fix(router): guard the declared-provider check for requests without a model

litellm/litellm_core_utils/get_llm_provider_logic.py

@@ -127,7 +127,7 @@ def handle_anthropic_text_model_custom_llm_provider(
     return model, custom_llm_provider
 
 
-def declared_authenticating_provider(model: str, custom_llm_provider: str | None = None) -> str | None:
+def declared_authenticating_provider(model: str | None, custom_llm_provider: str | None = None) -> str | None:
     """The authenticating provider this pair already names, or None.
 
     get_llm_provider runs the OAuth device flow for github_copilot and chatgpt, because their
@@ -135,7 +135,7 @@ def declared_authenticating_provider(model: str, custom_llm_provider: str | None
     and for a declared pair the resolver's answer is the declaration itself, so metadata callers
     adopt the declaration instead of resolving.
     """
-    declared: Final = custom_llm_provider or (model.split("/", 1)[0] if "/" in model else None)
+    declared: Final = custom_llm_provider or (model.split("/", 1)[0] if model and "/" in model else None)
     return declared if declared in PROVIDERS_THAT_AUTHENTICATE_ON_PROVIDER_INFO else None
 
 

litellm/router_utils/pattern_match_deployments.py

@@ -204,7 +204,7 @@ class PatternMatchRouter:
 
         return litellm_deployment_litellm_model
 
-    def get_pattern(self, model: str, custom_llm_provider: str | None = None) -> list[dict] | None:
+    def get_pattern(self, model: str | None, custom_llm_provider: str | None = None) -> list[dict] | None:
         """
         Check if a pattern exists for the given model and custom llm provider
 
@@ -221,9 +221,9 @@ class PatternMatchRouter:
         return self.route(model) or self.route(f"{provider}/{model}")
 
     @staticmethod
-    def _resolved_provider(model: str) -> str | None:
+    def _resolved_provider(model: str | None) -> str | None:
         try:
-            return get_llm_provider(model=model)[1]
+            return get_llm_provider(model=model)[1] if model else None
         except Exception:  # noqa: BLE001  # get_llm_provider raises when the provider is unknown; the name then routes as-is
             return None
 

tests/test_litellm/router_utils/test_pattern_match_deployments.py

@@ -53,6 +53,20 @@ def test_get_pattern_bare_provider_name_never_matches_that_providers_wildcard(mo
     assert router.get_pattern("github_copilot") is None
 
 
+def test_get_pattern_missing_model_returns_none(monkeypatch):
+    """Regression: a request without a model reaches the auth layer's pattern walk as ``None``; the
+    declared-provider guard raised ``TypeError`` where the old inline resolve swallowed every
+    resolver error, so the proxy's missing-model 400 became a crash."""
+
+    def _unknown_provider(model, *args, **kwargs):
+        raise ValueError(f"unknown provider for {model}")
+
+    monkeypatch.setattr(pattern_match_deployments, "get_llm_provider", _unknown_provider)
+    router = PatternMatchRouter()
+    router.add_pattern("openai/*", _wildcard_deployment("openai/*"))
+    assert router.get_pattern(None) is None
+
+
 def test_get_pattern_still_resolves_unqualified_names(monkeypatch):
     monkeypatch.setattr(
         pattern_match_deployments,