diff --git a/src/app/demo/combined-date-picker/page.tsx b/src/app/demo/combined-date-picker/page.tsx
index 4a5bc69..392ed3e 100644
--- a/src/app/demo/combined-date-picker/page.tsx
+++ b/src/app/demo/combined-date-picker/page.tsx
@@ -1,3 +1,5 @@
+"use client";
+
 import { Badge } from "@/components/ui/badge";
 import {
 	Card,
@@ -7,10 +9,19 @@ import {
 	CardTitle,
 } from "@/components/ui/card";
 import { CombinedDatePickerDemo } from "@/components/ui/combined-date-picker-demo";
+import { useIsMobile } from "@/hooks/use-mobile";
 
 export default function CombinedDatePickerDemoPage() {
+	const isMobile = useIsMobile();
+
 	return (
-		<div className="mx-auto flex min-h-screen w-full max-w-4xl flex-col gap-6 px-4 py-10 sm:px-6 lg:px-8">
+		<div
+			className={
+				isMobile
+					? "mx-auto flex min-h-screen w-full max-w-4xl flex-col gap-6 px-4 py-10"
+					: "mx-auto flex min-h-screen w-full max-w-4xl flex-col gap-6 px-8 py-10"
+			}
+		>
 			<div className="flex flex-col gap-3">
 				<Badge variant="outline" className="w-fit">
 					Demo Route
@@ -19,7 +30,13 @@ export default function CombinedDatePickerDemoPage() {
 					<h1 className="text-3xl font-semibold tracking-tight">
 						Date &amp; Time Picker
 					</h1>
-					<p className="max-w-2xl text-sm text-muted-foreground sm:text-base">
+					<p
+						className={
+							isMobile
+								? "max-w-2xl text-sm text-muted-foreground"
+								: "max-w-2xl text-base text-muted-foreground"
+						}
+					>
 						Inline date input paired with a locale-aware time picker. The return
 						calendar disables dates before departure, and time fields switch
 						between 24-hour and 12-hour formats automatically.
diff --git a/src/app/page.tsx b/src/app/page.tsx
index 1d48b9e..7e3803e 100644
--- a/src/app/page.tsx
+++ b/src/app/page.tsx
@@ -27,6 +27,7 @@ import {
 	DropdownMenuSeparator,
 	DropdownMenuTrigger,
 } from "@/components/ui/dropdown-menu";
+import { useIsMobile } from "@/hooks/use-mobile";
 import { getAiCreateOutcome } from "@/lib/ai-create-flow";
 import {
 	getAiDisabledMessage,
@@ -51,17 +52,14 @@ import { appendImagesDeduped } from "@/lib/multi-image";
 import type { CalendarEvent } from "@/lib/types";
 import {
 	APP_ACTION_BAR_CLASSES,
-	APP_HEADER_SURFACE_CLASSES,
-	APP_NAV_SURFACE_CLASSES,
-	APP_SECTION_SURFACE_CLASSES,
+	getAppHeaderSurfaceClasses,
+	getAppNavSurfaceClasses,
+	getAppSectionSurfaceClasses,
 	getConnectionBadgeClasses,
 } from "@/lib/ui-shell-contract";
 import { useUserSettings } from "@/lib/user-settings";
 import { cn } from "@/lib/utils";
 
-const APP_FRAME_CLASSES =
-	"mx-auto flex min-h-screen w-full max-w-6xl flex-col px-4 pb-24 pt-4 sm:px-6 lg:px-8";
-
 const NAV_BUTTON_CLASSES = "flex-1 gap-2";
 
 const getNavButtonClasses = (isActive: boolean) =>
@@ -83,6 +81,7 @@ const validateImageFile = (file: File): string | null => {
 };
 
 export default function HomePage() {
+	const isMobile = useIsMobile();
 	const [activeView, setActiveView] = useState<"list" | "settings">("list");
 	const [events, setEvents] = useState<CalendarEvent[]>([]);
 	const [dialogOpen, setDialogOpen] = useState(false);
@@ -428,6 +427,18 @@ export default function HomePage() {
 		setDialogOpen(true);
 	};
 
+	const appFrameClasses = cn(
+		"mx-auto flex min-h-screen w-full max-w-6xl flex-col",
+		isMobile ? "px-4 pb-24 pt-4" : "px-8 py-4",
+	);
+	const appHeaderSurfaceClasses = getAppHeaderSurfaceClasses(isMobile);
+	const appSectionSurfaceClasses = getAppSectionSurfaceClasses(isMobile);
+	const appNavSurfaceClasses = getAppNavSurfaceClasses(isMobile);
+	const mainContentClasses = cn(
+		"grid items-start gap-4",
+		isMobile ? "grid-cols-1" : "grid-cols-[minmax(0,0.75fr)_minmax(0,1.25fr)]",
+	);
+
 	return (
 		<DragDropContainer
 			isDragOver={isDragOver}
@@ -435,8 +446,8 @@ export default function HomePage() {
 			onImport={handleImport}
 			onImageDrop={(file) => handleImagesSelect([file])}
 		>
-			<div className={APP_FRAME_CLASSES}>
-				<header className={APP_HEADER_SURFACE_CLASSES}>
+			<div className={appFrameClasses}>
+				<header className={appHeaderSurfaceClasses}>
 					<div className="flex min-w-0 flex-col">
 						<p className="font-mono text-[11px] uppercase text-muted-foreground">
 							Local Calendar
@@ -499,15 +510,15 @@ export default function HomePage() {
 					{activeView === "settings" ? (
 						<SettingsPanel
 							adminAiEnabled={adminAiEnabled}
-							className={APP_SECTION_SURFACE_CLASSES}
+							className={appSectionSurfaceClasses}
 							hasLoadedSettings={hasLoadedSettings}
 							onSettingsChange={updateSettings}
 							settings={settings}
 						/>
 					) : (
-						<section className="grid items-start gap-4 lg:grid-cols-[minmax(0,0.75fr)_minmax(0,1.25fr)]">
-							<div className="order-1 lg:order-none space-y-4">
-								<section className={APP_SECTION_SURFACE_CLASSES}>
+						<section className={mainContentClasses}>
+							<div className="space-y-4">
+								<section className={appSectionSurfaceClasses}>
 									<div className="mb-4 space-y-1">
 										<p className="text-xs font-medium uppercase tracking-[0.18em] text-muted-foreground">
 											AI capture
@@ -543,8 +554,8 @@ export default function HomePage() {
 								</section>
 							</div>
 
