[styled-engine] Prevent enableCssLayer styles from being overridden by unlayered styles#48603
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Janpot wants to merge 3 commits into
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[styled-engine] Prevent enableCssLayer styles from being overridden by unlayered styles#48603Janpot wants to merge 3 commits into
Janpot wants to merge 3 commits into
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Summary
This was showing up in the visual regression tests after #48575, depending on when the
injectFirstfixture runs.When
enableCssLayeris set,StyledEngineProviderwraps MUI's styles in@layer muibut keeps emotion's default cache keycss- the same key used by the default andinjectFirstcaches, which insert unlayered. Since the generated class name is${key}-${hash}, the same style produces the same class name in both the layered and the unlayered caches. An unlayered rule outranks every cascade layer, so whenever a style ends up inserted both unlayered (default /injectFirst) and layered, the unlayered copy silently overrides MUI's own layered style.