This paper discusses Extreme Programming (XP), a relatively new and increasingly popular ‘user-centred’ software design approach. Extreme Programming proposes that collaborative software development should be centred on the practices of programming. That proposal contrasts strongly with more heavily instrumented, formalised and centrally managed software engineering methodologies. The paper maps the interactions of an Extreme Programming team involved in building a commercial organisational knowledge management system. Using ethnographic techniques, it analyses how this particular style of software development developed in a given locality, and how it uniquely hybridised documents, conversations, software tools and office layout in that locality. It examines some of the many artifices, devices, techniques and talk that come together as a complicated contemporary software system is produced. It argues that XP's emphasis on programming as the core activity and governing metaphor can only be understood in relation to competing overtly formal software engineering approaches and the organisational framing of software development. XP, it suggests, gains traction by re-embodying the habits of programming as a collective practice.