@pause/x402-risk

PAUSE Risk Extension for x402 — risk-score every address before payment.

Stop AI agents from paying malicious addresses. @pause/x402-risk adds PAUSE Risk Engine scoring to the x402 payment protocol, blocking payments to high-risk wallets before any money moves.

Works with @x402/fetch, @x402/axios, Express, Hono, and any custom x402 flow.

Why

x402 lets agents pay for resources over HTTP. But agents pay whatever address the server tells them to — blindly.

• The 402Bridge hack drained 200+ users' USDC
• x402 V2's dynamic payTo routing means addresses can change per-request
• AI agents executing payments autonomously have no human oversight

@pause/x402-risk fixes this. Every payTo address is scanned across 11 Bayesian risk signals before your agent signs anything. HIGH risk = payment blocked. Zero funds lost.

Install

npm install @pause/x402-risk

Quick Start — Client (Protect Your Agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";
import { createRiskGuard, wrapFetchWithRiskGuard } from "@pause/x402-risk/client";

// Setup x402 client (standard)
const client = new x402Client();
registerExactEvmScheme(client, {
  signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`),
});

// Add PAUSE risk guard — ONE LINE
const guard = createRiskGuard({ minScore: 40 });

// Wrap fetch with both payment and risk
const safeFetch = wrapFetchWithRiskGuard(
  wrapFetchWithPayment(fetch, client),
  guard
);

// Every payment is now risk-scored automatically
const response = await safeFetch("https://api.example.com/paid-endpoint");

If the payTo address scores below 40 (HIGH risk), the payment is blocked and a PaymentBlockedError is thrown. No signature. No gas. No funds lost.

Quick Start — Server (Protect Your Service)

import express from "express";
import { paymentMiddleware } from "@x402/express";
import { createRiskMiddleware } from "@pause/x402-risk/server";

const app = express();

// Add PAUSE risk check BEFORE x402 payment middleware
app.use(createRiskMiddleware({ minScore: 40 }));

// Standard x402 paywall
app.use(paymentMiddleware({ /* your routes */ }, resourceServer));

Payers with HIGH risk wallets are rejected with a 403 before your endpoint runs.

Configuration

const guard = createRiskGuard({
  // Required
  minScore: 40,           // Block addresses scoring below this (0-100)

  // Optional
  riskEngineUrl: "https://api.pausescan.com",  // PAUSE Risk Engine URL
  apiKey: "pk_...",       // Pro API key (50 free scans/month without)
  warnScore: 70,          // Trigger onWarning callback below this score
  cacheTtlMs: 300000,     // Cache scores for 5 minutes (default)
  timeoutMs: 5000,        // Risk engine timeout (default)
  failOpen: false,        // true = allow payment if engine is down

  // Address lists
  allowlist: ["0xYourWallet", "0xTrustedPartner"],
  blocklist: ["0xKnownScammer"],

  // Callbacks
  onBlocked: (assessment, payTo) => { /* log, alert, etc */ },
  onWarning: (assessment, payTo) => { /* caution logging */ },
  onAssessment: (assessment, payTo) => { /* every scan */ },
});

Risk Scoring

The PAUSE Risk Engine analyzes each address across 11 independent Bayesian signals:

| Signal | Weight | What It Detects | |---|---|---| | Mixer Exposure | 0.45 | Tornado Cash and mixing service interaction | | Draining Pattern | 0.30 | Wallet drainer behavior (approve + sweep) | | Exchange Cluster | 0.25 | Proximity to exchange hot/cold wallets | | Sweep Pattern | 0.25 | Funds consolidation into single address | | TX Burst Anomaly | 0.20 | Bot-like transaction volume spikes | | Scam Graph | 0.20 | Connections to reported scam addresses | | Dusting Attack | 0.15 | Micro-transactions for wallet tracking | | ENS Authenticity | 0.15 | ENS domain ownership verification | | Rival Consensus | 0.15 | Cross-reference with external scoring | | Wallet Age | 0.10 | Account creation date and activity | | Balance Volatility | 0.10 | Abnormal balance fluctuation patterns |

Signals are combined using log-odds Bayesian scoring with correlation discounting to produce a single 0-100 safety score.

| Score | Risk | Action | |---|---|---| | 70-100 | SAFE | Payment proceeds normally | | 40-70 | MEDIUM | Payment proceeds, onWarning fires | | 0-40 | HIGH | Payment BLOCKED, PaymentBlockedError thrown |

Standalone Usage (No x402)

Use the risk engine directly for any address screening:

import { PauseRiskEngine } from "@pause/x402-risk";

const engine = new PauseRiskEngine();
const result = await engine.scan("0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045");

console.log(result.score);    // 87
console.log(result.risk);     // "SAFE"
console.log(result.signals);  // Array of 11 signal results

Error Handling

import { PaymentBlockedError, RiskEngineUnavailableError } from "@pause/x402-risk";

try {
  const response = await safeFetch("https://api.example.com/paid");
} catch (error) {
  if (error instanceof PaymentBlockedError) {
    // Address was HIGH risk — payment blocked, no funds lost
    console.log(error.assessment.score);  // e.g., 23
    console.log(error.assessment.risk);   // "HIGH"
    console.log(error.payTo);             // "0x..."
  }
  if (error instanceof RiskEngineUnavailableError) {
    // Risk engine down and failOpen=false
    console.log(error.payTo);
  }
}

API Reference

Client

| Export | Description | |---|---| | createRiskGuard(config) | Create a risk guard instance | | wrapFetchWithRiskGuard(fetch, guard) | Wrap fetch with risk checking | | createRiskCheck(config) | Standalone risk check function |

Server

| Export | Description | |---|---| | createRiskMiddleware(config) | Express/Connect middleware | | createPayerCheck(config) | Standalone payer check function |

Core

| Export | Description | |---|---| | PauseRiskEngine | Direct risk engine client | | PaymentBlockedError | Error thrown when payment is blocked | | RiskEngineUnavailableError | Error thrown when engine is unreachable |

Links

• PAUSE Platform: pausesecure.com
• Free Scanner: pausescan.com
• x402 Protocol: x402.org
• Smart Contract: PAUSECommit V2 on Etherscan

License

MIT — PAUSE (Pre-Authorization Unified Security Engine)