With communities facing growing climate-induced risks, participatory decision-making processes become vital in shaping adaptive and resilient futures for the built environment. Recent advancements in large-language models point to a future in which AI agents may support collective decision-makingCollective decision-making—able to facilitate deliberation, represent absent voices, and interface with built environment data. This chapter specifically investigates how voice-based conversational agentsConversational agents can support collective decision-making in climate-adaptation planning. Through a speculative workshop in which participants debated rebuilding or relocating a flood-affected community in assigned roles, we used a Wizard-of-Oz prototype to examine how a conversational agent could mediate group interactions and support deliberation on spatial and ethical concerns. Our findings highlight both the potential and the challenges of integrating AI agents as a knowledge hub and co-facilitator in public deliberation. While participants valued the agent’s ability to broaden access to information and balance power dynamics, they also raised concerns around transparency, bias, and trust. The chapter contributes design insights and ethical considerations for embedding conversational agentsConversational agents into participatory planning processes, and discusses their potential future role as infrastructural components in climate-responsive human–building interaction.