Vue.js: Reactivity and Runtime Fixes

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Good morning, this is your Vue.js developer briefing for June 4th, 2026.

Today's activity centers on fixing edge cases that could break reactivity tracking and DOM rendering in production applications. The team addressed several specific scenarios where Vue's runtime behavior didn't match developer expectations.

The most significant fix targets reactivity with sealed objects. Pull request 14917 resolves an issue where calling `reactive` on a sealed object returned the raw target instead of a proxy, causing mutations on existing properties to go untracked. The core problem was an overly broad guard that rejected any non-extensible target, but sealed objects only lock structure, not values. This fix narrows the check to frozen objects specifically, restoring proper reactivity for sealed targets.

Runtime DOM handling also saw important corrections. PR 14915 fixes how literal template elements render their children - previously, child nodes were inserted directly onto the template element rather than into its content fragment, causing them to not display. Meanwhile, the Vapor runtime received fixes for custom element prop updates and async component handling, ensuring props and slots properly forward to loading components.

The watch API got attention for an immediate callback bug in PR 14914, where empty source arrays with the immediate flag weren't triggering their initial callback. This type of edge case can be particularly frustrating since it breaks expected behavior in testing and initialization code.

Two other areas saw targeted fixes: the template compiler now handles CDATA sections at document root without crashing, and documentation links were updated to reflect Vite's new domain.

What's next: These fixes target specific edge cases that likely affected real applications, so teams should consider updating to benefit from more reliable reactivity and rendering behavior.

That's your Vue.js briefing. Stay updated on the latest changes.