Installation and setup

One pip install brings the framework, its core types and the runtime under its agents. Provider packages come later, when a hosted model replaces the one you write.

langchain 1.4.2

The langchain package brings langchain-core, which holds the message types and the base classes every model builds on, and langgraph, which runs the agent loop.

pip install "langchain==1.4.2"

Check which version Python finds:

from importlib.metadata import version

print(version("langchain"))
print(version("langchain-core"))

Lessons 26 and 29 install what they need when they need it: a text splitter, numpy and MCP support.

Keys, for when you want a hosted modelOptional

Every lesson runs on a stand-in model you write in lesson 3. To use a hosted model instead, install its provider package and set its key as an environment variable. Lesson 33 makes the switch with init_chat_model.

pip install "langchain-groq==1.1.3"

export GROQ_API_KEY=gsk_...