# Graph state

Data shared by every step in the graph, most often the messages array plus a few fields of your own.

AI developers · Part 06: LangChain / LangGraph · Card 8 of 14 · Last updated 2026-10-13

## Analogy

The Redux store. Nodes read it, return updates, and the graph merges them in.

## In an agent

State is what gets checkpointed, so it's what lets an agent pause and resume.

## Practice

### Flashcards

- **Interview: what does LangGraph add to LangChain?** Explicit graphs with state, checkpoints, interrupts and routing, so complex agents are easier to control.

## Questions people ask

### What is state in LangGraph?

State is the data every node in the graph can read, most often the messages array plus a few fields of your own, such as the current route or a draft. A node returns updates, and LangGraph merges them into the state. It works much like a Redux store with reducers.

### Why does graph state matter for pausing and resuming agents?

Because the state is what gets saved. A checkpointer stores the full state after every step, so the agent can stop, for example to wait for approval or after a crash, and continue later from exactly the same point. Anything kept outside the state would be lost when the run pauses.

## Related concepts

- [LangGraph.js](https://studyvisually.com/learn/tech/ai-developers/langchain-langgraph/langgraph)
- [Conditional edges](https://studyvisually.com/learn/tech/ai-developers/langchain-langgraph/conditional-edges)
- [Checkpointing](https://studyvisually.com/learn/tech/ai-developers/langchain-langgraph/checkpointing)
- [interrupt()](https://studyvisually.com/learn/tech/ai-developers/langchain-langgraph/interrupt)

Web page: https://studyvisually.com/learn/tech/ai-developers/langchain-langgraph/graph-state
Study this card in the app: https://studyvisually.com/app/learn?category=ai-developers&card=graph-state