Next.js CSS Chunking and Dynamic Import Bugs Cause Incorrect Asset Inclusion and Styling Loss

Developers using Next.js encounter two primary issues regarding CSS chunking and dynamic imports: first, Webpack's CssChunkingPlugin incorrectly merges and leaks async-only component CSS into initial route entry bundles (adding 50 KiB+ of render-blocking CSS); second, in the Pages Router, shared CSS between pages and next/dynamic components gets wiped out after client-side navigation due to a missing dynamic CSS manifest link during rendering.

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