diff --git a/frontend/src/i18n/locales/en.ts b/frontend/src/i18n/locales/en.ts
index 031923a1..c45b99ff 100644
--- a/frontend/src/i18n/locales/en.ts
+++ b/frontend/src/i18n/locales/en.ts
@@ -923,40 +923,55 @@ export default {
             'You can copy the entire URL or just the code parameter value, the system will auto-detect'
         },
         // Gemini specific
-        gemini: {
-          title: 'Gemini Account Authorization',
-          followSteps: 'Follow these steps to authorize your Gemini account:',
-          step1GenerateUrl: 'Generate the authorization URL (requires a redirect URI)',
-          generateAuthUrl: 'Generate Auth URL',
-          step2OpenUrl: 'Open the URL in your browser and complete authorization',
-          openUrlDesc:
-            'Open the authorization URL in a new tab, log in to your Google account and authorize.',
-          step3EnterCode: 'Enter Authorization URL or Code',
-          authCodeDesc:
-            'After authorization, you will be redirected to the redirect URI with <code>code</code> and <code>state</code>. Paste the full URL or just the code below:',
-          authCode: 'Authorization URL or Code',
-          authCodePlaceholder:
-            'Option 1: Paste the complete callback URL\n(https://your-domain/auth/callback?code=...&state=...)\nOption 2: Paste only the code value',
-          authCodeHint:
-            'If you paste the full URL, the system will auto-extract code/state for you',
+	        gemini: {
+	          title: 'Gemini Account Authorization',
+	          followSteps: 'Follow these steps to authorize your Gemini account:',
+	          step1GenerateUrl: 'Generate the authorization URL',
+	          generateAuthUrl: 'Generate Auth URL',
+	          projectIdLabel: 'Project ID (optional)',
+	          projectIdPlaceholder: 'e.g. my-gcp-project or cloud-ai-companion-xxxxx',
+	          projectIdHint:
+	            'Leave empty to auto-detect after code exchange. If auto-detection fails, fill it in and re-generate the auth URL to try again.',
+	          howToGetProjectId: 'How to get',
+	          step2OpenUrl: 'Open the URL in your browser and complete authorization',
+	          openUrlDesc:
+	            'Open the authorization URL in a new tab, log in to your Google account and authorize.',
+	          step3EnterCode: 'Enter Authorization URL or Code',
+	          authCodeDesc:
+	            'After authorization, copy the callback URL (recommended) or just the <code>code</code> and paste it below.',
+	          authCode: 'Callback URL or Code',
+	          authCodePlaceholder:
+	            'Option 1 (recommended): Paste the callback URL\nOption 2: Paste only the code value',
+	          authCodeHint: 'The system will auto-extract code/state from the URL.',
           redirectUri: 'Redirect URI',
           redirectUriHint:
             'This must be configured in your Google OAuth client and must match exactly.',
           confirmRedirectUri:
             'I have configured this Redirect URI in the Google OAuth client (must match exactly)',
-          invalidRedirectUri: 'Redirect URI must be a valid http(s) URL',
-          redirectUriNotConfirmed: 'Please confirm the Redirect URI is configured correctly',
-          missingRedirectUri: 'Missing redirect URI',
-          failedToGenerateUrl: 'Failed to generate Gemini auth URL',
-          missingExchangeParams: 'Missing auth code, session ID, state, or redirect URI',
-          failedToExchangeCode: 'Failed to exchange Gemini auth code',
-          modelPassthrough: 'Gemini Model Passthrough',
-          modelPassthroughDesc:
-            'All model requests are forwarded directly to the Gemini API without model restrictions or mappings.',
-          stateWarningTitle: '⚠️ Important: Gemini requires both code and state',
-          stateWarningDesc:
-            'We recommend pasting the complete callback URL so the system can auto-extract both code and state. Pasting only the code will cause authorization to fail.'
