diff --git a/background.js b/background.js
index cf59b2d..8b6e64d 100644
--- a/background.js
+++ b/background.js
@@ -239,6 +239,7 @@ const SUB2API_STEP1_RESPONSE_TIMEOUT_MS = 90000;
 const SUB2API_STEP9_RESPONSE_TIMEOUT_MS = 120000;
 const DEFAULT_SUB2API_URL = 'https://sub2api.hisence.fun/admin/accounts';
 const DEFAULT_CODEX2API_URL = 'http://localhost:8080/admin/accounts';
+const DEFAULT_GPC_HELPER_API_URL = 'https://gopay.hwork.pro';
 const DEFAULT_SUB2API_GROUP_NAME = 'codex';
 const DEFAULT_SUB2API_PROXY_NAME = '';
 const CONTRIBUTION_SOURCE_CPA = 'cpa';
@@ -603,7 +604,7 @@ const PERSISTED_SETTING_DEFAULTS = {
   gopayPhone: '',
   gopayOtp: '',
   gopayPin: '',
-  gopayHelperApiUrl: '',
+  gopayHelperApiUrl: DEFAULT_GPC_HELPER_API_URL,
   gopayHelperCardKey: '',
   gopayHelperPhoneNumber: '',
   gopayHelperCountryCode: '+86',
@@ -2213,9 +2214,13 @@ function normalizePersistentSettingValue(key, value) {
         ? self.GoPayUtils.normalizeGoPayCountryCode(value)
         : String(value || '+86').trim();
     case 'gopayHelperApiUrl':
-      return self.GoPayUtils?.normalizeGpcHelperBaseUrl
-        ? self.GoPayUtils.normalizeGpcHelperBaseUrl(value)
-        : String(value || '').trim().replace(/\/+$/g, '');
+      {
+        const defaultGpcHelperApiUrl = PERSISTED_SETTING_DEFAULTS.gopayHelperApiUrl
+          || (typeof DEFAULT_GPC_HELPER_API_URL !== 'undefined' ? DEFAULT_GPC_HELPER_API_URL : 'https://gopay.hwork.pro');
+        return self.GoPayUtils?.normalizeGpcHelperBaseUrl
+          ? self.GoPayUtils.normalizeGpcHelperBaseUrl(value || defaultGpcHelperApiUrl)
+          : String(value || defaultGpcHelperApiUrl).trim().replace(/\/+$/g, '');
+      }
     case 'gopayHelperCardKey':
     case 'gopayHelperReferenceId':
     case 'gopayHelperGoPayGuid':
@@ -9387,13 +9392,13 @@ async function maybeSwitchIpProxyAfterAutoRunRoundSuccess(payload = {}) {
 
 function resolveGpcHelperBaseUrl(apiUrl = '') {
   if (self.GoPayUtils?.normalizeGpcHelperBaseUrl) {
-    return self.GoPayUtils.normalizeGpcHelperBaseUrl(apiUrl);
+    return self.GoPayUtils.normalizeGpcHelperBaseUrl(apiUrl || DEFAULT_GPC_HELPER_API_URL);
   }
-  let normalized = String(apiUrl || '').trim().replace(/\/+$/g, '');
+  let normalized = String(apiUrl || DEFAULT_GPC_HELPER_API_URL).trim().replace(/\/+$/g, '');
   normalized = normalized.replace(/\/api\/checkout\/start$/i, '');
   normalized = normalized.replace(/\/api\/gopay\/(?:otp|pin)$/i, '');
   normalized = normalized.replace(/\/api\/card\/balance(?:\?.*)?$/i, '');
-  return normalized;
+  return normalized || DEFAULT_GPC_HELPER_API_URL;
 }
 
 function buildGpcCardBalanceRequestUrl(apiUrl = '', cardKey = '') {
@@ -9423,7 +9428,7 @@ function formatGpcCardBalancePayload(payload = {}) {
 }
 
