chore: fix TS alias resolution and SVG mocking for test setup

Reviewed-on: #36

.gitea/workflows/workflow.yml

@@ -41,7 +41,13 @@ jobs:
         run: yarn lint
 
       - name: Type Check
-        run: yarn check:shadcn-excluded
+        run: yarn check
+
+      - name: Run Unit Tests
+        run: yarn test:unit
+
+      - name: Run Component Tests
+        run: yarn test:component
 
   publish:
     needs: build # Only runs if tests/lint pass

.storybook/Decorator.svelte

@@ -4,12 +4,11 @@
 
     This provides:
     - ResponsiveManager context for breakpoint tracking
-    - TooltipProvider for shadcn Tooltip components
+    - TooltipProvider for tooltip components
 -->
 <script lang="ts">
 import { createResponsiveManager } from '$shared/lib';
 import type { ResponsiveManager } from '$shared/lib';
-import { Provider as TooltipProvider } from '$shared/shadcn/ui/tooltip';
 import { setContext } from 'svelte';
 
 interface Props {
@@ -24,6 +23,4 @@ $effect(() => responsiveManager.init());
 setContext<ResponsiveManager>('responsive', responsiveManager);
 </script>
 
-<TooltipProvider delayDuration={200} skipDelayDuration={300}>
-    {@render children()}
-</TooltipProvider>
+{@render children()}

.storybook/StoryStage.svelte

@@ -1,14 +1,18 @@
 <script lang="ts">
 interface Props {
     children: import('svelte').Snippet;
-    width?: string; // Optional width override
+    /**
+     * Tailwind max-width class applied to the card, or 'none' to remove width constraint.
+     * @default 'max-w-3xl'
+     */
+    maxWidth?: string;
 }
 
-let { children, width = 'max-w-3xl' }: Props = $props();
+let { children, maxWidth = 'max-w-3xl' }: Props = $props();
 </script>
 
 <div class="flex min-h-screen w-full items-center justify-center bg-background p-8">
-    <div class="w-full bg-card shadow-lg ring-1 ring-border rounded-xl p-12 {width}">
+    <div class="w-full bg-card shadow-lg ring-1 ring-border rounded-xl p-12 {maxWidth !== 'none' ? maxWidth : ''}">
         <div class="relative flex justify-center items-center text-foreground">
             {@render children()}
         </div>

.storybook/preview.ts

@@ -5,68 +5,6 @@ import ThemeDecorator from './ThemeDecorator.svelte';
 import '../src/app/styles/app.css';
 
 const preview: Preview = {
-    globalTypes: {
-        viewport: {
-            description: 'Viewport size for responsive design',
-            defaultValue: 'widgetWide',
-            toolbar: {
-                icon: 'view',
-                items: [
-                    {
-                        value: 'reset',
-                        icon: 'refresh',
-                        title: 'Reset viewport',
-                    },
-                    {
-                        value: 'mobile1',
-                        icon: 'mobile',
-                        title: 'iPhone 5/SE',
-                    },
-                    {
-                        value: 'mobile2',
-                        icon: 'mobile',
-                        title: 'iPhone 14 Pro Max',
-                    },
-                    {
-                        value: 'tablet',
-                        icon: 'tablet',
-                        title: 'iPad (Portrait)',
-                    },
-                    {
-                        value: 'desktop',
-                        icon: 'desktop',
-                        title: 'Desktop (Small)',
-                    },
-                    {
-                        value: 'widgetMedium',
-                        icon: 'view',
-                        title: 'Widget Medium',
-                    },
-                    {
-                        value: 'widgetWide',
-                        icon: 'view',
-                        title: 'Widget Wide',
-                    },
-                    {
-                        value: 'widgetExtraWide',
-                        icon: 'view',
-                        title: 'Widget Extra Wide',
-                    },
-                    {
-                        value: 'fullWidth',
-                        icon: 'view',
-                        title: 'Full Width',
-                    },
-                    {
-                        value: 'fullScreen',
-                        icon: 'expand',
-                        title: 'Full Screen',
-                    },
-                ],
-                dynamicTitle: true,
-            },
-        },
-    },
     parameters: {
         layout: 'padded',
         controls: {
@@ -195,10 +133,11 @@ const preview: Preview = {
             },
         }),
         // Wrap with StoryStage for presentation styling
-        story => ({
+        (story, context) => ({
             Component: StoryStage,
             props: {
                 children: story(),
+                maxWidth: context.parameters.storyStage?.maxWidth,
             },
         }),
     ],

README.md

@@ -8,14 +8,14 @@ A modern font exploration and comparison tool for browsing fonts from Google Fon
 - **Side-by-Side Comparison**: Compare up to 4 fonts simultaneously with customizable text, size, and typography settings
 - **Advanced Filtering**: Filter by category, provider, character subsets, and weight
 - **Virtual Scrolling**: Fast, smooth browsing of thousands of fonts
-- **Responsive UI**: Beautiful interface built with shadcn components and Tailwind CSS
+- **Responsive UI**: Beautiful interface built with Tailwind CSS
 - **Type-Safe**: Full TypeScript coverage with strict mode enabled
 
 ## Tech Stack
 
 - **Framework**: Svelte 5 with reactive primitives (runes)
 - **Styling**: Tailwind CSS v4
-- **Components**: shadcn-svelte (via bits-ui)
+- **Components**: Bits UI primitives
 - **State Management**: TanStack Query for async data
 - **Architecture**: Feature-Sliced Design (FSD)
 - **Quality**: oxlint (linting), dprint (formatting), lefthook (git hooks)

components.json

@@ -1,16 +0,0 @@
-{
-  "$schema": "https://shadcn-svelte.com/schema.json",
-  "tailwind": {
-    "css": "src/app.css",
-    "baseColor": "zinc"
-  },
-  "aliases": {
-    "components": "$shared/shadcn/ui",
-    "utils": "$shared/shadcn/utils/shadcn-utils",
-    "ui": "$shared/shadcn/ui",
-    "hooks": "$shared/shadcn/hooks",
-    "lib": "$shared"
-  },
-  "typescript": true,
-  "registry": "https://shadcn-svelte.com/registry"
-}

dprint.json

@@ -31,7 +31,17 @@
     "importDeclaration.forceMultiLine": "whenMultiple",
     "importDeclaration.forceSingleLine": false,
     "exportDeclaration.forceMultiLine": "whenMultiple",
-    "exportDeclaration.forceSingleLine": false
+    "exportDeclaration.forceSingleLine": false,
+    "ifStatement.useBraces": "always",
+    "ifStatement.singleBodyPosition": "nextLine",
+    "whileStatement.useBraces": "always",
+    "whileStatement.singleBodyPosition": "nextLine",
+    "forStatement.useBraces": "always",
+    "forStatement.singleBodyPosition": "nextLine",
+    "forInStatement.useBraces": "always",
+    "forInStatement.singleBodyPosition": "nextLine",
+    "forOfStatement.useBraces": "always",
+    "forOfStatement.singleBodyPosition": "nextLine"
   },
   "json": {
     "indentWidth": 2,

lefthook.yml

@@ -13,11 +13,15 @@ pre-commit:
 pre-push:
   parallel: true
   commands:
+    test-unit:
+      run: yarn test:unit
+    test-component:
+      run: yarn test:component
     type-check:
       run: yarn tsc --noEmit
 
     svelte-check:
-      run: yarn check:shadcn-excluded --threshold warning
+      run: yarn check --threshold warning
 
     format-check:
       glob: "*.{ts,js,svelte,json,md}"

package.json

@@ -11,7 +11,6 @@
     "prepare": "svelte-check --tsconfig ./tsconfig.json || echo ''",
     "check": "svelte-check",
     "check:watch": "svelte-check --tsconfig ./tsconfig.json --watch",
-    "check:shadcn-excluded": "svelte-check --no-tsconfig --ignore \"src/shared/shadcn\"",
     "lint": "oxlint",
     "format": "dprint fmt",
     "format:check": "dprint check",
@@ -66,6 +65,7 @@
     "vitest-browser-svelte": "^2.0.1"
   },
   "dependencies": {
+    "@chenglou/pretext": "^0.0.5",
     "@tanstack/svelte-query": "^6.0.14"
   }
 }

src/app/styles/app.css

@@ -7,7 +7,7 @@
   /* Base font size */
   --font-size: 16px;
 
-  /* GLYPHDIFF Swiss Design System */
+  /* GLYPHDIFF Design System */
   /* Primary Colors */
   --swiss-beige: #f3f0e9;
   --swiss-red: #ff3b30;
@@ -91,7 +91,6 @@
   --space-4xl: 4rem;
 
   /* Typography Scale */
-  --text-2xs: 0.625rem;
   --text-xs: 0.75rem;
   --text-sm: 0.875rem;
   --text-base: 1rem;
@@ -205,6 +204,14 @@
   --font-mono: 'Space Mono', monospace;
   --font-primary: 'Space Grotesk', system-ui, -apple-system, 'Segoe UI', Inter, Roboto, Arial, sans-serif;
   --font-secondary: 'Inter', system-ui, -apple-system, 'Segoe UI', Roboto, Arial, sans-serif;
+
+  /* Micro typography scale — extends Tailwind's text-xs (0.75rem) downward */
+  --text-5xs: 0.4375rem;
+  --text-4xs: 0.5rem;
+  --text-3xs: 0.5625rem;
+  --text-2xs: 0.625rem;
+  /* Monospace label tracking — used in Loader and Footnote */
+  --tracking-wider-mono: 0.2em;
 }
 
 @layer base {
@@ -265,6 +272,21 @@
   }
 }
 
+@layer utilities {
+  /* 21× border-black/5 dark:border-white/10 → single token */
+  .border-subtle {
+    @apply border-black/5 dark:border-white/10;
+  }
+  /* Secondary text pair */
+  .text-secondary {
+    @apply text-neutral-500 dark:text-neutral-400;
+  }
+  /* Standard focus ring */
+  .focus-ring {
+    @apply focus-visible:ring-2 focus-visible:ring-brand focus-visible:ring-offset-2;
+  }
+}
+
 /* Global utility - useful across your app */
 @media (prefers-reduced-motion: reduce) {
     * {

src/app/ui/Layout.svelte

@@ -14,12 +14,10 @@
  *
  * - Footer area (currently empty, reserved for future use)
  */
-import { BreadcrumbHeader } from '$entities/Breadcrumb';
 import { themeManager } from '$features/ChangeAppTheme';
 import GD from '$shared/assets/GD.svg';
 import { ResponsiveProvider } from '$shared/lib';
-import { Provider as TooltipProvider } from '$shared/shadcn/ui/tooltip';
-import { cn } from '$shared/shadcn/utils/shadcn-utils';
+import clsx from 'clsx';
 import {
     type Snippet,
     onDestroy,
@@ -75,29 +73,23 @@ onDestroy(() => themeManager.destroy());
         />
     </noscript>
     <title>GlyphDiff | Typography & Typefaces</title>
+    <meta
+        name="description"
+        content="Compare typefaces side by side. Adjust size, weight, leading, and tracking to find the perfect typographic pairing."
+    />
 </svelte:head>
 
 <ResponsiveProvider>
     <div
         id="app-root"
-        class={cn(
+        class={clsx(
             'min-h-screen w-auto flex flex-col bg-surface dark:bg-dark-bg',
             theme === 'dark' ? 'dark' : '',
         )}
     >
-        <header>
-            <BreadcrumbHeader />
-        </header>
-
-        <!-- <ScrollArea class="h-screen w-screen"> -->
-        <!-- <main class="flex-1 w-full mx-auto relative"> -->
-        <TooltipProvider>
-            {#if fontsReady}
-                {@render children?.()}
-            {/if}
-        </TooltipProvider>
-        <!-- </main> -->
-        <!-- </ScrollArea> -->
+        {#if fontsReady}
+            {@render children?.()}
+        {/if}
         <footer></footer>
     </div>
 </ResponsiveProvider>

src/entities/Breadcrumb/model/store/scrollBreadcrumbsStore.svelte.ts

@@ -34,11 +34,17 @@
  * A breadcrumb item representing a tracked section
  */
 export interface BreadcrumbItem {
-    /** Unique index for ordering */
+    /**
+     * Unique index for ordering
+     */
     index: number;
-    /** Display title for the breadcrumb */
+    /**
+     * Display title for the breadcrumb
+     */
     title: string;
-    /** DOM element to track */
+    /**
+     * DOM element to track
+     */
     element: HTMLElement;
 }
 
@@ -50,21 +56,37 @@ export interface BreadcrumbItem {
  * past while moving down the page.
  */
 class ScrollBreadcrumbsStore {
-    /** All tracked breadcrumb items */
+    /**
+     * All tracked breadcrumb items
+     */
     #items = $state<BreadcrumbItem[]>([]);
-    /** Set of indices that have scrolled past (exited viewport while scrolling down) */
+    /**
+     * Set of indices that have scrolled past (exited viewport while scrolling down)
+     */
     #scrolledPast = $state<Set<number>>(new Set());
-    /** Intersection Observer instance */
+    /**
+     * Intersection Observer instance
+     */
     #observer: IntersectionObserver | null = null;
-    /** Offset for smooth scrolling (sticky header height) */
+    /**
+     * Offset for smooth scrolling (sticky header height)
+     */
     #scrollOffset = 0;
-    /** Current scroll direction */
+    /**
+     * Current scroll direction
+     */
     #isScrollingDown = $state(false);
-    /** Previous scroll Y position to determine direction */
+    /**
+     * Previous scroll Y position to determine direction
+     */
     #prevScrollY = 0;
-    /** Throttled scroll handler */
+    /**
+     * Throttled scroll handler
+     */
     #handleScroll: (() => void) | null = null;
-    /** Listener count for cleanup */
+    /**
+     * Listener count for cleanup
+     */
     #listenerCount = 0;
 
     /**
@@ -83,13 +105,17 @@ class ScrollBreadcrumbsStore {
      * (fires as soon as any part of element crosses viewport edge).
      */
     #initObserver(): void {
-        if (this.#observer) return;
+        if (this.#observer) {
+            return;
+        }
 
         this.#observer = new IntersectionObserver(
             entries => {
                 for (const entry of entries) {
                     const item = this.#items.find(i => i.element === entry.target);
-                    if (!item) continue;
+                    if (!item) {
+                        continue;
+                    }
 
                     if (!entry.isIntersecting && this.#isScrollingDown) {
                         // Element exited viewport while scrolling DOWN - add to breadcrumbs
@@ -141,17 +167,23 @@ class ScrollBreadcrumbsStore {
         this.#detachScrollListener();
     }
 
-    /** All tracked items sorted by index */
+    /**
+     * All tracked items sorted by index
+     */
     get items(): BreadcrumbItem[] {
         return this.#items.slice().sort((a, b) => a.index - b.index);
     }
 
-    /** Items that have scrolled past viewport top (visible in breadcrumbs) */
+    /**
+     * Items that have scrolled past viewport top (visible in breadcrumbs)
+     */
     get scrolledPastItems(): BreadcrumbItem[] {
         return this.items.filter(item => this.#scrolledPast.has(item.index));
     }
 
