Refactor session state handling

Changed to generate session state on the server side.

Author: fujita-h

app/backend/app.py

@@ -80,6 +80,7 @@
     CONFIG_VECTOR_SEARCH_ENABLED,
 )
 from core.authentication import AuthenticationHelper
+from core.sessionhelper import create_session_id
 from decorators import authenticated, authenticated_path
 from error import error_dict, error_response
 from prepdocs import (
@@ -219,10 +220,15 @@ async def chat(auth_claims: Dict[str, Any]):
         else:
             approach = cast(Approach, current_app.config[CONFIG_CHAT_APPROACH])
 
+        # If session state is provided, persists the session state,
+        # else creates a new session_id depending on the chat history options enabled.
+        session_state = request_json.get("session_state")
+        if session_state is None:
+            session_state = create_session_id(current_app.config[CONFIG_CHAT_HISTORY_BROWSER_ENABLED])
         result = await approach.run(
             request_json["messages"],
             context=context,
-            session_state=request_json.get("session_state"),
+            session_state=session_state,
         )
         return jsonify(result)
     except Exception as error:
@@ -245,10 +251,15 @@ async def chat_stream(auth_claims: Dict[str, Any]):
         else:
             approach = cast(Approach, current_app.config[CONFIG_CHAT_APPROACH])
 
+        # If session state is provided, persists the session state,
+        # else creates a new session_id depending on the chat history options enabled.
+        session_state = request_json.get("session_state")
+        if session_state is None:
+            session_state = create_session_id(current_app.config[CONFIG_CHAT_HISTORY_BROWSER_ENABLED])
         result = await approach.run_stream(
             request_json["messages"],
             context=context,
-            session_state=request_json.get("session_state"),
+            session_state=session_state,
         )
         response = await make_response(format_as_ndjson(result))
         response.timeout = None  # type: ignore

app/backend/core/sessionhelper.py

@@ -0,0 +1,7 @@
+import uuid
+
+
+def create_session_id(config_chat_history_browser_enabled: bool) -> str | None:
+    if config_chat_history_browser_enabled:
+        return str(uuid.uuid4())
+    return None

app/frontend/src/pages/chat/Chat.tsx

@@ -203,8 +203,7 @@ const Chat = () => {
                     }
                 },
                 // AI Chat Protocol: Client must pass on any session state received from the server
-                // Set new UUID as session state for the first request
-                session_state: answers.length ? answers[answers.length - 1][1].session_state : crypto.randomUUID()
+                session_state: answers.length ? answers[answers.length - 1][1].session_state : null
             };
 
             const response = await chatApi(request, shouldStream, token);
@@ -217,14 +216,18 @@ const Chat = () => {
             if (shouldStream) {
                 const parsedResponse: ChatAppResponse = await handleAsyncRequest(question, answers, response.body);
                 setAnswers([...answers, [question, parsedResponse]]);
-                historyManager.addItem(parsedResponse.session_state, [...answers, [question, parsedResponse]]);
+                if (typeof parsedResponse.session_state === "string" && parsedResponse.session_state !== "") {
+                    historyManager.addItem(parsedResponse.session_state, [...answers, [question, parsedResponse]]);
+                }
             } else {
                 const parsedResponse: ChatAppResponseOrError = await response.json();
                 if (parsedResponse.error) {
                     throw Error(parsedResponse.error);
                 }
                 setAnswers([...answers, [question, parsedResponse as ChatAppResponse]]);
-                historyManager.addItem(parsedResponse.session_state, [...answers, [question, parsedResponse as ChatAppResponse]]);
+                if (typeof parsedResponse.session_state === "string" && parsedResponse.session_state !== "") {
+                    historyManager.addItem(parsedResponse.session_state, [...answers, [question, parsedResponse as ChatAppResponse]]);
+                }
             }
             setSpeechUrls([...speechUrls, null]);
         } catch (e) {