# LangChain — Build LLM-Powered Applications

> The most popular framework for building applications with large language models. Chains, agents, RAG, memory, tool use, and integrations with 700+ providers.

## Install

Save as a script file and run:

## Quick Use

```bash
pip install langchain langchain-openai langchain-anthropic
```

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## Intro

LangChain is the standard framework for building LLM-powered applications. Compose chains of prompts, connect to vector stores for RAG, build autonomous agents, and integrate with hundreds of tools and providers.

**Best for**: Chatbots, RAG pipelines, autonomous agents, document Q&A, data extraction
**Works with**: OpenAI, Anthropic, Google, Ollama, HuggingFace, and 700+ integrations

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## Core Concepts

### Chains
Compose multiple LLM calls and transformations into a pipeline:
```python
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)
```python
from langchain_community.vectorstores import FAISS
from langchain_openai import OpenAIEmbeddings

vectorstore = FAISS.from_documents(docs, OpenAIEmbeddings())
retriever = vectorstore.as_retriever()
```

### Agents
```python
from langchain.agents import create_tool_calling_agent
agent = create_tool_calling_agent(llm, tools, prompt)
```

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## Ecosystem

- **LangSmith** — Observability and testing platform
- **LangGraph** — Stateful multi-actor agent framework
- **LangServe** — Deploy chains as REST APIs

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### FAQ

**Q: What is LangChain?**
A: The most popular framework for building applications with large language models. Chains, agents, RAG, memory, tool use, and integrations with 700+ providers.

**Q: How do I install LangChain?**
A: Check the Quick Use section above for step-by-step installation instructions. Most assets can be set up in under 2 minutes.

## Source & Thanks

> Created by [LangChain](https://github.com/langchain-ai). Licensed under MIT.
> [langchain-ai/langchain](https://github.com/langchain-ai/langchain) — 100K+ GitHub stars

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Source: https://tokrepo.com/en/workflows/803c3d1a-a47e-474d-8b6c-ea7965f5d00c
Author: Script Depot