Deep Dive into Reducer Functions | LangGraph | LangChain

In this video, we’ll take a deep dive into Reducer Functions in LangGraph — one of the most important concepts to master if you want to build powerful, stateful LLM applications. We’ll start by understanding what reducers are, why they’re used, and how they control state updates across graph nodes. Then, we’ll move into hands-on code implementations covering: 🔹 Default state behavior – what happens when no reducer is defined 🔹 Pre-defined reducer functions – leveraging built-in LangGraph utilities 🔹 Custom reducers – defining your own logic for complex state updates 🔹 Chat message reduce…