feat: custom server entry points during development by teemingc · Pull Request #16464 · sveltejs/kit

teemingc · 2026-07-21T22:07:07Z

split off from #15574

This PR moves dev manifest generation and server instantiation to their own modules away from the main Vite dev setup. Doing so provides a way for adapters to intercept the dev server instantiation by adding a Vite plugin which resolves the sveltekit:server-entry ID to its own server entry module. This allows us to reuse adapter or user server entrypoints during development so that it reflects the production build more closely. For example:

the static adapter can enable "prerendering" conditions that are normally only surfaced during build
the Node adapter can use the actual adapter handler code during both dev/production. We can also expose an option to specify the path of a custom server that can be used during development
it brings us one step closer to allowing a custom worker entrypoint for the Cloudflare adapter

The downside is that a good API for this hasn't been discussed beforehand, so there's probably room on the table to improving it rather than the current patching over existing APIs to get it working.

One idea was to pass an instantiated server to each handler rather than having to import the Server class and manifest from two different paths. My gut feeling is that it was originally designed that way to make generating split serverless functions easier as different manifests can be injected into each function entrypoint while reusing the same Server class import from the build output. If we do end up changing this, we'll have to refactor most of the existing adapter server handlers and that should be its own PR.

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pkg-svelte-dev · 2026-07-21T22:07:10Z

Install the latest version of @sveltejs/kit from 87d28df:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/87d28dfb71e7cc3ca8d69554b19a9ca40bb37024

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16464

changeset-bot · 2026-07-21T22:07:14Z

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svelte-docs-bot · 2026-07-21T22:09:12Z

Preview: https://svelte-dev-git-preview-kit-16464-svelte.vercel.app/

Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>

teemingc · 2026-07-23T17:55:40Z

 		const type = manifest.mimeTypes[file.slice(file.lastIndexOf('.'))];

-		return new Response(read_implementation(file), {
+		return new Response(read_implementation(__SVELTEKIT_DEV__ ? from_fs(file) : file), {


Movedfrom_fs out of the dev read implementation to here so that adapters don't have to repeat from_fs when providing a read implementation

Co-authored-by: Nic Polumeyv <nicolas.polum@outlook.com>

Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>

…16490) closes #11932 Makes sense to split this off from #16464 since it's a relatively simple change. Technically, this means we're 100% on the environment API, but everything still runs on Node.js only. Main benefit is that we have separate module graphs between the client and server now and one step closer to adopting other parts of the environment API (fetchable dev environments) --- ### Please don't delete this checklist! Before submitting the PR, please make sure you do the following: - [x] It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs - [x] This message body should clearly illustrate what problems it solves. - [ ] Ideally, include a test that fails without this PR but passes with it. ### Tests - [ ] Run the tests with `pnpm test` and lint the project with `pnpm lint` and `pnpm check` ### Changesets - [ ] If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running `pnpm changeset` and following the prompts. Changesets that add features should be `minor` and those that fix bugs should be `patch`. Please prefix changeset messages with `feat:`, `fix:`, or `chore:`. ### Edits - [x] Please ensure that 'Allow edits from maintainers' is checked. PRs without this option may be closed. --------- Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com> Co-authored-by: Vercel <vercel[bot]@users.noreply.github.com> Co-authored-by: Nic Polumeyv <nicolas.polum@outlook.com> Co-authored-by: Rich Harris <rich.harris@vercel.com>

…implementation is a bag of shite

into feat-server-entrypoint

teemingc added 4 commits July 22, 2026 03:47

get it working

277389a

fix remote import

9d8040f

replace ssrLoadModule and serialise assets path correctly

e97c6a1

ensure it works with vitest

0c78c0e

teemingc added 23 commits July 22, 2026 06:12

doc fix

0c19777

Merge branch 'version-3' into feat-server-entrypoint

ceaebc8

import only after server has started

3ff979b

Update index.js

f8245f3

Merge branch 'version-3' into feat-server-entrypoint

5e0e3f0

prettier

0ba765a

fix

9e0a2a9

format

8fc3473

standardise handler

fd47988

Merge branch 'version-3' into feat-server-entrypoint

4a3bae7

resolve to ssr entry correctly

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format

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doc fix

a4c64f9

Merge branch 'version-3' into feat-server-entrypoint

bcc1de7

fix trace facade not exporting fetch handler

88fb3fb

remove Vite fs prefix just before reading

dd97b18

avoid collision

35ac374

Update 99-writing-adapters.md

7391962

invalidate dev manifest data

0bd9813

Merge branch 'version-3' into feat-server-entrypoint

a2a5446

format

42eac09

windows

9b751f6

revert

b403f30

Merge branch 'runnable-dev-environment' into feat-server-entrypoint

8da087a

teemingc marked this pull request as ready for review July 23, 2026 17:40

missed this

b29f339

vercel Bot reviewed Jul 23, 2026

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Comment thread packages/kit/src/exports/vite/dev/server.js Outdated

Update packages/kit/src/exports/vite/dev/server.js

79b8d5f

Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>

teemingc commented Jul 23, 2026

View reviewed changes

teemingc and others added 7 commits July 24, 2026 01:57

add again

da976b8

Update packages/kit/src/exports/vite/dev/index.js

fc5d32f

Co-authored-by: Nic Polumeyv <nicolas.polum@outlook.com>

Update packages/kit/src/exports/vite/dev/index.js

9bfd903

Co-authored-by: Nic Polumeyv <nicolas.polum@outlook.com>

Merge branch 'version-3' into runnable-dev-environment

e2cafbe

merge runnable-dev-environment

1e548d7

DRY

28a0e73

Update packages/kit/src/exports/vite/dev/index.js

77883dc

Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>

Base automatically changed from runnable-dev-environment to version-3 July 24, 2026 14:14

Rich-Harris added 2 commits July 24, 2026 10:18

merge runnable-dev-environment

0dfd7e2

merge version-3. sure hope i did this right! github: your stacked PR …

676a9a7

…implementation is a bag of shite

vercel Bot reviewed Jul 24, 2026

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Comment thread packages/kit/src/exports/vite/index.js Outdated

teemingc added 3 commits July 25, 2026 00:13

Merge branch 'feat-server-entrypoint' of https://github.com/sveltejs/kit

f109f0f

into feat-server-entrypoint

remove merge conflict markers

391049c

remove manifest data virtual module

dbc8def

vercel Bot reviewed Jul 24, 2026

View reviewed changes

Comment thread packages/kit/src/exports/vite/index.js Outdated

teemingc added 8 commits July 25, 2026 01:27

didnt get them all the first try

71416d3

invalidate ssr manifest module

f2e57ad

no longer true

42e0ef8

vercel bot fix

7db1c35

only reload for $app/manifest

49c0556

not needed

36e2c21

clean up

c97be4d

not needed anymore

87d28df

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feat: custom server entry points during development#16464

feat: custom server entry points during development#16464
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Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

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teemingc commented Jul 21, 2026 •

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