Replay Attack Prevention in Compact: Nonces, Nullifiers, and Domain Separation

On Ethereum, replay protection is built into the protocol. Every account has a nonce; every transaction carries it; the node rejects duplicates. You don't think about it. Midnight doesn't work that way. Transactions arrive as zero-knowledge proofs. The network verifies the proof is valid — but it doesn't inherently know whether that exact proof has been submitted before. The public ledger sees the result of a valid proof, not the transaction itself. That means replay prevention is your job, not