Add UserRequirement to watch in default if the role is not set to watch

metagpt/schema.py

@@ -121,6 +121,10 @@ 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,