From d10cb7de83b1399f932eab067827c033278bf00e Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 23 May 2022 21:56:01 -0400
Subject: [PATCH 01/13] put build inside _app/build directory

---
 packages/kit/src/core/build/build_client.js         |  6 ++++--
 packages/kit/src/core/build/build_server.js         |  2 +-
 packages/kit/src/core/build/build_service_worker.js |  2 +-
 packages/kit/src/core/build/index.js                |  6 +++---
 packages/kit/src/core/preview/index.js              |  8 ++++++--
 packages/kit/test/apps/basics/test/test.js          | 10 ++++++++++
 6 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/packages/kit/src/core/build/build_client.js b/packages/kit/src/core/build/build_client.js
index 1e7f23bc8cd5..17e602dd7d02 100644
--- a/packages/kit/src/core/build/build_client.js
+++ b/packages/kit/src/core/build/build_client.js
@@ -59,7 +59,7 @@ export async function build_client({
 		build: {
 			cssCodeSplit: true,
 			manifest: true,
-			outDir: client_out_dir,
+			outDir: `${client_out_dir}/build`,
 			polyfillDynamicImport: false,
 			rollupOptions: {
 				input,
@@ -95,7 +95,9 @@ export async function build_client({
 	const { chunks, assets } = await create_build(merged_config);
 
 	/** @type {import('vite').Manifest} */
-	const vite_manifest = JSON.parse(fs.readFileSync(`${client_out_dir}/manifest.json`, 'utf-8'));
+	const vite_manifest = JSON.parse(
+		fs.readFileSync(`${client_out_dir}/build/manifest.json`, 'utf-8')
+	);
 
 	const entry = posixify(client_entry_file);
 	const entry_js = new Set();
diff --git a/packages/kit/src/core/build/build_server.js b/packages/kit/src/core/build/build_server.js
index 289abecf0cf2..97447465ac03 100644
--- a/packages/kit/src/core/build/build_server.js
+++ b/packages/kit/src/core/build/build_server.js
@@ -69,7 +69,7 @@ export class Server {
 			manifest,
 			method_override: ${s(config.kit.methodOverride)},
 			paths: { base, assets },
-			prefix: assets + '/${config.kit.appDir}/',
+			prefix: assets + '/${config.kit.appDir}/build/',
 			prerender: {
 				default: ${config.kit.prerender.default},
 				enabled: ${config.kit.prerender.enabled}
diff --git a/packages/kit/src/core/build/build_service_worker.js b/packages/kit/src/core/build/build_service_worker.js
index e193242d665d..924ea08ae3e1 100644
--- a/packages/kit/src/core/build/build_service_worker.js
+++ b/packages/kit/src/core/build/build_service_worker.js
@@ -44,7 +44,7 @@ export async function build_service_worker(
 
 			export const build = [
 				${Array.from(build)
-					.map((file) => `${s(`${config.kit.paths.base}/${config.kit.appDir}/${file}`)}`)
+					.map((file) => `${s(`${config.kit.paths.base}/${config.kit.appDir}/build/${file}`)}`)
 					.join(',\n\t\t\t\t')}
 			];
 
diff --git a/packages/kit/src/core/build/index.js b/packages/kit/src/core/build/index.js
index 61def523cc7f..008cbd7a0475 100644
--- a/packages/kit/src/core/build/index.js
+++ b/packages/kit/src/core/build/index.js
@@ -34,7 +34,7 @@ export async function build(config, { log }) {
 		// during `svelte-kit preview`, because we use a local asset path. If Vite
 		// used relative paths, I _think_ this could get fixed. Issue here:
 		// https://github.com/vitejs/vite/issues/2009
-		assets_base: `${config.kit.paths.assets || config.kit.paths.base}/${config.kit.appDir}/`,
+		assets_base: `${config.kit.paths.assets || config.kit.paths.base}/${config.kit.appDir}/build/`,
 		manifest_data,
 		output_dir,
 		client_entry_file: path.relative(cwd, `${get_runtime_path(config)}/client/start.js`),
@@ -65,8 +65,8 @@ export async function build(config, { log }) {
 
 	const files = new Set([
 		...static_files,
-		...client.chunks.map((chunk) => `${config.kit.appDir}/${chunk.fileName}`),
-		...client.assets.map((chunk) => `${config.kit.appDir}/${chunk.fileName}`)
+		...client.chunks.map((chunk) => `${config.kit.appDir}/build/${chunk.fileName}`),
+		...client.assets.map((chunk) => `${config.kit.appDir}/build/${chunk.fileName}`)
 	]);
 
