AI agents pay USDC on Base for private internet access through Sentinel's decentralized VPN network.
Live at x402.sentinel.co.
One HTTP request. No KYC. No accounts. No P2P tokens. No custom contract to deploy. The agent signs an EIP-3009 USDC transfer, our facilitator settles it on Base, the server provisions a Sentinel subscription with a gas fee grant, and the agent connects to the VPN — paying zero gas.
import{x402Client,wrapFetchWithPayment}from'@x402/fetch';import{ExactEvmScheme}from'@x402/evm/exact/client';import{createWallet,connect}from'blue-js-sdk/ai-path';constwallet=awaitcreateWallet();constscheme=newExactEvmScheme({ address, signTypedData });constclient=newx402Client();client.register('eip155:8453',scheme);constpaidFetch=wrapFetchWithPayment(fetch,client);constres=awaitpaidFetch('https://x402.sentinel.co/vpn/connect/30days',{method: 'POST',body: JSON.stringify({sentinelAddr: wallet.address}),});const{ subscriptionId, feeGranter, nodeAddress }=awaitres.json();constvpn=awaitconnect({mnemonic: wallet.mnemonic, subscriptionId, feeGranter, nodeAddress,protocol: 'v2ray'});// protocol:'v2ray' = zero admin on Windows, binary auto-installs (~70% of nodes).// vpn.connected === true — agent's IP is now a Sentinel node, zero gas paidAgent x402 Server Sentinel Chain
───── ─────────── ──────────────
1. POST /vpn/connect/30days Returns HTTP 402 +
{ sentinelAddr } PAYMENT-REQUIRED header
│ (amount, asset, payTo, network)
│
2. @x402/fetch reads 402, Facilitator verifies + settles
signs EIP-3009 USDC transfer on Base (~2s)
transferWithAuthorization
│ │
3. Resends with ──────────────────────────────> MsgShareSubscription
PAYMENT-SIGNATURE Server then sends one atomic + MsgGrantAllowance
│ Sentinel TX: (fee grant for agent)
│
4. 200 OK with provisioning Returns subscriptionId,
credentials feeGranter, nodeAddress, nodes[]
│
5. connect({ mnemonic, ─────────────────────────────> MsgStartSession
subscriptionId, feeGranter, (gas paid by operator)
nodeAddress })
│
6. Handshake directly with VPN node (WireGuard/V2Ray). We never see the tunnel.
│
7. VPN tunnel up. Agent is private.
Key property: USDC payment uses native EIP-3009 transferWithAuthorization — no custom contract to deploy, no approve() step, no token-allowance round-trip. The asset address in every payment is the canonical USDC contract on Base: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913.
x402/
├── server/ — x402 HTTP 402 VPN server (the one you run)
│ └── src/
│ ├── index.ts — Express routes + x402 paymentMiddleware
│ ├── facilitator.ts — Self-hosted EIP-3009 facilitator
│ └── sentinel.ts — MsgShareSubscription + MsgGrantAllowance
│
├── client/ — Reference agent client (@x402/fetch wrapper)
│
├── docs/ — Public site (docs/index.html)
│
└── fresh-test/ — End-to-end tests against a live server
The api/, contracts/, and sdk/ directories contain an earlier event-watcher design (custom payment contract + agentId registration + polling). The HTTP 402 + EIP-3009 flow in server/ is the canonical implementation — it needs no contract, no event watcher, and no database, and auto-creates Sentinel subscriptions on demand. The live deployment at x402.sentinel.co runs server/.
| Chain | Payment Method | Status |
|---|---|---|
| Base | Native USDC + EIP-3009 transferWithAuthorization (no custom contract) | Live on mainnet |
| Solana | SPL USDC transfer + memo (Helius webhook) | Code written, not yet enabled |
| Endpoint | Days | Price |
|---|---|---|
POST /vpn/connect/1day | 1 | $0.033 USDC |
POST /vpn/connect/7days | 7 | $0.233 USDC |
POST /vpn/connect/30days | 30 | $1.00 USDC |
Pricing is configurable per operator — see server/src/index.ts.
cd server
cp .env.example .env # fill in operator details (see below)
npm install
npx tsc
node dist/index.jsServer starts on http://localhost:4020. The self-hosted facilitator starts on :4021.
