This article starts from the hypothesis that urban design and planning can contribute to a transition towards a more sustainable society, if it supports work and living environments to ‘collaborate’ in making a more sustainable future. It describes our research into how design (of e.g. space, services or technologies) currently enables and could enable this process of collaboration. The literature section discusses how work environments are increasingly disconnected from their surrounding living environments (e.g. because of global professional networks) and their role in giving form to sustainable cities. It articulates the importance of the activity of bringing the worlds of work and living together in collaborative city-making and defines it as “supermix coaching”. In the results section, we base ourselves on our fieldwork to explore this activity’s two main aspects: 1. gaining insight into the turning points (e.g. spatial growth of the company) in the interrelationship between living and working environments throughout history and 2. companies, policy and people living in the city taking more conscious collaborative actions in relation to those turning points (e.g. co-designing this growth with the neighbourhood). In the discussion, we address the importance of addressing these two aspects on different spatial scales: the starting point of this study, being the microscale (architectural space, technology and human actors); the mesoscale (the region and the city) and the macroscale (global context and contemporary trends).