Design research in architecture has evolved significantly in the last three decades. This article traces a historical lineage of architectural design research in order to speculate on its contemporary trajectories. This article investigates two interrelated threads. The first provides an overview of significant moments in the history of architectural design research in the academic field in the UK and Western Europe, drawing from relevant literature. The second focuses on the 1995 book S,M,L,XL by OMA, Rem Koolhaas, and Bruce Mau, which coincided with the emergence of architectural design research discourse in academia. We demonstrate how the medium of this book contributed to a reorganisation of architectural design knowledge. Our article concludes by speculating on a similar paradigmatic turning point for design research that we are facing today. With the emergence of AI image generators and their expanding impact on architectural design, such as Midjourney and DALL-E, the field is confronted with a new horizon. If the birth of architectural design research was ushered in by a hypermediated format whose multiple narratives were co-constructed by the reader/viewer, then new media such as AI technologies signal a phase of post-mediation that challenges the authorship of the architect. The article ends by speculating on the role of architectural design research at a time when the very agency of the architect is challenged by such outside forces.