What State Represents

The State is the single source of truth for your agent. It is a shared dictionary (or object) that all nodes can access.

The Schema

You define the schema upfront using Python's TypedDict.

from typing import TypedDict, List

class AgentState(TypedDict):
    # The chat history
    messages: List[str]
    # Internal thought process
    current_plan: str
    # Results from API calls
    tools_output: dict
    # User metadata
    user_info: dict

Global vs Local

In LangGraph, State is Global to the execution run.

• If Node A writes to user_info, Node Z (running 10 steps later) can read it.
• You don't need to pass arguments function-to-function. You just update the shared state.

This mimics how human memory works during a task. We hold the context in our "working memory" while we perform different actions.