Not invoking on_function_calls_started for the cancel function, and creating on_function_calls_cancelled

src/pipecat/services/llm_service.py

@@ -183,7 +183,10 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
 
     - on_completion_timeout: Called when an LLM completion timeout occurs
     - on_function_calls_started: Called when function calls are received and
-      execution is about to start
+      execution is about to start. Built-in tools (e.g. ``cancel_async_tool_call``)
+      are excluded from this event.
+    - on_function_calls_cancelled: Called after one or more async tool calls are
+      cancelled.
 
     Example::
 
@@ -194,6 +197,10 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
         @task.event_handler("on_function_calls_started")
         async def on_function_calls_started(service, function_calls):
             logger.info(f"Starting {len(function_calls)} function calls")
+
+        @task.event_handler("on_function_calls_cancelled")
+        async def on_function_calls_cancelled(service, cancelled):
+            logger.info(f"Cancelled {len(cancelled)} async function calls")
     """
 
     _settings: LLMSettings
@@ -252,6 +259,7 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
         self._summary_task: Optional[asyncio.Task] = None
 
         self._register_event_handler("on_function_calls_started")
+        self._register_event_handler("on_function_calls_cancelled")
         self._register_event_handler("on_completion_timeout")
 
     def get_llm_adapter(self) -> BaseLLMAdapter:
@@ -693,9 +701,14 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
         if len(function_calls) == 0:
             return
 
-        await self._call_event_handler("on_function_calls_started", function_calls)
-
-        await self.broadcast_frame(FunctionCallsStartedFrame, function_calls=function_calls)
+        # Exclude the built-in cancel tool — it's an internal mechanism and
+        # should not be surfaced to user-facing event handlers or frames.
+        user_visible_calls = [
+            fc for fc in function_calls if fc.function_name != CANCEL_ASYNC_TOOL_NAME
+        ]
+        if user_visible_calls:
+            await self._call_event_handler("on_function_calls_started", user_visible_calls)
+            await self.broadcast_frame(FunctionCallsStartedFrame, function_calls=user_visible_calls)
 
         # When group_parallel_tools is True all calls share a group_id so the
         # aggregator triggers the LLM exactly once after the last one completes.
@@ -954,6 +967,7 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
             tool_call_id: tool_call_id to cancel.
         """
         cancelled_tasks = set()
+        cancelled_items = []
         for task, runner_item in self._function_call_tasks.items():
             if runner_item.tool_call_id == tool_call_id:
                 name = runner_item.function_name
@@ -973,13 +987,18 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
                     FunctionCallCancelFrame, function_name=name, tool_call_id=tool_call_id
                 )
 
+                cancelled_items.append(runner_item)
                 logger.debug(f"{self} Async function call [{name}:{tool_call_id}] cancelled")
 
         for task in cancelled_tasks:
             self._function_call_task_finished(task)
 
+        if cancelled_items:
+            await self._call_event_handler("on_function_calls_cancelled", cancelled_items)
+
     async def _cancel_function_call(self, function_name: Optional[str]):
         cancelled_tasks = set()
+        cancelled_items = []
         for task, runner_item in self._function_call_tasks.items():
             if runner_item.registry_item.function_name == function_name:
                 name = runner_item.function_name
@@ -999,12 +1018,16 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
                     FunctionCallCancelFrame, function_name=name, tool_call_id=tool_call_id
                 )
 
+                cancelled_items.append(runner_item)
                 logger.debug(f"{self} Function call [{name}:{tool_call_id}] has been cancelled")
 
         # Remove all cancelled tasks from our set.
         for task in cancelled_tasks:
             self._function_call_task_finished(task)
 
+        if cancelled_items:
+            await self._call_event_handler("on_function_calls_cancelled", cancelled_items)
+
     def _function_call_task_finished(self, task: asyncio.Task):
         if task in self._function_call_tasks:
             del self._function_call_tasks[task]