WhatsApp Bot — Baileys + LangChain

A real WhatsApp bot: the same LangChain + Groq pieces from the Session 6 LangChain lesson, now answering real messages. Baileys links to WhatsApp the same way WhatsApp Web does — scan a QR code once, no official business API or paid account needed.

Setup (one time)

Needs Node.js 20 or newer — check with node -v.

npm install

1. Copy .env.example to .env
2. Paste your Groq API key inside .env (same key used in the LangChain session)

Run it

npm start

1. A QR code prints in the terminal.
2. On your phone: WhatsApp → Settings → Linked Devices → Link a Device → scan it.
3. Message the bot from any other WhatsApp number/chat — it replies using Llama 3.3 via Groq.

Your login is saved in auth_info_baileys/ after the first scan, so you won't need to scan again unless you delete that folder or unlink the device from your phone.

How it works

Piece	What it does	Session 6 callback
baileys	Connects to WhatsApp as a linked device; fires connection.update (QR, connect/disconnect) and messages.upsert (incoming messages)	new — not covered in the LangChain session
ChatGroq	Same model class, same llama-3.3-70b-versatile	FILE 00
ChatPromptTemplate + .pipe()	Same chain idea as FILE 02's prompt | llm | parser — JavaScript can't overload |, so LangChain.js uses .pipe() instead. Same Runnable concept, different syntax	FILE 02
StrOutputParser	Plain string out, no digging into .content	FILE 02

Every incoming text message runs through the chain and the reply is sent straight back. No memory between messages (stateless) — that keeps this first version simple. To make it remember each conversation, add FILE 04's RunnableWithMessageHistory pattern, keyed by the sender's remoteJid instead of a made-up session id.

Notes / things that can go wrong

• Groq 429 (rate limit): same free-tier limit as the LangChain session. The bot catches this and sends a fallback reply instead of crashing — wait a bit and try again.
• Group chats and Status updates are ignored on purpose — this bot only replies in 1:1 chats, so it won't spam a group during the demo.
• "Logged out" after closing: if you unlink the device from your phone, delete the auth_info_baileys/ folder and run npm start again for a fresh QR code.
• Baileys is an unofficial WhatsApp Web client (not the official WhatsApp Business API) — great for learning and demos, but keep test traffic light. Don't use it for bulk messaging or spam; WhatsApp can ban the number.