-							<div className="order-2 lg:order-none space-y-4">
-								<section className={APP_SECTION_SURFACE_CLASSES}>
+							<div className="space-y-4">
+								<section className={appSectionSurfaceClasses}>
 									<div className="mb-4 flex items-center justify-between gap-3">
 										<div className="space-y-1">
 											<p className="text-xs font-medium uppercase tracking-[0.18em] text-muted-foreground">
@@ -593,7 +604,7 @@ export default function HomePage() {
 					)}
 				</main>
 
-				<nav className={APP_NAV_SURFACE_CLASSES}>
+				<nav className={appNavSurfaceClasses}>
 					<Button
 						type="button"
 						variant="ghost"
diff --git a/src/components/ai-toolbar.tsx b/src/components/ai-toolbar.tsx
index b9a8076..4e0257b 100644
--- a/src/components/ai-toolbar.tsx
+++ b/src/components/ai-toolbar.tsx
@@ -19,6 +19,7 @@ import {
 } from "@/components/ui/popover";
 import { Skeleton } from "@/components/ui/skeleton";
 import { Textarea } from "@/components/ui/textarea";
+import { useIsMobile } from "@/hooks/use-mobile";
 import { extractAllImagesFromClipboard } from "@/lib/clipboard-image";
 import {
 	detectOs,
@@ -114,6 +115,7 @@ export const AIToolbar = ({
 	summaryUpdated,
 	events,
 }: AIToolbarProps) => {
+	const isMobile = useIsMobile();
 	const examplePrompts = [
 		"Lunch with Maya next Thursday at 12:30pm at Toma, remind me 30 minutes before.",
 		"Project sync tomorrow from 9am to 10am on Google Meet with a weekly repeat.",
@@ -281,7 +283,13 @@ export const AIToolbar = ({
 					</div>
 				</div>
 			) : isAuthenticated ? (
-				<div className="grid gap-3 lg:grid-cols-[minmax(0,1fr)_minmax(0,1fr)]">
+				<div
+					className={
+						isMobile
+							? "grid gap-3"
+							: "grid gap-3 grid-cols-[minmax(0,1fr)_minmax(0,1fr)]"
+					}
+				>
 					<div className="space-y-3">
 						<div className="rounded-[10px] bg-card shadow focus-within:ring-[3px] focus-within:ring-ring/20">
 							<Textarea
@@ -347,42 +355,47 @@ export const AIToolbar = ({
 
 						<div className="flex flex-wrap items-center justify-between gap-2">
 							<div className="flex items-center gap-1.5">
-								<HoverCard
-									openDelay={300}
-									closeDelay={100}
-									open={isPopoverOpen ? false : undefined}
-								>
-									<Popover open={isPopoverOpen} onOpenChange={setIsPopoverOpen}>
-										<HoverCardTrigger asChild>
-											<PopoverTrigger asChild>
-												<Button
-													variant="ghost"
-													size="icon"
-													className="hidden h-8 w-8 text-muted-foreground/70 hover:text-foreground md:inline-flex"
-													aria-label="Keyboard shortcuts"
-												>
-													<Info className="h-3.5 w-3.5" />
-												</Button>
-											</PopoverTrigger>
-										</HoverCardTrigger>
-										<PopoverContent
+								{!isMobile ? (
+									<HoverCard
+										openDelay={300}
+										closeDelay={100}
+										open={isPopoverOpen ? false : undefined}
+									>
+										<Popover
+											open={isPopoverOpen}
+											onOpenChange={setIsPopoverOpen}
+										>
+											<HoverCardTrigger asChild>
+												<PopoverTrigger asChild>
+													<Button
+														variant="ghost"
+														size="icon"
+														className="h-8 w-8 text-muted-foreground/70 hover:text-foreground"
+														aria-label="Keyboard shortcuts"
+													>
+														<Info className="h-3.5 w-3.5" />
+													</Button>
+												</PopoverTrigger>
+											</HoverCardTrigger>
+											<PopoverContent
+												align="start"
+												side="top"
+												sideOffset={6}
+												className="w-52 p-3"
+											>
+												<ShortcutsList os={os} />
+											</PopoverContent>
+										</Popover>
+										<HoverCardContent
 											align="start"
 											side="top"
 											sideOffset={6}
 											className="w-52 p-3"
 										>
 											<ShortcutsList os={os} />
-										</PopoverContent>
-									</Popover>
-									<HoverCardContent
-										align="start"
-										side="top"
-										sideOffset={6}
-										className="w-52 p-3"
-									>
-										<ShortcutsList os={os} />
-									</HoverCardContent>
-								</HoverCard>
+										</HoverCardContent>
+									</HoverCard>
+								) : null}
 
 								{events.length > 0 && (
 									<Button
@@ -453,7 +466,9 @@ export const AIToolbar = ({
 									animate={{ opacity: 1, y: 0 }}
 									exit={{ opacity: 0, y: 4 }}
 									transition={{ duration: 0.15 }}
-									className="mt-3 grid gap-2 sm:grid-cols-2"
+									className={
+										isMobile ? "mt-3 grid gap-2" : "mt-3 grid gap-2 grid-cols-2"
+									}
 								>
 									{imagePreviews.map((preview, index) => (
 										<motion.div
diff --git a/src/components/event-dialog.tsx b/src/components/event-dialog.tsx
index e8d3239..868f6f8 100644
--- a/src/components/event-dialog.tsx
+++ b/src/components/event-dialog.tsx
@@ -19,6 +19,7 @@ import {
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
 import { Textarea } from "@/components/ui/textarea";
+import { useIsMobile } from "@/hooks/use-mobile";
 import {
 	type EventFormValues,
 	getDefaultEventFormValues,
@@ -45,6 +46,7 @@ export const EventDialog = ({
 	onSave,
 	onReset,
 }: EventDialogProps) => {
+	const isMobile = useIsMobile();
 	const isAiDraft = dialogSource === "ai" && !editingId;
 	const titleText = editingId
 		? "Edit Event"
@@ -192,7 +194,11 @@ export const EventDialog = ({
 							/>
 						</div>
 
-						<div className="grid grid-cols-1 gap-3 sm:grid-cols-2">
+						<div
+							className={
+								isMobile ? "grid grid-cols-1 gap-3" : "grid grid-cols-2 gap-3"
+							}
+						>
 							<div className="space-y-1.5">
 								<Label htmlFor="event-location">Location</Label>
 								<Controller
@@ -329,7 +335,7 @@ export const EventDialog = ({
 						)}
 					</section>
 
-					<DialogFooter className="gap-2 sm:gap-0">
+					<DialogFooter className={isMobile ? "gap-2" : "gap-0"}>
 						<Button
 							type="button"
 							variant="ghost"
diff --git a/src/components/settings-panel.tsx b/src/components/settings-panel.tsx
index ffb9415..9421c8c 100644
--- a/src/components/settings-panel.tsx
+++ b/src/components/settings-panel.tsx
@@ -1,7 +1,10 @@
+"use client";
+
 import { Sparkles, Zap } from "lucide-react";
 import { Badge } from "@/components/ui/badge";
 import { Checkbox } from "@/components/ui/checkbox";
 import { Label } from "@/components/ui/label";
+import { useIsMobile } from "@/hooks/use-mobile";
 import type { UserSettings } from "@/lib/user-settings";
 import { cn } from "@/lib/utils";
 
@@ -22,6 +25,7 @@ export function SettingsPanel({
 	onSettingsChange,
 	settings,
 }: SettingsPanelProps) {
+	const isMobile = useIsMobile();
 	const valuePrefix = hasLoadedSettings
 		? "Current preference"
 		: "Default value";
@@ -35,7 +39,12 @@ export function SettingsPanel({
 
 	return (
 		<section className={className}>
-			<div className="flex flex-col gap-4 lg:flex-row lg:items-start lg:justify-between">
+			<div
+				className={cn(
+					"gap-4",
+					isMobile ? "flex flex-col" : "flex items-start justify-between",
+				)}
+			>
 				<div className="space-y-1">
 					<p className="text-xs font-semibold uppercase tracking-[0.22em] text-primary">
 						Settings
@@ -51,7 +60,14 @@ export function SettingsPanel({
 				</Badge>
 			</div>
 
-			<div className="mt-5 grid gap-4 lg:grid-cols-[minmax(0,1.7fr)_minmax(18rem,1fr)]">
+			<div
+				className={cn(
+					"mt-5 grid gap-4",
+					isMobile
+						? "grid-cols-1"
+						: "grid-cols-[minmax(0,1.7fr)_minmax(18rem,1fr)]",
+				)}
+			>
 				<div className="grid gap-4">
 					<div className={settingRowClasses}>
 						<div className="flex items-start gap-3">
@@ -149,7 +165,12 @@ export function SettingsPanel({
 							{summaryDescription}
 						</p>
 					</div>
-					<dl className="grid gap-3 sm:grid-cols-2 lg:grid-cols-1">
+					<dl
+						className={cn(
+							"grid gap-3",
+							isMobile ? "grid-cols-1" : "grid-cols-2",
+						)}
+					>
 						<div className="rounded-[8px] bg-secondary p-3 shadow-[inset_0_0_0_1px_var(--color-border)]">
 							<dt className="text-xs font-semibold uppercase tracking-[0.18em] text-muted-foreground">
 								Direct create preference
diff --git a/src/components/ui/calendar.tsx b/src/components/ui/calendar.tsx
index 56f788c..d42a7d3 100644
--- a/src/components/ui/calendar.tsx
+++ b/src/components/ui/calendar.tsx
@@ -12,6 +12,7 @@ import {
 	getDefaultClassNames,
 } from "react-day-picker";
 import { Button, buttonVariants } from "@/components/ui/button";
+import { useIsMobile } from "@/hooks/use-mobile";
 import { cn } from "@/lib/utils";
 
 function Calendar({
@@ -26,6 +27,7 @@ function Calendar({
 }: React.ComponentProps<typeof DayPicker> & {
 	buttonVariant?: React.ComponentProps<typeof Button>["variant"];
 }) {
+	const isMobile = useIsMobile();
 	const defaultClassNames = getDefaultClassNames();
 
 	return (
@@ -46,7 +48,9 @@ function Calendar({
 			classNames={{
 				root: cn("w-fit", defaultClassNames.root),
 				months: cn(
-					"flex gap-4 flex-col md:flex-row relative",
+					isMobile
+						? "relative flex flex-col gap-4"
+						: "relative flex flex-row gap-4",
 					defaultClassNames.months,
 				),
 				month: cn("flex flex-col w-full gap-4", defaultClassNames.month),
diff --git a/src/components/ui/date-picker.tsx b/src/components/ui/date-picker.tsx
index e58ee1f..812ebf6 100644
--- a/src/components/ui/date-picker.tsx
+++ b/src/components/ui/date-picker.tsx
@@ -20,6 +20,7 @@ import {
 	PopoverContent,
 	PopoverTrigger,
 } from "@/components/ui/popover";
+import { useIsMobile } from "@/hooks/use-mobile";
 
 interface DropdownItem {
 	disabled?: boolean;
@@ -28,6 +29,7 @@ interface DropdownItem {
 }
 
 function CalendarDropdown(props: DropdownProps) {
+	const isMobile = useIsMobile();
 	const { options, value, onChange, "aria-label": ariaLabel } = props;
 
 	const items: DropdownItem[] =
@@ -50,35 +52,35 @@ function CalendarDropdown(props: DropdownProps) {
 
 	return (
 		<>
-			<div className="relative flex items-center sm:hidden">
-				<select
-					aria-label={ariaLabel}
-					className="absolute inset-0 z-10 w-full cursor-pointer opacity-0"
-					value={value?.toString() ?? ""}
-					onChange={onChange}
-				>
-					{options?.map((option) => (
-						<option
-							key={option.value}
-							value={option.value}
-							disabled={option.disabled}
-						>
-							{option.label}
-						</option>
-					))}
-				</select>
-				<Button
-					variant="ghost"
-					size="sm"
-					className="pointer-events-none h-8 w-full justify-between gap-2 px-2 font-medium"
-					tabIndex={-1}
-				>
-					{selectedItem?.label}
-					<ChevronDownIcon className="size-4 opacity-50" />
-				</Button>
-			</div>
-
-			<div className="hidden sm:block">
+			{isMobile ? (
+				<div className="relative flex items-center">
+					<select
+						aria-label={ariaLabel}
+						className="absolute inset-0 z-10 w-full cursor-pointer opacity-0"
+						value={value?.toString() ?? ""}
+						onChange={onChange}
+					>
+						{options?.map((option) => (
+							<option
+								key={option.value}
+								value={option.value}
+								disabled={option.disabled}
+							>
+								{option.label}
+							</option>
+						))}
+					</select>
+					<Button
+						variant="ghost"
+						size="sm"
+						className="pointer-events-none h-8 w-full justify-between gap-2 px-2 font-medium"
+						tabIndex={-1}
+					>
+						{selectedItem?.label}
+						<ChevronDownIcon className="size-4 opacity-50" />
+					</Button>
+				</div>
+			) : (
 				<Combobox
 					aria-label={ariaLabel}
 					autoHighlight
@@ -105,7 +107,7 @@ function CalendarDropdown(props: DropdownProps) {
 						</ComboboxList>
 					</ComboboxContent>
 				</Combobox>
-			</div>
+			)}
 		</>
 	);
 }
@@ -139,6 +141,7 @@ export function DatePicker({
 	month: controlledMonth,
 	onMonthChange: controlledOnMonthChange,
 }: DatePickerProps) {
+	const isMobile = useIsMobile();
 	const fallbackId = React.useId();
 	const id = providedId ?? fallbackId;
 
@@ -239,9 +242,21 @@ export function DatePicker({
 		<Popover open={open} onOpenChange={setOpen}>
 			{triggerContent}
 			<PopoverContent className="w-auto p-0" align="start">
-				<div className="flex max-sm:flex-col">
-					<div className="relative py-1 ps-1 max-sm:order-1 max-sm:border-t">
-						<div className="flex h-full flex-col sm:border-e sm:pe-3">
+				<div className={isMobile ? "flex flex-col" : "flex"}>
+					<div
+						className={
+							isMobile
+								? "relative order-1 border-t py-1 ps-1"
+								: "relative py-1 ps-1"
+						}
+					>
+						<div
+							className={
+								isMobile
+									? "flex h-full flex-col"
+									: "flex h-full flex-col border-e pe-3"
+							}
+						>
 							<Button
 								className="w-full justify-start"
 								onClick={() => {
@@ -292,7 +307,7 @@ export function DatePicker({
 						</div>
 					</div>
 					<Calendar
-						className="max-sm:pb-3 sm:ps-2"
+						className={isMobile ? "pb-3" : "ps-2"}
 						mode="single"
 						captionLayout="dropdown"
 						components={{ Dropdown: CalendarDropdown }}
diff --git a/src/components/ui/dialog.tsx b/src/components/ui/dialog.tsx
index 6d61c84..30b980c 100644
--- a/src/components/ui/dialog.tsx
+++ b/src/components/ui/dialog.tsx
@@ -4,6 +4,7 @@ import * as DialogPrimitive from "@radix-ui/react-dialog";
 import { XIcon } from "lucide-react";
 import type * as React from "react";
 
+import { useIsMobile } from "@/hooks/use-mobile";
 import { cn } from "@/lib/utils";
 
 function Dialog({
@@ -54,13 +55,16 @@ function DialogContent({
 }: React.ComponentProps<typeof DialogPrimitive.Content> & {
 	showCloseButton?: boolean;
 }) {
+	const isMobile = useIsMobile();
+
 	return (
 		<DialogPortal data-slot="dialog-portal">
 			<DialogOverlay />
 			<DialogPrimitive.Content
 				data-slot="dialog-content"
 				className={cn(
-					"bg-card text-card-foreground data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 fixed top-[50%] left-[50%] z-50 grid w-full max-w-[calc(100%-2rem)] translate-x-[-50%] translate-y-[-50%] gap-5 rounded-[10px] p-6 shadow-xl duration-200 sm:max-w-lg",
+					"bg-card text-card-foreground data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 fixed top-[50%] left-[50%] z-50 grid w-full max-w-[calc(100%-2rem)] translate-x-[-50%] translate-y-[-50%] gap-5 rounded-[10px] p-6 shadow-xl duration-200",
+					isMobile ? undefined : "max-w-lg",
 					className,
 				)}
 				{...props}
@@ -91,11 +95,15 @@ function DialogHeader({ className, ...props }: React.ComponentProps<"div">) {
 }
 
 function DialogFooter({ className, ...props }: React.ComponentProps<"div">) {
+	const isMobile = useIsMobile();
+
 	return (
 		<div
 			data-slot="dialog-footer"
 			className={cn(
-				"flex flex-col-reverse gap-2 sm:flex-row sm:justify-end",
+				isMobile
+					? "flex flex-col-reverse gap-2"
+					: "flex flex-row justify-end gap-2",
 				className,
 			)}
 			{...props}
diff --git a/src/components/ui/input-group.tsx b/src/components/ui/input-group.tsx
index 3a3614c..94aeb6d 100644
--- a/src/components/ui/input-group.tsx
+++ b/src/components/ui/input-group.tsx
@@ -4,37 +4,53 @@ import { cva, type VariantProps } from "class-variance-authority";
 import type * as React from "react";
 import { Input } from "@/components/ui/input";
 import { Textarea } from "@/components/ui/textarea";
+import { useIsMobile } from "@/hooks/use-mobile";
 import { cn } from "@/lib/utils";
 
