Dutch-auction swap orders: a price that changes until someone fills

Evaluate the price at the fill time

Suppose a hypothetical order sells 100 A, initially requesting 102 B, with a linear decay to 99 B over 30 seconds. At 20 seconds, that curve requests 100 B. A fill at 100 B is consistent with the illustrative curve even though it is below the initial 102 B.

This is a teaching example, not a current UniswapX duration, parameter recommendation or claim that every auction uses linear decay.

A filler compares the obligation with execution cost

The filler needs to deliver the required output while obtaining the input, paying execution costs and handling its own trading strategy. Competition can encourage earlier execution, but a market move or lack of interest can leave an order unfilled.

The minimum and validity conditions are more useful protections than an expectation that someone will take the initial price.

Do not generalize across auction types

The retrieved overview explicitly describes chain-specific mechanisms. Identify the concrete order format before interpreting a curve. Record actual fill amounts and time when comparing outcomes; an initial auction amount is not the same kind of quote as a guaranteed exchange.