fix: Built-in agents (names starting with "__") now use in-memory session storage instead of creating .adk folders in the agents directory

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 845852695

src/google/adk/cli/utils/local_storage.py

@@ -34,6 +34,8 @@ from .dot_adk_folder import DotAdkFolder
 
 logger = logging.getLogger("google_adk." + __name__)
 
+_BUILT_IN_SESSION_SERVICE_KEY = "__adk_built_in_session_service__"
+
 
 def create_local_database_session_service(
     *,
@@ -124,6 +126,16 @@ class PerAgentDatabaseSessionService(BaseSessionService):
 
   async def _get_service(self, app_name: str) -> BaseSessionService:
     async with self._service_lock:
+      if app_name.startswith("__"):
+        service = self._services.get(_BUILT_IN_SESSION_SERVICE_KEY)
+        if service is not None:
+          return service
+        service = create_local_database_session_service(
+            base_dir=self._agents_root,
+        )
+        self._services[_BUILT_IN_SESSION_SERVICE_KEY] = service
+        return service
+
       storage_name = self._app_name_to_dir.get(app_name, app_name)
       service = self._services.get(storage_name)
       if service is not None:

tests/unittests/cli/utils/test_local_storage.py

@@ -72,6 +72,18 @@ async def test_per_agent_session_service_respects_app_name_alias(
   assert (tmp_path / folder_name / ".adk" / "session.db").exists()
 
 
+@pytest.mark.asyncio
+async def test_per_agent_session_service_routes_built_in_agents_to_root_dot_adk(
+    tmp_path: Path,
+) -> None:
+  service = PerAgentDatabaseSessionService(agents_root=tmp_path)
+
+  await service.create_session(app_name="__helper", user_id="user")
+
+  assert not (tmp_path / "__helper").exists()
+  assert (tmp_path / ".adk" / "session.db").exists()
+
+
 def test_create_local_database_session_service_returns_sqlite(
     tmp_path: Path,
 ) -> None: