Bug Report: Namespace import (`import * as X`) breaks hydration

[timootten]

Describe the bug

When importing for example Bits-UI components via a namespace import like:

import * as Sheet from '$lib/components/ui/sheet';

any attempt to render a component (for example Sheet.Root) causes SvelteKit to fail hydration. The component is treated as null, which leads to a hydration mismatch.

Using named imports fixes the issue:

import {
    Root as SheetRoot,
    Trigger as SheetTrigger,
    Content as SheetContent
} from '$lib/components/ui/sheet';

Expected behavior
Namespace imports should be fully supported and should not result in invalid component references.

Actual behavior
Components imported via import * as X are not recognized as valid Svelte components, causing hydration to break.

Reproduction

https://github.com/timootten/SvelteKit-Remotefunctions-BitsUI-Problem

Logs

(index):810 
 Failed to hydrate:  TypeError: Cannot read properties of null (reading 'nodeType')

    in <unknown>
    in +layout.svelte
    in root.svelte

    at _page (+page.svelte:7:25)

System Info

System:
    OS: Windows 11 10.0.26100
    CPU: (16) x64 AMD Ryzen 7 5700X 8-Core Processor
    Memory: 16.89 GB / 31.91 GB
  Binaries:
    Node: 22.20.0 - C:\Program Files\nodejs\node.EXE
    npm: 10.9.0 - C:\Program Files\nodejs\npm.CMD
    pnpm: 10.18.1 - C:\Users\timoo\AppData\Local\pnpm\pnpm.CMD
    bun: 1.3.1 - C:\Users\timoo\AppData\Local\pnpm\bun.CMD
    Deno: 2.3.3 - C:\Users\timoo\.deno\bin\deno.EXE
  Browsers:
    Chrome: 142.0.7444.136
    Edge: Chromium (140.0.3485.54)
    Firefox: 144.0.2 - C:\Program Files\Mozilla Firefox\firefox.exe
    Internet Explorer: 11.0.26100.1882
  npmPackages:
    svelte: 5.43.6 => 5.43.6

Severity

blocking an upgrade