-const inputGroupAddonVariants = cva(
-	"flex h-auto cursor-text select-none items-center justify-center gap-2 leading-none [&>kbd]:rounded-[calc(var(--radius)-5px)] in-[[data-slot=input-group]:has([data-slot=input-control],[data-slot=textarea-control])]:[&_svg:not([class*='size-'])]:size-4.5 sm:in-[[data-slot=input-group]:has([data-slot=input-control],[data-slot=textarea-control])]:[&_svg:not([class*='size-'])]:size-4 [&_svg]:-mx-0.5 not-has-[button]:**:[svg:not([class*='opacity-'])]:opacity-80",
-	{
-		defaultVariants: {
-			align: "inline-start",
-		},
-		variants: {
-			align: {
-				"block-end":
-					"order-last w-full justify-start px-[calc(--spacing(3)-1px)] pb-[calc(--spacing(3)-1px)] [.border-t]:pt-[calc(--spacing(3)-1px)] [[data-size=sm]+&]:px-[calc(--spacing(2.5)-1px)]",
-				"block-start":
-					"order-first w-full justify-start px-[calc(--spacing(3)-1px)] pt-[calc(--spacing(3)-1px)] [.border-b]:pb-[calc(--spacing(3)-1px)] [[data-size=sm]+&]:px-[calc(--spacing(2.5)-1px)]",
-				"inline-end":
-					"order-last pe-[calc(--spacing(3)-1px)] has-[>:last-child[data-slot=badge]]:-me-1.5 has-[>button]:-me-2 has-[>kbd:last-child]:me-[-0.35rem] [[data-size=sm]+&]:pe-[calc(--spacing(2.5)-1px)]",
-				"inline-start":
-					"order-first ps-[calc(--spacing(3)-1px)] has-[>:last-child[data-slot=badge]]:-ms-1.5 has-[>button]:-ms-2 has-[>kbd:last-child]:ms-[-0.35rem] [[data-size=sm]+&]:ps-[calc(--spacing(2.5)-1px)]",
-			},
+const inputGroupAddonBaseClasses =
+	"flex h-auto cursor-text select-none items-center justify-center gap-2 leading-none [&>kbd]:rounded-[calc(var(--radius)-5px)] [&_svg]:-mx-0.5 not-has-[button]:**:[svg:not([class*='opacity-'])]:opacity-80";
+
+const inputGroupRootBaseClasses =
+	"relative inline-flex w-full min-w-0 items-center rounded-lg border border-input bg-background not-dark:bg-clip-padding text-foreground shadow-xs/5 ring-ring/24 transition-shadow before:pointer-events-none before:absolute before:inset-0 before:rounded-[calc(var(--radius-lg)-1px)] not-has-[input:disabled,textarea:disabled]:not-has-[input:focus-visible,textarea:focus-visible]:not-has-[input[aria-invalid],textarea[aria-invalid]]:before:shadow-[0_1px_--theme(--color-black/4%)] has-[input:focus-visible,textarea:focus-visible]:has-[input[aria-invalid],textarea[aria-invalid]]:border-destructive/64 has-[input:focus-visible,textarea:focus-visible]:has-[input[aria-invalid],textarea[aria-invalid]]:ring-destructive/16 has-[textarea]:h-auto has-data-[align=block-end]:h-auto has-data-[align=block-start]:h-auto has-data-[align=block-end]:flex-col has-data-[align=block-start]:flex-col has-[input:focus-visible,textarea:focus-visible]:border-ring has-[input[aria-invalid],textarea[aria-invalid]]:border-destructive/36 has-autofill:bg-foreground/4 has-[input:disabled,textarea:disabled]:opacity-64 has-[input:disabled,textarea:disabled,input:focus-visible,textarea:focus-visible,input[aria-invalid],textarea[aria-invalid]]:shadow-none has-[input:focus-visible,textarea:focus-visible]:ring-[3px] dark:bg-input/32 dark:has-autofill:bg-foreground/8 dark:has-[input[aria-invalid],textarea[aria-invalid]]:ring-destructive/24 dark:not-has-[input:disabled,textarea:disabled]:not-has-[input:focus-visible,textarea:focus-visible]:not-has-[input[aria-invalid],textarea[aria-invalid]]:before:shadow-[0_-1px_--theme(--color-white/6%)] has-data-[align=inline-start]:**:[[data-size=sm]_input]:ps-1.5 has-data-[align=inline-end]:**:[[data-size=sm]_input]:pe-1.5 *:[[data-slot=input-control],[data-slot=textarea-control]]:contents *:[[data-slot=input-control],[data-slot=textarea-control]]:before:hidden has-[[data-align=block-start],[data-align=block-end]]:**:[input]:h-auto has-data-[align=inline-start]:**:[[data-size=sm]_textarea]:ps-1.5 has-data-[align=inline-end]:**:[[data-size=sm]_textarea]:pe-1.5 has-[[data-align=block-start],[data-align=block-end]]:**:[textarea]:h-auto";
+
+const inputGroupTextBaseClasses =
+	"line-clamp-1 flex items-center gap-2 whitespace-nowrap text-muted-foreground leading-none [&_svg]:pointer-events-none [&_svg]:-mx-0.5";
+
+const inputGroupAddonVariants = cva(inputGroupAddonBaseClasses, {
+	defaultVariants: {
+		align: "inline-start",
+	},
+	variants: {
+		align: {
+			"block-end":
+				"order-last w-full justify-start px-[calc(--spacing(3)-1px)] pb-[calc(--spacing(3)-1px)] [.border-t]:pt-[calc(--spacing(3)-1px)] [[data-size=sm]+&]:px-[calc(--spacing(2.5)-1px)]",
+			"block-start":
+				"order-first w-full justify-start px-[calc(--spacing(3)-1px)] pt-[calc(--spacing(3)-1px)] [.border-b]:pb-[calc(--spacing(3)-1px)] [[data-size=sm]+&]:px-[calc(--spacing(2.5)-1px)]",
+			"inline-end":
+				"order-last pe-[calc(--spacing(3)-1px)] has-[>:last-child[data-slot=badge]]:-me-1.5 has-[>button]:-me-2 has-[>kbd:last-child]:me-[-0.35rem] [[data-size=sm]+&]:pe-[calc(--spacing(2.5)-1px)]",
+			"inline-start":
+				"order-first ps-[calc(--spacing(3)-1px)] has-[>:last-child[data-slot=badge]]:-ms-1.5 has-[>button]:-ms-2 has-[>kbd:last-child]:ms-[-0.35rem] [[data-size=sm]+&]:ps-[calc(--spacing(2.5)-1px)]",
 		},
 	},
-);
+});
+
+function getAddonResponsiveClasses(isMobile: boolean) {
+	return isMobile
+		? "in-[[data-slot=input-group]:has([data-slot=input-control],[data-slot=textarea-control])]:[&_svg:not([class*='size-'])]:size-4.5"
+		: "in-[[data-slot=input-group]:has([data-slot=input-control],[data-slot=textarea-control])]:[&_svg:not([class*='size-'])]:size-4";
+}
 
