> ## Documentation Index
> Fetch the complete documentation index at: https://docs.stellarx402.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Exact payments

> Use the shipped Stellar exact scheme with canonical x402 clients and sponsored fees.

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

## Payment flow

1. The seller returns HTTP 402 with `PaymentRequired`.
2. The buyer checks network, asset, amount, `payTo`, and timeout.
3. The canonical Stellar client signs the Soroban authorization entry.
4. The seller retries with the standard payment header.
5. The facilitator verifies and enforcing-simulates the signed invocation.
6. A channel account becomes the transaction source and the sponsor pays the
   fee bump.
7. 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

```ts theme={"theme":{"light":"github-light","dark":"github-dark"}}
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](/operations/security#pubnet) before enabling a network.