The claim for a ‘more people-centred democracy’ poses the question of how collaborative planning can empower citizens to act for institutional change beyond government and markets. The planning of the Museumsquartier in Vienna and the Schlossplatz in Berlin showed the multi-facetted institutional contexts and diverse civic-political interactions involved in these contested cultural projects. To embed planning between power structures and civic agency, an interpretative-institutional approach understands the planner’s activity, field and institutional framework as situationally contingent, relational and open-ended. Diverse theoretical and practical alternatives to structural logics constitute collaboration as intersubjective knowledge practices that respond to concrete problems by interpretative interventions and reflective learning.