fix: Make human-in-the-loop more consistent between graph state and chat history (#550)

## Summary
This PR addresses inconsistencies between the UI display and the agent's
internal LangGraph state during the ticket booking process. Previously,
hardcoded messages spread across the UI, the backend request handlers,
and agent nodes, led to a disjointed UX where chat history, user
prompts, and agent responses could become out of sync, particularly
after a page refresh.

The core of this change is the introduction of a single, internal helper
function (__booking_handler) that centralizes the logic for both
confirming and declining a ticket booking. This refactoring ensures that
all UI components and chat history entries are a direct reflection of
the agent's state.

## Changes
* Created a common `__booking_handler` to manage both booking "accept"
and "decline" actions, eliminating code duplication and streamlining
maintenance.

* Replaced hardcoded UI text for confirmations and responses with
messages sourced directly from the agent's graph state. This guarantees
consistency between what the user sees and the agent's conversational
history.

* The user's choice (e.g., `"Looks good to me. Book it!"`) and the
agent's final response are now reliably added to the user session's chat
history for both success and decline scenarios.

* Added a crucial comment explaining the rationale for injecting the
"decline" message to the langgraph state *before* invoking the agent.

* Removed unnecessary `params` from the request handlers for better code
hygiene.

Author: anubhav756

agent/agent.py

@@ -51,18 +51,23 @@ def __init__(self):
     def user_session_exist(self, uuid: str) -> bool:
         return uuid in self._user_sessions
 
-    async def user_session_insert_ticket(self, uuid: str, params: str) -> Any:
-        response = await self.user_session_invoke(uuid, None)
-        return "ticket booking success"
+    async def user_session_insert_ticket(self, uuid: str) -> Any:
+        return await self.user_session_invoke(uuid, None)
 
     async def user_session_decline_ticket(self, uuid: str) -> dict[str, Any]:
         config = self.get_config(uuid)
+
+        # The user has declined the pending ticket booking. We inject a
+        # synthetic HumanMessage to simulate the user explicitly canceling. This
+        # state update causes langgraph to re-run its conditional logic. Instead
+        # of proceeding with the interrupted tool call, the graph routes to the
+        # main agent, which formulates a natural response to the user's
+        # "cancellation".
         human_message = HumanMessage(
             content="I changed my mind. Decline ticket booking."
         )
         self._langgraph_app.update_state(config, {"messages": [human_message]})
-        response = await self.user_session_invoke(uuid, None)
-        return response
+        return await self.user_session_invoke(uuid, None)
 
     async def user_session_create(self, session: dict[str, Any]):
         """Create and load an agent executor with tools and LLM."""

agent/react_graph.py

@@ -166,7 +166,7 @@ async def insert_ticket_node(state: UserState):
             tool_call = last_message.tool_calls[0]
             tool_args = tool_call.get("args")
             output = await insert_ticket.ainvoke(tool_args)
-            human_message = HumanMessage(content="Looks good to me.")
+            human_message = HumanMessage(content="Looks good to me. Book it!")
             ai_message = AIMessage(
                 content=(
                     "Your flight has been successfully booked."

app.py

@@ -155,56 +155,71 @@ async def chat_handler(request: Request, prompt: str = Body(embed=True)):
     output = response.get("output")
     confirmation = response.get("confirmation")
     trace = response.get("trace")
+    request.session["history"].append({"type": "ai", "data": {"content": output}})
     # Return assistant response
     if confirmation:
         return json.dumps(
-            {"type": "confirmation", "content": confirmation, "trace": trace}
+            {
+                "type": "confirmation",
+                "content": {"output": output, **confirmation},
+                "trace": trace,
+            }
         )
     else:
-        request.session["history"].append({"type": "ai", "data": {"content": output}})
         return json.dumps(
-            {"type": "message", "content": markdown(output), "trace": trace}
+            {
+                "type": "message",
+                "content": markdown(output),
+                "trace": trace,
+            }
         )
 
