From 80b1b9b1889845eb686dd64691a14656c21b8a66 Mon Sep 17 00:00:00 2001
From: Mateo Wang <277851410+mateo-berri@users.noreply.github.com>
Date: Thu, 5 Nov 2026 16:50:53 -0800
Subject: [PATCH] fix(router): let type checkers see the real Router
 constructor arguments (#50278)

---
 .../management_endpoints/router_settings_endpoints.py |  2 +-
 litellm/router.py                                     | 11 ++++++++---
 litellm/router_utils/handle_error.py                  |  4 ++--
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/litellm/proxy/management_endpoints/router_settings_endpoints.py b/litellm/proxy/management_endpoints/router_settings_endpoints.py
index 9951891fd07..013eb1ebff4 100644
--- a/litellm/proxy/management_endpoints/router_settings_endpoints.py
+++ b/litellm/proxy/management_endpoints/router_settings_endpoints.py
@@ -68,7 +68,7 @@ def _get_routing_strategies_from_router_class() -> list[str]:
     Dynamically extract routing strategies from the Router class __init__ method.
     """
     # Get the __init__ signature
-    sig: Final = inspect.signature(Router.__init__)
+    sig: Final = inspect.signature(Router)
 
     # Get the routing_strategy parameter
     routing_strategy_param: Final = sig.parameters.get("routing_strategy")
diff --git a/litellm/router.py b/litellm/router.py
index a5d72daea1e..4b51c16aa81 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -52,7 +52,7 @@ if TYPE_CHECKING:
 # ``Router(...)``'s parameters, their defaults and its docstring: ``router_arguments`` binds a call
 # against them and ``Router.__init__`` reports them. The body is never run.
 def _router_init(
-    self,
+    self: object,
     model_list: list[DeploymentTypedDict] | list[dict[str, Any]] | None = None,
     ## ASSISTANTS API ##
     assistants_config: AssistantsTypedDict | None = None,
@@ -222,17 +222,22 @@ def _class_descriptor(cls: type, name: str) -> bool:
 
 
 if TYPE_CHECKING:
-    from typing import overload
+    from typing import ParamSpec, overload
 
     from litellm.litellm_core_utils.streaming_handler import CustomStreamWrapper
     from litellm.types.llms.openai import AllMessageValues, OpenAIFileObject
     from litellm.types.utils import EmbeddingResponse, LiteLLMBatch, ModelResponse
 
+    _P: Final = ParamSpec("_P")
+
+    def _takes_parameters_of(source: Callable[_P, None]) -> Callable[[Callable[..., None]], Callable[_P, None]]: ...
+
     class Router(RustCore, DeprecatedRouterMembers):
         """What type checkers see: the constructor's parameters and the endpoints' return types. The
         endpoints are served by the core at run time (litellm/router_rust/invoke/endpoints.py)."""
 
-        __init__ = _router_init  # pyright: ignore[reportAssignmentType, reportIncompatibleMethodOverride]  # Router(...)'s parameters
+        @_takes_parameters_of(_router_init)
+        def __init__(self) -> None: ...  # pyright: ignore[reportMissingSuperCall]  # a type-checking stub
 
         @classmethod
         def from_config(cls, config: RouterConfig, host: PythonHost = python_host) -> "Router": ...
diff --git a/litellm/router_utils/handle_error.py b/litellm/router_utils/handle_error.py
index 6033024123f..97bf4710fca 100644
--- a/litellm/router_utils/handle_error.py
+++ b/litellm/router_utils/handle_error.py
@@ -26,7 +26,7 @@ async def send_llm_exception_alert(
     ctx: "RoutingContext | None",
     request_kwargs: dict,
     error_traceback_str: str,
-    original_exception,
+    original_exception: Exception,
 ):
     """
     Only runs if router.slack_alerting_logger is set
@@ -34,7 +34,7 @@ async def send_llm_exception_alert(
 
     Parameters:
         ctx (RoutingContext): The router's routing context.
-        original_exception (Any): The original exception that occurred.
+        original_exception (Exception): The original exception that occurred.
 
     Returns:
         None