I am trying to build a Langgraph agent consisted of multiple request and receive/validate nodes. The request nodes will ask a question, and receive/validate nodes will receive the human input and validate if it is a valid response.

To receive the human input and validate it, the logic is to update the corresponding key-value pair in Langgraph state, and send it for validation.

The mock graph below shows the logic, enter image description here

where the state gets updated with a human input after 'request_name' node has been executed and it continues to the 'receive_name' node in the graph. I can see that graph state has been updated with the name provided by the user after manual state update, i.e, after this line

 graph.update_state(config=thread, values={requested_item: user_response}, as_node=node_name)

but when it reaches 'receive_name' node, the 'name' in the state is still None. why does the updated state not reach to the 'receive_name' node? Or how can I implement this in a more efficient way?

Here is the code.

from langgraph.graph import StateGraph, START, END
from langgraph.types import Command, interrupt
from langgraph.checkpoint.memory import MemorySaver
from langgraph.graph.message import add_messages
from typing import TypedDict, Annotated
from IPython.display import Image, display
from langchain_core.messages import AIMessage
from langchain_core.runnables.graph import MermaidDrawMethod


class State(TypedDict):
    requested_item: str
    name: str
    id: str
    name_validation: bool
    id_validation: bool
    messages: Annotated[list, add_messages]


def request_name(state):
    print('---request_name---')
    # state['requested_item'] = 'name'
    return {'messages': [AIMessage(content='Please provide a name.')],
            'requested_item': 'name'}


def receive_name(state):
    print("---receive_name---")
    user_response = state['name']

    state['name_validation'] = validate_name(user_response)
    return state


def request_id(state):
    print("---request_id ---")
    # state['requested_item'] = 'id'
    return {'messages': [AIMessage(content='Please provide an ID.')],
            'requested_item': 'id'}


def receive_id(state):
    print('---receive_id---')
    user_response = state['id']

    state['id_validation'] = validate_id(user_response)
    return state


def validate_name(name):
    names = ['xxx', 'yyy', 'zzz']
    if name in names:
        return True
    else:
        return False


def validate_id(id):
    ids = ['111', '222', '333']
    if id in ids:
        return True
    else:
        return False


builder = StateGraph(State)
builder.add_node("request_name", request_name)
builder.add_node("receive_name", receive_name)
builder.add_node("request_id", request_id)
builder.add_node("receive_id", receive_id)
builder.add_edge(START, "request_name")
builder.add_edge("request_name", "receive_name")
builder.add_conditional_edges(
    'receive_name',
    receive_name,
    {True: 'request_id',
     False: 'request_name'}
)
builder.add_edge("request_id", "receive_name")
builder.add_conditional_edges(
    'receive_id',
    receive_id,
    {True: END,
     False: 'request_id'}
)


# Set up memory
memory = MemorySaver()

# Add
graph = builderpile(checkpointer=memory)

# View
display(Image(graph.get_graph().draw_mermaid_png()))
graph_image_path = ('graph_test.png')
display(Image(graph.get_graph().draw_mermaid_png(draw_method=MermaidDrawMethod.API,
                                                 output_file_path=graph_image_path)))


# Input
initial_input = {"requested_item": "",
                 "name": None,
                 "id": None}

# Thread
thread = {"configurable": {"thread_id": "1"}}

for event in graph.stream(initial_input, thread):
    node_name = list(event.keys())[0]
    print(node_name)
    if 'request' in node_name:
        for value in event.values():
            requested_item = value['requested_item']
            user_response = input(value["messages"][-1].content + ':')
            graph.update_state(config=thread, values={requested_item: user_response}, as_node=node_name)

    else:
        for value in event.values():
            if value["messages"][-1].type == 'ai':
                print(value["messages"][-1].content)

By the way, I also tried to implement this using human-in-the-loop concept with 'interrupt()' function, but the problem is that the graph resumes from the first node every time after it receives a human input. So, the later nodes in the graph didn't get executed at all.