenix server for collection.
from langchain_core.prompts import ChatPromptTemplate
from langchain_openai import ChatOpenAI
prompt = ChatPromptTemplate.from_template("{x} {y} {z}?").partial(x="why is", z="blue")
chain = prompt | ChatOpenAI(model_name="gpt-3.5-turbo")
chain.invoke(dict(y="sky"))Now that you have tracing setup, all invocations of chains will be streamed to your running Phoenix for observability and evaluation.
Sign up for Phoenix:
Sign up for an Arize Phoenix account at https://app.phoenix.arize.com/login
Click Create Space, then follow the prompts to create and launch your space.
Install packages:
pip install arize-phoenix-otelSet your Phoenix endpoint and API Key:
From your new Phoenix Space
Create your API key from the Settings page
Copy your Hostname from the Settings page
In your code, set your endpoint and API key:
import os
os.environ["PHOENIX_API_KEY"] = "ADD YOUR PHOENIX API KEY"
os.environ["PHOENIX_COLLECTOR_ENDPOINT"] = "ADD YOUR PHOENIX HOSTNAME"
# If you created your Phoenix Cloud instance before June 24th, 2025,
# you also need to set the API key as a header:
# os.environ["PHOENIX_CLIENT_HEADERS"] = f"api_key={os.getenv('PHOENIX_API_KEY')}"Launch your local Phoenix instance:
pip install arize-phoenix
phoenix serveFor details on customizing a local terminal deployment, see Terminal Setup.
Install packages:
pip install arize-phoenix-otelSet your Phoenix endpoint:
import os
os.environ["PHOENIX_COLLECTOR_ENDPOINT"] = "http://localhost:6006"See Terminal for more details.
Pull latest Phoenix image from Docker Hub:
docker pull arizephoenix/phoenix:latestRun your containerized instance:
docker run -p 6006:6006 arizephoenix/phoenix:latestThis will expose the Phoenix on localhost:6006
Install packages:
pip install arize-phoenix-otelSet your Phoenix endpoint:
import os
os.environ["PHOENIX_COLLECTOR_ENDPOINT"] = "http://localhost:6006"For more info on using Phoenix with Docker, see Docker.
Install packages:
pip install arize-phoenixLaunch Phoenix:
import phoenix as px
px.launch_app()