diff --git a/frontend/src/lib/components/admin/BookingCreateModal.svelte b/frontend/src/lib/components/admin/BookingCreateModal.svelte
index c0fd071..0d87a92 100644
--- a/frontend/src/lib/components/admin/BookingCreateModal.svelte
+++ b/frontend/src/lib/components/admin/BookingCreateModal.svelte
@@ -1,7 +1,7 @@
 <script lang="ts">
 	import { authStore } from '$lib/stores/auth.svelte';
 	import { toast } from 'svelte-sonner';
-	import { SvelteDate } from 'svelte/reactivity';
+	import { SvelteDate, SvelteSet, SvelteURLSearchParams } from 'svelte/reactivity';
 	import { CalendarDate, getLocalTimeZone, type DateValue } from '@internationalized/date';
 	import { isValidUKPhone, toE164UK } from '$lib/utils/phone';
 	import { formatUserName } from '$lib/utils/nameDisplay';
@@ -235,7 +235,7 @@
 	// =============== Cache ===============
 	let workingHoursCache: Record<string, Record<string, DayHours>> = {};
 	let availableHoursCache: Record<string, Record<string, DayAvailability>> = {};
-	let loadingMonthKeys: Set<string> = new Set();
+	let loadingMonthKeys: Set<string> = new SvelteSet();
 
 	// =============== Derived Helpers ===============
 	function getTotalDuration() {
@@ -456,7 +456,7 @@
 		bookingCreateInitialLoadDone = false;
 		userNavigatedCalendar = false;
 		bookingCreateAutoSelectDone = false;
-		loadingMonthKeys = new Set();
+		loadingMonthKeys = new SvelteSet();
 		outOfHours = false;
 		normalWorkingHours = null;
 		// Clear reservation state
@@ -602,7 +602,7 @@
 
 		// Prevent re-entrant calls for the same month
 		if (loadingMonthKeys.has(monthKey)) return;
-		loadingMonthKeys = new Set(loadingMonthKeys).add(monthKey);
+		loadingMonthKeys = new SvelteSet(loadingMonthKeys).add(monthKey);
 
 		hoursMonthGeneration++;
 		const gen = hoursMonthGeneration;
@@ -657,7 +657,7 @@
 		} finally {
 			_loadingWorkingHours = false;
 			loadingAvailableHours = false;
-			loadingMonthKeys = new Set([...loadingMonthKeys].filter((k) => k !== monthKey));
+			loadingMonthKeys = new SvelteSet([...loadingMonthKeys].filter((k) => k !== monthKey));
 		}
 	}
 
@@ -811,7 +811,7 @@
 	async function fetchCustomServices() {
 		loadingCustomServices = true;
 		try {
-			const params = new URLSearchParams();
+			const params = new SvelteURLSearchParams();
 			if (customSearchQuery.trim()) {
 				params.set('q', customSearchQuery.trim());
 			} else {
diff --git a/frontend/src/lib/components/admin/BookingsCard.svelte b/frontend/src/lib/components/admin/BookingsCard.svelte
index 1cfb7b7..c10b6cd 100644
--- a/frontend/src/lib/components/admin/BookingsCard.svelte
+++ b/frontend/src/lib/components/admin/BookingsCard.svelte
@@ -1,6 +1,6 @@
 <script lang="ts">
 	import { authStore } from '$lib/stores/auth.svelte';
-	import { SvelteDate } from 'svelte/reactivity';
+	import { SvelteDate, SvelteURLSearchParams } from 'svelte/reactivity';
 	import { toast } from 'svelte-sonner';
 
 	// shadcn-svelte components
@@ -31,7 +31,7 @@
 	async function fetchBookings(pageIdx: number = 0, search: string = '') {
 		loadingSearch = true;
 		try {
-			const params = new URLSearchParams({
+			const params = new SvelteURLSearchParams({
 				per_page: '3'
 			});
 			const cursor = cursors[pageIdx];
diff --git a/frontend/src/lib/components/admin/CustomServicesManagement.svelte b/frontend/src/lib/components/admin/CustomServicesManagement.svelte
index 792623a..db7f2d2 100644
--- a/frontend/src/lib/components/admin/CustomServicesManagement.svelte
+++ b/frontend/src/lib/components/admin/CustomServicesManagement.svelte
@@ -8,6 +8,7 @@
 	import * as Modal from '$lib/components/ui/dialog';
 	import { Skeleton } from '$lib/components/ui/skeleton';
 	import { Separator } from '$lib/components/ui/separator';
+import { SvelteURLSearchParams } from 'svelte/reactivity';
 
