Fix BatchEndpoint.defaults regression: restore attribute-access object from get()

sdk/ml/azure-ai-ml/CHANGELOG.md

@@ -11,7 +11,7 @@
 ## 1.34.1 (unreleased)
 
 ### Bugs Fixed
-- Fixed `BatchEndpoint` defaults serialization regression where `deployment_name` was sent to the service as snake_case instead of camelCase (`deploymentName`), causing `begin_create_or_update` to fail with "Could not find member 'deployment_name' on object of type 'BatchEndpointDefaults'". `BatchEndpoint.defaults` is now consistently exposed as a snake_case dict to users and converted to the correct wire format on serialization.
+- Fixed `BatchEndpoint` defaults serialization regression where `deployment_name` was sent to the service as snake_case instead of camelCase (`deploymentName`), causing `begin_create_or_update` to fail with "Could not find member 'deployment_name' on object of type 'BatchEndpointDefaults'". Serialization now emits the correct camelCase wire format, while `BatchEndpoint.defaults` returned from `get()` continues to expose an object that supports attribute access (e.g. `endpoint.defaults.deployment_name`), preserving backward compatibility with existing code and samples.
 
 ## 1.34.0 (2026-06-11)
 

sdk/ml/azure-ai-ml/azure/ai/ml/_schema/_endpoint/batch/batch_endpoint_defaults.py

@@ -9,6 +9,7 @@
 
 from marshmallow import fields, post_load
 
+from azure.ai.ml._restclient.arm_ml_service.models import BatchEndpointDefaults
 from azure.ai.ml._schema.core.schema import PatchedSchemaMeta
 
 module_logger = logging.getLogger(__name__)
@@ -24,4 +25,4 @@ class BatchEndpointsDefaultsSchema(metaclass=PatchedSchemaMeta):
 
     @post_load
     def make(self, data: Any, **kwargs: Any) -> Any:
-        return dict(data)
+        return BatchEndpointDefaults(**data)

sdk/ml/azure-ai-ml/azure/ai/ml/entities/_endpoint/batch_endpoint.py

@@ -97,14 +97,12 @@ def _to_rest_batch_endpoint(self, location: str) -> BatchEndpointData:
 
     @classmethod
     def _from_rest_object(cls, obj: BatchEndpointData) -> "BatchEndpoint":
-        defaults: Optional[Dict[str, str]] = None
-        rest_defaults = obj.properties.defaults
-        if isinstance(rest_defaults, RestBatchEndpointDefaults):
-            if rest_defaults.deployment_name is not None:
-                defaults = {"deployment_name": rest_defaults.deployment_name}
-        elif isinstance(rest_defaults, dict):
-            defaults = dict(rest_defaults) if rest_defaults else None
-
+        # Pass the REST ``BatchEndpointDefaults`` object through unchanged so that
+        # ``endpoint.defaults.deployment_name`` remains gettable/settable. Callers
+        # (including the published batch-endpoint sample notebooks) rely on being
+        # able to do ``endpoint.defaults.deployment_name = <name>`` after a get().
+        # Serialization back to camelCase wire format is handled in
+        # ``_to_rest_batch_endpoint`` via the ``RestBatchEndpointDefaults`` branch.
         return BatchEndpoint(
             id=obj.id,
             name=obj.name,
@@ -113,7 +111,7 @@ def _from_rest_object(cls, obj: BatchEndpointData) -> "BatchEndpoint":
             auth_mode=camel_to_snake(obj.properties.auth_mode),
             description=obj.properties.description,
             location=obj.location,
-            defaults=defaults,
+            defaults=obj.properties.defaults,
             provisioning_state=obj.properties.provisioning_state,
             scoring_uri=obj.properties.scoring_uri,
             openapi_uri=obj.properties.swagger_uri,

sdk/ml/azure-ai-ml/tests/batch_online_common/unittests/test_endpoint_entity.py

@@ -205,14 +205,31 @@ def test_to_rest_batch_endpoint_with_no_defaults_passes_none(self) -> None:
 
         assert rest_batch_endpoint.properties.defaults is None
 
-    def test_from_rest_object_defaults_returned_as_snake_case_dict(self) -> None:
+    def test_from_rest_object_defaults_supports_attribute_access(self) -> None:
         with open(TestBatchEndpointYAML.BATCH_ENDPOINT_REST, "r") as f:
             batch_endpoint_rest = _deserialize(BatchEndpointData, json.load(f))
 
         batch_endpoint = BatchEndpoint._from_rest_object(batch_endpoint_rest)
 
-        assert batch_endpoint.defaults == {"deployment_name": "hello-world-1"}
-        assert batch_endpoint.defaults["deployment_name"] == "hello-world-1"
+        # ``endpoint.defaults`` must remain an object that supports attribute
+        # get/set so the published sample pattern keeps working:
+        #     endpoint.defaults.deployment_name = deployment.name
+        assert batch_endpoint.defaults.deployment_name == "hello-world-1"
+
+    def test_from_rest_object_defaults_roundtrips_to_camel_case(self) -> None:
+        with open(TestBatchEndpointYAML.BATCH_ENDPOINT_REST, "r") as f:
+            batch_endpoint_rest = _deserialize(BatchEndpointData, json.load(f))
+
+        batch_endpoint = BatchEndpoint._from_rest_object(batch_endpoint_rest)
+
+        # Emulate the sample notebook flow: mutate the default deployment on the
+        # object returned by get() and serialize it back to the wire format.
+        batch_endpoint.defaults.deployment_name = "hello-world-2"
+        rest_batch_endpoint = batch_endpoint._to_rest_batch_endpoint("eastus")
+
+        rest_defaults = rest_batch_endpoint.properties.defaults
+        assert rest_defaults.deployment_name == "hello-world-2"
+        assert rest_defaults.as_dict() == {"deploymentName": "hello-world-2"}
 
 
 class TestKubernetesOnlineEndopint: