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perf: use a Set to check element ids when validating fragment links - #16494

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Nic-Polumeyv:prerender-hashlink-set
Jul 25, 2026
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perf: use a Set to check element ids when validating fragment links#16494
teemingc merged 1 commit into
sveltejs:version-3from
Nic-Polumeyv:prerender-hashlink-set

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@Nic-Polumeyv

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Prerendering validates each expected fragment link with hashlinks.includes(id) against the target page's array of element ids, which is O(A*L) for A ids and L inbound fragment links. Storing the crawled ids as a Set makes it O(A + L).

Cost for a page with N anchors and N inbound fragment links (Node 22):

N array includes Set (incl. construction)
1,000 21 ms 0.5 ms
4,000 123 ms 0.8 ms
8,000 616 ms 1.7 ms
16,000 1,591 ms 3.8 ms

This mainly benefits large heavily cross-linked prerendered sites such as generated API references.

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Install the latest version of @sveltejs/kit from c6ad266:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/c6ad266ec85bdecc00cc54db95c658bdf8458c17

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16494

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This PR is from a fork. A maintainer must approve approve each commit before it can be built and installed.

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changeset-bot Bot commented Jul 23, 2026

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🦋 Changeset detected

Latest commit: c6ad266

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

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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Thanks

@teemingc
teemingc merged commit 6850fa5 into sveltejs:version-3 Jul 25, 2026
17 of 18 checks passed
Rich-Harris pushed a commit that referenced this pull request Jul 29, 2026
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/adapter-vercel@7.0.0-next.4

### Major Changes

- breaking: remove support for edge and Node 20 runtimes
([#16520](#16520))

### Patch Changes

- chore: bump `@vercel/nft` dependency
([#16522](#16522))
- Updated dependencies
[[`6942ddb`](6942ddb),
[`68137d4`](68137d4),
[`15dc603`](15dc603),
[`a4f1521`](a4f1521),
[`629b45d`](629b45d),
[`7a7833a`](7a7833a),
[`e6591a0`](e6591a0),
[`7a7833a`](7a7833a),
[`b196a39`](b196a39),
[`66bf343`](66bf343),
[`4bde76b`](4bde76b),
[`d9f05cb`](d9f05cb),
[`40efca1`](40efca1),
[`8ef5548`](8ef5548),
[`9efb8f2`](9efb8f2),
[`6a670dc`](6a670dc),
[`3416dcc`](3416dcc),
[`6850fa5`](6850fa5),
[`e6591a0`](e6591a0),
[`688bead`](688bead),
[`b596610`](b596610),
[`0f26c13`](0f26c13),
[`110a3db`](110a3db),
[`665d467`](665d467),
[`9c8c60c`](9c8c60c)]:
  - @sveltejs/kit@3.0.0-next.13
## @sveltejs/kit@3.0.0-next.13

### Major Changes

- breaking: replace the `noScroll` and `keepFocus` options of `goto`
with a single `reset` option, and the `data-sveltekit-noscroll` and
`data-sveltekit-keepfocus` attributes with `data-sveltekit-reset`
([#16558](#16558))

- breaking: deprecate `error(status, {...})` in favour of `error(status,
message, {...})` ([#16540](#16540))

### Minor Changes

- feat: add shallow routing to `goto` and deprecate `pushState` and
`replaceState` ([#16449](#16449))

- feat: preserve page state set through `goto(..., { state,
persistState: true })` across reloads
([#16449](#16449))

### Patch Changes

- chore: deduplicate repeated CSP directive handling
([#16498](#16498))

- fix: avoid Vite dev server reload on initial page request
([#16553](#16553))

- fix: don't set a `null` `accept-language` header on internal `fetch`
sub-requests when the incoming request has none
([#16527](#16527))

- fix: correctly detect prerendered paths in server `fetch` when
`paths.base` is set
([#16525](#16525))

- fix: don't duplicate remote modules in the generated manifest
([#16532](#16532))

- fix: exclude inlined files from the page's `$app/manifest` immutable
list ([#16531](#16531))

