feat: Cloudflare Vite plugin integration by teemingc · Pull Request #15627 · sveltejs/kit

teemingc · 2026-03-31T17:22:05Z

closes #10496
closes #13692
closes #1712
closes #2963
closes #13300
closes #1519

This PR removes support for Cloudflare Pages and integrates with the Cloudflare Vite plugin. Users can now:

Use runtime APIs and bindings locally/remotely during build and preview.
Deploy apps unbundled by default (bundling is no longer required; saving a build artifact works again)
Write a custom worker entrypoint

TODOs

export a fetch handler for adapter-cloudflare
analysis in workerd
prerender in workerd
think about what tests are needed
split the PR up into removing Cloudflare Pages support and adding the Cloudflare Vite plugin

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This reverts commit eaffa39.

changeset-bot · 2026-03-31T17:22:10Z

🦋 Changeset detected

Latest commit: 8970286

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

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@sveltejs/adapter-cloudflare	Major

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svelte-docs-bot · 2026-03-31T17:22:38Z

Preview: https://svelte-dev-git-preview-kit-15627-svelte.vercel.app/

teemingc · 2026-05-19T09:21:53Z

+	await expect(page.locator('#var')).toHaveText(`Var: ${prod_string}VAR`);
+});
+
+test('serves static assets with assets path prefix', async ({ page, request }) => {


Not really sure how to get this test passing in the Cloudflare environment. Vite doesn't enforce consumers to allow us to run arbitrary code during preview so an alternative might be to have process.env.SVELTEKIT_ASSETS as an override which we set before anything else starts?

…1 (steps 1-3) Steps 1-3 of docs/jazz-to-cloudflare-migration.md: - Provision D1 + per-show ShowRoom and singleton ShowDirectory Durable Object bindings in wrangler.jsonc; generate binding types (pnpm cf:types). - Switch SvelteKit to @sveltejs/adapter-cloudflare. Because the released adapter (pre sveltejs/kit#15627) writes its worker to wrangler's `main`, a second config (wrangler.adapter.jsonc) drives the adapter's output while the real wrangler.jsonc `main` is src/worker.ts — a custom entry that imports the built SvelteKit worker, re-exports the Durable Objects, and wraps fetch with @sentry/cloudflare. - Port server Sentry to @sentry/cloudflare; delete instrumentation.server.ts and the adapter-node tracing/instrumentation settings. - Move Better Auth off jazzAdapter to a per-request createAuth(env) factory using the Drizzle / drizzle-orm/d1 adapter. Hand-authored D1 schema (auth tables + registry: shows/showHosts/hostLinks) with a partial unique index enforcing one live show. drizzle-kit migrations applied to local D1. - DEV_AUTH-gated dev-auth bypass (/dev-login) seeding an admin and a viewer, minting real JWKS-signed JWTs (verified: admin is_admin:true, viewer false). - Repoint auth:schema/db:reset; drop auth:validate. Add cf:types/db:* scripts. Deviations (documented): raw Durable Objects + WebSocket Hibernation API instead of PartyServer; wrangler dev against the build is the DO-capable runtime loop instead of @cloudflare/vite-plugin's vite dev, which cannot run a custom DO-exporting worker entry with the current SvelteKit adapter. Jazz data path goes dark mid-migration (single branch, no dual-path), restored on the new stack in steps 4-5. check/lint/build all green; app + auth verified under wrangler dev via Chrome DevTools. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Links the two live upstream tracks: sveltejs/kit#15627 (adapter-cloudflare adopting @cloudflare/vite-plugin) and the Durable Object / Workflow export gap in cloudflare/workers-sdk#14013. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

badreddinesaadioui · 2026-06-10T13:13:44Z

tested this PR against a real production app: SvelteKit + a Durable Object (voice agent) exported from the same Worker, WebSockets, Workers AI with remote: true bindings, R2, and a handful of +server.ts endpoints. Today we use @oselvar/sveltekit-add-worker-exports to work around #1712, so this PR is exactly what we've been waiting for. Sharing results in case real-world feedback is useful at this stage.

