fix(#244): show waiting spinner after NWC payment instead of re-arming the pay button

lib/features/order/screens/pay_lightning_invoice_screen.dart

@@ -212,7 +212,13 @@ class _PayLightningInvoiceScreenState
         }
 
         // If NWC wallet is connected and payment hasn't failed yet, show auto-pay.
-        if (isWalletConnected && !_manualMode) {
+        // Once a payment has been detected (_waiting), fall through to the
+        // invoice/QR branch instead: it renders the same waiting-for-
+        // confirmation spinner in context, whereas NwcPaymentWidget re-arms its
+        // own pay button in its finally block and would let the user re-send the
+        // same bolt11 (the wallet rejects the duplicate and drops them onto the
+        // QR of an already-settled invoice). Issue #244.
+        if (isWalletConnected && !_manualMode && !_waiting) {
           return Scaffold(
             appBar: AppBar(title: Text(l10n.payLightningInvoiceTitle)),
             body: Padding(

test/features/order/screens/pay_lightning_invoice_screen_test.dart

@@ -0,0 +1,82 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mostro/features/order/providers/trade_state_provider.dart';
+import 'package:mostro/features/order/screens/pay_lightning_invoice_screen.dart';
+import 'package:mostro/features/settings/providers/nwc_provider.dart';
+import 'package:mostro/l10n/app_localizations.dart';
+import 'package:mostro/shared/widgets/nwc_payment_widget.dart';
+import 'package:mostro/src/rust/api/types.dart';
+
+import '../../../support/fake_trades.dart';
+
+/// A trade with a usable hold invoice so the screen passes the
+/// invoice.isEmpty / amountSats guard and reaches the NWC / QR branches.
+TradeInfo _payableTrade() {
+  final base = fakeTrade(
+    id: 'x',
+    status: OrderStatus.waitingPayment,
+    amountSats: BigInt.from(1000),
+  );
+  return TradeInfo(
+    id: base.id,
+    order: base.order,
+    role: base.role,
+    counterpartyPubkey: base.counterpartyPubkey,
+    currentStep: base.currentStep,
+    tradeKeyIndex: base.tradeKeyIndex,
+    startedAt: base.startedAt,
+    holdInvoice: 'lnbc1000n1pxxxxxxx',
+  );
+}
+
+Widget _app({required bool walletConnected, required TradeInfo trade}) {
+  return ProviderScope(
+    overrides: [
+      isWalletConnectedProvider.overrideWithValue(walletConnected),
+      tradeInfoStreamProvider('order-x').overrideWith(
+        (ref) => Stream.value(trade),
+      ),
+      // Keep the status poller quiet so it doesn't fire navigation during the
+      // test; the NWC success callback is what drives _waiting here.
+      tradeStatusProvider('order-x').overrideWith(
+        (ref) => const Stream.empty(),
+      ),
+    ],
+    child: const MaterialApp(
+      localizationsDelegates: AppLocalizations.localizationsDelegates,
+      supportedLocales: AppLocalizations.supportedLocales,
+      home: PayLightningInvoiceScreen(orderId: 'order-x'),
+    ),
+  );
+}
+
+void main() {
+  testWidgets(
+    '#244: after NWC payment the pay widget is replaced by a waiting spinner',
+    (tester) async {
+      await tester.pumpWidget(
+        _app(walletConnected: true, trade: _payableTrade()),
+      );
+      await tester.pump(); // resolve the trade stream
+      await tester.pump(const Duration(milliseconds: 50)); // let the stream settle
+
+      final l10n = await AppLocalizations.delegate.load(const Locale('en'));
+
+      // Before payment: the NWC auto-pay widget is shown, no waiting text.
+      expect(find.byType(NwcPaymentWidget), findsOneWidget);
+      expect(find.text(l10n.waitingForPaymentConfirmation), findsNothing);
+
+      // Simulate a successful NWC payment by invoking the widget's success
+      // callback (what the real wallet flow calls). This sets _waiting = true.
+      final nwc = tester.widget<NwcPaymentWidget>(find.byType(NwcPaymentWidget));
+      nwc.onPaymentSuccess();
+      await tester.pump();
+
+      // After payment: the pay widget is gone and the confirmation spinner
+      // (with its label) is shown instead — no re-armed pay button.
+      expect(find.byType(NwcPaymentWidget), findsNothing);
+      expect(find.text(l10n.waitingForPaymentConfirmation), findsOneWidget);
+    },
+  );
+}

test/support/fake_trades.dart

@@ -11,6 +11,7 @@ TradeInfo fakeTrade({
   String paymentMethod = 'Wire',
   bool isMine = false,
   int startedAt = 1000,
+  BigInt? amountSats,
 }) {
   final order = OrderInfo(
     id: 'order-$id',
@@ -22,6 +23,7 @@ TradeInfo fakeTrade({
     premium: 0,
     creatorPubkey: 'pubkey-$id',
     createdAt: startedAt,
+    amountSats: amountSats ?? BigInt.zero,
     isMine: isMine,
     rating: 0,
     totalReviews: 0,