diff --git a/frontend/eslint.a11y.config.js b/frontend/eslint.a11y.config.js
index ff9e8d1..baaf241 100644
--- a/frontend/eslint.a11y.config.js
+++ b/frontend/eslint.a11y.config.js
@@ -29,5 +29,22 @@ export default defineConfig(
 				svelteConfig
 			}
 		}
+	},
+	{
+		name: 'svelte:a11y:rules',
+		files: ['**/*.svelte', '**/*.svelte.ts', '**/*.svelte.js'],
+		rules: {
+			// Compile all .svelte files and surface compiler warnings as ESLint errors.
+			// The Svelte 5 compiler has built-in a11y checks (a11y_missing_attribute,
+			// a11y_click_events_have_key_events, a11y_no_static_element_interactions, etc.)
+			// that are enabled by default via accessibilityWarnings: true.
+			'svelte/valid-compile': 'error',
+
+			// Require explicit type attribute on <button> elements
+			'svelte/button-has-type': 'error',
+
+			// Require rel="noopener noreferrer" with target="_blank"
+			'svelte/no-target-blank': 'error'
+		}
 	}
 );
diff --git a/frontend/src/lib/components/admin/BookingCreateModal.svelte b/frontend/src/lib/components/admin/BookingCreateModal.svelte
index b1f0037..7ae932f 100644
--- a/frontend/src/lib/components/admin/BookingCreateModal.svelte
+++ b/frontend/src/lib/components/admin/BookingCreateModal.svelte
@@ -1075,6 +1075,7 @@
 						<!-- Tabs -->
 						<div class="flex gap-6 border-b border-gray-200">
 							<button
+								type="button"
 								class="pb-2 text-sm font-medium transition-colors {userType === 'member'
 									? 'border-b-2 border-primary text-primary'
 									: 'text-gray-500 hover:text-gray-700'}"
@@ -1086,6 +1087,7 @@
 								Member
 							</button>
 							<button
+								type="button"
 								class="pb-2 text-sm font-medium transition-colors {userType === 'guest'
 									? 'border-b-2 border-primary text-primary'
 									: 'text-gray-500 hover:text-gray-700'}"
@@ -1302,6 +1304,7 @@
 									<div class="space-y-2">
 										{#each customServices as cs (cs.id)}
 											<button
+												type="button"
 												class="flex w-full items-center justify-between rounded-lg border px-3 py-2 text-sm hover:bg-gray-50"
 												onclick={() => {
 													if (!selectedServices.some((s) => s.id === cs.id)) {
diff --git a/frontend/src/lib/components/admin/HolidayHours.svelte b/frontend/src/lib/components/admin/HolidayHours.svelte
index da2c1f5..a31e0b5 100644
--- a/frontend/src/lib/components/admin/HolidayHours.svelte
+++ b/frontend/src/lib/components/admin/HolidayHours.svelte
@@ -528,6 +528,7 @@
 								<div class="flex items-center justify-between text-sm">
 									<span>Week starting: {week}</span>
 									<button
+										type="button"
 										class="text-xs text-red-500 hover:text-red-700"
 										onclick={() => removeWeek(index)}
 									>
diff --git a/frontend/src/lib/components/admin/WalkInCreateModal.svelte b/frontend/src/lib/components/admin/WalkInCreateModal.svelte
index 739fef4..890bcc6 100644
--- a/frontend/src/lib/components/admin/WalkInCreateModal.svelte
+++ b/frontend/src/lib/components/admin/WalkInCreateModal.svelte
@@ -653,6 +653,7 @@
 						<!-- Tabs -->
 						<div class="flex gap-6 border-b border-gray-200">
 							<button
+								type="button"
 								class="pb-2 text-sm font-medium transition-colors {userType === 'member'
 									? 'border-b-2 border-primary text-primary'
 									: 'text-gray-500 hover:text-gray-700'}"
@@ -664,6 +665,7 @@
 								Member
 							</button>
 							<button
+								type="button"
