diff --git a/google/genai/models.py b/google/genai/models.py
index 7a35a8b6c..8c7509c9f 100644
--- a/google/genai/models.py
+++ b/google/genai/models.py
@@ -4548,6 +4548,12 @@ def _UpdateModelConfig_to_mldev(
         getv(from_object, ['default_checkpoint_id']),
     )
 
+  if getv(from_object, ['update_mask']) is not None:
+    raise ValueError(
+        'update_mask parameter is only supported in Gemini Enterprise Agent'
+        ' Platform mode, not in Gemini Developer API mode.'
+    )
+
   return to_object
 
 
@@ -4571,6 +4577,13 @@ def _UpdateModelConfig_to_vertex(
         getv(from_object, ['default_checkpoint_id']),
     )
 
+  if getv(from_object, ['update_mask']) is not None:
+    setv(
+        parent_object,
+        ['_query', 'updateMask'],
+        getv(from_object, ['update_mask']),
+    )
+
   return to_object
 
 
diff --git a/google/genai/types.py b/google/genai/types.py
index e0dcee515..1ee18d0fd 100644
--- a/google/genai/types.py
+++ b/google/genai/types.py
@@ -10703,6 +10703,7 @@ class UpdateModelConfig(_common.BaseModel):
   display_name: Optional[str] = Field(default=None, description="""""")
   description: Optional[str] = Field(default=None, description="""""")
   default_checkpoint_id: Optional[str] = Field(default=None, description="""""")
+  update_mask: Optional[str] = Field(default=None, description="""""")
 
 
 class UpdateModelConfigDict(TypedDict, total=False):
@@ -10720,6 +10721,9 @@ class UpdateModelConfigDict(TypedDict, total=False):
   default_checkpoint_id: Optional[str]
   """"""
 
+  update_mask: Optional[str]
+  """"""
+
 
 UpdateModelConfigOrDict = Union[UpdateModelConfig, UpdateModelConfigDict]