 	// TODO is this right?
diff --git a/packages/kit/src/core/preview/index.js b/packages/kit/src/core/preview/index.js
index b931202f18df..f258942fc51a 100644
--- a/packages/kit/src/core/preview/index.js
+++ b/packages/kit/src/core/preview/index.js
@@ -66,8 +66,12 @@ export async function preview({ port, host, config, https: use_https = false })
 		scoped(
 			assets,
 			sirv(join(config.kit.outDir, 'output/client'), {
-				maxAge: 31536000,
-				immutable: true
+				setHeaders: (res, pathname) => {
+					// only apply to build directory, not e.g. version.json
+					if (pathname.startsWith(`/${config.kit.appDir}/build`)) {
+						res.setHeader('cache-control', 'public,max-age=31536000,immutable');
+					}
+				}
 			})
 		),
 
diff --git a/packages/kit/test/apps/basics/test/test.js b/packages/kit/test/apps/basics/test/test.js
index ab76155f9833..b56b99cd7e83 100644
--- a/packages/kit/test/apps/basics/test/test.js
+++ b/packages/kit/test/apps/basics/test/test.js
@@ -2636,3 +2636,13 @@ test.describe.parallel('XSS', () => {
 		);
 	});
 });
+
+test.describe.parallel('Version', () => {
+	test('does not serve version.json with an immutable cache header', async ({ request }) => {
+		// this isn't actually a great test, because caching behaviour is down to adapters.
+		// but it's better than nothing
+		const response = await request.get('/_app/version.json');
+		const headers = response.headers();
+		expect(headers['cache-control'] || '').not.toContain('immutable');
+	});
+});

From 93ce1d37571be786383a6349cd59c47f3ce6633e Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 23 May 2022 22:02:32 -0400
Subject: [PATCH 02/13] use free variable for native fetch

---
 packages/kit/src/runtime/client/client.js  | 10 +++++-----
 packages/kit/src/runtime/client/fetcher.js |  9 +++++----
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/packages/kit/src/runtime/client/client.js b/packages/kit/src/runtime/client/client.js
index 9b8658f69492..c535ae42768c 100644
--- a/packages/kit/src/runtime/client/client.js
+++ b/packages/kit/src/runtime/client/client.js
@@ -11,7 +11,7 @@ import {
 	notifiable_store,
 	scroll_state
 } from './utils.js';
-import * as fetcher from './fetcher.js';
+import { increment, decrement, initial_fetch, native_fetch } from './fetcher.js';
 import { parse } from './parse.js';
 
 import Root from '__GENERATED__/root.svelte';
@@ -594,7 +594,7 @@ export function create_client({ target, session, base, trailing_slash }) {
 					add_dependency(normalized);
 
 					// prerendered pages may be served from any origin, so `initial_fetch` urls shouldn't be normalized
-					return started ? fetcher.native(normalized, init) : fetcher.initial(requested, init);
+					return started ? native_fetch(normalized, init) : initial_fetch(requested, init);
 				},
 				status: status ?? null,
 				error: error ?? null
@@ -613,10 +613,10 @@ export function create_client({ target, session, base, trailing_slash }) {
 
 			if (import.meta.env.DEV) {
 				try {
-					fetcher.increment();
+					increment();
 					loaded = await module.load.call(null, load_input);
 				} finally {
-					fetcher.decrement();
+					decrement();
 				}
 			} else {
 				loaded = await module.load.call(null, load_input);
@@ -704,7 +704,7 @@ export function create_client({ target, session, base, trailing_slash }) {
 					const is_shadow_page = has_shadow && i === a.length - 1;
 
 					if (is_shadow_page) {
-						const res = await fetcher.native(
+						const res = await native_fetch(
 							`${url.pathname}${url.pathname.endsWith('/') ? '' : '/'}__data.json${url.search}`,
 							{
 								headers: {
diff --git a/packages/kit/src/runtime/client/fetcher.js b/packages/kit/src/runtime/client/fetcher.js
index 05605964fb1d..9c5d2375a70a 100644
--- a/packages/kit/src/runtime/client/fetcher.js
+++ b/packages/kit/src/runtime/client/fetcher.js
@@ -2,7 +2,7 @@ import { hash } from '../hash.js';
 
 let loading = 0;
 
