Cannot use untrack in a .svelte.js or .svelte.ts file

[feus4177]

Describe the bug

Want to use explicit dependencies with $effect like demonstrated here. Since this will be used across the app, it would be nice to factor it out into a .svelte.js module. However, the untrack function does not seem to get added correctly to those files. As a result an error gets thrown:

ReferenceError: untrack is not defined
    at $effect (playground:output:3369:4)
    at update_reaction (playground:output:1917:57)
    at update_effect (playground:output:2043:19)
    at flush_queued_effects (playground:output:2152:7)
    at flush_queued_root_effects (playground:output:2131:5)
    at process_deferred (playground:output:2183:3)

Reproduction

https://svelte.dev/playground/f9fec2106b954d02b23e7f710aa62e80?version=5.16.0

Logs

No response

System Info

System:
    OS: macOS 15.2
    CPU: (10) arm64 Apple M1 Max
    Memory: 1.53 GB / 64.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.9.0 - /opt/homebrew/bin/node
    npm: 10.8.3 - /opt/homebrew/bin/npm
    pnpm: 9.5.0 - /opt/homebrew/bin/pnpm
  Browsers:
    Chrome: 131.0.6778.205
    Safari: 18.2
  npmPackages:
    svelte: ^5.11.1 => 5.11.1

Severity

blocking an upgrade

[Conduitry]

untrack isn't a global. https://svelte.dev/docs/svelte/svelte

[feus4177]

My apologies. I had looked at https://svelte.dev/docs/svelte/svelte#untrack and there was no import in the example so I just got confused.

[braebo]

Yea throwing the docs at @feus4177 as if everything they need to know is in there isn't entirely fair when this is literally the entire doc entry:

When used inside a $derived or $effect, any state read inside fn will not be treated as a dependency.

$effect(() => {
	// this will run when `data` changes, but not when `time` changes
	save(data, {
		timestamp: anytimestamp: untrack(() => time)
	});
});

Considering how often Svelte 5 code actually ends up looking like this:

import { untrack } from 'svelte'

let count = $state(0);

$effect(() => {
  count;
  untrack(() => {
    doStuff();
  });
});

untrack really should be covered in the $effect section of the docs, with a full example including the import.