fix(events): exclude state-only events from final responses

src/google/adk/events/event.py

@@ -302,6 +302,15 @@ def is_final_response(self) -> bool:
         and not self.get_function_calls()
     ):
       return True
+    # A state-only event persists framework state; it is not an agent response.
+    # Keep empty Content events final because a model may legitimately complete
+    # a turn without producing any parts.
+    if (
+        self.content is None
+        and self.output is None
+        and self.actions.state_delta
+    ):
+      return False
     return (
         not self.get_function_calls()
         and not self.get_function_responses()

tests/unittests/agents/test_base_agent.py

@@ -329,6 +329,30 @@ async def test_run_async_before_agent_callback_bypass_agent(
   assert events[0].content.parts[0].text == 'agent run is bypassed.'
 
 
+@pytest.mark.asyncio
+async def test_run_async_before_agent_callback_state_delta_is_not_final(
+    request: pytest.FixtureRequest,
+):
+  def update_state(callback_context: CallbackContext) -> None:
+    callback_context.state['callback_state'] = 'before'
+
+  agent = _TestingAgent(
+      name=f'{request.function.__name__}_test_agent',
+      before_agent_callback=update_state,
+  )
+  parent_ctx = await _create_parent_invocation_context(
+      request.function.__name__, agent
+  )
+
+  events = [event async for event in agent.run_async(parent_ctx)]
+
+  assert len(events) == 2
+  assert events[0].content is None
+  assert events[0].actions.state_delta == {'callback_state': 'before'}
+  assert events[0].is_final_response() is False
+  assert events[1].is_final_response() is True
+
+
 @pytest.mark.asyncio
 async def test_run_async_with_async_before_agent_callback_bypass_agent(
     request: pytest.FixtureRequest,
@@ -694,6 +718,30 @@ async def test_run_async_after_agent_callback_append_reply(
   )
 
 
+@pytest.mark.asyncio
+async def test_run_async_after_agent_callback_state_delta_is_not_final(
+    request: pytest.FixtureRequest,
+):
+  def update_state(callback_context: CallbackContext) -> None:
+    callback_context.state['callback_state'] = 'after'
+
+  agent = _TestingAgent(
+      name=f'{request.function.__name__}_test_agent',
+      after_agent_callback=update_state,
+  )
+  parent_ctx = await _create_parent_invocation_context(
+      request.function.__name__, agent
+  )
+
+  events = [event async for event in agent.run_async(parent_ctx)]
+
+  assert len(events) == 2
+  assert events[0].is_final_response() is True
+  assert events[1].content is None
+  assert events[1].actions.state_delta == {'callback_state': 'after'}
+  assert events[1].is_final_response() is False
+
+
 @pytest.mark.asyncio
 async def test_run_async_with_async_after_agent_callback_append_reply(
     request: pytest.FixtureRequest,

tests/unittests/events/test_event.py

@@ -69,6 +69,16 @@ def test_is_final_response_empty_event_is_final():
   assert event.is_final_response() is True
 
 
+def test_is_final_response_state_delta_only_event_is_not_final():
+  event = _event(actions=EventActions(state_delta={'key': 'value'}))
+  assert event.is_final_response() is False
+
+
+def test_is_final_response_empty_content_with_state_delta_is_final():
+  event = _event(parts=[], actions=EventActions(state_delta={'key': 'value'}))
+  assert event.is_final_response() is True
+
+
 def test_is_final_response_with_function_call_is_not_final():
   event = _event(parts=[_text_part(), _function_call_part()])
   assert event.is_final_response() is False