-export const native = window.fetch;
+export const native_fetch = window.fetch;
 
 export function increment() {
 	loading += 1;
@@ -32,7 +32,8 @@ if (import.meta.env.DEV) {
 				`Loading ${url} using \`window.fetch\`. For best results, use the \`fetch\` that is passed to your \`load\` function: https://kit.svelte.dev/docs/loading#input-fetch`
 			);
 		}
-		return native(input, init);
+
+		return native_fetch(input, init);
 	};
 }
 
@@ -40,7 +41,7 @@ if (import.meta.env.DEV) {
  * @param {RequestInfo} resource
  * @param {RequestInit} [opts]
  */
-export function initial(resource, opts) {
+export function initial_fetch(resource, opts) {
 	const url = JSON.stringify(typeof resource === 'string' ? resource : resource.url);
 
 	let selector = `script[sveltekit\\:data-type="data"][sveltekit\\:data-url=${url}]`;
@@ -55,5 +56,5 @@ export function initial(resource, opts) {
 		return Promise.resolve(new Response(body, init));
 	}
 
-	return native(resource, opts);
+	return native_fetch(resource, opts);
 }

From 6a30552372dd401fb9b96467c79cae5b6c32637c Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 23 May 2022 22:08:50 -0400
Subject: [PATCH 03/13] update test

---
 packages/kit/test/apps/basics/test/test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/kit/test/apps/basics/test/test.js b/packages/kit/test/apps/basics/test/test.js
index b56b99cd7e83..6a25d2e767c3 100644
--- a/packages/kit/test/apps/basics/test/test.js
+++ b/packages/kit/test/apps/basics/test/test.js
@@ -347,7 +347,7 @@ test.describe.parallel('Imports', () => {
 			]);
 		} else {
 			expect(sources[0].startsWith('data:image/png;base64,')).toBeTruthy();
-			expect(sources[1]).toBe(`${baseURL}/_app/assets/large-3183867c.jpg`);
+			expect(sources[1]).toBe(`${baseURL}/_app/build/assets/large-3183867c.jpg`);
 		}
 	});
 });

From f28d823d5ebfb27c02438285500f4464fac90593 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 23 May 2022 22:18:56 -0400
Subject: [PATCH 04/13] only serve _app/build with immutable cache header, not
 _app/version.json - fixes #4837

---
 .changeset/wise-berries-flash.md              | 10 ++++++++
 .../adapter-cloudflare-workers/files/entry.js |  2 +-
 packages/adapter-cloudflare/src/worker.js     |  2 +-
 packages/adapter-netlify/src/edge.js          |  3 ++-
 packages/adapter-node/src/handler.js          | 23 +++++++++++--------
 packages/adapter-vercel/index.js              |  2 +-
 6 files changed, 29 insertions(+), 13 deletions(-)
 create mode 100644 .changeset/wise-berries-flash.md

diff --git a/.changeset/wise-berries-flash.md b/.changeset/wise-berries-flash.md
new file mode 100644
index 000000000000..0e72e7394437
--- /dev/null
+++ b/.changeset/wise-berries-flash.md
@@ -0,0 +1,10 @@
+---
+'@sveltejs/adapter-cloudflare': patch
+'@sveltejs/adapter-cloudflare-workers': patch
+'@sveltejs/adapter-netlify': patch
+'@sveltejs/adapter-node': patch
+'@sveltejs/adapter-vercel': patch
+'@sveltejs/kit': patch
+---
+
+only serve \_app/build with immutable cache header, not \_app/version.json
diff --git a/packages/adapter-cloudflare-workers/files/entry.js b/packages/adapter-cloudflare-workers/files/entry.js
index 2d2a5d32c0cf..2efd905e45f3 100644
--- a/packages/adapter-cloudflare-workers/files/entry.js
+++ b/packages/adapter-cloudflare-workers/files/entry.js
@@ -6,7 +6,7 @@ const static_asset_manifest = JSON.parse(static_asset_manifest_json);
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/`;
+const prefix = `/${manifest.appDir}/build/`;
 
 export default {
 	/**
diff --git a/packages/adapter-cloudflare/src/worker.js b/packages/adapter-cloudflare/src/worker.js
index ad7c4643034d..5c385749e667 100644
--- a/packages/adapter-cloudflare/src/worker.js
+++ b/packages/adapter-cloudflare/src/worker.js
@@ -4,7 +4,7 @@ import * as Cache from 'worktop/cfw.cache';
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/`;
+const prefix = `/${manifest.appDir}/build/`;
 
