LangChain Common Errors

Overview

Quick reference for the most frequent LangChain errors with exact error messages, root causes, and copy-paste fixes.

Import Errors

Cannot find module '@langchain/openai'

# Provider package not installed
npm install @langchain/openai
# Also: @langchain/anthropic, @langchain/google-genai, @langchain/community

Cannot import name 'ChatOpenAI' from 'langchain' (Python)