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Free developer environment for building and testing AI agent payments. Runs on Base Sepolia with testnet USDC. No credit card. No real money.

What's included

src/mock-server.ts         x402-compatible API server (3 paid endpoints)
scripts/basic-payment.ts   create a wallet, make a payment, check balance
scripts/x402-flow.ts       full 402 challenge/response cycle
scripts/policy-enforcement.ts  spending caps, allowlists, per-tx limits
.env.example               sandbox API key + network config

Quickstart

git clone https://github.com/procohq/lab
cd lab
npm install
cp .env.example .env

Get a free sandbox key at procohq.com/sandbox and add it to .env:

PROCO_API_KEY=sk_sandbox_...
NETWORK=base-sepolia

The mock server

Start a local x402-compatible API server with three priced endpoints:

npm run server
# Listening on http://localhost:4402

Endpoint	Price	Description
GET /weather	$0.01	Weather data
GET /search	$0.05	Search results
POST /analyze	$0.50	AI analysis
GET /health	free	Health check

All endpoints follow the x402 protocol — return 402 Payment Required until a valid X-Payment header is supplied.

Test scripts

Basic payment flow

Creates an agent wallet, makes a payment, and checks the updated balance.

npm run basic

✓ Wallet created: wallet_abc123  (balance: 10.00 USDC)
✓ Payment sent: $1.00 USDC → api.example.com
✓ Balance updated: 9.00 USDC

Full x402 flow

Demonstrates the complete 402 challenge/response cycle — request → 402 → sign → retry → 200.

npm run x402

→ GET /weather
← 402  { amount: 0.01, currency: "USDC", network: "base-sepolia" }
→ POST /v1/payments/sign  (asking Proco to sign payment)
← signed payment proof
→ GET /weather  (X-Payment: <proof>)
← 200  { temp: 22, condition: "clear" }
✓ Payment settled: 0.01 USDC

Policy enforcement

Tests that spending controls are enforced before any transaction reaches the chain.

npm run policy

✓ Daily cap enforced      → PolicyViolationError: daily limit exceeded
✓ Vendor allowlist works  → PolicyViolationError: vendor not in allowlist
✓ Per-tx limit works      → PolicyViolationError: amount exceeds per-tx limit

How it works

The sandbox uses real x402 infrastructure on Base Sepolia — the same protocol as production, with testnet funds. Your agent wallet is created via the Proco API, funded automatically with testnet USDC, and can transact immediately.

Agent  →  GET /weather
Server  ←  402 + PaymentRequired { amount: $0.01, network: "base-sepolia" }
Agent  →  Proco  POST /v1/payments/sign
Proco  →  Agent  signed X-Payment proof
Agent  →  GET /weather + X-Payment: <proof>
Server  ←  200 + weather data

No wallets to create. No faucets to drain. No gas to manage.

Moving to production

When you're ready to go live, swap your sandbox key for a production key at procohq.com. Same API, same code, real USDC on Base mainnet.

- PROCO_API_KEY=sk_sandbox_...
+ PROCO_API_KEY=sk_live_...
- NETWORK=base-sepolia
+ NETWORK=base

Related

• procohq/pay — Proco pay: payment infrastructure, wallets, and policy enforcement
• coinbase/x402 — the x402 open standard
• procohq.com — production API + wallet dashboard

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procohq.com · MIT · Built by Proco