-    /** Index of the most recently scrolled item (active section) */
+    /**
+     * Index of the most recently scrolled item (active section)
+     */
     get activeIndex(): number | null {
         const past = this.scrolledPastItems;
         return past.length > 0 ? past[past.length - 1].index : null;
@@ -171,7 +203,9 @@ class ScrollBreadcrumbsStore {
      * @param offset - Scroll offset in pixels (for sticky headers)
      */
     add(item: BreadcrumbItem, offset = 0): void {
-        if (this.#items.find(i => i.index === item.index)) return;
+        if (this.#items.find(i => i.index === item.index)) {
+            return;
+        }
 
         this.#scrollOffset = offset;
         this.#items.push(item);
@@ -188,7 +222,9 @@ class ScrollBreadcrumbsStore {
      */
     remove(index: number): void {
         const item = this.#items.find(i => i.index === index);
-        if (!item) return;
+        if (!item) {
+            return;
+        }
 
         this.#observer?.unobserve(item.element);
         this.#items = this.#items.filter(i => i.index !== index);
@@ -209,7 +245,9 @@ class ScrollBreadcrumbsStore {
      */
     scrollTo(index: number, container: HTMLElement | Window = window): void {
         const item = this.#items.find(i => i.index === index);
-        if (!item) return;
+        if (!item) {
+            return;
+        }
 
         const rect = item.element.getBoundingClientRect();
         const scrollTop = container === window ? window.scrollY : (container as HTMLElement).scrollTop;

src/entities/Breadcrumb/model/store/scrollBreadcrumbsStore.test.ts

@@ -1,4 +1,6 @@
-/** @vitest-environment jsdom */
+/**
+ * @vitest-environment jsdom
+ */
 import {
     afterEach,
     beforeEach,
@@ -24,7 +26,9 @@ class MockIntersectionObserver implements IntersectionObserver {
 
     constructor(callback: IntersectionObserverCallback, options?: IntersectionObserverInit) {
         this.callbacks.push(callback);
-        if (options?.rootMargin) this.rootMargin = options.rootMargin;
+        if (options?.rootMargin) {
+            this.rootMargin = options.rootMargin;
+        }
         if (options?.threshold) {
             this.thresholds = Array.isArray(options.threshold) ? options.threshold : [options.threshold];
         }
@@ -118,7 +122,9 @@ describe('ScrollBreadcrumbsStore', () => {
             (event: string, listener: EventListenerOrEventListenerObject) => {
                 if (event === 'scroll') {
                     const index = scrollListeners.indexOf(listener as () => void);
-                    if (index > -1) scrollListeners.splice(index, 1);
+                    if (index > -1) {
+                        scrollListeners.splice(index, 1);
+                    }
                 }
                 return undefined;
             },

src/entities/Breadcrumb/ui/BreadcrumbHeader/BreadcrumbHeader.stories.svelte

@@ -0,0 +1,65 @@
+<script module>
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import BreadcrumbHeader from './BreadcrumbHeader.svelte';
+
+const { Story } = defineMeta({
+    title: 'Entities/BreadcrumbHeader',
+    component: BreadcrumbHeader,
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Fixed header that slides in when the user scrolls past tracked page sections. Reads `scrollBreadcrumbsStore.scrolledPastItems` — renders nothing when the list is empty. Requires the `responsive` context provided by `Providers`.',
+            },
+            story: { inline: false },
+        },
+        layout: 'fullscreen',
+    },
+    argTypes: {},
+});
+</script>
+
+<script>
+import Providers from '$shared/lib/storybook/Providers.svelte';
+import BreadcrumbHeaderSeeded from './BreadcrumbHeaderSeeded.svelte';
+</script>
+
+<Story
+    name="With Breadcrumbs"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'Three sections are registered with the breadcrumb store. The story scrolls the iframe so the IntersectionObserver marks them as scrolled-past, revealing the fixed header.',
+            },
+        },
+    }}
+>
+    {#snippet template()}
+        <Providers>
+            <BreadcrumbHeaderSeeded />
+        </Providers>
+    {/snippet}
+</Story>
+
+<Story
+    name="Empty"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'No sections registered — BreadcrumbHeader renders nothing. This is the initial state before the user scrolls past any tracked section.',
+            },
+        },
+    }}
+>
+    {#snippet template()}
+        <Providers>
+            <div style="padding: 2rem; color: #888; font-size: 0.875rem;">
+                BreadcrumbHeader renders nothing when scrolledPastItems is empty.
+            </div>
+            <BreadcrumbHeader />
+        </Providers>
+    {/snippet}
+</Story>

src/entities/Breadcrumb/ui/BreadcrumbHeader/BreadcrumbHeader.svelte

@@ -44,7 +44,7 @@ function createButtonText(item: BreadcrumbItem) {
             flex items-center justify-between
             z-40
             bg-surface/90 dark:bg-dark-bg/90 backdrop-blur-md
-            border-b border-black/5 dark:border-white/10
+            border-b border-subtle
         "
     >
         <div class="max-w-8xl px-4 sm:px-6 h-full w-full flex items-center justify-between gap-2 sm:gap-4">

src/entities/Breadcrumb/ui/BreadcrumbHeader/BreadcrumbHeader.svelte.test.ts

@@ -0,0 +1,11 @@
+import { render } from '@testing-library/svelte';
+import BreadcrumbHeader from './BreadcrumbHeader.svelte';
+
+const context = new Map([['responsive', { isMobile: false, isMobileOrTablet: false }]]);
+
+describe('BreadcrumbHeader', () => {
+    it('renders nothing when no sections have been scrolled past', () => {
+        const { container } = render(BreadcrumbHeader, { context });
+        expect(container.firstElementChild).toBeNull();
+    });
+});

src/entities/Breadcrumb/ui/BreadcrumbHeader/BreadcrumbHeaderSeeded.svelte

@@ -0,0 +1,49 @@
+<script>
+import { onMount } from 'svelte';
+import { scrollBreadcrumbsStore } from '../../model';
+import BreadcrumbHeader from './BreadcrumbHeader.svelte';
+
+const sections = [
+    { index: 100, title: 'Introduction' },
+    { index: 101, title: 'Typography' },
+    { index: 102, title: 'Spacing' },
+];
+
+/** @type {HTMLDivElement} */
+let container;
+
+onMount(() => {
+    for (const section of sections) {
+        const el = /** @type {HTMLElement} */ (container.querySelector(`[data-story-index="${section.index}"]`));
+        scrollBreadcrumbsStore.add({ index: section.index, title: section.title, element: el }, 96);
+    }
+
+    /*
+     * Scroll past the sections so IntersectionObserver marks them as
+     * scrolled-past, making scrolledPastItems non-empty and the header visible.
+     */
+    setTimeout(() => {
+        window.scrollTo({ top: 2000, behavior: 'instant' });
+    }, 100);
+
+    return () => {
+        for (const { index } of sections) {
+            scrollBreadcrumbsStore.remove(index);
+        }
+        window.scrollTo({ top: 0, behavior: 'instant' });
+    };
+});
+</script>
+
+<div bind:this={container} style="height: 2400px; padding-top: 900px;">
+    {#each sections as section}
+        <div
+            data-story-index={section.index}
+            style="height: 400px; padding: 2rem; background: #f5f5f5; margin-bottom: 1rem;"
+        >
+            {section.title} — scroll up to see the breadcrumb header
+        </div>
+    {/each}
+</div>
+
+<BreadcrumbHeader />

src/entities/Breadcrumb/ui/NavigationWrapper/NavigationWrapper.stories.svelte

@@ -0,0 +1,109 @@
+<script module>
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import NavigationWrapper from './NavigationWrapper.svelte';
+
+const { Story } = defineMeta({
+    title: 'Entities/NavigationWrapper',
+    component: NavigationWrapper,
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Thin wrapper that registers an HTML section with `scrollBreadcrumbsStore` via a Svelte use-directive action. Has no visual output of its own — renders `{@render content(registerBreadcrumb)}` where `registerBreadcrumb` is the action to attach with `use:`. On destroy the section is automatically removed from the store.',
+            },
+            story: { inline: false },
+        },
+        layout: 'fullscreen',
+    },
+    argTypes: {
+        index: {
+            control: { type: 'number', min: 0 },
+            description: 'Unique index used for ordering in the breadcrumb trail',
+        },
+        title: {
+            control: 'text',
+            description: 'Display title shown in the breadcrumb header',
+        },
+        offset: {
+            control: { type: 'number', min: 0 },
+            description: 'Scroll offset in pixels to account for sticky headers',
+        },
+    },
+});
+</script>
+
+<script lang="ts">
+import type { ComponentProps } from 'svelte';
+</script>
+
+<Story
+    name="Single Section"
+    args={{ index: 0, title: 'Introduction', offset: 96 }}
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'A single section registered with NavigationWrapper. The `content` snippet receives the `register` action and applies it via `use:register`.',
+            },
+        },
+    }}
+>
+    {#snippet template(args: ComponentProps<typeof NavigationWrapper>)}
+        <NavigationWrapper {...args}>
+            {#snippet content(register)}
+                <section use:register style="padding: 2rem; background: #f5f5f5; min-height: 200px;">
+                    <p style="font-size: 0.875rem; color: #555;">
+                        Section registered as <strong>{args.title}</strong> at index {args.index}. Scroll past this
+                        section to see it appear in the breadcrumb header.
+                    </p>
+                </section>
+            {/snippet}
+        </NavigationWrapper>
+    {/snippet}
+</Story>
+
+<Story
+    name="Multiple Sections"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'Three sequential sections each wrapped in NavigationWrapper with distinct indices and titles. Demonstrates how the breadcrumb trail builds as the user scrolls.',
+            },
+        },
+    }}
+>
+    {#snippet template()}
+        <div style="display: flex; flex-direction: column; gap: 0;">
+            <NavigationWrapper index={0} title="Introduction" offset={96}>
+                {#snippet content(register)}
+                    <section use:register style="padding: 2rem; background: #f5f5f5; min-height: 300px;">
+                        <h2 style="margin: 0 0 0.5rem;">Introduction</h2>
+                        <p style="font-size: 0.875rem; color: #555;">
+                            Registered as section 0. Scroll down to build the breadcrumb trail.
+                        </p>
+                    </section>
+                {/snippet}
+            </NavigationWrapper>
+
+            <NavigationWrapper index={1} title="Typography" offset={96}>
+                {#snippet content(register)}
+                    <section use:register style="padding: 2rem; background: #ebebeb; min-height: 300px;">
+                        <h2 style="margin: 0 0 0.5rem;">Typography</h2>
+                        <p style="font-size: 0.875rem; color: #555;">Registered as section 1.</p>
+                    </section>
+                {/snippet}
+            </NavigationWrapper>
+
+            <NavigationWrapper index={2} title="Spacing" offset={96}>
+                {#snippet content(register)}
+                    <section use:register style="padding: 2rem; background: #e0e0e0; min-height: 300px;">
+                        <h2 style="margin: 0 0 0.5rem;">Spacing</h2>
+                        <p style="font-size: 0.875rem; color: #555;">Registered as section 2.</p>
+                    </section>
+                {/snippet}
+            </NavigationWrapper>
+        </div>
+    {/snippet}
+</Story>

src/entities/Font/api/proxy/proxyFonts.test.ts

@@ -19,10 +19,13 @@ vi.mock('$shared/api/api', () => ({
 }));
 
 import { api } from '$shared/api/api';
+import { queryClient } from '$shared/api/queryClient';
+import { fontKeys } from '$shared/api/queryKeys';
 import {
     fetchFontsByIds,
     fetchProxyFontById,
     fetchProxyFonts,
+    seedFontCache,
 } from './proxyFonts';
 
 const PROXY_API_URL = 'https://api.glyphdiff.com/api/v1/fonts';
@@ -46,6 +49,7 @@ function mockApiGet<T>(data: T) {
 describe('proxyFonts', () => {
     beforeEach(() => {
         vi.mocked(api.get).mockReset();
+        queryClient.clear();
     });
 
     describe('fetchProxyFonts', () => {
@@ -168,4 +172,33 @@ describe('proxyFonts', () => {
             expect(result).toEqual([]);
         });
     });
+
+    describe('seedFontCache', () => {
+        test('should populate cache with multiple fonts', () => {
+            const fonts = [
+                createMockFont({ id: '1', name: 'A' }),
+                createMockFont({ id: '2', name: 'B' }),
+            ];
+            seedFontCache(fonts);
+            expect(queryClient.getQueryData(fontKeys.detail('1'))).toEqual(fonts[0]);
+            expect(queryClient.getQueryData(fontKeys.detail('2'))).toEqual(fonts[1]);
+        });
+
+        test('should update existing cached fonts with new data', () => {
+            const id = 'update-me';
+            queryClient.setQueryData(fontKeys.detail(id), createMockFont({ id, name: 'Old' }));
+
+            const updated = createMockFont({ id, name: 'New' });
+            seedFontCache([updated]);
+
+            expect(queryClient.getQueryData(fontKeys.detail(id))).toEqual(updated);
+        });
+
+        test('should handle empty input arrays gracefully', () => {
+            const spy = vi.spyOn(queryClient, 'setQueryData');
+            seedFontCache([]);
+            expect(spy).not.toHaveBeenCalled();
+            spy.mockRestore();
+        });
+    });
 });

src/entities/Font/api/proxy/proxyFonts.ts

@@ -11,13 +11,23 @@
  */
 
 import { api } from '$shared/api/api';
+import { queryClient } from '$shared/api/queryClient';
+import { fontKeys } from '$shared/api/queryKeys';
 import { buildQueryString } from '$shared/lib/utils';
 import type { QueryParams } from '$shared/lib/utils';
 import type { UnifiedFont } from '../../model/types';
-import type {
-    FontCategory,
-    FontSubset,
-} from '../../model/types';
+
+/**
+ * Normalizes cache by seeding individual font entries from collection responses.
+ * This ensures that a font fetched in a list or batch is available via its detail key.
+ *
+ * @param fonts - Array of fonts to cache
+ */
+export function seedFontCache(fonts: UnifiedFont[]): void {
+    fonts.forEach(font => {
+        queryClient.setQueryData(fontKeys.detail(font.id), font);
+    });
+}
 
 /**
  * Proxy API base URL
@@ -87,16 +97,24 @@ export interface ProxyFontsParams extends QueryParams {
  * Includes pagination metadata alongside font data
  */
 export interface ProxyFontsResponse {
-    /** Array of unified font objects */
+    /**
+     * List of font objects returned by the proxy
+     */
     fonts: UnifiedFont[];
 
-    /** Total number of fonts matching the query */
+    /**
+     * Total number of matching fonts (ignoring limit/offset)
+     */
     total: number;
 
-    /** Limit used for this request */
+    /**
+     * Page size used for the request
+     */
     limit: number;
 
-    /** Offset used for this request */
+    /**
+     * Start index for the result set
+     */
     offset: number;
 }
 
@@ -179,7 +197,9 @@ export async function fetchProxyFontById(
  * @returns Promise resolving to an array of fonts
  */
 export async function fetchFontsByIds(ids: string[]): Promise<UnifiedFont[]> {
-    if (ids.length === 0) return [];
+    if (ids.length === 0) {
+        return [];
+    }
 
     const queryString = ids.join(',');
     const url = `${PROXY_API_URL}/batch?ids=${queryString}`;

src/entities/Font/index.ts

@@ -1,3 +1,4 @@
 export * from './api';
+export * from './lib';
 export * from './model';
 export * from './ui';

src/entities/Font/lib/getFontUrl/getFontUrl.ts

@@ -3,7 +3,9 @@ import type {
     UnifiedFont,
 } from '../../model';
 
-/** Valid font weight values (100-900 in increments of 100) */
+/**
+ * Valid font weight values (100-900 in increments of 100)
+ */
 const SIZES = [100, 200, 300, 400, 500, 600, 700, 800, 900];
 
 /**

src/entities/Font/lib/index.ts

@@ -48,3 +48,6 @@ export {
     FontNetworkError,
     FontResponseError,
 } from './errors/errors';
+
+export { createFontRowSizeResolver } from './sizeResolver/createFontRowSizeResolver';
+export type { FontRowSizeResolverOptions } from './sizeResolver/createFontRowSizeResolver';

src/entities/Font/lib/mocks/filters.mock.ts

@@ -1,31 +1,3 @@
-/**
- * Mock font filter data
- *
- * Factory functions and preset mock data for font-related filters.
- * Used in Storybook stories for font filtering components.
- *
- * ## Usage
- *
- * ```ts
- * import {
- *     createMockFilter,
- *     MOCK_FILTERS,
- * } from '$entities/Font/lib/mocks';
- *
- * // Create a custom filter
- * const customFilter = createMockFilter({
- *     properties: [
- *         { id: 'option1', name: 'Option 1', value: 'option1' },
- *         { id: 'option2', name: 'Option 2', value: 'option2', selected: true },
- *     ],
- * });
- *
- * // Use preset filters
- * const categoriesFilter = MOCK_FILTERS.categories;
- * const subsetsFilter = MOCK_FILTERS.subsets;
- * ```
- */
-
 import type {
     FontCategory,
     FontProvider,
@@ -34,13 +6,13 @@ import type {
 import type { Property } from '$shared/lib';
 import { createFilter } from '$shared/lib';
 
-// TYPE DEFINITIONS
-
 /**
  * Options for creating a mock filter
  */
 export interface MockFilterOptions {
-    /** Filter properties */
+    /**
+     * Initial set of properties for the mock filter
+     */
     properties: Property<string>[];
 }
 
@@ -48,16 +20,20 @@ export interface MockFilterOptions {
  * Preset mock filters for font filtering
  */
 export interface MockFilters {
-    /** Provider filter (Google, Fontshare) */
+    /**
+     * Provider filter (Google, Fontshare)
+     */
     providers: ReturnType<typeof createFilter<'google' | 'fontshare'>>;
-    /** Category filter (sans-serif, serif, display, etc.) */
+    /**
+     * Category filter (sans-serif, serif, display, etc.)
+     */
     categories: ReturnType<typeof createFilter<FontCategory>>;
-    /** Subset filter (latin, latin-ext, cyrillic, etc.) */
+    /**
+     * Subset filter (latin, latin-ext, cyrillic, etc.)
+     */
     subsets: ReturnType<typeof createFilter<FontSubset>>;
 }
 
-// FONT CATEGORIES
-
 /**
  * Unified categories (combines both providers)
  */
@@ -71,8 +47,6 @@ export const UNIFIED_CATEGORIES: Property<FontCategory>[] = [
     { id: 'script', name: 'Script', value: 'script' },
 ];
 
-// FONT SUBSETS
-
 /**
  * Common font subsets
  */
@@ -85,8 +59,6 @@ export const FONT_SUBSETS: Property<FontSubset>[] = [
     { id: 'devanagari', name: 'Devanagari', value: 'devanagari' },
 ];
 
-// FONT PROVIDERS
-
 /**
  * Font providers
  */
@@ -95,8 +67,6 @@ export const FONT_PROVIDERS: Property<FontProvider>[] = [
     { id: 'fontshare', name: 'Fontshare', value: 'fontshare' },
 ];
 
-// FILTER FACTORIES
-
 /**
  * Create a mock filter from properties
  */
@@ -139,8 +109,6 @@ export function createProvidersFilter(options?: { selected?: FontProvider[] }) {
     return createFilter<FontProvider>({ properties });
 }
 
-// PRESET FILTERS
-
 /**
  * Preset mock filters - use these directly in stories
  */
@@ -216,8 +184,6 @@ export const MOCK_FILTERS_ALL_SELECTED: MockFilters = {
     }),
 };
 
