LangGraph Foundations
Core concepts — graphs, nodes, edges, and state management.
Edges and Routing
Edges define execution flow between nodes — static edges for fixed paths, conditional edges for dynamic routing based on state, and parallel edges for concurrent fan-out execution.
Graph Compilation
Calling builder.compile() validates the graph structure, resolves all edges and nodes, and returns a frozen, executable CompiledGraph object that supports invoke, stream, and async execution.
Nodes
Nodes are Python functions that receive the current graph state, perform a unit of work, and return a partial state update dict — they are the computational building blocks of every LangGraph application.
State and State Schema
State is a typed, shared data structure that flows through every node in a LangGraph graph, with reducers controlling how concurrent or sequential updates are merged.
The Command API
The Command object lets a node simultaneously update state and control routing in a single return value, replacing the need for separate conditional edges in many scenarios.
What Is LangGraph
LangGraph is a low-level orchestration framework that models AI agent logic as a directed graph of nodes, edges, and shared state.