Pending boundary inside async component never mounts result #16921
Description
Describe the bug
An example as simple as this is broken in SvelteKit:
<script>
await Promise.resolve();
</script>
<svelte:boundary>
<div>Loaded</div>
{#snippet pending()}
Loading
{/snippet}
</svelte:boundary>The "Loaded" text never appears.
Reproduction
Logs
System Info
System:
OS: Linux 6.13 Fedora Linux 43 (Forty Three Prerelease)
CPU: (24) x64 AMD Ryzen 9 7900 12-Core Processor
Memory: 16.89 GB / 30.48 GB
Container: Yes
Shell: 4.0.2 - /bin/fish
Binaries:
Node: 22.19.0 - ~/.local/share/pnpm/node
npm: 10.9.3 - ~/.local/share/pnpm/npm
pnpm: 10.18.0 - ~/.local/share/pnpm/pnpm
bun: 1.2.20 - ~/.bun/bin/bun
Browsers:
Chrome: 141.0.7390.54
npmPackages:
@sveltejs/adapter-cloudflare: catalog: => 7.2.4
@sveltejs/kit: catalog: => 2.43.8
@sveltejs/vite-plugin-svelte: catalog: => 6.2.1
svelte: catalog: => 5.39.8
vite: catalog: => 7.1.9Severity
blocking an upgrade
Additional Information
No response