-// GENERIC FILTER MOCKS
-
 /**
  * Create a mock filter with generic string properties
  * Useful for testing generic filter components
@@ -239,7 +205,9 @@ export function createGenericFilter(
  * Preset generic filters for testing
  */
 export const GENERIC_FILTERS = {
-    /** Small filter with 3 items */
+    /**
+     * Small filter with 3 items
+     */
     small: createFilter({
         properties: [
             { id: 'option-1', name: 'Option 1', value: 'option-1' },
@@ -247,7 +215,9 @@ export const GENERIC_FILTERS = {
             { id: 'option-3', name: 'Option 3', value: 'option-3' },
         ],
     }),
-    /** Medium filter with 6 items */
+    /**
+     * Medium filter with 6 items
+     */
     medium: createFilter({
         properties: [
             { id: 'alpha', name: 'Alpha', value: 'alpha' },
@@ -258,7 +228,9 @@ export const GENERIC_FILTERS = {
             { id: 'zeta', name: 'Zeta', value: 'zeta' },
         ],
     }),
-    /** Large filter with 12 items */
+    /**
+     * Large filter with 12 items
+     */
     large: createFilter({
         properties: [
             { id: 'jan', name: 'January', value: 'jan' },
@@ -275,7 +247,9 @@ export const GENERIC_FILTERS = {
             { id: 'dec', name: 'December', value: 'dec' },
         ],
     }),
-    /** Filter with some pre-selected items */
+    /**
+     * Filter with some pre-selected items
+     */
     partial: createFilter({
         properties: [
             { id: 'red', name: 'Red', value: 'red', selected: true },
@@ -284,7 +258,9 @@ export const GENERIC_FILTERS = {
             { id: 'yellow', name: 'Yellow', value: 'yellow', selected: false },
         ],
     }),
-    /** Filter with all items selected */
+    /**
+     * Filter with all items selected
+     */
     allSelected: createFilter({
         properties: [
             { id: 'cat', name: 'Cat', value: 'cat', selected: true },
@@ -292,7 +268,9 @@ export const GENERIC_FILTERS = {
             { id: 'bird', name: 'Bird', value: 'bird', selected: true },
         ],
     }),
-    /** Empty filter (no items) */
+    /**
+     * Empty filter (no items)
+     */
     empty: createFilter({
         properties: [],
     }),

src/entities/Font/lib/mocks/fonts.mock.ts

@@ -51,23 +51,41 @@ import type {
  * Options for creating a mock UnifiedFont
  */
 export interface MockUnifiedFontOptions {
-    /** Unique identifier (default: derived from name) */
+    /**
+     * Unique identifier (default: derived from name)
+     */
     id?: string;
-    /** Font display name (default: 'Mock Font') */
+    /**
+     * Font display name (default: 'Mock Font')
+     */
     name?: string;
-    /** Font provider (default: 'google') */
+    /**
+     * Font provider (default: 'google')
+     */
     provider?: FontProvider;
-    /** Font category (default: 'sans-serif') */
+    /**
+     * Font category (default: 'sans-serif')
+     */
     category?: FontCategory;
-    /** Font subsets (default: ['latin']) */
+    /**
+     * Font subsets (default: ['latin'])
+     */
     subsets?: FontSubset[];
-    /** Font variants (default: ['regular', '700', 'italic', '700italic']) */
+    /**
+     * Font variants (default: ['regular', '700', 'italic', '700italic'])
+     */
     variants?: FontVariant[];
-    /** Style URLs (if not provided, mock URLs are generated) */
+    /**
+     * Style URLs (if not provided, mock URLs are generated)
+     */
     styles?: FontStyleUrls;
-    /** Metadata overrides */
+    /**
+     * Metadata overrides
+     */
     metadata?: Partial<FontMetadata>;
-    /** Features overrides */
+    /**
+     * Features overrides
+     */
     features?: Partial<FontFeatures>;
 }
 

src/entities/Font/lib/mocks/stores.mock.ts

@@ -1,8 +1,4 @@
 /**
- * ============================================================================
- * MOCK FONT STORE HELPERS
- * ============================================================================
- *
  * Factory functions and preset mock data for TanStack Query stores and state management.
  * Used in Storybook stories for components that use reactive stores.
  *
@@ -35,27 +31,73 @@ import {
     generateMockFonts,
 } from './fonts.mock';
 
-// TANSTACK QUERY MOCK TYPES
-
 /**
  * Mock TanStack Query state
  */
 export interface MockQueryState<TData = unknown, TError = Error> {
+    /**
+     * Primary query status (pending, success, error)
+     */
     status: QueryStatus;
+    /**
+     * Payload data (present on success)
+     */
     data?: TData;
+    /**
+     * Caught error object (present on error)
+     */
     error?: TError;
+    /**
+     * True if initial load is in progress
+     */
     isLoading?: boolean;
+    /**
+     * True if background fetch is in progress
+     */
     isFetching?: boolean;
+    /**
+     * True if query resolved successfully
+     */
     isSuccess?: boolean;
+    /**
+     * True if query failed
+     */
     isError?: boolean;
+    /**
+     * True if query is waiting to be executed
+     */
     isPending?: boolean;
+    /**
+     * Timestamp of last successful data retrieval
+     */
     dataUpdatedAt?: number;
+    /**
+     * Timestamp of last recorded error
+     */
     errorUpdatedAt?: number;
+    /**
+     * Total number of consecutive failures
+     */
     failureCount?: number;
+    /**
+     * Detailed reason for the last failure
+     */
     failureReason?: TError;
+    /**
+     * Number of times an error has been caught
+     */
     errorUpdateCount?: number;
+    /**
+     * True if currently refetching in background
+     */
     isRefetching?: boolean;
+    /**
+     * True if refetch attempt failed
+     */
     isRefetchError?: boolean;
+    /**
+     * True if query is paused (e.g. offline)
+     */
     isPaused?: boolean;
 }
 
@@ -63,26 +105,72 @@ export interface MockQueryState<TData = unknown, TError = Error> {
  * Mock TanStack Query observer result
  */
 export interface MockQueryObserverResult<TData = unknown, TError = Error> {
+    /**
+     * Current observer status
+     */
     status?: QueryStatus;
+    /**
+     * Cached or active data payload
+     */
     data?: TData;
+    /**
+     * Caught error from the observer
+     */
     error?: TError;
+    /**
+     * Loading flag for the observer
+     */
     isLoading?: boolean;
+    /**
+     * Fetching flag for the observer
+     */
     isFetching?: boolean;
+    /**
+     * Success flag for the observer
+     */
     isSuccess?: boolean;
+    /**
+     * Error flag for the observer
+     */
     isError?: boolean;
+    /**
+     * Pending flag for the observer
+     */
     isPending?: boolean;
+    /**
+     * Last update time for data
+     */
     dataUpdatedAt?: number;
+    /**
+     * Last update time for error
+     */
     errorUpdatedAt?: number;
+    /**
+     * Consecutive failure count
+     */
     failureCount?: number;
+    /**
+     * Failure reason object
+     */
     failureReason?: TError;
+    /**
+     * Error count for the observer
+     */
     errorUpdateCount?: number;
+    /**
+     * Refetching flag
+     */
     isRefetching?: boolean;
+    /**
+     * Refetch error flag
+     */
     isRefetchError?: boolean;
+    /**
+     * Paused flag
+     */
     isPaused?: boolean;
 }
 
-// TANSTACK QUERY MOCK FACTORIES
-
 /**
  * Create a mock query state for TanStack Query
  */
@@ -138,33 +226,53 @@ export function createSuccessState<TData>(data: TData): MockQueryObserverResult<
     return createMockQueryState<TData>({ status: 'success', data, error: undefined });
 }
 
-// FONT STORE MOCKS
-
 /**
  * Mock UnifiedFontStore state
  */
 export interface MockFontStoreState {
-    /** All cached fonts */
+    /**
+     * Map of mock fonts indexed by ID
+     */
     fonts: Record<string, UnifiedFont>;
-    /** Current page */
+    /**
+     * Currently active page number
+     */
     page: number;
-    /** Total pages available */
+    /**
+     * Total number of pages calculated from limit
+     */
     totalPages: number;
-    /** Items per page */
+    /**
+     * Number of items per page
+     */
     limit: number;
-    /** Total font count */
+    /**
+     * Total number of available fonts
+     */
     total: number;
-    /** Loading state */
+    /**
+     * Store-level loading status
+     */
     isLoading: boolean;
-    /** Error state */
+    /**
+     * Caught error object
+     */
     error: Error | null;
-    /** Search query */
+    /**
+     * Mock search filter string
+     */
     searchQuery: string;
-    /** Selected provider */
+    /**
+     * Mock provider filter selection
+     */
     provider: 'google' | 'fontshare' | 'all';
-    /** Selected category */
+    /**
+     * Mock category filter selection
+     */
     category: string | null;
-    /** Selected subset */
+    /**
+     * Mock subset filter selection
+     */
     subset: string | null;
 }
 
@@ -210,10 +318,12 @@ export function createMockFontStoreState(
 }
 
 /**
- * Preset font store states
+ * Preset font store states for UI testing
  */
 export const MOCK_FONT_STORE_STATES = {
-    /** Initial loading state */
+    /**
+     * Initial loading state with no data
+     */
     loading: createMockFontStoreState({
         isLoading: true,
         fonts: {},
@@ -221,7 +331,9 @@ export const MOCK_FONT_STORE_STATES = {
         page: 1,
     }),
 
-    /** Empty state (no fonts found) */
+    /**
+     * State with no fonts matching filters
+     */
     empty: createMockFontStoreState({
         fonts: {},
         total: 0,
@@ -229,7 +341,9 @@ export const MOCK_FONT_STORE_STATES = {
         isLoading: false,
     }),
 
-    /** First page with fonts */
+    /**
+     * First page of results (10 items)
+     */
     firstPage: createMockFontStoreState({
         fonts: Object.fromEntries(
             Object.values(UNIFIED_FONTS).slice(0, 10).map(font => [font.id, font]),
@@ -241,7 +355,9 @@ export const MOCK_FONT_STORE_STATES = {
         isLoading: false,
     }),
 
-    /** Second page with fonts */
+    /**
+     * Second page of results (10 items)
+     */
     secondPage: createMockFontStoreState({
         fonts: Object.fromEntries(
             Object.values(UNIFIED_FONTS).slice(10, 20).map(font => [font.id, font]),
@@ -253,7 +369,9 @@ export const MOCK_FONT_STORE_STATES = {
         isLoading: false,
     }),
 
-    /** Last page with fonts */
+    /**
+     * Final page of results (5 items)
+     */
     lastPage: createMockFontStoreState({
         fonts: Object.fromEntries(
             Object.values(UNIFIED_FONTS).slice(0, 5).map(font => [font.id, font]),
@@ -265,7 +383,9 @@ export const MOCK_FONT_STORE_STATES = {
         isLoading: false,
     }),
 
-    /** Error state */
+    /**
+     * Terminal failure state
+     */
     error: createMockFontStoreState({
         fonts: {},
         error: new Error('Failed to load fonts'),
@@ -274,7 +394,9 @@ export const MOCK_FONT_STORE_STATES = {
         isLoading: false,
     }),
 
-    /** With search query */
+    /**
+     * State with active search query
+     */
     withSearch: createMockFontStoreState({
         fonts: Object.fromEntries(
             Object.values(UNIFIED_FONTS).slice(0, 3).map(font => [font.id, font]),
@@ -285,7 +407,9 @@ export const MOCK_FONT_STORE_STATES = {
         searchQuery: 'Roboto',
     }),
 
-    /** Filtered by category */
+    /**
+     * State with active category filter
+     */
     filteredByCategory: createMockFontStoreState({
         fonts: Object.fromEntries(
             Object.values(UNIFIED_FONTS)
@@ -299,7 +423,9 @@ export const MOCK_FONT_STORE_STATES = {
         category: 'serif',
     }),
 
-    /** Filtered by provider */
+    /**
+     * State with active provider filter
+     */
     filteredByProvider: createMockFontStoreState({
         fonts: Object.fromEntries(
             Object.values(UNIFIED_FONTS)
@@ -313,7 +439,9 @@ export const MOCK_FONT_STORE_STATES = {
         provider: 'google',
     }),
 
-    /** Large dataset */
+    /**
+     * Large collection for performance testing (50 items)
+     */
     largeDataset: createMockFontStoreState({
         fonts: Object.fromEntries(
             generateMockFonts(50).map(font => [font.id, font]),
@@ -326,17 +454,30 @@ export const MOCK_FONT_STORE_STATES = {
     }),
 };
 
-// MOCK STORE OBJECT
-
 /**
  * Create a mock store object that mimics TanStack Query behavior
  * Useful for components that subscribe to store properties
  */
 export function createMockStore<T>(config: {
+    /**
+     * Reactive data payload
+     */
     data?: T;
+    /**
+     * Loading status flag
+     */
     isLoading?: boolean;
+    /**
+     * Error status flag
+     */
     isError?: boolean;
+    /**
+     * Catch-all error object
+     */
     error?: Error;
+    /**
+     * Background fetching flag
+     */
     isFetching?: boolean;
 }) {
     const {
@@ -348,50 +489,81 @@ export function createMockStore<T>(config: {
     } = config;
 
     return {
+        /**
+         * Returns the active data payload
+         */
         get data() {
             return data;
         },
+        /**
+         * True if initially loading
+         */
         get isLoading() {
             return isLoading;
         },
+        /**
+         * True if last request failed
+         */
         get isError() {
             return isError;
         },
+        /**
+         * Returns the caught error object
+         */
         get error() {
             return error;
         },
+        /**
+         * True if fetching in background
+         */
         get isFetching() {
             return isFetching;
         },
+        /**
+         * True if query is stable and has data
+         */
         get isSuccess() {
             return !isLoading && !isError && data !== undefined;
         },
+        /**
+         * Returns semantic status string
+         */
         get status() {
-            if (isLoading) return 'pending';
-            if (isError) return 'error';
+            if (isLoading) {
+                return 'pending';
+            }
+            if (isError) {
+                return 'error';
+            }
             return 'success';
         },
     };
 }
 
 /**
- * Preset mock stores
+ * Preset mock stores for common UI states
  */
 export const MOCK_STORES = {
-    /** Font store in loading state */
+    /**
+     * Initial loading state
+     */
     loadingFontStore: createMockStore<UnifiedFont[]>({
         isLoading: true,
         data: undefined,
     }),
 
-    /** Font store with fonts loaded */
+    /**
+     * Successful data load state
+     */
     successFontStore: createMockStore<UnifiedFont[]>({
         data: Object.values(UNIFIED_FONTS),
         isLoading: false,
         isError: false,
     }),
 
-    /** Font store with error */
+    /**
+     * API error state
+     */
     errorFontStore: createMockStore<UnifiedFont[]>({
         data: undefined,
         isLoading: false,
@@ -399,7 +571,9 @@ export const MOCK_STORES = {
         error: new Error('Failed to load fonts'),
     }),
 
-    /** Font store with empty results */
+    /**
+     * Empty result set state
+     */
     emptyFontStore: createMockStore<UnifiedFont[]>({
         data: [],
         isLoading: false,
@@ -414,36 +588,69 @@ export const MOCK_STORES = {
         const mockState = createMockFontStoreState(state);
         return {
             // State properties
+            /**
+             * Collection of mock fonts
+             */
             get fonts() {
                 return mockState.fonts;
             },
+            /**
+             * Current mock page
+             */
             get page() {
                 return mockState.page;
             },
+            /**
+             * Total mock pages
+             */
             get totalPages() {
                 return mockState.totalPages;
             },
+            /**
+             * Mock items per page
+             */
             get limit() {
                 return mockState.limit;
             },
+            /**
+             * Total mock items
+             */
             get total() {
                 return mockState.total;
             },
+            /**
+             * Mock loading status
+             */
             get isLoading() {
                 return mockState.isLoading;
             },
+            /**
+             * Mock error status
+             */
             get error() {
                 return mockState.error;
             },
+            /**
+             * Mock search string
+             */
             get searchQuery() {
                 return mockState.searchQuery;
             },
+            /**
+             * Mock provider filter
+             */
             get provider() {
                 return mockState.provider;
             },
+            /**
+             * Mock category filter
+             */
             get category() {
                 return mockState.category;
             },
+            /**
+             * Mock subset filter
+             */
             get subset() {
                 return mockState.subset;
             },
@@ -464,15 +671,45 @@ export const MOCK_STORES = {
      * Matches FontStore's public API for Storybook use
      */
     fontStore: (config: {
+        /**
+         * Preset font list
+         */
         fonts?: UnifiedFont[];
+        /**
+         * Total item count
+         */
         total?: number;
+        /**
+         * Items per page
+         */
         limit?: number;
+        /**
+         * Pagination offset
+         */
         offset?: number;
+        /**
+         * Loading flag
+         */
         isLoading?: boolean;
+        /**
+         * Fetching flag
+         */
         isFetching?: boolean;
+        /**
+         * Error flag
+         */
         isError?: boolean;
+        /**
+         * Catch-all error object
+         */
         error?: Error | null;
+        /**
+         * Has more pages flag
+         */
         hasMore?: boolean;
+        /**
+         * Current page number
+         */
         page?: number;
     } = {}) => {
         const {
@@ -495,27 +732,51 @@ export const MOCK_STORES = {
 
