x402 Agent Payments

ARouter supports the x402 payment protocol, the open standard for HTTP-native payments. AI agents with crypto wallets can authenticate, pay for credits, and make LLM requests — all without registering an account or logging into a dashboard.

Three Entry Points

ARouter provides three ways for agents to get started. API key users and wallet users now follow separate long-term paths:

Entry Point	Auth Method	Use Case
Standard x402 Payment	`PAYMENT-SIGNATURE` header only	Any x402 client — first wallet payment registers account and returns a wallet JWT
SIWx Authentication	`SIGN-IN-WITH-X` header	Prove wallet ownership → get wallet JWT (no payment)
API Key	`Authorization: Bearer lr_live_xxxx`	Existing API key users — insufficient balance returns `403`, no x402 auto-topup

Standard x402 mode works with any x402-compatible tool — @x402/fetch, awal, MCP wallets, Chrome extensions. No ARouter SDK required.

How It Works

Standard x402 (Any x402 Client)

The simplest entry point. Any wallet with USDC can make LLM requests immediately:

Send a request with no API key — the gateway returns HTTP 402 with payment options.
The x402 client signs a USDC payment (gasless via EIP-3009).
Retry the request with the PAYMENT-SIGNATURE header.
The gateway verifies, settles, creates your account, and returns the response.
The PAYMENT-RESPONSE header contains a jwt extension for future wallet-authenticated requests.

Prove wallet ownership to get a wallet JWT without paying first: SIWx follows the CAIP-122 standard — the same protocol used by QuickNode and other x402-enabled services.

API Key Users

Existing API key users continue to use the standard ARouter API key flow:

Supported Networks

Network	CAIP-2 Identifier	Token
Base Mainnet	`eip155:8453`	USDC
Base Sepolia (testnet)	`eip155:84532`	USDC
Solana Mainnet	`solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp`	USDC
Solana Devnet	`solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1`	USDC

Wallet Compatibility

All wallets work — no private key export required:

Wallet	Payment (EIP-3009)	Auth (SIWx)	Needs Private Key?
MetaMask	✓	✓	No
Coinbase Wallet	✓	✓	No
Coinbase Agent Wallet	✓	✓	No (CDP API)
Phantom (Solana)	✓	✓	No
Local private key	✓	✓	Yes

SDK Usage

Standard x402 (No ARouter SDK Needed)

Use Coinbase’s official @x402/fetch directly:

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { ExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);
const client = new x402Client();
client.register("eip155:*", new ExactEvmScheme(signer));

const paidFetch = wrapFetchWithPayment(fetch, client);

const resp = await paidFetch("https://api.arouter.ai/v1/chat/completions", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    model: "openai/gpt-5.4",
    messages: [{ role: "user", content: "Hello" }],
  }),
});

SIWx Authentication (Get Wallet JWT)

Node.js SDK

import { ARouter, authenticateWithSIWx } from "@arouter/sdk";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);

const { jwt } = await authenticateWithSIWx(
  "https://api.arouter.ai",
  { address: account.address, signMessage: (msg) => account.signMessage({ message: msg }) },
);

const client = new ARouter({ baseURL: "https://api.arouter.ai", apiKey: jwt });

Go SDK

import arouter "github.com/arouter-ai/arouter-go"

signer := arouter.NewEvmWalletSigner(privateKey)
result, err := arouter.AuthenticateWithSIWx(ctx, "https://api.arouter.ai", signer, nil)

client := arouter.NewClient("https://api.arouter.ai", result.JWT)

ARouter SDK + Auto Payment (Recommended for High-Frequency)

Go SDK — EVM (Base)

import (
    "github.com/ethereum/go-ethereum/crypto"
    arouter "github.com/arouter-ai/arouter-go"
)

key, _ := crypto.HexToECDSA("your-private-key-hex")

client := arouter.NewClient(
    "https://api.arouter.ai",
    "",  // no API key needed
    arouter.WithX402CoinbasePayment(key),
)

WithX402CoinbasePayment sets up wallet x402 payment with JWT caching:

first successful payment returns a wallet JWT inside PAYMENT-RESPONSE
subsequent requests use Bearer <jwt>
401 triggers SIWx re-authentication
402 triggers x402 payment

Go SDK — Solana

solanaKey := ed25519.PrivateKey(yourKeyBytes)
client := arouter.NewClient("https://api.arouter.ai", "",
    arouter.WithX402SolanaPayment(solanaKey),
)

Node.js SDK — EVM (Base)

import { ARouter, withX402EvmPayment } from "@arouter/sdk";
import { privateKeyToAccount } from "viem/accounts";

const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);
const client = withX402EvmPayment(
  new ARouter({ baseURL: "https://api.arouter.ai", apiKey: "" }),
  signer,
);