-        }
+	          invalidRedirectUri: 'Redirect URI must be a valid http(s) URL',
+	          redirectUriNotConfirmed: 'Please confirm the Redirect URI is configured correctly',
+	          missingRedirectUri: 'Missing redirect URI',
+	          failedToGenerateUrl: 'Failed to generate Gemini auth URL',
+	          missingExchangeParams: 'Missing auth code, session ID, or state',
+	          failedToExchangeCode: 'Failed to exchange Gemini auth code',
+	          modelPassthrough: 'Gemini Model Passthrough',
+	          modelPassthroughDesc:
+	            'All model requests are forwarded directly to the Gemini API without model restrictions or mappings.',
+	          stateWarningTitle: 'Note',
+	          stateWarningDesc: 'Recommended: paste the full callback URL (includes code & state).',
+	          oauthTypeLabel: 'OAuth Type',
+	          needsProjectId: 'For GCP Developers',
+	          needsProjectIdDesc: 'Uses built-in client, requires GCP project',
+	          noProjectIdNeeded: 'For Regular Users',
+	          noProjectIdNeededDesc: 'Requires your own OAuth client'
+	        }
+	      },
+      // Gemini specific (platform-wide)
+      gemini: {
+        modelPassthrough: 'Gemini Model Passthrough',
+        modelPassthroughDesc:
+          'All model requests are forwarded directly to the Gemini API without model restrictions or mappings.',
+        apiKeyHint: 'Your Gemini API Key (starts with AIza)'
       },
       // Re-Auth Modal
       reAuthorizeAccount: 'Re-Authorize Account',
@@ -983,7 +998,7 @@ export default {
       startingTestForAccount: 'Starting test for account: {name}',
       testAccountTypeLabel: 'Account type: {type}',
       selectTestModel: 'Select Test Model',
-      testModel: 'claude-sonnet-4-5-20250929',
+      testModel: 'Test model',
       testPrompt: 'Prompt: "hi"',
       // Stats Modal
       viewStats: 'View Stats',
diff --git a/frontend/src/i18n/locales/zh.ts b/frontend/src/i18n/locales/zh.ts
index b309e8a6..5ffe0d94 100644
--- a/frontend/src/i18n/locales/zh.ts
+++ b/frontend/src/i18n/locales/zh.ts
@@ -1038,35 +1038,47 @@ export default {
           authCodeHint: '您可以直接复制整个链接或仅复制 code 参数值，系统会自动识别'
         },
         // Gemini specific
-        gemini: {
-          title: 'Gemini 账户授权',
-          followSteps: '请按照以下步骤完成 Gemini 账户的授权：',
-          step1GenerateUrl: '先配置 Redirect URI，然后生成授权链接',
-          generateAuthUrl: '生成授权链接',
-          step2OpenUrl: '在浏览器中打开链接并完成授权',
-          openUrlDesc: '请在新标签页中打开授权链接，登录您的 Google 账户并授权。',
-          step3EnterCode: '输入回调链接或 Code',
-          authCodeDesc:
-            '授权完成后会跳转到 Redirect URI，并带上 <code>code</code> 与 <code>state</code> 参数。请粘贴完整链接或仅粘贴 code：',
-          authCode: '回调链接或 Code',
-          authCodePlaceholder:
-            '方式1：粘贴完整回调链接\n(https://your-domain/auth/callback?code=...&state=...)\n方式2：仅粘贴 code 参数的值',
-          authCodeHint: '如果粘贴完整链接，系统会自动提取 code/state',
+	        gemini: {
+	          title: 'Gemini 账户授权',
+	          followSteps: '请按照以下步骤完成 Gemini 账户的授权：',
+	          step1GenerateUrl: '生成授权链接',
