diff --git a/src/google/adk/cli/adk_web_server.py b/src/google/adk/cli/adk_web_server.py
index b2436d93c7..492fa96584 100644
--- a/src/google/adk/cli/adk_web_server.py
+++ b/src/google/adk/cli/adk_web_server.py
@@ -461,6 +461,12 @@ async def get_runner_async(self, app_name: str) -> Runner:
     self.runner_dict[app_name] = runner
     return runner
 
+  def _get_root_agent(self, agent_or_app: BaseAgent | App) -> BaseAgent:
+    """Extract root agent from either a BaseAgent or App object."""
+    if isinstance(agent_or_app, App):
+      return agent_or_app.root_agent
+    return agent_or_app
+
   def _create_runner(self, agentic_app: App) -> Runner:
     """Create a runner with common services."""
     return Runner(
@@ -803,9 +809,8 @@ async def add_session_to_eval_set(
 
       # Populate the session with initial session state.
       agent_or_app = self.agent_loader.load_agent(app_name)
-      if isinstance(agent_or_app, App):
-        agent_or_app = agent_or_app.root_agent
-      initial_session_state = create_empty_state(agent_or_app)
+      root_agent = self._get_root_agent(agent_or_app)
+      initial_session_state = create_empty_state(root_agent)
 
       new_eval_case = EvalCase(
           eval_id=req.eval_id,
@@ -966,7 +971,8 @@ async def run_eval(
               status_code=400, detail=f"Eval set `{eval_set_id}` not found."
           )
 
-        root_agent = self.agent_loader.load_agent(app_name)
+        agent_or_app = self.agent_loader.load_agent(app_name)
+        root_agent = self._get_root_agent(agent_or_app)
 
         eval_case_results = []
 
@@ -1305,7 +1311,8 @@ async def get_event_graph(
 
       function_calls = event.get_function_calls()
       function_responses = event.get_function_responses()
-      root_agent = self.agent_loader.load_agent(app_name)
+      agent_or_app = self.agent_loader.load_agent(app_name)
+      root_agent = self._get_root_agent(agent_or_app)
       dot_graph = None
       if function_calls:
         function_call_highlights = []