diff --git a/metagpt/actions/role_run.py b/metagpt/actions/role_run.py
new file mode 100644
index 000000000..9f0c626b8
--- /dev/null
+++ b/metagpt/actions/role_run.py
@@ -0,0 +1,16 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+"""
+@Time    : 2023/12/18
+@Author  : mashenquan
+@File    : role_run.py
+@Desc    : Message type caused by `Role.run()` invocation.
+"""
+from metagpt.actions import Action
+
+
+class RoleRun(Action):
+    """Message type caused by `Role.run` invocation"""
+
+    async def run(self, *args, **kwargs):
+        raise NotImplementedError
diff --git a/metagpt/roles/role.py b/metagpt/roles/role.py
index 1e7ebf711..413595c6b 100644
--- a/metagpt/roles/role.py
+++ b/metagpt/roles/role.py
@@ -27,7 +27,7 @@ from pydantic import BaseModel, Field
 
 from metagpt.actions import Action, ActionOutput
 from metagpt.actions.action_node import ActionNode
-from metagpt.actions.add_requirement import UserRequirement
+from metagpt.actions.role_run import RoleRun
 from metagpt.llm import LLM, HumanProvider
 from metagpt.logs import logger
 from metagpt.memory import Memory
@@ -127,17 +127,7 @@ class RoleContext(BaseModel):
         return self.memory.get()
 
 
-class _RoleInjector(type):
-    def __call__(cls, *args, **kwargs):
-        instance = super().__call__(*args, **kwargs)
-
-        if not instance._rc.watch:
-            instance._watch([UserRequirement])
-
-        return instance
-
-
-class Role(metaclass=_RoleInjector):
+class Role:
     """Role/Agent"""
 
     def __init__(self, name="", profile="", goal="", constraints="", desc="", is_human=False):
@@ -152,7 +142,6 @@ class Role(metaclass=_RoleInjector):
         self._rc = RoleContext()
         self._subscription = {any_to_str(self), name} if name else {any_to_str(self)}
 
-
     def _reset(self):
         self._states = []
         self._actions = []
@@ -304,7 +293,9 @@ class Role(metaclass=_RoleInjector):
         old_messages = [] if ignore_memory else self._rc.memory.get()
         self._rc.memory.add_batch(news)
         # Filter out messages of interest.
-        self._rc.news = [n for n in news if n.cause_by in self._rc.watch and n not in old_messages]
+        watch = self._rc.watch or set()
+        watch.add(any_to_str(RoleRun))
+        self._rc.news = [n for n in news if n.cause_by in watch and n not in old_messages]
 
         # Design Rules:
         # If you need to further categorize Message objects, you can do so using the Message.set_meta function.
@@ -401,6 +392,8 @@ class Role(metaclass=_RoleInjector):
                 msg = with_message
             elif isinstance(with_message, list):
                 msg = Message("\n".join(with_message))
+            if not msg.cause_by:
+                msg.cause_by = RoleRun
             self.put_message(msg)
 
         if not await self._observe():
diff --git a/metagpt/schema.py b/metagpt/schema.py
index 5aec378e4..758149efa 100644
--- a/metagpt/schema.py
+++ b/metagpt/schema.py
@@ -121,10 +121,6 @@ class Message(BaseModel):
         :param send_to: Specifies the target recipient or consumer for message delivery in the environment.
         :param role: Message meta info tells who sent this message.
         """
-        if not cause_by:
-            from metagpt.actions import UserRequirement
-            cause_by = UserRequirement
-
         super().__init__(
             id=uuid.uuid4().hex,
             content=content,