 								class="pb-2 text-sm font-medium transition-colors {userType === 'guest'
 									? 'border-b-2 border-primary text-primary'
 									: 'text-gray-500 hover:text-gray-700'}"
@@ -877,6 +879,7 @@
 									<div class="space-y-2">
 										{#each customServices as cs (cs.id)}
 											<button
+												type="button"
 												class="flex w-full items-center justify-between rounded-lg border px-3 py-2 text-sm hover:bg-gray-50"
 												onclick={() => {
 													if (!selectedServices.some((s) => s.id === cs.id)) {
diff --git a/frontend/src/lib/components/layout/ContactCard.svelte b/frontend/src/lib/components/layout/ContactCard.svelte
index 60e357e..fb4a89d 100644
--- a/frontend/src/lib/components/layout/ContactCard.svelte
+++ b/frontend/src/lib/components/layout/ContactCard.svelte
@@ -103,7 +103,7 @@
 				<a
 					href={`https://instagram.com/${instagram}`}
 					target="_blank"
-					rel="noopener"
+					rel="noopener noreferrer"
 					class="text-primary hover:underline">@{instagram}</a
 				>
 			</div>
diff --git a/frontend/src/lib/components/layout/NavBar.svelte b/frontend/src/lib/components/layout/NavBar.svelte
index 2e03af9..b9cd442 100644
--- a/frontend/src/lib/components/layout/NavBar.svelte
+++ b/frontend/src/lib/components/layout/NavBar.svelte
@@ -101,7 +101,7 @@
 				<a
 					href="https://instagram.com"
 					target="_blank"
-					rel="noopener"
+					rel="noopener noreferrer"
 					class="text-gray-600 hover:text-primary"
 					aria-label="Instagram"
 				>
@@ -180,6 +180,7 @@
 			<!-- Mobile: Burger -->
 			<div class="flex items-center md:hidden">
 				<button
+					type="button"
 					onclick={toggleMenu}
 					class="relative h-6 w-6 focus:outline-none"
 					aria-label="Toggle menu"
diff --git a/frontend/src/routes/account/+page.svelte b/frontend/src/routes/account/+page.svelte
index c81ccbf..a95e9f7 100644
--- a/frontend/src/routes/account/+page.svelte
+++ b/frontend/src/routes/account/+page.svelte
@@ -1303,6 +1303,7 @@
 		<div class="desktop-tab-menu">
 			<div class="flex rounded-lg border bg-gray-50 p-1">
 				<button
+					type="button"
 					class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 					'general'
 						? 'bg-white text-gray-900 shadow-sm'
@@ -1323,6 +1324,7 @@
 				</button>
 				{#if authStore.currentUser?.role !== 'admin'}
 					<button
+						type="button"
 						class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 						'history'
 							? 'bg-white text-gray-900 shadow-sm'
@@ -1346,6 +1348,7 @@
 				{/if}
 				{#if authStore.currentUser?.role !== 'admin'}
 					<button
+						type="button"
 						class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 						'referral'
 							? 'bg-white text-gray-900 shadow-sm'
@@ -1369,6 +1372,7 @@
 				{/if}
 				{#if canSaveCards}
 					<button
+						type="button"
 						class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 						'cards'
 							? 'bg-white text-gray-900 shadow-sm'
@@ -1394,6 +1398,7 @@
 					</button>
 				{/if}
 				<button
+					type="button"
 					class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 					'admin'
 						? 'bg-white text-gray-900 shadow-sm'
@@ -2734,6 +2739,7 @@
 		<div class="mobile-tab-menu">
 			<div class="flex rounded-lg border bg-gray-50 p-1">
 				<button
+					type="button"
 					class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 					'general'
 						? 'bg-white text-gray-900 shadow-sm'
@@ -2755,6 +2761,7 @@
 
