diff --git a/src/__tests__/payment-flow.test.ts b/src/__tests__/payment-flow.test.ts
index c141612..1e9cc3e 100644
--- a/src/__tests__/payment-flow.test.ts
+++ b/src/__tests__/payment-flow.test.ts
@@ -193,7 +193,7 @@ describe('Payment Flow - PC/Mobile, QR/Redirect', () => {
       ).toBe(true);
     });
 
-    it('EasyPay does not use isMobile flag itself (delegates to frontend)', async () => {
+    it('EasyPay forwards isMobile to client for device=jump on mobile', async () => {
       mockEasyPayCreatePayment.mockResolvedValue({
         code: 1,
         trade_no: 'EP-003',
@@ -212,16 +212,14 @@ describe('Payment Flow - PC/Mobile, QR/Redirect', () => {
 
       await provider.createPayment(request);
 
-      // EasyPay client is called the same way regardless of isMobile
+      // EasyPay client receives isMobile so it can set device=jump
       expect(mockEasyPayCreatePayment).toHaveBeenCalledWith(
         expect.objectContaining({
           outTradeNo: 'order-ep-003',
           paymentType: 'alipay',
+          isMobile: true,
         }),
       );
-      // No isMobile parameter forwarded to the underlying client
-      const callArgs = mockEasyPayCreatePayment.mock.calls[0][0];
-      expect(callArgs).not.toHaveProperty('isMobile');
     });
   });
 
diff --git a/src/lib/easy-pay/client.ts b/src/lib/easy-pay/client.ts
index 597a72e..6563bdb 100644
--- a/src/lib/easy-pay/client.ts
+++ b/src/lib/easy-pay/client.ts
@@ -9,6 +9,7 @@ export interface CreatePaymentOptions {
   clientIp: string;
   productName: string;
   returnUrl?: string;
+  isMobile?: boolean;
 }
 
 function normalizeCidList(cid?: string): string | undefined {
@@ -68,6 +69,10 @@ export async function createPayment(opts: CreatePaymentOptions): Promise<EasyPay
     params.cid = cid;
   }
 
+  if (opts.isMobile) {
+    params.device = 'jump';
+  }
+
   const sign = generateSign(params, env.EASY_PAY_PKEY);
   params.sign = sign;
   params.sign_type = 'MD5';
diff --git a/src/lib/easy-pay/provider.ts b/src/lib/easy-pay/provider.ts
index 41707bc..4a30a6d 100644
--- a/src/lib/easy-pay/provider.ts
+++ b/src/lib/easy-pay/provider.ts
@@ -29,6 +29,7 @@ export class EasyPayProvider implements PaymentProvider {
       clientIp: request.clientIp || '127.0.0.1',
       productName: request.subject,
       returnUrl: request.returnUrl,
+      isMobile: request.isMobile,
     });
 
     return {