+	          generateAuthUrl: '生成授权链接',
+	          projectIdLabel: 'Project ID（可选）',
+	          projectIdPlaceholder: '例如：my-gcp-project 或 cloud-ai-companion-xxxxx',
+	          projectIdHint: '留空则在兑换授权码后自动探测；若自动探测失败，可填写后重新生成授权链接再授权。',
+	          howToGetProjectId: '如何获取',
+	          step2OpenUrl: '在浏览器中打开链接并完成授权',
+	          openUrlDesc: '请在新标签页中打开授权链接，登录您的 Google 账户并授权。',
+	          step3EnterCode: '输入回调链接或 Code',
+	          authCodeDesc: '授权完成后，复制浏览器跳转后的回调链接（推荐）或仅复制 <code>code</code>，粘贴到下方即可。',
+	          authCode: '回调链接或 Code',
+	          authCodePlaceholder: '方式1（推荐）：粘贴回调链接\n方式2：仅粘贴 code 参数的值',
+	          authCodeHint: '系统会自动从链接中解析 code/state。',
           redirectUri: 'Redirect URI',
           redirectUriHint: '需要在 Google OAuth Client 中配置，且必须与此处完全一致。',
           confirmRedirectUri: '我已在 Google OAuth Client 中配置了该 Redirect URI（必须完全一致）',
           invalidRedirectUri: 'Redirect URI 必须是合法的 http(s) URL',
-          redirectUriNotConfirmed: '请确认 Redirect URI 已在 Google OAuth Client 中正确配置',
-          missingRedirectUri: '缺少 Redirect URI',
-          failedToGenerateUrl: '生成 Gemini 授权链接失败',
-          missingExchangeParams: '缺少 code / session_id / state / redirect_uri',
-          failedToExchangeCode: 'Gemini 授权码兑换失败',
-          modelPassthrough: 'Gemini 直接转发模型',
-          modelPassthroughDesc: '所有模型请求将直接转发至 Gemini API，不进行模型限制或映射。',
-          stateWarningTitle: '⚠️ 重要：Gemini 需要 code 和 state 参数',
-          stateWarningDesc:
-            '建议直接粘贴完整的回调链接，系统会自动提取 code 和 state。如果只粘贴 code，授权将会失败。'
-        }
+	          redirectUriNotConfirmed: '请确认 Redirect URI 已在 Google OAuth Client 中正确配置',
+	          missingRedirectUri: '缺少 Redirect URI',
+	          failedToGenerateUrl: '生成 Gemini 授权链接失败',
+	          missingExchangeParams: '缺少 code / session_id / state',
+	          failedToExchangeCode: 'Gemini 授权码兑换失败',
+	          modelPassthrough: 'Gemini 直接转发模型',
+	          modelPassthroughDesc: '所有模型请求将直接转发至 Gemini API，不进行模型限制或映射。',
+	          stateWarningTitle: '提示',
+	          stateWarningDesc: '建议粘贴完整回调链接（包含 code 和 state）。',
+	          oauthTypeLabel: 'OAuth 类型',
+	          needsProjectId: '适合 GCP 开发者',
+	          needsProjectIdDesc: '使用内置客户端，需 GCP 项目',
+	          noProjectIdNeeded: '适合普通用户',
+	          noProjectIdNeededDesc: '需自建 OAuth Client'
+	        }
+	      },
+      // Gemini specific (platform-wide)
+      gemini: {
+        modelPassthrough: 'Gemini 直接转发模型',
+        modelPassthroughDesc: '所有模型请求将直接转发至 Gemini API，不进行模型限制或映射。',
+        apiKeyHint: 'Your Gemini API Key（以 AIza 开头）'
       },
       // Re-Auth Modal
       reAuthorizeAccount: '重新授权账号',
@@ -1090,9 +1102,9 @@ export default {
       copyOutput: '复制输出',
       startingTestForAccount: '开始测试账号：{name}',
       testAccountTypeLabel: '账号类型：{type}',
-      selectTestModel: '选择测试模型',
-      testModel: 'claude-sonnet-4-5-20250929',
-      testPrompt: '提示词："hi"',
+	      selectTestModel: '选择测试模型',
+	      testModel: '测试模型',
+	      testPrompt: '提示词："hi"',
       // Stats Modal
       viewStats: '查看统计',
       usageStatistics: '使用统计',