fix(core): prevent SSR crash when head/body projected through a headless Slot#8668
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…ess Slot A headless component (renders only <Slot/>) that projects the document root gets a useOn placeholder <script> injected to anchor a document/window handler. When it wraps <head>/<body>, that placeholder landed as a direct child of <html> — invalid HTML that throws Code(Q12): SsrError(tag). It now defers into <head> via additionalHeadNodes. Mostly hit in dev, since HMR injects such a handler into every component.
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Varixo
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May 27, 2026
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Move $deferRootPlaceholder$ from the Container interface to the SSRContainer interface and cast at the call site (avoids an optional field on Container).
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What is it?
Description
SSR crashed with
Code(Q12): SsrError(tag)when<head>/<body>were projected through a headless component (e.g. a Provider that renders only<Slot/>, like a root context provider).Such a component gets a
useOnplaceholder<script>injected to anchor a document/window handler. When it wraps<head>/<body>, that placeholder ended up as a direct child of<html>— invalid HTML, which threw. It now defers into<head>, mirroring how$appendStyle$already routes root-level styles intoadditionalHeadNodesinstead of emitting them inline at the<html>frame.Mostly hit in dev, since HMR injects such a handler into every component — so any
<Slot/>-wrapped head/body broke even with nouseOnin app code.