 async function refreshGpcCardBalance(state = {}, options = {}) {
-  const apiUrl = String(state?.gopayHelperApiUrl || '').trim();
+  const apiUrl = resolveGpcHelperBaseUrl(state?.gopayHelperApiUrl || DEFAULT_GPC_HELPER_API_URL);
   const cardKey = String(state?.gopayHelperCardKey || state?.gpcCardKey || state?.cardKey || '').trim();
   if (!apiUrl) {
     throw new Error('缺少 GPC API 地址。');
diff --git a/background/steps/create-plus-checkout.js b/background/steps/create-plus-checkout.js
index e108a16..8e1b67b 100644
--- a/background/steps/create-plus-checkout.js
+++ b/background/steps/create-plus-checkout.js
@@ -7,6 +7,7 @@
   const PLUS_PAYMENT_METHOD_PAYPAL = 'paypal';
   const PLUS_PAYMENT_METHOD_GOPAY = 'gopay';
   const PLUS_PAYMENT_METHOD_GPC_HELPER = 'gpc-helper';
+  const DEFAULT_GPC_HELPER_API_URL = 'https://gopay.hwork.pro';
 
   function createPlusCheckoutCreateExecutor(deps = {}) {
     const {
@@ -200,11 +201,11 @@
       if (rootScope.GoPayUtils?.normalizeGpcHelperBaseUrl) {
         return rootScope.GoPayUtils.normalizeGpcHelperBaseUrl(apiUrl);
       }
-      let normalized = String(apiUrl || '').trim().replace(/\/+$/g, '');
+      let normalized = String(apiUrl || DEFAULT_GPC_HELPER_API_URL).trim().replace(/\/+$/g, '');
       normalized = normalized.replace(/\/api\/checkout\/start$/i, '');
       normalized = normalized.replace(/\/api\/gopay\/(?:otp|pin)$/i, '');
       normalized = normalized.replace(/\/api\/card\/balance(?:\?.*)?$/i, '');
-      return normalized;
+      return normalized || DEFAULT_GPC_HELPER_API_URL;
     }
 
     function buildGpcHelperApiUrl(apiUrl = '', path = '') {
diff --git a/background/steps/fill-plus-checkout.js b/background/steps/fill-plus-checkout.js
index 62f4778..692b2dd 100644
--- a/background/steps/fill-plus-checkout.js
+++ b/background/steps/fill-plus-checkout.js
@@ -10,6 +10,7 @@
   const PLUS_PAYMENT_METHOD_PAYPAL = 'paypal';
   const PLUS_PAYMENT_METHOD_GOPAY = 'gopay';
   const PLUS_PAYMENT_METHOD_GPC_HELPER = 'gpc-helper';
+  const DEFAULT_GPC_HELPER_API_URL = 'https://gopay.hwork.pro';
   const PAYMENT_METHOD_CONFIGS = {
     [PLUS_PAYMENT_METHOD_PAYPAL]: {
       id: PLUS_PAYMENT_METHOD_PAYPAL,
@@ -111,11 +112,11 @@
       if (rootScope.GoPayUtils?.normalizeGpcHelperBaseUrl) {
         return rootScope.GoPayUtils.normalizeGpcHelperBaseUrl(apiUrl);
       }
-      let normalized = String(apiUrl || '').trim().replace(/\/+$/g, '');
+      let normalized = String(apiUrl || DEFAULT_GPC_HELPER_API_URL).trim().replace(/\/+$/g, '');
       normalized = normalized.replace(/\/api\/checkout\/start$/i, '');
       normalized = normalized.replace(/\/api\/gopay\/(?:otp|pin)$/i, '');
       normalized = normalized.replace(/\/api\/card\/balance(?:\?.*)?$/i, '');
-      return normalized;
+      return normalized || DEFAULT_GPC_HELPER_API_URL;
     }
 
     async function fetchJsonWithTimeout(url, options = {}, timeoutMs = 30000) {
diff --git a/gopay-utils.js b/gopay-utils.js
index a24ef8d..462f034 100644
--- a/gopay-utils.js
+++ b/gopay-utils.js
@@ -4,6 +4,7 @@
   const PLUS_PAYMENT_METHOD_PAYPAL = 'paypal';
   const PLUS_PAYMENT_METHOD_GOPAY = 'gopay';
   const PLUS_PAYMENT_METHOD_GPC_HELPER = 'gpc-helper';
+  const DEFAULT_GPC_HELPER_API_URL = 'https://gopay.hwork.pro';
 
