Tutorial: LangGraph

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LangGraph^{View Repo} helps you build complex stateful applications, like chatbots or agents, using a graph-based approach. You define your application’s logic as a series of steps (Nodes) connected by transitions (Edges) in a Graph. The system manages the application’s shared state using Channels and executes the graph step-by-step with its Pregel engine, handling things like branching, interruptions, and saving progress (Checkpointing).

flowchart TD
    A0["Pregel Execution Engine"]
    A1["Graph / StateGraph"]
    A2["Channels"]
    A3["Nodes (PregelNode)"]
    A4["Checkpointer (BaseCheckpointSaver)"]
    A5["Control Flow Primitives (Branch, Send, Interrupt)"]
    A0 -- "Executes" --> A1
    A1 -- "Contains" --> A3
    A3 -- "Updates State Via" --> A2
    A0 -- "Manages State Via" --> A2
    A0 -- "Uses Checkpointer" --> A4
    A1 -- "Defines Control Flow With" --> A5
    A5 -- "Directs Execution Of" --> A0
    A4 -- "Saves State Of" --> A2

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Table of contents

• Graph & StateGraph
• Nodes (PregelNode)
• Channels
• Control Flow Primitives
• Pregel Execution Engine
• Checkpointer (BaseCheckpointSaver)