diff --git a/src/blocks/carousel/carousel-tab-list/__tests__/view.test.ts b/src/blocks/carousel/carousel-tab-list/__tests__/view.test.ts
index d1523ce..0ce4cf5 100644
--- a/src/blocks/carousel/carousel-tab-list/__tests__/view.test.ts
+++ b/src/blocks/carousel/carousel-tab-list/__tests__/view.test.ts
@@ -209,6 +209,29 @@ describe( 'getTabTabIndex (roving tabindex)', () => {
 		);
 		expect( storeConfig!.callbacks.getTabTabIndex() ).toBe( '-1' );
 	} );
+
+	it( 'returns "0" for the first tab when selectedIndex is -1', () => {
+		( getContext as jest.Mock ).mockReturnValue(
+			mockContext( { selectedIndex: -1, snap: { index: 0 } } ),
+		);
+		expect( storeConfig!.callbacks.getTabTabIndex() ).toBe( '0' );
+	} );
+
+	it( 'returns "0" for the first tab when selectedIndex is undefined (uninitialized)', () => {
+		( getContext as jest.Mock ).mockReturnValue(
+			mockContext( { selectedIndex: undefined as unknown as number, snap: { index: 0 } } ),
+		);
+		expect( storeConfig!.callbacks.getTabTabIndex() ).toBe( '0' );
+	} );
+
+	it( 'returns "-1" when snap or snap.index is undefined', () => {
+		( getContext as jest.Mock ).mockReturnValue( {
+			carouselId: 'c1',
+			selectedIndex: 0,
+			snap: undefined,
+		} );
+		expect( storeConfig!.callbacks.getTabTabIndex() ).toBe( '-1' );
+	} );
 } );
 
 describe( 'getKeyFeatureDotText', () => {
diff --git a/src/blocks/carousel/carousel-tab-list/style.scss b/src/blocks/carousel/carousel-tab-list/style.scss
index 1753b0a..ef29650 100644
--- a/src/blocks/carousel/carousel-tab-list/style.scss
+++ b/src/blocks/carousel/carousel-tab-list/style.scss
@@ -32,7 +32,9 @@
 		align-items: center;
 		justify-content: center;
 		padding: 0.5em 1em;
-		border: var(--rt-tab-border-width) var(--rt-tab-border-style) var(--rt-tab-border-color);
+		border-width: var(--rt-tab-border-width);
+		border-style: var(--rt-tab-border-style);
+		border-color: var(--rt-tab-border-color);
 		background: var(--rt-tab-inactive-bg);
 		color: var(--rt-tab-inactive-color);
 		cursor: pointer;
@@ -45,11 +47,9 @@
 
 		&:focus-visible {
 
-			/* Visible by default (WCAG 2.4.7). Use currentColor unconditionally
-			 * because --rt-tab-border-color defaults to transparent. */
-			outline-color: currentcolor;
-			outline-style: solid;
-			outline-width: 2px;
+			/* Visible by default (WCAG 2.4.7). High contrast outline for keyboard
+			 * navigation. */
+			outline: 2px solid var(--wp-admin-theme-color, #007cba);
 			outline-offset: 2px;
 		}
 
@@ -61,9 +61,42 @@
 	}
 }
 
+@media (max-width: 1024px) {
+
+	.wp-block-rt-carousel-carousel-tab-list,
+	.wp-block-rt-carousel-carousel-tab-list.is-layout-flex {
+		max-width: 100%;
+		flex-wrap: nowrap;
+		overflow-x: auto;
+		-webkit-overflow-scrolling: touch;
+		scrollbar-width: thin;
+		scrollbar-color: rgba(0, 0, 0, 0.2) transparent;
+		padding-bottom: 4px;
+
+		&::-webkit-scrollbar {
+			height: 4px;
+		}
+
+		&::-webkit-scrollbar-track {
+			background: transparent;
+		}
+
+		&::-webkit-scrollbar-thumb {
+			background-color: rgba(0, 0, 0, 0.2);
+			border-radius: 2px;
+		}
+
+		.wp-block-rt-carousel-carousel-tab-list__tab {
+			flex: 0 0 auto;
+			white-space: nowrap;
+		}
+	}
+}
+
 @media (prefers-reduced-motion: reduce) {
 
 	.wp-block-rt-carousel-carousel-tab-list__tab {
 		transition: none;
 	}
 }
+
diff --git a/src/blocks/carousel/carousel-tab-list/view.ts b/src/blocks/carousel/carousel-tab-list/view.ts
index 4da4c14..7fd58cc 100644
--- a/src/blocks/carousel/carousel-tab-list/view.ts
+++ b/src/blocks/carousel/carousel-tab-list/view.ts
@@ -94,8 +94,17 @@ store( 'rt-carousel/carousel', {
 		 * inactive tabs are focusable only via arrow keys (tabindex=-1). */
 		getTabTabIndex: (): string => {
 			const context = getContext< TabContext >();
-			const isActive = context.selectedIndex === context.snap?.index;
+			const snapIndex = context.snap?.index;
+			if ( typeof snapIndex !== 'number' ) {
+				return '-1';
+			}
+			const selectedIndex =
+				typeof context.selectedIndex === 'number' && context.selectedIndex >= 0
+					? context.selectedIndex
+					: 0;
+			const isActive = selectedIndex === snapIndex;
 			return isActive ? '0' : '-1';
 		},
 	},
 } as CarouselStore );
+
diff --git a/src/blocks/carousel/save.tsx b/src/blocks/carousel/save.tsx
index 686eca1..e05edd6 100644
--- a/src/blocks/carousel/save.tsx
+++ b/src/blocks/carousel/save.tsx
@@ -56,7 +56,7 @@ export default function Save( {
 			: false,
 		isPlaying: !! autoplay, // Initially true if autoplay is enabled
 		timerIterationId: 0,
-		selectedIndex: -1,
+		selectedIndex: 0,
 		scrollSnaps: [],
 		canScrollPrev: false,
 		canScrollNext: false,
diff --git a/src/blocks/carousel/view.ts b/src/blocks/carousel/view.ts
index 0f93cf2..0aa7328 100644
--- a/src/blocks/carousel/view.ts
+++ b/src/blocks/carousel/view.ts
@@ -285,7 +285,14 @@ store( 'rt-carousel/carousel', {
 			const { snap } = context as CarouselContext & {
 				snap?: { index?: number };
 			};
-			return context.selectedIndex === snap?.index;
+			if ( typeof snap?.index !== 'number' ) {
+				return false;
+			}
+			const selectedIndex =
+				typeof context.selectedIndex === 'number' && context.selectedIndex >= 0
+					? context.selectedIndex
+					: 0;
+			return selectedIndex === snap.index;
 		},
 		getDotLabel: () => {
 			const context = getContext<CarouselContext>();