breaking: overhaul tsconfig by Rich-Harris · Pull Request #16458 · sveltejs/kit

Rich-Harris · 2026-07-21T14:59:30Z

Pairs with #16450.

The way we handle TypeScript configuration is a little bit messy, particularly as it regards service workers, which need to be in their own TypeScript project. This PR tidies things up a bit. It will need corresponding work to happen to the default project template. Essentially, a SvelteKit 3 project only needs this tsconfig.json file:

{
  "extends": "$app/tsconfig"
}

A service worker should live in a src/service-worker/index.ts file (not a src/service-worker.ts file, though this will still work) with a sibling tsconfig.json like this:

{
  "extends": "$app/tsconfig/service-worker"
}

You can add whatever other configuration you like there, though it's important that the first one "excludes" the service worker, and that both contain "types": ["$app/types"] if those options are overridden.

In addition to those two modules — which are 'real' modules in the sense that they live in node_modules/$app — we introduce a third, $app/service-worker, which exists solely to make it easier to get a correctly-typed self object (without this, there is a lot of annoying boilerplate):

import { self } from '$app/service-worker';

In future, we could also use this module for e.g. offline caching strategies and the like.

I've tested the node_modules/$app approach with pnpm and it seems like a winner. $ is an invalid character for an npm package but valid for Node's module resolution algorithm, so it works without danger of clobbering. pnpm doesn't nuke the directory when it installs or uninstalls packages (much like things like node_modules/.vite). We could extend this idea to other modules, which would help with this very longstanding issue.

TODO:

docs
validation of types and exclude
tidy up

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pkg-svelte-dev · 2026-07-21T14:59:33Z

Install the latest version of @sveltejs/kit from e74bfb3:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/e74bfb37eefbd5ae9dce4738a065ac1ba1836b07

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16458

changeset-bot · 2026-07-21T14:59:36Z

🦋 Changeset detected

Latest commit: e74bfb3

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

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svelte-docs-bot · 2026-07-21T19:50:07Z

Preview: https://svelte-dev-git-preview-kit-16458-svelte.vercel.app/

…-op `fetch` event listener as an import-time side effect for every consumer. This commit fixes the issue reported at packages/kit/src/runtime/app/service-worker/index.js:15 ## Bug The new `$app/service-worker` runtime module contained leftover WIP/debug code at module top level: ```js self.addEventListener('fetch', (e) => { e.respondWith; }); ``` The module's stated purpose is *solely* to expose a correctly-typed `self` (`export const self: ServiceWorkerGlobalScope`). The generated public types (`packages/kit/types/index.d.ts`) only declare `self` — there is no fetch-handling surface. ### Why it's a problem * **Import-time side effect:** Any module doing `import { self } from '$app/service-worker'` would register a real `fetch` event listener on the service worker global scope. Registering a fetch handler is semantically meaningful (it influences PWA install/behavior criteria and can shadow the network), so silently attaching one for every consumer is surprising and unintended. * **Dead expression:** `e.respondWith;` merely references the property and does nothing — it never calls `respondWith(...)`. This is the classic unused-expression that likely triggered the "pacify eslint" workaround rather than being intentional behavior. ### Trigger Any consumer importing the module registers the empty listener. The `e.respondWith;` statement is unconditionally dead. ## Fix Removed the entire `self.addEventListener('fetch', ...)` block, leaving only the typed `self` export and the DEV-time guard, which matches the module's documented single responsibility and the generated public types. Co-authored-by: Vercel <vercel[bot]@users.noreply.github.com> Co-authored-by: Rich-Harris <hello@rich-harris.dev>

Rich-Harris · 2026-07-23T20:36:07Z

I think the preview deployment will be broken until we release this and update svelte.dev

