Google Vertex AI

caution

You are currently on a page documenting the use of Google Vertex models as text completion models. Many popular models available on Google Vertex are chat completion models.

You may be looking for this page instead.

LangChain.js supports two different authentication methods based on whether you’re running in a Node.js environment or a web environment.

This will help you get started with VertexAI completion models (LLMs) using LangChain. For detailed documentation on VertexAI features and configuration options, please refer to the API reference.

Overview

Integration details

Class	Package	Local	Serializable	PY support	Package downloads	Package latest
VertexAI	@langchain/google-vertexai	❌	✅	✅

Setup

To access VertexAI models you’ll need to create a Google Cloud Platform (GCP) account, get an API key, and install the @langchain/google-vertexai integration package.

Credentials

Node.js

You should make sure the Vertex AI API is enabled for the relevant project and that you’ve authenticated to Google Cloud using one of these methods:

• You are logged into an account (using gcloud auth application-default login) permitted to that project.
• You are running on a machine using a service account that is permitted to the project.
• You have downloaded the credentials for a service account that is permitted to the project and set the GOOGLE_APPLICATION_CREDENTIALS environment variable to the path of this file. or
• You set the GOOGLE_API_KEY environment variable to the API key for the project.

Web

To call Vertex AI models in web environments (like Edge functions), you’ll need to install the @langchain/google-vertexai-web package.

Then, you’ll need to add your service account credentials directly as a GOOGLE_VERTEX_AI_WEB_CREDENTIALS environment variable:

GOOGLE_VERTEX_AI_WEB_CREDENTIALS={"type":"service_account","project_id":"YOUR_PROJECT-12345",...}

You can also pass your credentials directly in code like this:

import { VertexAI } from "@langchain/google-vertexai";
// Or uncomment this line if you're using the web version:
// import { VertexAI } from "@langchain/google-vertexai-web";

const model = new VertexAI({
  authOptions: {
    credentials: {"type":"service_account","project_id":"YOUR_PROJECT-12345",...},
  },
});

If you want to get automated tracing of your model calls you can also set your LangSmith API key by uncommenting below:

# export LANGCHAIN_TRACING_V2="true"
# export LANGCHAIN_API_KEY="your-api-key"

Installation

The LangChain VertexAI integration lives in the @langchain/google-vertexai package:

tip

See this section for general instructions on installing integration packages.

npm

npm i @langchain/google-vertexai

yarn

yarn add @langchain/google-vertexai

pnpm

pnpm add @langchain/google-vertexai

or for web environments:

npm

npm i @langchain/google-vertexai-web

yarn

yarn add @langchain/google-vertexai-web

pnpm

pnpm add @langchain/google-vertexai-web

Instantiation

Now we can instantiate our model object and generate chat completions:

import { VertexAI } from "@langchain/google-vertexai-web";

const llm = new VertexAI({
  model: "gemini-pro",
  temperature: 0,
  maxRetries: 2,
  // other params...
});

Invocation

const inputText = "VertexAI is an AI company that ";

const completion = await llm.invoke(inputText);
completion;

offers a wide range of cloud computing services and artificial intelligence solutions to businesses and developers worldwide.

Chaining

We can chain our completion model with a prompt template like so:

import { PromptTemplate } from "@langchain/core/prompts";

const prompt = PromptTemplate.fromTemplate(
  "How to say {input} in {output_language}:\n"
);

const chain = prompt.pipe(llm);
await chain.invoke({
  output_language: "German",
  input: "I love programming.",
});

"Ich liebe Programmieren."
Pronunciation guide:

Ich: [ɪç] (similar to "ikh" with a soft "ch" sound)
liebe: [ˈliːbə] (LEE-buh)
Programmieren: [pʁoɡʁaˈmiːʁən] (pro-gra-MEE-ren)

You could also say:
"Ich liebe es zu programmieren."
Which translates more literally to "I love to program." This version is a bit more formal or precise.
Pronunciation:

es: [ɛs] (like the letter "S")
zu: [tsuː] (tsoo)

Both versions are correct and commonly used.

API reference

For detailed documentation of all VertexAI features and configurations head to the API reference: https://api.js.langchain.com/classes/langchain_google_vertexai.VertexAI.html