fix: don't use fork of unrelated route

.changeset/dull-spies-hammer.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: don't use fork of unrelated route

packages/kit/src/runtime/client/client.js

@@ -1690,8 +1690,9 @@ async function navigate({
 		}
 	}
 
+	// also compare ids to avoid using wrong fork (e.g. a new one could've been added while navigating)
+	const load_cache_fork = intent && load_cache?.id === intent.id ? load_cache.fork : null;
 	// reset preload synchronously after the history state has been set to avoid race conditions
-	const load_cache_fork = load_cache?.fork;
 	load_cache = null;
 
 	navigation_result.props.page.state = state;

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-data/offline/slow-navigation/+page.svelte

@@ -0,0 +1 @@
+<p>slow navigation</p>

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-data/offline/target/+page.svelte

@@ -0,0 +1 @@
+<p>target</p>

packages/kit/test/apps/basics/test/client.test.js

@@ -1047,6 +1047,21 @@ test.describe('data-sveltekit attributes', () => {
 		expect(page).toHaveURL('/data-sveltekit/preload-data/offline/slow-navigation');
 	});
 
+	test('data-sveltekit-preload does not abort ongoing navigation #2', async ({ page }) => {
+		await page.goto('/data-sveltekit/preload-data/offline');
+
+		await page.locator('#slow-navigation').dispatchEvent('click');
+		await page.waitForTimeout(100); // wait for navigation to start
+		await page.locator('#one').dispatchEvent('mousemove');
+		await Promise.all([
+			page.waitForTimeout(100), // wait for preloading to start
+			page.waitForLoadState('networkidle') // wait for preloading to finish
+		]);
+
+		expect(page).toHaveURL('/data-sveltekit/preload-data/offline/slow-navigation');
+		await expect(page.getByText('slow navigation', { exact: true })).toBeVisible();
+	});
+
 	test('data-sveltekit-preload-data tap works after data-sveltekit-preload-code hover', async ({
 		page
 	}) => {