   function normalizePlusPaymentMethod(value = '') {
     const normalized = String(value || '').trim().toLowerCase();
@@ -46,15 +47,15 @@
   }
 
   function normalizeGpcHelperBaseUrl(apiUrl = '') {
-    let normalized = String(apiUrl || '').trim();
+    let normalized = String(apiUrl || DEFAULT_GPC_HELPER_API_URL).trim();
     if (!normalized) {
-      return '';
+      return DEFAULT_GPC_HELPER_API_URL;
     }
     normalized = normalized.replace(/\/+$/g, '');
     normalized = normalized.replace(/\/api\/checkout\/start$/i, '');
     normalized = normalized.replace(/\/api\/gopay\/(?:otp|pin)$/i, '');
     normalized = normalized.replace(/\/api\/card\/balance(?:\?.*)?$/i, '');
-    return normalized;
+    return normalized || DEFAULT_GPC_HELPER_API_URL;
   }
 
   function buildGpcHelperApiUrl(apiUrl = '', path = '') {
@@ -194,6 +195,7 @@
 
   return {
     DEFAULT_GOPAY_COUNTRY_CODE,
+    DEFAULT_GPC_HELPER_API_URL,
     PLUS_PAYMENT_METHOD_GPC_HELPER,
     PLUS_PAYMENT_METHOD_GOPAY,
     PLUS_PAYMENT_METHOD_PAYPAL,
diff --git a/sidepanel/sidepanel.html b/sidepanel/sidepanel.html
index 11bf79f..a80d989 100644
--- a/sidepanel/sidepanel.html
+++ b/sidepanel/sidepanel.html
@@ -279,10 +279,6 @@
           <button id="btn-add-paypal-account" class="btn btn-outline btn-sm data-inline-btn" type="button">添加</button>
         </div>
       </div>
-      <div class="data-row" id="row-gpc-helper-api" style="display:none;">
-        <span class="data-label">GPC API</span>
-        <input type="text" id="input-gpc-helper-api" class="data-input" placeholder="https://gopay.hwork.pro" />
-      </div>
       <div class="data-row" id="row-gpc-helper-card-key" style="display:none;">
         <span class="data-label">GPC 卡密</span>
         <div class="data-inline">
diff --git a/sidepanel/sidepanel.js b/sidepanel/sidepanel.js
index 7ba4544..6e60951 100644
--- a/sidepanel/sidepanel.js
+++ b/sidepanel/sidepanel.js
@@ -478,6 +478,7 @@ const stepsList = document.querySelector('.steps-list');
 const PLUS_PAYMENT_METHOD_PAYPAL = 'paypal';
 const PLUS_PAYMENT_METHOD_GOPAY = 'gopay';
 const PLUS_PAYMENT_METHOD_GPC_HELPER = 'gpc-helper';
+const DEFAULT_GPC_HELPER_API_URL = 'https://gopay.hwork.pro';
 const DEFAULT_PLUS_PAYMENT_METHOD = PLUS_PAYMENT_METHOD_PAYPAL;
 const SIGNUP_METHOD_EMAIL = 'email';
 const SIGNUP_METHOD_PHONE = 'phone';
@@ -2773,6 +2774,9 @@ function applyCloudflareTempEmailSettingsState(state = {}) {
 }
 
