Integrated urban megaprojects that attempt to (re-)develop parts of cities are complex affairs. The planners employed in them decide on large real estate, infrastructure and public space investments. The lengthy delivery trajectories of these projects undoubtedly result in emerging properties and changes in the social, political and spatial settings in which they are implemented. This ethnographic study focuses on the question how planners cope with this ambiguity in such non canonical practices. By immersion in the Amsterdam Zuidas urban megaproject for half a year, planners were observed in action. The ethnography reconstructs three episodes that represent typical interaction activities that they undertook to discuss progress of the project. The study shows how planners handle diverse types of ambiguity via different coping mechanism and reflects on the implications of these tactics for the project. It also discusses methods, potentials and pitfalls of ethnographic research in urban megaproject scholarship.