diff --git a/litellm/proxy/route_llm_request.py b/litellm/proxy/route_llm_request.py
index f611384b7ae..bfe6b8484fa 100644
--- a/litellm/proxy/route_llm_request.py
+++ b/litellm/proxy/route_llm_request.py
@@ -1,17 +1,21 @@
 import asyncio
-from dataclasses import fields as _dc_fields
 from typing import TYPE_CHECKING, Any, Literal, Optional
 
 from fastapi import HTTPException, status
 
 import litellm
 from litellm.proxy._types import UserAPIKeyAuth
-from litellm.types.router import MockRouterTestingParams
 
-# Router-internal mock_testing_* flag names. Single source of truth so a
-# new flag added to ``MockRouterTestingParams`` is automatically stripped.
-_MOCK_TESTING_KWARG_NAMES: tuple = tuple(
-    f.name for f in _dc_fields(MockRouterTestingParams)
+# Router-internal mock_testing_* flag names — kept in sync with
+# ``litellm.types.router.MockRouterTestingParams`` by the test
+# ``test_mock_testing_kwarg_names_matches_dataclass``. Hardcoding (rather
+# than deriving via ``dataclasses.fields(MockRouterTestingParams)`` at
+# import time) avoids a cyclic import: ``litellm.types.router`` imports
+# back into proxy modules before this module finishes loading.
+_MOCK_TESTING_KWARG_NAMES: tuple = (
+    "mock_testing_fallbacks",
+    "mock_testing_context_fallbacks",
+    "mock_testing_content_policy_fallbacks",
 )
 
 if TYPE_CHECKING:
diff --git a/tests/test_litellm/proxy/test_route_llm_request.py b/tests/test_litellm/proxy/test_route_llm_request.py
index 9ef90085e41..98b0b6be025 100644
--- a/tests/test_litellm/proxy/test_route_llm_request.py
+++ b/tests/test_litellm/proxy/test_route_llm_request.py
@@ -241,6 +241,21 @@ async def test_route_request_with_router_settings_override_preserves_existing():
     assert call_kwargs["timeout"] == 30
 
 
+def test_mock_testing_kwarg_names_matches_dataclass():
+    """``_MOCK_TESTING_KWARG_NAMES`` is hardcoded to avoid a cyclic import
+    against ``litellm.types.router``. This test guards against drift —
+    if a new ``mock_testing_*`` field is added to ``MockRouterTestingParams``
+    the strip list must be updated to keep covering it."""
+    from dataclasses import fields
+
+    from litellm.proxy.route_llm_request import _MOCK_TESTING_KWARG_NAMES
+    from litellm.types.router import MockRouterTestingParams
+
+    assert set(_MOCK_TESTING_KWARG_NAMES) == {
+        f.name for f in fields(MockRouterTestingParams)
+    }
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     "mock_flag",