 function collectSettingsPayload() {
+  const defaultGpcHelperApiUrl = typeof DEFAULT_GPC_HELPER_API_URL !== 'undefined'
+    ? DEFAULT_GPC_HELPER_API_URL
+    : 'https://gopay.hwork.pro';
   const { domains, activeDomain } = getCloudflareDomainsFromState();
   const selectedCloudflareDomain = normalizeCloudflareDomainValue(
     !cloudflareDomainEditMode ? selectCfDomain.value : activeDomain
@@ -3303,10 +3307,10 @@ function collectSettingsPayload() {
         ? String(inputGoPayPin.value || '')
         : String(latestState?.gopayPin || '')),
     gopayHelperApiUrl: window.GoPayUtils?.normalizeGpcHelperBaseUrl
-      ? window.GoPayUtils.normalizeGpcHelperBaseUrl(typeof inputGpcHelperApi !== 'undefined' && inputGpcHelperApi ? inputGpcHelperApi.value : latestState?.gopayHelperApiUrl)
+      ? window.GoPayUtils.normalizeGpcHelperBaseUrl(typeof inputGpcHelperApi !== 'undefined' && inputGpcHelperApi ? inputGpcHelperApi.value : (latestState?.gopayHelperApiUrl || defaultGpcHelperApiUrl))
       : (typeof inputGpcHelperApi !== 'undefined' && inputGpcHelperApi
-        ? String(inputGpcHelperApi.value || '').trim().replace(/\/+$/g, '')
-        : String(latestState?.gopayHelperApiUrl || '').trim()),
+        ? String(inputGpcHelperApi.value || defaultGpcHelperApiUrl).trim().replace(/\/+$/g, '')
+        : String(latestState?.gopayHelperApiUrl || defaultGpcHelperApiUrl).trim()),
     gopayHelperCardKey: typeof inputGpcHelperCardKey !== 'undefined' && inputGpcHelperCardKey
       ? String(inputGpcHelperCardKey.value || '').trim()
       : String(latestState?.gopayHelperCardKey || '').trim(),
@@ -7044,7 +7048,7 @@ function updatePlusModeUI() {
   }
   if (typeof plusPaymentMethodCaption !== 'undefined' && plusPaymentMethodCaption) {
     plusPaymentMethodCaption.textContent = method === gpcValue
-      ? 'GPC API 订阅链路'
+      ? 'GPC 订阅链路'
       : method === gopayValue
       ? 'GoPay 印尼订阅链路'
       : 'PayPal 订阅链路';
@@ -7069,7 +7073,6 @@ function updatePlusModeUI() {
     row.style.display = enabled && selectedMethod === paypalValue ? '' : 'none';
   });
   [
-    typeof rowGpcHelperApi !== 'undefined' ? rowGpcHelperApi : null,
     typeof rowGpcHelperCardKey !== 'undefined' ? rowGpcHelperCardKey : null,
     typeof rowGpcHelperCountryCode !== 'undefined' ? rowGpcHelperCountryCode : null,
     typeof rowGpcHelperPhone !== 'undefined' ? rowGpcHelperPhone : null,
@@ -7788,7 +7791,10 @@ function applySettingsState(state) {
     selectPlusPaymentMethod.value = normalizePlusPaymentMethod(state?.plusPaymentMethod);
   }
   if (typeof inputGpcHelperApi !== 'undefined' && inputGpcHelperApi) {
-    inputGpcHelperApi.value = state?.gopayHelperApiUrl || '';
+    const defaultGpcHelperApiUrl = typeof DEFAULT_GPC_HELPER_API_URL !== 'undefined'
+      ? DEFAULT_GPC_HELPER_API_URL
+      : 'https://gopay.hwork.pro';
+    inputGpcHelperApi.value = state?.gopayHelperApiUrl || defaultGpcHelperApiUrl;
   }
   if (typeof inputGpcHelperCardKey !== 'undefined' && inputGpcHelperCardKey) {
     inputGpcHelperCardKey.value = state?.gopayHelperCardKey || '';
@@ -11204,7 +11210,7 @@ btnGpcHelperBalance?.addEventListener('click', async () => {
       type: 'REFRESH_GPC_CARD_BALANCE',
       source: 'sidepanel',
       payload: {
-        gopayHelperApiUrl: inputGpcHelperApi?.value || '',
+        gopayHelperApiUrl: inputGpcHelperApi?.value || DEFAULT_GPC_HELPER_API_URL,
         gopayHelperCardKey: inputGpcHelperCardKey?.value || '',
         gopayHelperCountryCode: selectGpcHelperCountryCode?.value || '+86',
         reason: 'manual',
diff --git a/tests/background-account-history-settings.test.js b/tests/background-account-history-settings.test.js
index 0b4ca5d..b72c0c6 100644
--- a/tests/background-account-history-settings.test.js
+++ b/tests/background-account-history-settings.test.js
@@ -154,6 +154,7 @@ const self = {
 };
 const PERSISTED_SETTING_DEFAULTS = {
   autoStepDelaySeconds: null,
+  gopayHelperApiUrl: 'https://gopay.hwork.pro',
   mailProvider: '163',
 };
 function normalizePanelMode(value) { return value === 'sub2api' ? 'sub2api' : (value === 'codex2api' ? 'codex2api' : 'cpa'); }
@@ -191,6 +192,7 @@ return {
     api.normalizePersistentSettingValue('gopayHelperApiUrl', ' https://gopay.hwork.pro/api/checkout/start '),
     'https://gopay.hwork.pro'
   );
+  assert.equal(api.normalizePersistentSettingValue('gopayHelperApiUrl', ''), 'https://gopay.hwork.pro');
   assert.equal(api.normalizePersistentSettingValue('gopayHelperCardKey', ' card_123 '), 'card_123');
   assert.equal(api.normalizePersistentSettingValue('gopayHelperCountryCode', ' 86 '), '+86');
   assert.equal(api.normalizePersistentSettingValue('gopayHelperPhoneNumber', ' +86 138-0013-8000 '), '+8613800138000');
diff --git a/tests/gopay-utils.test.js b/tests/gopay-utils.test.js
index 0e08506..f5967a7 100644
--- a/tests/gopay-utils.test.js
+++ b/tests/gopay-utils.test.js
@@ -23,6 +23,12 @@ test('GoPay utils keeps GPC helper payment method distinct', () => {
 
