MPP

#Overview

When MPP is enabled, an unpaid request can return a 402 with a standard payment challenge. The client retries using Authorization: Payment ... and receives a Payment-Receipt header on success. For the underlying payment method, see Tempo's machine payments docs.

Current payment rail:

• Network: Tempo mainnet (4217)
• Settlement asset: pathUSD (0x20c0000000000000000000000000000000000000)
• Tempo has no native gas token. Transaction fees are paid in Tempo stablecoins, so the paying wallet should hold pathUSD.
• Rungate can advertise MPP and x402 on the same unpaid request. MPP-capable clients should follow the payment challenge in WWW-Authenticate.

#Challenge flow

The example below uses Tempo against the same Tempo-mainnet pathUSD payment rail currently advertised by Rungate.

HTTP/1.1 402 Payment Required
WWW-Authenticate: Payment ...
PAYMENT-REQUIRED: <optional x402 fallback>
Content-Type: application/json

{
  "error": {
    "code": 402,
    "message": "Payment required"
  }
}

#Client example

The mppx client can pay the challenge and retry in one call.

import { Mppx, tempo } from "mppx/client";

const mppx = Mppx.create({
  polyfill: false,
  methods: [tempo({ account, getClient: () => walletClient })],
});

const res = await mppx.fetch("https://api.rungate.ai/v1/chat/completions", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    model: "deepseek/deepseek-v3.2",
    messages: [{ role: "user", content: "Say hello." }],
  }),
});

console.log(res.headers.get("payment-receipt"));