Modern knowledge work consists of both individual and highly collaborative activities that are typically composed of a number of configuration, coordination and articulation processes. The desktop interface today, however, provides very little support for these processes and rather forces knowledge 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 desktop 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 individual and collaborative work configuration practices and that activity-centric collaboration is a two-phase process consisting of an activity sharing and per-activity coordination phase.