LangGraph4j support for AG-UI

This module provides the building blocks to expose a LangGraph4j graph as an agent compliant with the AG-UI protocol, streaming its execution as a sequence of AG-UI events (message chunks, step lifecycle, run lifecycle, errors, etc.).

Classes overview

AGUIAgent

Core interface representing an AG-UI compliant agent. Exposes a unique id() and a run(RunAgentInput) method returning a Flow.Publisher<Event> that streams the AG-UI events produced by the agent execution.

AGUIAgentBase

Abstract base implementation of AGUIAgent that bridges a LangGraph4j CompiledGraph to the AG-UI event stream. It lazily compiles the graph (via the abstract newGraph() method), builds the graph input from the incoming request (via the abstract graphInput(RunAgentInput) method), runs it either asynchronously or synchronously, and translates node/streaming outputs, errors and completion into the corresponding AG-UI events. Subclasses typically only need to implement the two abstract methods.

AGUIAgentRegistry

A simple registry (Map<String, AGUIAgent>) used to look up a registered AGUIAgent by its identifier, typically used to dispatch an incoming AG-UI run request to the appropriate agent implementation.

AGUIHook

A LangGraph4j NodeHook implementation dedicated to the AG-UI protocol. Its stepEvents() factory method returns a NodeHook.WrapCall that automatically dispatches the AG-UI StepStartedEvent before a node runs and the StepFinishedEvent after it completes successfully, without requiring manual event handling in the node's own logic.

AGUINodeOutput

A custom LangGraph4j NodeOutput implementation that acts as a bridge between LangGraph4j's output streaming and AG-UI events. It carries a list of AG-UI Events (e.g. text message events, step lifecycle events) produced by a node, which are then forwarded to the AG-UI subscriber. Instances are created through its fluent Builder (AGUINodeOutput.builder()).

AGUIRunAgentInput

A mutable, bean-style wrapper around AG-UI's RunAgentInput (thread id, run id, tools, context, messages, forwarded properties, resume, state), convenient for deserialization frameworks. It exposes toRunAgentParameters() to convert itself into an immutable RunAgentInput instance.