@heraldprotocol/x402

JavaScript SDK for the heraldprotocol x402 protocol on the 0G network.

Installation

# npm
npm install @heraldprotocol/x402

# pnpm
pnpm add @heraldprotocol/x402

# yarn
yarn add @heraldprotocol/x402

# bun
bun add @heraldprotocol/x402

Modules

@heraldprotocol/x402/server

Server-side helpers for sellers to integrate x402 micropayments, preconfigured for 0G networks.

ExactEvmScheme

Drop-in replacement for @x402/evm's ExactEvmScheme. Adds a money parser that resolves human-readable prices (e.g. "$0.001") to the correct token amount for 0G's default stablecoin per network — so you can price endpoints in USD without hardcoding decimals or token addresses.

Register it on your x402ResourceServer for the 0G network you target:

import { ExactEvmScheme } from "@heraldprotocol/x402/server";

new x402ResourceServer(facilitator).register(
  "eip155:16661",
  new ExactEvmScheme()
);

That's the only heraldprotocol-specific wiring. Everything else — the facilitator client, paymentMiddleware, route definitions — is standard x402. See the x402 docs for framework adapters (Hono, Express, Next.js, etc.).

A full end-to-end Hono example lives at examples/server.

Supported networks

| Network | Chain ID | Default Asset | Symbol | Address | | -------------- | -------------------- | ----------------- | --------- | -------------------------------------------- | | eip155:16661 | 0G Mainnet | Bridged USDC | USDC.e | 0x1f3aa82227281ca364bfb3d253b0f1af1da6473e | | eip155:16602 | 0G Galileo Testnet | - | - | - |

0G testnet has no official stablecoin yet. This table will be updated once one is available.

Requirements

• Node.js 18+ (or any runtime with WebCrypto + fetch)

License

MIT