ui: Remove PWA navigate fallback to prevent caching API endpoint requests (#25174)

tools/ui/src/lib/constants/pwa.ts

@@ -288,9 +288,7 @@ export const API_CACHING_PATTERNS = {
 } as const;
 
 // SvelteKit PWA plugin options
-export const PWA_KIT_OPTIONS = {
+export const PWA_KIT_OPTIONS = {} as const;
-	NAVIGATE_FALLBACK: './'
-} as const;
 
 export const APPLE_META_TAGS = {
 	MOBILE_WEB_APP_CAPABLE: { name: 'apple-mobile-web-app-capable', content: 'yes' },
@@ -322,6 +320,14 @@ export const SVELTEKIT_PWA_OPTIONS: SvelteKitPWAOptions = {
 		globIgnores: GLOB_IGNORES,
 		maximumFileSizeToCacheInBytes: CACHE_SETTINGS.MAX_FILE_SIZE_BYTES,
 
+		// Prevent @vite-pwa/sveltekit from auto-adding a NavigationRoute by
+		// setting navigateFallback to empty string. This keeps the service
+		// worker from intercepting direct browser navigation to server API
+		// endpoints (e.g. /slots, /models, /v1/models) which should return
+		// JSON, not the SPA HTML shell. The server's own static-file fallback
+		// handles non-API navigation to index.html for the SPA router.
+		navigateFallback: '',
+
 		// Runtime caching for API calls - use NetworkFirst so APIs are always fresh
 		runtimeCaching: [
 			{
@@ -351,10 +357,7 @@ export const SVELTEKIT_PWA_OPTIONS: SvelteKitPWAOptions = {
 
 	devOptions: {
 		enabled: true,
-		suppressWarnings: true,
+		suppressWarnings: true
-		// Use PWA_KIT_OPTIONS.NAVIGATE_FALLBACK to match production SW behaviour
-		// (navigateFallback defaults to the configured base path, which is '/' for this SPA).
-		navigateFallback: PWA_KIT_OPTIONS.NAVIGATE_FALLBACK
 	},
 
 	// SvelteKit-specific options

tools/ui/tests/e2e/pwa.e2e.ts

@@ -43,7 +43,10 @@ test.describe('PWA Service Worker', () => {
 		expect(swContent).toMatch(/"_app\/immutable\/assets\/bundle\.[a-zA-Z0-9_-]+\.css"/);
 		expect(swContent).toMatch(/"manifest\.webmanifest"/);
 		expect(swContent).toMatch(/"_app\/version\.json"/);
-		expect(swContent).toMatch(/NavigationRoute/);
+		// NavigationRoute is intentionally absent — server API endpoints
+		// (e.g. /slots, /models) must not be intercepted by the PWA and
+		// should return JSON directly from the server.
+		expect(swContent).not.toMatch(/NavigationRoute/);
 		expect(swContent).toMatch(/api-cache/);
 	});
 

tools/ui/tests/unit/pwa.spec.ts

@@ -108,9 +108,11 @@ describe('PWA Build Output', () => {
 			expect(swContent).toMatch(/"manifest\.webmanifest"/);
 		});
 
-		it('has navigation route registered', () => {
+		it('no navigation route — API endpoints bypass PWA', () => {
 			expect(swContent).toBeTruthy();
-			expect(swContent).toMatch(/NavigationRoute/);
+			// NavigationRoute is intentionally absent so direct browser
+			// navigation to server API endpoints returns JSON, not HTML.
+			expect(swContent).not.toMatch(/NavigationRoute/);
 		});
 
 		it('has runtime caching for API routes', () => {