 /** @type {import('worktop/cfw').Module.Worker<{ ASSETS: import('worktop/cfw.durable').Durable.Object }>} */
 const worker = {
diff --git a/packages/adapter-netlify/src/edge.js b/packages/adapter-netlify/src/edge.js
index 89d2eb7e58ec..adf7dee8a9b7 100644
--- a/packages/adapter-netlify/src/edge.js
+++ b/packages/adapter-netlify/src/edge.js
@@ -2,7 +2,7 @@ import { Server } from '0SERVER';
 import { manifest, prerendered } from 'MANIFEST';
 
 const server = new Server(manifest);
-const prefix = `/${manifest.appDir}/`;
+const prefix = `/${manifest.appDir}/build/`;
 
 /**
  * @param { Request } request
@@ -12,6 +12,7 @@ const prefix = `/${manifest.appDir}/`;
 export default function handler(request, context) {
 	if (is_static_file(request)) {
 		// Static files can skip the handler
+		// TODO can we serve _app/build files with an immutable cache header?
 		return;
 	}
 
diff --git a/packages/adapter-node/src/handler.js b/packages/adapter-node/src/handler.js
index d5c66d920b15..e68ed88b3b22 100644
--- a/packages/adapter-node/src/handler.js
+++ b/packages/adapter-node/src/handler.js
@@ -22,18 +22,23 @@ const __dirname = path.dirname(fileURLToPath(import.meta.url));
 
 /**
  * @param {string} path
- * @param {number} max_age
- * @param {boolean} immutable
+ * @param {boolean} client
  */
-function serve(path, max_age, immutable = false) {
+function serve(path, client = false) {
 	return (
 		fs.existsSync(path) &&
 		sirv(path, {
 			etag: true,
-			maxAge: max_age,
-			immutable,
 			gzip: true,
-			brotli: true
+			brotli: true,
+			setHeaders:
+				client &&
+				((res, pathname) => {
+					// only apply to build directory, not e.g. version.json
+					if (pathname.startsWith(`/${manifest.appDir}/build/`)) {
+						res.setHeader('cache-control', 'public,max-age=31536000,immutable');
+					}
+				})
 		})
 	);
 }
@@ -126,9 +131,9 @@ function get_origin(headers) {
 
 export const handler = sequence(
 	[
-		serve(path.join(__dirname, '/client'), 31536000, true),
-		serve(path.join(__dirname, '/static'), 0),
-		serve(path.join(__dirname, '/prerendered'), 0),
+		serve(path.join(__dirname, '/client'), true),
+		serve(path.join(__dirname, '/static')),
+		serve(path.join(__dirname, '/prerendered')),
 		ssr
 	].filter(Boolean)
 );
diff --git a/packages/adapter-vercel/index.js b/packages/adapter-vercel/index.js
index 041f492557fa..37d0d7dda9a8 100644
--- a/packages/adapter-vercel/index.js
+++ b/packages/adapter-vercel/index.js
@@ -180,7 +180,7 @@ async function v1(builder, external) {
 			...prerendered_pages,
 			...prerendered_redirects,
 			{
-				src: `/${builder.config.kit.appDir}/.+`,
+				src: `/${builder.config.kit.appDir}/build/.+`,
 				headers: {
 					'cache-control': 'public, immutable, max-age=31536000'
 				}

From 1cd467fd7d9dfaeb9d6490fde9d73c370dc34945 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Mon, 23 May 2022 22:23:05 -0400
Subject: [PATCH 05/13] Update .changeset/wise-berries-flash.md

---
 .changeset/wise-berries-flash.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.changeset/wise-berries-flash.md b/.changeset/wise-berries-flash.md
index 0e72e7394437..fe4c7271283d 100644
--- a/.changeset/wise-berries-flash.md
+++ b/.changeset/wise-berries-flash.md
@@ -7,4 +7,4 @@
 '@sveltejs/kit': patch
 ---
 
-only serve \_app/build with immutable cache header, not \_app/version.json
+only serve `_app/build` with immutable cache header, not `_app/version.json`

From 3b88ffdd95069f7f8cdf0e5e19f8f783b8d9e8ca Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 24 May 2022 16:55:45 -0400
Subject: [PATCH 06/13] fix is_static_file

