feat(cli): implement /upgrade command (#21511)

packages/cli/src/ui/commands/upgradeCommand.ts

@@ -0,0 +1,50 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {
+  AuthType,
+  openBrowserSecurely,
+  UPGRADE_URL_PAGE,
+} from '@google/gemini-cli-core';
+import type { SlashCommand } from './types.js';
+import { CommandKind } from './types.js';
+
+/**
+ * Command to open the upgrade page for Gemini Code Assist.
+ * Only intended to be shown/available when the user is logged in with Google.
+ */
+export const upgradeCommand: SlashCommand = {
+  name: 'upgrade',
+  kind: CommandKind.BUILT_IN,
+  description: 'Upgrade your Gemini Code Assist tier for higher limits',
+  autoExecute: true,
+  action: async (context) => {
+    const authType =
+      context.services.config?.getContentGeneratorConfig()?.authType;
+    if (authType !== AuthType.LOGIN_WITH_GOOGLE) {
+      // This command should ideally be hidden if not logged in with Google,
+      // but we add a safety check here just in case.
+      return {
+        type: 'message',
+        messageType: 'error',
+        content:
+          'The /upgrade command is only available when logged in with Google.',
+      };
+    }
+
+    try {
+      await openBrowserSecurely(UPGRADE_URL_PAGE);
+    } catch (error) {
+      return {
+        type: 'message',
+        messageType: 'error',
+        content: `Failed to open upgrade page: ${error instanceof Error ? error.message : String(error)}`,
+      };
+    }
+
+    return undefined;
+  },
+};