Trading at the midpoint
Cross has no order book, no spread and nothing to sandwich. Here is how a batch works.
An order book is a public record of intent. On a chain, it is also a public invitation: every resting order can be read, every pending fill can be jumped. Cross removes the book.
A price from outside
Cross does not discover prices. It takes them from the open market: at the moment a batch closes, the keeper asks Jupiter what selling one share pays and what buying one costs, and the batch crosses halfway between. Nobody inside the pool can move that number, so there is nothing to gain from seeing other people's orders and nothing to lose from not seeing them. The midpoint has no spread; a fill at the midpoint has no price impact.
Sealed until it is over
A batch runs for five minutes. During that window an order is a commitment: a hash of the market, the side, the size and a limit price, funded by one of your notes. Nothing about it is visible.
When the window ends the batch fixes its price. Then, for one minute, orders are revealed: each reveal is a proof that the funding note exists, belongs to the revealer, has not been spent, covers the order, and that the order's limit admits the price. The limit itself is never published. An order that is not revealed is simply cancelled. Because the price came from outside, that free cancel gives nobody an edge over the limit price they already set.
Settled as notes
Revealed orders whose limits admit the price are matched, pro rata on the heavier side. The fills are paid out as new notes in each participant's account. No token moves; the pool's public balance is unchanged, and the fill is invisible as a transfer. Opaque's keeper claims every settled order, so there is nothing for you to sign after the batch.
What the tape shows, per batch: the asset, the price, and the quantity that crossed. A revealed order shows a side and a size under a key used exactly once. Not who, not at what limit, not what else they hold.
Hours
xStocks trade around the clock, and so does Cross. Its price is whatever the open market says at the moment of closing, day or night. When the pair cannot be quoted, batches do not close and orders wait, which is the correct behaviour for a venue that refuses to guess a price.
The trade-off
Patience. A batch every five minutes, not a fill every second. For a position you intend to hold, that is a small price for a trade nobody can see coming.