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fix: externalize @opentelemetry/api to prevent chunk colocation - #16302

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fix: externalize @opentelemetry/api to prevent chunk colocation#16302
elliott-with-the-longest-name-on-github merged 1 commit into
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elliott/externalize-opentelemetry-api

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@elliott-with-the-longest-name-on-github elliott-with-the-longest-name-on-github commented Jul 9, 2026 •
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closes #16288

When instrumentation.server.js and application code both import @opentelemetry/api, the bundler may colocate it into a shared chunk that also contains application modules. The compiled instrumentation entry then imports that chunk — evaluating application modules before Server.init() has called set_env(). Any module that reads $env/dynamic/private at module scope silently captures undefined.

This is a nastier variant of #14286: there the env modules are imported by instrumentation.server.ts itself; here instrumentation never touches $env — it merely imports @opentelemetry/api, and the chunking pulls in unrelated app modules.

What changed

  • Added @opentelemetry/api to ssr.external in the kit Vite plugin, so it stays as a bare import('@opentelemetry/api') in the build output rather than being bundled into a shared chunk.
  • Added @opentelemetry/api to adapter-node's external list (it's an optional peer dep, not in pkg.dependencies, so the existing regex wouldn't match it).

Why externalize?

  1. Prevents chunk colocation — no shared chunks between instrumentation and app code via this dep, so importing @opentelemetry/api from instrumentation can never cause app modules to evaluate.
  2. OTEL correctness — OpenTelemetry requires a single @opentelemetry/api module instance. The global tracer/propagation is set on that instance. Two bundled copies would mean instrumentation hooks are invisible to the SvelteKit runtime's tracer.

Other adapters don't need changes:

  • adapter-vercel serverless uses nodeFileTrace (copies deps, doesn't bundle) — the bare import resolves from node_modules.
  • adapter-vercel edge and adapter-netlify edge already bundle instrumentation as a separate single-file graph, and the edge bundler resolves the bare import into the bundle.
  • adapter-netlify serverless copies the kit server output directly via builder.writeServer.

@pkg-svelte-dev

pkg-svelte-dev Bot commented Jul 9, 2026 •
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Install the latest version of @sveltejs/kit from eb39e12:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/eb39e12d567c48aed1e937b353500dda83918a4e

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16302

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🦋 Changeset detected

Latest commit: eb39e12

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

This PR includes changesets to release 2 packages
Name Type
@sveltejs/kit Patch
@sveltejs/adapter-node Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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Preview: https://svelte-dev-git-preview-kit-16302-svelte.vercel.app/

@elliott-with-the-longest-name-on-github
elliott-with-the-longest-name-on-github force-pushed the elliott/externalize-opentelemetry-api branch 2 times, most recently from a436ecb to 2b5ae26 Compare July 9, 2026 20:44
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@elliott-with-the-longest-name-on-github elliott-with-the-longest-name-on-github linked an issue Jul 9, 2026 that may be closed by this pull request
instrumentation.server.js can evaluate app modules before Server.init() when the bundler colocates a shared dependency ($env/dynamic/private silently undefined) #16288
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@Rich-Harris

Rich-Harris commented Jul 10, 2026

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Is this just treating a symptom? Couldn't the same thing happen with any module that was imported by both instrumentation.server.ts and app code?

@elliott-with-the-longest-name-on-github

elliott-with-the-longest-name-on-github commented Jul 10, 2026

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You're correct. The only foolproof solution to this problem is externalizing all dependencies of instrumentation.server.ts to ensure they're not bundled with app code. In practice, though, tracing setup code other than @opentelemetry/api is very rarely something you're going to end up importing anywhere but your setup file.

Not sure what a better solution would look like...

@teemingc teemingc added this to the 3.0 milestone Jul 31, 2026
@Stadly Stadly mentioned this pull request Aug 5, 2026
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@elliott-with-the-longest-name-on-github
elliott-with-the-longest-name-on-github marked this pull request as ready for review August 10, 2026 14:51
@elliott-with-the-longest-name-on-github @teemingc
fix: externalize @opentelemetry/api to prevent chunk colocation
eb39e12 
When `instrumentation.server.js` and application code both import
`@opentelemetry/api`, the bundler may colocate it into a shared chunk
that also contains application modules. The compiled instrumentation
entry then imports that chunk — evaluating application modules before
`Server.init()` has called `set_env()`.

Externalizing `@opentelemetry/api` ensures:
- No shared chunks between instrumentation and app code (via this dep)
- A single module instance so OTEL hooks registered in instrumentation
  are visible to the SvelteKit runtime's tracer

Added to `ssr.external` in the kit Vite plugin and to adapter-node's
external list (since `@opentelemetry/api` is an optional peer dep, not
in `pkg.dependencies`, and wouldn't be matched by the existing regex).

