diff --git a/litellm/router_strategy/complexity_router/complexity_router.py b/litellm/router_strategy/complexity_router/complexity_router.py
index d6f67120cef..ccded64c3a5 100644
--- a/litellm/router_strategy/complexity_router/complexity_router.py
+++ b/litellm/router_strategy/complexity_router/complexity_router.py
@@ -1156,18 +1156,12 @@ class ComplexityRouter(CustomLogger):
     def _pick_from_tier_value(
         model: str | list[str] | TierTarget, tier_key: str
     ) -> str:  # mutable-ok: legacy pool inputs remain lists
-        if isinstance(model, TierTarget):
-            target_model: Final = model.model
-            if isinstance(target_model, str):
-                return target_model
-            if not target_model:
-                raise ValueError(f"Empty model pool for tier {tier_key}")
-            return random.choice(target_model)
         if isinstance(model, str):
             return model
-        if not model:
+        pool: Final = tier_pool(model)
+        if not pool:
             raise ValueError(f"Empty model pool for tier {tier_key}")
-        return random.choice(model)
+        return random.choice(pool)
 
     def _tier_pools(self) -> dict[str, list[str]]:  # mutable-ok: adaptive router consumes mutable pools
         return {  # mutable-ok: router consumers require mutable tier pool mappings
diff --git a/tests/test_litellm/router_strategy/test_complexity_router.py b/tests/test_litellm/router_strategy/test_complexity_router.py
index b37c574b5b0..7cb402969ab 100644
--- a/tests/test_litellm/router_strategy/test_complexity_router.py
+++ b/tests/test_litellm/router_strategy/test_complexity_router.py
@@ -913,7 +913,10 @@ class TestSingletonMutation:
 
     def test_default_config_not_mutated(self, mock_router_instance):
         """Test that creating routers without config doesn't mutate defaults."""
-        from litellm.router_strategy.complexity_router.config import ComplexityRouterConfig
+        from litellm.router_strategy.complexity_router.config import (
+            DEFAULT_CLASSIFIER_CONTEXT_WINDOW_SIZE,
+            ComplexityRouterConfig,
+        )
 
         # Get original default
         original_default = ComplexityRouterConfig().default_model