 	type CustomService = {
 		id: string;
@@ -106,7 +107,7 @@
 	async function fetchServices() {
 		loading = true;
 		try {
-			const params = new URLSearchParams({
+			const params = new SvelteURLSearchParams({
 				page: page.toString(),
 				per_page: perPage.toString()
 			});
diff --git a/frontend/src/lib/components/admin/GiftCardsManagement.svelte b/frontend/src/lib/components/admin/GiftCardsManagement.svelte
index 9576a1a..e9927d6 100644
--- a/frontend/src/lib/components/admin/GiftCardsManagement.svelte
+++ b/frontend/src/lib/components/admin/GiftCardsManagement.svelte
@@ -8,6 +8,7 @@
 	import * as Modal from '$lib/components/ui/dialog';
 	import { Skeleton } from '$lib/components/ui/skeleton';
 	import { formatUserName } from '$lib/utils/nameDisplay';
+import { SvelteDate, SvelteURLSearchParams } from 'svelte/reactivity';
 
 	interface GiftCard {
 		id: string;
@@ -252,7 +253,7 @@
 		loading = true;
 		loadingSearch = true;
 		try {
-			const params = new URLSearchParams({
+			const params = new SvelteURLSearchParams({
 				page: page.toString(),
 				per_page: '10'
 			});
@@ -779,7 +780,7 @@
 	}
 
 	function formatDate(dateStr: string): string {
-		return new Date(dateStr).toLocaleDateString('en-GB', {
+		return new SvelteDate(dateStr).toLocaleDateString('en-GB', {
 			day: 'numeric',
 			month: 'short',
 			year: 'numeric',
@@ -789,14 +790,14 @@
 
 	function getExpiryDate(lastUsedAt?: string): Date | null {
 		if (!lastUsedAt) return null;
-		const date = new Date(lastUsedAt);
+		const date = new SvelteDate(lastUsedAt);
 		date.setMonth(date.getMonth() + 24);
 		return date;
 	}
 
 	function isExpired(lastUsedAt?: string): boolean {
 		const expiry = getExpiryDate(lastUsedAt);
-		return expiry !== null && expiry < new Date();
+		return expiry !== null && expiry < new SvelteDate();
 	}
 
 	// =============== Sorting ===============
@@ -854,7 +855,7 @@
 				case 'remaining':
 					return (a.amount_remaining - b.amount_remaining) * mul;
 				case 'created':
-					return (new Date(a.created_at).getTime() - new Date(b.created_at).getTime()) * mul;
+					return (new SvelteDate(a.created_at).getTime() - new SvelteDate(b.created_at).getTime()) * mul;
 				case 'status': {
 					const aVal = a.redeemed_by ? 2 : a.amount_remaining === 0 ? 1 : 0;
 					const bVal = b.redeemed_by ? 2 : b.amount_remaining === 0 ? 1 : 0;
@@ -883,7 +884,7 @@
 				case 'balance':
 					return (a.balance - b.balance) * mul;
 				case 'updated':
-					return (new Date(a.updated_at).getTime() - new Date(b.updated_at).getTime()) * mul;
+					return (new SvelteDate(a.updated_at).getTime() - new SvelteDate(b.updated_at).getTime()) * mul;
 				default:
 					return 0;
 			}
diff --git a/frontend/src/lib/components/admin/PatchTestsManagement.svelte b/frontend/src/lib/components/admin/PatchTestsManagement.svelte
index 15f3d56..ab1256a 100644
--- a/frontend/src/lib/components/admin/PatchTestsManagement.svelte
+++ b/frontend/src/lib/components/admin/PatchTestsManagement.svelte
@@ -7,6 +7,7 @@
 	import { Checkbox } from '$lib/components/ui/checkbox';
 	import { Skeleton } from '$lib/components/ui/skeleton';
 	import * as Modal from '$lib/components/ui/dialog';
+import { SvelteMap } from 'svelte/reactivity';
 
