diff --git a/backend/internal/handler/pay.go b/backend/internal/handler/pay.go
index f585dd1..5579461 100644
--- a/backend/internal/handler/pay.go
+++ b/backend/internal/handler/pay.go
@@ -4,6 +4,7 @@ import (
 	"errors"
 	"log"
 	"net/http"
+	"strings"
 
 	"github.com/gin-gonic/gin"
 
@@ -12,6 +13,17 @@ import (
 	"github.com/wangjia/jiu/backend/internal/util"
 )
 
+// isMobileUA 判断是否手机浏览器（词表与 pay 侧 handler/order.go 保持一致）。
+func isMobileUA(ua string) bool {
+	ua = strings.ToLower(ua)
+	for _, kw := range []string{"android", "iphone", "ipod", "mobile", "harmony", "windows phone"} {
+		if strings.Contains(ua, kw) {
+			return true
+		}
+	}
+	return false
+}
+
 type PayHandler struct {
 	svc *service.PayService
 }
@@ -30,13 +42,24 @@ func (h *PayHandler) Purchase(c *gin.Context) {
 	}
 	var req struct {
 		BizCode string `json:"biz_code" binding:"required"`
+		// 终端类型（可选，"pc"/"mobile"）：App 显式声明优先；缺省按本请求 UA 判断
+		// （官网浏览器购买的 UA 是真实终端 UA）。透传给 pay 决定收银台形态。
+		ClientType string `json:"client_type" binding:"omitempty,oneof=pc mobile"`
 	}
 	if err := c.ShouldBindJSON(&req); err != nil {
 		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
 		return
 	}
+	clientType := req.ClientType
+	if clientType == "" {
+		if isMobileUA(c.Request.UserAgent()) {
+			clientType = "mobile"
+		} else {
+			clientType = "pc"
+		}
+	}
 
-	res, err := h.svc.CreatePurchase(middleware.GetShopID(c), middleware.GetUserID(c), req.BizCode)
+	res, err := h.svc.CreatePurchase(middleware.GetShopID(c), middleware.GetUserID(c), req.BizCode, clientType)
 	if err != nil {
 		switch {
 		case errors.Is(err, service.ErrPayNotConfigured):
diff --git a/backend/internal/service/pay.go b/backend/internal/service/pay.go
index 078be9d..38a866d 100644
--- a/backend/internal/service/pay.go
+++ b/backend/internal/service/pay.go
@@ -90,7 +90,10 @@ type PurchaseResult struct {
 }
 
 // CreatePurchase 建购买记录并调 pay 下单，返回收银台跳转 URL。
-func (s *PayService) CreatePurchase(shopID, userID uint64, bizCode string) (*PurchaseResult, error) {
+// clientType（契约 v1.1.0，"pc"/"mobile"/""）：显式端型透传给 pay 决定收银台形态
+// （mobile=手机网站支付拉起支付宝 App / pc=电脑扫码页）；服务端间调用下单请求 UA
+// 是本后端的，不传则 pay 会按 Go client UA 误判为 PC。
+func (s *PayService) CreatePurchase(shopID, userID uint64, bizCode, clientType string) (*PurchaseResult, error) {
 	if !s.Configured() {
 		return nil, ErrPayNotConfigured
 	}
@@ -117,12 +120,16 @@ func (s *PayService) CreatePurchase(shopID, userID uint64, bizCode string) (*Pur
 		return nil, err
 	}
 
-	reqBody, _ := json.Marshal(map[string]any{
+	payload := map[string]any{
 		"product_id": productID,
 		"biz_system": "jiu",
 		"biz_ref":    strconv.FormatUint(p.ID, 10),
 		"return_url": s.retURL,
-	})
+	}
+	if clientType != "" {
+		payload["client_type"] = clientType
+	}
+	reqBody, _ := json.Marshal(payload)
 	respBody, err := s.signedPost("/api/v1/orders", reqBody)
 	if err != nil {
 		return nil, fmt.Errorf("pay 下单失败: %w", err)
diff --git a/backend/internal/service/pay_test.go b/backend/internal/service/pay_test.go
index 53ac1ee..87f5555 100644
--- a/backend/internal/service/pay_test.go
+++ b/backend/internal/service/pay_test.go
@@ -234,7 +234,7 @@ func TestCreatePurchase_HappyPath(t *testing.T) {
 	mux.HandleFunc("GET /api/v1/products", func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprint(w, `{"data":[{"id":3,"biz_code":"annual_standard"},{"id":4,"biz_code":"monthly_pro"}]}`)
 	})
-	var gotBizRef string
+	var gotBizRef, gotClientType string
 	mux.HandleFunc("POST /api/v1/orders", func(w http.ResponseWriter, r *http.Request) {
 		body := make([]byte, r.ContentLength)
 		_, _ = r.Body.Read(body)
@@ -246,13 +246,14 @@ func TestCreatePurchase_HappyPath(t *testing.T) {
 		var req map[string]any
 		_ = json.Unmarshal(body, &req)
 		gotBizRef, _ = req["biz_ref"].(string)
+		gotClientType, _ = req["client_type"].(string)
 		fmt.Fprint(w, `{"data":{"pay_url":"https://openapi.alipay.com/gateway","out_trade_no":"yanmei-new-1","amount":"2999.00","subject":"年付标准"}}`)
 	})
 	payServer := httptest.NewServer(mux)
 	defer payServer.Close()
 