---
 packages/adapter-netlify/src/edge.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/adapter-netlify/src/edge.js b/packages/adapter-netlify/src/edge.js
index adf7dee8a9b7..23e3784488e4 100644
--- a/packages/adapter-netlify/src/edge.js
+++ b/packages/adapter-netlify/src/edge.js
@@ -2,7 +2,7 @@ import { Server } from '0SERVER';
 import { manifest, prerendered } from 'MANIFEST';
 
 const server = new Server(manifest);
-const prefix = `/${manifest.appDir}/build/`;
+const prefix = `/${manifest.appDir}/`;
 
 /**
  * @param { Request } request
@@ -34,6 +34,7 @@ function is_static_file(request) {
 	if (url.pathname.startsWith(prefix)) {
 		return true;
 	}
+
 	// prerendered pages and index.html files
 	const pathname = url.pathname.replace(/\/$/, '');
 	let file = pathname.substring(1);

From f3e35ea89f512caf7e33f92d11a1ed259b9b23f8 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 24 May 2022 16:59:04 -0400
Subject: [PATCH 07/13] rename /build/ to /immutable/

---
 .../adapter-cloudflare-workers/files/entry.js   |  2 +-
 packages/adapter-cloudflare/src/worker.js       |  2 +-
 packages/adapter-netlify/index.js               |  2 +-
 packages/adapter-node/src/handler.js            |  2 +-
 packages/adapter-vercel/index.js                |  2 +-
 packages/kit/src/core/build/build_client.js     |  2 +-
 packages/kit/src/core/build/build_server.js     |  2 +-
 .../kit/src/core/build/build_service_worker.js  |  2 +-
 packages/kit/src/core/build/index.js            | 17 ++++++++++-------
 packages/kit/test/apps/basics/test/test.js      |  2 +-
 10 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/packages/adapter-cloudflare-workers/files/entry.js b/packages/adapter-cloudflare-workers/files/entry.js
index 2efd905e45f3..3450959bdcd8 100644
--- a/packages/adapter-cloudflare-workers/files/entry.js
+++ b/packages/adapter-cloudflare-workers/files/entry.js
@@ -6,7 +6,7 @@ const static_asset_manifest = JSON.parse(static_asset_manifest_json);
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/build/`;
+const prefix = `/${manifest.appDir}/immutable/`;
 
 export default {
 	/**
diff --git a/packages/adapter-cloudflare/src/worker.js b/packages/adapter-cloudflare/src/worker.js
index 5c385749e667..6a8c0376deb7 100644
--- a/packages/adapter-cloudflare/src/worker.js
+++ b/packages/adapter-cloudflare/src/worker.js
@@ -4,7 +4,7 @@ import * as Cache from 'worktop/cfw.cache';
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/build/`;
+const prefix = `/${manifest.appDir}/immutable/`;
 
 /** @type {import('worktop/cfw').Module.Worker<{ ASSETS: import('worktop/cfw.durable').Durable.Object }>} */
 const worker = {
diff --git a/packages/adapter-netlify/index.js b/packages/adapter-netlify/index.js
index 89fa7305cc4e..774db538a5eb 100644
--- a/packages/adapter-netlify/index.js
+++ b/packages/adapter-netlify/index.js
@@ -64,7 +64,7 @@ export default function ({ split = false, edge = edge_set_in_env_var } = {}) {
 			builder.copy('_headers', headers_file);
 			appendFileSync(
 				headers_file,
-				`\n\n/${builder.config.kit.appDir}/*\n  cache-control: public\n  cache-control: immutable\n  cache-control: max-age=31536000\n`
+				`\n\n/${builder.config.kit.appDir}/immutable/*\n  cache-control: public\n  cache-control: immutable\n  cache-control: max-age=31536000\n`
 			);
 
