Static CSS Leakage in Microfrontends — Why Shadow DOM Fails and How postcss-prefix-selector Fixes It

This is a follow-up to MUI v4/v5 Style Conflicts in single-spa — A Complete Debug Record . The previous article covered dynamic style conflicts caused by MUI v4 JSS injecting style tags on mount and overriding the host app's Emotion styles. This article covers a different problem that surfaced right after: static CSS leakage. Both problems look the same on the surface — child app styles leaking into the host app — but the root causes are completely different, and so are the solutions. Discoverin