Expose on_summary_applied event on LLMAssistantAggregator

Forward the on_summary_applied event from the internal summarizer to
the aggregator so users can listen for it without accessing private
members. Update summarization examples to use the new public event.

examples/foundational/54-context-summarization-openai.py

@@ -138,17 +138,14 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
     )
 
     # Listen for summarization events
-    summarizer = assistant_aggregator._summarizer
-    if summarizer:
-
-        @summarizer.event_handler("on_summary_applied")
-        async def on_summary_applied(summarizer, event: SummaryAppliedEvent):
-            logger.info(
-                f"Context summarized: {event.original_message_count} messages -> "
-                f"{event.new_message_count} messages "
-                f"({event.summarized_message_count} summarized, "
-                f"{event.preserved_message_count} preserved)"
-            )
+    @assistant_aggregator.event_handler("on_summary_applied")
+    async def on_summary_applied(aggregator, summarizer, event: SummaryAppliedEvent):
+        logger.info(
+            f"Context summarized: {event.original_message_count} messages -> "
+            f"{event.new_message_count} messages "
+            f"({event.summarized_message_count} summarized, "
+            f"{event.preserved_message_count} preserved)"
+        )
 
     pipeline = Pipeline(
         [

examples/foundational/54a-context-summarization-google.py

@@ -138,17 +138,14 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
     )
 
     # Listen for summarization events
-    summarizer = assistant_aggregator._summarizer
-    if summarizer:
-
-        @summarizer.event_handler("on_summary_applied")
-        async def on_summary_applied(summarizer, event: SummaryAppliedEvent):
-            logger.info(
-                f"Context summarized: {event.original_message_count} messages -> "
-                f"{event.new_message_count} messages "
-                f"({event.summarized_message_count} summarized, "
-                f"{event.preserved_message_count} preserved)"
-            )
+    @assistant_aggregator.event_handler("on_summary_applied")
+    async def on_summary_applied(aggregator, summarizer, event: SummaryAppliedEvent):
+        logger.info(
+            f"Context summarized: {event.original_message_count} messages -> "
+            f"{event.new_message_count} messages "
+            f"({event.summarized_message_count} summarized, "
+            f"{event.preserved_message_count} preserved)"
+        )
 
     pipeline = Pipeline(
         [

examples/foundational/54c-context-summarization-dedicated-llm.py

@@ -177,17 +177,14 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
     )
 
     # Listen for summarization events
-    summarizer = assistant_aggregator._summarizer
-    if summarizer:
-
-        @summarizer.event_handler("on_summary_applied")
-        async def on_summary_applied(summarizer, event: SummaryAppliedEvent):
-            logger.info(
-                f"Context summarized: {event.original_message_count} messages -> "
-                f"{event.new_message_count} messages "
-                f"({event.summarized_message_count} summarized, "
-                f"{event.preserved_message_count} preserved)"
-            )
+    @assistant_aggregator.event_handler("on_summary_applied")
+    async def on_summary_applied(aggregator, summarizer, event: SummaryAppliedEvent):
+        logger.info(
+            f"Context summarized: {event.original_message_count} messages -> "
+            f"{event.new_message_count} messages "
+            f"({event.summarized_message_count} summarized, "
+            f"{event.preserved_message_count} preserved)"
+        )
 
     pipeline = Pipeline(
         [

src/pipecat/processors/aggregators/llm_response_universal.py

@@ -70,7 +70,10 @@ from pipecat.processors.aggregators.llm_context import (
     LLMSpecificMessage,
     NotGiven,
 )
-from pipecat.processors.aggregators.llm_context_summarizer import LLMContextSummarizer
+from pipecat.processors.aggregators.llm_context_summarizer import (
+    LLMContextSummarizer,
+    SummaryAppliedEvent,
+)
 from pipecat.processors.frame_processor import FrameCallback, FrameDirection, FrameProcessor
 from pipecat.turns.user_idle_controller import UserIdleController
 from pipecat.turns.user_mute import BaseUserMuteStrategy
@@ -796,6 +799,7 @@ class LLMAssistantAggregator(LLMContextAggregator):
     - on_assistant_turn_started: Called when the assistant turn starts
     - on_assistant_turn_stopped: Called when the assistant turn ends
     - on_assistant_thought: Called when an assistant thought is available
+    - on_summary_applied: Called when a context summarization is applied
 
     Example::
 
@@ -811,6 +815,10 @@ class LLMAssistantAggregator(LLMContextAggregator):
         async def on_assistant_thought(aggregator, message: AssistantThoughtMessage):
             ...
 
+        @aggregator.event_handler("on_summary_applied")
+        async def on_summary_applied(aggregator, summarizer, event: SummaryAppliedEvent):
+            ...
+
     """
 
     def __init__(
@@ -873,10 +881,12 @@ class LLMAssistantAggregator(LLMContextAggregator):
         self._summarizer.add_event_handler(
             "on_request_summarization", self._on_request_summarization
         )
+        self._summarizer.add_event_handler("on_summary_applied", self._on_summary_applied)
 
         self._register_event_handler("on_assistant_turn_started")
         self._register_event_handler("on_assistant_turn_stopped")
         self._register_event_handler("on_assistant_thought")
+        self._register_event_handler("on_summary_applied")
 
     @property
     def has_function_calls_in_progress(self) -> bool:
@@ -1294,6 +1304,19 @@ class LLMAssistantAggregator(LLMContextAggregator):
         """
         await self.push_frame(frame, FrameDirection.UPSTREAM)
 
+    async def _on_summary_applied(
+        self, summarizer: LLMContextSummarizer, event: SummaryAppliedEvent
+    ):
+        """Handle summary applied event from the summarizer.
+
+        Forwards the event to any registered `on_summary_applied` handlers.
+
+        Args:
+            summarizer: The summarizer that applied the summary.
+            event: The summary applied event.
+        """
+        await self._call_event_handler("on_summary_applied", summarizer, event)
+
 
 class LLMContextAggregatorPair:
     """Pair of LLM context aggregators for updating context with user and assistant messages."""