Exact payments

exact authorizes one fixed atomic amount. It is the shipped Stellar scheme and the critical path for the public testnet preview.

Payment flow

The seller returns HTTP 402 with PaymentRequired.
The buyer checks network, asset, amount, payTo, and timeout.
The canonical Stellar client signs the Soroban authorization entry.
The seller retries with the standard payment header.
The facilitator verifies and enforcing-simulates the signed invocation.
A channel account becomes the transaction source and the sponsor pays the fee bump.
The seller receives a standard settlement response and the resource result.

The facilitator does not take custody of the payment asset. It is never the payer or recipient.

Canonical client

import { x402Client, x402HTTPClient } from "@x402/core/client";
import { createEd25519Signer } from "@x402/stellar";
import { ExactStellarScheme } from "@x402/stellar/exact/client";

const network = "stellar:testnet" as const;
const client = new x402Client().register(
  network,
  new ExactStellarScheme(
    createEd25519Signer(process.env.BUYER_SECRET_KEY!, network),
  ),
);
const http = new x402HTTPClient(client);

The buyer signs only the payment authorization. The facilitator reconstructs the outer transaction and rejects client-controlled source and fee data.

Verification guarantees

The exact path checks the standard { transaction } payload, contract and function, payer, recipient, configured asset, atomic amount, authorization signature, expiration, and authorization tree. Enforcing simulation executes custom __check_auth accounts and token behavior before a sponsored transaction is submitted. The final event check requires exactly one matching SEP-41 transfer event and expected balance changes.

Atomic-unit amounts and assets

Amounts are integer strings. The facilitator supports configured SEP-41/SAC assets, including testnet XLM SAC and testnet USDC in the checked-in profile. An issued asset still requires the payer and recipient to have the appropriate trustline and issuer authorization.

Evidence boundary

The repository contains real testnet exact settlement hashes and an official testnet x402 E2E result. Pubnet exact evidence is not claimed yet. See release status before enabling a network.

Getting started

Build

Discover

Protocol

Upto (proposed)

Operate

Reference

Payment flow

Canonical client

Verification guarantees

Atomic-unit amounts and assets

Evidence boundary

​Payment flow

​Canonical client

​Verification guarantees

​Atomic-unit amounts and assets

​Evidence boundary

Payment flow

Canonical client

Verification guarantees

Atomic-unit amounts and assets

Evidence boundary