@ftptech/x402-canton-client

Payer-side SDK for Canton x402. Lets an autonomous agent pay for x402-gated HTTP resources using a CantonSigner that submits a CIP-56 TransferFactory_Transfer from the agent's Canton participant.

Install

npm i @ftptech/x402-canton-client

Note: the @ftp npm scope is not final — it may change before the first public release (see docs/PUBLISHING.md). Pin the version you install and check the README for the current package name.

What's in here

• CantonSigner interface — abstracts how a CIP-56 transfer is signed and submitted (real participant via Cip56KeyfileSigner, mock for tests, hosted-party variants).
• Cip56KeyfileSigner + makeCip56KeyfileSigner(config) — production signer that loads an Ed25519 key from a PEM file (or env-var PEM string) and drives the participant's interactive-submission prepare/sign/execute flow for TransferFactory_Transfer.
• ExactCantonScheme — builds x402 v2 PaymentPayload envelopes from PaymentRequirements + a signer.
• wrapFetchWithCantonPayment(fetch, signer) — drop-in fetch replacement that detects 402, decodes PAYMENT-REQUIRED, calls the signer, retries with PAYMENT-SIGNATURE, throws X402PaymentError with a stable code field on failure.
• readPaymentResponseHeader(response) — decodes the v2 PAYMENT-RESPONSE settlement header.

Quick example

import {
  wrapFetchWithCantonPayment,
  readPaymentResponseHeader,
  makeCip56KeyfileSigner,
} from "@ftptech/x402-canton-client";

const signer = makeCip56KeyfileSigner({
  participantUrl:   "https://your-participant/ledger-api",
  participantToken: "<bearer>",
  scanUrl:          "https://scan.your-sv/api/scan",
  party:            "agent_party::1220...",
  keyPath:          "/run/secrets/agent.pem",
});

const fetchWithPay = wrapFetchWithCantonPayment(fetch, signer);
const res = await fetchWithPay("https://api.example.com/data");
const settle = readPaymentResponseHeader(res);

See docs/quickstart.md for the full demo flow and examples/agent-buyer/ for a runnable agent.

Project

github.com/sunstrike228/canton-x402.