 			// for esbuild, use ESM
diff --git a/packages/adapter-node/src/handler.js b/packages/adapter-node/src/handler.js
index e68ed88b3b22..4e3cfe1eeef3 100644
--- a/packages/adapter-node/src/handler.js
+++ b/packages/adapter-node/src/handler.js
@@ -35,7 +35,7 @@ function serve(path, client = false) {
 				client &&
 				((res, pathname) => {
 					// only apply to build directory, not e.g. version.json
-					if (pathname.startsWith(`/${manifest.appDir}/build/`)) {
+					if (pathname.startsWith(`/${manifest.appDir}/immutable/`)) {
 						res.setHeader('cache-control', 'public,max-age=31536000,immutable');
 					}
 				})
diff --git a/packages/adapter-vercel/index.js b/packages/adapter-vercel/index.js
index 37d0d7dda9a8..b731b91aaa38 100644
--- a/packages/adapter-vercel/index.js
+++ b/packages/adapter-vercel/index.js
@@ -180,7 +180,7 @@ async function v1(builder, external) {
 			...prerendered_pages,
 			...prerendered_redirects,
 			{
-				src: `/${builder.config.kit.appDir}/build/.+`,
+				src: `/${builder.config.kit.appDir}/immutable/.+`,
 				headers: {
 					'cache-control': 'public, immutable, max-age=31536000'
 				}
diff --git a/packages/kit/src/core/build/build_client.js b/packages/kit/src/core/build/build_client.js
index 17e602dd7d02..0a1b24fcf76b 100644
--- a/packages/kit/src/core/build/build_client.js
+++ b/packages/kit/src/core/build/build_client.js
@@ -96,7 +96,7 @@ export async function build_client({
 
 	/** @type {import('vite').Manifest} */
 	const vite_manifest = JSON.parse(
-		fs.readFileSync(`${client_out_dir}/build/manifest.json`, 'utf-8')
+		fs.readFileSync(`${client_out_dir}/immutable/manifest.json`, 'utf-8')
 	);
 
 	const entry = posixify(client_entry_file);
diff --git a/packages/kit/src/core/build/build_server.js b/packages/kit/src/core/build/build_server.js
index 97447465ac03..8cf13eb49bb0 100644
--- a/packages/kit/src/core/build/build_server.js
+++ b/packages/kit/src/core/build/build_server.js
@@ -69,7 +69,7 @@ export class Server {
 			manifest,
 			method_override: ${s(config.kit.methodOverride)},
 			paths: { base, assets },
-			prefix: assets + '/${config.kit.appDir}/build/',
+			prefix: assets + '/${config.kit.appDir}/immutable/',
 			prerender: {
 				default: ${config.kit.prerender.default},
 				enabled: ${config.kit.prerender.enabled}
diff --git a/packages/kit/src/core/build/build_service_worker.js b/packages/kit/src/core/build/build_service_worker.js
index 924ea08ae3e1..6b43554bdd2d 100644
--- a/packages/kit/src/core/build/build_service_worker.js
+++ b/packages/kit/src/core/build/build_service_worker.js
@@ -44,7 +44,7 @@ export async function build_service_worker(
 
 			export const build = [
 				${Array.from(build)
-					.map((file) => `${s(`${config.kit.paths.base}/${config.kit.appDir}/build/${file}`)}`)
+					.map((file) => `${s(`${config.kit.paths.base}/${config.kit.appDir}/immutable/${file}`)}`)
 					.join(',\n\t\t\t\t')}
 			];
 
diff --git a/packages/kit/src/core/build/index.js b/packages/kit/src/core/build/index.js
index 008cbd7a0475..4bd182b64753 100644
--- a/packages/kit/src/core/build/index.js
+++ b/packages/kit/src/core/build/index.js
@@ -26,15 +26,18 @@ export async function build(config, { log }) {
 
 	const { manifest_data } = sync.all(config);
 
+	// TODO this is so that Vite's preloading works. Unfortunately, it fails
+	// during `svelte-kit preview`, because we use a local asset path. If Vite
+	// used relative paths, I _think_ this could get fixed. Issue here:
+	// https://github.com/vitejs/vite/issues/2009
+	const { base, assets } = config.kit.paths;
+	const assets_base = `${assets || base}/${config.kit.appDir}/immutable/`;
+
 	const options = {
 		cwd,
 		config,
 		build_dir,
-		// TODO this is so that Vite's preloading works. Unfortunately, it fails
-		// during `svelte-kit preview`, because we use a local asset path. If Vite
-		// used relative paths, I _think_ this could get fixed. Issue here:
-		// https://github.com/vitejs/vite/issues/2009
-		assets_base: `${config.kit.paths.assets || config.kit.paths.base}/${config.kit.appDir}/build/`,
+		assets_base,
 		manifest_data,
 		output_dir,
 		client_entry_file: path.relative(cwd, `${get_runtime_path(config)}/client/start.js`),
@@ -65,8 +68,8 @@ export async function build(config, { log }) {
 
 	const files = new Set([
 		...static_files,
-		...client.chunks.map((chunk) => `${config.kit.appDir}/build/${chunk.fileName}`),
-		...client.assets.map((chunk) => `${config.kit.appDir}/build/${chunk.fileName}`)
+		...client.chunks.map((chunk) => `${config.kit.appDir}/immutable/${chunk.fileName}`),
+		...client.assets.map((chunk) => `${config.kit.appDir}/immutable/${chunk.fileName}`)
 	]);
 
