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The VertexAI SDK can be instrumented using the openinference-instrumentation-vertexai package.

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Launch Phoenix

  • Phoenix Cloud
  • Command Line
  • Docker
  • Notebook
Sign up for Phoenix:
  1. Sign up for an Arize Phoenix account at https://app.phoenix.arize.com/login
  2. Click Create Space, then follow the prompts to create and launch your space.
Install packages:
pip install arize-phoenix-otel
Set your Phoenix endpoint and API Key:From your new Phoenix Space
  1. Create your API key from the Settings page
  2. Copy your Hostname from the Settings page
  3. 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')}"
Having trouble finding your endpoint? Check out Finding your Phoenix Endpoint

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Install

pip install openinference-instrumentation-vertexai vertexai

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Setup

See Google’s guide on setting up your environment for the Google Cloud AI Platform. You can also store your Project ID in the CLOUD_ML_PROJECT_ID environment variable. Use 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
)

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Run VertexAI

import vertexai
from vertexai.generative_models import GenerativeModel

vertexai.init(location="us-central1")
model = GenerativeModel("gemini-1.5-flash")

print(model.generate_content("Why is sky blue?").text)

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Observe

Now that you have tracing setup, all invocations of Vertex models will be streamed to your running Phoenix for observability and evaluation.

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Resources