x402 machine payments on Elysium Testnet

Turn HTTP 402 into a settlement gate.

EPP-402 lets agents and services discover each other, agree a signed quote, pay over x402 with one signed header, settle on Elysium and hold a receipt that proves both the payment and the delivery.

Read the quickstart Open the explorer

Network
Elysium Testnet · chain 99801
Settles to HyperEVM
Standard
x402 v2 · exact scheme
PAYMENT-REQUIRED, -SIGNATURE, -RESPONSE
Settlement
EIP-3009 · facilitator pays gas
The payer signs, never broadcasts
Status
Testnet · awaiting first settlement
Nothing has settled yet

POST/v1/inference

402 Payment Requiredexample

PAYMENT-REQUIRED · decoded

{
  "x402Version": 2,
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:99801",
      "asset": "0x…EPPUSD",
      "amount": "10000",
      "payTo": "0xb1297Fea0b54A79BdBCfb8b057e39B226Cc2ebFc",
      "maxTimeoutSeconds": 300
    }
  ],
  "extensions": {
    "epp402": {
      "info": {
        "version": "1.0.0",
        "providerId": "inference.example.com",
        "quoteId": "qt_01k9r3w6zj8e2n0h4yv7c5b9ma"
      }
    }
  }
}

POST/v1/inference+ PAYMENT-SIGNATURE

200 OK

PAYMENT-RESPONSE · decoded

{
  "success": true,
  "transaction": "0x4b6c…e21f",
  "network": "eip155:99801",
  "payer": "0xB572b1950336e3c0b73B3E289929ceD2E4fda2b8"
}

EPP-RECEIPTSigned by the provider

The gate

Six stages carry a request from discovery to a receipt.

Discovery, quote, session and intent happen before any money moves. Settlement is the one on-chain step. The receipt is what the buyer keeps. Each stage is a protocol object with a schema, and the four signed ones carry an EIP-712 signature bound to the chain.

lifecycle one paid requestPlaying

stage 01 · Discovery

A provider publishes what it sells, the assets it accepts, the facilitators it settles through and the key its quotes and receipts are signed with. The registry indexes the document; it is never required to buy.

DiscoveryDocument fields, from the schema

protocol
version
provider
network
networks
assets
x402
services
receipts
updatedAt
signature

Live network

What has settled on Elysium Testnet.

Indexed from the chain and the facilitator, refreshed every thirty seconds. Nothing here is simulated: when the count is zero, the count is zero.

Indexer connectedOpen the explorer

Confirmed settlements

None yet

Settled volume

EPPUSD

Asset not deployed yet

Registered providers

0 have been paid

Commerce sessions

0 receipts issued

settlements latest 0

eip155:99801

Transaction	Payer	Paid to	Amount	Status	When
No settlements indexed yet. The first paid request through an EPP-402 provider will appear here.

Three layers

x402 is the payment. EPP-402 is the commerce around it. Elysium is where it settles.

EPP-402 does not replace x402; it uses the official v2 specification, packages and facilitator interface as its HTTP-native payment foundation and adds a structured commerce layer above it. A plain x402 client can pay an EPP-402 endpoint without learning a new handshake.

Read the architecture

EPP-402 commerce layer

off-chain · signed objects

Coordinates the economic interaction around a payment.

Service discovery
Provider metadata
Pricing and quotes
Commerce sessions
Payment intents
Spending policies
Transaction coordination
Receipt generation
Commerce history

x402 payment layer

HTTP · official v2 wire format

Requests, communicates, verifies and settles a payment over HTTP.

HTTP 402 negotiation
Payment requirements
Payment payloads
Payment schemes (exact)
Payment verification
Settlement interfaces
Settlement responses

Elysium settlement layer

on-chain · EVM

Moves the money and makes it verifiable.

EVM-compatible execution
Supported payment assets
Wallet signatures
Smart contracts where required
Transaction monitoring
On-chain verification

Developers

Your route stays. The gate goes in front of it.

Accepting a payment is one middleware. Paying is one wrapped fetch. The protocol handles the headers, the signatures and the settlement, and leaves you the handler.

01Publish a discovery document
Serve /.well-known/epp402.json: your services, prices, assets, facilitators and the key your quotes and receipts are signed with.
02Guard a route with payment
The middleware answers 402 with x402 v2 requirements, verifies the signed payment with the facilitator, settles on Elysium and issues a signed receipt.
03Pay from an agent
The SDK discovers, quotes, opens a session, enforces the spending policy, signs one EIP-3009 authorization and verifies the receipt. No gas, no API key.

server.tsIllustrative

import { serve } from "@hono/node-server";
import { privateKeyToAccount } from "viem/accounts";
import { createProvider } from "@epp402/server";

const provider = createProvider({
  providerId: "inference.example.com",
  name: "Example Inference",
  url: "https://inference.example.com",
  network: "elysium-testnet",
  signer: privateKeyToAccount(process.env.PROVIDER_PRIVATE_KEY as `0x${string}`),
  facilitatorUrl: "https://epp402-core.fly.dev/facilitator",
  registryUrl: "https://epp402-core.fly.dev",
  services: [
    {
      id: "inference.standard",
      name: "Standard inference",
      category: "ai-inference",
      endpoint: "/v1/inference",
      method: "POST",
      price: "0.01", // list price in EPPUSD; the quote below prices each request
      quote: {
        price: (req) => 10_000n + 5n * BigInt(String((req.params as { text?: string }).text ?? "").length / 100),
      },
    },
  ],
});

// Discovery, quotes, receipts and the x402 gate are already mounted; add your handler.
const app = provider.app();
app.post("/v1/inference", async (c) => c.json(await infer(await c.req.json())));

serve({ fetch: app.fetch, port: 4031 }, () => provider.publish());

Quickstart SDK reference

Ecosystem

One registry, eight kinds of service.