 	// TODO is this right?
diff --git a/packages/kit/test/apps/basics/test/test.js b/packages/kit/test/apps/basics/test/test.js
index a2362222b0da..a8af8739de2e 100644
--- a/packages/kit/test/apps/basics/test/test.js
+++ b/packages/kit/test/apps/basics/test/test.js
@@ -347,7 +347,7 @@ test.describe.parallel('Imports', () => {
 			]);
 		} else {
 			expect(sources[0].startsWith('data:image/png;base64,')).toBeTruthy();
-			expect(sources[1]).toBe(`${baseURL}/_app/build/assets/large-3183867c.jpg`);
+			expect(sources[1]).toBe(`${baseURL}/_app/immutable/assets/large-3183867c.jpg`);
 		}
 	});
 });

From 271a83c7cf9b3699ee94ec508d999972f1eb54e7 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Tue, 24 May 2022 17:00:46 -0400
Subject: [PATCH 08/13] Update packages/kit/src/core/preview/index.js

---
 packages/kit/src/core/preview/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/kit/src/core/preview/index.js b/packages/kit/src/core/preview/index.js
index f258942fc51a..93dcfe98c562 100644
--- a/packages/kit/src/core/preview/index.js
+++ b/packages/kit/src/core/preview/index.js
@@ -68,7 +68,7 @@ export async function preview({ port, host, config, https: use_https = false })
 			sirv(join(config.kit.outDir, 'output/client'), {
 				setHeaders: (res, pathname) => {
 					// only apply to build directory, not e.g. version.json
-					if (pathname.startsWith(`/${config.kit.appDir}/build`)) {
+					if (pathname.startsWith(`/${config.kit.appDir}/immutable`)) {
 						res.setHeader('cache-control', 'public,max-age=31536000,immutable');
 					}
 				}

From c1b6ee01a71be025179a3212c64a3e6f9e2bf0ca Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Tue, 24 May 2022 17:00:50 -0400
Subject: [PATCH 09/13] Update packages/kit/src/core/build/build_client.js

---
 packages/kit/src/core/build/build_client.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/kit/src/core/build/build_client.js b/packages/kit/src/core/build/build_client.js
index 0a1b24fcf76b..8bea2daf31b1 100644
--- a/packages/kit/src/core/build/build_client.js
+++ b/packages/kit/src/core/build/build_client.js
@@ -59,7 +59,7 @@ export async function build_client({
 		build: {
 			cssCodeSplit: true,
 			manifest: true,
-			outDir: `${client_out_dir}/build`,
+			outDir: `${client_out_dir}/immutable`,
 			polyfillDynamicImport: false,
 			rollupOptions: {
 				input,

From e3f249337e34c5f9777d7725381de87b8ce85ce5 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Tue, 24 May 2022 17:00:55 -0400
Subject: [PATCH 10/13] Update packages/adapter-netlify/src/edge.js

---
 packages/adapter-netlify/src/edge.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/adapter-netlify/src/edge.js b/packages/adapter-netlify/src/edge.js
index 23e3784488e4..533d57eb2cc9 100644
--- a/packages/adapter-netlify/src/edge.js
+++ b/packages/adapter-netlify/src/edge.js
@@ -12,7 +12,7 @@ const prefix = `/${manifest.appDir}/`;
 export default function handler(request, context) {
 	if (is_static_file(request)) {
 		// Static files can skip the handler
-		// TODO can we serve _app/build files with an immutable cache header?
+		// TODO can we serve _app/immutable files with an immutable cache header?
 		return;
 	}
 

From 369b37229fe795c74d4a946d1a392b3e47571e51 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Tue, 24 May 2022 17:00:59 -0400
Subject: [PATCH 11/13] Update .changeset/wise-berries-flash.md

