refactor(proxy): move UNMATCHED_REQUEST_ROUTE to constants

Centralize the Prometheus unmatched-route sentinel in constants.py
so metrics paths share one canonical value.

litellm/constants.py

@@ -1334,6 +1334,8 @@ LITELLM_TRUNCATION_DB_SAFEGUARD_NOTE: Final = (
 ########################### LiteLLM Proxy Specific Constants ###########################
 ########################################################################################
 
+UNMATCHED_REQUEST_ROUTE: Final = "/unmatched"
+
 # Standard headers that are always checked for customer/end-user ID (no configuration required)
 # These headers work out-of-the-box for tools like Claude Code that support custom headers
 STANDARD_CUSTOMER_ID_HEADERS: Final = [

litellm/proxy/auth/auth_utils.py

@@ -11,7 +11,7 @@ from fastapi import HTTPException, Request, status
 import litellm
 from litellm import Router, provider_list
 from litellm._logging import verbose_proxy_logger
-from litellm.constants import MINIMUM_CUSTOM_KEY_LENGTH, STANDARD_CUSTOMER_ID_HEADERS
+from litellm.constants import MINIMUM_CUSTOM_KEY_LENGTH, STANDARD_CUSTOMER_ID_HEADERS, UNMATCHED_REQUEST_ROUTE
 from litellm.litellm_core_utils.safe_json_loads import safe_json_loads
 from litellm.litellm_core_utils.url_utils import (
     SSRFError,
@@ -767,8 +767,6 @@ def normalize_request_route(route: str) -> str:
     return route
 
 
-UNMATCHED_REQUEST_ROUTE: Final = "/unmatched"
-
 # Literal proxy routes safe to emit when FastAPI's route template is unavailable
 # (e.g. auth failure on an unmatched scope). Dynamic segments must never appear
 # here — those are covered by get_request_route_template() or normalize_request_route().

tests/test_litellm/integrations/test_prometheus_labels.py

@@ -451,10 +451,8 @@ def test_route_normalization_preserves_static_routes():
 
 def test_unmatched_scanner_routes_collapse_for_metrics():
     """Unknown paths must not create unbounded Prometheus route labels."""
-    from litellm.proxy.auth.auth_utils import (
-        UNMATCHED_REQUEST_ROUTE,
-        resolve_request_route_for_metrics,
-    )
+    from litellm.constants import UNMATCHED_REQUEST_ROUTE
+    from litellm.proxy.auth.auth_utils import resolve_request_route_for_metrics
 
     scanner_paths = [
         "/files/pRzAdaV1.php",

tests/test_litellm/proxy/auth/test_auth_utils.py

@@ -2951,10 +2951,8 @@ class TestResolveRequestRouteForMetrics:
             assert resolve_request_route_for_metrics(None, route) == route
 
     def test_collapses_unknown_paths_to_unmatched(self):
-        from litellm.proxy.auth.auth_utils import (
-            UNMATCHED_REQUEST_ROUTE,
-            resolve_request_route_for_metrics,
-        )
+        from litellm.constants import UNMATCHED_REQUEST_ROUTE
+        from litellm.proxy.auth.auth_utils import resolve_request_route_for_metrics
 
         scanner_paths = [
             "/files/pRzAdaV1.php",