Payment rail

Aptos

On Aptos, the challenge carries the ATR hash; a standard transfer has no field for it. Source: lcp docs: rails⁠ (opens in a new tab) The Agentic Transaction Record (ATR) is one record of exactly what was agreed, for one transaction. Its ATR hash, the ATR’s fingerprint, is the proof bound to the transaction: change one byte of the ATR and it no longer matches. Source: lcp docs: the ATR⁠ (opens in a new tab) · Source: lcp docs: the ATR hash⁠ (opens in a new tab)

lcp docs: rails⁠ (opens in a new tab) · lcp docs: the ATR⁠ (opens in a new tab) · lcp docs: the ATR hash⁠ (opens in a new tab)

Aptos

Example

Field: the challenge only

What the payer signs carries none of the ATR hash; where it rides instead is below.

This example’s ATR hash, as it rides

Where the ATR hash rides

On this rail, the ATR hash rides in the challenge only.

Exhibit Each field, and the pairings that use it

What a payment on this rail proves

On this pairing, the buyer’s signature does not cover the ATR hash, the payment does not leave a public proof of it, and no one can read it back from the chain alone. Source: lcp docs: pairings reference⁠ (opens in a new tab)

Switch to Technical to see each pairing, and the sentence its record states about what a payment through it proves.

lcp docs: pairings reference⁠ (opens in a new tab)

Exhibit Each pairing’s record

The package

Pattern: HTTP-layer advisory (LCP §8.3.7)⁠ (opens in a new tab)
Where the ATR hash rides: The challenge only. No field of a standard Aptos transfer carries H; the seller ties the payment to H when it claims it for the request.
What a payment through it proves: Before this payment, the buyer signed and paid an agreement transaction carrying this ATR's hash on <network>, recorded in <transaction>. The ATR was assembled before the challenge went out, and the challenge advertised its hash and link. The payer's signed Aptos transaction does not carry the hash. The seller tied the hash to this payment when it claimed it for this request, and identified the settlement as the payer's committed transaction by sender, sequence number and a digest of its transfer. This does not show that the buyer's approval carried the hash, or that amount, payee, asset or timing match the ATR's content.

Where a sentence names <network> and <transaction>, the pairing’s record fills them in: they name the agreement payment the buyer made first. Source: lcp docs: pairings reference⁠ (opens in a new tab) · Source: lcp docs: the agreement URL⁠ (opens in a new tab)

Reading the settlement

The package reads a payment’s settlement through a reader you supply: the endpoint, the credentials, the timeouts and the retries are yours. A reader that fails never makes a payment read as failed. Source: lcp docs: reading settlement⁠ (opens in a new tab)

lcp docs: reading settlement⁠ (opens in a new tab)

Exhibit How the package reads this rail’s settlement

The protocols that pay on it

x402

lcp docs: rails⁠ (opens in a new tab)

Ready to see your own agreements proved?

Tell us what you sell, buy or carry, and we will show you where the agreement rides in it.

Integra Binder, hosted by Integra, does the seller’s side of each agreement and is free on test networks, with test-network USDC.

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