---
 .changeset/wise-berries-flash.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.changeset/wise-berries-flash.md b/.changeset/wise-berries-flash.md
index fe4c7271283d..8cb7218931d9 100644
--- a/.changeset/wise-berries-flash.md
+++ b/.changeset/wise-berries-flash.md
@@ -7,4 +7,4 @@
 '@sveltejs/kit': patch
 ---
 
-only serve `_app/build` with immutable cache header, not `_app/version.json`
+only serve `_app/immutable` with immutable cache header, not `_app/version.json`

From 26da5ad5ff5137bc7df9daaba8b4b5ed027050de Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 24 May 2022 17:36:30 -0400
Subject: [PATCH 12/13] update test

---
 packages/kit/test/apps/options-2/test/test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/kit/test/apps/options-2/test/test.js b/packages/kit/test/apps/options-2/test/test.js
index 0d8ba54090df..22b9e99d14a0 100644
--- a/packages/kit/test/apps/options-2/test/test.js
+++ b/packages/kit/test/apps/options-2/test/test.js
@@ -21,7 +21,7 @@ test.describe.parallel('Service worker', () => {
 			const response = await request.get('/basepath/service-worker.js');
 			const content = await response.text();
 
-			expect(content).toMatch(/\/_app\/start-[a-z0-9]+\.js/);
+			expect(content).toMatch(/\/_app\/immutable\/start-[a-z0-9]+\.js/);
 		});
 
 		test('does not register /basepath/service-worker.js', async ({ page }) => {

From 257d2fd78d8deb192ceae399123f1deeff6ed53f Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Tue, 24 May 2022 17:52:40 -0400
Subject: [PATCH 13/13] fix cloudflare adapters

---
 packages/adapter-cloudflare-workers/files/entry.js | 10 +++++++---
 packages/adapter-cloudflare/src/worker.js          | 10 +++++++---
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/packages/adapter-cloudflare-workers/files/entry.js b/packages/adapter-cloudflare-workers/files/entry.js
index 3450959bdcd8..1064a1547763 100644
--- a/packages/adapter-cloudflare-workers/files/entry.js
+++ b/packages/adapter-cloudflare-workers/files/entry.js
@@ -6,7 +6,7 @@ const static_asset_manifest = JSON.parse(static_asset_manifest_json);
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/immutable/`;
+const prefix = `/${manifest.appDir}/`;
 
 export default {
 	/**
@@ -23,11 +23,15 @@ export default {
 			const res = await get_asset_from_kv(req, env, context);
 			if (is_error(res.status)) return res;
 
+			const cache_control = url.pathname.startsWith(prefix + 'immutable/')
+				? 'public, immutable, max-age=31536000'
+				: 'no-cache';
+
 			return new Response(res.body, {
 				headers: {
-					// include original cache headers, minus cache-control which
+					// include original headers, minus cache-control which
 					// is overridden, and etag which is no longer useful
-					'cache-control': 'public, immutable, max-age=31536000',
+					'cache-control': cache_control,
 					'content-type': res.headers.get('content-type'),
 					'x-robots-tag': 'noindex'
 				}
diff --git a/packages/adapter-cloudflare/src/worker.js b/packages/adapter-cloudflare/src/worker.js
index 6a8c0376deb7..4a53b71ea0ee 100644
--- a/packages/adapter-cloudflare/src/worker.js
+++ b/packages/adapter-cloudflare/src/worker.js
@@ -4,7 +4,7 @@ import * as Cache from 'worktop/cfw.cache';
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/immutable/`;
+const prefix = `/${manifest.appDir}/`;
 
 /** @type {import('worktop/cfw').Module.Worker<{ ASSETS: import('worktop/cfw.durable').Durable.Object }>} */
 const worker = {
@@ -20,11 +20,15 @@ const worker = {
 		if (pathname.startsWith(prefix)) {
 			res = await env.ASSETS.fetch(req);
 
+			const cache_control = pathname.startsWith(prefix + 'immutable/')
+				? 'public, immutable, max-age=31536000'
+				: 'no-cache';
+
 			res = new Response(res.body, {
 				headers: {
-					// include original cache headers, minus cache-control which
+					// include original headers, minus cache-control which
 					// is overridden, and etag which is no longer useful
-					'cache-control': 'public, immutable, max-age=31536000',
+					'cache-control': cache_control,
 					'content-type': res.headers.get('content-type'),
 					'x-robots-tag': 'noindex'
 				}