Fix AttributeError when metadata is null in request body (#17263) (#17306)

Handle the case where metadata is explicitly set to null/None in the
request body. This was causing a 401 error with "'NoneType' object
has no attribute 'get'" when calling /v1/batches with metadata: null.

The fix uses `or {}` instead of a default dict value since the key
exists but has a None value.

litellm/proxy/common_utils/http_parsing_utils.py

@@ -309,7 +309,7 @@ def get_tags_from_request_body(request_body: dict) -> List[str]:
         List of tag names (strings), empty list if no valid tags found
     """
     metadata_variable_name = get_metadata_variable_name_from_kwargs(request_body)
-    metadata = request_body.get(metadata_variable_name, {})
+    metadata = request_body.get(metadata_variable_name) or {}
     tags_in_metadata: Any = metadata.get("tags", [])
     tags_in_request_body: Any = request_body.get("tags", [])
     combined_tags: List[str] = []

tests/test_litellm/proxy/common_utils/test_http_parsing_utils.py

@@ -606,8 +606,27 @@ def test_get_tags_from_request_body_with_dict_tags():
             }
         }
     }
-    
+
     result = get_tags_from_request_body(request_body=request_body)
-    
+
+    assert result == []
+    assert isinstance(result, list)
+
+
+def test_get_tags_from_request_body_with_null_metadata():
+    """
+    Test that function handles null metadata gracefully without crashing.
+
+    This is a regression test for https://github.com/BerriAI/litellm/issues/17263
+    When metadata is explicitly set to null/None, the function should return
+    an empty list instead of raising AttributeError.
+    """
+    request_body = {
+        "model": "gpt-4",
+        "metadata": None  # OpenAI API accepts metadata: null
+    }
+
+    result = get_tags_from_request_body(request_body=request_body)
+
     assert result == []
     assert isinstance(result, list)