> ## Documentation Index
> Fetch the complete documentation index at: https://docs.renvoy.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Client Integration

> Pay for x402-protected API endpoints using USDC.

## Prerequisites

* A wallet with USDC on the target network (Base, Base Sepolia, Solana, or Solana Devnet)
* The wallet's private key (for signing payments)

## Using `@x402/fetch`

The `@x402/fetch` package wraps the standard `fetch` API to automatically handle 402 responses — detecting payment requirements, signing the USDC transfer, and retrying the request.

### Install

```bash theme={null}
npm install @x402/fetch @x402/evm viem
```

### Minimal example

```typescript theme={null}
import { x402Client, wrapFetchWithPayment } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Create a signer from your private key
const signer = privateKeyToAccount("0xYOUR_PRIVATE_KEY");

// Set up the x402 client with EVM payment support
const client = new x402Client();
registerExactEvmScheme(client, { signer });

// Wrap fetch to auto-handle 402 responses
const fetchWithPayment = wrapFetchWithPayment(fetch, client);

// Use it like normal fetch — payments are handled automatically
const response = await fetchWithPayment("https://api.example.com/data");
const data = await response.json();
```

### How it works

1. `fetchWithPayment` makes the initial request
2. If the server returns `402`, the wrapper reads the payment requirements from the response
3. It signs a USDC transfer authorization using your wallet
4. It retries the request with the signed payment in the `X-PAYMENT` header
5. The server settles the payment via the facilitator and returns the data

No manual header construction. No base64 encoding. The wrapper handles everything.

### Reading the payment response

After a successful payment, the server includes settlement details in the `PAYMENT-RESPONSE` header:

```typescript theme={null}
import { x402Client, wrapFetchWithPayment, x402HTTPClient } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const signer = privateKeyToAccount("0xYOUR_PRIVATE_KEY");
const client = new x402Client();
registerExactEvmScheme(client, { signer });
const fetchWithPayment = wrapFetchWithPayment(fetch, client);

const response = await fetchWithPayment("https://api.example.com/data");

if (response.ok) {
  const paymentResponse = new x402HTTPClient(client).getPaymentSettleResponse(
    name => response.headers.get(name),
  );
  console.log("Transaction:", paymentResponse.transaction);
}
```

## Raw integration (without `@x402/fetch`)

If you can't use the wrapper, handle the 402 flow manually:

### 1. Make the initial request

```bash theme={null}
curl -i https://api.example.com/data
```

### 2. Parse the 402 response

The response body contains payment requirements:

```json theme={null}
{
  "x402Version": 1,
  "accepts": [{
    "scheme": "exact",
    "network": "eip155:8453",
    "maxAmountRequired": "1000",
    "resource": "https://api.example.com/data",
    "description": "API access",
    "mimeType": "application/json",
    "payTo": "0xMerchantAddress",
    "maxTimeoutSeconds": 60,
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "extra": { "name": "USD Coin", "version": "2" }
  }]
}
```

### 3. Sign the payment

Construct and sign a USDC `transferWithAuthorization` (EIP-3009) or `permit` + `transferFrom` authorization matching the requirements.

### 4. Retry with the payment

Base64-encode the signed payment payload and include it in the `X-PAYMENT` header:

```bash theme={null}
curl -H "X-PAYMENT: <base64-encoded-payment>" https://api.example.com/data
```

The server will settle the payment via the facilitator and return the data.

## Solana client

For Solana, use the `@x402/svm` package instead of `@x402/evm`:

### Install

```bash theme={null}
npm install @x402/fetch @x402/svm @solana/web3.js
```

### Example

```typescript theme={null}
import { x402Client, wrapFetchWithPayment } from "@x402/fetch";
import { registerExactSvmScheme } from "@x402/svm/exact/client";
import { Keypair } from "@solana/web3.js";

// Create a signer from your private key
const signer = Keypair.fromSecretKey(Uint8Array.from(JSON.parse(process.env.SOLANA_PRIVATE_KEY!)));

// Set up the x402 client with Solana payment support
const client = new x402Client();
registerExactSvmScheme(client, { signer });

// Wrap fetch to auto-handle 402 responses
const fetchWithPayment = wrapFetchWithPayment(fetch, client);

// Use it like normal fetch — payments are handled automatically
const response = await fetchWithPayment("https://api.example.com/data");
const data = await response.json();
```