Prior research on professional boundary work emphasises the importance of subtle interactions among affected individuals when a new role is inserted into an established professional setting, which inevitably changes the prevalent division of labour. Thus, managers may set reflective spaces for professionals to collaboratively arrange their boundaries and make room for the new professional. This ethnomethodologically oriented study examines boundary arrangements in work development meetings in a university hospital, while professionals made room for a new role, a hospitalist. Examining professionals’ naturally occurring interactions in reflective spaces, the findings depict seven categorisations for the hospitalist. Elaborating on the dynamics of these categorisations, we propose that technically based categorisations sustain stability and context-bound categorisations allow change in work practices, whereas their combination enables transformation within the institutional context. Accordingly, the study adds to the literature on the transformative potential of reflective spaces by illuminating the intertwining of engaged professionals’ boundary talk-in-interaction with the consequences of configurational boundary work in relation to a new professional role.