You need:
- EVM wallet on Base — receives USDC payments, also funds the facilitator (~0.001 ETH per settlement)
- Sentinel wallet — holds P2P tokens for chain gas (~0.06 P2P per agent provisioning)
- Sentinel plan — with leased nodes (your nodes, or rented from operators)
npm install @x402/fetch @x402/evm blue-js-sdk viemimport{x402Client,wrapFetchWithPayment}from'@x402/fetch';import{ExactEvmScheme}from'@x402/evm/exact/client';import{createWalletClient,http}from'viem';import{privateKeyToAccount}from'viem/accounts';import{base}from'viem/chains';import{createWallet,connect,disconnect}from'blue-js-sdk/ai-path';// 1. Sentinel wallet (one-time — persist the mnemonic)constwallet=awaitcreateWallet();// 2. x402 payment client backed by an EVM key with USDC on Baseconstaccount=privateKeyToAccount(process.env.EVM_KEY);constviemClient=createWalletClient({
account,chain: base,transport: http('https://mainnet.base.org'),});constscheme=newExactEvmScheme({address: account.address,signTypedData: (msg)=>viemClient.signTypedData(msg),});constclient=newx402Client();client.register('eip155:8453',scheme);constpaidFetch=wrapFetchWithPayment(fetch,client);// 3. Buy 30 days of VPN — 402 → auto-sign → settle → provisionconstres=awaitpaidFetch('https://x402.sentinel.co/vpn/connect/30days',{method: 'POST',headers: {'Content-Type': 'application/json'},body: JSON.stringify({sentinelAddr: wallet.address}),});constprovision=awaitres.json();// { subscriptionId, feeGranter, nodeAddress, nodes, expiresAt, ... }// 4. Connect — agent pays zero gas, operator fee-grants the sessionconstvpn=awaitconnect({mnemonic: wallet.mnemonic,nodeAddress: provision.nodeAddress,subscriptionId: String(provision.subscriptionId),feeGranter: provision.feeGranter,protocol: 'v2ray',// zero admin on Windows, binary auto-installs (~70% of nodes)});console.log(`VPN up: ${vpn.ip} via ${vpn.protocol}`);awaitdisconnect();| Method | Path | Price | Body |
|---|---|---|---|
| POST | /vpn/connect/1day | $0.033 | { sentinelAddr } |
| POST | /vpn/connect/7days | $0.233 | { sentinelAddr } |
| POST | /vpn/connect/30days | $1.00 | { sentinelAddr } |
Response after settlement:
{
"provisioned": true,
"subscriptionId": 1192288,
"planId": 42,
"feeGranter": "sent1...",
"nodeAddress": "sentnode1...",
"nodes": ["sentnode1a...", "sentnode1b...", "..."],
"sentinelTxHash": "...",
"expiresAt": "2026-05-14T18:50:48Z"
}| Method | Path | Description |
|---|---|---|
| GET | /pricing | Tier table, asset, payTo, network |
| GET | /nodes | Nodes in the operator's plan |
| GET | /health | Server uptime |
| GET | /agent/:sentinelAddr | Agent's subscription + fee-grant status |
| Property | Guarantee |
|---|---|
| Agent controls its session | Agent's Sentinel mnemonic signs MsgStartSession locally |
| Tunnel credentials stay with agent | WireGuard/V2Ray handshake is agent ↔ node |
| EVM key never leaves the agent | EIP-3009 signature created locally; facilitator only sees the signature |
| Self-hosted facilitator | No Coinbase, no third party in the payment path |
| Payment is verifiable | Every USDC settlement is a public Base transaction |
| No agent PII | Operator stores sentinelAddr only — no IPs, no traffic, no logs |
| Item | Approx. cost |
|---|---|
| EIP-3009 settlement on Base | ~$0.001 ETH |
| Sentinel provisioning TX (per agent) | ~$0.0001 in P2P |
| VPS for the server | $5–10/month |
# ─── Base / payments ───
OPERATOR_ADDRESS=0x... # Receives USDC payments
BASE_NETWORK=eip155:8453 # Or eip155:84532 for Sepolia
# ─── Facilitator (pick ONE) ───
FACILITATOR_PRIVATE_KEY=0x... # Self-hosted, needs ETH on Base
FACILITATOR_PORT=4021
# CDP_API_KEY_ID= # Or use Coinbase CDP
# CDP_API_KEY_SECRET=
# ─── Sentinel ───
SENTINEL_OPERATOR_MNEMONIC=word1 word2 ... # 12-word mnemonic, holds P2P
SENTINEL_PLAN_ID=42 # Plan with leased nodes
SENTINEL_RPC_URL=https://rpc.sentinel.co:443
SENTINEL_LCD_URL=https://lcd.sentinel.co
# ─── Server ───
PORT=4020
See server/.env.example for the full template.
MIT