How it works
An app, a backend or an AI agent requests your API.
Before it signs anything, your policy engine says allow, wait for a human, or deny.
Only on allow does it sign the payment - testnet today.
x402Serve() checks it and lets the request through.
It settles on Stellar in ~5 s - and if you anchor it, anyone can verify the receipt from the CID alone.
Before your agent signs a payment, Nirium asks your policy engine.
// excerpt - call() is your own HTTP helper to your policy engine
agent.initX402({
signer, network: "stellar:testnet",
policy: {
requireExpiry: true,
evaluate: (ctx, { signal }) =>
call("decide", { method: "POST", body: JSON.stringify(ctx), signal }),
currentVersion: async (_ctx, { signal }) =>
(await call("version", { signal })).policyVersion,
onDecision: (record) =>
call("outcome", { method: "POST", body: JSON.stringify(record) }),
},
});New in 0.16.0 · experimental - the shape may change before 1.0. Tested on testnet, engine-neutral by design (no smart account required on your side).
The hook itself doesn't resolve concurrent requests - your engine does. AgentLedger's does it atomically (verified 2026-10-09, testnet). Code running in the same process as the raw signer can still sign around the hook - that gap (L02) is still open.
Three decisions, verified against Horizon
Integration test coordinated with AgentLedger.
One middleware, and your API charges per call.
import express from 'express';
import { x402Serve } from 'nirium';
const app = express();
app.use(x402Serve({
payTo: process.env.PAY_TO, // your G... address
facilitatorApiKey: process.env.FACILITATOR_KEY, // free testnet key
routes: { 'GET /weather': '$0.05' }, // testnet by default
}));
app.get('/weather', (_req, res) => res.json({ tempC: 21 }));
app.listen(3000);Ran verbatim with nirium@0.18.0 on testnet (9 Nov 2026): 402, then paid, then 200.
Open to everyone on testnet. Nirium's own endpoint answers 402 on mainnet; its last payment settled on 29 Sep 2026. Charging on your own API (x402Serve) on mainnet is not something we promote for third parties while the legal review closes.
npm i nirium express @x402/express @x402/core @x402/stellar
Any x402 client works, from a testnet account with USDC.
Any settlement can become a receipt anyone can check from a hash alone.
POST /api/audit/log
// example request, not a live anchor:
{ "hash": "sha-256:e3b0c442...", "tag": "invoice-2026-07" }Live on mainnet · free during beta.
Verify a signed mainnet anchor (our own test, 2026-10-21)Every claim below resolves to something public.
POLICY
CHARGE
Legal notice - Nirium is B2B software-only infrastructure and never custodies funds; financial services (SPEI onramp, CETES custody) are operated by regulated third parties. Read full legal notice →
Start on testnet in five minutes. Nirium's own endpoint answers 402 on mainnet; third-party mainnet use is not something we promote while legal review stays open.
See live usageAll rate data shown is protocol reference information only - not a return projection or guarantee.