Describe the bug

In SSR mode, when a dynamic component is rendered via a member expression (<a.b.c />) where a is a $derived, the compiler outputs a.b.c directly instead of a().b.c. Since server-side $derived returns a thunk (function) after #17674, a.b is undefined and accessing a.b.c throws TypeError: Cannot read properties of undefined (reading 'c').

The client compiler handles this correctly by emitting $.get(a).b.c.

Workaround

Capture each access in its own $derived:

<script>
  const platformIcons = $derived(icons);
  const Icon = $derived(platformIcons.currency.Icon);
</script>
<Icon />

That generates $.derived(() => platformIcons().currency.Icon), which works.

Reproduction

https://svelte.dev/playground/2fa2e050cfa44e94a3141dca53ce4ac2?version=latest

<script>
  let icons = $state({ currency: { Icon: () => 'x' } });
  const platformIcons = $derived(icons);
</script>

<platformIcons.currency.Icon />

Logs

System Info

System:
    OS: Linux 6.19 Fedora Linux 43 (KDE Plasma Desktop Edition)
    CPU: (12) x64 AMD Ryzen 5 7500F 6-Core Processor
    Memory: 14.92 GB / 31.05 GB
    Container: Yes
    Shell: 5.9 - /usr/bin/zsh
  Binaries:
    Node: 24.14.0 - /home/envyvox/.local/share/pnpm/node
    Yarn: 1.22.22 - /usr/local/bin/yarn
    npm: 11.9.0 - /home/envyvox/.local/share/pnpm/npm
    pnpm: 10.32.1 - /home/envyvox/.local/share/pnpm/pnpm
  Browsers:
    Firefox: 149.0.2
    Firefox Developer Edition: 149.0.2
  npmPackages:
    svelte: 5.55.5 => 5.55.5

Severity

annoyance