…to rethink-tsconfig

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

I think this looks good, just a few comments around cleanliness / naming

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.12 ### Major Changes - breaking: rename `Pathname` type to `Path` and `Asset` to `AssetPath` ([#16430](#16430)) breaking: remove leading `/` from `Path` and `AssetPath` - breaking: write tsconfig to `node_modules/$app/tsconfig` ([#16458](#16458)) - breaking: error on `event.url`, `event.params` and `event.route` access inside queries ([#16452](#16452)) - breaking: delete `$service-worker` module ([#16450](#16450)) - breaking: detect new deployments on data, remote, and form action responses, tab focus, and visibility change, and default `version.pollInterval` to 1 hour ([#16496](#16496)) ### Minor Changes - feat: add `$app/manifest` module with `immutable`, `assets`, `prerendered`, and `routes` exports ([#16372](#16372)) - feat: validate that all remote form fields were created with form.fields.foo.as(...) ([#16331](#16331)) - feat: make `$app/paths` importable in service workers ([#16441](#16441)) - feat: `$app/service-worker` module ([#16458](#16458)) - feat: better tsconfig validation ([#16458](#16458)) - fix: default cookies to `secure` to `false` during development ([#16462](#16462)) ### Patch Changes - fix: allow `undefined` values to be passed to form field `.as(...)` where applicable ([#15681](#15681)) - fix: include queries refreshed from within another query in the serialized response ([#16461](#16461)) - fix: generate sourcemaps for remote modules ([#16440](#16440)) - fix: avoid empty getElementById() call on hash routing navigation ([#16448](#16448)) - fix: warn if hook files are spelled as "hook" instead of "hooks" ([#16483](#16483)) - chore: deprecate the `alias` option ([#16470](#16470)) - fix: prevent infinite loops when server-side queries refresh each other in a cycle during the single-flight drain ([#16461](#16461)) - fix: populate `version` in service workers ([#16434](#16434)) - fix: resolve remote modules as external during dev prebundling so packages can re-export remote functions ([#16426](#16426)) - fix: refetch route-tracking server data when navigating away from an error page ([#16381](#16381)) - fix: serialize `query(...).set(...)`/`query(...).refresh()` values into the rendered HTML when called from within a query during SSR ([#16461](#16461)) - fix: fall back to the page's form actions when a sibling endpoint has no POST handler ([#16349](#16349)) - fix: return a lightweight 404 instead of rendering the error page for subresource requests ([#16463](#16463)) - fix: preserve stripped path prefixes by making trailing-slash redirects relative ([#16431](#16431)) - chore: deduplicate type-stripping logic in `tweak_types` ([#16454](#16454)) - fix: more informative error message when running a command inside a query or prerender function ([`eb5c973`](eb5c973)) ## @sveltejs/adapter-cloudflare@8.0.0-next.3 ### Patch Changes - chore: bump `@cloudflare/workers-types` to `4.20260621.1` ([#16455](#16455)) - Updated dependencies [[`adc4c5b`](adc4c5b), [`ecb0701`](ecb0701), [`4b4cc60`](4b4cc60), [`7390dbe`](7390dbe), [`2e71340`](2e71340), [`c87bc3a`](c87bc3a), [`af15c6c`](af15c6c), [`c6fa431`](c6fa431), [`bfe4dea`](bfe4dea), [`df7dc72`](df7dc72), [`5ae11a1`](5ae11a1), [`781205c`](781205c), [`c87bc3a`](c87bc3a), [`a1bfeb9`](a1bfeb9), [`c87bc3a`](c87bc3a), [`9f0127d`](9f0127d), [`4b4cc60`](4b4cc60), [`8f5b9c7`](8f5b9c7), [`c9b5544`](c9b5544), [`fe1d4a4`](fe1d4a4), [`4b4cc60`](4b4cc60), [`5f78e95`](5f78e95), [`25510fc`](25510fc), [`c99a6cf`](c99a6cf), [`17a45ca`](17a45ca), [`2ca20c3`](2ca20c3), [`eb5c973`](eb5c973)]: - @sveltejs/kit@3.0.0-next.12 ## @sveltejs/adapter-netlify@7.0.0-next.4 ### Patch Changes - fix: await `init` on every request to prevent race condition ([#16467](#16467)) - chore: bump Rolldown to `1.2.0` ([#16455](#16455)) - Updated dependencies [[`adc4c5b`](adc4c5b), [`ecb0701`](ecb0701), [`4b4cc60`](4b4cc60), [`7390dbe`](7390dbe), [`2e71340`](2e71340), [`c87bc3a`](c87bc3a), [`af15c6c`](af15c6c), [`c6fa431`](c6fa431), [`bfe4dea`](bfe4dea), [`df7dc72`](df7dc72), [`5ae11a1`](5ae11a1), [`781205c`](781205c), [`c87bc3a`](c87bc3a), [`a1bfeb9`](a1bfeb9), [`c87bc3a`](c87bc3a), [`9f0127d`](9f0127d), [`4b4cc60`](4b4cc60), [`8f5b9c7`](8f5b9c7), [`c9b5544`](c9b5544), [`fe1d4a4`](fe1d4a4), [`4b4cc60`](4b4cc60), [`5f78e95`](5f78e95), [`25510fc`](25510fc), [`c99a6cf`](c99a6cf), [`17a45ca`](17a45ca), [`2ca20c3`](2ca20c3), [`eb5c973`](eb5c973)]: - @sveltejs/kit@3.0.0-next.12 ## @sveltejs/adapter-node@6.0.0-next.6 ### Patch Changes - fix: preserve stripped path prefixes by making trailing-slash redirects relative ([#16431](#16431)) - chore: bump Rolldown to `1.2.0` ([#16455](#16455)) - Updated dependencies [[`adc4c5b`](adc4c5b), [`ecb0701`](ecb0701), [`4b4cc60`](4b4cc60), [`7390dbe`](7390dbe), [`2e71340`](2e71340), [`c87bc3a`](c87bc3a), [`af15c6c`](af15c6c), [`c6fa431`](c6fa431), [`bfe4dea`](bfe4dea), [`df7dc72`](df7dc72), [`5ae11a1`](5ae11a1), [`781205c`](781205c), [`c87bc3a`](c87bc3a), [`a1bfeb9`](a1bfeb9), [`c87bc3a`](c87bc3a), [`9f0127d`](9f0127d), [`4b4cc60`](4b4cc60), [`8f5b9c7`](8f5b9c7), [`c9b5544`](c9b5544), [`fe1d4a4`](fe1d4a4), [`4b4cc60`](4b4cc60), [`5f78e95`](5f78e95), [`25510fc`](25510fc), [`c99a6cf`](c99a6cf), [`17a45ca`](17a45ca), [`2ca20c3`](2ca20c3), [`eb5c973`](eb5c973)]: - @sveltejs/kit@3.0.0-next.12 ## @sveltejs/adapter-vercel@7.0.0-next.3 ### Patch Changes - fix: await `init` on every request to prevent race condition ([#16467](#16467)) - chore: bump Rolldown to `1.2.0` ([#16455](#16455)) - Updated dependencies [[`adc4c5b`](adc4c5b), [`ecb0701`](ecb0701), [`4b4cc60`](4b4cc60), [`7390dbe`](7390dbe), [`2e71340`](2e71340), [`c87bc3a`](c87bc3a), [`af15c6c`](af15c6c), [`c6fa431`](c6fa431), [`bfe4dea`](bfe4dea), [`df7dc72`](df7dc72), [`5ae11a1`](5ae11a1), [`781205c`](781205c), [`c87bc3a`](c87bc3a), [`a1bfeb9`](a1bfeb9), [`c87bc3a`](c87bc3a), [`9f0127d`](9f0127d), [`4b4cc60`](4b4cc60), [`8f5b9c7`](8f5b9c7), [`c9b5544`](c9b5544), [`fe1d4a4`](fe1d4a4), [`4b4cc60`](4b4cc60), [`5f78e95`](5f78e95), [`25510fc`](25510fc), [`c99a6cf`](c99a6cf), [`17a45ca`](17a45ca), [`2ca20c3`](2ca20c3), [`eb5c973`](eb5c973)]: - @sveltejs/kit@3.0.0-next.12 Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

