$derived reactivity breaks with "createSubscriber" after its teardown/destroy has been called at least once.

[jonbo]

Describe the bug

The reactivity of $derived seems to break in combination with createSubscriber after its teardown has been called once AND if the value it's watching is not being used elsewhere. Using instead a plain (reactive) function seems to work fine, however.

My apologies if this is intended behavior, and not a bug which it seems to me to be.

Reproduction

https://svelte.dev/playground/b451d2f033f94669a5ee60537e679fd5?version=5.28.2

Logs

System Info

5.28.2

Severity

annoyance

[PatrickG]

It works until svelte 5.19.4, starts failing with svelte 5.19.5.
Probably related to this PR.