Over the past decade, state-led waterfront projects in the Gulf region have emerged as an intriguing urban phenomenon, repositioning World Heritage Sites (WHSs) located along coastal zones within large-scale urban development. In a region increasingly exposed to urban transformation and a hot-arid climate, these waterfront transformations also intersect with the emerging need for climate-adaptive urban resilience. While such projects are often framed as a means of contemporary extension of heritage assets, their implications for WHSs remain underexamined. This study investigates how state-led waterfront developments in the peripheries of the World Heritage Sites function as socio-spatial mediators that reconnect maritime heritage with these sites while enhancing or undermining urban resilience and climate adaptability. Drawing on comparative case studies from the Historic Jeddah (inscribed in 2014) and the Pearling Testimony of an Island Economy, Muharraq, Bahrain (inscribed in 2012), the data collection comprises literature synthesis, policy and planning documents, state-led waterfront proposals, and site observations, analyzed through the Comprehensive Waterfront Development Index (CWDI) framework. The analysis expands the existing six dimensions of the CWDI framework to eight dimensions and dissects two of the dimensions to a further two more. This expansion and dissection contextualize waterfront developments as socio-spatial mediators re-connecting maritime heritage with the WHSs. Findings reveal that while both cases integrate CWDI dimensions, social integration is limited, whereas climate adaptation remains absent, diminishing the urban resilience of the WHS. By doing so, this study contributes to broader debates on sustainable development and climate-adaptive urban resilience in rapidly transforming peripheries of WHSs.