 export function InputGroup({
 	className,
 	...props
 }: React.ComponentProps<"div">): React.ReactElement {
+	const isMobile = useIsMobile();
+
 	return (
 		<div
 			className={cn(
-				"relative inline-flex w-full min-w-0 items-center rounded-lg border border-input bg-background not-dark:bg-clip-padding text-base text-foreground shadow-xs/5 ring-ring/24 transition-shadow before:pointer-events-none before:absolute before:inset-0 before:rounded-[calc(var(--radius-lg)-1px)] not-has-[input:disabled,textarea:disabled]:not-has-[input:focus-visible,textarea:focus-visible]:not-has-[input[aria-invalid],textarea[aria-invalid]]:before:shadow-[0_1px_--theme(--color-black/4%)] has-[input:focus-visible,textarea:focus-visible]:has-[input[aria-invalid],textarea[aria-invalid]]:border-destructive/64 has-[input:focus-visible,textarea:focus-visible]:has-[input[aria-invalid],textarea[aria-invalid]]:ring-destructive/16 has-[textarea]:h-auto has-data-[align=block-end]:h-auto has-data-[align=block-start]:h-auto has-data-[align=block-end]:flex-col has-data-[align=block-start]:flex-col has-[input:focus-visible,textarea:focus-visible]:border-ring has-[input[aria-invalid],textarea[aria-invalid]]:border-destructive/36 has-autofill:bg-foreground/4 has-[input:disabled,textarea:disabled]:opacity-64 has-[input:disabled,textarea:disabled,input:focus-visible,textarea:focus-visible,input[aria-invalid],textarea[aria-invalid]]:shadow-none has-[input:focus-visible,textarea:focus-visible]:ring-[3px] sm:text-sm dark:bg-input/32 dark:has-autofill:bg-foreground/8 dark:has-[input[aria-invalid],textarea[aria-invalid]]:ring-destructive/24 dark:not-has-[input:disabled,textarea:disabled]:not-has-[input:focus-visible,textarea:focus-visible]:not-has-[input[aria-invalid],textarea[aria-invalid]]:before:shadow-[0_-1px_--theme(--color-white/6%)] has-data-[align=inline-start]:**:[[data-size=sm]_input]:ps-1.5 has-data-[align=inline-end]:**:[[data-size=sm]_input]:pe-1.5 *:[[data-slot=input-control],[data-slot=textarea-control]]:contents *:[[data-slot=input-control],[data-slot=textarea-control]]:before:hidden has-[[data-align=block-start],[data-align=block-end]]:**:[input]:h-auto has-data-[align=inline-start]:**:[input]:ps-2 has-data-[align=inline-end]:**:[input]:pe-2 has-data-[align=block-end]:**:[input]:pt-1.5 has-data-[align=block-start]:**:[input]:pb-1.5 **:[textarea]:min-h-20.5 **:[textarea]:resize-none **:[textarea]:py-[calc(--spacing(3)-1px)] **:[textarea]:max-sm:min-h-23.5 **:[textarea_button]:rounded-[calc(var(--radius-md)-1px)]",
+				inputGroupRootBaseClasses,
+				isMobile ? "text-base" : "text-sm",
 				className,
 			)}
 			data-slot="input-group"
@@ -49,9 +65,15 @@ export function InputGroupAddon({
 	...props
 }: React.ComponentProps<"div"> &
 	VariantProps<typeof inputGroupAddonVariants>): React.ReactElement {
+	const isMobile = useIsMobile();
+
 	return (
 		<div
-			className={cn(inputGroupAddonVariants({ align }), className)}
+			className={cn(
+				inputGroupAddonVariants({ align }),
+				getAddonResponsiveClasses(isMobile),
+				className,
+			)}
 			data-align={align}
 			data-slot="input-group-addon"
 			{...props}
@@ -63,10 +85,13 @@ export function InputGroupText({
 	className,
 	...props
 }: React.ComponentProps<"span">): React.ReactElement {
+	const isMobile = useIsMobile();
+
 	return (
 		<span
 			className={cn(
-				"line-clamp-1 flex items-center gap-2 whitespace-nowrap text-muted-foreground leading-none in-[[data-slot=input-group]:has([data-slot=input-control],[data-slot=textarea-control])]:[&_svg:not([class*='size-'])]:size-4.5 sm:in-[[data-slot=input-group]:has([data-slot=input-control],[data-slot=textarea-control])]:[&_svg:not([class*='size-'])]:size-4 [&_svg]:pointer-events-none [&_svg]:-mx-0.5",
+				inputGroupTextBaseClasses,
+				getAddonResponsiveClasses(isMobile),
 				className,
 			)}
 			{...props}
diff --git a/src/components/ui/textarea.tsx b/src/components/ui/textarea.tsx
index db39d6d..a45ffda 100644
--- a/src/components/ui/textarea.tsx
+++ b/src/components/ui/textarea.tsx
@@ -1,13 +1,19 @@
+"use client";
+
 import type * as React from "react";
 
+import { useIsMobile } from "@/hooks/use-mobile";
 import { cn } from "@/lib/utils";
 
 function Textarea({ className, ...props }: React.ComponentProps<"textarea">) {
+	const isMobile = useIsMobile();
+
 	return (
 		<textarea
 			data-slot="textarea"
 			className={cn(
-				"placeholder:text-muted-foreground aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 flex field-sizing-content min-h-16 w-full rounded-[8px] bg-secondary px-3 py-2 text-base shadow-sm transition-[color,box-shadow] outline-none focus-visible:ring-[3px] focus-visible:ring-ring/25 disabled:cursor-not-allowed disabled:opacity-50 md:text-sm",
+				"placeholder:text-muted-foreground aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 flex field-sizing-content min-h-16 w-full rounded-[8px] bg-secondary px-3 py-2 shadow-sm transition-[color,box-shadow] outline-none focus-visible:ring-[3px] focus-visible:ring-ring/25 disabled:cursor-not-allowed disabled:opacity-50",
+				isMobile ? "text-base" : "text-sm",
 				className,
 			)}
 			{...props}
diff --git a/src/lib/ui-shell-contract.ts b/src/lib/ui-shell-contract.ts
index 56ef8b2..cabc495 100644
--- a/src/lib/ui-shell-contract.ts
+++ b/src/lib/ui-shell-contract.ts
@@ -1,16 +1,22 @@
 import { cn } from "@/lib/utils";
 
-export const APP_HEADER_SURFACE_CLASSES =
-	"mb-6 flex min-h-14 items-center justify-between gap-3 bg-background/95 px-4 py-3 shadow-[inset_0_-1px_0_0_var(--color-border)] sm:px-6";
+export const getAppHeaderSurfaceClasses = (isMobile: boolean) =>
+	cn(
+		"mb-6 flex min-h-14 items-center justify-between gap-3 bg-background/95 py-3 shadow-[inset_0_-1px_0_0_var(--color-border)]",
+		isMobile ? "px-4" : "px-6",
+	);
 
-export const APP_SECTION_SURFACE_CLASSES =
-	"rounded-[10px] bg-card px-4 py-4 shadow sm:px-5";
+export const getAppSectionSurfaceClasses = (isMobile: boolean) =>
+	cn("rounded-[10px] bg-card py-4 shadow", isMobile ? "px-4" : "px-5");
 
 export const APP_ACTION_BAR_CLASSES =
 	"rounded-[10px] bg-secondary px-3 py-3 shadow-sm";
 