 				{#if authStore.currentUser?.role !== 'admin'}
 					<button
+						type="button"
 						class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 						'history'
 							? 'bg-white text-gray-900 shadow-sm'
@@ -2779,6 +2786,7 @@
 
 				{#if authStore.currentUser?.role !== 'admin'}
 					<button
+						type="button"
 						class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 						'referral'
 							? 'bg-white text-gray-900 shadow-sm'
@@ -2803,6 +2811,7 @@
 
 				{#if canSaveCards}
 					<button
+						type="button"
 						class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 						'cards'
 							? 'bg-white text-gray-900 shadow-sm'
@@ -2829,6 +2838,7 @@
 				{/if}
 
 				<button
+					type="button"
 					class="flex-1 rounded-md px-2 py-2 text-xs font-medium transition-colors {activeTab ===
 					'admin'
 						? 'bg-white text-gray-900 shadow-sm'
diff --git a/frontend/src/routes/admin/+page.svelte b/frontend/src/routes/admin/+page.svelte
index f42cb55..599dce7 100644
--- a/frontend/src/routes/admin/+page.svelte
+++ b/frontend/src/routes/admin/+page.svelte
@@ -279,6 +279,7 @@
 		<!-- 2. Customers & Bookings -->
 		<div class="rounded-lg border">
 			<button
+				type="button"
 				class="flex w-full items-center justify-between bg-gray-50 px-4 py-3 transition-colors hover:bg-gray-100 {sectionState.customers ===
 				'expanded'
 					? 'rounded-t-lg'
@@ -310,6 +311,7 @@
 		<!-- 3. Services & Products -->
 		<div class="rounded-lg border">
 			<button
+				type="button"
 				class="flex w-full items-center justify-between bg-gray-50 px-4 py-3 transition-colors hover:bg-gray-100 {sectionState.services ===
 				'expanded'
 					? 'rounded-t-lg'
@@ -354,6 +356,7 @@
 		<!-- 4. Scheduling & Hours -->
 		<div class="rounded-lg border">
 			<button
+				type="button"
 				class="flex w-full items-center justify-between bg-gray-50 px-4 py-3 transition-colors hover:bg-gray-100 {sectionState.scheduling ===
 				'expanded'
 					? 'rounded-t-lg'
@@ -384,6 +387,7 @@
 		<!-- 5. Promotions & Finance -->
 		<div class="rounded-lg border">
 			<button
+				type="button"
 				class="flex w-full items-center justify-between bg-gray-50 px-4 py-3 transition-colors hover:bg-gray-100 {sectionState.promotions ===
 				'expanded'
 					? 'rounded-t-lg'
@@ -413,6 +417,7 @@
 		<!-- 6. Business Settings -->
 		<div class="rounded-lg border">
 			<button
+				type="button"
 				class="flex w-full items-center justify-between bg-gray-50 px-4 py-3 transition-colors hover:bg-gray-100 {sectionState.settings ===
 				'expanded'
 					? 'rounded-t-lg'
diff --git a/frontend/src/routes/gdpr/+page.svelte b/frontend/src/routes/gdpr/+page.svelte
index 92fa06a..fe3d9d2 100644
--- a/frontend/src/routes/gdpr/+page.svelte
+++ b/frontend/src/routes/gdpr/+page.svelte
@@ -541,10 +541,11 @@
 		<div class="print-area">
 			<div class="mb-6 flex flex-col items-start justify-between gap-4 sm:flex-row sm:items-center">
 				<div>
-					<button
-						onclick={handleGotoAccount}
-						class="mb-2 inline-flex items-center gap-1 text-sm text-gray-500 hover:text-gray-900"
-					>
+				<button
+					type="button"
+					onclick={handleGotoAccount}
+					class="mb-2 inline-flex items-center gap-1 text-sm text-gray-500 hover:text-gray-900"
+				>
 						<svg
 							xmlns="http://www.w3.org/2000/svg"
 							class="h-4 w-4"
diff --git a/frontend/src/routes/portfolio/+page.svelte b/frontend/src/routes/portfolio/+page.svelte
index 8d8541e..15f0fe1 100644
--- a/frontend/src/routes/portfolio/+page.svelte
+++ b/frontend/src/routes/portfolio/+page.svelte
@@ -727,6 +727,7 @@
 						{@const hasActiveFilters = Object.values(selectedFilters).some((v) => v && v !== '')}
 						{#if hasActiveFilters || selectedTag || selectedTags.length > 0}
 							<button
+								type="button"
 								class="filter-dropdown flex shrink-0 items-center justify-center"
 								onclick={clearFilters}
 								aria-label="Clear all filters"
@@ -750,6 +751,7 @@
 							{@const hasActiveFilter = selectedValue && selectedValue !== ''}
 							<div class="filter-dropdown relative shrink-0">
 								<button
+									type="button"
 									class="flex items-center gap-1 rounded-lg border border-gray-300 bg-white px-3 py-1.5 text-sm transition-colors hover:bg-gray-50 {hasActiveFilter
 										? 'border-primary bg-primary/10'
 										: ''}"
@@ -781,6 +783,7 @@
 							style="position: fixed; left: {dropdownPosition?.x}px; top: {dropdownPosition?.y}px;"
 						>
 							<button
+								type="button"
 								class="filter-dropdown flex w-full items-center justify-between px-3 py-2 text-left text-sm transition-colors hover:bg-fuchsia-50 {selectedValue ===
 								''
 									? 'bg-fuchsia-100 font-medium'
@@ -794,6 +797,7 @@
 							</button>
 							{#each filter.values as value (value.value)}
 								<button
+									type="button"
 									class="filter-dropdown flex w-full items-center justify-between px-3 py-2 text-left text-sm transition-colors hover:bg-fuchsia-50 {selectedValue ===
 									value.value
 										? 'bg-fuchsia-100 font-medium'
@@ -827,6 +831,7 @@
 