Setup: installed via pkg.pr.new/@sveltejs/kit@15627 and pkg.pr.new/@sveltejs/adapter-cloudflare@15627, with vite@8.0.16, svelte@5.56.3, @sveltejs/vite-plugin-svelte@7, @cloudflare/vite-plugin@1.x, Node 22. Custom entrypoint per the new docs: main pointing at our own src/worker/index.ts that does import { fetch } from '@sveltejs/adapter-cloudflare/worker', re-exports the DO class, and export default { fetch }.

Findings, in the order we hit them:

vite build fails during the analysis phase:
```
Cannot find module 'SERVER' imported from node_modules/.vite-analyse/deps_ssr/@sveltejs_adapter-cloudflare_worker.js
```
Same error reported above by another tester. Root cause appears to be that when the custom entrypoint imports @sveltejs/adapter-cloudflare/worker, Vite's dep optimizer pre-bundles that module, and the adapter's resolver for the virtual SERVER/MANIFEST ids never runs against the optimized copy. Adding optimizeDeps.exclude: ['@sveltejs/adapter-cloudflare/worker'] in user config (both top-level and ssr) did not help; the analysis server seems to spin up its own config. Maybe the adapter should exclude its own /worker subpath from dep optimization. This currently blocks the custom-entrypoint flow entirely, and since a DO class can only be exported from main, it blocks every Durable Object use case, which is the headline feature for us.
vite dev fails before that with:
```
The following environment options are incompatible with the Cloudflare Vite plugin:
	- "ssr" environment: `resolve.external`: ["@floating-ui/dom","@iconify/types"]
```
We never set resolve.external; vite-plugin-svelte auto-externalizes those (transitive deps of common Svelte UI libs, @iconify/svelte and svooltip in our case). So dev fails out of the box for apps using ordinary component libraries. Workaround: adding them to ssr.noExternal, after which we hit ReferenceError: exports is not defined from the runner, presumably a CJS dep now being executed raw in workerd. We stopped there.
pkce-challenge (transitive dep of Cloudflare's own agents SDK via the MCP SDK) fails to resolve in the worker build: its exports map only has browser and node conditions, no default, so the workerd-conditions resolve finds nothing. Worked around with a resolve.alias to its browser build. Probably an ecosystem problem rather than this PR's, but anyone building a voice/agents app on Workers will hit it immediately.
Minor setup friction worth documenting for testers: the preview kit imports rolldown at config-load time but doesn't ship it, so on a fresh install the build dies with ERR_MODULE_NOT_FOUND: rolldown until you install it manually. And with Vite 7 still installed (peer range is ^8.0.0, npm only warns with --legacy-peer-deps), the failure mode is a confusing Could not find file "src/routes/.../+server.ts" in Vite manifest for every endpoint rather than a version error.

Happy to re-test on this app as the PR evolves; it exercises pretty much everything at once (DO + WebSockets + remote AI bindings + custom entrypoint), so it's a decent canary.

closes #16361 This PR adds the Cloudflare Workers-specific condition `workerd` to the imports list in `package.json` so that Wrangler stops resolving to the `browser` condition which exposes client-side code. It's a quick fix that isn't needed if we land #15627 which simply removes the `browser` condition added by the Cloudflare Vite plugin for the build. Once we use Cloudflare's Vite plugin, the builds get deployed unbundled so we don't have to worry about Wrangler rebundling with the `browser` condition like we do now. --- ### 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 - [x] 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.

teemingc · 2026-07-30T19:11:08Z

Going to close this one until we can make better sense of the fetchable dev environment API in a way that doesn't make Kit worse for other platforms

Giggiux · 2026-07-31T10:51:24Z

Going to close this one until we can make better sense of the fetchable dev environment API in a way that doesn't make Kit worse for other platforms

@teemingc I kinda don't understand this decision. What are the limits of the current Vite plugin/or the feature that would be worse for the other platforms supporting this?
Other major meta-frameworks support this (Tanstack/Astro for sure; not sure about Next, as I haven't used it in years, but vinext exists).

I personally tested SvelteKit 3 with this, and the only issue I had was the SERVER/MANIFEST error I linked (#15627 (comment)).

I also understand that I am missing some context on new features / architectural decisions, but for a Vite-based meta framework, it seems odd that it cannot support a Vite Plugin.

