Add auto sub accounts demo

base-account/auto-sub-accounts/README.md

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+# Sub Accounts Example
+
+A simple Next.js app demonstrating Base Account SDK Sub Accounts integration with automatic sub account creation and USDC transfers on Base Sepolia.
+
+## Features
+
+- **Automatic Sub Account Creation**: Sub account is created automatically when users connect their wallet
+- **USDC Transfer**: Send USDC to a specified address on Base Sepolia
+- **Auto Spend Permissions**: Sub accounts can access Universal Account balance when needed
+- **Modern UI**: Clean and responsive interface
+
+## Getting Started
+
+### Prerequisites
+
+- Node.js 18+ installed
+- A Base Account (create one at [account.base.app](https://account.base.app))
+- USDC on Base Sepolia testnet
+
+### Installation
+
+1. Install dependencies:
+
+```bash
+npm install
+```
+
+2. Run the development server:
+
+```bash
+npm run dev
+```
+
+3. Open [http://localhost:3000](http://localhost:3000) in your browser
+
+## How It Works
+
+This app uses the **quickstart configuration** from the Base Account SDK:
+
+```tsx
+const sdk = createBaseAccountSDK({
+  subAccounts: {
+    creation: 'on-connect',    // Auto-create sub account on connect
+    defaultAccount: 'sub',      // Use sub account for transactions by default
+  }
+});
+```
+
+### Key Benefits
+
+- **No repeated prompts**: Transactions are sent from the sub account without repeated approval
+- **Seamless funding**: Auto Spend Permissions allow the sub account to access Universal Account balance
+- **Better UX**: Perfect for apps requiring frequent transactions
+
+## Usage
+
+1. **Connect Wallet**: Click "Connect Wallet" and approve the connection in your Base Account
+2. **Sub Account Created**: A sub account is automatically created for this app
+3. **Send USDC**: Enter an amount and click "Send USDC" to transfer to the recipient address
+
+## Configuration
+
+### Recipient Address
+
+The USDC recipient address is set in `app/page.tsx`:
+
+```tsx
+const RECIPIENT_ADDRESS = "0xd8da6bf26964af9d7eed9e03e53415d37aa96045";
+```
+
+### USDC Contract
+
+The app uses the USDC contract on Base Sepolia:
+
+```tsx
+const USDC_ADDRESS = "0x036CbD53842c5426634e7929541eC2318f3dCF7e";
+```
+
+## Learn More
+
+- [Base Account Documentation](https://docs.base.org/base-account)
+- [Sub Accounts Guide](https://docs.base.org/base-account/improve-ux/sub-accounts)
+- [Base Account SDK](https://github.com/base/account-sdk)
+
+## License
+
+MIT
+

base-account/auto-sub-accounts/app/globals.css

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+* {
+  box-sizing: border-box;
+  padding: 0;
+  margin: 0;
+}
+
+html,
+body {
+  max-width: 100vw;
+  overflow-x: hidden;
+}
+
+body {
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
+    'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
+    sans-serif;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+  background: linear-gradient(to bottom, #0052ff 0%, #001a66 100%);
+  min-height: 100vh;
+  color: white;
+}
+
+.container {
+  max-width: 800px;
+  margin: 0 auto;
+  padding: 40px 20px;
+}
+
+.card {
+  background: rgba(255, 255, 255, 0.1);
+  backdrop-filter: blur(10px);
+  border-radius: 16px;
+  padding: 32px;
+  margin-bottom: 24px;
+  border: 1px solid rgba(255, 255, 255, 0.2);
+}
+
+.title {
+  font-size: 2.5rem;
+  font-weight: bold;
+  margin-bottom: 8px;
+  text-align: center;
+}
+
+.subtitle {
+  font-size: 1.1rem;
+  opacity: 0.9;
+  text-align: center;
+  margin-bottom: 32px;
+}
+
+.section-title {
+  font-size: 1.5rem;
+  font-weight: 600;
+  margin-bottom: 16px;
+}
+
+.info-row {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  margin-bottom: 16px;
+  padding: 16px;
+  background: rgba(0, 0, 0, 0.2);
+  border-radius: 8px;
+}
+
+.info-label {
+  font-size: 0.875rem;
+  opacity: 0.8;
+  font-weight: 500;
+}
+
+.info-value {
+  font-family: 'Monaco', 'Courier New', monospace;
+  font-size: 0.9rem;
+  word-break: break-all;
+}
+
+.button {
+  background: white;
+  color: #0052ff;
+  border: none;
+  padding: 14px 28px;
+  border-radius: 8px;
+  font-size: 16px;
+  font-weight: 600;
+  cursor: pointer;
+  transition: all 0.2s;
+  width: 100%;
+  margin-bottom: 12px;
+}
+
+.button:hover:not(:disabled) {
+  transform: translateY(-2px);
+  box-shadow: 0 4px 12px rgba(255, 255, 255, 0.3);
+}
+
+.button:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.button-secondary {
+  background: transparent;
+  color: white;
+  border: 2px solid white;
+}
+
+.button-secondary:hover:not(:disabled) {
+  background: rgba(255, 255, 255, 0.1);
+}
+
+.status-message {
+  padding: 12px 16px;
+  background: rgba(0, 0, 0, 0.3);
+  border-radius: 8px;
+  margin-bottom: 16px;
+  font-size: 0.9rem;
+}
+
+.button-group {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+}
+
+.input-group {
+  margin-bottom: 16px;
+}
+
+.input-label {
+  display: block;
+  margin-bottom: 8px;
+  font-size: 0.9rem;
+  font-weight: 500;
+}
+
+.input {
+  width: 100%;
+  padding: 12px 16px;
+  border-radius: 8px;
+  border: 1px solid rgba(255, 255, 255, 0.3);
+  background: rgba(0, 0, 0, 0.2);
+  color: white;
+  font-size: 1rem;
+  font-family: 'Monaco', 'Courier New', monospace;
+}
+
+.input::placeholder {
+  color: rgba(255, 255, 255, 0.5);
+}
+
+.input:focus {
+  outline: none;
+  border-color: white;
+}
+

base-account/auto-sub-accounts/app/layout.tsx

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+import type { Metadata } from "next";
+import "./globals.css";
+
+export const metadata: Metadata = {
+  title: "Sub Accounts Example",
+  description: "Demo app showing Base Account Sub Accounts integration",
+};
+
+export default function RootLayout({
+  children,
+}: Readonly<{
+  children: React.ReactNode;
+}>) {
+  return (
+    <html lang="en">
+      <body>{children}</body>
+    </html>
+  );
+}
+