fix: apply run_config custom_metadata to user event in node runtime

The node-based runtime path (LlmAgent chat mode and BaseNode) appended
the user event without the run-level custom_metadata that the legacy
agent path and v1 both apply, so it was dropped from session history.

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 934433213

Author: GWeale

src/google/adk/runners.py

@@ -736,6 +736,7 @@ async def _append_user_event(
       iso = _find_active_task_isolation_scope(ic.session)
       if iso is not None:
         event.isolation_scope = iso
+    _apply_run_config_custom_metadata(event, ic.run_config)
     return await self.session_service.append_event(
         session=ic.session, event=event
     )

tests/unittests/runners/test_runner_node.py

@@ -27,6 +27,7 @@
 from google.adk.agents.callback_context import CallbackContext
 from google.adk.agents.context import Context
 from google.adk.agents.llm_agent import LlmAgent
+from google.adk.agents.run_config import RunConfig
 from google.adk.events.event import Event
 from google.adk.runners import Runner
 from google.adk.sessions.in_memory_session_service import InMemorySessionService
@@ -256,6 +257,30 @@ async def test_multiple_invocations_accumulate_events():
   assert outputs == ['Echo: first', 'Echo: second', 'Echo: third']
 
 
+@pytest.mark.asyncio
+async def test_run_config_custom_metadata_stamps_user_event():
+  """The node path stamps the user event with run-level custom_metadata."""
+  ss = InMemorySessionService()
+  runner = Runner(
+      app_name='test', node=_EchoNode(name='echo'), session_service=ss
+  )
+  session = await ss.create_session(app_name='test', user_id='u')
+
+  async for _ in runner.run_async(
+      user_id='u',
+      session_id=session.id,
+      new_message=_user_message('hi'),
+      run_config=RunConfig(custom_metadata={'turn_id': 't-1'}),
+  ):
+    pass
+
+  updated = await ss.get_session(
+      app_name='test', user_id='u', session_id=session.id
+  )
+  user_event = next(e for e in updated.events if e.author == 'user')
+  assert user_event.custom_metadata == {'turn_id': 't-1'}
+
+
 # ---------------------------------------------------------------------------
 # yield_user_message
 # ---------------------------------------------------------------------------

tests/unittests/test_runners.py

@@ -972,6 +972,41 @@ async def test_run_config_custom_metadata_propagates_to_events():
   assert user_event.custom_metadata == {"request_id": "req-1"}
 
 
+@pytest.mark.asyncio
+async def test_run_config_custom_metadata_stamps_user_event_in_chat_mode():
+  """LlmAgent chat path stamps the user event with run-level custom_metadata."""
+  session_service = InMemorySessionService()
+
+  def _before_agent_callback(callback_context) -> types.Content:
+    del callback_context  # Unused; short-circuits the model call.
+    return types.Content(role="model", parts=[types.Part(text="hi back")])
+
+  agent = LlmAgent(
+      name="chat_agent", before_agent_callback=_before_agent_callback
+  )
+  runner = Runner(
+      app_name=TEST_APP_ID, agent=agent, session_service=session_service
+  )
+  await session_service.create_session(
+      app_name=TEST_APP_ID, user_id=TEST_USER_ID, session_id=TEST_SESSION_ID
+  )
+
+  run_config = RunConfig(custom_metadata={"turn_id": "t-1"})
+  async for _ in runner.run_async(
+      user_id=TEST_USER_ID,
+      session_id=TEST_SESSION_ID,
+      new_message=types.Content(role="user", parts=[types.Part(text="hi")]),
+      run_config=run_config,
+  ):
+    pass
+
+  session = await session_service.get_session(
+      app_name=TEST_APP_ID, user_id=TEST_USER_ID, session_id=TEST_SESSION_ID
+  )
+  user_event = next(event for event in session.events if event.author == "user")
+  assert user_event.custom_metadata == {"turn_id": "t-1"}
+
+
 class TestRunnerWithPlugins:
   """Tests for Runner with plugins."""