@rail402.dev/scheme-upto-stellar

The upto settlement scheme for Stellar. A buyer authorizes a ceiling and only the actual usage settles, which fits metered services such as token billing or per-call APIs. A Soroban contract enforces the ceiling and single settlement on-ledger. (exact charges a fixed price; upto charges "authorize up to N, settle what was used".)

What you need

Node.js 20+, testnet only. Registration is the same as the exact scheme, so you also use a stock x402 client, a @x402/stellar signer, and a facilitator that supports upto.

Install

npm install @rail402.dev/scheme-upto-stellar

Buyer side

Register the scheme on a stock x402 client:

import { x402Client } from "@x402/core/client";
import { wrapFetchWithPayment } from "@x402/fetch";
import { createEd25519Signer } from "@x402/stellar";
import { UptoStellarClientScheme } from "@rail402.dev/scheme-upto-stellar";

const signer = createEd25519Signer(process.env.STELLAR_SECRET, "stellar:testnet");

const client = new x402Client();
client.register("stellar:*", new UptoStellarClientScheme(signer));

const res = await wrapFetchWithPayment(fetch, client)("https://metered.example/tokens");

Facilitator side

import { UptoStellarFacilitatorScheme } from "@rail402.dev/scheme-upto-stellar";

facilitator.register("stellar:testnet", new UptoStellarFacilitatorScheme(signers));

Sellers register UptoStellarServerScheme on their x402ResourceServer.

Exports: UptoStellarClientScheme, UptoStellarServerScheme, UptoStellarFacilitatorScheme, UPTO_CONTRACTS, uptoContractFor.

Part of Rail402. Apache-2.0.