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fix: Stop re-loading already-loaded CSS during server-side route resolution #15014

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Merged
Rich-Harris merged 3 commits into from
Dec 2, 2025
Merged

fix: Stop re-loading already-loaded CSS during server-side route resolution #15014

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fix: Stop re-loading already-loaded CSS during server-side route reso…
elliott-with-the-longest-name-on-github Dec 2, 2025
a1e61cf
remove comments
elliott-with-the-longest-name-on-github Dec 2, 2025
e87bf77
guarantee we only query the DOM once
Rich-Harris Dec 2, 2025
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5 changes: 5 additions & 0 deletions .changeset/eager-rats-turn.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'@sveltejs/kit': patch
---

fix: Stop re-loading already-loaded CSS during server-side route resolution
18 changes: 11 additions & 7 deletions packages/kit/src/runtime/client/utils.js
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Expand Up @@ -323,8 +323,8 @@ export function is_external_url(url, base, hash_routing) {
return false;
}

/** @type {Record<string, boolean>} */
const seen = {};
/** @type {Set<string> | null} */
let seen = null;

/**
* Used for server-side resolution, to replicate Vite's CSS loading behaviour in production.
Expand All @@ -341,13 +341,17 @@ export function load_css(deps) {
);
const csp_nonce = csp_nonce_meta?.nonce || csp_nonce_meta?.getAttribute('nonce');

seen ??= new Set(
Array.from(document.querySelectorAll('link[rel="stylesheet"]')).map((link) => {
return /** @type {HTMLLinkElement} */ (link).href;
})
);

for (const dep of deps) {
if (dep in seen) continue;
seen[dep] = true;
const href = new URL(dep, document.baseURI).href;

if (document.querySelector(`link[href="${dep}"][rel="stylesheet"]`)) {
continue;
}
if (seen.has(href)) continue;
seen.add(href);

const link = document.createElement('link');
link.rel = 'stylesheet';
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12 changes: 6 additions & 6 deletions packages/kit/test/apps/basics/test/cross-platform/client.test.js
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Expand Up @@ -9,7 +9,7 @@
test.describe.configure({ mode: 'parallel' });

test.describe('a11y', () => {
test('resets focus', async ({ page, clicknav, browserName }) => {

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GitHub Actions / test-kit-cross-browser (18, windows-latest, chromium, dev)

flaky test: resets focus 

retries: 2
const tab = browserName === 'webkit' ? 'Alt+Tab' : 'Tab';

await page.goto('/accessibility/a');
Expand All @@ -33,7 +33,7 @@
expect(await page.evaluate(() => document.documentElement.getAttribute('tabindex'))).toBe(null);
});

test('applies autofocus after a navigation', async ({ page, clicknav }) => {

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GitHub Actions / test-kit-cross-browser (18, windows-latest, chromium, dev)

flaky test: applies autofocus after a navigation 

retries: 2
await page.goto('/accessibility/autofocus/a');

await clicknav('[href="/accessibility/autofocus/b"]');
Expand Down Expand Up @@ -182,7 +182,7 @@
expect(await page.innerHTML('pre')).toBe('1 true leave');
});

test('beforeNavigate is not triggered on redirect', async ({ page, baseURL }) => {

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flaky test: beforeNavigate is not triggered on redirect 

retries: 2
await page.goto('/navigation-lifecycle/before-navigate/prevent-navigation');

await page.click('[href="/navigation-lifecycle/before-navigate/redirect"]');
Expand Down Expand Up @@ -927,9 +927,9 @@
// we start watching requests
await page.goto('/routing/form-get', { waitUntil: 'load' });

expect(await page.textContent('h1')).toBe('...');
expect(await page.textContent('h2')).toBe('enter');
expect(await page.textContent('h3')).toBe('...');
await expect(page.locator('h1')).toHaveText('...');
await expect(page.locator('h2')).toHaveText('enter');
await expect(page.locator('h3')).toHaveText('...');

/** @type {string[]} */
const requests = [];
Expand All @@ -939,10 +939,10 @@
await page.locator('button').click();

// Filter out server-side route resolution request
await expect(page.locator('h1')).toHaveText('updated');
await expect(page.locator('h2')).toHaveText('form');
await expect(page.locator('h3')).toHaveText('bar');
expect(requests.filter((r) => !r.includes('__route.js'))).toEqual([]);
expect(await page.textContent('h1')).toBe('updated');
expect(await page.textContent('h2')).toBe('form');
expect(await page.textContent('h3')).toBe('bar');
});

test('responds to <form target="_blank"> submission with new tab', async ({ page }) => {
Expand Down
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