fix(llm-router): address Copilot review comments

Applied Copilot security/quality recommendations:

1. Fixed mutable default arguments - Changed `connection_kwargs: Dict[str, Any] = {}`
   to `Optional[Dict[str, Any]] = None` in LLMRouter.__init__ and SemanticRouter.__init__
   to avoid shared state across instances.

2. Added empty routes guard - Added `if not self.routes: return []` check in
   both sync and async `_get_route_matches()` to prevent ValueError when calling
   `max(route.distance_threshold for route in self.routes)` on empty sequence.

These changes address the same issues that were fixed in the original LLMRouter
implementation (commits e1cd469 and 9cba561), ensuring consistency across
the refactored codebase.

All 86 router tests passing.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: bsbodden

redisvl/extensions/llm_router/__init__.py

@@ -79,7 +79,7 @@ def __init__(
         redis_url: str = "redis://localhost:6379",
         overwrite: bool = False,
         cost_optimization: bool = False,
-        connection_kwargs: Dict[str, Any] = {},
+        connection_kwargs: Optional[Dict[str, Any]] = None,
         **kwargs,
     ):
         """Initialize LLMRouter (deprecated, use SemanticRouter).
@@ -110,6 +110,10 @@ def __init__(
 
             routing_config = RoutingConfig(cost_optimization=True)
 
+        # Handle mutable default
+        if connection_kwargs is None:
+            connection_kwargs = {}
+
         # Call parent __init__
         super().__init__(
             name=name,

redisvl/extensions/router/semantic.py

@@ -56,7 +56,7 @@ def __init__(
         redis_client: Optional[SyncRedisClient] = None,
         redis_url: str = "redis://localhost:6379",
         overwrite: bool = False,
-        connection_kwargs: Dict[str, Any] = {},
+        connection_kwargs: Optional[Dict[str, Any]] = None,
         **kwargs,
     ):
         """Initialize the SemanticRouter.
@@ -96,6 +96,9 @@ def __init__(
         if routing_config is None:
             routing_config = RoutingConfig()
 
+        if connection_kwargs is None:
+            connection_kwargs = {}
+
         super().__init__(
             name=name,
             routes=routes,
@@ -386,6 +389,8 @@ def _get_route_matches(
         max_k: int = 1,
     ) -> List[RouteMatch]:
         """Get route response from vector db"""
+        if not self.routes:
+            return []
 
         # what's interesting about this is that we only provide one distance_threshold for a range query not multiple
         # therefore you might take the max_threshold and further refine from there.
@@ -1438,6 +1443,8 @@ async def _get_route_matches(
         max_k: int = 1,
     ) -> List[RouteMatch]:
         """Get route response from vector db (async)"""
+        if not self.routes:
+            return []
 
         # what's interesting about this is that we only provide one distance_threshold for a range query not multiple
         # therefore you might take the max_threshold and further refine from there.