fix: unbreak client closed errors when using vertexai session service

PiperOrigin-RevId: 811911528

pyproject.toml

@@ -38,8 +38,7 @@ dependencies = [
   "google-cloud-spanner>=3.56.0, <4.0.0",                   # For Spanner database
   "google-cloud-speech>=2.30.0, <3.0.0",                    # For Audio Transcription
   "google-cloud-storage>=2.18.0, <3.0.0",                   # For GCS Artifact service
-  # TODO: Modify genai version constraint after the connector/client session warning is fixed.
-  "google-genai>=1.21.1, <1.37.0",                           # Google GenAI SDK
+  "google-genai>=1.21.1, <=1.40.0, !=1.37.0, !=1.38.0, !=1.39.0",                           # Google GenAI SDK
   "graphviz>=0.20.2, <1.0.0",                               # Graphviz for graph rendering
   "mcp>=1.8.0, <2.0.0;python_version>='3.10'",              # For MCP Toolset
   "opentelemetry-api>=1.37.0, <=1.37.0",                    # OpenTelemetry - limit upper version for sdk and api to not risk breaking changes from unstable _logs package.

src/google/adk/sessions/vertex_ai_session_service.py

@@ -371,15 +371,15 @@ class VertexAiSessionService(BaseSessionService):
   ) -> Optional[genai.types.HttpOptions]:
     return None
 
-  def _get_api_client(self):
+  def _get_api_client(self) -> genai.client.BaseApiClient:
     """Instantiates an API client for the given project and location.
 
     It needs to be instantiated inside each request so that the event loop
     management can be properly propagated.
     """
-    api_client = genai.Client(
+    api_client = genai.client.BaseApiClient(
         vertexai=True, project=self._project, location=self._location
-    )._api_client
+    )
 
     if new_options := self._api_client_http_options_override():
       api_client._http_options = new_options