fix: replace mutable default arguments (= [] and = {}) with None

Mutable default arguments in Python are shared across all calls,
causing subtle state-leak bugs. Replaced with Optional[...] = None
and initialized inside the function body.

Affected:
- utils.decode(): tokens: List[int] = [] -> Optional[List[int]] = None
- VectorStoreRegistry.__init__(): vector_stores = [] -> None
- get_litellm_model_info(): model: dict = {} -> Optional[dict] = None
- LowestCostLoggingHandler.__init__(): routing_args = {} -> None
- LowestLatencyLoggingHandler.__init__(): routing_args = {} -> None
- LowestTPM_RPM_Routing.__init__(): routing_args = {} -> None
- LowestTPM_RPM_Routing_v2.__init__(): routing_args = {} -> None

litellm/proxy/proxy_server.py

@@ -5954,7 +5954,9 @@ def select_data_generator(
     )
 
 
-def get_litellm_model_info(model: dict = {}):
+def get_litellm_model_info(model: Optional[dict] = None):
+    if model is None:
+        model = {}
     model_info = model.get("model_info", {})
     model_to_lookup = model.get("litellm_params", {}).get("model", None)
     try:

litellm/router_strategy/lowest_cost.py

@@ -15,7 +15,7 @@ class LowestCostLoggingHandler(CustomLogger):
     logged_success: int = 0
     logged_failure: int = 0
 
-    def __init__(self, router_cache: DualCache, routing_args: dict = {}):
+    def __init__(self, router_cache: DualCache, routing_args: Optional[dict] = None):
         self.router_cache = router_cache
 
     def log_success_event(self, kwargs, response_obj, start_time, end_time):

litellm/router_strategy/lowest_latency.py

@@ -31,8 +31,10 @@ class LowestLatencyLoggingHandler(CustomLogger):
     logged_success: int = 0
     logged_failure: int = 0
 
-    def __init__(self, router_cache: DualCache, routing_args: dict = {}):
+    def __init__(self, router_cache: DualCache, routing_args: Optional[dict] = None):
         self.router_cache = router_cache
+        if routing_args is None:
+            routing_args = {}
         self.routing_args = RoutingArgs(**routing_args)
 
     def log_success_event(  # noqa: PLR0915

litellm/router_strategy/lowest_tpm_rpm.py

@@ -22,8 +22,10 @@ class LowestTPMLoggingHandler(CustomLogger):
     logged_failure: int = 0
     default_cache_time_seconds: int = 1 * 60 * 60  # 1 hour
 
-    def __init__(self, router_cache: DualCache, routing_args: dict = {}):
+    def __init__(self, router_cache: DualCache, routing_args: Optional[dict] = None):
         self.router_cache = router_cache
+        if routing_args is None:
+            routing_args = {}
         self.routing_args = RoutingArgs(**routing_args)
 
     def log_success_event(self, kwargs, response_obj, start_time, end_time):

litellm/router_strategy/lowest_tpm_rpm_v2.py

@@ -47,8 +47,10 @@ class LowestTPMLoggingHandler_v2(BaseRoutingStrategy, CustomLogger):
     logged_failure: int = 0
     default_cache_time_seconds: int = 1 * 60 * 60  # 1 hour
 
-    def __init__(self, router_cache: DualCache, routing_args: dict = {}):
+    def __init__(self, router_cache: DualCache, routing_args: Optional[dict] = None):
         self.router_cache = router_cache
+        if routing_args is None:
+            routing_args = {}
         self.routing_args = RoutingArgs(**routing_args)
         BaseRoutingStrategy.__init__(
             self,

litellm/utils.py

@@ -2236,7 +2236,9 @@ def encode(model="", text="", custom_tokenizer: Optional[dict] = None):
     return enc
 
 
-def decode(model="", tokens: List[int] = [], custom_tokenizer: Optional[dict] = None):
+def decode(model="", tokens: Optional[List[int]] = None, custom_tokenizer: Optional[dict] = None):
+    if tokens is None:
+        tokens = []
     tokenizer_json = custom_tokenizer or _select_tokenizer(model=model)
     dec = tokenizer_json["tokenizer"].decode(tokens)
     return dec

litellm/vector_stores/vector_store_registry.py

@@ -106,8 +106,8 @@ class VectorStoreIndexRegistry:
 
 
 class VectorStoreRegistry:
-    def __init__(self, vector_stores: List[LiteLLM_ManagedVectorStore] = []):
-        self.vector_stores: List[LiteLLM_ManagedVectorStore] = vector_stores
+    def __init__(self, vector_stores: Optional[List[LiteLLM_ManagedVectorStore]] = None):
+        self.vector_stores: List[LiteLLM_ManagedVectorStore] = vector_stores or []
         self.vector_store_ids_to_vector_store_map: Dict[
             str, LiteLLM_ManagedVectorStore
         ] = {}