diff --git a/tests/unit/vertexai/genai/replays/test_create_agent_engine_session.py b/tests/unit/vertexai/genai/replays/test_create_agent_engine_session.py
index b055a9b67c..3f3dc0e142 100644
--- a/tests/unit/vertexai/genai/replays/test_create_agent_engine_session.py
+++ b/tests/unit/vertexai/genai/replays/test_create_agent_engine_session.py
@@ -32,7 +32,7 @@ def test_create_session_with_ttl(client):
             config=types.CreateAgentEngineSessionConfig(
                 display_name="my_session",
                 session_state={"foo": "bar"},
-                ttl="120s",
+                ttl="1200000s",
                 labels={"label_key": "label_value"},
             ),
         )
@@ -42,12 +42,13 @@ def test_create_session_with_ttl(client):
         assert operation.response.user_id == "test-user-123"
         assert operation.response.labels == {"label_key": "label_value"}
         assert operation.response.name.startswith(agent_engine.api_resource.name)
+        assert operation.done
         # Expire time is calculated by the server, so we only check that it is
         # within a reasonable range to avoid flakiness.
         assert (
-            operation.response.create_time + datetime.timedelta(seconds=119.5)
+            operation.response.create_time + datetime.timedelta(seconds=1199999.5)
             <= operation.response.expire_time
-            <= operation.response.create_time + datetime.timedelta(seconds=120.5)
+            <= operation.response.create_time + datetime.timedelta(seconds=1200000.5)
         )
     finally:
         # Clean up resources.
@@ -60,7 +61,7 @@ def test_create_session_with_expire_time(client):
         assert isinstance(agent_engine, types.AgentEngine)
         assert isinstance(agent_engine.api_resource, types.ReasoningEngine)
         expire_time = datetime.datetime(
-            2026, 1, 1, 12, 30, 00, tzinfo=datetime.timezone.utc
+            2028, 1, 1, 12, 30, 00, tzinfo=datetime.timezone.utc
         )
 
         operation = client.agent_engines.sessions.create(
@@ -78,6 +79,7 @@ def test_create_session_with_expire_time(client):
         assert operation.response.user_id == "test-user-123"
         assert operation.response.name.startswith(agent_engine.api_resource.name)
         assert operation.response.expire_time == expire_time
+        assert operation.done
     finally:
         # Clean up resources.
         client.agent_engines.delete(name=agent_engine.api_resource.name, force=True)
diff --git a/vertexai/_genai/sessions.py b/vertexai/_genai/sessions.py
index 777bcf56a9..43c5bf64b5 100644
--- a/vertexai/_genai/sessions.py
+++ b/vertexai/_genai/sessions.py
@@ -651,12 +651,15 @@ def create(
             user_id=user_id,
             config=config,
         )
-        if config.wait_for_completion and not operation.done:
-            operation = _agent_engines_utils._await_operation(
-                operation_name=operation.name,
-                get_operation_fn=self._get_session_operation,
-                poll_interval_seconds=0.5,
-            )
+        if config.wait_for_completion:
+            if not operation.done:
+                operation = _agent_engines_utils._await_operation(
+                    operation_name=operation.name,
+                    get_operation_fn=self._get_session_operation,
+                    poll_interval_seconds=0.5,
+                )
+            # We need to make a call to get the session because the operation
+            # response might not contain the relevant fields.
             if operation.response:
                 operation.response = self.get(name=operation.response.name)
             elif operation.error:
@@ -1133,12 +1136,15 @@ async def create(
             user_id=user_id,
             config=config,
         )
-        if config.wait_for_completion and not operation.done:
-            operation = await _agent_engines_utils._await_async_operation(
-                operation_name=operation.name,
-                get_operation_fn=self._get_session_operation,
-                poll_interval_seconds=0.5,
-            )
+        if config.wait_for_completion:
+            if not operation.done:
+                operation = await _agent_engines_utils._await_async_operation(
+                    operation_name=operation.name,
+                    get_operation_fn=self._get_session_operation,
+                    poll_interval_seconds=0.5,
+                )
+            # We need to make a call to get the session because the operation
+            # response might not contain the relevant fields.
             if operation.response:
                 operation.response = await self.get(name=operation.response.name)
             elif operation.error: