fix: race condition when refreshing all shopinbit tickets when not all tickets use the same customer key. Probably introduces bugs elsewhere now though...

diff --git a/lib/pages/shopinbit/shopinbit_car_fee_view.dart b/lib/pages/shopinbit/shopinbit_car_fee_view.dart
index 60ea3f4..9bb863e 100644
--- a/lib/pages/shopinbit/shopinbit_car_fee_view.dart
+++ b/lib/pages/shopinbit/shopinbit_car_fee_view.dart
@@ -202,7 +202,7 @@ class _ShopInBitCarFeeViewState extends ConsumerState<ShopInBitCarFeeView> {
     if (_submitting) return;
     setState(() => _submitting = true);
     try {
-      await ref.read(pShopinBitService).ensureCustomerKey();
+      final customerKey = await ref.read(pShopinBitService).ensureCustomerKey();
 
       // Delivery address (always provided)
       final deliveryName = _splitFullName(_nameController.text);
@@ -242,7 +242,11 @@ class _ShopInBitCarFeeViewState extends ConsumerState<ShopInBitCarFeeView> {
       final resp = await ref
           .read(pShopinBitService)
           .client
-          .createCarResearchInvoice(billing: billing, request: request);
+          .createCarResearchInvoice(
+            billing: billing,
+            request: request,
+            customerKey: customerKey,
+          );
 
       if (resp.hasError || resp.value == null) {
         Logging.instance.e(
@@ -273,14 +277,14 @@ class _ShopInBitCarFeeViewState extends ConsumerState<ShopInBitCarFeeView> {
       // `GET /car-research/invoices/current` (see the requests list).
 
       // Best-effort fee fetch; do not block navigation on fee parse failure.
-      await _loadFee(invoice);
+      await _loadFee(invoice, customerKey);
 
       if (!mounted) return;
 
       unawaited(
         Navigator.of(context).pushNamed(
           ShopInBitCarResearchPaymentView.routeName,
-          arguments: invoice,
+          arguments: (invoice: invoice, customerKey: customerKey),
         ),
       );
     } catch (e, s) {
@@ -314,7 +318,7 @@ class _ShopInBitCarFeeViewState extends ConsumerState<ShopInBitCarFeeView> {
     }
   }
 
-  Future<void> _loadFee(CarResearchInvoice invoice) async {
+  Future<void> _loadFee(CarResearchInvoice invoice, String customerKey) async {
     // Keep status call for visibility into any future API changes surfacing
     // a fee field. Today the endpoint returns only {status, additional}, so
     // we source the displayed amount from the BIP21 payment URIs instead.
@@ -322,7 +326,10 @@ class _ShopInBitCarFeeViewState extends ConsumerState<ShopInBitCarFeeView> {
       final resp = await ref
           .read(pShopinBitService)
           .client
-          .getCarResearchInvoiceStatus(invoice.btcpayInvoice);
+          .getCarResearchInvoiceStatus(
+            invoice.btcpayInvoice,
+            customerKey: customerKey,
+          );
       if (resp.hasError || resp.value == null) {
         Logging.instance.i(
           "CarResearch status response (car_fee_view): error "
diff --git a/lib/pages/shopinbit/shopinbit_car_research_payment_view.dart b/lib/pages/shopinbit/shopinbit_car_research_payment_view.dart
index eb1137b..f8367ab 100644
--- a/lib/pages/shopinbit/shopinbit_car_research_payment_view.dart
+++ b/lib/pages/shopinbit/shopinbit_car_research_payment_view.dart
@@ -30,11 +30,16 @@ import 'shopinbit_tickets_view.dart';
 enum _PaymentFlowState { idle, polling, finalizing, complete, error }
 
 class ShopInBitCarResearchPaymentView extends ConsumerStatefulWidget {
-  const ShopInBitCarResearchPaymentView({super.key, required this.invoice});
+  const ShopInBitCarResearchPaymentView({
+    super.key,
+    required this.invoice,
+    required this.customerKey,
+  });
 
   static const String routeName = "/shopInBitCarResearchPayment";
 
   final CarResearchInvoice invoice;
+  final String customerKey;
 
   @override
   ConsumerState<ShopInBitCarResearchPaymentView> createState() =>
@@ -221,7 +226,10 @@ class _ShopInBitCarResearchPaymentViewState
       final resp = await ref
           .read(pShopinBitService)
           .client
-          .getCarResearchInvoiceStatus(widget.invoice.btcpayInvoice);
+          .getCarResearchInvoiceStatus(
+            widget.invoice.btcpayInvoice,
+            customerKey: widget.customerKey,
+          );
       if (resp.hasError || resp.value == null) {
         if (mounted) {
           unawaited(
@@ -288,6 +296,7 @@ class _ShopInBitCarResearchPaymentViewState
       // and creates the receipt and real car ticket even if this call fails.
       final logResp = await client.logCarResearchPayment(
         widget.invoice.btcpayInvoice,
+        customerKey: widget.customerKey,
       );
 
       if (logResp.hasError || logResp.value == null) {
diff --git a/lib/pages/shopinbit/shopinbit_payment_shared.dart b/lib/pages/shopinbit/shopinbit_payment_shared.dart
index 93a6974..af6974d 100644
--- a/lib/pages/shopinbit/shopinbit_payment_shared.dart
+++ b/lib/pages/shopinbit/shopinbit_payment_shared.dart
@@ -4,9 +4,9 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../app_config.dart';
 import '../../models/isar/models/ethereum/eth_contract.dart';
-import '../../providers/global/shopin_bit_service_provider.dart';
 import '../../providers/providers.dart';
 import '../../route_generator.dart';
+import '../../services/shopinbit/src/client.dart';
 import '../../services/shopinbit/src/models/payment.dart';
 import '../../services/wallets.dart';
 import '../../themes/stack_colors.dart';
@@ -229,18 +229,24 @@ Future<bool> tryNavigateToShopInBitWalletSend({
 // recovery" guidance; PUT (which regenerates) only when GET shows none.
 // Returns null on any failure so the view can fall back to polling.
 Future<PaymentInfo?> fetchShopInBitPaymentInfo(
-  WidgetRef ref,
+  ShopInBitClient client,
   int apiTicketId,
+  String customerKey,
 ) async {
   try {
-    final client = ref.read(pShopinBitService).client;
-    final getResp = await client.getPayment(apiTicketId);
+    final getResp = await client.getPayment(
+      apiTicketId,
+      customerKey: customerKey,
+    );
     if (!getResp.hasError &&
         getResp.value != null &&
         getResp.value!.paymentLinks.isNotEmpty) {
       return getResp.value;
     }
-    final putResp = await client.putPayment(apiTicketId);
+    final putResp = await client.putPayment(
+      apiTicketId,
+      customerKey: customerKey,
+    );
     if (!putResp.hasError && putResp.value != null) {
       return putResp.value;
     }
diff --git a/lib/pages/shopinbit/shopinbit_payment_view.dart b/lib/pages/shopinbit/shopinbit_payment_view.dart
index 97888d0..2ad8237 100644
--- a/lib/pages/shopinbit/shopinbit_payment_view.dart
+++ b/lib/pages/shopinbit/shopinbit_payment_view.dart
@@ -74,6 +74,18 @@ class _ShopInBitPaymentViewState extends ConsumerState<ShopInBitPaymentView> {
 
   bool get _payNowEnabled => !_isExpiredOrInvalid && !_isTerminal;
 
+  String? _customerKeyCache;
+
+  Future<String> get _customerKey async {
+    _customerKeyCache ??=
+        (await ref
+                .read(pSharedDrift)
+                .shopInBitTicketsDao
+                .getByApiId(widget.apiTicketId))!
+            .customerKey;
+    return _customerKeyCache!;
+  }
+
   @override
   void initState() {
     super.initState();
@@ -111,7 +123,7 @@ class _ShopInBitPaymentViewState extends ConsumerState<ShopInBitPaymentView> {
       final resp = await ref
           .read(pShopinBitService)
           .client
-          .getPayment(widget.apiTicketId);
+          .getPayment(widget.apiTicketId, customerKey: await _customerKey);
       if (!resp.hasError && resp.value != null && mounted) {
         setState(() => _applyPaymentInfo(resp.value!));
         if (_isTerminal) {
@@ -123,11 +135,15 @@ class _ShopInBitPaymentViewState extends ConsumerState<ShopInBitPaymentView> {
 
   Future<void> _refreshInvoice() async {
     _pollTimer?.cancel();
+
+    final customerKey = await _customerKey;
+    if (!mounted) return;
+
     final resp = await showLoading(
       whileFuture: ref
           .read(pShopinBitService)
           .client
-          .putPayment(widget.apiTicketId),
+          .putPayment(widget.apiTicketId, customerKey: customerKey),
       context: context,
       message: "Refreshing invoice",
     );
@@ -140,11 +156,15 @@ class _ShopInBitPaymentViewState extends ConsumerState<ShopInBitPaymentView> {
 
   Future<void> _checkForPayment() async {
     _pollTimer?.cancel();
+
+    final customerKey = await _customerKey;
+    if (!mounted) return;
+
     final resp = await showLoading(
       whileFuture: ref
           .read(pShopinBitService)
           .client
-          .getPayment(widget.apiTicketId),
+          .getPayment(widget.apiTicketId, customerKey: customerKey),
       context: context,
       message: "Checking for payment",
     );
diff --git a/lib/pages/shopinbit/shopinbit_shipping_view.dart b/lib/pages/shopinbit/shopinbit_shipping_view.dart
index 1f3c412..82914b8 100644
--- a/lib/pages/shopinbit/shopinbit_shipping_view.dart
+++ b/lib/pages/shopinbit/shopinbit_shipping_view.dart
@@ -5,6 +5,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_svg/svg.dart';
 
+import '../../providers/db/drift_provider.dart';
 import '../../providers/global/shopin_bit_service_provider.dart';
 import '../../services/shopinbit/src/models/address.dart';
 import '../../services/shopinbit/src/models/payment.dart';
@@ -195,6 +196,11 @@ class _ShopInBitShippingViewState extends ConsumerState<ShopInBitShippingView> {
         );
       }
 
+      final thisTicket = await ref
+          .read(pSharedDrift)
+          .shopInBitTicketsDao
+          .getByApiId(widget.apiTicketId);
+
       final resp = await ref
           .read(pShopinBitService)
           .client
@@ -209,6 +215,7 @@ class _ShopInBitShippingViewState extends ConsumerState<ShopInBitShippingView> {
               country: country,
             ),
             billing: billingAddress,
+            customerKey: thisTicket!.customerKey,
           );
 
       if (resp.hasError) {
@@ -216,7 +223,11 @@ class _ShopInBitShippingViewState extends ConsumerState<ShopInBitShippingView> {
         debugPrint("submitAddress failed: ${resp.exception?.message}");
       }
 
-      paymentInfo = await fetchShopInBitPaymentInfo(ref, widget.apiTicketId);
+      paymentInfo = await fetchShopInBitPaymentInfo(
+        ref.read(pShopinBitService).client,
+        widget.apiTicketId,
+        thisTicket.customerKey,
+      );
     } catch (e) {
       debugPrint("submitAddress threw: $e");
     } finally {
diff --git a/lib/pages/shopinbit/shopinbit_ticket_detail.dart b/lib/pages/shopinbit/shopinbit_ticket_detail.dart
index 364407a..e3af19c 100644
--- a/lib/pages/shopinbit/shopinbit_ticket_detail.dart
+++ b/lib/pages/shopinbit/shopinbit_ticket_detail.dart
@@ -8,6 +8,7 @@ import 'package:intl/intl.dart';
 
 import '../../db/drift/shared_db/shared_database.dart';
 import '../../models/shopinbit/shopinbit_enums.dart';
+import '../../providers/db/drift_provider.dart';
 import '../../providers/global/shopin_bit_service_provider.dart';
 import '../../services/shopinbit/src/models/message.dart';
 import '../../themes/stack_colors.dart';
@@ -97,7 +98,13 @@ class _ShopInBitTicketDetailState extends ConsumerState<ShopInBitTicketDetail> {
     _messageController.clear();
 
     try {
-      final ok = await ref.read(pShopinBitService).sendMessage(_id, text);
+      final thisTicket = await ref
+          .read(pSharedDrift)
+          .shopInBitTicketsDao
+          .getByApiId(_id);
+      final ok = await ref
+          .read(pShopinBitService)
+          .sendMessage(_id, text, thisTicket!.customerKey);
       if (ok) {
         // Pull the server's copy into the DB row, then drop our optimistic one.
         await _refresh();
diff --git a/lib/pages/shopinbit/shopinbit_tickets_view.dart b/lib/pages/shopinbit/shopinbit_tickets_view.dart
index 3f941d5..87c9927 100644
--- a/lib/pages/shopinbit/shopinbit_tickets_view.dart
+++ b/lib/pages/shopinbit/shopinbit_tickets_view.dart
@@ -38,10 +38,10 @@ class _ShopInBitTicketsViewState extends ConsumerState<ShopInBitTicketsView> {
   bool _refreshing = false;
   bool _resuming = false;
 
-  // An unfinished car research fee invoice recovered from the server, if any.
+  // Some unfinished car research fee invoices recovered from the server, if any.
   // The fee is paid before any ticket exists, so this is the only way to let
   // the user resume it — there is no local "pending" row anymore.
-  CarResearchInvoice? _resumableInvoice;
+  List<CarResearchInvoice>? _resumableInvoices;
 
   @override
   void initState() {
@@ -65,12 +65,13 @@ class _ShopInBitTicketsViewState extends ConsumerState<ShopInBitTicketsView> {
   /// Pull the most recent still-payable car research invoice from
   /// `GET /car-research/invoices/current` so we can surface a "resume" entry.
   Future<void> _loadResumableInvoice() async {
-    CarResearchInvoice? resumable;
+    List<CarResearchInvoice>? resumable;
     try {
+      final customerKey = await ref.read(pShopinBitService).ensureCustomerKey();
       final resp = await ref
           .read(pShopinBitService)
           .client
-          .getCurrentCarResearchInvoices();
+          .getCurrentCarResearchInvoices(customerKey: customerKey);
       final invoices = resp.value;
       if (invoices != null) {
         for (final inv in invoices) {
@@ -80,10 +81,13 @@ class _ShopInBitTicketsViewState extends ConsumerState<ShopInBitTicketsView> {
               (inv.expiresAt!.isAfter(DateTime.now()) ||
                   carResearchIsFinalized(inv.status, inv.additional));
           if (payable) {
-            resumable = CarResearchInvoice(
-              btcpayInvoice: inv.invoiceId,
-              expiresAt: inv.expiresAt!,
-              paymentLinks: inv.paymentLinks,
+            resumable ??= [];
+            resumable.add(
+              CarResearchInvoice(
+                btcpayInvoice: inv.invoiceId,
+                expiresAt: inv.expiresAt!,
+                paymentLinks: inv.paymentLinks,
+              ),
             );
             break;
           }
@@ -98,17 +102,20 @@ class _ShopInBitTicketsViewState extends ConsumerState<ShopInBitTicketsView> {
       // Leave _resumableInvoice unchanged on failure.
       return;
     }
-    if (mounted) setState(() => _resumableInvoice = resumable);
+    if (mounted) setState(() => _resumableInvoices = resumable);
   }
 
   Future<void> _resumeFlow(CarResearchInvoice invoice) async {
     if (_resuming) return;
     setState(() => _resuming = true);
     try {
-      await Navigator.of(context).pushNamed(
-        ShopInBitCarResearchPaymentView.routeName,
-        arguments: invoice,
-      );
+      final customerKey = await ref.read(pShopinBitService).ensureCustomerKey();
+      if (mounted) {
+        await Navigator.of(context).pushNamed(
+          ShopInBitCarResearchPaymentView.routeName,
+          arguments: (invoice: invoice, customerKey: customerKey),
+        );
+      }
     } finally {
       if (mounted) setState(() => _resuming = false);
     }
@@ -118,7 +125,7 @@ class _ShopInBitTicketsViewState extends ConsumerState<ShopInBitTicketsView> {
     required BuildContext context,
     required bool isDesktop,
     required List<ShopInBitTicket> tickets,
-    required CarResearchInvoice? resumable,
+    required List<CarResearchInvoice>? resumable,
   }) {
     if (resumable == null && tickets.isEmpty) {
       return [
@@ -136,20 +143,22 @@ class _ShopInBitTicketsViewState extends ConsumerState<ShopInBitTicketsView> {
 
     final children = <Widget>[];
     if (resumable != null) {
-      children.add(
-        RoundedContainer(
-          color: Theme.of(context).extension<StackColors>()!.popupBG,
-          onPressed: _resuming ? null : () => unawaited(_resumeFlow(resumable)),
-          child: _RequestRow(
-            title: "Car Research (In Progress)",
-            subtitle: _resuming
-                ? "Opening your car research payment..."
-                : "Tap to continue your car research payment",
-            badgeText: "Resume",
-            badgeColor: Theme.of(
-              context,
-            ).extension<StackColors>()!.accentColorYellow,
-            loading: _resuming,
+      children.addAll(
+        resumable.map(
+          (e) => RoundedContainer(
+            color: Theme.of(context).extension<StackColors>()!.popupBG,
+            onPressed: _resuming ? null : () => unawaited(_resumeFlow(e)),
+            child: _RequestRow(
+              title: "Car Research (In Progress)",
+              subtitle: _resuming
+                  ? "Opening your car research payment..."
+                  : "Tap to continue your car research payment",
+              badgeText: "Resume",
+              badgeColor: Theme.of(
+                context,
+              ).extension<StackColors>()!.accentColorYellow,
+              loading: _resuming,
+            ),
           ),
         ),
       );
@@ -192,7 +201,7 @@ class _ShopInBitTicketsViewState extends ConsumerState<ShopInBitTicketsView> {
     final isDesktop = Util.isDesktop;
     final tickets =
         ref.watch(pShopInBitTickets).asData?.value ?? const <ShopInBitTicket>[];
-    final resumable = _resumableInvoice;
+    final resumables = _resumableInvoices;
 
     return ConditionalParent(
       condition: isDesktop,
@@ -272,7 +281,7 @@ class _ShopInBitTicketsViewState extends ConsumerState<ShopInBitTicketsView> {
                 context: context,
                 isDesktop: isDesktop,
                 tickets: tickets,
-                resumable: resumable,
+                resumable: resumables,
               ),
             ],
           ),
diff --git a/lib/route_generator.dart b/lib/route_generator.dart
index a685528..cbe2a11 100644
--- a/lib/route_generator.dart
+++ b/lib/route_generator.dart
@@ -1242,10 +1242,13 @@ class RouteGenerator {
         return _routeError("${settings.name} invalid args: ${args.toString()}");
 
       case ShopInBitCarResearchPaymentView.routeName:
-        if (args is CarResearchInvoice) {
+        if (args is ({CarResearchInvoice invoice, String customerKey})) {
           return getRoute(
             shouldUseMaterialRoute: useMaterialPageRoute,
-            builder: (_) => ShopInBitCarResearchPaymentView(invoice: args),
+            builder: (_) => ShopInBitCarResearchPaymentView(
+              invoice: args.invoice,
+              customerKey: args.customerKey,
+            ),
             settings: RouteSettings(name: settings.name),
           );
         }
diff --git a/lib/services/shopinbit/shopinbit_service.dart b/lib/services/shopinbit/shopinbit_service.dart
index 1f33466..fc6c72c 100644
--- a/lib/services/shopinbit/shopinbit_service.dart
+++ b/lib/services/shopinbit/shopinbit_service.dart
@@ -29,7 +29,6 @@ class ShopInBitService {
     final ShopInBitSetting? current = await db.shopInBitSettingsDao
         .getCurrentSettings();
     if (current != null) {
-      client.externalCustomerKey = current.customerKey;
       await db.shopInBitSettingsDao.touch(current.customerKey);
       return current.customerKey;
     }
@@ -48,7 +47,6 @@ class ShopInBitService {
   /// settings. The UI filters tickets by the active key.
   Future<String> useCustomerKey(String key) async {
     await db.shopInBitSettingsDao.upsert(key);
-    client.externalCustomerKey = key;
     return key;
   }
 
@@ -120,10 +118,15 @@ class ShopInBitService {
     return ref;
   }
 
-  Future<bool> sendMessage(int apiTicketId, String message) async {
+  Future<bool> sendMessage(
+    int apiTicketId,
+    String message,
+    String customerKey,
+  ) async {
     final ApiResponse<Map<String, dynamic>> resp = await client.sendMessage(
       apiTicketId,
       message,
+      customerKey: customerKey,
     );
     if (resp.hasError) return false;
     unawaited(refreshOne(apiTicketId));
@@ -176,16 +179,13 @@ class ShopInBitService {
         return;
       }
 
-      // Ensure the client points at the right key for this ticket's calls.
-      client.externalCustomerKey = customerKey;
-
       final ApiResponse<TicketFull> fullResp;
       final ApiResponse<TicketStatus> statusResp;
       final ApiResponse<List<TicketMessage>> messagesResp;
       (fullResp, statusResp, messagesResp) = await (
-        client.getTicketFull(id),
-        client.getTicketStatus(id),
-        client.getMessages(id),
+        client.getTicketFull(id, customerKey: customerKey),
+        client.getTicketStatus(id, customerKey: customerKey),
+        client.getMessages(id, customerKey: customerKey),
       ).wait;
 
       if (existing == null) {
diff --git a/lib/services/shopinbit/src/api_response.dart b/lib/services/shopinbit/src/api_response.dart
index a1e9135..623afc3 100644
--- a/lib/services/shopinbit/src/api_response.dart
+++ b/lib/services/shopinbit/src/api_response.dart
@@ -3,8 +3,9 @@ import 'api_exception.dart';
 class ApiResponse<T> {
   final T? value;
   final ApiException? exception;
+  final String? customerKey;
 
-  ApiResponse({this.value, this.exception});
+  ApiResponse({this.value, this.exception, this.customerKey});
 
   bool get hasError => exception != null;
 
diff --git a/lib/services/shopinbit/src/client.dart b/lib/services/shopinbit/src/client.dart
index c939c5a..80ee6dc 100644
--- a/lib/services/shopinbit/src/client.dart
+++ b/lib/services/shopinbit/src/client.dart
@@ -27,10 +27,6 @@ class ShopInBitClient {
   final HTTP _httpClient;
   final TokenManager _tokenManager;
 
-  String? _externalCustomerKey;
-
-  set externalCustomerKey(String? key) => _externalCustomerKey = key;
-
   ShopInBitClient({
     required this.accessKey,
     required this.partnerSecret,
@@ -38,8 +34,7 @@ class ShopInBitClient {
     this.sandbox = false,
     String? externalCustomerKey,
     HTTP? httpClient,
-  }) : _externalCustomerKey = externalCustomerKey,
-       _httpClient = httpClient ?? const HTTP(),
+  }) : _httpClient = httpClient ?? const HTTP(),
        _tokenManager = TokenManager(
          accessKey: accessKey,
          partnerSecret: partnerSecret,
@@ -66,7 +61,7 @@ class ShopInBitClient {
     return _request(
       'GET',
       '/generate-key',
-      needsCustomerKey: false,
+      customerKey: null,
       parse: (json) {
         return json['external_customer_key'] as String;
       },
@@ -74,19 +69,14 @@ class ShopInBitClient {
   }
 
   Future<ApiResponse<Map<String, dynamic>>> getHealth() async {
-    return _request(
-      'GET',
-      '/health',
-      needsCustomerKey: false,
-      parse: (json) => json,
-    );
+    return _request('GET', '/health', customerKey: null, parse: (json) => json);
   }
 
   Future<ApiResponse<List<Map<String, dynamic>>>> getCountries() async {
     return _requestRaw(
       'GET',
       '/meta/countries',
-      needsCustomerKey: false,
+      customerKey: null,
       needsAuth: false,
       parse: (body) {
         final decoded = jsonDecode(body);
@@ -127,22 +117,31 @@ class ShopInBitClient {
           number: json['ticket_number'].toString(),
         );
       },
+      customerKey: externalCustomerKey,
     );
   }
 
-  Future<ApiResponse<TicketStatus>> getTicketStatus(int ticketId) async {
+  Future<ApiResponse<TicketStatus>> getTicketStatus(
+    int ticketId, {
+    required String customerKey,
+  }) async {
     return _request(
       'GET',
       '/tickets/$ticketId/status',
       parse: TicketStatus.fromJson,
+      customerKey: customerKey,
     );
   }
 
-  Future<ApiResponse<TicketFull>> getTicketFull(int ticketId) async {
+  Future<ApiResponse<TicketFull>> getTicketFull(
+    int ticketId, {
+    required String customerKey,
+  }) async {
     return _request(
       'GET',
       '/tickets/$ticketId/full',
       parse: TicketFull.fromJson,
+      customerKey: customerKey,
     );
   }
 
@@ -158,6 +157,7 @@ class ShopInBitClient {
             .map((e) => TicketRef.fromJson(e as Map<String, dynamic>))
             .toList();
       },
+      customerKey: customerKey,
     );
   }
 
@@ -165,17 +165,22 @@ class ShopInBitClient {
 
   Future<ApiResponse<Map<String, dynamic>>> sendMessage(
     int ticketId,
-    String message,
-  ) async {
+    String message, {
+    required String customerKey,
+  }) async {
     return _request(
       'POST',
       '/tickets/$ticketId/messages',
       body: {'message': message},
       parse: (json) => json,
+      customerKey: customerKey,
     );
   }
 
-  Future<ApiResponse<List<TicketMessage>>> getMessages(int ticketId) async {
+  Future<ApiResponse<List<TicketMessage>>> getMessages(
+    int ticketId, {
+    required String customerKey,
+  }) async {
     return _request(
       'GET',
       '/tickets/$ticketId/messages',
@@ -185,6 +190,7 @@ class ShopInBitClient {
             .map((e) => TicketMessage.fromJson(e as Map<String, dynamic>))
             .toList();
       },
+      customerKey: customerKey,
     );
   }
 
@@ -194,12 +200,14 @@ class ShopInBitClient {
     int ticketId, {
     required String message,
     required List<Map<String, String>> attachments,
+    required String customerKey,
   }) async {
     return _request(
       'POST',
       '/tickets/$ticketId/attachments',
       body: {'message': message, 'attachments': attachments},
       parse: (json) => json,
+      customerKey: customerKey,
     );
   }
 
@@ -211,6 +219,7 @@ class ShopInBitClient {
   /// [useQueryAuth] = true to append token and customer_key as query params.
   Future<ApiResponse<Uri>> getAttachmentUrl(
     String attachmentPath, {
+    String? customerKey,
     bool useQueryAuth = false,
   }) async {
     try {
@@ -221,8 +230,7 @@ class ShopInBitClient {
         uri = uri.replace(
           queryParameters: {
             'token': token,
-            if (_externalCustomerKey != null)
-              'customer_key': _externalCustomerKey!,
+            if (customerKey != null) 'customer_key': customerKey,
           },
         );
       }
@@ -235,13 +243,16 @@ class ShopInBitClient {
   }
 
   /// Download an attachment from `/attachment-proxy/<path>`.
-  Future<ApiResponse<Response>> getAttachment(String attachmentPath) async {
+  Future<ApiResponse<Response>> getAttachment(
+    String attachmentPath, {
+    String? customerKey,
+  }) async {
     try {
       final token = await _tokenManager.getValidToken();
       final resolved = _resolvePath('/attachment-proxy/$attachmentPath');
       final uri = Uri.parse('$baseUrl$resolved');
       Logging.instance.t("$_kTag GET $uri");
-      final headers = _headers(token);
+      final headers = _headers(token, customerKey: customerKey);
       final response = await _httpClient.get(
         url: uri,
         headers: headers,
@@ -279,6 +290,7 @@ class ShopInBitClient {
   Future<ApiResponse<Map<String, dynamic>>> submitAddress(
     int ticketId, {
     required Address shipping,
+    required String customerKey,
     Address? billing,
   }) async {
     return _request(
@@ -286,6 +298,7 @@ class ShopInBitClient {
       '/tickets/$ticketId/address',
       body: {'shipping': shipping.toJson(), 'billing': billing?.toJson()},
       parse: (json) => json,
+      customerKey: customerKey,
     );
   }
 
@@ -295,11 +308,15 @@ class ShopInBitClient {
   /// and any view that just wants to show the current invoice; per ShopinBit
   /// 1.0.4 this endpoint is read-only and will not create or regenerate the
   /// invoice. Call [putPayment] for that.
-  Future<ApiResponse<PaymentInfo>> getPayment(int ticketId) async {
+  Future<ApiResponse<PaymentInfo>> getPayment(
+    int ticketId, {
+    required String customerKey,
+  }) async {
     return _request(
       'GET',
       '/tickets/$ticketId/payment',
       parse: PaymentInfo.fromJson,
+      customerKey: customerKey,
     );
   }
 
