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fix: ensure version is defined when using $app/env with explicit env vars#15971

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Nic-Polumeyv:fix-app-env-version-define
Jun 7, 2026
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fix: ensure version is defined when using $app/env with explicit env vars#15971
teemingc merged 2 commits into
sveltejs:mainfrom
Nic-Polumeyv:fix-app-env-version-define

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@Nic-Polumeyv

@Nic-Polumeyv Nic-Polumeyv commented Jun 7, 2026 •
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When experimental.explicitEnvironmentVariables is enabled, $app/environment throws and apps import from $app/env instead. $app/env re-exports version from internal.js (export const version = __SVELTEKIT_APP_VERSION__), but unlike $app/environment it never references import.meta.hot, so Vite doesn't force its client to load. If $app/env is imported before the Vite client has loaded, version evaluates while the define is missing and the browser throws:

ReferenceError: __SVELTEKIT_APP_VERSION__ is not defined

This happens when $app/env is imported early, e.g. from hooks.client.js. Importing it from a route component is too late to hit it, since the client is already up by then, which is why it's intermittent. I ran into it in a real app after enabling experimental.explicitEnvironmentVariables.

It came in with #15934, which moved version onto the __SVELTEKIT_APP_VERSION__ define and added import.meta.hot to $app/environment, but not to the newly split $app/env.

The fix mirrors $app/environment. I left that file's import.meta.hot in place to keep this minimal, though it's now redundant with this one.

Added a regression test in options-2: an early $app/env import in hooks.client.js plus a load of the page. It fails on main (the app never finishes hydrating) and passes with this change.

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changeset-bot Bot commented Jun 7, 2026 •
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🦋 Changeset detected

Latest commit: 27717f0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package
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@sveltejs/kit Patch

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@Nic-Polumeyv

Nic-Polumeyv commented Jun 7, 2026

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The two failing jobs look unrelated to this change. test-kit (20) crashed at the Node level (Assertion failed: (req_wrap_async) != nullptr, exit 129) and test-kit (22) timed out on a remote-functions e2e test, while 18, 24 and all cross-browser runs pass. This PR only adds import.meta.hot to $app/env, so I don't think it's related, but happy to rebase or re-run if that helps.

@Nic-Polumeyv

Nic-Polumeyv commented Jun 7, 2026

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Added a regression test in options-2 and pinned the exact trigger: the error fires when $app/env is imported before the Vite client loads (e.g. from hooks.client.js); a route-component import is too late to hit it. Verified locally that the test fails on main and passes with this change. (Updating an earlier note of mine that said a deterministic test wasn't feasible, it is.)

@Nic-Polumeyv Nic-Polumeyv force-pushed the fix-app-env-version-define branch from 064bf30 to 1ed409d Compare June 7, 2026 03:31
@teemingc

teemingc commented Jun 7, 2026 •
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I wonder if a fix such as https://github.com/sveltejs/kit/pull/15574/changes#diff-a7244013c14e3925b24a2faf96dc33f01fae957ae2fa1a89a96fba3ee90be886R646 would be more fool proof. This isn’t the first time we’ve run into this issue and it could happen again depending on the order or presence of imported modules.

teemingc
teemingc approved these changes Jun 7, 2026
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Thanks!

@teemingc teemingc merged commit 17fadaa into sveltejs:main Jun 7, 2026
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@github-actions github-actions Bot mentioned this pull request Jun 7, 2026
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@Nic-Polumeyv Nic-Polumeyv deleted the fix-app-env-version-define branch June 7, 2026 18:03
@Nic-Polumeyv Nic-Polumeyv mentioned this pull request Jun 7, 2026
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@github-actions github-actions Bot mentioned this pull request Jun 7, 2026
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Rich-Harris pushed a commit that referenced this pull request Jun 8, 2026
@github-actions
Version Packages (#15962)
33dec0e 
This PR was opened by the [Changesets
release](https://github.com/changesets/action) GitHub action. When
you're ready to do a release, you can merge this and the packages will
be published to npm automatically. If you're not ready to do a release
yet, that's fine, whenever you add more changesets to main, this PR will
be updated.


# Releases
## @sveltejs/kit@2.63.1

### Patch Changes


- fix: use SSE for `query.live`
([#15957](#15957))


- fix: use forward slashes in the generated `env.d.ts` import path on
Windows ([#15977](#15977))


- fix: allow `$app/environment` with a warning when
`explicitEnvironmentVariables` is enabled
([#15980](#15980))


- fix: avoid importing Vite while validating explicit environment
variables ([#15953](#15953))


- docs: adjust the release version of explicit env vars
([#15968](#15968))


- fix: ensure `version` is defined when importing from `$app/env` with
explicit environment variables
([#15971](#15971))

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Rich-Harris pushed a commit that referenced this pull request Jun 8, 2026
@github-actions
Version Packages (next) (#15974)
806e658 
This PR was opened by the [Changesets
release](https://github.com/changesets/action) GitHub action. When
you're ready to do a release, you can merge this and the packages will
be published to npm automatically. If you're not ready to do a release
yet, that's fine, whenever you add more changesets to version-3, this PR
will be updated.

⚠️⚠️⚠️⚠️⚠️⚠️

`version-3` is currently in **pre mode** so this branch has prereleases
rather than normal releases. If you want to exit prereleases, run
`changeset pre exit` on `version-3`.

⚠️⚠️⚠️⚠️⚠️⚠️

# Releases
## @sveltejs/kit@3.0.0-next.2

### Patch Changes


- fix: use SSE for `query.live`
([#15957](#15957))


- fix: use forward slashes in the generated `env.d.ts` import path on
Windows ([#15977](#15977))


- fix: avoid importing Vite while validating explicit environment
variables ([#15953](#15953))


- docs: adjust the release version of explicit env vars
([#15968](#15968))


- fix: ensure `version` is defined when importing from `$app/env` with
explicit environment variables
([#15971](#15971))

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
@p-c-h-b p-c-h-b mentioned this pull request Jun 10, 2026
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