diff --git a/coretk/coretk/coreclient.py b/coretk/coretk/coreclient.py
index e5ba838e..ad912422 100644
--- a/coretk/coretk/coreclient.py
+++ b/coretk/coretk/coreclient.py
@@ -71,6 +71,7 @@ class CoreClient:
         # data for managing the current session
         self.nodes = {}
         self.edges = {}
+        self.hooks = {}
         self.id = 1
         self.reusable = []
         self.preexisting = set()
@@ -97,19 +98,30 @@ class CoreClient:
         )
 
     def join_session(self, session_id):
-        # query session and set as current session
+        # update session and title
         self.session_id = session_id
-        response = self.client.get_session(self.session_id)
-        logging.info("joining session(%s): %s", self.session_id, response)
-        self.client.events(self.session_id, self.handle_events)
-
-        # set title to session
         self.master.title(f"CORE Session({self.session_id})")
 
-        # determine next node id and reusable nodes
-        session = response.session
+        # clear session data
         self.reusable.clear()
         self.preexisting.clear()
+        self.nodes.clear()
+        self.edges.clear()
+        self.hooks.clear()
+
+        # get session data
+        response = self.client.get_session(self.session_id)
+        logging.info("joining session(%s): %s", self.session_id, response)
+        session = response.session
+        self.client.events(self.session_id, self.handle_events)
+
+        # get hooks
+        response = self.client.get_hooks(self.session_id)
+        logging.info("joined session hooks: %s", response)
+        for hook in response.hooks:
+            self.hooks[hook.file] = hook
+
+        # determine next node id and reusable nodes
         max_id = 1
         for node in session.nodes:
             if node.id > max_id:
@@ -262,9 +274,10 @@ class CoreClient:
         mobility_configs=None,
     ):
         response = self.client.start_session(
-            session_id=self.session_id,
-            nodes=nodes,
-            links=links,
+            self.session_id,
+            nodes,
+            links,
+            hooks=list(self.hooks.values()),
             wlan_configs=wlan_configs,
         )
         logging.debug("Start session %s, result: %s", self.session_id, response.result)
diff --git a/coretk/coretk/dialogs/hooks.py b/coretk/coretk/dialogs/hooks.py
index a4195246..7e1338ad 100644
--- a/coretk/coretk/dialogs/hooks.py
+++ b/coretk/coretk/dialogs/hooks.py
@@ -1,4 +1,3 @@
-import logging
 import tkinter as tk
 from tkinter import ttk
 
@@ -11,7 +10,7 @@ class HookDialog(Dialog):
         super().__init__(master, app, "Hook", modal=True)
         self.name = tk.StringVar()
         self.data = None
-        self.hook = None
+        self.hook = core_pb2.Hook()
         self.state = tk.StringVar()
         self.draw()
 
@@ -82,11 +81,9 @@ class HookDialog(Dialog):
     def save(self):
         data = self.data.get("1.0", tk.END).strip()
         state_value = core_pb2.SessionState.Enum.Value(self.state.get())
-        self.hook = core_pb2.Hook(state=state_value, file=self.name.get(), data=data)
-        response = self.app.core.client.add_hook(
-            self.app.core.session_id, self.hook.state, self.hook.file, self.hook.data
-        )
-        logging.info("add hook: %s", response)
+        self.hook.file = self.name.get()
+        self.hook.data = data
+        self.hook.state = state_value
         self.destroy()
 
 
@@ -97,20 +94,16 @@ class HooksDialog(Dialog):
         self.edit_button = None
         self.delete_button = None
         self.selected = None
-        self.hooks = {}
         self.draw()
 
     def draw(self):
-        response = self.app.core.client.get_hooks(self.app.core.session_id)
-        logging.info("get hooks: %s", response)
         self.columnconfigure(0, weight=1)
         self.rowconfigure(0, weight=1)
         self.listbox = tk.Listbox(self)
         self.listbox.grid(row=0, sticky="nsew")
         self.listbox.bind("<<ListboxSelect>>", self.select)
-        for hook in response.hooks:
-            self.hooks[hook.file] = hook
-            self.listbox.insert(tk.END, hook.file)
+        for hook_file in self.app.core.hooks:
+            self.listbox.insert(tk.END, hook_file)
         frame = tk.Frame(self)
         frame.grid(row=1, sticky="ew")
         for i in range(4):
@@ -131,11 +124,11 @@ class HooksDialog(Dialog):
         dialog.show()
         hook = dialog.hook
         if hook:
-            self.hooks[hook.file] = hook
+            self.app.core.hooks[hook.file] = hook
             self.listbox.insert(tk.END, hook.file)
 
     def click_edit(self):
-        hook = self.hooks[self.selected]
+        hook = self.app.core.hooks[self.selected]
         dialog = HookDialog(self, self.app)
         dialog.set(hook)
         dialog.show()