diff --git a/orders/views/payment.py b/orders/views/payment.py
index 0bcbc88..806d975 100644
--- a/orders/views/payment.py
+++ b/orders/views/payment.py
@@ -1318,13 +1318,20 @@ class CreateOrderView(APIView):
                 pay_sign = hashlib.md5(pay_sign_string.encode('utf-8')).hexdigest().upper()
 
                 # 返回支付参数（H5 JSAPI 必须带 appId；小程序可忽略）
+                # _diag 仅给 H5 诊断页展示商户号，调起支付时前端不会传给微信
                 result = {
                     'appId': APPID,
                     'timeStamp': timestamp,
                     'nonceStr': nonce_str,
                     'package': package,
                     'signType': 'MD5',
-                    'paySign': pay_sign
+                    'paySign': pay_sign,
+                    '_diag': {
+                        'mch_id': str(MCHID or ''),
+                        'club_id': str(club_id or ''),
+                        'appid': str(APPID or ''),
+                        'app_source': str(source or ''),
+                    },
                 }
 
                 return result
diff --git a/templates/wechat/h5_jsapi_pay.html b/templates/wechat/h5_jsapi_pay.html
index 1332b87..e7d1813 100644
--- a/templates/wechat/h5_jsapi_pay.html
+++ b/templates/wechat/h5_jsapi_pay.html
@@ -24,11 +24,17 @@
         }
         .ok { color: #07c160; }
         .err { color: #ff5a5a; }
+        .banner {
+            margin: 0 0 16px; padding: 14px 12px; border-radius: 10px;
+            background: #3a0000; border: 2px solid #ff2d2d; color: #ffe0e0;
+            font-size: 15px; font-weight: 700; line-height: 1.5; word-break: break-all;
+        }
     </style>
 </head>
 <body>
 <div class="wrap">
     <div class="title">微信支付（诊断模式）</div>
+    <div class="banner" id="banner">收款商户号加载中…</div>
     <div class="sub" id="tip">初始化…</div>
     <button class="btn" type="button" id="payBtn">立即支付 / 重试</button>
     <button class="btn gray" type="button" id="copyBtn">复制下方全部诊断到剪贴板</button>
@@ -41,10 +47,23 @@
     var btn = document.getElementById('payBtn');
     var copyBtn = document.getElementById('copyBtn');
     var logEl = document.getElementById('log');
+    var banner = document.getElementById('banner');
     var lines = [];
     var payload = null;
     var pay = null;
     var returnUrl = '';
+    var diag = {};
+
+    function setBanner() {
+        var mch = (diag && diag.mch_id) || '(未知，请看下方日志 payload.debug)';
+        var app = (pay && (pay.appId || pay.appid)) || (diag && diag.backendAppId) || '(未知)';
+        var club = (diag && diag.club_id) || '(未知)';
+        banner.innerHTML =
+            '【必须看】收款商户号 mch_id = <span style="color:#0f0">' + mch + '</span><br/>' +
+            'appId = ' + app + '<br/>' +
+            'club_id = ' + club + '<br/>' +
+            '请到<strong>这个商户号</strong>的后台配 JSAPI 目录：https://www.abas.asia/hqhd/dingdan/';
+    }
 
     function now() {
         try { return new Date().toISOString(); } catch (e) { return String(Date.now()); }
@@ -118,6 +137,10 @@
 
     pay = payload && payload.pay ? payload.pay : null;
     returnUrl = (payload && payload.returnUrl) || '';
+    diag = (payload && payload.debug) || {};
+    setBanner();
+    push('!!!! 收款商户号 mch_id', diag.mch_id || '(空——后端未返回 _diag，请先部署后端)');
+    push('payload.debug 完整', diag);
 
     dumpEnv('页面加载');
     push('payload.orderId', payload && payload.orderId);
@@ -223,22 +246,19 @@
                     push('当前校验 URL', checkUrl);
                     push('调起用的 appId', appId);
                     if (quick) {
-                        setTip('<span class="err">微信秒关并返回 cancel（常被误当成取消）</span><br/>不是「支付成功取消」。URL/appId 见下方，点重试或复制日志', true);
+                        setTip('<span class="err">微信秒关并返回 cancel</span><br/>顶部红框的 mch_id 才是要配目录的商户号', true);
                         try {
                             alert(
-                                '支付未完成（微信返回 cancel，且秒关）\n\n' +
-                                '这经常不是你手动取消，而是微信直接关掉收银台。\n' +
-                                '若屏幕曾闪过「URL未注册」，就是目录/商户仍不对。\n\n' +
-                                'appId=' + appId + '\n' +
-                                'URL=' + checkUrl + '\n' +
-                                '耗时=' + costMs + 'ms\n\n' +
-                                '完整日志在绿字区，点「复制」发给技术'
+                                '支付未完成（cancel 秒关）\n\n' +
+                                '【收款商户号 mch_id】\n' + ((diag && diag.mch_id) || '(未知，先部署后端)') + '\n\n' +
+                                '必须在这个商户后台配：\nhttps://www.abas.asia/hqhd/dingdan/\n\n' +
+                                'appId=' + appId + '\nURL=' + checkUrl + '\nms=' + costMs
                             );
                         } catch (e) {}
                     } else {
                         setTip('已取消支付。可点「立即支付」重试');
                         try {
-                            alert('已取消支付\n\n若其实没点取消、只看到「未注册」，请把绿字日志复制发给技术\n\nappId=' + appId + '\nURL=' + checkUrl);
+                            alert('已取消\nmch_id=' + ((diag && diag.mch_id) || '(未知)') + '\nappId=' + appId + '\nURL=' + checkUrl);
                         } catch (e) {}
                     }
                     return;