Modern knowledge work consists of both individual and highly collaborative activities that are typically composed of a number of configuration, coordination and articulation pro- cesses. The desktop interface today, however, provides very little support for these processes and rather forces knowl- edge workers to adapt to the technology. We introduce co- Activity Manager, an activity-centric desktop system that (i) provides tools for ad hoc dynamic configuration of a desk- top working context, (ii) supports both explicit and implicit articulation of ongoing work through a built-in collaboration manager and (iii) provides the means to coordinate and share working context with other users and devices. In this paper, we discuss the activity theory informed design of co-Activity Manager and report on a 14 day field deployment in a multi- disciplinary software development team. The study showed that the activity-centric workspace supports different individ- ual and collaborative work configuration practices and that activity-centric collaboration is a two-phase process consist- ing of an activity sharing and per-activity coordination phase.