What is surplus, and who keeps it?

The short version: surplus is the gap between what you signed for and the better execution settlement achieved. It comes from price movement, solver competition, and peer matches. Ophis takes no cut of it on any chain: 100% is returned on the Ophis-operated chains, while CoW-hosted chains pass through CoW Protocol's upstream 50% share of quote improvement first. The fee is on volume, never on surplus.

What is surplus?

Surplus is execution beyond the terms you signed: your order named a limit, settlement achieved better, and the difference is surplus. On a sell order it means receiving more of the buy token than your floor required; on a buy order, spending less of the sell token than your cap allowed.

Where does surplus come from?

Three main places. Prices move between signing and settlement, and movement in your favor lands beyond your limit. Solvers compete, so a better route, a market-maker quote, or private inventory found by the winning solver shows up as execution above your floor. And a coincidence of wants inside the batch skips pool fees and price impact entirely, with the saving surfacing as surplus on both sides.

Who keeps the surplus?

Ophis takes no cut of price improvement on any chain. On Optimism, Unichain, and Robinhood Chain, 100% of the improvement is returned to the trader. On CoW-hosted chains, CoW Protocol retains 50% of quote improvement upstream before the remainder is returned. The Ophis fee is charged on volume, never as a share of your surplus.

How is surplus different from positive slippage?

Positive slippage is the tolerance-model cousin: price movement in your favor inside a router swap. Whether it reaches you depends on how the router handles it, and captured positive slippage has historically been a quiet revenue line in parts of the industry. Surplus in a batch auction is explicit by construction: the signed limit defines exactly where your terms end, so everything beyond it is measurable, attributable, and returned under published rules.

Can I see the surplus on my trades?

Yes. Every settlement is public, and the executed price against your signed limit is checkable on-chain per order. The Ophis explorer shows settlements, and the swap app surfaces the improvement on an order once it fills.

Go deeper

The full fee and all-in cost picture per chain is on the pricing page. Why a signed limit makes surplus measurable at all: slippage vs a signed limit price. Two of the three surplus sources in depth: what is a solver and what is a coincidence of wants.