diff --git a/apps/mall/pages/checkout/index.vue b/apps/mall/pages/checkout/index.vue
index 5698fb1..4729584 100644
--- a/apps/mall/pages/checkout/index.vue
+++ b/apps/mall/pages/checkout/index.vue
@@ -117,6 +117,11 @@ async function loadCart(): Promise<void> {
     items.value = snapshot.items;
     addresses.value = list;
     coupons.value = couponList;
+    // A stashed group intent only applies while its SKU is still in the cart.
+    const intent = groupIntent.value;
+    if (intent && !items.value.some((item) => item.sku_id === intent.sku_id)) {
+      groupIntent.value = null;
+    }
     selectedAddressId.value =
       list.find((address) => address.is_default)?.id ?? list[0]?.id ?? "";
     if (items.value.length === 0) {
@@ -162,6 +167,12 @@ async function submitOrder(): Promise<void> {
 }
 
 onMounted(() => void loadCart());
+
+// Leaving without submitting must not reprice a later order: the intent is
+// consumed by a successful submit, which clears it before navigating to pay.
+onBeforeUnmount(() => {
+  groupIntent.value = null;
+});
 </script>
 
 <template>
diff --git a/apps/mall/pages/collective.vue b/apps/mall/pages/collective.vue
index e26aeb0..de79425 100644
--- a/apps/mall/pages/collective.vue
+++ b/apps/mall/pages/collective.vue
@@ -54,6 +54,9 @@ async function start(activity: GroupBuyingActivityView, open: boolean): Promise<
   workingId.value = activity.id;
   try {
     await $api.addCartItem(activity.sku_id, 1);
+    // The intent is quantity-1 only, so normalise in case the SKU was already in
+    // the cart or a previous attempt failed.
+    await $api.updateCartItem(activity.sku_id, 1);
     await cart.refresh();
     useState<GroupBuyIntent | null>("checkout-group-intent", () => null).value = {
       activity_id: activity.id,