- perf: avoid quadratic remote form issue merging
([#16493](#16493))

- fix: don't attempt to serialize fetch responses when the request body
is not a string or TypedArray
([#16501](#16501))

- fix: read the error status of `App.Error` in the `prerender` and
`query.live` remote functions
([#16529](#16529))

- fix: propagate errors from prerendered remote responses instead of
re-running the function
([#16535](#16535))

- fix: respect the status returned from `handleError` on the fallback
error page served to error-page sub-requests
([#16528](#16528))

- fix: skip unnecessary `version.json` checks if `updated.current` is
already `true` ([#16518](#16518))

- fix: allow generation of $app/tsconfig without TypeScript installed
([#16534](#16534))

- perf: use a `Set` to check element ids when validating fragment links
during prerendering
([#16494](#16494))

- fix: only include `_app/immutable` files in `$app/manifest`'s
`immutable` in the service worker
([#16531](#16531))

- fix: log errors caught by the Vite dev server handler
([#16550](#16550))

- fix: resolve `root` per instance of the SvelteKit Vite plugin
([#16513](#16513))

- fix: ignore path casing differences when warning about overridden Vite
config on Windows ([#16545](#16545))

- fix: preserve the current URL search parameters when submitting a
remote form without JavaScript
([#16373](#16373))

- fix: treeshake prerendered remote functions in the right chunks
([#16533](#16533))

- fix: error during development if the adapter does not support
instrumentation and it exists
([#16548](#16548))
## @sveltejs/adapter-netlify@7.0.0-next.5

### Patch Changes

- chore: replace @netlify/functions with @netlify/types for the Context
type ([#16542](#16542))
- Updated dependencies
[[`6942ddb`](6942ddb),
[`68137d4`](68137d4),
[`15dc603`](15dc603),
[`a4f1521`](a4f1521),
[`629b45d`](629b45d),
[`7a7833a`](7a7833a),
[`e6591a0`](e6591a0),
[`7a7833a`](7a7833a),
[`b196a39`](b196a39),
[`66bf343`](66bf343),
[`4bde76b`](4bde76b),
[`d9f05cb`](d9f05cb),
[`40efca1`](40efca1),
[`8ef5548`](8ef5548),
[`9efb8f2`](9efb8f2),
[`6a670dc`](6a670dc),
[`3416dcc`](3416dcc),
[`6850fa5`](6850fa5),
[`e6591a0`](e6591a0),
[`688bead`](688bead),
[`b596610`](b596610),
[`0f26c13`](0f26c13),
[`110a3db`](110a3db),
[`665d467`](665d467),
[`9c8c60c`](9c8c60c)]:
  - @sveltejs/kit@3.0.0-next.13
## @sveltejs/adapter-static@4.0.0-next.2

### Patch Changes

- fix: match adapter-vercel's prerendered redirect handling when
deploying to Vercel
([#16497](#16497))
- Updated dependencies
[[`6942ddb`](6942ddb),
[`68137d4`](68137d4),
[`15dc603`](15dc603),
[`a4f1521`](a4f1521),
[`629b45d`](629b45d),
[`7a7833a`](7a7833a),
[`e6591a0`](e6591a0),
[`7a7833a`](7a7833a),
[`b196a39`](b196a39),
[`66bf343`](66bf343),
[`4bde76b`](4bde76b),
[`d9f05cb`](d9f05cb),
[`40efca1`](40efca1),
[`8ef5548`](8ef5548),
[`9efb8f2`](9efb8f2),
[`6a670dc`](6a670dc),
[`3416dcc`](3416dcc),
[`6850fa5`](6850fa5),
[`e6591a0`](e6591a0),
[`688bead`](688bead),
[`b596610`](b596610),
[`0f26c13`](0f26c13),
[`110a3db`](110a3db),
[`665d467`](665d467),
[`9c8c60c`](9c8c60c)]:
  - @sveltejs/kit@3.0.0-next.13

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
@Nic-Polumeyv
Nic-Polumeyv deleted the prerender-hashlink-set branch July 30, 2026 22:54
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2 participants