 				{#if selectedTag || selectedTags.length > 0}
 					<button
+						type="button"
 						class="flex shrink-0 items-center justify-center"
 						onclick={clearSearch}
 						aria-label="Clear search tags"
@@ -852,6 +857,7 @@
 	<div class="grid grid-cols-3 gap-1 p-2 pt-0 sm:grid-cols-4 md:grid-cols-6 lg:grid-cols-8">
 		{#each images as img (img.id)}
 			<button
+				type="button"
 				class="relative aspect-square overflow-hidden rounded-xs transition-opacity hover:opacity-90 active:opacity-75"
 				onclick={() => openModal(img)}
 				aria-label="View full size portfolio item"
@@ -970,6 +976,7 @@
 				</div>
 
 				<button
+					type="button"
 					bind:this={closeBtnRef}
 					class="absolute right-2 z-[60] rounded-full bg-black/50 p-2 text-white transition-colors hover:bg-black/70 sm:right-4"
 					onclick={closeModal}
@@ -987,6 +994,7 @@
 
 				{#if currentIndex > 0}
 					<button
+						type="button"
 						bind:this={prevButtonRef}
 						class="absolute top-1/2 left-2 z-[60] -translate-y-1/2 rounded-full bg-black/50 p-3 text-white transition-colors hover:bg-black/70 sm:left-4"
 						onclick={navigatePrev}
@@ -1005,6 +1013,7 @@
 
 				{#if currentIndex < images.length - 1}
 					<button
+						type="button"
 						bind:this={nextButtonRef}
 						class="absolute top-1/2 right-2 z-[60] -translate-y-1/2 rounded-full bg-black/50 p-3 text-white transition-colors hover:bg-black/70 sm:right-4"
 						onclick={navigateNext}
diff --git a/frontend/src/routes/schedule/+page.svelte b/frontend/src/routes/schedule/+page.svelte
index 648ee9a..18c6d97 100644
--- a/frontend/src/routes/schedule/+page.svelte
+++ b/frontend/src/routes/schedule/+page.svelte
@@ -369,6 +369,7 @@
 												{/if}
 
 												<button
+													type="button"
 													onclick={() => openBooking(booking.id)}
 													class="inline-flex items-center gap-1 rounded-lg px-2.5 py-1.5 text-sm font-medium text-gray-500 transition-colors hover:bg-gray-100 hover:text-gray-900"
 												>