Silverback x402 Facilitator

Zero-fee x402 payment facilitator supporting USDC settlement on Base, SKALE, and Solana.

Live: https://facilitator.silverbackdefi.app

Overview

Silverback Facilitator is built on the official @x402/core + @x402/evm + @x402/svm SDK. It provides free payment settlement for any x402 resource server — no API keys or setup required.

Supported Networks

Network	Asset	Protocol	Gas	Address
Base	USDC	ERC-3009	~$0.001	0x48380bCf1c09773C9E96901F89A7A6B75E2BBeCC
SKALE Base Hub	USDC (Bridged)	ERC-3009	$0.00	0x48380bCf1c09773C9E96901F89A7A6B75E2BBeCC
Solana	USDC	SPL Transfer	~$0.001	CiFihYLDLZYE92R5FtyHt1YaWiVpv6FJUg1wBjQGEAMQ

Endpoints

Method	Path	Description
GET	/supported	Returns supported kinds, extensions, and signers
POST	/verify	Verify a payment signature
POST	/settle	Execute on-chain settlement
GET	/discovery/resources	Bazaar-compatible resource catalog
GET	/health	Operational status

Usage

Use Silverback as your facilitator in any x402 resource server:

import { paymentMiddleware } from "x402/express";

app.use(
  paymentMiddleware(
    receiverAddress,
    resourceConfig,
    { url: "https://facilitator.silverbackdefi.app" }
  )
);

Or with the facilitators package:

import { silverback } from "facilitators";
import { paymentMiddleware } from "x402/express";

app.use(paymentMiddleware(receiverAddress, resourceConfig, silverback));

Features

• Zero fee — No settlement fee on any network
• Multi-chain — Base, SKALE, and Solana in one facilitator
• Zero gas — SKALE settlements cost nothing in gas
• ERC-3009 — TransferWithAuthorization for Base and SKALE USDC
• SPL Transfer — Native Solana USDC settlement
• EIP-6492 — Smart wallet deployment support
• Bazaar Discovery — Resources cataloged on successful settlement
• v1 + v2 — Supports both x402 payload formats

Tech Stack

• @x402/core — Facilitator framework
• @x402/evm — EVM scheme (Base + SKALE)
• @x402/svm — Solana scheme
• @x402/extensions — Bazaar discovery catalog
• Express.js + esbuild

Environment Variables

Variable	Required	Description
FACILITATOR_PRIVATE_KEY	Yes	EVM signing key (Base + SKALE)
SOLANA_FACILITATOR_PRIVATE_KEY	No	SVM signing key (Solana)
BASE_RPC_URL	No	Custom Base RPC (default: public)
PORT	No	Server port (default: 3402)

Links

• Website: https://silverbackdefi.app
• x402scan: Silverback Facilitator
• x402 Protocol: https://github.com/coinbase/x402

License

MIT