@@ -308,23 +325,31 @@ class ShopInBitClient {
   /// shipping/billing, seen the Terms & Conditions, and explicitly clicked
   /// PAY NOW.  Repeated calls regenerate the invoice and invalidate any in-
   /// flight payment.
-  Future<ApiResponse<PaymentInfo>> putPayment(int ticketId) async {
+  Future<ApiResponse<PaymentInfo>> putPayment(
+    int ticketId, {
+    required String customerKey,
+  }) async {
     return _request(
       'PUT',
       '/tickets/$ticketId/payment',
       parse: PaymentInfo.fromJson,
+      customerKey: customerKey,
     );
   }
 
   // -- Vouchers --
 
   /// Pre-check a voucher code (does not consume usage or create a ticket).
-  Future<ApiResponse<VoucherInfo>> checkVoucher(String code) async {
+  Future<ApiResponse<VoucherInfo>> checkVoucher(
+    String code, {
+    required String customerKey,
+  }) async {
     return _request(
       'GET',
       '/vouchers/validate',
       query: {'code': code},
       parse: VoucherInfo.fromJson,
+      customerKey: customerKey,
     );
   }
 
@@ -334,6 +359,7 @@ class ShopInBitClient {
     required String customerPseudonym,
     required String serviceType,
     required String comment,
+    required String customerKey,
     String? deliveryCountry,
   }) async {
     return _request(
@@ -347,6 +373,7 @@ class ShopInBitClient {
         if (deliveryCountry != null) 'delivery_country': deliveryCountry,
       },
       parse: VipRedemptionResult.fromJson,
+      customerKey: customerKey,
     );
   }
 
@@ -354,6 +381,7 @@ class ShopInBitClient {
 
   Future<ApiResponse<CarResearchInvoice>> createCarResearchInvoice({
     required Address billing,
+    required String customerKey,
     CarResearchRequest? request,
   }) async {
     return _request(
@@ -362,17 +390,17 @@ class ShopInBitClient {
       body: {
         'billing': billing.toJson(),
         if (request != null) 'request': request.toJson(),
-        if (_externalCustomerKey != null)
-          'external_customer_key': _externalCustomerKey,
+        'external_customer_key': customerKey,
       },
       parse: CarResearchInvoice.fromJson,
+      customerKey: customerKey,
     );
   }
 
   /// Unresolved car research invoices for the current partner/customer pair.
   /// Used to recover a fee payment the user started but did not finish.
   Future<ApiResponse<List<CarResearchCurrentInvoice>>>
-  getCurrentCarResearchInvoices() async {
+  getCurrentCarResearchInvoices({required String customerKey}) async {
     return _requestRaw(
       'GET',
       '/car-research/invoices/current',
@@ -390,31 +418,33 @@ class ShopInBitClient {
             )
             .toList();
       },
+      customerKey: customerKey,
     );
   }
 
   Future<ApiResponse<Map<String, dynamic>>> getCarResearchInvoiceStatus(
-    String invoiceId,
-  ) async {
+    String invoiceId, {
+    required String customerKey,
+  }) async {
     return _request(
       'GET',
       '/car-research/invoice/$invoiceId/status',
       parse: (json) => json,
+      customerKey: customerKey,
     );
   }
 
   Future<ApiResponse<CarResearchPaymentResult>> logCarResearchPayment(
-    String invoiceId,
-  ) async {
+    String invoiceId, {
+
+    required String customerKey,
+  }) async {
     return _request(
       'POST',
       '/car-research/log-payment',
-      body: {
-        'invoice_id': invoiceId,
-        if (_externalCustomerKey != null)
-          'external_customer_key': _externalCustomerKey,
-      },
+      body: {'invoice_id': invoiceId, 'external_customer_key': customerKey},
       parse: CarResearchPaymentResult.fromJson,
+      customerKey: customerKey,
     );
   }
 
@@ -428,6 +458,8 @@ class ShopInBitClient {
     String? environment,
     String? expirationTime,
     int? ticketId,
+
+    required String customerKey,
   }) async {
     return _request(
       'POST',
@@ -442,6 +474,7 @@ class ShopInBitClient {
         if (ticketId != null) 'ticketId': ticketId,
       },
       parse: (json) => json,
+      customerKey: customerKey,
     );
   }
 
@@ -451,7 +484,7 @@ class ShopInBitClient {
     return _request(
       'GET',
       '/partners/webhooks',
-      needsCustomerKey: false,
+      customerKey: null,
       parse: (json) {
         if (json.containsKey('webhooks')) {
           return (json['webhooks'] as List<dynamic>)
@@ -469,7 +502,7 @@ class ShopInBitClient {
     return _request(
       'POST',
       '/partners/webhooks',
-      needsCustomerKey: false,
+      customerKey: null,
       body: {'webhook_url': webhookUrl, 'event_types': eventTypes},
       parse: (json) => json,
     );
@@ -481,7 +514,7 @@ class ShopInBitClient {
     return _request(
       'POST',
       '/partners/webhooks/$webhookId/rotate',
-      needsCustomerKey: false,
+      customerKey: null,
       parse: (json) => json,
     );
   }
@@ -490,7 +523,7 @@ class ShopInBitClient {
     return _request(
       'DELETE',
       '/partners/webhooks/$webhookId',
-      needsCustomerKey: false,
+      customerKey: null,
       parse: (_) {},
     );
   }
@@ -499,23 +532,27 @@ class ShopInBitClient {
 
