The 20th biennial conference of the International Planning History Society (IPHS) was held in Hong Kong, China. Through a comprehensive analysis of the keynote speeches, panel presentations, roundtable discussions, excursions and IPHS awards, this report highlights key insights from the conference that are especially relevant to urban historians. It suggests that planning history not only acts as a tool for informing urban strategies but also offers critical perspectives on socio-political, environmental, and cultural dimensions of urban transformation. The report presents three key insights for urban historians: (1) the entangled planning histories of Hong Kong and Shenzhen reflect broader political, ideological and international ambitions of dominant powers; (2) the evolution of environmental histories when rethinking human–natural relations in urban transition; and (3) the emerging attention to marginalized voices and alternative archives to enrich dominant planning narratives. These together demonstrate how planning history offers a critical historiographical lens for interpreting urban transformation.