How To Build A Stateful Agent With Langgraph

Mental model

Because the state is explicit, LangGraph can checkpoint it, resume after a crash, retry a node, and branch — things a sequential crew can’t express cleanly.

Step 1 — Install

That’s a working LangGraph agent. Linear, but it’s the shape everything else builds on.

Step 2 — Define the state

The power of LangGraph is conditional routing. Say you only want to call the answer node if you got at least one note.

Step 3 — Define two nodes

The killer feature. Add a checkpointer and the graph can pause, restart, and be inspected at any node.

Step 4 — Wire the graph

Step 5 — Run it

Step 6 — Add a conditional edge

Step 7 — Persist state (checkpointing)

Step 8 — Safety rails

When NOT to use LangGraph