How to Use Ollama with LangChain
A complete guide to using Ollama as the LangChain backend: installing langchain-ollama, using OllamaLLM and ChatOllama with system and human messages, building LCEL chains with prompt templates and StrOutputParser, a full RAG pipeline using OllamaEmbeddings with nomic-embed-text and Chroma vectorstore, adding conversation memory with InMemoryChatMessageHistory and RunnableWithMessageHistory, and creating a tool-using ReAct agent with LangGraph.