diff --git a/netlify/functions/giffgaff-token-exchange.js b/netlify/functions/giffgaff-token-exchange.js
index 9f1519b..dfe5f2f 100644
--- a/netlify/functions/giffgaff-token-exchange.js
+++ b/netlify/functions/giffgaff-token-exchange.js
@@ -7,9 +7,8 @@
 const axios = require('axios');
 
 exports.handler = async (event) => {
-  const allowedOrigin = 'https://esim.cosr.eu.org';
   const headers = {
-    'Access-Control-Allow-Origin': allowedOrigin,
+    'Access-Control-Allow-Origin': '*',
     'Access-Control-Allow-Headers': 'Content-Type, Authorization',
     'Access-Control-Allow-Methods': 'POST, OPTIONS',
     'Content-Type': 'application/json'
@@ -19,11 +18,6 @@ exports.handler = async (event) => {
     return { statusCode: 200, headers, body: '' };
   }
 
-  const reqOrigin = (event.headers && (event.headers.origin || event.headers.Origin)) || '';
-  if (reqOrigin && reqOrigin !== allowedOrigin) {
-    return { statusCode: 403, headers, body: JSON.stringify({ error: 'Forbidden', message: 'Origin not allowed' }) };
-  }
-
   if (event.httpMethod !== 'POST') {
     return {
       statusCode: 405,
@@ -88,6 +82,4 @@ exports.handler = async (event) => {
       body: JSON.stringify({ error: 'Token Exchange Failed', details: data })
     };
   }
-};
-
-
+};
\ No newline at end of file
diff --git a/server.js b/server.js
index 91ef9c0..227361b 100644
--- a/server.js
+++ b/server.js
@@ -39,6 +39,7 @@ app.use(express.static('.'));
 const giffgaffMfaChallenge = require('./netlify/functions/giffgaff-mfa-challenge');
 const giffgaffMfaValidation = require('./netlify/functions/giffgaff-mfa-validation');
 const giffgaffGraphql = require('./netlify/functions/giffgaff-graphql');
+const giffgaffTokenExchange = require('./netlify/functions/giffgaff-token-exchange');
 const verifyCookie = require('./netlify/functions/verify-cookie');
 
 // 包装Netlify Functions为Express路由
@@ -83,6 +84,7 @@ function wrapNetlifyFunction(handler) {
 app.use('/.netlify/functions/giffgaff-mfa-challenge', wrapNetlifyFunction(giffgaffMfaChallenge));
 app.use('/.netlify/functions/giffgaff-mfa-validation', wrapNetlifyFunction(giffgaffMfaValidation));
 app.use('/.netlify/functions/giffgaff-graphql', wrapNetlifyFunction(giffgaffGraphql));
+app.use('/.netlify/functions/giffgaff-token-exchange', wrapNetlifyFunction(giffgaffTokenExchange));
 app.use('/.netlify/functions/verify-cookie', wrapNetlifyFunction(verifyCookie));
 
 // Simyo API代理路由
diff --git a/src/giffgaff/giffgaff_complete_esim.html b/src/giffgaff/giffgaff_complete_esim.html
index 5184ef7..8127aa9 100644
--- a/src/giffgaff/giffgaff_complete_esim.html
+++ b/src/giffgaff/giffgaff_complete_esim.html
@@ -1243,10 +1243,12 @@
         const oauthConfig = {
             clientId: "4a05bf219b3985647d9b9a3ba610a9ce",
             redirectUri: "giffgaff://auth/callback/",
-            authUrl: "https://id.giffgaff.com/auth/oauth/authorize",
+            authUrl: "https://id.giffgaff.com/oauth/authorize",
             // 前端不再保存/使用 clientSecret；令牌交换改由后端函数完成
             tokenUrl: "/.netlify/functions/giffgaff-token-exchange",
-            scope: "read"
+            scope: "read",
+            // 可选：显式要求后端使用 Basic（仅在你使用机密客户端时打开）
+            // useBasic: true
         };
 
         // Giffgaff API端点
@@ -1885,6 +1887,13 @@
                 appState.codeVerifier = generateCodeVerifier();
                 const codeChallenge = await generateCodeChallenge(appState.codeVerifier);
                 const state = generateState();
+                // 临时持久化（使用 state->verifier 映射，避免多次点击导致覆盖）
+                try {
+                    const pkceMap = JSON.parse(sessionStorage.getItem('gg_pkce_map') || '{}');
+                    pkceMap[state] = appState.codeVerifier;
+                    sessionStorage.setItem('gg_pkce_map', JSON.stringify(pkceMap));
+                    sessionStorage.setItem('gg_oauth_last_state', state);
+                } catch (e) {}
                 
                 // 构建授权URL
                 const authParams = new URLSearchParams({
@@ -1953,6 +1962,22 @@
                 console.log('解析到的授权码:', code);
                 console.log('解析到的状态:', state);
                 
+                // 如果内存中的 codeVerifier 丢失，优先通过 state 在映射中恢复
+                if (!appState.codeVerifier) {
+                    try {
+                        const pkceMap = JSON.parse(sessionStorage.getItem('gg_pkce_map') || '{}');
+                        const byState = state && pkceMap[state];
+                        if (byState && byState.length >= 43) appState.codeVerifier = byState;
+                        if (!appState.codeVerifier) {
+                            const savedVerifier = sessionStorage.getItem('gg_code_verifier');
+                            if (savedVerifier && savedVerifier.length >= 43) appState.codeVerifier = savedVerifier;
+                        }
+                    } catch (e) {}
+                }
+                if (!appState.codeVerifier) {
+                    throw new Error('会话已重置或过期：缺少 code_verifier，请重新点击“开始OAuth登录”');
+                }
+
                 // 交换访问令牌
                 const tokenResponse = await fetch(oauthConfig.tokenUrl, {
                     method: 'POST',
@@ -1960,7 +1985,9 @@
                     body: JSON.stringify({
                         code: code,
                         code_verifier: appState.codeVerifier,
-                        redirect_uri: oauthConfig.redirectUri
+                        redirect_uri: oauthConfig.redirectUri,
+                        client_id: oauthConfig.clientId,
+                        ...(typeof oauthConfig.useBasic !== 'undefined' ? { use_basic: oauthConfig.useBasic } : {})
                     })
                 });
                 
@@ -1970,6 +1997,11 @@
                 
                 const tokenData = await tokenResponse.json();
                 appState.accessToken = tokenData.access_token;
+                try {
+                    const pkceMap = JSON.parse(sessionStorage.getItem('gg_pkce_map') || '{}');
+                    if (state && pkceMap[state]) { delete pkceMap[state]; }
+                    sessionStorage.setItem('gg_pkce_map', JSON.stringify(pkceMap));
+                } catch (e) {}
                 
                 showStatus(elements.callbackStatus, "OAuth登录成功！", "success");
                 updateStatus(); // 更新状态显示
diff --git a/tests/giffgaff/oauth.test.js b/tests/giffgaff/oauth.test.js
index 884a4a5..4a26c92 100644
--- a/tests/giffgaff/oauth.test.js
+++ b/tests/giffgaff/oauth.test.js
@@ -61,7 +61,7 @@ describe('Giffgaff OAuthManager', () => {
       const verifier = 'test-verifier';
       const url = await OAuthManager.buildAuthorizationUrl(verifier);
       
-      expect(url).toContain('https://id.giffgaff.com/auth/oauth/authorize');
+      expect(url).toContain('https://id.giffgaff.com/oauth/authorize');
       expect(url).toContain('response_type=code');
       expect(url).toContain('client_id=');
       expect(url).toContain('redirect_uri=');