17-lc02-chatbot.qmd

---
title: "LangChain 02 -- Build a Chatbot with LangChain"
---

## Introduction

[![](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/trgardos/ml-549-fa24/blob/main/src/langchain/02-langchain-chatbot.ipynb)

[Previously](16-lc01-simple-llm-app.qmd), we:

- Used a language model
- Used prompt templates and output parsers
- Started using LangChain Expression Language (LCEL) to chain components together
- Logged interactions with LangSmith
- Wrote a simple client/server application using LangServe

For this example, we'll build a simple chatbot application programmatically.

We'll explore the following features:

- Message persistance using LangGraph
- Chat thread configuration
- Prompt templates
- Trimming conversation history
- Streaming