diff --git a/backend/internal/service/payment_refund.go b/backend/internal/service/payment_refund.go
index 01eecff8..57469fa3 100644
--- a/backend/internal/service/payment_refund.go
+++ b/backend/internal/service/payment_refund.go
@@ -21,7 +21,7 @@ import (
 
 // getOrderProviderInstance looks up the provider instance that processed this order.
 // For legacy orders without provider_instance_id, it resolves only when the
-// enabled instance is uniquely identifiable from the stored order fields.
+// historical instance is uniquely identifiable from the stored order fields.
 func (s *PaymentService) getOrderProviderInstance(ctx context.Context, o *dbent.PaymentOrder) (*dbent.PaymentProviderInstance, error) {
 	if s == nil || s.entClient == nil || o == nil {
 		return nil, nil
@@ -40,47 +40,55 @@ func (s *PaymentService) getOrderProviderInstance(ctx context.Context, o *dbent.
 }
 
 func (s *PaymentService) resolveUniqueLegacyOrderProviderInstance(ctx context.Context, o *dbent.PaymentOrder) (*dbent.PaymentProviderInstance, error) {
+	paymentType := payment.GetBasePaymentType(strings.TrimSpace(o.PaymentType))
 	providerKey := strings.TrimSpace(psStringValue(o.ProviderKey))
 	if providerKey != "" {
 		instances, err := s.entClient.PaymentProviderInstance.Query().
-			Where(
-				paymentproviderinstance.EnabledEQ(true),
-				paymentproviderinstance.ProviderKeyEQ(providerKey),
-			).
+			Where(paymentproviderinstance.ProviderKeyEQ(providerKey)).
 			All(ctx)
 		if err != nil {
 			return nil, err
 		}
-		if len(instances) == 1 {
-			return instances[0], nil
+		matched := psFilterLegacyOrderProviderInstances(paymentType, instances)
+		if len(matched) == 1 {
+			return matched[0], nil
 		}
 		return nil, nil
 	}
 
-	paymentType := payment.GetBasePaymentType(strings.TrimSpace(o.PaymentType))
 	if paymentType == "" {
 		return nil, nil
 	}
 
 	instances, err := s.entClient.PaymentProviderInstance.Query().
-		Where(paymentproviderinstance.EnabledEQ(true)).
 		All(ctx)
 	if err != nil {
 		return nil, err
 	}
 
-	var matched []*dbent.PaymentProviderInstance
-	for _, inst := range instances {
-		if psLegacyOrderMatchesInstance(paymentType, inst) {
-			matched = append(matched, inst)
-		}
-	}
+	matched := psFilterLegacyOrderProviderInstances(paymentType, instances)
 	if len(matched) == 1 {
 		return matched[0], nil
 	}
 	return nil, nil
 }
 
+func psFilterLegacyOrderProviderInstances(orderPaymentType string, instances []*dbent.PaymentProviderInstance) []*dbent.PaymentProviderInstance {
+	if len(instances) == 0 {
+		return nil
+	}
+	if strings.TrimSpace(orderPaymentType) == "" {
+		return instances
+	}
+	var matched []*dbent.PaymentProviderInstance
+	for _, inst := range instances {
+		if psLegacyOrderMatchesInstance(orderPaymentType, inst) {
+			matched = append(matched, inst)
+		}
+	}
+	return matched
+}
+
 func psLegacyOrderMatchesInstance(orderPaymentType string, inst *dbent.PaymentProviderInstance) bool {
 	if inst == nil {
 		return false
diff --git a/backend/internal/service/payment_webhook_provider_test.go b/backend/internal/service/payment_webhook_provider_test.go
index 33e4186d..4f0b6848 100644
--- a/backend/internal/service/payment_webhook_provider_test.go
+++ b/backend/internal/service/payment_webhook_provider_test.go
@@ -141,6 +141,70 @@ func TestGetOrderProviderInstanceLeavesAmbiguousLegacyOrderUnresolved(t *testing
 	require.Nil(t, got)
 }
 
+func TestGetOrderProviderInstanceLeavesLegacyProviderKeyUnresolvedWhenHistoricalInstancesConflict(t *testing.T) {
+	ctx := context.Background()
+	client := newPaymentConfigServiceTestClient(t)
+	_, err := client.PaymentProviderInstance.Create().
+		SetProviderKey(payment.TypeStripe).
+		SetName("stripe-disabled-legacy").
+		SetConfig("{}").
+		SetSupportedTypes("stripe").
+		SetEnabled(false).
+		Save(ctx)
+	require.NoError(t, err)
+	_, err = client.PaymentProviderInstance.Create().
+		SetProviderKey(payment.TypeStripe).
+		SetName("stripe-enabled-current").
+		SetConfig("{}").
+		SetSupportedTypes("stripe").
+		SetEnabled(true).
+		Save(ctx)
+	require.NoError(t, err)
+
+	providerKey := payment.TypeStripe
+	order := &dbent.PaymentOrder{
+		PaymentType: payment.TypeStripe,
+		ProviderKey: &providerKey,
+	}
+
+	svc := &PaymentService{
+		entClient:    client,
+		loadBalancer: newWebhookProviderTestLoadBalancer(client),
+	}
+
+	got, err := svc.getOrderProviderInstance(ctx, order)
+	require.NoError(t, err)
+	require.Nil(t, got)
+}
+
+func TestGetOrderProviderInstanceLeavesProviderKeyMatchUnresolvedWhenTypeNotSupported(t *testing.T) {
+	ctx := context.Background()
+	client := newPaymentConfigServiceTestClient(t)
+	_, err := client.PaymentProviderInstance.Create().
+		SetProviderKey(payment.TypeWxpay).
+		SetName("wxpay-only").
+		SetConfig("{}").
+		SetSupportedTypes("wxpay").
+		SetEnabled(true).
+		Save(ctx)
+	require.NoError(t, err)
+
+	providerKey := payment.TypeWxpay
+	order := &dbent.PaymentOrder{
+		PaymentType: payment.TypeAlipayDirect,
+		ProviderKey: &providerKey,
+	}
+
+	svc := &PaymentService{
+		entClient:    client,
+		loadBalancer: newWebhookProviderTestLoadBalancer(client),
+	}
+
+	got, err := svc.getOrderProviderInstance(ctx, order)
+	require.NoError(t, err)
+	require.Nil(t, got)
+}
+
 func TestGetWebhookProviderRejectsAmbiguousRegistryFallback(t *testing.T) {
 	ctx := context.Background()
 	client := newPaymentConfigServiceTestClient(t)