@braintrust/langchain-js

SDK for integrating Braintrust with LangChain.js. This package provides a callback handler to automatically log LangChain.js executions to Braintrust.

Installation

npm install @braintrust/langchain-js
# or
yarn add @braintrust/langchain-js
# or
pnpm add @braintrust/langchain-js

Requirements

• Node.js >= 16
• LangChain.js >= 0.3.0

Usage

First, make sure you have your Braintrust API key set in your environment:

export BRAINTRUST_API_KEY="your-api-key"

Basic Usage

import { ChatOpenAI } from "@langchain/openai";
import {
  BraintrustCallbackHandler,
  setGlobalHandler,
} from "@braintrust/langchain-js";

// Create the callback handler (optionally pass in a custom logger)
const handler = new BraintrustCallbackHandler();

// Set the handler for all LangChain components
setGlobalHandler(handler);

// Use LangChain as normal - all calls will be logged to Braintrust
const response = await model.invoke("Tell me a joke about bears");

If you'd like to pass the callback handler to specific LangChain calls, you can do so by passing the handler to the callbacks option.

import { ChatOpenAI } from "@langchain/openai";
import { BraintrustCallbackHandler } from "@braintrust/langchain-js";

// Create the callback handler (optionally pass in a custom logger)
const handler = new BraintrustCallbackHandler();

// Initialize your LangChain components with the handler
const model = new ChatOpenAI({
  callbacks: [handler],
});

// Use LangChain as normal - all calls will be logged to Braintrust
const response = await model.invoke("Tell me a joke about bears", {
  callbacks: [handler],
});

Supported Features

The callback handler supports logging for:

• LLM calls (including streaming)
• Chat model interactions
• Chain executions
• Tool/Agent usage
• Memory operations
• State management (LangGraph)

Review the LangChain.js documentation for more information on how to use callbacks.

Development

Contributions are welcomed!

git clone https://github.com/braintrustdata/sdk.git

cd sdk/integrations/langchain-js

pnpm install

# work on the code

pnpm test
pnpm build