The notion ‘smart city' has found a prominent place in urban visions, policies, planning, and infrastructure development, often promising citizens’ participation in shaping urban futures. This paper examines the frictions emerging between powerful Smart City Vienna policy imaginaries and their realization in real-world participatory experiments. Drawing on Responsible Research and Innovation (RRI) sensitivities, we highlight the challenges of giving voice to citizens and, in particular, the limits of participation in projectified (i.e. clearly temporalized) urban transformations. We not only observe the messiness, the unknowns, and uncertainties of participatory smartification processes but also the quite powerful infrastructuring of citizenry through these processes. This points to the need to design participatory processes able to respond to this open-endedness and processuality of temporalized urban transformation, always being attentive to who is experimenting with what and who can participate in shaping urban futures.