 	type Service = {
 		id: string;
@@ -110,7 +111,7 @@
 			if (ptRes.ok && svcRes.ok) {
 				patchTests = await ptRes.json();
 				const svcData = await svcRes.json();
-				const uniqueSvc = new Map();
+				const uniqueSvc = new SvelteMap();
 				svcData.forEach((s: Service) => {
 					if (s.id) uniqueSvc.set(s.id, s);
 				});
diff --git a/frontend/src/lib/components/admin/ServicesManagement.svelte b/frontend/src/lib/components/admin/ServicesManagement.svelte
index b339239..6e3ed41 100644
--- a/frontend/src/lib/components/admin/ServicesManagement.svelte
+++ b/frontend/src/lib/components/admin/ServicesManagement.svelte
@@ -8,6 +8,7 @@
 	import { Input } from '$lib/components/ui/input';
 	import * as Modal from '$lib/components/ui/dialog';
 	import { Skeleton } from '$lib/components/ui/skeleton';
+import { SvelteMap } from 'svelte/reactivity';
 
 	// =============== Types ===============
 	type Service = {
@@ -151,7 +152,7 @@
 
 			if (response.ok) {
 				const data = await response.json();
-				const uniqueServices = new Map();
+				const uniqueServices = new SvelteMap();
 				data.forEach((s: Service) => {
 					if (s.id) uniqueServices.set(s.id, s);
 				});
diff --git a/frontend/src/lib/components/admin/UserModal.svelte b/frontend/src/lib/components/admin/UserModal.svelte
index 556ca71..77c6205 100644
--- a/frontend/src/lib/components/admin/UserModal.svelte
+++ b/frontend/src/lib/components/admin/UserModal.svelte
@@ -1,6 +1,6 @@
 <script lang="ts">
 	import { authStore } from '$lib/stores/auth.svelte';
-	import { SvelteDate } from 'svelte/reactivity';
+	import { SvelteDate, SvelteURLSearchParams } from 'svelte/reactivity';
 	import { toast } from 'svelte-sonner';
 	import * as Modal from '$lib/components/ui/dialog';
 	import { Button } from '$lib/components/ui/button';
@@ -155,7 +155,7 @@
 
 		loadingBookings = true;
 		try {
-			const params = new URLSearchParams({
+			const params = new SvelteURLSearchParams({
 				per_page: '4'
 			});
 			const cursor = cursors[pageIdx];
diff --git a/frontend/src/lib/components/admin/UsersCard.svelte b/frontend/src/lib/components/admin/UsersCard.svelte
index bd60067..09d3716 100644
--- a/frontend/src/lib/components/admin/UsersCard.svelte
+++ b/frontend/src/lib/components/admin/UsersCard.svelte
@@ -6,6 +6,7 @@
 	import { Button } from '$lib/components/ui/button';
 	import { Skeleton } from '$lib/components/ui/skeleton';
 	import { formatUserName } from '$lib/utils/nameDisplay';
+import { SvelteURLSearchParams } from 'svelte/reactivity';
 
 	interface Props {
 		openUserModal: (userId: string) => void;
@@ -47,7 +48,7 @@
 		loadingSearch = true;
 