Closes #16288
@teemingc
teemingc force-pushed the elliott/externalize-opentelemetry-api branch from fc13f64 to eb39e12 Compare August 10, 2026 18:34
@elliott-with-the-longest-name-on-github
elliott-with-the-longest-name-on-github merged commit 813726d into version-3 Aug 10, 2026
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@elliott-with-the-longest-name-on-github
elliott-with-the-longest-name-on-github deleted the elliott/externalize-opentelemetry-api branch August 10, 2026 19:24
@github-actions github-actions Bot mentioned this pull request Aug 10, 2026
Merged
teemingc added a commit that referenced this pull request Aug 11, 2026
@github-actions @teemingc
Version Packages (next) (#16714)
da52dc7 
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.19

### Major Changes

- breaking: move `defineParams` and associated types to
`@sveltejs/kit/params`
([#16716](#16716))

- breaking: run all errors through the `handleError` hook
([#16664](#16664))

- breaking: move `Page`, `ReadonlyURL` and `ReadonlyURLSearchParams`
from `@sveltejs/kit` to `$app/state`
([#16694](#16694))

- breaking: move `BeforeNavigate`, `OnNavigate`, `AfterNavigate`,
`Navigation`, `NavigationTarget`, `NavigationType`, `GotoOptions` and
the `Navigation*` variant types from `@sveltejs/kit` to
`$app/navigation` ([#16694](#16694))

- breaking: move `ActionResult` and `SubmitFunction` from
`@sveltejs/kit` to `$app/forms`
([#16694](#16694))

- breaking: remove `handleValidationError` and pass remote function
validation errors to `handleError` with `kind: 'validation'`
([#16672](#16672))

### Minor Changes

- feat: ignore files with + prefix if they contain test/spec/stories
([#16715](#16715))

### Patch Changes

- fix: rebuild the dev manifest when route files disappear during an
incremental update
([#16643](#16643))

- fix: externalize `@opentelemetry/api` to prevent bundler chunk
colocation between `instrumentation.server.js` and application code
([#16302](#16302))

- fix: surface prerender errors during development
([#16507](#16507))
## @sveltejs/adapter-node@6.0.0-next.9

### Patch Changes

- fix: externalize `@opentelemetry/api` to prevent bundler chunk
colocation between `instrumentation.server.js` and application code
([#16302](#16302))
- Updated dependencies
[[`04f9ab4`](04f9ab4),
[`1e198bd`](1e198bd),
[`813726d`](813726d),
[`a115a7b`](a115a7b),
[`031ac69`](031ac69),
[`dc7442c`](dc7442c),
[`19c4478`](19c4478),
[`dc7442c`](dc7442c),
[`dc7442c`](dc7442c),
[`0b3e2b3`](0b3e2b3)]:
  - @sveltejs/kit@3.0.0-next.19

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Tee Ming <chewteeming01@gmail.com>
@github-actions github-actions Bot mentioned this pull request Aug 11, 2026
Merged
teemingc pushed a commit that referenced this pull request Aug 11, 2026
@github-actions
Version Packages (next) (#16732)
83c6905 
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.19

### Major Changes

- breaking: move `defineParams` and associated types to
`@sveltejs/kit/params`
([#16716](#16716))

- breaking: run all errors through the `handleError` hook
([#16664](#16664))

- breaking: move `Page`, `ReadonlyURL` and `ReadonlyURLSearchParams`
from `@sveltejs/kit` to `$app/state`
([#16694](#16694))

- breaking: move `BeforeNavigate`, `OnNavigate`, `AfterNavigate`,
`Navigation`, `NavigationTarget`, `NavigationType`, `GotoOptions` and
the `Navigation*` variant types from `@sveltejs/kit` to
`$app/navigation` ([#16694](#16694))

- breaking: move `ActionResult` and `SubmitFunction` from
`@sveltejs/kit` to `$app/forms`
([#16694](#16694))

- breaking: remove `handleValidationError` and pass remote function
validation errors to `handleError` with `kind: 'validation'`
([#16672](#16672))

### Minor Changes

- feat: ignore files with + prefix if they contain test/spec/stories
([#16715](#16715))

### Patch Changes

- fix: rebuild the dev manifest when route files disappear during an
incremental update
([#16643](#16643))

- fix: externalize `@opentelemetry/api` to prevent bundler chunk
colocation between `instrumentation.server.js` and application code
([#16302](#16302))

- fix: surface prerender errors during development
([#16507](#16507))

- fix: adjust error overload for optional `App.Error` parameters
([#16725](#16725))
## @sveltejs/adapter-node@6.0.0-next.9

### Patch Changes

- fix: externalize `@opentelemetry/api` to prevent bundler chunk
colocation between `instrumentation.server.js` and application code
([#16302](#16302))
- Updated dependencies
[[`04f9ab4`](04f9ab4),
[`1e198bd`](1e198bd),
[`813726d`](813726d),
[`a115a7b`](a115a7b),
[`031ac69`](031ac69),
[`dc7442c`](dc7442c),
[`19c4478`](19c4478),
[`dc7442c`](dc7442c),
[`dc7442c`](dc7442c),
[`0b3e2b3`](0b3e2b3),
[`c5d0ce2`](c5d0ce2)]:
  - @sveltejs/kit@3.0.0-next.19

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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