 test('GoPay utils builds GPC card balance URL from helper endpoints', () => {
   const api = loadGoPayUtils();
+  assert.equal(api.DEFAULT_GPC_HELPER_API_URL, 'https://gopay.hwork.pro');
+  assert.equal(api.normalizeGpcHelperBaseUrl(''), 'https://gopay.hwork.pro');
+  assert.equal(
+    api.buildGpcHelperApiUrl('', '/api/checkout/start'),
+    'https://gopay.hwork.pro/api/checkout/start'
+  );
   assert.equal(
     api.buildGpcCardBalanceUrl('http://localhost:18473/', ' card key/1 '),
     'http://localhost:18473/api/card/balance?card_key=card%20key%2F1'
diff --git a/tests/sidepanel-plus-payment-method.test.js b/tests/sidepanel-plus-payment-method.test.js
index c81e807..ca141fc 100644
--- a/tests/sidepanel-plus-payment-method.test.js
+++ b/tests/sidepanel-plus-payment-method.test.js
@@ -204,7 +204,7 @@ return {
   });
 });
 
-test('sidepanel Plus UI shows GPC fields and purchase button only for GPC', () => {
+test('sidepanel Plus UI shows GPC fields and purchase button only for GPC without API input', () => {
   const bundle = [
     extractFunction('normalizePlusPaymentMethod'),
     extractFunction('getSelectedPlusPaymentMethod'),
@@ -244,7 +244,7 @@ return {
 
   assert.equal(api.rowPayPalAccount.style.display, 'none');
   assert.equal(api.btnGpcCardKeyPurchase.style.display, '');
-  assert.equal(api.rows.rowGpcHelperApi.style.display, '');
+  assert.equal(api.rows.rowGpcHelperApi.style.display, 'none');
   assert.equal(api.rows.rowGpcHelperCardKey.style.display, '');
   assert.equal(api.rows.rowGpcHelperPhone.style.display, '');
   assert.match(api.plusPaymentMethodCaption.textContent, /GPC/);
diff --git a/tests/step-definitions-module.test.js b/tests/step-definitions-module.test.js
index d5ef80e..974b6c6 100644
--- a/tests/step-definitions-module.test.js
+++ b/tests/step-definitions-module.test.js
@@ -136,6 +136,8 @@ test('sidepanel html exposes Plus mode, PayPal, and GoPay settings', () => {
   assert.match(html, /<option value="gpc-helper">GPC<\/option>/);
   assert.match(html, /id="btn-gpc-card-key-purchase"/);
   assert.match(html, />购买卡密</);
+  assert.doesNotMatch(html, /GPC API/);
+  assert.doesNotMatch(html, /id="input-gpc-helper-api"/);
   assert.match(html, /id="input-gpc-helper-card-key"/);
   assert.match(html, /id="btn-gpc-helper-balance"/);
   assert.match(html, /id="input-gpc-helper-phone"/);