 		try {
-			const params = new URLSearchParams({
+			const params = new SvelteURLSearchParams({
 				per_page: '4'
 			});
 			const cursor = cursors[pageIdx];
diff --git a/frontend/src/lib/components/admin/WalkInCreateModal.svelte b/frontend/src/lib/components/admin/WalkInCreateModal.svelte
index d1526eb..8c58de6 100644
--- a/frontend/src/lib/components/admin/WalkInCreateModal.svelte
+++ b/frontend/src/lib/components/admin/WalkInCreateModal.svelte
@@ -2,7 +2,7 @@
 	import { authStore } from '$lib/stores/auth.svelte';
 	import { generateUUID } from '$lib/utils/uuid';
 	import { toast } from 'svelte-sonner';
-	import { SvelteDate } from 'svelte/reactivity';
+	import { SvelteDate, SvelteURLSearchParams } from 'svelte/reactivity';
 	import { getLocalTimeZone } from '@internationalized/date';
 	import { isValidUKPhone, toE164UK } from '$lib/utils/phone';
 	import { formatUserName } from '$lib/utils/nameDisplay';
@@ -351,7 +351,7 @@
 	async function fetchCustomServices() {
 		loadingCustomServices = true;
 		try {
-			const params = new URLSearchParams();
+			const params = new SvelteURLSearchParams();
 			if (customSearchQuery.trim()) {
 				params.set('q', customSearchQuery.trim());
 			} else {
diff --git a/frontend/src/routes/admin/schedule/+page.svelte b/frontend/src/routes/admin/schedule/+page.svelte
index e87185b..aa40df5 100644
--- a/frontend/src/routes/admin/schedule/+page.svelte
+++ b/frontend/src/routes/admin/schedule/+page.svelte
@@ -104,15 +104,15 @@
 	/** Return the current London date as a Date set to midnight in the local timezone.
 	 *  Uses Intl.DateTimeFormat with Europe/London to handle BST/GMT correctly. */
 	function getLondonToday(): Date {
-		const dateStr = new Date().toLocaleDateString('en-CA', { timeZone: 'Europe/London' });
-		return new Date(dateStr + 'T00:00:00');
+		const dateStr = new SvelteDate().toLocaleDateString('en-CA', { timeZone: 'Europe/London' });
+		return new SvelteDate(dateStr + 'T00:00:00');
 	}
 
 	/** Return the current time-of-day in London as minutes since midnight, using
 	 *  Intl.DateTimeFormat with Europe/London so the current-time blue line is
 	 *  positioned correctly regardless of the browser's system timezone. */
 	function getLondonNowMinutes(): number {
-		const timeStr = new Date().toLocaleTimeString('en-GB', {
+		const timeStr = new SvelteDate().toLocaleTimeString('en-GB', {
 			timeZone: 'Europe/London',
 			hour: '2-digit',
 			minute: '2-digit',
@@ -127,7 +127,7 @@
 	 *  at 23:30 UTC (00:30 BST next day) are grouped under the correct
 	 *  London date column rather than the UTC date. */
 	function getLondonDateKey(iso: string): string {
-		return new Date(iso).toLocaleDateString('en-CA', { timeZone: 'Europe/London' });
+		return new SvelteDate(iso).toLocaleDateString('en-CA', { timeZone: 'Europe/London' });
 	}
 
 	function formatWeekLabel(start: Date): string {
@@ -316,7 +316,7 @@
 
 	function navigateWeek(delta: number) {
 		if (!weekStart) return;
-		const d = new Date(weekStart);
+		const d = new SvelteDate(weekStart);
 		d.setDate(d.getDate() + delta * 7);
 		weekStart = d;
 	}
diff --git a/frontend/src/routes/gdpr/+page.svelte b/frontend/src/routes/gdpr/+page.svelte
index 2a834aa..975d108 100644
--- a/frontend/src/routes/gdpr/+page.svelte
+++ b/frontend/src/routes/gdpr/+page.svelte
@@ -6,6 +6,7 @@
 	import * as Card from '$lib/components/ui/card';
 	import { Skeleton } from '$lib/components/ui/skeleton';
 	import { Separator } from '$lib/components/ui/separator';
+import { SvelteMap } from 'svelte/reactivity';
 
 	type GdprData = {
 		user_profile: {
@@ -401,7 +402,7 @@
 			.filter((r) => r.status === 'completed')
 			.reduce((sum, r) => sum + Number(r.amount), 0);
 
-		const serviceMap = new Map<string, { count: number; total: number }>();
+		const serviceMap = new SvelteMap<string, { count: number; total: number }>();
 		for (const b of bookings) {
 			for (const s of b.services ?? []) {
 				const existing = serviceMap.get(s.name) ?? { count: 0, total: 0 };
@@ -415,7 +416,7 @@
 			.sort((a, b) => b.count - a.count)
 			.slice(0, 5);
 
-		const methodMap = new Map<string, { count: number; total: number }>();
+		const methodMap = new SvelteMap<string, { count: number; total: number }>();
 		for (const p of payments.filter((p) => p.status === 'completed')) {
 			if (p.payment_method === 'discount') continue;
 			const method = p.payment_method.replace(/_/g, ' ');