Seaport is the settlement layer underneath the NFT market: an open marketplace protocol where every listing, offer, and collection bid is a signed order, and a single contract at the same address on every chain checks the signature, moves the assets, and pays everyone the order names.

Its design is the reason it became the default. An order is a list of what the offerer gives and what they must receive, so one primitive covers a fixed price listing, a declining auction, an offer on any token in a collection, and a bundle traded for a bundle. Orders live off chain until someone fills them, which makes listing free, and the contract enforces every term at the moment of settlement, which makes filling safe.

That same design leaves a seller holding liabilities they cannot see. Every signed order stays live until it fills, expires, or is cancelled, and the orders a wallet signed months ago on a marketplace it no longer opens are still valid instructions to sell at yesterday's price. When a collection moves, the stale listing is the first thing to fill, and by the time anyone notices, the asset is gone at a price nobody would sign today.

Seaport ships the remedy in the contract itself. Every order commits to its offerer's counter, and incrementing the counter voids everything signed before it in a single call, across every marketplace that settles through the protocol. The contract also publishes, for any order, whether it has been cancelled and how much of it has filled.

In a plug, that remedy becomes a standing rule instead of a panic. The account cancels every open order the moment a floor breaks a level, before assets leave the wallet, or on a schedule that keeps no offer alive past its window. A plan can wait on an order's status and move the proceeds the block it fills, or stop the instant it is cancelled.

Listings that never outlive the price they were signed at. A sale that triggers the next step on its own. A wallet whose open orders are a decision, not an accident.