From npm install to a governed agent payment.

$ node -v
v22.14.0   # anything ≥22

$ mkdir rein-quickstart
$ cd rein-quickstart
$ npm init -y
$ npm install @reinconsole/sdk @reinconsole/gate @reinconsole/mock-rails @reinconsole/core   # ~15 s

$ npx -p @reinconsole/policy-engine rein-policy-engine
[rein] policy-engine listening on http://0.0.0.0:8787

// guard-quickstart.mjs — cap an agent's spend, offline, in one file.
// Prereq: the policy engine is running:  npx -p @reinconsole/policy-engine rein-policy-engine
import { newId } from '@reinconsole/core';
import { createGuard, EngineClient, PaymentBlockedError } from '@reinconsole/sdk';
import { MockLedger, MockFacilitator, createMockVendor } from '@reinconsole/mock-rails';

const engineUrl = 'http://127.0.0.1:8787';
const wallet = '0xResearch01';

// A simulated x402 world: a ledger, a settlement facilitator, and a
// paywalled vendor charging $0.01 per call. No accounts, no chain, no funds.
const ledger = new MockLedger();
const facilitator = new MockFacilitator({ ledger, name: 'mock-facilitator' });
const vendor = createMockVendor({ facilitator, atomicPrice: '10000', payTo: '0xVendorTreasury' });

// 1. Register the agent with the policy engine
const client = new EngineClient({ baseUrl: engineUrl });
const agent = await client.registerAgent({
  orgId: newId('org'),
  name: 'research-agent',
  wallets: [{ chain: 'base', address: wallet, mode: 'sdk' }],
});

// 2. Wrap fetch with the guard
const guard = createGuard({
  engineUrl,
  agentId: agent.id,
  fetch: vendor.fetch,                    // swap for globalThis.fetch against real vendors
  payer: facilitator.payerFor(wallet),
});

// 3. Set the rules: max $0.50 per tx, max $0.04 per rolling hour
await guard.client.addPolicy({
  policyId: 'starter-policy',
  appliesTo: { agents: [agent.id] },
  rules: [
    { id: 'tx-cap', deny: { amountGt: '0.50' } },
    { id: 'hour-budget', deny: { rollingSum: { window: '1h', gt: '0.04' } } },
  ],
  default: 'allow',
});

// 4. Spend within budget — four $0.01 calls sail through
const guarded = guard.wrap();
for (let i = 1; i <= 4; i++) {
  await guarded('https://api.data.test/v1/query');
  const r = guard.receipts().at(-1);
  console.log(`call ${i}  ALLOW  $0.0${i}/$0.04 spent · tx ${r.settlement?.txHash?.slice(0, 12)}…`);
}

// 5. The fifth call would breach the budget — denied BEFORE any payment exists
try {
  await guarded('https://api.data.test/v1/query');
} catch (e) {
  if (!(e instanceof PaymentBlockedError)) throw e;
  console.log(`call 5  DENY   ${e.decision.reason}`);
  console.log(`ledger has ${ledger.entries().length} entries — the denied payment was never constructed`);
}

$ node guard-quickstart.mjs

call 1  ALLOW  $0.01/$0.04 spent · tx 0x5ab6460ff8…
call 2  ALLOW  $0.02/$0.04 spent · tx 0xa8725d31cb…
call 3  ALLOW  $0.03/$0.04 spent · tx 0x5de05ac3a4…
call 4  ALLOW  $0.04/$0.04 spent · tx 0x565141762f…
call 5  DENY   denied by: hour-budget
ledger has 4 entries — the denied payment was never constructed

// gate-quickstart.mjs — put a paywall on any Node API, offline, in one file.
// Prereq: the policy engine is running:  npx -p @reinconsole/policy-engine rein-policy-engine
import { createServer } from 'node:http';
import { newId } from '@reinconsole/core';
import { createGuard, EngineClient } from '@reinconsole/sdk';
import { createGate, gateMiddleware, mockFacilitatorRails } from '@reinconsole/gate';
import { MockLedger, MockFacilitator } from '@reinconsole/mock-rails';

// A simulated settlement network (swap for facilitatorClientRails(...) on real rails)
const ledger = new MockLedger();
const facilitator = new MockFacilitator({ ledger, name: 'mock-facilitator' });

// 1. Price your routes
const gate = createGate({
  routes: [
    { path: '/api/answer', price: '0.05', description: 'one research answer' },
    { path: '/api/premium/*', method: 'POST', price: '0.25' },
  ],
  rails: mockFacilitatorRails(facilitator),
  payTo: '0xVendorTreasury',
  network: 'base',
  asset: 'USDC',
});

// 2. Put the middleware in front of your handler (Express: app.use(gateMiddleware(gate)))
const paywall = gateMiddleware(gate);
const server = createServer((req, res) => {
  paywall(req, res, () => {
    res.writeHead(200, { 'content-type': 'application/json' });
    res.end(JSON.stringify({ answer: 42 }));
  });
});
await new Promise((r) => server.listen(8402, '127.0.0.1', r));

// 3. An unpaid caller gets a machine-readable 402 quote, not a dead end
const unpaid = await fetch('http://127.0.0.1:8402/api/answer');
const quote = await unpaid.json();
console.log(`unpaid  HTTP ${unpaid.status} — quote: ${quote.accepts[0].maxAmountRequired} atomic USDC to ${quote.accepts[0].payTo}`);

// 4. A guarded agent buys through the paywall — Rein on both sides of the wire
const engineUrl = 'http://127.0.0.1:8787';
const wallet = '0xBuyerWallet01';
const client = new EngineClient({ baseUrl: engineUrl });
const agent = await client.registerAgent({
  orgId: newId('org'),
  name: 'buyer-agent',
  wallets: [{ chain: 'base', address: wallet, mode: 'sdk' }],
});
const guard = createGuard({
  engineUrl,
  agentId: agent.id,
  payer: facilitator.payerFor(wallet),
  fetch: (input, init) => globalThis.fetch(input, init),
});
await guard.client.addPolicy({
  policyId: 'buyer-policy',
  appliesTo: { agents: [agent.id] },
  rules: [{ id: 'tx-cap', deny: { amountGt: '1.00' } }],
  default: 'allow',
});

const paid = await guard.wrap()('http://127.0.0.1:8402/api/answer');
console.log(`paid    HTTP ${paid.status} · ${JSON.stringify(await paid.json())}`);

// One payment, receipts on BOTH sides that agree
const buyerReceipt = guard.receipts().at(-1);
const gateReceipt = gate.receipts.at(-1);
console.log(`buyer receipt  ${buyerReceipt.id.slice(0, 16)}… · $${buyerReceipt.amount} · tx ${buyerReceipt.settlement?.txHash?.slice(0, 12)}…`);
console.log(`gate receipt   ${gateReceipt.id.slice(0, 16)}… · $${gateReceipt.amount} · tx ${gateReceipt.transaction?.slice(0, 12)}…`);

server.close();

$ node gate-quickstart.mjs

unpaid  HTTP 402 — quote: 50000 atomic USDC to 0xVendorTreasury
paid    HTTP 200 · {"answer":42}
buyer receipt  rcp_01KX3SM05MS3… · $0.05 · tx 0xa650338ff1…
gate receipt   grc_01KX3SM05GDR… · $0.05 · tx 0xa650338ff1…

$ pnpm --filter @reinconsole/demo demo:sepolia

$ pnpm --filter @reinconsole/demo demo:sepolia-8004