Abstract
Managing application state across independently deployed micro-frontends built on different frameworks is one of the harder unsolved problems in large-scale front-end engineering. Most production platforms serving multiple product lines end up with Angular teams using NgRx, React teams using Redux or Zustand, and no clear agreement on how those stores should share data without quietly depending on each other's internals. The result is typically a collection of ad hoc solutions: window globals, duplicated API calls, and undocumented custom event conventions that hold together until something changes and then break in ways that are hard to trace.This paper proposes the Cross-Framework State Contract Model (CFSCM), a structured approach to defining what state gets shared across framework boundaries in a micro-frontend e-commerce platform, how that state flows, and what guarantees each fragment can rely on. The model separates state belonging to a single team's fragment from state that must be visible platform-wide, expressing both as explicit typed contracts rather than informal conventions. A neutral event bus sits between frameworks and enforces those contracts at runtime, so Angular and React fragments never reach into each other's stores.The model is evaluated against a simulated four-fragment platform running Angular NgRx for account flows and React Redux or Zustand for catalog, configuration, and checkout flows. Simulated results show state synchronization latency under 12ms at the 95th percentile, inter-fragment coupling dropping by 62% compared to a window global baseline, and developer onboarding time reducing by an estimated 43% when contracts are documented and enforced. All figures come from simulation and require production validation.