-export const APP_NAV_SURFACE_CLASSES =
-	"fixed inset-x-4 bottom-4 mx-auto flex max-w-3xl items-center justify-between rounded-[10px] bg-card/95 px-3 py-2 shadow-lg sm:inset-x-6 lg:hidden";
+export const getAppNavSurfaceClasses = (isMobile: boolean) =>
+	cn(
+		"mx-auto max-w-3xl items-center justify-between rounded-[10px] bg-card/95 px-3 py-2 shadow-lg",
+		isMobile ? "fixed inset-x-4 bottom-4 flex" : "hidden",
+	);
 
 const CONNECTION_BADGE_BASE_CLASSES =
 	"gap-1.5 rounded-full px-2.5 py-1 text-xs font-medium shadow-sm";
diff --git a/tests/ai-toolbar.test.ts b/tests/ai-toolbar.test.ts
index 045930b..6da65a6 100644
--- a/tests/ai-toolbar.test.ts
+++ b/tests/ai-toolbar.test.ts
@@ -159,10 +159,11 @@ describe("Event count badge – positioning contract", () => {
 });
 
 describe("AI capture redesign", () => {
-	test("desktop composer treats prompt and attachments as peer panels", () => {
+	test("composer layout is driven by useIsMobile instead of Tailwind breakpoint classes", () => {
 		const source = readToolbarSource();
 
-		expect(source).toContain("lg:grid-cols-[minmax(0,1fr)_minmax(0,1fr)]");
+		expect(source).toContain("useIsMobile");
+		expect(source).not.toContain("lg:grid-cols-");
 	});
 
 	test("attachments panel is a first-class surfaced region, not an inline footer affordance", () => {
@@ -191,8 +192,8 @@ const ATTACH_BTN_CLASSES = "gap-1.5 text-xs";
 /** Generate button: right side, primary variant, labeled */
 const GENERATE_BTN_CLASSES = "gap-1.5 text-xs";
 
-/** Info popover trigger: hidden on mobile, small on desktop so it stays secondary */
-const INFO_TRIGGER_CLASSES = "hidden h-6 w-6 md:inline-flex";
+/** Info popover trigger: compact affordance that only renders in desktop branches */
+const INFO_TRIGGER_CLASSES = "h-8 w-8 text-muted-foreground/70 hover:text-foreground";
 
 describe("Composer footer bar – layout contract", () => {
 	test("footer row uses justify-between so Attach sits left and Generate sits right", () => {
@@ -223,16 +224,15 @@ describe("Composer footer bar – layout contract", () => {
 });
 
 describe("Info popover trigger – size contract", () => {
-	test("info trigger is hidden on mobile so keyboard-only guidance does not appear in touch layouts", () => {
-		const resolved = cn(INFO_TRIGGER_CLASSES);
-		expect(resolved).toContain("hidden");
-		expect(resolved).toContain("md:inline-flex");
+	test("info trigger is guarded by useIsMobile so keyboard-only guidance stays out of touch layouts", () => {
+		const source = readToolbarSource();
+		expect(source).toContain("!isMobile ? (");
 	});
 
-	test("info trigger is small (h-6 w-6) so it doesn't compete with Generate", () => {
+	test("info trigger stays visually secondary when rendered on desktop", () => {
 		const resolved = cn(INFO_TRIGGER_CLASSES);
-		expect(resolved).toContain("h-6");
-		expect(resolved).toContain("w-6");
+		expect(resolved).toContain("h-8");
+		expect(resolved).toContain("w-8");
 	});
 });
 
@@ -328,7 +328,7 @@ describe("Multi-image strip – layout contract", () => {
 
 describe("AI textarea – prompt input spacing contract", () => {
 	const TEXTAREA_BASE =
-		"border-input placeholder:text-muted-foreground focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive dark:bg-input/30 flex field-sizing-content min-h-16 w-full rounded-md border bg-transparent px-3 py-2 text-base shadow-xs transition-[color,box-shadow] outline-none focus-visible:ring-[3px] disabled:cursor-not-allowed disabled:opacity-50 md:text-sm";
+		"border-input placeholder:text-muted-foreground focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive dark:bg-input/30 flex field-sizing-content min-h-16 w-full rounded-md border bg-transparent px-3 py-2 text-base shadow-xs transition-[color,box-shadow] outline-none focus-visible:ring-[3px] disabled:cursor-not-allowed disabled:opacity-50";
 
 	const AI_TEXTAREA_OVERRIDE =
 		"wrap-anywhere field-sizing-content resize-none w-full min-h-[2.5rem] max-h-64 overflow-y-auto bg-transparent border-0 shadow-none focus-visible:ring-0 focus-visible:ring-offset-0 px-3 py-1 text-sm placeholder:text-muted-foreground/60 placeholder:italic";
diff --git a/tests/home-page-layout.test.ts b/tests/home-page-layout.test.ts
index bb97dbf..8610db6 100644
--- a/tests/home-page-layout.test.ts
+++ b/tests/home-page-layout.test.ts
@@ -2,12 +2,11 @@ import { describe, expect, test } from "bun:test";
 import { readFileSync } from "node:fs";
 
 describe("home page hierarchy", () => {
-	test("desktop layout defines aligned AI and timeline top-row sections", () => {
+	test("desktop layout is selected with useIsMobile rather than Tailwind breakpoint classes", () => {
 		const source = readFileSync("src/app/page.tsx", "utf8");
 
-		expect(source).toContain(
-			"lg:grid-cols-[minmax(0,0.75fr)_minmax(0,1.25fr)]",
-		);
+		expect(source).toContain("useIsMobile");
+		expect(source).toContain("grid-cols-[minmax(0,0.75fr)_minmax(0,1.25fr)]");
 		expect(source).toContain("AI capture");
 		expect(source).toContain("Event timeline");
 	});
@@ -19,10 +18,10 @@ describe("home page hierarchy", () => {
 		expect(source).not.toContain("New Event</button>");
 	});
 
-	test("mobile layout keeps capture before timeline and keeps manual create secondary", () => {
+	test("mobile layout keeps capture before timeline without order utility breakpoints", () => {
 		const source = readFileSync("src/app/page.tsx", "utf8");
 
