diff --git a/src/google/adk/runners.py b/src/google/adk/runners.py
index c85ac6ff94..7d82069b60 100644
--- a/src/google/adk/runners.py
+++ b/src/google/adk/runners.py
@@ -474,7 +474,11 @@ async def _run_node_async(
     with tracer.start_as_current_span('invocation'):
       # 1. Setup
       session = await self._get_or_create_session(
-          user_id=user_id, session_id=session_id
+          user_id=user_id,
+          session_id=session_id,
+          get_session_config=run_config.get_session_config
+          if run_config
+          else None,
       )
 
       # Validate and resolve resume inputs
@@ -1000,7 +1004,9 @@ async def run_async(
 
       if self.agent.mode == 'chat':
         session = await self._get_or_create_session(
-            user_id=user_id, session_id=session_id
+            user_id=user_id,
+            session_id=session_id,
+            get_session_config=run_config.get_session_config,
         )
         # when the chat coordinator has task-mode sub-agents,
         # the wrapper handles delegation via ctx.run_node. Don't let
diff --git a/tests/unittests/test_runners.py b/tests/unittests/test_runners.py
index 22f6ac55f4..10b2c52b15 100644
--- a/tests/unittests/test_runners.py
+++ b/tests/unittests/test_runners.py
@@ -1695,9 +1695,28 @@ async def test_run_async_passes_get_session_config():
         ),
     )
 
+  events_seen_by_agent = []
+
+  class EventCheckingAgent(BaseAgent):
+
+    def __init__(self, name: str):
+      super().__init__(name=name, sub_agents=[])
+
+    async def _run_async_impl(
+        self, invocation_context: InvocationContext
+    ) -> AsyncGenerator[Event, None]:
+      events_seen_by_agent.extend(invocation_context.session.events)
+      yield Event(
+          invocation_id=invocation_context.invocation_id,
+          author=self.name,
+          content=types.Content(
+              role="model", parts=[types.Part(text="Test response")]
+          ),
+      )
+
   runner = Runner(
       app_name=TEST_APP_ID,
-      agent=MockAgent("test_agent"),
+      agent=EventCheckingAgent("test_agent"),
       session_service=session_service,
       artifact_service=InMemoryArtifactService(),
   )
@@ -1720,6 +1739,13 @@ async def test_run_async_passes_get_session_config():
   assert len(events) >= 1
   assert events[0].author == "test_agent"
 
+  # The agent should have only seen 3 historical events + 1 new message = 4 events.
+  assert len(events_seen_by_agent) == 4
+  assert events_seen_by_agent[0].invocation_id == "inv_7"
+  assert events_seen_by_agent[1].invocation_id == "inv_8"
+  assert events_seen_by_agent[2].invocation_id == "inv_9"
+  assert events_seen_by_agent[3].content.parts[0].text == "hello"
+
 
 @pytest.mark.asyncio
 async def test_run_async_teardown_on_aclose():