         return {
             // State getters
+            /**
+             * Current mock parameters
+             */
             get params() {
                 return state.params;
             },
+            /**
+             * Mock font list
+             */
             get fonts() {
                 return mockFonts;
             },
+            /**
+             * Mock loading state
+             */
             get isLoading() {
                 return isLoading;
             },
+            /**
+             * Mock fetching state
+             */
             get isFetching() {
                 return isFetching;
             },
+            /**
+             * Mock error state
+             */
             get isError() {
                 return isError;
             },
+            /**
+             * Mock error object
+             */
             get error() {
                 return error;
             },
+            /**
+             * Mock empty state check
+             */
             get isEmpty() {
                 return !isLoading && !isFetching && mockFonts.length === 0;
             },
+            /**
+             * Mock pagination metadata
+             */
             get pagination() {
                 return {
                     total: mockTotal,
@@ -527,18 +788,33 @@ export const MOCK_STORES = {
                 };
             },
             // Category getters
+            /**
+             * Derived sans-serif filter
+             */
             get sansSerifFonts() {
                 return mockFonts.filter(f => f.category === 'sans-serif');
             },
+            /**
+             * Derived serif filter
+             */
             get serifFonts() {
                 return mockFonts.filter(f => f.category === 'serif');
             },
+            /**
+             * Derived display filter
+             */
             get displayFonts() {
                 return mockFonts.filter(f => f.category === 'display');
             },
+            /**
+             * Derived handwriting filter
+             */
             get handwritingFonts() {
                 return mockFonts.filter(f => f.category === 'handwriting');
             },
+            /**
+             * Derived monospace filter
+             */
             get monospaceFonts() {
                 return mockFonts.filter(f => f.category === 'monospace');
             },

src/entities/Font/lib/sizeResolver/createFontRowSizeResolver.test.ts

@@ -0,0 +1,168 @@
+// @vitest-environment jsdom
+import { TextLayoutEngine } from '$shared/lib';
+import { installCanvasMock } from '$shared/lib/helpers/__mocks__/canvas';
+import { clearCache } from '@chenglou/pretext';
+import {
+    beforeEach,
+    describe,
+    expect,
+    it,
+    vi,
+} from 'vitest';
+import type { FontLoadStatus } from '../../model/types';
+import { mockUnifiedFont } from '../mocks';
+import { createFontRowSizeResolver } from './createFontRowSizeResolver';
+
+// Fixed-width canvas mock: every character is 10px wide regardless of font.
+// This makes wrapping math predictable: N chars × 10px = N×10 total width.
+const CHAR_WIDTH = 10;
+const LINE_HEIGHT = 20;
+const CONTAINER_WIDTH = 200;
+const CONTENT_PADDING_X = 32; // p-4 × 2 sides = 32px
+const CHROME_HEIGHT = 56;
+const FALLBACK_HEIGHT = 220;
+const FONT_SIZE_PX = 16;
+
+describe('createFontRowSizeResolver', () => {
+    let statusMap: Map<string, FontLoadStatus>;
+    let getStatus: (key: string) => FontLoadStatus | undefined;
+
+    beforeEach(() => {
+        installCanvasMock((_font, text) => text.length * CHAR_WIDTH);
+        clearCache();
+        statusMap = new Map();
+        getStatus = key => statusMap.get(key);
+    });
+
+    function makeResolver(overrides?: Partial<Parameters<typeof createFontRowSizeResolver>[0]>) {
+        const font = mockUnifiedFont({ id: 'inter', name: 'Inter' });
+        return {
+            font,
+            resolver: createFontRowSizeResolver({
+                getFonts: () => [font],
+                getWeight: () => 400,
+                getPreviewText: () => 'Hello',
+                getContainerWidth: () => CONTAINER_WIDTH,
+                getFontSizePx: () => FONT_SIZE_PX,
+                getLineHeightPx: () => LINE_HEIGHT,
+                getStatus,
+                contentHorizontalPadding: CONTENT_PADDING_X,
+                chromeHeight: CHROME_HEIGHT,
+                fallbackHeight: FALLBACK_HEIGHT,
+                ...overrides,
+            }),
+        };
+    }
+
+    it('returns fallbackHeight when font status is undefined', () => {
+        const { resolver } = makeResolver();
+        expect(resolver(0)).toBe(FALLBACK_HEIGHT);
+    });
+
+    it('returns fallbackHeight when font status is "loading"', () => {
+        const { resolver } = makeResolver();
+        statusMap.set('inter@400', 'loading');
+        expect(resolver(0)).toBe(FALLBACK_HEIGHT);
+    });
+
+    it('returns fallbackHeight when font status is "error"', () => {
+        const { resolver } = makeResolver();
+        statusMap.set('inter@400', 'error');
+        expect(resolver(0)).toBe(FALLBACK_HEIGHT);
+    });
+
+    it('returns fallbackHeight when containerWidth is 0', () => {
+        const { resolver } = makeResolver({ getContainerWidth: () => 0 });
+        statusMap.set('inter@400', 'loaded');
+        expect(resolver(0)).toBe(FALLBACK_HEIGHT);
+    });
+
+    it('returns fallbackHeight when previewText is empty', () => {
+        const { resolver } = makeResolver({ getPreviewText: () => '' });
+        statusMap.set('inter@400', 'loaded');
+        expect(resolver(0)).toBe(FALLBACK_HEIGHT);
+    });
+
+    it('returns fallbackHeight for out-of-bounds rowIndex', () => {
+        const { resolver } = makeResolver();
+        statusMap.set('inter@400', 'loaded');
+        expect(resolver(99)).toBe(FALLBACK_HEIGHT);
+    });
+
+    it('returns computed height (totalHeight + chromeHeight) when font is loaded', () => {
+        const { resolver } = makeResolver();
+        statusMap.set('inter@400', 'loaded');
+
+        // 'Hello' = 5 chars × 10px = 50px. contentWidth = 200 - 32 = 168px. Fits on one line.
+        // totalHeight = 1 × LINE_HEIGHT = 20. result = 20 + CHROME_HEIGHT = 76.
+        const result = resolver(0);
+        expect(result).toBe(LINE_HEIGHT + CHROME_HEIGHT);
+    });
+
+    it('returns increased height when text wraps due to narrow container', () => {
+        // contentWidth = 40 - 32 = 8px — 'Hello' (50px) forces wrapping onto many lines
+        const { resolver } = makeResolver({ getContainerWidth: () => 40 });
+        statusMap.set('inter@400', 'loaded');
+
+        const result = resolver(0);
+        expect(result).toBeGreaterThan(LINE_HEIGHT + CHROME_HEIGHT);
+    });
+
+    it('does not call layout() again on second call with same arguments', () => {
+        const { resolver } = makeResolver();
+        statusMap.set('inter@400', 'loaded');
+
+        const layoutSpy = vi.spyOn(TextLayoutEngine.prototype, 'layout');
+
+        resolver(0);
+        resolver(0);
+
+        expect(layoutSpy).toHaveBeenCalledTimes(1);
+        layoutSpy.mockRestore();
+    });
+
+    it('calls layout() again when containerWidth changes (cache miss)', () => {
+        let width = CONTAINER_WIDTH;
+        const { resolver } = makeResolver({ getContainerWidth: () => width });
+        statusMap.set('inter@400', 'loaded');
+
+        const layoutSpy = vi.spyOn(TextLayoutEngine.prototype, 'layout');
+
+        resolver(0);
+        width = 100;
+        resolver(0);
+
+        expect(layoutSpy).toHaveBeenCalledTimes(2);
+        layoutSpy.mockRestore();
+    });
+
+    it('returns greater height when container narrows (more wrapping)', () => {
+        let width = CONTAINER_WIDTH;
+        const { resolver } = makeResolver({ getContainerWidth: () => width });
+        statusMap.set('inter@400', 'loaded');
+
+        const h1 = resolver(0);
+        width = 100; // narrower → more wrapping
+        const h2 = resolver(0);
+
+        expect(h2).toBeGreaterThanOrEqual(h1);
+    });
+
+    it('uses variable font key for variable fonts', () => {
+        const vfFont = mockUnifiedFont({ id: 'roboto', name: 'Roboto', features: { isVariable: true } });
+        const { resolver } = makeResolver({ getFonts: () => [vfFont] });
+        // Variable fonts use '{id}@vf' key, not '{id}@{weight}'
+        statusMap.set('roboto@vf', 'loaded');
+        const result = resolver(0);
+        expect(result).not.toBe(FALLBACK_HEIGHT);
+        expect(result).toBeGreaterThan(0);
+    });
+
+    it('returns fallbackHeight for variable font when static key is set instead', () => {
+        const vfFont = mockUnifiedFont({ id: 'roboto', name: 'Roboto', features: { isVariable: true } });
+        const { resolver } = makeResolver({ getFonts: () => [vfFont] });
+        // Setting the static key should NOT unlock computed height for variable fonts
+        statusMap.set('roboto@400', 'loaded');
+        expect(resolver(0)).toBe(FALLBACK_HEIGHT);
+    });
+});

src/entities/Font/lib/sizeResolver/createFontRowSizeResolver.ts

@@ -0,0 +1,134 @@
+import { TextLayoutEngine } from '$shared/lib';
+import { generateFontKey } from '../../model/store/appliedFontsStore/utils/generateFontKey/generateFontKey';
+import type {
+    FontLoadStatus,
+    UnifiedFont,
+} from '../../model/types';
+
+/**
+ * Options for {@link createFontRowSizeResolver}.
+ *
+ * All getter functions are called on every resolver invocation. When called
+ * inside a Svelte `$derived.by` block, any reactive state read within them
+ * (e.g. `SvelteMap.get()`) is automatically tracked as a dependency.
+ */
+export interface FontRowSizeResolverOptions {
+    /**
+     * Returns the current fonts array. Index `i` corresponds to row `i`.
+     */
+    getFonts: () => UnifiedFont[];
+    /**
+     * Returns the active font weight (e.g. 400).
+     */
+    getWeight: () => number;
+    /**
+     * Returns the preview text string.
+     */
+    getPreviewText: () => string;
+    /**
+     * Returns the scroll container's inner width in pixels. Returns 0 before mount.
+     */
+    getContainerWidth: () => number;
+    /**
+     * Returns the font size in pixels (e.g. `controlManager.renderedSize`).
+     */
+    getFontSizePx: () => number;
+    /**
+     * Returns the computed line height in pixels.
+     * Typically `controlManager.height * controlManager.renderedSize`.
+     */
+    getLineHeightPx: () => number;
+    /**
+     * Returns the font load status for a given font key (`'{id}@{weight}'` or `'{id}@vf'`).
+     *
+     * In production: `(key) => appliedFontsManager.statuses.get(key)`.
+     * Injected for testability — avoids a module-level singleton dependency in tests.
+     * The call to `.get()` on a `SvelteMap` must happen inside a `$derived.by` context
+     * for reactivity to work. This is satisfied when `itemHeight` is called by
+     * `createVirtualizer`'s `estimateSize`.
+     */
+    getStatus: (fontKey: string) => FontLoadStatus | undefined;
+    /**
+     * Total horizontal padding of the text content area in pixels.
+     * Use the smallest breakpoint value (mobile `p-4` = 32px) to guarantee
+     * the content width is never over-estimated, keeping the height estimate safe.
+     */
+    contentHorizontalPadding: number;
+    /**
+     * Fixed height in pixels of chrome that is not text content (header bar, etc.).
+     */
+    chromeHeight: number;
+    /**
+     * Height in pixels to return when the font is not loaded or container width is 0.
+     */
+    fallbackHeight: number;
+}
+
+/**
+ * Creates a row-height resolver for `FontSampler` rows in `VirtualList`.
+ *
+ * The returned function is suitable as the `itemHeight` prop of `VirtualList`.
+ * Pass it from the widget layer (`SampleList`) so that typography values from
+ * `controlManager` are injected as getter functions rather than imported directly,
+ * keeping `$entities/Font` free of `$features` dependencies.
+ *
+ * **Reactivity:** When the returned function reads `getStatus()` inside a
+ * `$derived.by` block (as `estimateSize` does in `createVirtualizer`), any
+ * `SvelteMap.get()` call within `getStatus` registers a Svelte 5 dependency.
+ * When a font's status changes to `'loaded'`, `offsets` recomputes automatically —
+ * no DOM snap occurs.
+ *
+ * **Caching:** A `Map` keyed by `fontCssString|text|contentWidth|lineHeightPx`
+ * prevents redundant `TextLayoutEngine.layout()` calls. The cache is invalidated
+ * naturally because a change in any input produces a different cache key.
+ *
+ * @param options - Configuration and getter functions (all injected for testability).
+ * @returns A function `(rowIndex: number) => number` for use as `VirtualList.itemHeight`.
+ */
+export function createFontRowSizeResolver(options: FontRowSizeResolverOptions): (rowIndex: number) => number {
+    const engine = new TextLayoutEngine();
+    // Key: `${fontCssString}|${text}|${contentWidth}|${lineHeightPx}`
+    const cache = new Map<string, number>();
+
+    return function resolveRowHeight(rowIndex: number): number {
+        const fonts = options.getFonts();
+        const font = fonts[rowIndex];
+        if (!font) {
+            return options.fallbackHeight;
+        }
+
+        const containerWidth = options.getContainerWidth();
+        const previewText = options.getPreviewText();
+
+        if (containerWidth <= 0 || !previewText) {
+            return options.fallbackHeight;
+        }
+
+        const weight = options.getWeight();
+        // generateFontKey: '{id}@{weight}' for static fonts, '{id}@vf' for variable fonts.
+        const fontKey = generateFontKey({ id: font.id, weight, isVariable: font.features?.isVariable });
+
+        // Reading via getStatus() allows the caller to pass appliedFontsManager.statuses.get(),
+        // which creates a Svelte 5 reactive dependency when called inside $derived.by.
+        const status = options.getStatus(fontKey);
+        if (status !== 'loaded') {
+            return options.fallbackHeight;
+        }
+
+        const fontSizePx = options.getFontSizePx();
+        const lineHeightPx = options.getLineHeightPx();
+        const contentWidth = containerWidth - options.contentHorizontalPadding;
+        const fontCssString = `${weight} ${fontSizePx}px "${font.name}"`;
+
+        const cacheKey = `${fontCssString}|${previewText}|${contentWidth}|${lineHeightPx}`;
+        const cached = cache.get(cacheKey);
+        if (cached !== undefined) {
+            return cached;
+        }
+
+        const { totalHeight } = engine.layout(previewText, fontCssString, contentWidth, lineHeightPx);
+        const result = totalHeight + options.chromeHeight;
+        cache.set(cacheKey, result);
+        return result;
+    };
+}

src/entities/Font/model/const/const.ts

@@ -1,5 +1,5 @@
 import type { ControlModel } from '$shared/lib';
-import type { ControlId } from '..';
+import type { ControlId } from '../types/typography';
 
 /**
  * Font size constants
@@ -86,3 +86,9 @@ export const DEFAULT_TYPOGRAPHY_CONTROLS_DATA: ControlModel<ControlId>[] = [
 export const MULTIPLIER_S = 0.5;
 export const MULTIPLIER_M = 0.75;
 export const MULTIPLIER_L = 1;
+
+/**
+ * Index value for items not yet loaded in a virtualized list.
+ * Treated as being at the very bottom of the infinite scroll.
+ */
+export const VIRTUAL_INDEX_NOT_LOADED = Infinity;

src/entities/Font/model/index.ts

@@ -1,7 +1,3 @@
-export {
-    appliedFontsManager,
-    createFontStore,
-    FontStore,
-    fontStore,
-} from './store';
+export * from './const/const';
+export * from './store';
 export * from './types';

src/entities/Font/model/store/appliedFontsStore/appliedFontStore.test.ts

@@ -1,10 +1,10 @@
-/** @vitest-environment jsdom */
+/**
+ * @vitest-environment jsdom
+ */
 import { AppliedFontsManager } from './appliedFontsStore.svelte';
 import { FontFetchError } from './errors';
 import { FontEvictionPolicy } from './utils/fontEvictionPolicy/FontEvictionPolicy';
 
-// ── Fake collaborators ────────────────────────────────────────────────────────
-
 class FakeBufferCache {
     async get(_url: string): Promise<ArrayBuffer> {
         return new ArrayBuffer(8);
@@ -13,7 +13,9 @@ class FakeBufferCache {
     clear(): void {}
 }
 
-/** Throws {@link FontFetchError} on every `get()` — simulates network/HTTP failure. */
+/**
+ * Throws {@link FontFetchError} on every `get()` — simulates network/HTTP failure.
+ */
 class FailingBufferCache {
     async get(url: string): Promise<never> {
         throw new FontFetchError(url, new Error('network error'), 500);
@@ -22,8 +24,6 @@ class FailingBufferCache {
     clear(): void {}
 }
 
-// ── Helpers ───────────────────────────────────────────────────────────────────
-
 const makeConfig = (id: string, overrides: Partial<{ weight: number; isVariable: boolean }> = {}) => ({
     id,
     name: id,
@@ -32,8 +32,6 @@ const makeConfig = (id: string, overrides: Partial<{ weight: number; isVariable:
     ...overrides,
 });
 
-// ── Suite ─────────────────────────────────────────────────────────────────────
-
 describe('AppliedFontsManager', () => {
     let manager: AppliedFontsManager;
     let eviction: FontEvictionPolicy;
@@ -66,8 +64,6 @@ describe('AppliedFontsManager', () => {
         vi.unstubAllGlobals();
     });
 
-    // ── touch() ───────────────────────────────────────────────────────────────
-
     describe('touch()', () => {
         it('queues and loads a new font', async () => {
             manager.touch([makeConfig('roboto')]);
@@ -131,8 +127,6 @@ describe('AppliedFontsManager', () => {
         });
     });
 
-    // ── queue processing ──────────────────────────────────────────────────────
-
     describe('queue processing', () => {
         it('filters non-critical weights in data-saver mode', async () => {
             (navigator as any).connection = { saveData: true };
@@ -163,8 +157,6 @@ describe('AppliedFontsManager', () => {
         });
     });
 
