This essay explores the intersection of mechanism design in city planning and the concept of “designing disorder,” as proposed by Sendra and Sennett. Mechanisms are “transmission belts” meant to turn planning and policy intentions into tangible outcomes on the ground. Mechanism design, hence, involves crafting the frameworks of rules, incentives, organizational practices, interaction processes, and resource allocations but also the construction of shared meanings, the fostering of common knowledge, and the alignment of incentives to mobilize diverse actors and facilitate their coordination for collective action. However, what does it mean to design mechanisms that enable the kind of beneficial disorder advocated by Sendra and Sennett? And more generally, how does the concept of design square with the idea of disorder? Embracing disorder as a potentially positive force inevitably leads to Taleb’s concept of antifragility, which in the domain of spatial planning suggests a set of tools, principles, heuristics, and recommendations for policy and mechanism design. The contributions in this session present multifaceted explorations and examples of “designing for disorder”. By carefully considering the interplay between formal rules and informal practices, by prioritizing optionality and embracing a degree of controlled disorder, they provide examples of how we could conceptualize and design mechanisms to make an urban environment that is not only resilient but actually antifragile—capable, that is, to “prosper in disorder”.