fix(proxy): allow clearing empty-collection user fields via /user/update

_update_internal_user_params dumps the request with exclude_unset and then
discards any value equal to [] or {}, so an explicitly sent empty collection
never reached the database. Because exclude_unset already drops fields the
caller never sent, that filter only ever fired on values set on purpose,
leaving a user's old models, allowed_cache_controls and model_max_budget in
place after a clear attempt. Route those real user columns through the same
fields_set check max_budget already uses so an explicit empty value is written.

config, permissions and aliases are not user-table columns, so they keep going
through the empty-collection filter and never reach Prisma.

litellm/proxy/management_endpoints/internal_user_endpoints.py

@@ -1127,6 +1127,15 @@ def _process_keys_for_user_info(
     return returned_keys
 
 
+# Real LiteLLM_UserTable columns whose empty value ([] / {}) is a deliberate
+# "clear it". The caller dumps with exclude_unset, so an empty value here always
+# means the field was sent on purpose and must reach the DB instead of being
+# dropped by the generic empty-collection filter below.
+USER_FIELDS_CLEARABLE_WHEN_SET = frozenset(
+    {"models", "allowed_cache_controls", "model_max_budget"}
+)
+
+
 def _update_internal_user_params(
     data_json: dict, data: Union[UpdateUserRequest, UpdateUserRequestNoUserIDorEmail]
 ) -> dict:
@@ -1137,6 +1146,9 @@ def _update_internal_user_params(
         if k == "max_budget":
             if "max_budget" in fields_set:
                 non_default_values[k] = v
+        elif k in USER_FIELDS_CLEARABLE_WHEN_SET:
+            if k in fields_set:
+                non_default_values[k] = v
         elif (
             v is not None
             and v
@@ -1145,7 +1157,7 @@ def _update_internal_user_params(
                 {},
             )
             and k not in LiteLLM_ManagementEndpoint_MetadataFields
-        ):  # models default to [], spend defaults to 0, we should not reset these values
+        ):  # drop [] / {} so list/dict fields left unset aren't reset to empty
             non_default_values[k] = v
 
     is_internal_user = False

tests/test_litellm/proxy/management_endpoints/test_internal_user_endpoints.py

@@ -1696,6 +1696,52 @@ def test_update_internal_user_params_keeps_original_max_budget_when_not_provided
     assert "user_alias" in non_default_values
 
 
+@pytest.mark.parametrize(
+    "field, empty_value",
+    [
+        ("models", []),
+        ("allowed_cache_controls", []),
+        ("model_max_budget", {}),
+    ],
+)
+def test_update_internal_user_params_clears_empty_collection_field(field, empty_value):
+    """
+    Regression for LIT-3888: an explicitly provided empty list/dict for a real
+    user column must reach the DB update so the field can be cleared via
+    /user/update. Previously [] / {} were filtered out as "defaults" and the old
+    values persisted.
+    """
+    data = UpdateUserRequest(user_id="test_user", **{field: empty_value})
+    data_json = data.model_dump(exclude_unset=True)
+
+    non_default_values = _update_internal_user_params(data_json=data_json, data=data)
+
+    assert field in non_default_values
+    assert non_default_values[field] == empty_value
+
+
+def test_update_internal_user_params_sets_personal_models():
+    """A non-empty models list is still applied unchanged."""
+    data = UpdateUserRequest(user_id="test_user", models=["gpt-4o"])
+    data_json = data.model_dump(exclude_unset=True)
+
+    non_default_values = _update_internal_user_params(data_json=data_json, data=data)
+
+    assert non_default_values["models"] == ["gpt-4o"]
+
+
+def test_update_internal_user_params_keeps_clearable_fields_when_not_provided():
+    """When a clearable field is omitted, its column must be left untouched."""
+    data = UpdateUserRequest(user_id="test_user", user_alias="test_alias")
+    data_json = data.model_dump(exclude_unset=True)
+
+    non_default_values = _update_internal_user_params(data_json=data_json, data=data)
+
+    assert "models" not in non_default_values
+    assert "allowed_cache_controls" not in non_default_values
+    assert "model_max_budget" not in non_default_values
+
+
 def test_generate_request_base_validator():
     """
     Test that GenerateRequestBase validator converts empty string to None for max_budget