refactor(hook): add reraise flag to AgentHook and remove _LoopHookChain

Add reraise parameter to AgentHook so hooks can opt out of exception
swallowing in CompositeHook._for_each_hook_safe. _LoopHook sets
reraise=True to let its exceptions propagate. _LoopHookChain is removed
and replaced with CompositeHook([loop_hook] + extra_hooks).

Signed-off-by: Lingao Meng <menglingao@xiaomi.com>

nanobot/agent/hook.py

@@ -29,6 +29,9 @@ class AgentHookContext:
 class AgentHook:
     """Minimal lifecycle surface for shared runner customization."""
 
+    def __init__(self, reraise: bool = False) -> None:
+        self._reraise = reraise
+
     def wants_streaming(self) -> bool:
         return False
 
@@ -69,6 +72,10 @@ class CompositeHook(AgentHook):
 
     async def _for_each_hook_safe(self, method_name: str, *args: Any, **kwargs: Any) -> None:
         for h in self._hooks:
+            if h._reraise:
+                await getattr(h, method_name)(*args, **kwargs)
+                continue
+
             try:
                 await getattr(h, method_name)(*args, **kwargs)
             except Exception:

nanobot/agent/loop.py

@@ -54,6 +54,7 @@ class _LoopHook(AgentHook):
         chat_id: str = "direct",
         message_id: str | None = None,
     ) -> None:
+        super().__init__(reraise=True)
         self._loop = agent_loop
         self._on_progress = on_progress
         self._on_stream = on_stream
@@ -108,44 +109,6 @@ class _LoopHook(AgentHook):
     def finalize_content(self, context: AgentHookContext, content: str | None) -> str | None:
         return self._loop._strip_think(content)
 
-
-class _LoopHookChain(AgentHook):
-    """Run the core hook before extra hooks."""
-
-    __slots__ = ("_primary", "_extras")
-
-    def __init__(self, primary: AgentHook, extra_hooks: list[AgentHook]) -> None:
-        self._primary = primary
-        self._extras = CompositeHook(extra_hooks)
-
-    def wants_streaming(self) -> bool:
-        return self._primary.wants_streaming() or self._extras.wants_streaming()
-
-    async def before_iteration(self, context: AgentHookContext) -> None:
-        await self._primary.before_iteration(context)
-        await self._extras.before_iteration(context)
-
-    async def on_stream(self, context: AgentHookContext, delta: str) -> None:
-        await self._primary.on_stream(context, delta)
-        await self._extras.on_stream(context, delta)
-
-    async def on_stream_end(self, context: AgentHookContext, *, resuming: bool) -> None:
-        await self._primary.on_stream_end(context, resuming=resuming)
-        await self._extras.on_stream_end(context, resuming=resuming)
-
-    async def before_execute_tools(self, context: AgentHookContext) -> None:
-        await self._primary.before_execute_tools(context)
-        await self._extras.before_execute_tools(context)
-
-    async def after_iteration(self, context: AgentHookContext) -> None:
-        await self._primary.after_iteration(context)
-        await self._extras.after_iteration(context)
-
-    def finalize_content(self, context: AgentHookContext, content: str | None) -> str | None:
-        content = self._primary.finalize_content(context, content)
-        return self._extras.finalize_content(context, content)
-
-
 class AgentLoop:
     """
     The agent loop is the core processing engine.
@@ -359,7 +322,7 @@ class AgentLoop:
             message_id=message_id,
         )
         hook: AgentHook = (
-            _LoopHookChain(loop_hook, self._extra_hooks)
+            CompositeHook([loop_hook] + self._extra_hooks)
             if self._extra_hooks
             else loop_hook
         )