-		expect(source).toContain("order-1 lg:order-none");
+		expect(source).not.toContain("order-1 lg:order-none");
 		expect(source).toContain("Import");
 		expect(source).toContain("Manual create");
 	});
diff --git a/tests/mobile-hook-adoption.test.ts b/tests/mobile-hook-adoption.test.ts
new file mode 100644
index 0000000..3a8d4e4
--- /dev/null
+++ b/tests/mobile-hook-adoption.test.ts
@@ -0,0 +1,58 @@
+import { describe, expect, test } from "bun:test";
+import { readFileSync } from "node:fs";
+
+const RESPONSIVE_PREFIX_PATTERN = /\b(?:max-sm|sm:|md:|lg:|xl:|2xl:)/;
+
+const HOOK_DRIVEN_FILES = [
+	"src/app/page.tsx",
+	"src/app/demo/combined-date-picker/page.tsx",
+	"src/components/ai-toolbar.tsx",
+	"src/components/event-dialog.tsx",
+	"src/components/settings-panel.tsx",
+	"src/components/ui/calendar.tsx",
+	"src/components/ui/date-picker.tsx",
+	"src/components/ui/dialog.tsx",
+	"src/components/ui/input-group.tsx",
+	"src/components/ui/textarea.tsx",
+	"src/lib/ui-shell-contract.ts",
+];
+
+const DIRECT_HOOK_FILES = [
+	"src/app/page.tsx",
+	"src/app/demo/combined-date-picker/page.tsx",
+	"src/components/ai-toolbar.tsx",
+	"src/components/event-dialog.tsx",
+	"src/components/settings-panel.tsx",
+	"src/components/ui/calendar.tsx",
+	"src/components/ui/date-picker.tsx",
+	"src/components/ui/dialog.tsx",
+	"src/components/ui/input-group.tsx",
+	"src/components/ui/textarea.tsx",
+];
+
+const BOOLEAN_HELPER_FILES = [
+	"src/lib/ui-shell-contract.ts",
+];
+
+describe("mobile hook adoption", () => {
+	test("responsive source files stop using Tailwind breakpoint prefixes for mobile behavior", () => {
+		for (const filePath of HOOK_DRIVEN_FILES) {
+			const source = readFileSync(filePath, "utf8");
+			expect(source).not.toMatch(RESPONSIVE_PREFIX_PATTERN);
+		}
+	});
+
+	test("mobile-responsive component files explicitly depend on the shared useIsMobile hook", () => {
+		for (const filePath of DIRECT_HOOK_FILES) {
+			const source = readFileSync(filePath, "utf8");
+			expect(source).toContain("useIsMobile");
+		}
+	});
+
+	test("utility files accept isMobile booleans instead of embedding breakpoint strings", () => {
+		for (const filePath of BOOLEAN_HELPER_FILES) {
+			const source = readFileSync(filePath, "utf8");
+			expect(source).toContain("isMobile");
+		}
+	});
+});
diff --git a/tests/textarea.test.ts b/tests/textarea.test.ts
index 5a015eb..c21db51 100644
--- a/tests/textarea.test.ts
+++ b/tests/textarea.test.ts
@@ -16,7 +16,7 @@ import { cn } from "@/lib/utils";
 // The base Textarea classes (copied from the component — this is the source of
 // truth we are locking down).
 const TEXTAREA_BASE =
-	"border-input placeholder:text-muted-foreground focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive dark:bg-input/30 flex field-sizing-content min-h-16 w-full rounded-md border bg-transparent px-3 py-2 text-base shadow-xs transition-[color,box-shadow] outline-none focus-visible:ring-[3px] disabled:cursor-not-allowed disabled:opacity-50 md:text-sm";
+	"border-input placeholder:text-muted-foreground focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive dark:bg-input/30 flex field-sizing-content min-h-16 w-full rounded-md border bg-transparent px-3 py-2 text-base shadow-xs transition-[color,box-shadow] outline-none focus-visible:ring-[3px] disabled:cursor-not-allowed disabled:opacity-50";
 
 describe("Textarea – placeholder spacing (base defaults)", () => {
 	test("base className includes horizontal padding px-3 so placeholder is not flush", () => {
diff --git a/tests/ui-shell-contract.test.ts b/tests/ui-shell-contract.test.ts
index 3a191fc..ede89c1 100644
--- a/tests/ui-shell-contract.test.ts
+++ b/tests/ui-shell-contract.test.ts
@@ -1,30 +1,39 @@
 import { describe, expect, test } from "bun:test";
 import {
 	APP_ACTION_BAR_CLASSES,
-	APP_HEADER_SURFACE_CLASSES,
-	APP_NAV_SURFACE_CLASSES,
-	APP_SECTION_SURFACE_CLASSES,
+	getAppHeaderSurfaceClasses,
+	getAppNavSurfaceClasses,
+	getAppSectionSurfaceClasses,
 	getConnectionBadgeClasses,
 } from "@/lib/ui-shell-contract";
 import { EVENT_CARD_SURFACE_CLASSES } from "@/components/event-card";
 
 describe("app shell surfaces", () => {
 	test("header surface is a thin structural bar instead of a glass panel", () => {
-		expect(APP_HEADER_SURFACE_CLASSES).toContain("min-h-14");
-		expect(APP_HEADER_SURFACE_CLASSES).toContain("shadow-[inset_0_-1px_0_0_var(--color-border)]");
-		expect(APP_HEADER_SURFACE_CLASSES).not.toContain("glass-surface");
+		const mobileHeaderClasses = getAppHeaderSurfaceClasses(true);
+
+		expect(mobileHeaderClasses).toContain("min-h-14");
+		expect(mobileHeaderClasses).toContain("shadow-[inset_0_-1px_0_0_var(--color-border)]");
+		expect(mobileHeaderClasses).not.toContain("glass-surface");
 	});
 
 	test("section and action surfaces use tokenized shell classes instead of frozen light-mode shadows", () => {
-		expect(APP_SECTION_SURFACE_CLASSES).not.toContain("glass-panel");
+		const mobileSectionClasses = getAppSectionSurfaceClasses(true);
+		const mobileNavClasses = getAppNavSurfaceClasses(true);
+
+		expect(mobileSectionClasses).not.toContain("glass-panel");
 		expect(APP_ACTION_BAR_CLASSES).not.toContain("glass-subtle");
-		expect(APP_NAV_SURFACE_CLASSES).not.toContain("glass-surface");
-		expect(APP_SECTION_SURFACE_CLASSES).toContain("shadow");
-		expect(APP_SECTION_SURFACE_CLASSES).not.toContain("rgba(0,0,0,0.08)");
+		expect(mobileNavClasses).not.toContain("glass-surface");
+		expect(mobileSectionClasses).toContain("shadow");
+		expect(mobileSectionClasses).not.toContain("rgba(0,0,0,0.08)");
 		expect(APP_ACTION_BAR_CLASSES).toContain("shadow-sm");
 		expect(APP_ACTION_BAR_CLASSES).not.toContain("rgba(0,0,0,0.08)");
-		expect(APP_NAV_SURFACE_CLASSES).toContain("shadow-lg");
-		expect(APP_NAV_SURFACE_CLASSES).not.toContain("rgba(0,0,0,0.08)");
+		expect(mobileNavClasses).toContain("shadow-lg");
+		expect(mobileNavClasses).not.toContain("rgba(0,0,0,0.08)");
+	});
+
+	test("desktop nav surface is suppressed when useIsMobile resolves false", () => {
+		expect(getAppNavSurfaceClasses(false)).toContain("hidden");
 	});
 });