fix: support us region routing

PiperOrigin-RevId: 890026941

Author: google-genai-bot

google/genai/_api_client.py

@@ -702,6 +702,10 @@ def __init__(
           self.api_key or self.location == 'global'
       ) and not self.custom_base_url:
         self._http_options.base_url = f'https://aiplatform.googleapis.com/'
+      elif self.location == 'us' and not self.custom_base_url:
+        self._http_options.base_url = (
+            f'https://aiplatform.{self.location}.rep.googleapis.com/'
+        )
       elif (
           self.custom_base_url
           and not self.custom_base_url.endswith('.googleapis.com')

google/genai/tests/client/test_client_initialization.py

@@ -516,6 +516,43 @@ def test_vertexai_no_default_location_when_location_explicitly_set(monkeypatch):
     assert client.models._api_client.project == project_id
 
 
+def test_vertexai_location_us_routing(monkeypatch):
+  # Verify that location='us' correctly routes to the us.rep endpoint
+  project_id = "fake_project_id"
+  location = "us"
+
+  with monkeypatch.context() as m:
+    m.delenv("GOOGLE_CLOUD_LOCATION", raising=False)
+    client = Client(vertexai=True, project=project_id, location=location)
+    assert client.models._api_client.location == location
+    assert client.models._api_client.project == project_id
+    assert (
+        client.models._api_client.get_read_only_http_options()["base_url"]
+        == "https://aiplatform.us.rep.googleapis.com/"
+    )
+
+
+def test_vertexai_location_us_routing_base_url_override(monkeypatch):
+  # Verify that base_url override takes precedence over location='us' routing
+  project_id = "fake_project_id"
+  location = "us"
+
+  with monkeypatch.context() as m:
+    m.delenv("GOOGLE_CLOUD_LOCATION", raising=False)
+    client = Client(
+        vertexai=True,
+        project=project_id,
+        location=location,
+        http_options={"base_url": "https://my-custom-url.com/"},
+    )
+    assert client.models._api_client.location == location
+    assert client.models._api_client.project == project_id
+    assert (
+        client.models._api_client.get_read_only_http_options()["base_url"]
+        == "https://my-custom-url.com/"
+    )
+
+
 def test_vertexai_no_default_location_when_env_location_set(monkeypatch):
   # Verify that location is NOT defaulted to global when set via environment
   project_id = "fake_project_id"