Enhancing legitimacy and effectiveness of climate policy requires improved interactions between and within administrative levels, the latter including horizontal public–private coordination. In the heavily decentralized Swedish urban planning process, developer dialogues are used to enhance collaboration and thereby increase the climate-proofing of new housing districts. In practice, municipalities struggle with identifying what types of collaborative arrangements best support the realization of climate goals, in light of strong property developer interests and bargaining. Based on qualitative interviews with coordinating planners, this paper illustrates lessons from repeated collaborative practices in six Swedish municipalities. We analytically characterize a shift between first- and second-generation developer dialogues. In first-generation dialogues, coordinators attempted to ensure jointly agreed upon principles, priorities and commitments, which instead resulted in troublesome negotiations. In second-generation dialogues, coordinators used mixed approaches to ensure more competitive and climate-proof urban development by mechanisms of indirect command and control. Principles of collaborative interaction were abandoned to regain control over urban planning. This documented shift contrasts heavily with theoretical assumptions from the climate governance literature, where enhanced collaboration assumedly increase effectiveness of climate policy implementation. Acknowledging the practical implications of using developer dialogues to climate-proof urban planning in different settings is critical for improved policy implementation.