@regista11/x402-facilitator

Gasless USDT0 settlement facilitator for X Layer (chain 196).

Lets your dApp accept stake / payment in USDT0 without forcing the user to hold gas. The user signs one EIP-712 typed-data payload (EIP-3009 transferWithAuthorization); your relayer wallet broadcasts the transfer and pays OKB. One signature, zero gas for the user.

Originally extracted from Regista 11 — the live football outcome market on X Layer. Works for any X Layer protocol that wants to ship gasless USDT0 payments.

What it does

1. Accepts an EIP-3009 typed-data signature from the staker.
2. Verifies the signer matches the from field, the nonce is unused, and the authorization window is open.
3. Calls USDT0.transferWithAuthorization(from, to, value, validAfter, validBefore, nonce, v, r, s) from your relayer wallet.
4. Returns the resulting on-chain tx hash.

The USDT0 contract is at 0x779Ded0c9e1022225f8E0630b35a9b54bE713736. Its EIP-712 domain name is USD₮0 — note the U+20AE TUGRIK glyph; the package matches this byte-for-byte and will reject signatures built against the ASCII T form.

Install

pnpm add @regista11/x402-facilitator
# or
npm install @regista11/x402-facilitator

viem >= 2.30 is a peer dependency.

Quickstart

import {
  XLayerFacilitatorClient,
  USDT0_ADDRESS,
} from "@regista11/x402-facilitator";

// The facilitator owns the OKB-funded relayer key and builds its own
// viem clients internally from rpcUrl + facilitatorPrivateKey.
const facilitator = new XLayerFacilitatorClient({
  rpcUrl: "https://rpc.xlayer.tech",
  facilitatorPrivateKey: process.env.RELAYER_PRIVATE_KEY as `0x${string}`,
});

// x402 "exact" scheme verbs. The user signs the EIP-712 payload in their
// wallet (match `domain.name` exactly: "USD₮0" with U+20AE). The signed
// authorization rides inside payload.payload; requirements is the x402
// payment requirement.
const payload = {
  payload: {
    authorization: {
      from: "0x…",
      to: "0x…",
      value: "5000000",          // 6-decimal USDT0 micros → $5.00
      validAfter: "0",
      validBefore: String(Math.floor(Date.now() / 1000) + 300),
      nonce: "0x…",              // 32 bytes
    },
    signature: "0x…",           // 65 bytes — v, r, s concatenated
  },
};
const requirements = { payTo: "0x…", amount: "5000000", asset: USDT0_ADDRESS };

const verdict = await facilitator.verify(payload, requirements);
if (verdict.isValid) {
  const result = await facilitator.settle(payload, requirements);
  console.log("tx hash:", result.transaction); // { success, status, transaction, network, amount, ... }
}

EIP-712 typed-data the user signs

{
  "types": {
    "EIP712Domain": [
      { "name": "name",              "type": "string"  },
      { "name": "version",           "type": "string"  },
      { "name": "chainId",           "type": "uint256" },
      { "name": "verifyingContract", "type": "address" }
    ],
    "TransferWithAuthorization": [
      { "name": "from",        "type": "address" },
      { "name": "to",          "type": "address" },
      { "name": "value",       "type": "uint256" },
      { "name": "validAfter",  "type": "uint256" },
      { "name": "validBefore", "type": "uint256" },
      { "name": "nonce",       "type": "bytes32" }
    ]
  },
  "domain": {
    "name":              "USD₮0",
    "version":           "1",
    "chainId":           196,
    "verifyingContract": "0x779Ded0c9e1022225f8E0630b35a9b54bE713736"
  },
  "primaryType": "TransferWithAuthorization",
  "message": { "...": "..." }
}

The constant USDT0_DOMAIN_NAME is exported so you don't have to hand-type the TUGRIK glyph.

Exports

| Name | Kind | What | |---|---|---| | XLayerFacilitatorClient | class | The main client — x402 verbs verify(), settle(), plus getSupported(), getSettleStatus() | | XLayerFacilitatorConfig | type | Constructor config (rpcUrl?, facilitatorPrivateKey) | | TransferAuthorization | type | EIP-3009 authorization struct | | computeDomainSeparator() | function | Computes the USDT0 domain separator | | recoverTransferSigner() | function | Recovers the signer address from an EIP-3009 signature | | splitSignature() | function | Splits a 65-byte hex signature into { v, r, s } | | SettlementCache | class | In-memory nonce cache (replay guard) | | USDT0_ADDRESS, USDT0_CHAIN_ID, USDT0_DOMAIN_NAME, USDT0_DECIMALS, … | const | USDT0 constants | | USDT0_ABI | const | Minimal ABI for transferWithAuthorization + balance reads | | TRANSFER_WITH_AUTHORIZATION_TYPES | const | EIP-712 types object — drop straight into signTypedData |

Production notes

• The relayer wallet needs OKB for gas — every relay is a real transaction on chain 196.
• Run one relayer instance per chain to keep the EVM nonce queue serialized. Multi-instance behind a load balancer will collide.
• The in-memory SettlementCache covers replay-within-window. For horizontal scale, back it with Redis / KV.

See it live

The reference deployment is the staking flow at regista11.xyz — every market is a Uniswap v4 hook on X Layer, every stake is a gasless USDT0 transfer relayed through this facilitator. Docs at regista11.xyz/docs/gasless-staking.

License

MIT © 2026 Regista 11