In myriad areas of public life—from voting to professional licensure—the state collects, shares, and uses sex and gender data in complex algorithmic systems that mete out benefits, verify identity, and secure spaces. But in doing so, the state often erases transgender, nonbinary, and gender-nonconforming individuals, subjecting them to the harms of exclusion. These harms are not simply features of technology design, as others have ably written....