fix: remove live event buffering in runner (#6151)

Author: wuliang229

src/google/adk/runners.py

@@ -66,10 +66,6 @@
 logger = logging.getLogger('google_adk.' + __name__)
 
 
-def _is_tool_call_or_response(event: Event) -> bool:
-  return bool(event.get_function_calls() or event.get_function_responses())
-
-
 def _get_function_responses_from_content(
     content: types.Content,
 ) -> list[types.FunctionResponse]:
@@ -80,21 +76,6 @@ def _get_function_responses_from_content(
   ]
 
 
-def _is_transcription(event: Event) -> bool:
-  return (
-      event.input_transcription is not None
-      or event.output_transcription is not None
-  )
-
-
-def _has_non_empty_transcription_text(
-    transcription: types.Transcription,
-) -> bool:
-  return bool(
-      transcription and transcription.text and transcription.text.strip()
-  )
-
-
 def _apply_run_config_custom_metadata(
     event: Event, run_config: RunConfig | None
 ) -> None:
@@ -873,22 +854,6 @@ async def _exec_with_plugin(
       yield early_exit_event
     else:
       # Step 2: Otherwise continue with normal execution
-      # Note for live/bidi:
-      # the transcription may arrive later than the action(function call
-      # event and thus function response event). In this case, the order of
-      # transcription and function call event will be wrong if we just
-      # append as it arrives. To address this, we should check if there is
-      # transcription going on. If there is transcription going on, we
-      # should hold on appending the function call event until the
-      # transcription is finished. The transcription in progress can be
-      # identified by checking if the transcription event is partial. When
-      # the next transcription event is not partial, it means the previous
-      # transcription is finished. Then if there is any buffered function
-      # call event, we should append them after this finished(non-partial)
-      # transcription event.
-      buffered_events: list[Event] = []
-      is_transcribing: bool = False
-
       async with Aclosing(execute_fn(invocation_context)) as agen:
         async for event in agen:
           _apply_run_config_custom_metadata(
@@ -906,50 +871,14 @@ async def _exec_with_plugin(
           )
 
           if is_live_call:
-            if event.partial and _is_transcription(event):
-              is_transcribing = True
-            if is_transcribing and _is_tool_call_or_response(event):
-              # only buffer function call and function response event which is
-              # non-partial
-              buffered_events.append(output_event)
-              continue
-            # Note for live/bidi: for audio response, it's considered as
-            # non-partial event(event.partial=None)
-            # event.partial=False and event.partial=None are considered as
-            # non-partial event; event.partial=True is considered as partial
-            # event.
-            if event.partial is not True:
-              if _is_transcription(event) and (
-                  _has_non_empty_transcription_text(event.input_transcription)
-                  or _has_non_empty_transcription_text(
-                      event.output_transcription
-                  )
-              ):
-                # transcription end signal, append buffered events
-                is_transcribing = False
-                logger.debug(
-                    'Appending transcription finished event: %s', event
-                )
-                if self._should_append_event(event, is_live_call):
-                  await self.session_service.append_event(
-                      session=invocation_context.session, event=output_event
-                  )
-
-                for buffered_event in buffered_events:
-                  logger.debug('Appending buffered event: %s', buffered_event)
-                  await self.session_service.append_event(
-                      session=invocation_context.session, event=buffered_event
-                  )
-                  yield buffered_event  # yield buffered events to caller
-                buffered_events = []
-              else:
-                # non-transcription event or empty transcription event, for
-                # example, event that stores blob reference, should be appended.
-                if self._should_append_event(event, is_live_call):
-                  logger.debug('Appending non-buffered event: %s', event)
-                  await self.session_service.append_event(
-                      session=invocation_context.session, event=output_event
-                  )
+            # Skip partial transcriptions for Live
+            if event.partial is not True and self._should_append_event(
+                event, is_live_call
+            ):
+              logger.debug('Appending live event: %s', output_event)
+              await self.session_service.append_event(
+                  session=invocation_context.session, event=output_event
+              )
           else:
             if event.partial is not True:
               await self.session_service.append_event(