[How to add thread-level persistence to a subgraph](https://langchain-ai.github.io/langgraph/how-tos/subgraph-persistence): LLM should read this page when implementing persistence in LangGraph with subgraphs, understanding thread-level persistence, or troubleshooting state management across graph hierarchies. This page explains how to add thread-level persistence to graphs with subgraphs in LangGraph, demonstrates propagating a checkpointer from parent to child graphs, and shows how to access and inspect persisted state across both parent and subgraph components.