breaking: overhaul tsconfig

30ae1c7

Rich-Harris added 6 commits July 21, 2026 11:40

WIP

7226b17

fix

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fix

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fix

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fix

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Rich-Harris added 3 commits July 21, 2026 15:54

fix

200a1b4

add $app/service-worker and $app/tsconfig/service-worker

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fix

864eba3

Rich-Harris mentioned this pull request Jul 22, 2026

breaking: stop generating ambient.d.ts #16460

Closed

pacify eslint

5448b91

This was referenced Jul 22, 2026

resolve.tsconfigPaths fallback conflicts with the generated tsconfig #16471

Open

Review TODOs and deprecated code #1247

Open

Rich-Harris added 13 commits July 22, 2026 16:49

WIP

d20ced2

WIP

52a091b

validation

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WIP

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move

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update tests

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WIP

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merge version-3

3df2c0f

tweak

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lint

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some docs

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docs

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fixes

b07be7c

Rich-Harris marked this pull request as ready for review July 23, 2026 20:17

vercel Bot reviewed Jul 23, 2026

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Comment thread packages/kit/src/runtime/app/service-worker/index.js Outdated

Rich-Harris and others added 4 commits July 23, 2026 16:24

fucking windows

a0da6b2

deprecate typescript.config option

1b80adb

changesets

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Merge branch 'rethink-tsconfig' of https://github.com/sveltejs/kit in…

7cbc234

…to rethink-tsconfig

Rich-Harris commented Jul 23, 2026

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Comment thread packages/kit/CHANGELOG.md Outdated

Rich-Harris and others added 4 commits July 23, 2026 16:41

Update packages/kit/CHANGELOG.md

8a4b4c8

fix

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Merge branch 'rethink-tsconfig' of https://github.com/sveltejs/kit in…

a0b82d1

…to rethink-tsconfig

fix playground

9a0fb38

elliott-with-the-longest-name-on-github approved these changes Jul 24, 2026

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Rich-Harris added 4 commits July 23, 2026 21:33

add comments/descriptions

831b534

attempt to explain regexes

b9a91ee

parent -> id

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inline docs

e74bfb3

Rich-Harris merged commit c87bc3a into version-3 Jul 24, 2026
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Rich-Harris deleted the rethink-tsconfig branch July 24, 2026 13:55

github-actions Bot mentioned this pull request Jul 24, 2026

Version Packages (next) #16435

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breaking: overhaul tsconfig#16458

breaking: overhaul tsconfig#16458
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