-    // ── Phase 1: fetch ────────────────────────────────────────────────────────
-
     describe('Phase 1 — fetch', () => {
         it('sets status to error on fetch failure', async () => {
             const consoleSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
@@ -209,8 +201,6 @@ describe('AppliedFontsManager', () => {
         });
     });
 
-    // ── Phase 2: parse ────────────────────────────────────────────────────────
-
     describe('Phase 2 — parse', () => {
         it('sets status to error on parse failure', async () => {
             const consoleSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
@@ -241,8 +231,6 @@ describe('AppliedFontsManager', () => {
         });
     });
 
-    // ── #purgeUnused ──────────────────────────────────────────────────────────
-
     describe('#purgeUnused', () => {
         it('evicts fonts after TTL expires', async () => {
             manager.touch([makeConfig('ephemeral')]);
@@ -300,8 +288,6 @@ describe('AppliedFontsManager', () => {
         });
     });
 
-    // ── destroy() ─────────────────────────────────────────────────────────────
-
     describe('destroy()', () => {
         it('clears all statuses', async () => {
             manager.touch([makeConfig('roboto')]);

src/entities/Font/model/store/appliedFontsStore/appliedFontsStore.svelte.ts

@@ -156,7 +156,9 @@ export class AppliedFontsManager {
         }
     }
 
-    /** Returns true if data-saver mode is enabled (defers non-critical weights). */
+    /**
+     * Returns true if data-saver mode is enabled (defers non-critical weights).
+     */
     #shouldDeferNonCritical(): boolean {
         return (navigator as any).connection?.saveData === true;
     }
@@ -188,13 +190,11 @@ export class AppliedFontsManager {
         const concurrency = getEffectiveConcurrency();
         const buffers = new Map<string, ArrayBuffer>();
 
-        // ==================== PHASE 1: Concurrent Fetching ====================
         // Fetch multiple font files in parallel since network I/O is non-blocking
         for (let i = 0; i < entries.length; i += concurrency) {
             await this.#fetchChunk(entries.slice(i, i + concurrency), buffers);
         }
 
-        // ==================== PHASE 2: Sequential Parsing ====================
         // Parse buffers one at a time with periodic yields to avoid blocking UI
         const hasInputPending = !!(navigator as any).scheduling?.isInputPending;
         let lastYield = performance.now();
@@ -246,12 +246,16 @@ export class AppliedFontsManager {
         );
 
         for (const result of results) {
-            if (result.ok) continue;
+            if (result.ok) {
+                continue;
+            }
             const { key, config, reason } = result;
             const isAbort = reason instanceof FontFetchError
                 && reason.cause instanceof Error
                 && reason.cause.name === 'AbortError';
-            if (isAbort) continue;
+            if (isAbort) {
+                continue;
+            }
             if (reason instanceof FontFetchError) {
                 console.error(`Font fetch failed: ${config.name}`, reason);
             }
@@ -279,7 +283,9 @@ export class AppliedFontsManager {
         }
     }
 
-    /** Removes fonts unused within TTL (LRU-style cleanup). Runs every PURGE_INTERVAL. Pinned fonts are never evicted. */
+    /**
+     * Removes fonts unused within TTL (LRU-style cleanup). Runs every PURGE_INTERVAL. Pinned fonts are never evicted.
+     */
     #purgeUnused() {
         const now = Date.now();
         // Iterate through all tracked font keys
@@ -291,7 +297,9 @@ export class AppliedFontsManager {
 
             // Remove FontFace from document to free memory
             const font = this.#loadedFonts.get(key);
-            if (font) document.fonts.delete(font);
+            if (font) {
+                document.fonts.delete(font);
+            }
 
             // Evict from cache and cleanup URL mapping
             const url = this.#urlByKey.get(key);
@@ -307,7 +315,9 @@ export class AppliedFontsManager {
         }
     }
 
-    /** Returns current loading status for a font, or undefined if never requested. */
+    /**
+     * Returns current loading status for a font, or undefined if never requested.
+     */
     getFontStatus(id: string, weight: number, isVariable = false) {
         try {
             return this.statuses.get(generateFontKey({ id, weight, isVariable }));
@@ -316,17 +326,23 @@ export class AppliedFontsManager {
         }
     }
 
-    /** Pins a font so it is never evicted by #purgeUnused(), regardless of TTL. */
+    /**
+     * Pins a font so it is never evicted by #purgeUnused(), regardless of TTL.
+     */
     pin(id: string, weight: number, isVariable = false): void {
         this.#eviction.pin(generateFontKey({ id, weight, isVariable }));
     }
 
-    /** Unpins a font, allowing it to be evicted by #purgeUnused() once its TTL expires. */
+    /**
+     * Unpins a font, allowing it to be evicted by #purgeUnused() once its TTL expires.
+     */
     unpin(id: string, weight: number, isVariable = false): void {
         this.#eviction.unpin(generateFontKey({ id, weight, isVariable }));
     }
 
-    /** Waits for all fonts to finish loading using document.fonts.ready. */
+    /**
+     * Waits for all fonts to finish loading using document.fonts.ready.
+     */
     async ready(): Promise<void> {
         if (typeof document === 'undefined') {
             return;
@@ -336,7 +352,9 @@ export class AppliedFontsManager {
         } catch { /* document unloaded */ }
     }
 
-    /** Aborts all operations, removes fonts from document, and clears state. Manager cannot be reused after. */
+    /**
+     * Aborts all operations, removes fonts from document, and clears state. Manager cannot be reused after.
+     */
     destroy() {
         // Abort all in-flight network requests
         this.#abortController.abort();
@@ -375,5 +393,7 @@ export class AppliedFontsManager {
     }
 }
 
-/** Singleton instance — use throughout the application for unified font loading state. */
+/**
+ * Singleton instance — use throughout the application for unified font loading state.
+ */
 export const appliedFontsManager = new AppliedFontsManager();

src/entities/Font/model/store/appliedFontsStore/utils/fontBufferCache/FontBufferCache.test.ts

@@ -1,4 +1,6 @@
-/** @vitest-environment jsdom */
+/**
+ * @vitest-environment jsdom
+ */
 import { FontFetchError } from '../../errors';
 import { FontBufferCache } from './FontBufferCache';
 

src/entities/Font/model/store/appliedFontsStore/utils/fontBufferCache/FontBufferCache.ts

@@ -3,9 +3,13 @@ import { FontFetchError } from '../../errors';
 type Fetcher = (url: string, init?: RequestInit) => Promise<Response>;
 
 interface FontBufferCacheOptions {
-    /** Custom fetch implementation. Defaults to `globalThis.fetch`. Inject in tests for isolation. */
+    /**
+     * Custom fetch implementation. Defaults to `globalThis.fetch`. Inject in tests for isolation.
+     */
     fetcher?: Fetcher;
-    /** Cache API cache name. Defaults to `'font-cache-v1'`. */
+    /**
+     * Cache API cache name. Defaults to `'font-cache-v1'`.
+     */
     cacheName?: string;
 }
 
@@ -85,12 +89,16 @@ export class FontBufferCache {
         return buffer;
     }
 
-    /** Removes a URL from the in-memory cache. Next call to `get()` will re-fetch. */
+    /**
+     * Removes a URL from the in-memory cache. Next call to `get()` will re-fetch.
+     */
     evict(url: string): void {
         this.#buffersByUrl.delete(url);
     }
 
-    /** Clears all in-memory cached buffers. */
+    /**
+     * Clears all in-memory cached buffers.
+     */
     clear(): void {
         this.#buffersByUrl.clear();
     }

src/entities/Font/model/store/appliedFontsStore/utils/fontEvictionPolicy/FontEvictionPolicy.ts

@@ -1,5 +1,7 @@
 interface FontEvictionPolicyOptions {
-    /** TTL in milliseconds. Defaults to 5 minutes. */
+    /**
+     * TTL in milliseconds. Defaults to 5 minutes.
+     */
     ttl?: number;
 }
 
@@ -28,12 +30,16 @@ export class FontEvictionPolicy {
         this.#usageTracker.set(key, now);
     }
 
-    /** Pins a font key so it is never evicted regardless of TTL. */
+    /**
+     * Pins a font key so it is never evicted regardless of TTL.
+     */
     pin(key: string): void {
         this.#pinnedFonts.add(key);
     }
 
-    /** Unpins a font key, allowing it to be evicted once its TTL expires. */
+    /**
+     * Unpins a font key, allowing it to be evicted once its TTL expires.
+     */
     unpin(key: string): void {
         this.#pinnedFonts.delete(key);
     }
@@ -57,18 +63,24 @@ export class FontEvictionPolicy {
         return now - lastUsed >= this.#TTL;
     }
 
-    /** Returns an iterator over all tracked font keys. */
+    /**
+     * Returns an iterator over all tracked font keys.
+     */
     keys(): IterableIterator<string> {
         return this.#usageTracker.keys();
     }
 
-    /** Removes a font key from tracking. Called by the orchestrator after eviction. */
+    /**
+     * Removes a font key from tracking. Called by the orchestrator after eviction.
+     */
     remove(key: string): void {
         this.#usageTracker.delete(key);
         this.#pinnedFonts.delete(key);
     }
 
-    /** Clears all usage timestamps and pinned keys. */
+    /**
+     * Clears all usage timestamps and pinned keys.
+     */
     clear(): void {
         this.#usageTracker.clear();
         this.#pinnedFonts.clear();

src/entities/Font/model/store/appliedFontsStore/utils/fontLoadQueue/FontLoadQueue.ts

@@ -34,22 +34,30 @@ export class FontLoadQueue {
         return entries;
     }
 
-    /** Returns `true` if the key is currently in the queue. */
+    /**
+     * Returns `true` if the key is currently in the queue.
+     */
     has(key: string): boolean {
         return this.#queue.has(key);
     }
 
-    /** Increments the retry count for a font key. */
+    /**
+     * Increments the retry count for a font key.
+     */
     incrementRetry(key: string): void {
         this.#retryCounts.set(key, (this.#retryCounts.get(key) ?? 0) + 1);
     }
 
-    /** Returns `true` if the font has reached or exceeded the maximum retry limit. */
+    /**
+     * Returns `true` if the font has reached or exceeded the maximum retry limit.
+     */
     isMaxRetriesReached(key: string): boolean {
         return (this.#retryCounts.get(key) ?? 0) >= this.#MAX_RETRIES;
     }
 
-    /** Clears all queued fonts and resets all retry counts. */
+    /**
+     * Clears all queued fonts and resets all retry counts.
+     */
     clear(): void {
         this.#queue.clear();
         this.#retryCounts.clear();

src/entities/Font/model/store/appliedFontsStore/utils/loadFont/loadFont.test.ts

@@ -1,4 +1,6 @@
-/** @vitest-environment jsdom */
+/**
+ * @vitest-environment jsdom
+ */
 import { FontParseError } from '../../errors';
 import { loadFont } from './loadFont';
 

src/entities/Font/model/store/batchFontStore.svelte.ts

@@ -0,0 +1,93 @@
+import { fontKeys } from '$shared/api/queryKeys';
+import { BaseQueryStore } from '$shared/lib/helpers/BaseQueryStore.svelte';
+import {
+    fetchFontsByIds,
+    seedFontCache,
+} from '../../api/proxy/proxyFonts';
+import {
+    FontNetworkError,
+    FontResponseError,
+} from '../../lib/errors/errors';
+import type { UnifiedFont } from '../../model/types';
+
+/**
+ * Internal fetcher that seeds the cache and handles error wrapping.
+ * Standalone function to avoid 'this' issues during construction.
+ */
+async function fetchAndSeed(ids: string[]): Promise<UnifiedFont[]> {
+    if (ids.length === 0) {
+        return [];
+    }
+
+    let response: UnifiedFont[];
+    try {
+        response = await fetchFontsByIds(ids);
+    } catch (cause) {
+        throw new FontNetworkError(cause);
+    }
+
+    if (!response || !Array.isArray(response)) {
+        throw new FontResponseError('batchResponse', response);
+    }
+
+    seedFontCache(response);
+    return response;
+}
+
+/**
+ * Reactive store for fetching and caching batches of fonts by ID.
+ * Integrates with TanStack Query via BaseQueryStore and handles
+ * normalized cache seeding.
+ */
+export class BatchFontStore extends BaseQueryStore<UnifiedFont[]> {
+    constructor(initialIds: string[] = []) {
+        super({
+            queryKey: fontKeys.batch(initialIds),
+            queryFn: () => fetchAndSeed(initialIds),
+            enabled: initialIds.length > 0,
+            retry: false,
+        });
+    }
+
+    /**
+     * Updates the IDs to fetch. Triggers a new query.
+     *
+     * @param ids - Array of font IDs
+     */
+    setIds(ids: string[]): void {
+        this.updateOptions({
+            queryKey: fontKeys.batch(ids),
+            queryFn: () => fetchAndSeed(ids),
+            enabled: ids.length > 0,
+            retry: false,
+        });
+    }
+
+    /**
+     * Array of fetched fonts
+     */
+    get fonts(): UnifiedFont[] {
+        return this.result.data ?? [];
+    }
+
+    /**
+     * Whether the query is currently loading
+     */
+    get isLoading(): boolean {
+        return this.result.isLoading;
+    }
+
+    /**
+     * Whether the query encountered an error
+     */
+    get isError(): boolean {
+        return this.result.isError;
+    }
+
+    /**
+     * The error object if the query failed
+     */
+    get error(): Error | null {
+        return (this.result.error as Error) ?? null;
+    }
+}

src/entities/Font/model/store/batchFontStore.test.ts

@@ -0,0 +1,107 @@
+import { queryClient } from '$shared/api/queryClient';
+import { fontKeys } from '$shared/api/queryKeys';
+import {
+    beforeEach,
+    describe,
+    expect,
+    it,
+    vi,
+} from 'vitest';
+import * as api from '../../api/proxy/proxyFonts';
+import {
+    FontNetworkError,
+    FontResponseError,
+} from '../../lib/errors/errors';
+import { BatchFontStore } from './batchFontStore.svelte';
+
+describe('BatchFontStore', () => {
+    beforeEach(() => {
+        queryClient.clear();
+        vi.clearAllMocks();
+    });
+
+    describe('Fetch Behavior', () => {
+        it('should skip fetch when initialized with empty IDs', async () => {
+            const spy = vi.spyOn(api, 'fetchFontsByIds');
+            const store = new BatchFontStore([]);
+            expect(spy).not.toHaveBeenCalled();
+            expect(store.fonts).toEqual([]);
+        });
+
+        it('should fetch and seed cache for valid IDs', async () => {
+            const fonts = [{ id: 'a', name: 'A' }] as any[];
+            vi.spyOn(api, 'fetchFontsByIds').mockResolvedValue(fonts);
+            const store = new BatchFontStore(['a']);
+            await vi.waitFor(() => expect(store.fonts).toEqual(fonts), { timeout: 1000 });
+            expect(queryClient.getQueryData(fontKeys.detail('a'))).toEqual(fonts[0]);
+        });
+    });
+
+    describe('Loading States', () => {
+        it('should transition through loading state', async () => {
+            vi.spyOn(api, 'fetchFontsByIds').mockImplementation(() =>
+                new Promise(r => setTimeout(() => r([{ id: 'a' }] as any), 50))
+            );
+            const store = new BatchFontStore(['a']);
+            expect(store.isLoading).toBe(true);
+            await vi.waitFor(() => expect(store.isLoading).toBe(false), { timeout: 1000 });
+        });
+    });
+
+    describe('Error Handling', () => {
+        it('should wrap network failures in FontNetworkError', async () => {
+            vi.spyOn(api, 'fetchFontsByIds').mockRejectedValue(new Error('Network fail'));
+            const store = new BatchFontStore(['a']);
+            await vi.waitFor(() => expect(store.isError).toBe(true), { timeout: 1000 });
+            expect(store.error).toBeInstanceOf(FontNetworkError);
+        });
+
+        it('should handle malformed API responses with FontResponseError', async () => {
+            // Mocking a malformed response that the store should validate
+            vi.spyOn(api, 'fetchFontsByIds').mockResolvedValue(null as any);
+            const store = new BatchFontStore(['a']);
+            await vi.waitFor(() => expect(store.isError).toBe(true), { timeout: 1000 });
+            expect(store.error).toBeInstanceOf(FontResponseError);
+        });
+
+        it('should have null error in success state', async () => {
+            const fonts = [{ id: 'a' }] as any[];
+            vi.spyOn(api, 'fetchFontsByIds').mockResolvedValue(fonts);
+            const store = new BatchFontStore(['a']);
+            await vi.waitFor(() => expect(store.fonts).toEqual(fonts), { timeout: 1000 });
+            expect(store.error).toBeNull();
+        });
+    });
+
+    describe('Disable Behavior', () => {
+        it('should return empty fonts and not fetch when setIds is called with empty array', async () => {
+            const fonts1 = [{ id: 'a' }] as any[];
+            const spy = vi.spyOn(api, 'fetchFontsByIds').mockResolvedValueOnce(fonts1);
+
+            const store = new BatchFontStore(['a']);
+            await vi.waitFor(() => expect(store.fonts).toEqual(fonts1), { timeout: 1000 });
+
+            spy.mockClear();
+            store.setIds([]);
+
+            await vi.waitFor(() => expect(store.fonts).toEqual([]), { timeout: 1000 });
+            expect(spy).not.toHaveBeenCalled();
+        });
+    });
+
+    describe('Reactivity', () => {
+        it('should refetch when setIds is called', async () => {
+            const fonts1 = [{ id: 'a' }] as any[];
+            const fonts2 = [{ id: 'b' }] as any[];
+            vi.spyOn(api, 'fetchFontsByIds')
+                .mockResolvedValueOnce(fonts1)
+                .mockResolvedValueOnce(fonts2);
+
+            const store = new BatchFontStore(['a']);
+            await vi.waitFor(() => expect(store.fonts).toEqual(fonts1), { timeout: 1000 });
+
+            store.setIds(['b']);
+            await vi.waitFor(() => expect(store.fonts).toEqual(fonts2), { timeout: 1000 });
+        });
+    });
+});

src/entities/Font/model/store/fontStore/fontStore.svelte.spec.ts

@@ -61,7 +61,6 @@ describe('FontStore', () => {
         vi.resetAllMocks();
     });
 