Providers publish their own discovery documents; the registry indexes them by category so an agent can find a price without a sales call. Counts are live from the index.

Browse providers

Compatibility

Built on the standard, settled on the chain.

EPP-402 does not invent an incompatible payment handshake, and it does not assume a stablecoin exists. Both halves below were verified against the official documentation and the live network.

x402 compatibility

Specification

Specification: x402 v2, the official specification and TypeScript packages
Headers: PAYMENT-REQUIRED, PAYMENT-SIGNATURE, PAYMENT-RESPONSE (never the legacy v1 headers)
Scheme: exact, EIP-3009 transferWithAuthorization: the payer signs, the facilitator broadcasts
Facilitator: GET /supported, POST /verify, POST /settle, plus GET /status/:tx
Extension: EPP-402 commerce references ride in extensions.epp402; the wire format is untouched
Interoperability: Any x402 v2 client that allows the asset can pay an EPP-402 endpoint

Elysium integration

Explorer

Network: Elysium Testnet, chain id 99801
Blocks: 100 ms canonical blocks, about 300 ms perceived receipt
Gas: HYPE, bridged 1:1 from HyperEVM; the payer never needs any
Settles to: HyperEVM Testnet (chain 998)
Stack: Arbitrum Orbit (Nitro/ArbOS), operated with Conduit
Public RPC: https://testnet-rpc.elysium.kinetiq.xyz

Reference

The details.

How quotes, sessions, settlement and receipts work, and what this release does and does not claim.

What is a quote?

A signed, time-bound price for one service call. The provider signs the quote's amount, asset, recipient, parameters hash and expiry with its key, and the 402 that follows must price the resource at exactly that amount. Once accepted, the amount cannot move.

What is a commerce session?

The coordination object for one workflow: a spending limit, the quotes attached to it (from one provider or several), the authorizations, what settled and what was delivered. A session is off-chain state, not an atomic transaction, so a provider failing halfway leaves the session partially settled, with the record of what happened.

What does the facilitator hold?

Nothing. It verifies the payer's EIP-3009 authorization against the payment requirements, broadcasts it and pays the gas. The authorization itself names the recipient and the exact amount, so the facilitator cannot redirect or resize a payment.

Which asset do payments use?

On Elysium Testnet the protocol settles in EPP402TestUSD (EPPUSD), a six-decimal EIP-3009 test asset the project deploys, because the chain's bridged USDC has EIP-2612 but no transferWithAuthorization. The asset has no value and a public faucet. Production assets are configured per network, never assumed.

Is this on mainnet?

No. EPP-402 runs on Elysium Testnet (chain 99801). Mainnet (chain 99901) is pre-launch on the network side and is not deployed on ours; nothing on this site claims otherwise.

How is a receipt verified?

Two checks, both independent of the provider: recover the EIP-712 signature and compare it with the provider address in the discovery document, then read the transaction on Elysium and confirm a transfer of the receipt's amount from the payer to the recipient. The explorer does both for any receipt you paste.

Which x402 clients work?

Any x402 v2 client whose spend controls allow the asset: the EPP-402 asset is not in the SDK's default table, so a client allows it by address with a per-payment cap, as it would any custom token. The EPP-402 SDK does that for you and adds quotes, sessions, intents and receipt verification.

What is EPP-402 not?

Not a wallet, not a chain, not a token and not a checkout page. It is the protocol between a buyer that is software and a seller that is software: discovery, pricing, authorization, settlement and proof.

Start

Sell to software. Buy as software.

Publish a discovery document, put the gate in front of a route, and the first agent that reads it can pay you on Elysium testnet with one signed header.

Read the quickstart Join the registry

terminalIllustrative response

$ curl https://inference.example.com/.well-known/epp402.json
{
  "protocol": "epp-402",
  "version": "1.0.0",
  "provider": {
    "id": "inference.example.com",
    "name": "Example Inference",
    "address": "0xb1297Fea0b54A79BdBCfb8b057e39B226Cc2ebFc",
    "url": "https://inference.example.com"
  },
  "network": "eip155:99801",
  "assets": [
    {
      "network": "eip155:99801",
      "address": "0x…",
      "symbol": "EPPUSD",
      "decimals": 6,
      "name": "EPP-402 Test USD",
      "version": "1",
      "transferMethod": "eip3009"
    }
  ],
  "x402": {
    "version": 2,
    "schemes": [
      "exact"
    ],
    "facilitators": [
      "https://epp402-core.fly.dev/facilitator"
    ]
  },
  "services": [
    {
      "id": "inference.standard",
      "name": "Standard inference",
      "category": "ai-inference",
      "endpoint": "/v1/inference",
      "method": "POST",
      "pricing": {
        "model": "per_request",
        "amount": "10000",
        "asset": "0x…"
      },
      "payment": {
        "protocol": "x402",
        "version": 2,
        "schemes": [
          "exact"
        ],
        "maxTimeoutSeconds": 300
      },
      "quote": {
        "endpoint": "/v1/quotes",
        "required": false
      }
    }
  ],
  "updatedAt": 1794100000
}

Turn HTTP 402 into a settlement gate.

Six stages carry a request from discovery to a receipt.

What has settled on Elysium Testnet.

x402 is the payment. EPP-402 is the commerce around it. Elysium is where it settles.

EPP-402 commerce layer

x402 payment layer

Elysium settlement layer

Your route stays. The gate goes in front of it.

01Publish a discovery document

02Guard a route with payment

03Pay from an agent

One registry, eight kinds of service.

AI inference

Market data

Compute

Storage

APIs and developer services

Data processing

Agent services

Other

Built on the standard, settled on the chain.

x402 compatibility

Elysium integration

The details.

Sell to software. Buy as software.