Core Concepts
Chains
Compose multiple LLM calls and transformations into a pipeline:
from langchain_openai import ChatOpenAI
from langchain_core.prompts import ChatPromptTemplate
chain = ChatPromptTemplate.from_template("Summarize: {text}") | ChatOpenAI()
result = chain.invoke({"text": "..."})RAG (Retrieval-Augmented Generation)
from langchain_community.vectorstores import FAISS
from langchain_openai import OpenAIEmbeddings
vectorstore = FAISS.from_documents(docs, OpenAIEmbeddings())
retriever = vectorstore.as_retriever()Agents
from langchain.agents import create_tool_calling_agent
agent = create_tool_calling_agent(llm, tools, prompt)Ecosystem
- LangSmith — Observability and testing platform
- LangGraph — Stateful multi-actor agent framework
- LangServe — Deploy chains as REST APIs