Throughout Shanghai’s treaty-port era, divergent understandings of the extraterritorial regime and the conflicts between the foreign community’s ‘natural and lawful’ pursuit of additional space and the Chinese rights recovery movement prevented clear demarcations between the city’s foreign settlements and the Chinese sphere. Instead, these controversies produced an expansive boundary zone in the form of extra-settlement roads (ESR), a contested and negotiated space where the projection of foreign power, the exercise of extraterritorial privileges, and the fabric of local Chinese lives were all conditioned by an array of quotidian elements such as public utilities, police protection, tax duties, and urban spatial characteristics. By the 1930s, developments in local, national, and imperial politics—such as the advent of the Guomindang regime, British accommodation of Chinese nationalism, and the dwindling authority of the Shanghai Municipal Council (SMC)—prompted discussions of formal joint Sino-foreign administration of ESR areas. However, this reconfiguration met with vehement resistance from the local Japanese community, which distrusted the British-controlled SMC yet relied on the treaty port’s existing administrative framework as a shield against Chinese threats. The ascendance of mass politics in the 1930s, via Chinese public outcries against imperial encroachment and Japanese settlers’ defence of their treaty rights, challenged the traditional paradigm of boundary-making and made ESR negotiations devolve into secret diplomacy that eventually reached a dead end. Examining ESR dynamics sheds new light on the intricate interplay of national sovereignty, colonial settlement, and imperial domination, while offering a fresh perspective on the shifting power landscapes in treaty-port Shanghai.