Lab 3: Nodes The Building Blocks

Every LangGraph graph is composed of nodes. Each node receives the current state, does some work, and returns an updated state. Click each card to learn more.

🚀 See It In Action

Watch a real LangGraph-style flow run: STARTLLM NodeEND. The LLM node will stream a real response from the API.

💡 Key Takeaways

  • Nodes are functions each node takes the current state as input and returns updates to that state.
  • START and END are special they mark the entry and exit of your graph. Every graph must have them.
  • LLM nodes call the model they read messages from state, call an LLM, and write the response back to state.
  • Tool nodes execute actions when the LLM decides to use a tool, a tool node runs it and returns the result.