(LangGraph integration) Human-in-the-loop not used for AG-UI tools

[ltoniazzi]

Working on this issue I noticed that AG-UI payload Tools do not exploit the Human-in-the-loop feature of LangGraph (which is a faeture already supported by the ag-ui integration).

Current implementation

It seems that currently (as the official example also suggests):

• the graph is supposed to return a placeholder tool response message (so it fires-and-forgets the tool calls)
• the ag-ui payload will include later the response and that redacts the content of the placeholder tool response message (so called orphaned tools).

Suggested implementation

But I am wondering why the design does not use the LangGraph Human-in-the-loop feature.
So the flow could be:

• the graph interrupts the tool execution
• an ag-ui payload sends the tool response, resuming the execution.

Question

It feels to me that using HITL is the natural way to handle tools from the AG-UI payload, so I'm wondering if someone can help me understand this design decision?

(One could build a middleware that binds tools at runtime and perform the interrupt for AG-UI tools)

[ltoniazzi]

Partial answer after looking at this course.

To link-up to CopilotKit:

1. Use the copilotkit middleware in create_agent (manages FE tools, injection and calls (by removing the call before a node is created to execute it, and placing it back at the end, I think, which in case it's a it odd, as the tool loop will think it did not call the tool!?))

graph = create_agent(
        model=_model,
        middleware=[CopilotKitMiddleware()],
    )

2. And use LangGraphAGUIAgent (that inherits from LangGraphAgent):

agent = LangGraphAGUIAgent(
     graph=graph,
)
add_langgraph_fastapi_endpoint(app=app, agent=agent, path="/")