payment-tempo

MPP Tempo charge client for Faremeter — wraps mppx into a faremeter MPPPaymentHandler so @faremeter/fetch's wrap() can auto-handle tempo.charge 402s alongside x402.

Architecturally analogous to @faremeter/payment-solana/charge but for Tempo (Stripe's L2). All the actual signing and transaction building is done by mppx — this package is a ~80 LOC adapter between two type vocabularies.

Why

Faremeter's MPP support today ships only the Solana flavor (createMPPSolanaChargeClient). Most real-world MPP services on the wire (Frames Registry, mpp.dev's Firecrawl, Brave Search, etc.) advertise method="tempo" and were unpayable through faremeter alone. This package closes that gap.

Install

bun add @frames-ag/payment-tempo @faremeter/fetch viem mppx

Use

import { wrap } from "@faremeter/fetch";
import { createMPPTempoChargeClient } from "@frames-ag/payment-tempo";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(process.env.TEMPO_PRIVATE_KEY as `0x${string}`);

const fetchPaid = wrap(fetch, {
  handlers: [],
  mppHandlers: [createMPPTempoChargeClient({ account })],
});

const res = await fetchPaid("https://api.firecrawl.dev/v1/scrape", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ url: "https://example.com" }),
});
// On 402 with WWW-Authenticate: Payment, this handler signs a Tempo
// USDC transfer via mppx, attaches the credential, and retries.

Stack with x402 handlers; faremeter routes per challenge:

const fetchPaid = wrap(fetch, {
  handlers: [
    createPaymentHandler(evmWallet),         // x402 EVM
    createPaymentHandler(solanaWallet, mint) // x402 Solana
  ],
  mppHandlers: [
    createMPPTempoChargeClient({ account }),  // MPP Tempo charge
    createMPPSolanaChargeClient({ wallet, mint }), // MPP Solana charge
  ],
});

API

createMPPTempoChargeClient(args)

Returns an MPPPaymentHandler that accepts tempo.charge challenges.

| Arg | Type | Description | |---|---|---| | account | viem.Account | viem account (any LocalAccount, e.g. from privateKeyToAccount) | | mode? | "push" \| "pull" | Override transaction submission mode. Defaults to push for JSON-RPC accounts, pull for local accounts | | clientId? | string | Client identifier baked into attribution memos |

Returns null for any challenge whose method !== "tempo" or intent !== "charge". faremeter's fetch wrap then tries the next handler.

Status

• ✅ Structural smoke passes (bun smoke) — null cases, valid challenges, malformed requests all routed correctly
• ⏳ End-to-end Tempo Devnet smoke pending a public Devnet MPP seller
• ⏳ End-to-end Tempo Mainnet smoke pending a funded Tempo wallet (Stripe-side bridge flow)

Roadmap to upstreaming

This package is built faremeter-shaped on purpose so it can be upstreamed as packages/payment-tempo/charge (or similar) in faremeter/faremeter. Steps:

1. Validate against a real Tempo charge endpoint
2. Mirror exact code style of payment-solana/charge
3. Open PR

Until then it lives standalone under @frames-ag/payment-tempo.

Reference material

• @faremeter/payment-solana/charge/client.ts — the structural template this mirrors
• mppx/client/Charge — the underlying SDK doing the actual Tempo signing
• @websets/wallet-mpp/mpp-provider-client.ts — production-quality MPP client (mppx-based) that informed this design