feat: Create a new HookEvent for Multiagent (#925)

* add a base class example

* feat:add BaseHookEvent for multiagent use

Author: JackYPCOnline

src/strands/hooks/__init__.py

@@ -39,7 +39,7 @@ def log_end(self, event: AfterInvocationEvent) -> None:
     BeforeToolCallEvent,
     MessageAddedEvent,
 )
-from .registry import HookCallback, HookEvent, HookProvider, HookRegistry
+from .registry import BaseHookEvent, HookCallback, HookEvent, HookProvider, HookRegistry
 
 __all__ = [
     "AgentInitializedEvent",
@@ -54,4 +54,6 @@ def log_end(self, event: AfterInvocationEvent) -> None:
     "HookProvider",
     "HookCallback",
     "HookRegistry",
+    "HookEvent",
+    "BaseHookEvent",
 ]

src/strands/hooks/registry.py

@@ -15,14 +15,8 @@
 
 
 @dataclass
-class HookEvent:
-    """Base class for all hook events.
-
-    Attributes:
-        agent: The agent instance that triggered this event.
-    """
-
-    agent: "Agent"
+class BaseHookEvent:
+    """Base class for all hook events."""
 
     @property
     def should_reverse_callbacks(self) -> bool:
@@ -66,10 +60,21 @@ def __setattr__(self, name: str, value: Any) -> None:
         raise AttributeError(f"Property {name} is not writable")
 
 
-TEvent = TypeVar("TEvent", bound=HookEvent, contravariant=True)
+@dataclass
+class HookEvent(BaseHookEvent):
+    """Base class for single agent hook events.
+
+    Attributes:
+        agent: The agent instance that triggered this event.
+    """
+
+    agent: "Agent"
+
+
+TEvent = TypeVar("TEvent", bound=BaseHookEvent, contravariant=True)
 """Generic for adding callback handlers - contravariant to allow adding handlers which take in base classes."""
 
-TInvokeEvent = TypeVar("TInvokeEvent", bound=HookEvent)
+TInvokeEvent = TypeVar("TInvokeEvent", bound=BaseHookEvent)
 """Generic for invoking events - non-contravariant to enable returning events."""