x402

x402 is a community-built payments layer that lets AI agents pay USDC on Base or Solana for private VPN access through the Sentinel dVPN network of 900+ decentralized nodes. One function call: no KYC, no accounts, no P2P tokens. The agent pays USDC, connects to a VPN, and is private.

You can access x402 from:

• GitHub repository

info

This project is community-built and not officially maintained by the Sentinel team.

import { connect } from 'x402-connect';

const vpn = await connect({
  payment: { chain: 'base', walletKey: process.env.EVM_KEY, hours: 720 },
});

// vpn.connected = true
// vpn.ip = '45.152.243.12'
// vpn.country = 'Germany'

How It Works

Agent                           x402 Backend                    Sentinel Chain
-----                           ------------                    --------------

1. POST /register               Stores agentId <-> sent1...
   { sentinelAddr }             Returns agentId
                  │
2. contract.pay(agentId, hrs)   USDC -> our wallet
   on Base (or SPL+memo on Sol) Event emitted
                  │                     │
                  │              3. Sees event
                  │                 Resolves agentId -> sent1...
                  │                 MsgShareSubscription -----> Agent added to plan
                  │                 MsgGrantAllowance --------> Agent pays 0 gas
                  │
4. connect()                    Fee granted
   via blue-agent-connect          ----------------------------> MsgStartSession
                  │
5. Handshake directly with VPN node (we never see this)
                  │
6. VPN tunnel up. Agent is private.

Architecture

x402/
├── api/              - Backend (Express, port 3402)
│   ├── Registration  - POST /register -> agentId
│   ├── Base Watcher  - Watches VpnPayment events on Base
│   ├── Sol Watcher   - Helius webhook for Solana USDC transfers
│   ├── Sentinel TX   - MsgShareSubscription + MsgGrantAllowance
│   ├── Pool Manager  - Handles 8-allocation subscription limit
│   └── Retry Queue   - Exponential backoff for failed Sentinel TXs
│
├── contracts/base/   - Solidity payment contract (Base L2)
│   └── BlueVpnPayment.sol  - pay(agentId, hours) -> USDC + event
│
└── sdk/              - What agents install (x402-connect)
    ├── connect()     - One-liner: register -> pay -> poll -> VPN
    ├── Base payment  - Contract interaction via ethers
    └── Solana payment - SPL transfer + memo (no custom program)

Packages

Package	Description	Status
x402/api	Backend service: registration, event watching, Sentinel provisioning	Built, tested
x402/contracts/base	Solidity payment contract for Base L2	Built, 15/15 tests
x402/sdk	Agent-facing SDK: connect(), disconnect(), status()	Built, compiles

Chains

Chain	Payment Method	Status
Base	Smart contract (BlueVpnPayment.sol)	Ready to deploy
Solana	SPL USDC transfer + memo (no contract needed)	Code written

Quick Start

1. Deploy Contract (Base)

cd contracts/base
npm install
DEPLOYER_PRIVATE_KEY=0x... npx hardhat run scripts/deploy.ts --network base

2. Start Backend

cd api
cp .env.example .env
# Fill in: SENTINEL_OPERATOR_MNEMONIC, SENTINEL_PLAN_ID, PAYMENT_CONTRACT_ADDRESS
npm install
npm run dev

3. Agent Connects

import { connect } from 'x402-connect';

const vpn = await connect({
  payment: {
    chain: 'base',        // or 'solana'
    walletKey: '0x...',   // EVM private key (or Solana secret key for 'solana')
    hours: 720,           // 30 days
  },
  country: 'US',          // optional: preferred country
});

Security

Property	Guarantee
Agent controls its session	The agent's Sentinel key signs MsgStartSession.
Tunnel credentials stay with agent	Handshake is agent-to-node, signed by the agent's key.
We never see traffic	WireGuard / V2Ray is end-to-end encrypted.
We never see credentials	We only add the allocation and the fee grant.
Payment is verifiable	On-chain on Base or Solana. Anyone can audit.
No lock-in	The agent's Sentinel key works with any operator.

Costs

Item	Cost
Deploy contract (Base)	~$0.50
Each agent payment TX (Base)	~$0.01
Solana payment TX	~$0.001
VPS for backend	$5-10/month
Sentinel gas per agent	~$0.0001

Environment Variables

# Base
PAYMENT_CONTRACT_ADDRESS=       # After deployment
BASE_RPC_URL=https://mainnet.base.org
BASE_WS_URL=wss://mainnet.base.org

# Sentinel
SENTINEL_OPERATOR_MNEMONIC=     # NEVER commit
SENTINEL_PLAN_ID=
SENTINEL_RPC_URL=https://rpc.sentinel.co:443

# Solana (optional)
HELIUS_API_KEY=
HELIUS_WEBHOOK_SECRET=
OPERATOR_USDC_ATA=

# API
PORT=3402
PRICE_PER_HOUR_USDC=10000      # 0.01 USDC per hour