-    // -----------------------------------------------------------------------
     describe('construction', () => {
         it('stores initial params', () => {
             const store = makeStore({ limit: 20 });
@@ -90,7 +89,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('state after fetch', () => {
         it('exposes loaded fonts', async () => {
             const store = await fetchedStore({}, generateMockFonts(7));
@@ -129,7 +127,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('error states', () => {
         it('isError is false before any fetch', () => {
             const store = makeStore();
@@ -178,7 +175,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('font accumulation', () => {
         it('replaces fonts when refetching the first page', async () => {
             const store = makeStore();
@@ -212,7 +208,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('pagination state', () => {
         it('returns zero-value defaults before any fetch', () => {
             const store = makeStore();
@@ -248,7 +243,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('setParams', () => {
         it('merges updates into existing params', () => {
             const store = makeStore({ limit: 10 });
@@ -266,7 +260,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('filter change resets', () => {
         it('clears accumulated fonts when a filter changes', async () => {
             const store = await fetchedStore({}, generateMockFonts(5));
@@ -302,7 +295,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('staleTime in buildOptions', () => {
         it('is 5 minutes with no active filters', () => {
             const store = makeStore();
@@ -331,7 +323,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('buildQueryKey', () => {
         it('omits empty-string params', () => {
             const store = makeStore();
@@ -366,7 +357,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('destroy', () => {
         it('does not throw', () => {
             const store = makeStore();
@@ -380,7 +370,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('refetch', () => {
         it('triggers a fetch', async () => {
             const store = makeStore();
@@ -400,7 +389,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('nextPage', () => {
         let store: FontStore;
 
@@ -437,7 +425,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('prevPage and goToPage', () => {
         it('prevPage is a no-op — infinite scroll does not support backward navigation', async () => {
             const store = await fetchedStore({}, generateMockFonts(5));
@@ -454,7 +441,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('prefetch', () => {
         it('triggers a fetch for the provided params', async () => {
             const store = makeStore();
@@ -465,7 +451,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('getCachedData / setQueryData', () => {
         it('getCachedData returns undefined before any fetch', () => {
             queryClient.clear();
@@ -497,7 +482,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('invalidate', () => {
         it('calls invalidateQueries', async () => {
             const store = await fetchedStore();
@@ -508,7 +492,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('setLimit', () => {
         it('updates the limit param', () => {
             const store = makeStore({ limit: 10 });
@@ -518,7 +501,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('filter shortcut methods', () => {
         let store: FontStore;
 
@@ -561,7 +543,6 @@ describe('FontStore', () => {
         });
     });
 
-    // -----------------------------------------------------------------------
     describe('category getters', () => {
         it('each getter returns only fonts of that category', async () => {
             const fonts = generateMixedCategoryFonts(2); // 2 of each category = 10 total
@@ -580,4 +561,67 @@ describe('FontStore', () => {
             store.destroy();
         });
     });
+
+    describe('fetchAllPagesTo', () => {
+        beforeEach(() => {
+            fetch.mockReset();
+            queryClient.clear();
+        });
+
+        it('fetches all missing pages in parallel up to targetIndex', async () => {
+            // First page already loaded (offset 0, limit 10, total 50)
+            const firstFonts = generateMockFonts(10);
+            fetch.mockResolvedValueOnce(makeResponse(firstFonts, { total: 50, limit: 10, offset: 0 }));
+            const store = makeStore();
+            await store.refetch();
+            flushSync();
+
+            expect(store.fonts).toHaveLength(10);
+
+            // Mock remaining pages
+            for (let offset = 10; offset < 50; offset += 10) {
+                fetch.mockResolvedValueOnce(
+                    makeResponse(generateMockFonts(10), { total: 50, limit: 10, offset }),
+                );
+            }
+
+            await store.fetchAllPagesTo(40);
+            flushSync();
+
+            expect(store.fonts).toHaveLength(50);
+        });
+
+        it('skips pages that fail and still merges successful ones', async () => {
+            const firstFonts = generateMockFonts(10);
+            fetch.mockResolvedValueOnce(makeResponse(firstFonts, { total: 30, limit: 10, offset: 0 }));
+            const store = makeStore();
+            await store.refetch();
+            flushSync();
+
+            // offset=10 fails, offset=20 succeeds
+            fetch.mockRejectedValueOnce(new Error('network error'));
+            fetch.mockResolvedValueOnce(
+                makeResponse(generateMockFonts(10), { total: 30, limit: 10, offset: 20 }),
+            );
+
+            await store.fetchAllPagesTo(25);
+            flushSync();
+
+            // Page at offset=20 merged, page at offset=10 missing — 20 total
+            expect(store.fonts).toHaveLength(20);
+        });
+
+        it('is a no-op when target is within already-loaded data', async () => {
+            const firstFonts = generateMockFonts(10);
+            fetch.mockResolvedValueOnce(makeResponse(firstFonts, { total: 50, limit: 10, offset: 0 }));
+            const store = makeStore();
+            await store.refetch();
+            flushSync();
+
+            const callsBefore = fetch.mock.calls.length;
+            await store.fetchAllPagesTo(5);
+
+            expect(fetch.mock.calls.length).toBe(callsBefore);
+        });
+    });
 });

src/entities/Font/model/store/fontStore/fontStore.svelte.ts

@@ -18,7 +18,9 @@ import type { UnifiedFont } from '../../types';
 
 type PageParam = { offset: number };
 
-/** Filter params + limit — offset is managed by TQ as a page param, not a user param. */
+/**
+ * Filter params + limit — offset is managed by TQ as a page param, not a user param.
+ */
 type FontStoreParams = Omit<ProxyFontsParams, 'offset'>;
 
 type FontStoreResult = InfiniteQueryObserverResult<InfiniteData<ProxyFontsResponse, PageParam>, Error>;
@@ -44,34 +46,53 @@ export class FontStore {
         });
     }
 
-    // -- Public state --
-
+    /**
+     * Current filter and limit configuration
+     */
     get params(): FontStoreParams {
         return this.#params;
     }
+    /**
+     * Flattened list of all fonts loaded across all pages (reactive)
+     */
     get fonts(): UnifiedFont[] {
         return this.#result.data?.pages.flatMap((p: ProxyFontsResponse) => p.fonts) ?? [];
     }
+    /**
+     * True if the first page is currently being fetched
+     */
     get isLoading(): boolean {
         return this.#result.isLoading;
     }
+    /**
+     * True if any background fetch is in progress (initial or pagination)
+     */
     get isFetching(): boolean {
         return this.#result.isFetching;
     }
+    /**
+     * True if the last fetch attempt resulted in an error
+     */
     get isError(): boolean {
         return this.#result.isError;
     }
 
+    /**
+     * Last caught error from the query observer
+     */
     get error(): Error | null {
         return this.#result.error ?? null;
     }
-    // isEmpty is false during loading/fetching so the UI never flashes "no results"
-    // while a fetch is in progress. The !isFetching guard is specifically for the filter-change
-    // transition: fonts clear synchronously → isFetching becomes true → isEmpty stays false.
+    /**
+     * True if no fonts were found for the current filter criteria
+     */
     get isEmpty(): boolean {
         return !this.isLoading && !this.isFetching && this.fonts.length === 0;
     }
 
+    /**
+     * Pagination metadata derived from the last loaded page
+     */
     get pagination() {
         const pages = this.#result.data?.pages;
         const last = pages?.at(-1);
@@ -95,45 +116,65 @@ export class FontStore {
         };
     }
 
-    // -- Lifecycle --
-
+    /**
+     * Cleans up subscriptions and destroys the observer
+     */
     destroy() {
         this.#unsubscribe();
         this.#observer.destroy();
     }
 
-    // -- Param management --
-
+    /**
+     * Merge new parameters into existing state and trigger a refetch
+     */
     setParams(updates: Partial<FontStoreParams>) {
         this.#params = { ...this.#params, ...updates };
         this.#observer.setOptions(this.buildOptions());
     }
+    /**
+     * Forcefully invalidate and refetch the current query from the network
+     */
     invalidate() {
         this.#qc.invalidateQueries({ queryKey: this.buildQueryKey(this.#params) });
     }
 
-    // -- Async operations --
-
+    /**
+     * Manually trigger a query refetch
+     */
     async refetch() {
         await this.#observer.refetch();
     }
 
+    /**
+     * Prime the cache with data for a specific parameter set
+     */
     async prefetch(params: FontStoreParams) {
         await this.#qc.prefetchInfiniteQuery(this.buildOptions(params));
     }
 
+    /**
+     * Abort any active network requests for this store
+     */
     cancel() {
         this.#qc.cancelQueries({ queryKey: this.buildQueryKey(this.#params) });
     }
 
+    /**
+     * Retrieve current font list from cache without triggering a fetch
+     */
     getCachedData(): UnifiedFont[] | undefined {
         const data = this.#qc.getQueryData<InfiniteData<ProxyFontsResponse, PageParam>>(
             this.buildQueryKey(this.#params),
         );
-        if (!data) return undefined;
+        if (!data) {
+            return undefined;
+        }
         return data.pages.flatMap(p => p.fonts);
     }
 
+    /**
+     * Manually update the cached font data (useful for optimistic updates)
+     */
     setQueryData(updater: (old: UnifiedFont[] | undefined) => UnifiedFont[]) {
         const key = this.buildQueryKey(this.#params);
         this.#qc.setQueryData<InfiniteData<ProxyFontsResponse, PageParam>>(
@@ -164,55 +205,191 @@ export class FontStore {
         );
     }
 
-    // -- Filter shortcuts --
-
+    /**
+     * Shortcut to update provider filters
+     */
     setProviders(v: ProxyFontsParams['providers']) {
         this.setParams({ providers: v });
     }
+    /**
+     * Shortcut to update category filters
+     */
     setCategories(v: ProxyFontsParams['categories']) {
         this.setParams({ categories: v });
     }
+    /**
+     * Shortcut to update subset filters
+     */
     setSubsets(v: ProxyFontsParams['subsets']) {
         this.setParams({ subsets: v });
     }
+    /**
+     * Shortcut to update search query
+     */
     setSearch(v: string) {
         this.setParams({ q: v || undefined });
     }
+    /**
+     * Shortcut to update sort order
+     */
     setSort(v: ProxyFontsParams['sort']) {
         this.setParams({ sort: v });
     }
 
-    // -- Pagination navigation --
-
+    /**
+     * Fetch the next page of results if available
+     */
     async nextPage(): Promise<void> {
         await this.#observer.fetchNextPage();
     }
-    prevPage(): void {} // no-op: infinite scroll accumulates forward only; method kept for API compatibility
-    goToPage(_page: number): void {} // no-op
 
+    #isCatchingUp = false;
+    #inFlightOffsets = new Set<number>();
+
+    /**
+     * Fetch all pages between the current loaded count and targetIndex in parallel.
+     * Pages are merged into the cache as they arrive (sorted by offset).
+     * Failed pages are silently skipped — normal scroll will re-fetch them on demand.
+     */
+    async fetchAllPagesTo(targetIndex: number): Promise<void> {
+        if (this.#isCatchingUp) {
+            return;
+        }
+
+        const pageSize = typeof this.#params.limit === 'number' ? this.#params.limit : 50;
+        const key = this.buildQueryKey(this.#params);
+        const existing = this.#qc.getQueryData<InfiniteData<ProxyFontsResponse, PageParam>>(key);
+
+        if (!existing) {
+            return;
+        }
+
+        const loadedOffsets = new Set(existing.pageParams.map(p => p.offset));
+
+        // Collect offsets for all missing and not-in-flight pages
+        const missingOffsets: number[] = [];
+        for (let offset = 0; offset <= targetIndex; offset += pageSize) {
+            if (!loadedOffsets.has(offset) && !this.#inFlightOffsets.has(offset)) {
+                missingOffsets.push(offset);
+            }
+        }
+
+        if (missingOffsets.length === 0) {
+            return;
+        }
+
+        this.#isCatchingUp = true;
+
+        // Sorted merge buffer — flush in offset order as pages arrive
+        const buffer = new Map<number, ProxyFontsResponse>();
+        const failed = new Set<number>();
+        let nextFlushOffset = (existing.pageParams.at(-1)?.offset ?? -pageSize) + pageSize;
+
+        const flush = () => {
+            while (buffer.has(nextFlushOffset) || failed.has(nextFlushOffset)) {
+                if (buffer.has(nextFlushOffset)) {
+                    this.#appendPageToCache(buffer.get(nextFlushOffset)!);
+                    buffer.delete(nextFlushOffset);
+                }
+                failed.delete(nextFlushOffset);
+                nextFlushOffset += pageSize;
+            }
+        };
+
+        try {
+            await Promise.allSettled(
+                missingOffsets.map(async offset => {
+                    this.#inFlightOffsets.add(offset);
+                    try {
+                        const page = await this.fetchPage({ ...this.#params, offset });
+                        buffer.set(offset, page);
+                    } catch {
+                        failed.add(offset);
+                    } finally {
+                        this.#inFlightOffsets.delete(offset);
+                    }
+                    flush();
+                }),
+            );
+        } finally {
+            this.#isCatchingUp = false;
+        }
+    }
+
+    /**
+     * Backward pagination (no-op: infinite scroll accumulates forward only)
+     */
+    prevPage(): void {}
+    /**
+     * Jump to specific page (no-op for infinite scroll)
+     */
+    goToPage(_page: number): void {}
+
+    /**
+     * Update the number of items fetched per page
+     */
     setLimit(limit: number) {
         this.setParams({ limit });
     }
 
-    // -- Category views --
-
+    /**
+     * Derived list of sans-serif fonts in the current set
+     */
     get sansSerifFonts() {
         return this.fonts.filter(f => f.category === 'sans-serif');
     }
+    /**
+     * Derived list of serif fonts in the current set
+     */
     get serifFonts() {
         return this.fonts.filter(f => f.category === 'serif');
     }
+    /**
+     * Derived list of display fonts in the current set
+     */
     get displayFonts() {
         return this.fonts.filter(f => f.category === 'display');
     }
+    /**
+     * Derived list of handwriting fonts in the current set
+     */
     get handwritingFonts() {
         return this.fonts.filter(f => f.category === 'handwriting');
     }
+    /**
+     * Derived list of monospace fonts in the current set
+     */
     get monospaceFonts() {
         return this.fonts.filter(f => f.category === 'monospace');
     }
 
-    // -- Private helpers (TypeScript-private so tests can spy via `as any`) --
+    /**
+     * Merge a single page into the InfiniteQuery cache in offset order.
+     * Called by fetchAllPagesTo as each parallel fetch resolves.
+     */
+    #appendPageToCache(page: ProxyFontsResponse): void {
+        const key = this.buildQueryKey(this.#params);
+        const existing = this.#qc.getQueryData<InfiniteData<ProxyFontsResponse, PageParam>>(key);
+        if (!existing) {
+            return;
+        }
+
+        // Guard against duplicates
+        const loadedOffsets = new Set(existing.pageParams.map(p => p.offset));
+        if (loadedOffsets.has(page.offset)) {
+            return;
+        }
+
+        const allPages = [...existing.pages, page].sort((a, b) => a.offset - b.offset);
+        const allParams = [...existing.pageParams, { offset: page.offset }].sort(
+            (a, b) => a.offset - b.offset,
+        );
+
+        this.#qc.setQueryData<InfiniteData<ProxyFontsResponse, PageParam>>(key, {
+            pages: allPages,
+            pageParams: allParams,
+        });
+    }
 
     private buildQueryKey(params: FontStoreParams): readonly unknown[] {
         const filtered: Record<string, any> = {};
@@ -263,9 +440,15 @@ export class FontStore {
             throw new FontNetworkError(cause);
         }
 
-        if (!response) throw new FontResponseError('response', response);
-        if (!response.fonts) throw new FontResponseError('response.fonts', response.fonts);
-        if (!Array.isArray(response.fonts)) throw new FontResponseError('response.fonts', response.fonts);
+        if (!response) {
+            throw new FontResponseError('response', response);
+        }
+        if (!response.fonts) {
+            throw new FontResponseError('response.fonts', response.fonts);
+        }
+        if (!Array.isArray(response.fonts)) {
+            throw new FontResponseError('response.fonts', response.fonts);
+        }
 
         return {
             fonts: response.fonts,

src/entities/Font/model/store/index.ts

@@ -1,5 +1,8 @@
 // Applied fonts manager
-export { appliedFontsManager } from './appliedFontsStore/appliedFontsStore.svelte';
+export * from './appliedFontsStore/appliedFontsStore.svelte';
+
+// Batch font store
+export { BatchFontStore } from './batchFontStore.svelte';
 
 // Single FontStore
 export {

src/entities/Font/model/types/font.ts

@@ -31,18 +31,28 @@ export type FontSubset = 'latin' | 'latin-ext' | 'cyrillic' | 'greek' | 'arabic'
  * Combined filter state for font queries
  */
 export interface FontFilters {
-    /** Selected font providers */
+    /**
+     * Active font providers to fetch from
+     */
     providers: FontProvider[];
-    /** Selected font categories */
+    /**
+     * Visual classifications (sans, serif, etc.)
+     */
     categories: FontCategory[];
-    /** Selected character subsets */
+    /**
+     * Character sets required for the sample text
+     */
     subsets: FontSubset[];
 }
 
