The emergence of formal regional regimes characterized by precision and non-delegation signifies a major shift in the Asia-Pacific region. This special issue addresses the previously unexamined politics of institutional change towards formalization by analysing the policy realms of emergency liquidity provision, development aid, clean air, and labour immigration. To guide our research, this introductory article presents a conceptual framework that posits a novel argument: formalization is a result of competitive regime creation and flexible regime choice, fostering mutually beneficial regimes within a system of state sovereignty, and dispersed state capabilities lacking centralized coordinating authority. In such a context, multiple major states initiate regimes to secure order-setting privileges. Given the existence of multiple regimes, smaller states never commit themselves to a single regime; instead, they engage in forum shopping to select the regimes that best advance their preferences. Without third-party enforcement, these regimes are implementable only if they remain aligned with the evolving state preferences.