# Installation

> Install the @nerochain/x402-* packages.

The NERO 402 SDK is published as five packages under the `@nerochain/` scope. Each package is independently installable; you only pull in what you use.

## Choose the packages you need

| Package | When to install it |
|---|---|
| `@nerochain/x402-types` | Always (transitively included by the others; install directly only if you build your own client/server adapter). |
| `@nerochain/x402-server` | You are a merchant gating an HTTP endpoint behind payment. |
| `@nerochain/x402-client` | You are an agent making paid calls. |
| `@nerochain/x402-aa` | You sign payments from an ERC-4337 smart contract wallet (the `aa-native` scheme). |
| `@nerochain/x402-extensions` | You want client-side idempotency or signed access tokens for cached access after a paid call. |

## Agent-side install

```bash
pnpm add @nerochain/x402-client @nerochain/x402-aa ethers
```

## Merchant-side install (Express)

```bash
pnpm add @nerochain/x402-server
```

Adapters for Hono, Fastify, and Next.js App Router are subpath imports of the same package — no separate install.

## Requirements

- **Node 20+** for the runtime.
- **TypeScript 5+** if you are using TypeScript directly. The packages ship `.d.ts` types.
- **`ethers` v6** for the agent side (the SDK accepts an `ethers.Wallet` or `ethers.HDNodeWallet`).

## Verifying the install

After installing, type-check that the packages resolve:

```bash
node -e "console.log(require('@nerochain/x402-client').x402Fetch.toString().slice(0, 60))"
```

You should see the start of the `x402Fetch` factory function. From there, head to the [agent quickstart](/docs/getting-started/agents) or the [merchant quickstart](/docs/getting-started/merchants).