LangChain Install & Auth

Overview

Set up LangChain SDK and configure LLM provider authentication credentials.

Prerequisites

• Python 3.9+ or Node.js 18+

• Package manager (pip, poetry, or npm)

• LLM provider account (OpenAI, Anthropic, Google, etc.)

• API key from your LLM provider dashboard

Instructions

Step 1: Install LangChain Core

set -euo pipefail

Python (recommended)

pip install langchain langchain-core langchain-community

Or with specific providers

pip install langchain-openai langchain-anthropic langchain-google-genai

Node.js

npm install langchain @langchain/core @langchain/community

Step 2: Configure Authentication

OpenAI

export OPENAI_API_KEY="your-openai-key"

Anthropic

export ANTHROPIC_API_KEY="your-anthropic-key"

Google

export GOOGLE_API_KEY="your-google-key"

Or create .env file

echo 'OPENAI_API_KEY=your-openai-key' >> .env

Step 3: Verify Connection

from langchain_openai import ChatOpenAI

llm = ChatOpenAI(model="gpt-4o-mini") response = llm.invoke("Say hello!") print(response.content)

Output

• Installed LangChain packages in virtual environment

• Environment variables or .env file with API keys

• Successful connection verification output

Error Handling

Error Cause Solution

Invalid API Key Incorrect or expired key Verify key in provider dashboard

Rate Limited Exceeded quota Check quota limits, implement backoff

Network Error Firewall blocking Ensure outbound HTTPS allowed

Module Not Found Installation failed Run pip install again, check Python version

Provider Error Service unavailable Check provider status page

Examples

Python Setup (OpenAI)

import os from langchain_openai import ChatOpenAI

Ensure API key is set

assert os.environ.get("OPENAI_API_KEY"), "Set OPENAI_API_KEY"

llm = ChatOpenAI( model="gpt-4o-mini", temperature=0.7, max_tokens=1000 # 1000: 1 second in ms )

Python Setup (Anthropic)

from langchain_anthropic import ChatAnthropic

llm = ChatAnthropic( model="claude-3-5-sonnet-20241022", # 20241022 = date/version stamp temperature=0.7 )

TypeScript Setup

import { ChatOpenAI } from "@langchain/openai";

const llm = new ChatOpenAI({ modelName: "gpt-4o-mini", temperature: 0.7 });

Resources

• LangChain Documentation

• LangChain JS/TS

• OpenAI API Keys

• Anthropic Console

Next Steps

After successful auth, proceed to langchain-hello-world for your first chain.