fix(router): bare authenticating-provider names declare nothing

litellm/litellm_core_utils/get_llm_provider_logic.py

@@ -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]
+    declared: Final = custom_llm_provider or (model.split("/", 1)[0] if "/" in model else None)
     return declared if declared in PROVIDERS_THAT_AUTHENTICATE_ON_PROVIDER_INFO else None
 
 

litellm/proxy/proxy_server.py

@@ -12482,11 +12482,7 @@ async def supported_openai_params(model: str):
 
     global llm_router
     try:
-        resolved_models: Final = (
-            llm_router.resolved_litellm_models(model)
-            if llm_router is not None and declared_authenticating_provider(model) is None
-            else ()
-        )
+        resolved_models: Final = llm_router.resolved_litellm_models(model) if llm_router is not None else ()
         target_model: Final = resolved_models[0] if resolved_models else model
         declared_provider: Final = declared_authenticating_provider(target_model)
         litellm_model, custom_llm_provider = (

tests/test_litellm/litellm_core_utils/test_get_supported_openai_params.py

@@ -188,6 +188,8 @@ class TestDeclaredAuthenticatingProvider:
             ("gpt-4o", "github_copilot", "github_copilot"),
             ("openai/gpt-4o", None, None),
             ("gpt-4o", "openai", None),
+            ("github_copilot", None, None),
+            ("chatgpt", None, None),
         ],
     )
     def test_names_only_the_providers_whose_resolution_authenticates(self, model, provider, expected):

tests/test_litellm/proxy/proxy_server/test_routes_utils.py

@@ -147,6 +147,27 @@ def test_supported_openai_params_resolves_router_alias(client, auth_as, monkeypa
     assert "max_tokens" in response.json()["supported_openai_params"]
 
 
+def test_supported_openai_params_declared_prefix_alias_resolves_through_router(client, auth_as, monkeypatch):
+    """Regression: an alias whose name starts with an authenticating provider's prefix skipped
+    router resolution and answered with that provider's params instead of the deployment's."""
+    router = litellm.Router(
+        model_list=[
+            {
+                "model_name": "github_copilot/gpt-4o",
+                "litellm_params": {"model": "anthropic/claude-opus-4-6", "api_key": "sk-test"},
+            }
+        ]
+    )
+    monkeypatch.setattr(proxy_server, "llm_router", router)
+
+    with auth_as():
+        response = client.get("/utils/supported_openai_params", params={"model": "github_copilot/gpt-4o"})
+
+    assert response.status_code == 200
+    expected = litellm.get_supported_openai_params(model="claude-opus-4-6", custom_llm_provider="anthropic")
+    assert response.json() == {"supported_openai_params": expected}
+
+
 def test_supported_openai_params_never_runs_oauth_for_authenticating_providers(client, auth_as, monkeypatch, tmp_path):
     """Regression: github_copilot/chatgpt names answer from their declaration; resolving them
     through ``get_llm_provider`` would run the provider's OAuth device flow and block the event loop."""

tests/test_litellm/router_utils/test_pattern_match_deployments.py

@@ -40,6 +40,19 @@ def test_get_pattern_never_resolves_declared_authenticating_providers(monkeypatc
     assert resolution_attempts == []
 
 
+def test_get_pattern_bare_provider_name_never_matches_that_providers_wildcard(monkeypatch):
+    """Regression: a bare ``github_copilot`` adopted itself as its provider and retried as
+    ``github_copilot/github_copilot``, false-matching the wildcard for a name no deployment serves."""
+
+    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("github_copilot/*", _wildcard_deployment("github_copilot/*"))
+    assert router.get_pattern("github_copilot") is None
+
+
 def test_get_pattern_still_resolves_unqualified_names(monkeypatch):
     monkeypatch.setattr(
         pattern_match_deployments,