The management of urban water has evolved from single-function systems to more sustainable designs promoting society and nature as inputs to engineer novel infrastructure. In transdisciplinary research, co-design refers to a design-thinking strategy in which people jointly frame a problem–solution. This article presents a conceptual framework to assess a case study focusing on the process of co-design and implementation of green infrastructure as a prototype for urban stormwater management. The evaluation is carried out from a self-reflective post-implementation perspective. Research activities are translated into the framework to evaluate conditions shaping the trajectory of the prototype development. As a result, key aspects driving the transdisciplinary research regarding levels of stakeholder participation and dimensions of power are identified. Planning resilient co-design strategies to retrofit urban spaces is necessary to avoid unintended consequences, especially at initial experimental stages. This study aims to contribute to the continuous improvement of piloting strategies in urban spaces by providing a framework for a structured evaluation of transdisciplinary research experiences.