x402

@lemmaoracle/x402

Drop-in replacement for @x402/* with automatic Lemma discovery and zero-knowledge proof submission.

Overview

Switch your x402 imports from @x402/* to @lemmaoracle/x402 and get automatic ZK proof generation on every settlement. The package adds Lemma discovery metadata and proof submission without changing your existing x402 integration code.

Install

npm install @lemmaoracle/x402 @lemmaoracle/sdk

@lemmaoracle/sdk is a required peer dependency.

Quick Start

import { Hono } from "hono";
import {
  HTTPFacilitatorClient,
  x402ResourceServer,
  paymentMiddleware,
  ExactEvmScheme,
} from "@lemmaoracle/x402";

const app = new Hono();
const facilitator = new HTTPFacilitatorClient();

// Pass LemmaConfig to enable proof generation; omit to use as plain @x402/* wrapper
const server = new x402ResourceServer(facilitator, {
  apiKey: "your-lemma-api-key",
  discovery: { schemas: ["dev:document:v1"] },
});

app.use(
  "/verify/:hash",
  paymentMiddleware(
    {
      "GET /verify/:hash": {
        price: "$0.01",
        network: "base-sepolia",
        resource: "verification-api",
        scheme: ExactEvmScheme,
        paysTo: "0xYourAddress",
      },
    },
    server,
  ),
);

app.get("/verify/:hash", async (c) => {
  return c.json({ verified: true, hash: c.req.param("hash") });
});

How it works

After each x402 settlement, the augmented x402ResourceServer automatically triggers a onAfterSettle hook that registers the payment as a Lemma document, generates a ZK proof via a Node.js relay, and submits the proof to the Lemma oracle. Proof data is included in the settlement response header.

Exports

Re-exports from @x402/* — HTTPFacilitatorClient, ExactEvmScheme, x402Client, plus associated types (Network, PaymentRequirements, PaymentPayload, FacilitatorConfig).

Augmented exports — x402ResourceServer (auto-attaches Lemma hook), paymentMiddleware (auto-enriches routes with discovery metadata).

Advanced (@lemmaoracle/x402/advanced) — createLemmaSubmissionHandler, resolveDiscoveryConfig, for custom orchestration. See LemmaConfig type for all configuration options.

ZK Circuit

This package includes a Circom circuit (circuits/payment.circom) that generates a Groth16 proof of a valid x402 payment. Commitment: Poseidon6(txHashLow, txHashHigh, recipientLow, amount, timestamp, minAmount).

Development

pnpm install
pnpm build          # compile TypeScript
pnpm build:circuit  # build the Circom circuit
pnpm test           # run tests
pnpm register       # register circuit with Lemma (requires env vars)

License

Apache-2.0