-/** Filter group identifier */
+/**
+ * Filter group identifier
+ */
 export type FilterGroup = 'providers' | 'categories' | 'subsets';
 
-/** Filter type including search query */
+/**
+ * Filter type including search query
+ */
 export type FilterType = FilterGroup | 'searchQuery';
 
 /**
@@ -80,15 +90,25 @@ export type UnifiedFontVariant = FontVariant;
  * Font style URLs
  */
 export interface FontStyleUrls {
-    /** Regular weight URL */
+    /**
+     * URL for the regular (400) weight
+     */
     regular?: string;
-    /** Italic URL */
+    /**
+     * URL for the italic (400) style
+     */
     italic?: string;
-    /** Bold weight URL */
+    /**
+     * URL for the bold (700) weight
+     */
     bold?: string;
-    /** Bold italic URL */
+    /**
+     * URL for the bold-italic (700) style
+     */
     boldItalic?: string;
-    /** Additional variant mapping */
+    /**
+     * Mapping for all other numeric/custom variants
+     */
     variants?: Partial<Record<UnifiedFontVariant, string>>;
 }
 
@@ -96,19 +116,24 @@ export interface FontStyleUrls {
  * Font metadata
  */
 export interface FontMetadata {
-    /** Timestamp when font was cached */
+    /**
+     * Epoch timestamp of last successful fetch
+     */
     cachedAt: number;
-    /** Font version from provider */
+    /**
+     * Semantic version string from upstream
+     */
     version?: string;
-    /** Last modified date from provider */
+    /**
+     * ISO date string of last remote update
+     */
     lastModified?: string;
-    /** Popularity rank (if available from provider) */
+    /**
+     * Raw ranking integer from provider
+     */
     popularity?: number;
     /**
-     * Normalized popularity score (0-100)
-     *
-     * Normalized across all fonts for consistent ranking
-     * Higher values indicate more popular fonts
+     * Normalized score (0-100) used for global sorting
      */
     popularityScore?: number;
 }
@@ -117,17 +142,38 @@ export interface FontMetadata {
  * Font features (variable fonts, axes, tags)
  */
 export interface FontFeatures {
-    /** Whether this is a variable font */
+    /**
+     * Whether the font supports fluid weight/width axes
+     */
     isVariable?: boolean;
-    /** Variable font axes (for Fontshare) */
+    /**
+     * Definable axes for variable font interpolation
+     */
     axes?: Array<{
+        /**
+         * Human-readable axis name (e.g., 'Weight')
+         */
         name: string;
+        /**
+         * CSS property name (e.g., 'wght')
+         */
         property: string;
+        /**
+         * Default numeric value for the axis
+         */
         default: number;
+        /**
+         * Minimum inclusive bound
+         */
         min: number;
+        /**
+         * Maximum inclusive bound
+         */
         max: number;
     }>;
-    /** Usage tags (for Fontshare) */
+    /**
+     * Descriptive keywords for search indexing
+     */
     tags?: string[];
 }
 
@@ -138,29 +184,44 @@ export interface FontFeatures {
  * for consistent font handling across the application.
  */
 export interface UnifiedFont {
-    /** Unique identifier (Google: family name, Fontshare: slug) */
+    /**
+     * Unique ID (family name for Google, slug for Fontshare)
+     */
     id: string;
-    /** Font display name */
+    /**
+     * Canonical family name for CSS font-family
+     */
     name: string;
-    /** Font provider (google | fontshare) */
+    /**
+     * Upstream data source
+     */
     provider: FontProvider;
     /**
-     * Provider badge display name
-     *
-     * Human-readable provider name for UI display
-     * e.g., "Google Fonts" or "Fontshare"
+     * Display label for provider badges
      */
     providerBadge?: string;
-    /** Font category classification */
+    /**
+     * Primary typographic category
+     */
     category: FontCategory;
-    /** Supported character subsets */
+    /**
+     * All supported character sets
+     */
     subsets: FontSubset[];
-    /** Available font variants (weights, styles) */
+    /**
+     * List of available weights and styles
+     */
     variants: UnifiedFontVariant[];
-    /** URL mapping for font file downloads */
+    /**
+     * Remote assets for font loading
+     */
     styles: FontStyleUrls;
-    /** Additional metadata */
+    /**
+     * Technical metadata and rankings
+     */
     metadata: FontMetadata;
-    /** Advanced font features */
+    /**
+     * Variable font details and tags
+     */
     features: FontFeatures;
 }

src/entities/Font/model/types/index.ts

@@ -1,12 +1,3 @@
-/**
- * ============================================================================
- * SINGLE EXPORT POINT
- * ============================================================================
- *
- * This is the single export point for all Font types.
- * All imports should use: `import { X } from '$entities/Font/model/types'`
- */
-
 // Font domain and model types
 export type {
     FilterGroup,
@@ -33,3 +24,4 @@ export type {
 } from './store';
 
 export * from './store/appliedFonts';
+export * from './typography';

src/entities/Font/model/types/store.ts

@@ -1,9 +1,3 @@
-/**
- * ============================================================================
- * STORE TYPES
- * ============================================================================
- */
-
 import type {
     FontCategory,
     FontProvider,
@@ -12,37 +6,55 @@ import type {
 } from './font';
 
 /**
- * Font collection state
+ * Global state for the local font collection
  */
 export interface FontCollectionState {
-    /** All cached fonts */
+    /**
+     * Map of cached fonts indexed by their unique family ID
+     */
     fonts: Record<string, UnifiedFont>;
-    /** Active filters */
+    /**
+     * Set of active user-defined filters
+     */
     filters: FontCollectionFilters;
-    /** Sort configuration */
+    /**
+     * Current sorting parameters for the display list
+     */
     sort: FontCollectionSort;
 }
 
 /**
- * Font collection filters
+ * Filter configuration for narrow collections
  */
 export interface FontCollectionFilters {
-    /** Search query */
+    /**
+     * Partial family name to match against
+     */
     searchQuery: string;
-    /** Filter by providers */
+    /**
+     * Data sources (Google, Fontshare) to include
+     */
     providers?: FontProvider[];
-    /** Filter by categories */
+    /**
+     * Typographic categories (Serif, Sans, etc.) to include
+     */
     categories?: FontCategory[];
-    /** Filter by subsets */
+    /**
+     * Character sets (Latin, Cyrillic, etc.) to include
+     */
     subsets?: FontSubset[];
 }
 
 /**
- * Font collection sort configuration
+ * Ordering configuration for the font list
  */
 export interface FontCollectionSort {
-    /** Sort field */
+    /**
+     * The font property to order by
+     */
     field: 'name' | 'popularity' | 'category';
-    /** Sort direction */
+    /**
+     * The sort order (Ascending or Descending)
+     */
     direction: 'asc' | 'desc';
 }

src/entities/Font/model/types/typography.ts

@@ -0,0 +1 @@
+export type ControlId = 'font_size' | 'font_weight' | 'line_height' | 'letter_spacing';

src/entities/Font/ui/FontApplicator/FontApplicator.stories.svelte

@@ -0,0 +1,91 @@
+<script module>
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import FontApplicator from './FontApplicator.svelte';
+
+const { Story } = defineMeta({
+    title: 'Entities/FontApplicator',
+    component: FontApplicator,
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Loads a font and applies it to children. Shows blur/scale loading state until font is ready, then reveals with a smooth transition.',
+            },
+            story: { inline: false },
+        },
+        layout: 'centered',
+    },
+    argTypes: {
+        weight: { control: 'number' },
+    },
+});
+</script>
+
+<script lang="ts">
+import { mockUnifiedFont } from '$entities/Font/lib/mocks';
+import type { ComponentProps } from 'svelte';
+
+const fontUnknown = mockUnifiedFont({ id: 'nonexistent-font-xk92z', name: 'Nonexistent Font Xk92z' });
+
+const fontArial = mockUnifiedFont({ id: 'arial', name: 'Arial' });
+
+const fontArialBold = mockUnifiedFont({ id: 'arial-bold', name: 'Arial' });
+</script>
+
+<Story
+    name="Loading State"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'Font that has never been loaded by appliedFontsManager. The component renders in its pending state: blurred, scaled down, and semi-transparent.',
+            },
+        },
+    }}
+    args={{ font: fontUnknown, weight: 400 }}
+>
+    {#snippet template(args: ComponentProps<typeof FontApplicator>)}
+        <FontApplicator {...args}>
+            <p class="text-xl">The quick brown fox jumps over the lazy dog</p>
+        </FontApplicator>
+    {/snippet}
+</Story>
+
+<Story
+    name="Loaded State"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'Uses Arial, a system font available in all browsers. Because appliedFontsManager has not loaded it via FontFace, the manager status may remain pending — meaning the blur/scale state may still show. In a real app the manager would load the font and transition to the revealed state.',
+            },
+        },
+    }}
+    args={{ font: fontArial, weight: 400 }}
+>
+    {#snippet template(args: ComponentProps<typeof FontApplicator>)}
+        <FontApplicator {...args}>
+            <p class="text-xl">The quick brown fox jumps over the lazy dog</p>
+        </FontApplicator>
+    {/snippet}
+</Story>
+
+<Story
+    name="Custom Weight"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'Demonstrates passing a custom weight (700). The weight is forwarded to appliedFontsManager for font resolution; visually identical to the loaded state story until the manager confirms the font.',
+            },
+        },
+    }}
+    args={{ font: fontArialBold, weight: 700 }}
+>
+    {#snippet template(args: ComponentProps<typeof FontApplicator>)}
+        <FontApplicator {...args}>
+            <p class="text-xl">The quick brown fox jumps over the lazy dog</p>
+        </FontApplicator>
+    {/snippet}
+</Story>

src/entities/Font/ui/FontApplicator/FontApplicator.svelte

@@ -1,15 +1,13 @@
 <!--
     Component: FontApplicator
-    Loads fonts from fontshare with link tag
-    - Loads font only if it's not already applied
-    - Reacts to font load status to show/hide content
-    - Adds smooth transition when font appears
+    Applies a font to its children once the font file is loaded.
+    Shows the skeleton snippet while loading; falls back to system font if no skeleton is provided.
 -->
 <script lang="ts">
-import { cn } from '$shared/shadcn/utils/shadcn-utils';
+import clsx from 'clsx';
 import type { Snippet } from 'svelte';
-import { prefersReducedMotion } from 'svelte/motion';
 import {
+    DEFAULT_FONT_WEIGHT,
     type UnifiedFont,
     appliedFontsManager,
 } from '../../model';
@@ -32,13 +30,19 @@ interface Props {
      * Content snippet
      */
     children?: Snippet;
+    /**
+     * Shown while the font file is loading.
+     * When omitted, children render in system font until ready.
+     */
+    skeleton?: Snippet;
 }
 
 let {
     font,
-    weight = 400,
+    weight = DEFAULT_FONT_WEIGHT,
     className,
     children,
+    skeleton,
 }: Props = $props();
 
 const status = $derived(
@@ -49,30 +53,16 @@ const status = $derived(
     ),
 );
 
-// The "Show" condition: Font is loaded OR it errored out OR it's a noTouch preview (like in search)
 const shouldReveal = $derived(status === 'loaded' || status === 'error');
-
-const transitionClasses = $derived(
-    prefersReducedMotion.current
-        ? 'transition-none' // Disable CSS transitions if motion is reduced
-        : 'transition-all duration-300 ease-[cubic-bezier(0.22,1,0.36,1)]',
-);
 </script>
 
-<div
-    style:font-family={shouldReveal
-    ? `'${font.name}'`
-    : 'system-ui, -apple-system, sans-serif'}
-    class={cn(
-        transitionClasses,
-        // If reduced motion is on, we skip the transform/blur entirely
-        !shouldReveal
-            && !prefersReducedMotion.current
-            && 'opacity-50 scale-[0.95] blur-sm',
-        !shouldReveal && prefersReducedMotion.current && 'opacity-0', // Still hide until font is ready, but no movement
-        shouldReveal && 'opacity-100 scale-100 blur-0',
-        className,
-    )}
->
-    {@render children?.()}
-</div>
+{#if !shouldReveal && skeleton}
+    {@render skeleton()}
+{:else}
+    <div
+        style:font-family={shouldReveal ? `'${font.name}'` : 'system-ui, -apple-system, sans-serif'}
+        class={clsx(className)}
+    >
+        {@render children?.()}
+    </div>
+{/if}

src/entities/Font/ui/FontVirtualList/FontVirtualList.stories.svelte

@@ -0,0 +1,114 @@
+<script module>
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import FontVirtualList from './FontVirtualList.svelte';
+
+const { Story } = defineMeta({
+    title: 'Entities/FontVirtualList',
+    component: FontVirtualList,
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Virtualized font list backed by the `fontStore` singleton. Handles font loading registration (pin/touch) for visible items and triggers infinite scroll pagination via `fontStore.nextPage()`. Because the component reads directly from the `fontStore` singleton, stories render against a live (but empty/loading) store — no font data will appear unless the API is reachable from the Storybook host.',
+            },
+            story: { inline: false },
+        },
+        layout: 'padded',
+    },
+    argTypes: {
+        weight: { control: 'number', description: 'Font weight applied to visible fonts' },
+        itemHeight: { control: 'number', description: 'Height of each list item in pixels' },
+    },
+});
+</script>
+
+<script lang="ts">
+import type { ComponentProps } from 'svelte';
+</script>
+
+<Story
+    name="Loading Skeleton"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'Skeleton state shown while `fontStore.fonts` is empty and `fontStore.isLoading` is true. In a real session the skeleton fades out once the first page loads.',
+            },
+        },
+    }}
+    args={{ weight: 400, itemHeight: 72 }}
+>
+    {#snippet template(args: ComponentProps<typeof FontVirtualList>)}
+        <div class="h-[400px] w-full">
+            <FontVirtualList {...args}>
+                {#snippet skeleton()}
+                    <div class="flex flex-col gap-2 p-4">
+                        {#each Array(6) as _}
+                            <div class="h-16 animate-pulse rounded bg-neutral-200"></div>
+                        {/each}
+                    </div>
+                {/snippet}
+                {#snippet children({ item })}
+                    <div class="border-b border-neutral-100 p-3">{item.name}</div>
+                {/snippet}
+            </FontVirtualList>
+        </div>
+    {/snippet}
+</Story>
+
+<Story
+    name="Empty State"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'No `skeleton` snippet provided. When `fontStore.fonts` is empty the underlying VirtualList renders its empty state directly.',
+            },
+        },
+    }}
+    args={{ weight: 400, itemHeight: 72 }}
+>
+    {#snippet template(args: ComponentProps<typeof FontVirtualList>)}
+        <div class="h-[400px] w-full">
+            <FontVirtualList {...args}>
+                {#snippet children({ item })}
+                    <div class="border-b border-neutral-100 p-3">{item.name}</div>
+                {/snippet}
+            </FontVirtualList>
+        </div>
+    {/snippet}
+</Story>
+
+<Story
+    name="With Item Renderer"
+    parameters={{
+        docs: {
+            description: {
+                story:
+                    'Demonstrates how to configure a `children` snippet for item rendering. The list will be empty because `fontStore` is not populated in Storybook, but the template shows the expected slot shape: `{ item: UnifiedFont }`.',
+            },
+        },
+    }}
+    args={{ weight: 400, itemHeight: 80 }}
+>
+    {#snippet template(args: ComponentProps<typeof FontVirtualList>)}
+        <div class="h-[400px] w-full">
+            <FontVirtualList {...args}>
+                {#snippet skeleton()}
+                    <div class="flex flex-col gap-2 p-4">
+                        {#each Array(6) as _}
+                            <div class="h-16 animate-pulse rounded bg-neutral-200"></div>
+                        {/each}
+                    </div>
+                {/snippet}
+                {#snippet children({ item })}
+                    <div class="flex items-center justify-between border-b border-neutral-100 px-4 py-3">
+                        <span class="text-sm font-medium">{item.name}</span>
+                        <span class="text-xs text-neutral-400">{item.category}</span>
+                    </div>
+                {/snippet}
+            </FontVirtualList>
+        </div>
+    {/snippet}
+</Story>

src/entities/Font/ui/FontVirtualList/FontVirtualList.svelte

@@ -4,6 +4,7 @@
     - Handles font registration with the manager
 -->
 <script lang="ts">
+import { debounce } from '$shared/lib/utils';
 import {
     Skeleton,
     VirtualList,
@@ -18,8 +19,8 @@ import {
     type FontLoadRequestConfig,
     type UnifiedFont,
     appliedFontsManager,
+    fontStore,
 } from '../../model';
-import { fontStore } from '../../model/store';
 
 interface Props extends
     Omit<
@@ -53,30 +54,72 @@ const isLoading = $derived(
     fontStore.isFetching || fontStore.isLoading,
 );
 
-function handleInternalVisibleChange(visibleItems: UnifiedFont[]) {
-    const configs: FontLoadRequestConfig[] = [];
+let visibleFonts = $state<UnifiedFont[]>([]);
+let isCatchingUp = $state(false);
 
-    visibleItems.forEach(item => {
-        const url = getFontUrl(item, weight);
-
-        if (url) {
-            configs.push({
-                id: item.id,
-                name: item.name,
-                weight,
-                url,
-                isVariable: item.features?.isVariable,
-            });
-        }
-    });
-
-    // Auto-register fonts with the manager
-    appliedFontsManager.touch(configs);
+const showInitialSkeleton = $derived(!!skeleton && isLoading && fontStore.fonts.length === 0);
+const showCatchupSkeleton = $derived(!!skeleton && isCatchingUp);
 
