@reinconsole/gate

The supply side of Rein — vendor-side x402 monetization middleware. Price your routes once and every payment into your API is quoted, cross-checked, screened, rate-limited, settled, and receipted before your handler runs.

Status: v0.1 — early open-source infrastructure, live on testnet. Verified live on Base Sepolia against the hosted x402.org facilitator. APIs may change before 1.0. See it running: Rein console.

Install

npm install @reinconsole/gate

Quickstart

import { createGate, gateMiddleware, facilitatorClientRails } from '@reinconsole/gate';

const gate = createGate({
  routes: [
    { path: '/api/answer', price: '0.05', description: 'one research answer' },
    { path: '/api/premium/*', method: 'POST', price: '0.25' },
  ],
  rails: facilitatorClientRails(facilitator), // or mockFacilitatorRails(...) offline
  payTo: '0xYourTreasury…',
  network: 'base-sepolia',
  asset: USDC_ADDRESS,
  screen: { denyPayers: ['0xKnownMule…'] },
});

app.use(gateMiddleware(gate)); // Express, or wrap any node:http handler

In-process instead? createGatedFetch(...) turns the same gate into a fetch-shaped vendor for tests and agent loops.

What it does that a bare 402 snippet doesn't

• Quote consistency. A presented payment must match the gate's own quote — scheme, network, amount, recipient — before any facilitator round-trip. Underpayment is refused at the door.
• Payer screening. Allow/deny lists plus a dynamic screen.check hook (reputation plugs in here — see @reinconsole/graph's payerCheck), checked before verify/settle, so a blocked payer costs you nothing.
• Replay protection. Each payment settles once; the slot is burned before the async legs, so two concurrent copies can't both pass.
• Velocity caps + rate limiting. Per-payer settled-spend caps (maxPayments / maxAmount) and a sliding-window presentation limiter (maxAttempts → 429 + Retry-After). Throttle refusals happen before the replay burn, so a held payment clears once the window slides.
• Honest rails failures. Provably-unsent transport failures are retried, then refused rails_unavailable with the replay slot released; an ambiguous settle refuses settle_unknown with the slot kept burned — the money may have moved, and the gate never guesses.
• Receipts + revenue. Every settlement becomes a GateReceipt; gate.stats() aggregates revenue by asset, route, and payer; quoted / settled / refused events stream on the bus.
• x402 v2 dual-stack. Accepts both payment dialects always; advertiseV2 adds the v2 PAYMENT-REQUIRED header quote beside the v1 body; CAIP-2 and v1 network ids normalize in consistency checks.
• Pluggable rails. The same gate runs against the mock facilitator (@reinconsole/mock-rails) or the real hosted facilitator (@reinconsole/x402-rails) — a two-method structural seam.

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