Node.js SDK — Dual-Chain (EVM + Solana)

import { ARouter, withX402Payment } from "@arouter/sdk";

const client = withX402Payment(
  new ARouter({ baseURL: "https://api.arouter.ai", apiKey: "" }),
  {
    evm: { signer: evmAccount },
    solana: { signer: solanaSigner },
  },
);

GET Endpoint for CLI Tools

For x402 CLI tools like awal that cannot send POST bodies:

GET /v1/x402/chat?model=openai/gpt-5.4&message=Hello&system=Be+brief&max_tokens=100

Parameter	Required	Description
`model`	Yes	Model name, e.g. `openai/gpt-5.4`
`message`	Yes	User message text
`system`	No	System prompt
`max_tokens`	No	Maximum output tokens
`temperature`	No	Temperature parameter
`stream`	No	Set to `true` for streaming

Payment Headers

Header	Direction	Description
`PAYMENT-REQUIRED`	Server → Client	Base64-encoded payment options (amount, wallet, network).
`PAYMENT-SIGNATURE`	Client → Server	Base64-encoded signed payment payload.
`SIGN-IN-WITH-X`	Client → Server	Base64-encoded SIWx authentication proof.
`PAYMENT-RESPONSE`	Server → Client	Base64-encoded settlement result. ARouter adds a `jwt` field for wallet users.

How Credits Work

x402 payments are deposited as credits into your tenant balance — the same pool used by Stripe and Helio payments.
All x402 transactions appear in the Billing page under transaction history with the x402_topup reference type.
The gateway deducts credits per-request as usual after the balance is topped up.
Wallet users are billed by tenant, authenticated by wallet JWT, and can re-authenticate via SIWx without exposing raw API keys.

Security

Standard x402 protocol: Uses Coinbase’s official x402 SDK for verification and settlement.
Facilitator verification: Payments are cryptographically verified via the x402 Facilitator before credits are granted.
Gasless payments: EIP-3009 (TransferWithAuthorization) — users sign, the Facilitator submits on-chain.
Amount cap: Single payments are capped to prevent unexpectedly large charges.
Idempotency: Each payment payload has a unique nonce — the same signature cannot be replayed.
SIWx standard: Authentication follows CAIP-122 with EIP-4361 (EVM) and SIWS (Solana) message formats.
Audit trail: All x402 top-ups are recorded in transaction history alongside Stripe/Helio payments.
Non-custodial: USDC goes directly to the receiving wallet. The Facilitator never holds funds.

Get Started

Core Concepts

Routing

Features

Guides

Privacy

Administration

Best Practices

Frameworks & Integrations

For Providers

Support

x402 Agent Payments

Three Entry Points

How It Works

Standard x402 (Any x402 Client)

API Key Users

Supported Networks

Wallet Compatibility

SDK Usage

Standard x402 (No ARouter SDK Needed)

SIWx Authentication (Get Wallet JWT)

Node.js SDK

Go SDK

ARouter SDK + Auto Payment (Recommended for High-Frequency)

Go SDK — EVM (Base)

Go SDK — Solana

Node.js SDK — EVM (Base)

Node.js SDK — Dual-Chain (EVM + Solana)

GET Endpoint for CLI Tools

Payment Headers

How Credits Work

Security

​Three Entry Points

​How It Works

​Standard x402 (Any x402 Client)

​SIWx Authentication (Wallet Sign-In)

​API Key Users

​Supported Networks

​Wallet Compatibility

​SDK Usage

​Standard x402 (No ARouter SDK Needed)

​SIWx Authentication (Get Wallet JWT)

​Node.js SDK

​Go SDK

​ARouter SDK + Auto Payment (Recommended for High-Frequency)

​Go SDK — EVM (Base)

​Go SDK — Solana

​Node.js SDK — EVM (Base)

​Node.js SDK — Dual-Chain (EVM + Solana)

​GET Endpoint for CLI Tools

​Payment Headers

​How Credits Work

​Security

Three Entry Points

How It Works

Standard x402 (Any x402 Client)

SIWx Authentication (Wallet Sign-In)

API Key Users

Supported Networks

Wallet Compatibility

SDK Usage

Standard x402 (No ARouter SDK Needed)

SIWx Authentication (Get Wallet JWT)

Node.js SDK

Go SDK

ARouter SDK + Auto Payment (Recommended for High-Frequency)

Go SDK — EVM (Base)

Go SDK — Solana

Node.js SDK — EVM (Base)

Node.js SDK — Dual-Chain (EVM + Solana)

GET Endpoint for CLI Tools

Payment Headers

How Credits Work

Security