fix: Correct EventAction merging logic and add corresponding tests

src/google/adk/flows/llm_flows/functions.py

@@ -511,6 +511,16 @@ def __build_response_event(
   return function_response_event
 
 
+def deep_merge_dicts(d1: dict, d2: dict) -> dict:
+  """Recursively merges d2 into d1."""
+  for key, value in d2.items():
+    if key in d1 and isinstance(d1[key], dict) and isinstance(value, dict):
+      d1[key] = deep_merge_dicts(d1[key], value)
+    else:
+      d1[key] = value
+  return d1
+
+
 def merge_parallel_function_response_events(
     function_response_events: list['Event'],
 ) -> 'Event':
@@ -529,15 +539,17 @@ def merge_parallel_function_response_events(
   base_event = function_response_events[0]
 
   # Merge actions from all events
-
-  merged_actions = EventActions()
-  merged_requested_auth_configs = {}
+  merged_actions_data = {}
   for event in function_response_events:
-    merged_requested_auth_configs.update(event.actions.requested_auth_configs)
-    merged_actions = merged_actions.model_copy(
-        update=event.actions.model_dump()
-    )
-  merged_actions.requested_auth_configs = merged_requested_auth_configs
+    if event.actions:
+      # Use `by_alias=True` because it converts the model to a dictionary while respecting field aliases, ensuring that the enum fields are correctly handled without creating a duplicate.
+      merged_actions_data = deep_merge_dicts(
+          merged_actions_data,
+          event.actions.model_dump(exclude_none=True, by_alias=True),
+      )
+
+  merged_actions = EventActions.model_validate(merged_actions_data)
+
   # Create the new merged event
   merged_event = Event(
       invocation_id=Event.new_id(),

tests/unittests/flows/llm_flows/test_functions_parallel.py

@@ -0,0 +1,107 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from google.adk.agents import Agent
+from google.adk.events.event_actions import EventActions
+from google.adk.tools import ToolContext
+from google.genai import types
+import pytest
+
+from ... import testing_utils
+
+
+@pytest.mark.asyncio
+async def test_parallel_function_calls_with_state_change():
+  function_calls = [
+      types.Part.from_function_call(
+          name='update_session_state',
+          args={'key': 'test_key1', 'value': 'test_value1'},
+      ),
+      types.Part.from_function_call(
+          name='update_session_state',
+          args={'key': 'test_key2', 'value': 'test_value2'},
+      ),
+      types.Part.from_function_call(
+          name='transfer_to_agent', args={'agent_name': 'test_sub_agent'}
+      ),
+  ]
+  function_responses = [
+      types.Part.from_function_response(
+          name='update_session_state', response={'result': None}
+      ),
+      types.Part.from_function_response(
+          name='update_session_state', response={'result': None}
+      ),
+      types.Part.from_function_response(
+          name='transfer_to_agent', response={'result': None}
+      ),
+  ]
+
+  responses: list[types.Content] = [
+      function_calls,
+      'response1',
+  ]
+  function_called = 0
+  mock_model = testing_utils.MockModel.create(responses=responses)
+
+  async def update_session_state(
+      key: str, value: str, tool_context: ToolContext
+  ) -> None:
+    nonlocal function_called
+    function_called += 1
+    tool_context.state.update({key: value})
+    return
+
+  async def transfer_to_agent(
+      agent_name: str, tool_context: ToolContext
+  ) -> None:
+    nonlocal function_called
+    function_called += 1
+    tool_context.actions.transfer_to_agent = agent_name
+    return
+
+  test_sub_agent = Agent(
+      name='test_sub_agent',
+  )
+
+  agent = Agent(
+      name='root_agent',
+      model=mock_model,
+      tools=[update_session_state, transfer_to_agent],
+      sub_agents=[test_sub_agent],
+  )
+  runner = testing_utils.TestInMemoryRunner(agent)
+  events = await runner.run_async_with_new_session('test')
+
+  # Notice that the following assertion only checks the "contents" part of the events.
+  # The "actions" part will be checked later.
+  assert testing_utils.simplify_events(events) == [
+      ('root_agent', function_calls),
+      ('root_agent', function_responses),
+      ('test_sub_agent', 'response1'),
+  ]
+
+  # Asserts the function calls.
+  assert function_called == 3
+
+  # Asserts the actions in response event.
+  response_event = events[1]
+
+  assert response_event.actions == EventActions(
+      state_delta={
+          'test_key1': 'test_value1',
+          'test_key2': 'test_value2',
+      },
+      transfer_to_agent='test_sub_agent',
+  )