diff --git a/coagent/core/agent.py b/coagent/core/agent.py
index 5f2a8b3..4be29e7 100644
--- a/coagent/core/agent.py
+++ b/coagent/core/agent.py
@@ -161,26 +161,31 @@ async def start(self) -> None:
         """Start the current agent."""
 
         # Subscribe the agent to its own address.
-        self._sub = await self.channel.subscribe(self.address, handler=self.receive)
-
-        self._handle_data_task = asyncio.create_task(self._handle_data())
+        self._sub = await self._create_subscription()
 
         # Send a `Started` message to the current agent.
         await self.channel.publish(self.address, Started().encode(), probe=False)
 
+        if not self._handle_data_task:
+            self._handle_data_task = asyncio.create_task(self._handle_data())
+
+    async def _create_subscription(self) -> Subscription:
+        # Subscribe the agent's receive method to its own address.
+        return await self.channel.subscribe(self.address, handler=self.receive)
+
     async def stop(self) -> None:
         """Stop the current agent."""
 
         # Send a `Stopped` message to the current agent.
         await self.channel.publish(self.address, Stopped().encode(), probe=False)
 
-        if self._handle_data_task:
-            self._handle_data_task.cancel()
-
         # Unsubscribe the agent from its own address.
         if self._sub:
             await self._sub.unsubscribe()
 
+        if self._handle_data_task:
+            self._handle_data_task.cancel()
+
     async def started(self) -> None:
         """This handler is called after the agent is started."""
         pass
diff --git a/coagent/core/discovery.py b/coagent/core/discovery.py
index 94d7ad1..93bb1c1 100644
--- a/coagent/core/discovery.py
+++ b/coagent/core/discovery.py
@@ -11,6 +11,7 @@
     Address,
     AgentSpec,
     RawMessage,
+    Subscription,
 )
 from .util import Trie
 
@@ -125,13 +126,7 @@ def __init__(self):
 
     async def start(self) -> None:
         """Since discovery is a special agent, we need to start it in a different way."""
-
-        # Each query message can only be received and handled by one discovery aggregator.
-        self._sub = await self.channel.subscribe(
-            self.address,
-            handler=self.receive,
-            queue=f"{self.address.topic}_workers",
-        )
+        await super().start()
 
         # Create and start the local discovery server.
         self._server = DiscoveryServer()
@@ -139,13 +134,20 @@ async def start(self) -> None:
         self._server.init(self.channel, Address(name=f"{self.address.name}.server"))
         await self._server.start()
 
+    async def _create_subscription(self) -> Subscription:
+        # Each query message can only be received and handled by one discovery aggregator.
+        return await self.channel.subscribe(
+            self.address,
+            handler=self.receive,
+            queue=f"{self.address.topic}_workers",
+        )
+
     async def stop(self) -> None:
         """Since discovery is a special agent, we need to stop it in a different way."""
         if self._server:
             await self._server.stop()
 
-        if self._sub:
-            await self._sub.unsubscribe()
+        await super().stop()
 
     async def register(self, spec: AgentSpec) -> None:
         if spec.name == self.address.name:
@@ -250,9 +252,7 @@ def __init__(self):
 
     async def start(self) -> None:
         """Since discovery server is a special agent, we need to start it in a different way."""
-
-        # Subscribe the agent to its own address.
-        self._sub = await self.channel.subscribe(self.address, handler=self.receive)
+        await super().start()
 
         # Upon startup, the current discovery server has no agent-subscriptions.
         # Therefore, it's necessary to synchronize the existing agent-subscriptions
@@ -283,13 +283,6 @@ async def receive(raw: RawMessage) -> None:
         finally:
             await sub.unsubscribe()
 
-    async def stop(self) -> None:
-        """Since discovery server is a special agent, we need to stop it in a different way."""
-
-        # Unsubscribe the agent from its own address.
-        if self._sub:
-            await self._sub.unsubscribe()
-
     async def register(self, spec: AgentSpec) -> None:
         if spec.name == self.address.name:
             raise ValueError(f"Agent type '{self.address.name}' is reserved")
diff --git a/coagent/core/factory.py b/coagent/core/factory.py
index 973ae13..5b78cf4 100644
--- a/coagent/core/factory.py
+++ b/coagent/core/factory.py
@@ -8,6 +8,7 @@
     Agent,
     AgentSpec,
     State,
+    Subscription,
 )
 
 
@@ -42,25 +43,24 @@ def __init__(self, spec: AgentSpec) -> None:
 
     async def start(self) -> None:
         """Since factory is a special agent, we need to start it in a different way."""
-        # Subscribe the factory to the given address.
+        await super().start()
+
+        # Start the recycle loop.
+        self._recycle_task = asyncio.create_task(self._recycle())
+
+    async def _create_subscription(self) -> Subscription:
+        # Each CreateAgent message can only be received and handled by one factory agent.
         #
         # Note that we specify a queue parameter to distribute requests among
         # multiple factory agents of the same type of primitive agent.
-        self._sub = await self.channel.subscribe(
+        return await self.channel.subscribe(
             self.address,
             handler=self.receive,
             queue=f"{self.address.topic}_workers",
         )
 
-        # Start the recycle loop.
-        self._recycle_task = asyncio.create_task(self._recycle())
-
     async def stop(self) -> None:
         """Since factory is a special agent, we need to stop it in a different way."""
-        # Unsubscribe the factory from the address.
-        if self._sub:
-            await self._sub.unsubscribe()
-
         # Stop all agents.
         for agent in self._agents.values():
             await agent.stop()
@@ -70,6 +70,8 @@ async def stop(self) -> None:
         if self._recycle_task:
             self._recycle_task.cancel()
 
+        await super().stop()
+
     async def _recycle(self) -> None:
         """The recycle loop for deleting idle agents."""
         while True: