DOC: <How to implement human in loop for updating information from one state to second state.>

[atulv24]

Issue with current documentation:

Hi, I was trying to implement human in loop concept but unable to implement. I follow the documentation but not getting desired output. I have attaching code also for review. please guide me how to implement human in loop such a way that graph flow will stop desired node then human will see the output of that node, it will update if required and then send information to next node. Next node will use that information and do remaining code,

from typing import TypedDict
from langgraph.graph import StateGraph, START, END
from langgraph.checkpoint.memory import MemorySaver
from IPython.display import Image, display

class State(TypedDict):
input: str

def step_1(state):
print("---Step 1---")
state['input'] += " from step 1"
return state

def step_2(state):
print("---Step 2---")
state['input'] += " from step 2"
return state

def step_3(state):
print("---Step 3---")
state['input'] += " from step 3"
return state

builder = StateGraph(State)
builder.add_node("step_1", step_1)
builder.add_node("step_2", step_2)
builder.add_node("step_3", step_3)
builder.add_edge(START, "step_1")
builder.add_edge("step_1", "step_2")
builder.add_edge("step_2", "step_3")
builder.add_edge("step_3", END)

Set up memory

memory = MemorySaver()

Add

graph = builder.compile(checkpointer=memory, interrupt_before=["step_3"])

View

display(Image(graph.get_graph().draw_mermaid_png()))

Input

initial_input = {"input": "hello world"}

Thread

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

Run the graph until the first interruption

current_state = initial_input
for event in graph.stream(current_state, thread, stream_mode="values"):
print(event)
current_state = event # Update the current state with the event output

Capture the output of step_2

state_after_step_2 = current_state

try:
user_edit = input(f"Edit the state after Step 2: {state_after_step_2['input']}\nYour edit: ")
except:
user_edit = state_after_step_2['input']

Update the state with the user's edit

state_after_step_2['input'] = user_edit

#Continue the graph execution with the updated state
for event in graph.stream(state_after_step_2, thread, stream_mode="values"):
print(event)
current_state = event # Update the current state with the event output

for event in graph.stream(None, thread, stream_mode="values"):

print(event)

current_state = event # Update the current state with the event output

Idea or request for content:

Please provide me doc, solution or blog where i can solve my issues.

[gbaian10]

You should use graph.update_state(.......) to update the status.

[vbarda]

yes, @atulv24 you should use .update_state -- please check out this guide https://langchain-ai.github.io/langgraph/how-tos/human_in_the_loop/time-travel/