sentinel-agent

Governance SDK for x402 AI agent payments

Real-time spend caps, audit logs, and anomaly detection for every micro-transaction your agents make.

Website · Dashboard · Docs · Changelog

What is Sentinel?

AI agents spend real money through x402 micro-transactions. Without governance, a single misconfigured agent can drain budgets in minutes. Sentinel sits between your agent and the payment network — intercepting every call, enforcing spend limits, and logging a complete audit trail.

One package. One line of code. Full visibility.

Quick Start

npm install sentinel-agent

import { createSentinel } from 'sentinel-agent'

const fetch = createSentinel({
  apiKey: process.env.SENTINEL_API_KEY,
  perCallCap: 1.00,
  dailyCap: 50.00,
  allowlist: ['api.openai.com', 'api.anthropic.com'],
})

const response = await fetch('https://api.openai.com/v1/chat/completions', {
  method: 'POST',
  headers: { Authorization: `Bearer ${process.env.OPENAI_KEY}` },
  body: JSON.stringify({ model: 'gpt-4o', messages: [...] }),
})

Features

| Feature | Description | |---------|-------------| | Per-call caps | Reject any call exceeding your limit before funds move | | Hourly & daily budgets | Rolling-window enforcement with instant rejection | | Lifetime caps | Hard ceiling on total agent spend | | Allowlist / blocklist | Lock endpoints to a known-safe list | | Audit trail | Agent ID, endpoint, amount, tx hash, timestamp | | Anomaly detection | Spike alerts when frequency exceeds 3× baseline | | Dashboard | Live analytics at sentinelagent.xyz/dashboard | | Zero refactoring | Drop-in x402 fetch replacement | | TypeScript-first | Full types and .d.ts exports |

Architecture

Your Agent
    │  fetch(url, options)
    ▼
┌─────────────────────────┐
│     sentinel-agent      │
│  ┌───────────────────┐  │
│  │  Policy Engine    │  │  ← caps + allow/blocklist (local, zero-RTT)
│  └────────┬──────────┘  │
│           │ allowed?    │
│           ▼             │
│  ┌───────────────────┐  │
│  │  x402 Payment     │  │  ← original fetch proceeds
│  └────────┬──────────┘  │
│           │ receipt     │
│           ▼             │
│  ┌───────────────────┐  │
│  │ Transaction Logger│  │  ← fire-and-forget to Sentinel API
│  └───────────────────┘  │
└─────────────────────────┘
    │
    ▼  sentinelagent.xyz/dashboard

Roadmap

• [x] Per-call, hourly, daily, lifetime spend caps
• [x] Allowlist and blocklist enforcement
• [x] Complete audit trail with tx hash
• [x] Anomaly detection and spike alerts
• [x] Base mainnet + Arbitrum support
• [x] Live dashboard at sentinelagent.xyz
• [ ] Webhook events (tx.approved, alert.critical, budget.80pct)
• [ ] Proxy mode — no SDK install required

License

MIT © 2026 Sentinel — sentinelagent.xyz