   Future<ApiResponse<Map<String, dynamic>>> sandboxSetState(
     int ticketId,
-    String state,
-  ) async {
+    String state, {
+    required String customerKey,
+  }) async {
     return _request(
       'POST',
       '/sandbox/state/$ticketId/$state',
       parse: (json) => json,
+      customerKey: customerKey,
     );
   }
 
   Future<ApiResponse<Map<String, dynamic>>> sandboxSetPayment(
     int ticketId,
-    String status,
-  ) async {
+    String status, {
+    required String customerKey,
+  }) async {
     return _request(
       'POST',
       '/sandbox/payment/$ticketId/$status',
       parse: (json) => json,
+      customerKey: customerKey,
     );
   }
 
@@ -542,14 +579,14 @@ class ShopInBitClient {
     return '/sandbox$path';
   }
 
-  Map<String, String> _headers(String token, {bool needsCustomerKey = true}) {
+  Map<String, String> _headers(String token, {String? customerKey}) {
     final h = <String, String>{
       'Authorization': 'Bearer $token',
       'Content-Type': 'application/json',
       'Accept': 'application/json',
     };
-    if (needsCustomerKey && _externalCustomerKey != null) {
-      h['External-Customer-Key'] = _externalCustomerKey!;
+    if (customerKey != null) {
+      h['External-Customer-Key'] = customerKey;
     }
     return h;
   }
@@ -559,7 +596,7 @@ class ShopInBitClient {
     String path, {
     Map<String, dynamic>? body,
     Map<String, String>? query,
-    bool needsCustomerKey = true,
+    required String? customerKey,
     bool needsAuth = true,
   }) async {
     final resolved = _resolvePath(path);
@@ -570,7 +607,7 @@ class ShopInBitClient {
     final Map<String, String> headers;
     if (needsAuth) {
       final token = await _tokenManager.getValidToken();
-      headers = _headers(token, needsCustomerKey: needsCustomerKey);
+      headers = _headers(token, customerKey: customerKey);
     } else {
       headers = {'Accept': 'application/json'};
     }
@@ -632,7 +669,7 @@ class ShopInBitClient {
     String path, {
     Map<String, dynamic>? body,
     Map<String, String>? query,
-    bool needsCustomerKey = true,
+    required String? customerKey,
     required T Function(Map<String, dynamic>) parse,
   }) async {
     try {
@@ -641,7 +678,7 @@ class ShopInBitClient {
         path,
         body: body,
         query: query,
-        needsCustomerKey: needsCustomerKey,
+        customerKey: customerKey,
       );
 
       final resolved = _resolvePath(path);
@@ -652,7 +689,7 @@ class ShopInBitClient {
           return ApiResponse(value: parse({}));
         }
         final json = jsonDecode(response.body) as Map<String, dynamic>;
-        return ApiResponse(value: parse(json));
+        return ApiResponse(value: parse(json), customerKey: customerKey);
       } else {
         Logging.instance.w(
           "$_kTag $method $resolved HTTP:${response.code} "
@@ -682,7 +719,7 @@ class ShopInBitClient {
     String path, {
     Map<String, dynamic>? body,
     Map<String, String>? query,
-    bool needsCustomerKey = true,
+    required String? customerKey,
     bool needsAuth = true,
     required T Function(String) parse,
   }) async {
@@ -692,7 +729,7 @@ class ShopInBitClient {
         path,
         body: body,
         query: query,
-        needsCustomerKey: needsCustomerKey,
+        customerKey: customerKey,
         needsAuth: needsAuth,
       );
 
diff --git a/lib/widgets/dialogs/nested_navigator_dialog/nested_navigator_dialog_route_generator.dart b/lib/widgets/dialogs/nested_navigator_dialog/nested_navigator_dialog_route_generator.dart
index 74e272c..eed491d 100644
--- a/lib/widgets/dialogs/nested_navigator_dialog/nested_navigator_dialog_route_generator.dart
+++ b/lib/widgets/dialogs/nested_navigator_dialog/nested_navigator_dialog_route_generator.dart
@@ -112,9 +112,12 @@ abstract final class NestedNavigatorDialogRouteGenerator {
         );
 
       case ShopInBitCarResearchPaymentView.routeName:
-        if (args is CarResearchInvoice) {
+        if (args is ({CarResearchInvoice invoice, String customerKey})) {
           return getRoute(
-            builder: (_) => ShopInBitCarResearchPaymentView(invoice: args),
+            builder: (_) => ShopInBitCarResearchPaymentView(
+              invoice: args.invoice,
+              customerKey: args.customerKey,
+            ),
             settings: RouteSettings(name: settings.name),
           );
         }