Flying Money
Give a budget. Not your wallet. Let AI agents and people spend capped USDC at one seller: checked instantly, collected in batches on Arbitrum, and impossible to overspend.
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描述
Give a budget. Not your wallet.
To let Claude pay for an API today, you hand it a card or a hot wallet. One prompt injection or one leaked key, and everything is exposed. Flying Money replaces that with a budget: USDC locked on Arbitrum for one seller, one spending key, a maximum, an end date. A stolen key can't pay anyone else or spend past the limit. Enforced by the contract, not by the prompt.
Try it in 60 seconds: useflyingmoney.vercel.app/demo → Run it for real. An agent buys 20 API calls from a 0.30 USDC budget: 20 purchases, 3 Arbitrum transactions, each with an explorer link. Tick Steal the agent key and watch a thief get refused three ways: by the seller, by the contract, and by a different seller.
What's different
Sellers don't watch the chain. Payment channels let the payer withdraw after a delay, so the seller must monitor and react. A Flying Money budget can't be cancelled before its end date, so a seller that has checked it can serve instantly, even through an internet outage at the till, and collect later.
Agents ask; humans approve. With one message, an assistant (Claude, Cursor, any MCP client) sets itself up and requests a budget. The owner sees who asks, which seller, how much and for how long, then funds it from their own wallet. An agent can never approve or raise its own budget.
One budget, two worlds. The same contract pays an API per request over HTTP 402, and a café by QR code at the counter. The customer needs no crypto wallet and pays no fees.
Why Arbitrum: purchases happen off-chain as signed slips, and only collection touches the chain. Batches are cheap: collecting 10 slips costs about 328k gas. Arbitrum's low fees make micro-payments from API calls, allowances and café tabs economical to settle.
What's built (open source, MIT)
FlyingMoney.sol, verified on Arbitrum Sepolia: 0xb9ae3158f9cA841d9Da3C3725014D8352ca967F2. No owner, admin, pause, fee or upgrade path. Seven invariants are tested by fuzzing in Foundry.
TypeScript SDK with a crash-safe outbox (a retry never charges twice), seller middleware, and an MCP server with six tools.
Account app (requests inbox, approvals, budgets, collection), a phone wallet and an offline-capable shop till.
Business: the protocol is free and open. The plan is a hosted service for sellers (payment records, collection, recovery), starting with paid API and data sellers whose customers are agents, then pilots with known shops.