In this chapter, I consider the rise of urban AI through the lens of ambient computing, a form of computing in which monitoring devices are able to learn from, and inform, the conditions of their physical environments. I discuss the challenges to public spaces emerging from the rise of ambient computing, which enable private data ecosystems to become more closely integrated within the management of urban public spaces. Here, I am interested specifically in addressing how these developments implicate the ‘life between buildings,’ the civic spaces and the public realm of cities. Returning to Malcolm McCullough’s concept of the ‘ambient commons,’ I suggest, it provides a useful lens through which to defend the values of public spaces in an era of AI-driven ambient computing, and explore opportunities to better articulate and defend different forms of data value generated by citizens and other actors operating in public spaces.