I am sorry for the next phrase. I really hope this is not a decision stemming from the ongoing Vercel/Cloudflare feud.

teemingc · 2026-07-31T11:01:44Z

I also understand that I am missing some context on new features / architectural decisions, but for a Vite-based meta framework, it seems odd that it cannot support a Vite Plugin.

The main issue is that supporting Vite's FetchableDevEnvironment interface requires a major rework to the Kit codebase that unnecessarily complicates it and in some cases downgrades it for a use case that only supports Cloudflare. This negatively impacts every other platform (Node, Vercel, Netlify, Bun, etc.). It's also blocking a lot of other useful PRs because of the constant merge conflicts (we're trying to ship SvelteKit 3)

I am sorry for the next phrase. I really hope this is not a decision stemming from the ongoing Vercel/Cloudflare feud.

Not to worry, I'm not even paid by Vercel 😆; I'm supported by the Svelte open collective (in fact, I'm a happy Cloudflare user and have been using it to host church sites for a few years now). Also, we haven't given up yet. We're still thinking about the best way to do this that doesn't require such a massive change. Will report back soon if my findings are successful.

teemingc added 2 commits March 25, 2026 02:52

split cloudflare changes

eaffa39

Revert "split cloudflare changes"

32054c0

This reverts commit eaffa39.

teemingc added the pkg:adapter-cloudflare label Mar 31, 2026

teemingc added 2 commits April 1, 2026 04:58

Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

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wip

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This was referenced Apr 5, 2026

feat: Vite environment API #14008

Closed

feature request: vite plugin with sveltekit cloudflare/workers-sdk#8922

Closed

teemingc added 6 commits April 6, 2026 18:12

fix

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Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

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fix

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wip

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Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

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Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

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teemingc added 6 commits April 8, 2026 02:49

docs

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wip

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bump cloudflare plugin

f181570

fix style inlining in workerd

3edc662

format

192dfe6

migration docs

79d04d5

teemingc added the breaking change label Apr 13, 2026

teemingc added 2 commits April 15, 2026 01:42

wip

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i think its done now i just need to test

e1d7ea7

teemingc added 4 commits May 19, 2026 15:01

Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

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add paths.assets

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don't need service worker test

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bump

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teemingc commented May 19, 2026

View reviewed changes

teemingc added 4 commits May 19, 2026 17:28

Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

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changeset

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changeset

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Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

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teemingc linked an issue May 22, 2026 that may be closed by this pull request

adapter-cloudflare: wrangler.json vars not available via $env/dynamic/private during dev #15736

Open

teemingc added 3 commits May 25, 2026 03:20

Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

3062a74

Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

012a59a

Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

f99a1cf

teemingc added 2 commits May 29, 2026 02:44

Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

dbd7d03

Merge branch 'fetchable-dev-environment' into cloudflare-vite-plugin

8970286

basuke mentioned this pull request Jun 5, 2026

adapter-cloudflare on Vite 8 (Rolldown): worker fails to start with createRequire(import.meta.url) when a CJS dep uses a Node builtin #15960

Open

teemingc linked an issue Jun 6, 2026 that may be closed by this pull request

adapter-cloudflare on Vite 8 (Rolldown): worker fails to start with createRequire(import.meta.url) when a CJS dep uses a Node builtin #15960

Open

teemingc linked an issue Jun 15, 2026 that may be closed by this pull request

Add a boolean to mark prerenderable routes #14493

Open

penalosa mentioned this pull request Jul 8, 2026

Wrangler does not support email binding for sveltekit adapter cloudflare/workers-sdk#10996

Closed

teemingc mentioned this pull request Jul 15, 2026

fix: avoid resolving to client code when bundled with Wrangler #16364

Merged

6 tasks

teemingc linked an issue Jul 15, 2026 that may be closed by this pull request

redirect() throws "window is not defined" on non-browser servers (Cloudflare Workers): server bundle uses browser get_origin #16361

Closed

Nic-Polumeyv mentioned this pull request Jul 17, 2026

Cloudflare Worker Adapter - Durable Objects #1712

Open

teemingc closed this Jul 30, 2026

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