diff --git a/ufo/agent/agent.py b/ufo/agent/agent.py
index 37992662..32793605 100644
--- a/ufo/agent/agent.py
+++ b/ufo/agent/agent.py
@@ -83,7 +83,7 @@ def __init__(
         self.experience_retriever = None
         self.human_demonstration_retriever = None
         self.Puppeteer = self.create_puppteer_interface()
-        self.host = None
+        self._host = None
 
     def get_prompter(
         self,
@@ -295,14 +295,14 @@ def set_host(self, host: HostAgent) -> None:
         Set the host agent.
         :param host: The host agent.
         """
-        self.host = host
+        self._host = host
 
     def get_host(self) -> HostAgent:
         """
         Get the host agent that manages the AppAgent.
         :return: The host agent.
         """
-        return self.host
+        return self._host
 
     def build_offline_docs_retriever(self) -> None:
         """
diff --git a/ufo/module/basic.py b/ufo/module/basic.py
index 74c706e3..4fe575e5 100644
--- a/ufo/module/basic.py
+++ b/ufo/module/basic.py
@@ -31,7 +31,6 @@
     ErrorState,
     MaxStepReachedState,
     NoneState,
-    SessionFinishState,
     StatusToStateMapper,
 )
 
@@ -436,7 +435,7 @@ def is_finish(self) -> bool:
         return: True if the session is ended, otherwise False.
         """
 
-        # Finish the session if the state is SessionFinishState, ErrorState, MaxStepReachedState, or NoneState.
+        # Finish the session if the state is ErrorState, MaxStepReachedState, or NoneState.
         return (
             True
             if isinstance(