diff --git a/internal/core/interfaces.go b/internal/core/interfaces.go
index 3dfc05b8..eb87f635 100644
--- a/internal/core/interfaces.go
+++ b/internal/core/interfaces.go
@@ -194,4 +194,19 @@ type ModelLookup interface {
 
 	// ModelCount returns the number of registered models
 	ModelCount() int
+
+	// GetProviderName maps a model selector back to the concrete configured
+	// provider instance name. Implementations that have no such mapping return
+	// an empty string. Same shape as the optional ProviderNameResolver
+	// interface used elsewhere for provider-side type assertions.
+	GetProviderName(model string) string
+
+	// GetProviderNameForType maps a provider type such as "openai" to the
+	// concrete configured instance name chosen for routing, e.g.
+	// "openai-primary". Returns empty when no mapping exists.
+	GetProviderNameForType(providerType string) string
+
+	// GetProviderTypeForName maps a concrete configured instance name back to
+	// its provider type. Returns empty when no mapping exists.
+	GetProviderTypeForName(providerName string) string
 }
diff --git a/internal/providers/router.go b/internal/providers/router.go
index 4ea165f3..d5df805b 100644
--- a/internal/providers/router.go
+++ b/internal/providers/router.go
@@ -112,12 +112,7 @@ func (r *Router) resolveUnqualifiedSelector(selector core.ModelSelector) (core.M
 	if selector.Provider != "" || strings.TrimSpace(selector.Model) == "" {
 		return core.ModelSelector{}, false
 	}
-
-	named, ok := r.lookup.(core.ProviderNameResolver)
-	if !ok {
-		return core.ModelSelector{}, false
-	}
-	providerName := strings.TrimSpace(named.GetProviderName(selector.Model))
+	providerName := strings.TrimSpace(r.lookup.GetProviderName(selector.Model))
 	if providerName == "" {
 		return core.ModelSelector{}, false
 	}
@@ -613,19 +608,13 @@ func (r *Router) GetProviderName(model string) string {
 	if selector.Provider != "" {
 		return selector.Provider
 	}
-	if named, ok := r.lookup.(core.ProviderNameResolver); ok {
-		return named.GetProviderName(selector.QualifiedModel())
-	}
-	return ""
+	return r.lookup.GetProviderName(selector.QualifiedModel())
 }
 
 // GetProviderNameForType returns the concrete configured provider instance name
 // chosen for a provider-typed route.
 func (r *Router) GetProviderNameForType(providerType string) string {
-	if named, ok := r.lookup.(core.ProviderTypeNameResolver); ok {
-		return strings.TrimSpace(named.GetProviderNameForType(providerType))
-	}
-	return ""
+	return strings.TrimSpace(r.lookup.GetProviderNameForType(providerType))
 }
 
 // GetProviderTypeForName returns the provider type for a concrete configured
@@ -635,20 +624,7 @@ func (r *Router) GetProviderTypeForName(providerName string) string {
 	if providerName == "" {
 		return ""
 	}
-	if typed, ok := r.lookup.(core.ProviderNameTypeResolver); ok {
-		return strings.TrimSpace(typed.GetProviderTypeForName(providerName))
-	}
-	if models, ok := r.lookup.(modelWithProviderLister); ok {
-		for _, entry := range models.ListModelsWithProvider() {
-			if strings.TrimSpace(entry.ProviderName) != providerName {
-				continue
-			}
-			if providerType := strings.TrimSpace(entry.ProviderType); providerType != "" {
-				return providerType
-			}
-		}
-	}
-	return ""
+	return strings.TrimSpace(r.lookup.GetProviderTypeForName(providerName))
 }
 
 func (r *Router) providerByType(providerType string) core.Provider {
diff --git a/internal/providers/router_test.go b/internal/providers/router_test.go
index efad078c..fc8b8523 100644
--- a/internal/providers/router_test.go
+++ b/internal/providers/router_test.go
@@ -104,6 +104,13 @@ func (m *mockModelLookup) ModelCount() int {
 	return len(m.models)
 }
 
+// The mock keeps no provider-name <-> type mapping, so the three resolver
+// methods always return empty. Tests that need provider-name routing use the
+// real ModelRegistry via newTestRegistryWithModels instead of this mock.
+func (m *mockModelLookup) GetProviderName(_ string) string             { return "" }
+func (m *mockModelLookup) GetProviderNameForType(_ string) string      { return "" }
+func (m *mockModelLookup) GetProviderTypeForName(_ string) string      { return "" }
+
 // mockProvider is a simple mock implementation of core.Provider for testing
 type mockProvider struct {
 	name              string