 	svc := newTestPaySvc(db, payServer.URL)
-	res, err := svc.CreatePurchase(shop.ID, 1, "annual_standard")
+	res, err := svc.CreatePurchase(shop.ID, 1, "annual_standard", "mobile")
 	require.NoError(t, err)
 	assert.Equal(t, "https://openapi.alipay.com/gateway", res.PayURL)
 	assert.Equal(t, "yanmei-new-1", res.OutTradeNo)
@@ -262,16 +263,17 @@ func TestCreatePurchase_HappyPath(t *testing.T) {
 	assert.Equal(t, "pending", p.Status)
 	assert.Equal(t, "2999.00", p.Amount)
 	assert.Equal(t, strconv.FormatUint(p.ID, 10), gotBizRef, "biz_ref 应为购买记录 id")
+	assert.Equal(t, "mobile", gotClientType, "client_type 应透传给 pay（契约 v1.1.0）")
 }
 
 func TestCreatePurchase_UnknownPlanAndUnconfigured(t *testing.T) {
 	db := testutil.SetupTestDB()
 	svc := newTestPaySvc(db, "http://pay.invalid")
-	_, err := svc.CreatePurchase(1, 1, "no_such_plan")
+	_, err := svc.CreatePurchase(1, 1, "no_such_plan", "pc")
 	assert.ErrorIs(t, err, ErrUnknownPlan)
 
 	unconfigured := NewPayService(db, "http://pay.invalid", "", "")
-	_, err = unconfigured.CreatePurchase(1, 1, "annual_standard")
+	_, err = unconfigured.CreatePurchase(1, 1, "annual_standard", "pc")
 	assert.ErrorIs(t, err, ErrPayNotConfigured)
 }
 
@@ -287,7 +289,7 @@ func TestCreatePurchase_PromoOncePerShop(t *testing.T) {
 	used, err := svc.PromoUsed(shop.ID)
 	require.NoError(t, err)
 	assert.False(t, used)
-	_, err = svc.CreatePurchase(shop.ID, 1, PromoBizCode)
+	_, err = svc.CreatePurchase(shop.ID, 1, PromoBizCode, "pc")
 	assert.NotErrorIs(t, err, ErrPromoUsed)
 
 	// pending 单不算已享用（可能弃单），仍可重新下单
@@ -302,7 +304,7 @@ func TestCreatePurchase_PromoOncePerShop(t *testing.T) {
 	used, err = svc.PromoUsed(shop.ID)
 	require.NoError(t, err)
 	assert.True(t, used)
-	_, err = svc.CreatePurchase(shop.ID, 1, PromoBizCode)
+	_, err = svc.CreatePurchase(shop.ID, 1, PromoBizCode, "pc")
 	assert.ErrorIs(t, err, ErrPromoUsed)
 
 	// 多租户隔离：别家买过不影响本店
diff --git a/client/lib/repositories/license_repository.dart b/client/lib/repositories/license_repository.dart
index c8b1b28..c98fb31 100644
--- a/client/lib/repositories/license_repository.dart
+++ b/client/lib/repositories/license_repository.dart
@@ -41,10 +41,16 @@ class LicenseRepository {
   }
 
   /// 在线购买/续费下单（仅管理员），返回 pay 收银台跳转信息。
-  Future<PurchaseOrder> createPurchase(String bizCode) async {
+  /// [clientType] 终端类型（"pc"/"mobile"，可选）：显式声明收银台形态——
+  /// mobile 走支付宝手机网站支付（H5 拉起 App），pc 走电脑扫码页；
+  /// 不传时后端按请求 UA 判断（浏览器场景 UA 真实，App 场景须显式传）。
+  Future<PurchaseOrder> createPurchase(String bizCode,
+      {String? clientType}) async {
     try {
-      final resp =
-          await _client.post('/license/purchase', data: {'biz_code': bizCode});
+      final resp = await _client.post('/license/purchase', data: {
+        'biz_code': bizCode,
+        if (clientType != null) 'client_type': clientType,
+      });
       return PurchaseOrder.fromJson(resp.data['data'] as Map<String, dynamic>);
     } on DioException catch (e) {
       throw AppException(
diff --git a/client/lib/screens/settings/purchase_card.dart b/client/lib/screens/settings/purchase_card.dart
index c3beb07..c1884cc 100644
--- a/client/lib/screens/settings/purchase_card.dart
+++ b/client/lib/screens/settings/purchase_card.dart
@@ -4,7 +4,9 @@
 // GET /license/purchase/:otn，webhook 续期到账后自动刷新授权并展示新到期日。
 // 价格仅展示，实付以 pay 侧套餐表为准（下单响应回传 amount）。
 import 'dart:async';
+import 'dart:io' show Platform;
 
+import 'package:flutter/foundation.dart' show kIsWeb;
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:intl/intl.dart';
@@ -73,13 +75,22 @@ class _PurchaseCardState extends ConsumerState<PurchaseCard> {
     super.dispose();
   }
 
+  /// 终端类型（契约 v1.1.0）：手机 App 显式声明 mobile 让 pay 出「手机网站支付」
+  /// 收银台（H5 拉起支付宝 App）；桌面 App 声明 pc（扫码页）；Web 端不传，
+  /// 后端按浏览器真实 UA 判断。kIsWeb 判断先于 dart:io（项目规则）。
+  String? get _clientType {
+    if (kIsWeb) return null;
+    return (Platform.isIOS || Platform.isAndroid) ? 'mobile' : 'pc';
+  }
+
   Future<void> _submit() async {
     setState(() => _submitting = true);
     try {
       final order = await ref
           .read(licenseRepositoryProvider)
-          .createPurchase(_plan.bizCode);
-      // 外部浏览器打开收银台：桌面端进网页支付，移动端由系统浏览器拉起支付宝
+          .createPurchase(_plan.bizCode, clientType: _clientType);
+      // 外部浏览器打开收银台：桌面端进网页支付，移动端由系统浏览器打开
+      // wap 收银台自动拉起支付宝 App
       await launchUrl(Uri.parse(order.payUrl),
           mode: LaunchMode.externalApplication);
       if (!mounted) return;