 
-@routes.post("/book/flight", response_class=PlainTextResponse)
-async def book_flight(request: Request, params: str = Body(embed=True)):
-    """Handler for LangChain chat requests"""
-    # Retrieve the params for the booking
-    if not params:
-        raise HTTPException(status_code=400, detail="Error: No booking params")
+async def __booking_handler(request: Request, is_confirmed: bool):
+    """Common booking handler for flight confirmation and decline"""
+    # Note in the history, that the ticket was not booked.
+    # This is helpful in case of reloads so there doesn't seem to be a break in
+    # communication.
     if "uuid" not in request.session:
         raise HTTPException(
             status_code=400, detail="Error: Invoke index handler before start chatting"
         )
     agent = request.app.state.agent
-    response = await agent.user_session_insert_ticket(request.session["uuid"], params)
-    # Note in the history, that the ticket has been successfully booked
-    request.session["history"].append(
-        {"type": "ai", "data": {"content": "Your flight has been successfully booked."}}
+    uuid = request.session["uuid"]
+
+    # Determine the correct agent action and user message based on confirmation
+    # status.
+    if is_confirmed:
+        action = agent.user_session_insert_ticket(uuid)
+        content = "Looks good to me. Book it!"
+    else:
+        action = agent.user_session_decline_ticket(uuid)
+        content = "I changed my mind. Decline ticket booking."
+
+    response = await action
+    output = response.get("output")
+    request.session["history"].extend(
+        [
+            {
+                "type": "human",
+                "data": {"content": content},
+            },
+            {"type": "ai", "data": {"content": output}},
+        ]
     )
-    return response
+    return output
+
+
+@routes.post("/book/flight", response_class=PlainTextResponse)
+async def book_flight(request: Request):
+    """Handler for booking confirmation requests"""
+    return await __booking_handler(request, is_confirmed=True)
 
 
 @routes.post("/book/flight/decline", response_class=PlainTextResponse)
 async def decline_flight(request: Request):
-    """Handler for LangChain chat requests"""
-    # Note in the history, that the ticket was not booked
-    # This is helpful in case of reloads so there doesn't seem to be a break in communication.
-    agent = request.app.state.agent
-    response = await agent.user_session_decline_ticket(request.session["uuid"])
-    response = response["output"]
-    request.session["history"].append(
-        {"type": "ai", "data": {"content": "Please confirm if you would like to book."}}
-    )
-    request.session["history"].append(
-        {
-            "type": "human",
-            "data": {"content": "I changed my mind. Decline ticket booking."},
-        }
-    )
-    request.session["history"].append({"type": "ai", "data": {"content": response}})
-    return response
+    """Handler for booking decline requests"""
+    return await __booking_handler(request, is_confirmed=False)
 
 
 @routes.post("/reset")

static/index.js

@@ -156,6 +156,7 @@ function logMessage(name, msg, trace) {
 function buildConfirmation(confirmation, messageId) {
     if (["Insert Ticket","insert_ticket"].includes(confirmation.tool)) {
         const params = confirmation.params;
+        const output = confirmation.output;
         const message_id = messageId;
         confirmations[message_id] = params
         const from = params.departure_airport;
@@ -169,7 +170,7 @@ function buildConfirmation(confirmation, messageId) {
         const message = `<div class="chat-bubble ai" id="${message_id}">
         <div class="sender-icon"><img src="static/logo.png"></div>
         <div class="ticket-confirmation">
-            Please confirm the details below to complete your booking
+            ${output}
             <div class="ticket-header"></div>
             <div class="ticket">
                 <div class="from">${from}</div>
@@ -181,7 +182,7 @@ function buildConfirmation(confirmation, messageId) {
             ${buildBox('left', 205, 35, 15, "Flight", flight)}
             ${buildBox('left', 265, 35, 15, "Passenger", userName, "")}
             ${buildButton("Looks good to me. Book it!", 342, "#805e9d", "#FFF", "confirmTicket" + message_id)}
-            ${buildButton("I changed my mind.", 395, "#f8f8f8", "#181a23", "cancelTicket" + message_id)}
+            ${buildButton("I changed my mind. Decline ticket booking.", 395, "#f8f8f8", "#181a23", "cancelTicket" + message_id)}
         </div></div>`;
         $('.inner-content').append(message);
         $('.chat-content').scrollTop($('.chat-content').prop("scrollHeight"));
@@ -262,7 +263,7 @@ async function cancelTicket(id) {
             'Content-Type': 'application/json'
         }
     });
-    logMessage("human", "I changed my mind.")
+    logMessage("human", "I changed my mind. Decline ticket booking.")
     removeTicketChoices(id);
 
     if (response.ok) {
@@ -274,7 +275,7 @@ async function cancelTicket(id) {
 }
 
 async function confirmTicket(id) {
-    logMessage("human", "Looks good to me.")
+    logMessage("human", "Looks good to me. Book it!")
     const params = JSON.stringify(confirmations[id]);
     const response = await fetch('book/flight', {
         method: 'POST',