+function handleInternalVisibleChange(items: UnifiedFont[]) {
+    visibleFonts = items;
     // Forward the call to any external listener
-    // onVisibleItemsChange?.(visibleItems);
+    onVisibleItemsChange?.(items);
 }
 
+/**
+ * Handle jump scroll — batch-load all missing pages then re-enable font loading.
+ * Suppresses appliedFontsManager.touch() during catch-up to avoid loading
+ * font files for thousands of intermediate fonts.
+ */
+async function handleJump(targetIndex: number) {
+    if (isCatchingUp || !fontStore.pagination.hasMore) {
+        return;
+    }
+    isCatchingUp = true;
+    try {
+        await fontStore.fetchAllPagesTo(targetIndex);
+    } finally {
+        isCatchingUp = false;
+    }
+}
+
+const debouncedTouch = debounce((configs: FontLoadRequestConfig[]) => {
+    appliedFontsManager.touch(configs);
+}, 150);
+
+// Re-touch whenever visible set or weight changes — fixes weight-change gap
+$effect(() => {
+    if (isCatchingUp) {
+        return;
+    }
+    const configs: FontLoadRequestConfig[] = visibleFonts.flatMap(item => {
+        const url = getFontUrl(item, weight);
+        if (!url) {
+            return [];
+        }
+        return [{ id: item.id, name: item.name, weight, url, isVariable: item.features?.isVariable }];
+    });
+    if (configs.length > 0) {
+        debouncedTouch(configs);
+    }
+});
+
+// Pin visible fonts so the eviction policy never removes on-screen entries.
+// Cleanup captures the snapshot values, so a weight change unpins the old
+// weight before pinning the new one.
+$effect(() => {
+    const w = weight;
+    const fonts = visibleFonts;
+    for (const f of fonts) {
+        appliedFontsManager.pin(f.id, w, f.features?.isVariable);
+    }
+    return () => {
+        for (const f of fonts) {
+            appliedFontsManager.unpin(f.id, w, f.features?.isVariable);
+        }
+    };
+});
+
 /**
  * Load more fonts by moving to the next page
  */
@@ -99,17 +142,19 @@ function loadMore() {
 function handleNearBottom(_lastVisibleIndex: number) {
     const { hasMore } = fontStore.pagination;
 
-    // VirtualList already checks if we're near the bottom of loaded items
-    if (hasMore && !fontStore.isFetching) {
+    // VirtualList already checks if we're near the bottom of loaded items.
+    // Guard isCatchingUp: fetchAllPagesTo bypasses TQ so isFetching stays false
+    // during batch catch-up, which would otherwise let nextPage() race with it.
+    if (hasMore && !fontStore.isFetching && !isCatchingUp) {
         loadMore();
     }
 }
 </script>
 
 <div class="relative w-full h-full">
-    {#if skeleton && isLoading && fontStore.fonts.length === 0}
+    {#if showInitialSkeleton && skeleton}
         <!-- Show skeleton only on initial load when no fonts are loaded yet -->
-        <div transition:fade={{ duration: 300 }}>
+        <div class="overflow-hidden h-full" transition:fade={{ duration: 300 }}>
             {@render skeleton()}
         </div>
     {:else}
@@ -117,14 +162,20 @@ function handleNearBottom(_lastVisibleIndex: number) {
         <VirtualList
             items={fontStore.fonts}
             total={fontStore.pagination.total}
-            isLoading={isLoading}
+            isLoading={isLoading || isCatchingUp}
             onVisibleItemsChange={handleInternalVisibleChange}
             onNearBottom={handleNearBottom}
+            onJump={handleJump}
             {...rest}
         >
             {#snippet children(scope)}
                 {@render children(scope)}
             {/snippet}
         </VirtualList>
+        {#if showCatchupSkeleton && skeleton}
+            <div class="absolute inset-0 overflow-hidden" transition:fade={{ duration: 150 }}>
+                {@render skeleton()}
+            </div>
+        {/if}
     {/if}
 </div>

src/features/ChangeAppTheme/model/store/ThemeManager/ThemeManager.svelte.ts

@@ -41,15 +41,25 @@ type ThemeSource = 'system' | 'user';
  */
 class ThemeManager {
     // Private reactive state
-    /** Current theme value ('light' or 'dark') */
+    /**
+     * Current theme value ('light' or 'dark')
+     */
     #theme = $state<Theme>('light');
-    /** Whether theme is controlled by user or follows system */
+    /**
+     * Whether theme is controlled by user or follows system
+     */
     #source = $state<ThemeSource>('system');
-    /** MediaQueryList for detecting system theme changes */
+    /**
+     * MediaQueryList for detecting system theme changes
+     */
     #mediaQuery: MediaQueryList | null = null;
-    /** Persistent storage for user's theme preference */
+    /**
+     * Persistent storage for user's theme preference
+     */
     #store = createPersistentStore<Theme | null>('glyphdiff:theme', null);
-    /** Bound handler for system theme change events */
+    /**
+     * Bound handler for system theme change events
+     */
     #systemChangeHandler = this.#onSystemChange.bind(this);
 
     constructor() {
@@ -64,22 +74,30 @@ class ThemeManager {
         }
     }
 
-    /** Current theme value */
+    /**
+     * Current theme value
+     */
     get value(): Theme {
         return this.#theme;
     }
 
-    /** Source of current theme ('system' or 'user') */
+    /**
+     * Source of current theme ('system' or 'user')
+     */
     get source(): ThemeSource {
         return this.#source;
     }
 
-    /** Whether dark theme is active */
+    /**
+     * Whether dark theme is active
+     */
     get isDark(): boolean {
         return this.#theme === 'dark';
     }
 
-    /** Whether theme is controlled by user (not following system) */
+    /**
+     * Whether theme is controlled by user (not following system)
+     */
     get isUserControlled(): boolean {
         return this.#source === 'user';
     }

src/features/ChangeAppTheme/model/store/ThemeManager/ThemeManager.test.ts

@@ -1,9 +1,9 @@
-/** @vitest-environment jsdom */
+/**
+ * @vitest-environment jsdom
+ */
 
-// ============================================================
 // Mock MediaQueryListEvent for system theme change simulations
 // Note: Other mocks (ResizeObserver, localStorage, matchMedia) are set up in vitest.setup.unit.ts
-// ============================================================
 
 class MockMediaQueryListEvent extends Event {
     matches: boolean;
@@ -16,9 +16,7 @@ class MockMediaQueryListEvent extends Event {
     }
 }
 
-// ============================================================
 // NOW IT'S SAFE TO IMPORT
-// ============================================================
 
 import {
     afterEach,

src/features/ChangeAppTheme/ui/ThemeSwitch/ThemeSwitch.svelte.test.ts

@@ -0,0 +1,56 @@
+import {
+    fireEvent,
+    render,
+    screen,
+} from '@testing-library/svelte';
+import { themeManager } from '../../model';
+import ThemeSwitch from './ThemeSwitch.svelte';
+
+const context = new Map([['responsive', { isMobile: false }]]);
+
+describe('ThemeSwitch', () => {
+    beforeEach(() => {
+        themeManager.setTheme('light');
+    });
+
+    describe('Rendering', () => {
+        it('renders an icon button', () => {
+            render(ThemeSwitch, { context });
+            expect(screen.getByRole('button')).toBeInTheDocument();
+        });
+
+        it('has "Toggle theme" title', () => {
+            render(ThemeSwitch, { context });
+            expect(screen.getByTitle('Toggle theme')).toBeInTheDocument();
+        });
+
+        it('renders an SVG icon', () => {
+            const { container } = render(ThemeSwitch, { context });
+            expect(container.querySelector('svg')).toBeInTheDocument();
+        });
+    });
+
+    describe('Interaction', () => {
+        it('toggles theme from light to dark on click', async () => {
+            render(ThemeSwitch, { context });
+            expect(themeManager.value).toBe('light');
+            await fireEvent.click(screen.getByRole('button'));
+            expect(themeManager.value).toBe('dark');
+        });
+
+        it('toggles theme from dark to light on click', async () => {
+            themeManager.setTheme('dark');
+            render(ThemeSwitch, { context });
+            await fireEvent.click(screen.getByRole('button'));
+            expect(themeManager.value).toBe('light');
+        });
+
+        it('double click returns to original theme', async () => {
+            render(ThemeSwitch, { context });
+            const btn = screen.getByRole('button');
+            await fireEvent.click(btn);
+            await fireEvent.click(btn);
+            expect(themeManager.value).toBe('light');
+        });
+    });
+});

src/features/DisplayFont/ui/FontSampler/FontSampler.stories.svelte

@@ -35,7 +35,7 @@ const { Story } = defineMeta({
 
 <script lang="ts">
 import type { UnifiedFont } from '$entities/Font';
-import { controlManager } from '$features/SetupFont';
+import type { ComponentProps } from 'svelte';
 
 // Mock fonts for testing
 const mockArial: UnifiedFont = {
@@ -89,7 +89,7 @@ const mockGeorgia: UnifiedFont = {
         index: 0,
     }}
 >
-    {#snippet template(args)}
+    {#snippet template(args: ComponentProps<typeof FontSampler>)}
         <Providers>
             <div class="max-w-2xl mx-auto">
                 <FontSampler {...args} />
@@ -106,7 +106,7 @@ const mockGeorgia: UnifiedFont = {
         index: 1,
     }}
 >
-    {#snippet template(args)}
+    {#snippet template(args: ComponentProps<typeof FontSampler>)}
         <Providers>
             <div class="max-w-2xl mx-auto">
                 <FontSampler {...args} />

src/features/DisplayFont/ui/FontSampler/FontSampler.svelte

@@ -8,14 +8,13 @@ import {
     FontApplicator,
     type UnifiedFont,
 } from '$entities/Font';
-import { controlManager } from '$features/SetupFont';
+import { typographySettingsStore } from '$features/SetupFont/model';
 import {
     Badge,
     ContentEditable,
     Divider,
     Footnote,
     Stat,
-    StatGroup,
 } from '$shared/ui';
 import { fly } from 'svelte/transition';
 
@@ -37,11 +36,6 @@ interface Props {
 
 let { font, text = $bindable(), index = 0 }: Props = $props();
 
-const fontWeight = $derived(controlManager.weight);
-const fontSize = $derived(controlManager.renderedSize);
-const lineHeight = $derived(controlManager.height);
-const letterSpacing = $derived(controlManager.spacing);
-
 // Adjust the property name to match your UnifiedFont type
 const fontType = $derived((font as any).type ?? (font as any).category ?? '');
 
@@ -52,10 +46,10 @@ const providerBadge = $derived(
 );
 
 const stats = $derived([
-    { label: 'SZ', value: `${fontSize}PX` },
-    { label: 'WGT', value: `${fontWeight}` },
-    { label: 'LH', value: lineHeight?.toFixed(2) },
-    { label: 'LTR', value: `${letterSpacing}` },
+    { label: 'SZ', value: `${typographySettingsStore.renderedSize}PX` },
+    { label: 'WGT', value: `${typographySettingsStore.weight}` },
+    { label: 'LH', value: typographySettingsStore.height?.toFixed(2) },
+    { label: 'LTR', value: `${typographySettingsStore.spacing}` },
 ]);
 </script>
 
@@ -65,7 +59,7 @@ const stats = $derived([
         group relative
         w-full h-full
         bg-paper dark:bg-dark-card
-        border border-black/5 dark:border-white/10
+        border border-subtle
         hover:border-brand dark:hover:border-brand
         hover:shadow-brand/10
         hover:shadow-[5px_5px_0px_0px]
@@ -75,20 +69,20 @@ const stats = $derived([
         min-h-60
         rounded-none
     "
-    style:font-weight={fontWeight}
+    style:font-weight={typographySettingsStore.weight}
 >
     <!-- ── Header bar ─────────────────────────────────────────────────── -->
     <div
         class="
             flex items-center justify-between
             px-4 sm:px-5 md:px-6 py-3 sm:py-4
-            border-b border-black/5 dark:border-white/10
+            border-b border-subtle
             bg-paper dark:bg-dark-card
         "
     >
         <!-- Left: index · name · type badge · provider badge -->
         <div class="flex items-center gap-2 sm:gap-4 min-w-0 shrink-0">
-            <span class="font-mono text-[0.625rem] tracking-widest text-neutral-400 uppercase leading-none shrink-0">
+            <span class="font-mono text-2xs tracking-widest text-neutral-400 uppercase leading-none shrink-0">
                 {String(index + 1).padStart(2, '0')}
             </span>
             <Divider orientation="vertical" class="h-3 shrink-0" />
@@ -100,14 +94,14 @@ const stats = $derived([
             </span>
 
             {#if fontType}
-                <Badge size="xs" variant="default" class="text-nowrap font-mono">
+                <Badge size="xs" variant="default" nowrap>
                     {fontType}
                 </Badge>
             {/if}
 
             <!-- Provider badge -->
             {#if providerBadge}
-                <Badge size="xs" variant="default" class="text-nowrap font-mono" data-provider={font.provider}>
+                <Badge size="xs" variant="default" nowrap data-provider={font.provider}>
                     {providerBadge}
                 </Badge>
             {/if}
@@ -140,20 +134,20 @@ const stats = $derived([
 
     <!-- ── Main content area ──────────────────────────────────────────── -->
     <div class="flex-1 p-4 sm:p-5 md:p-8 flex items-center overflow-hidden bg-paper dark:bg-dark-card relative z-10">
-        <FontApplicator {font} weight={fontWeight}>
+        <FontApplicator {font} weight={typographySettingsStore.weight}>
             <ContentEditable
                 bind:text
-                {fontSize}
-                {lineHeight}
-                {letterSpacing}
+                fontSize={typographySettingsStore.renderedSize}
+                lineHeight={typographySettingsStore.height}
+                letterSpacing={typographySettingsStore.spacing}
             />
         </FontApplicator>
     </div>
 
     <!-- ── Mobile stats footer (md:hidden — header stats take over above) -->
-    <div class="md:hidden px-4 sm:px-5 py-1.5 sm:py-2 border-t border-black/5 dark:border-white/10 flex gap-2 sm:gap-4 bg-paper dark:bg-dark-card mt-auto">
+    <div class="md:hidden px-4 sm:px-5 py-1.5 sm:py-2 border-t border-subtle flex gap-2 sm:gap-4 bg-paper dark:bg-dark-card mt-auto">
         {#each stats as stat, i}
-            <Footnote class="text-[0.4375rem] sm:text-[0.5rem] tracking-wider {i === 0 ? 'ml-auto' : ''}">
+            <Footnote class="text-5xs sm:text-4xs tracking-wider {i === 0 ? 'ml-auto' : ''}">
                 {stat.label}:{stat.value}
             </Footnote>
             {#if i < stats.length - 1}

src/features/GetFonts/api/filters/filters.ts

@@ -15,19 +15,29 @@ const PROXY_API_URL = 'https://api.glyphdiff.com/api/v1/filters' as const;
  * Filter metadata type from backend
  */
 export interface FilterMetadata {
-    /** Filter ID (e.g., "providers", "categories", "subsets") */
+    /**
+     * Filter ID (e.g., "providers", "categories", "subsets")
+     */
     id: string;
 
-    /** Display name (e.g., "Font Providers", "Categories", "Character Subsets") */
+    /**
+     * Display name (e.g., "Font Providers", "Categories", "Character Subsets")
+     */
     name: string;
 
-    /** Filter description */
+    /**
+     * Filter description
+     */
     description: string;
 
-    /** Filter type */
+    /**
+     * Filter type
+     */
     type: 'enum' | 'string' | 'array';
 
-    /** Available filter options */
+    /**
+     * Available filter options
+     */
     options: FilterOption[];
 }
 
@@ -35,16 +45,24 @@ export interface FilterMetadata {
  * Filter option type
  */
 export interface FilterOption {
-    /** Option ID (e.g., "google", "serif", "latin") */
+    /**
+     * Option ID (e.g., "google", "serif", "latin")
+     */
     id: string;
 
-    /** Display name (e.g., "Google Fonts", "Serif", "Latin") */
+    /**
+     * Display name (e.g., "Google Fonts", "Serif", "Latin")
+     */
     name: string;
 
-    /** Option value (e.g., "google", "serif", "latin") */
+    /**
+     * Option value (e.g., "google", "serif", "latin")
+     */
     value: string;
 
-    /** Number of fonts with this value */
+    /**
+     * Number of fonts with this value
+     */
     count: number;
 }
 
@@ -52,7 +70,9 @@ export interface FilterOption {
  * Proxy filters API response
  */
 export interface ProxyFiltersResponse {
-    /** Array of filter metadata */
+    /**
+     * Array of filter metadata
+     */
     filters: FilterMetadata[];
 }
 

src/features/GetFonts/index.ts

@@ -4,6 +4,7 @@ export {
     mapManagerToParams,
 } from './lib';
 
+export { filtersStore } from './model/state/filters.svelte';
 export { filterManager } from './model/state/manager.svelte';
 
 export {

src/features/GetFonts/model/index.ts

@@ -1,15 +1,56 @@
 export type {
+    /**
+     * Top-level configuration for all filters
+     */
     FilterConfig,
+    /**
+     * Configuration for a single grouping of filter properties
+     */
     FilterGroupConfig,
 } from './types/filter';
 
-export { filtersStore } from './state/filters.svelte';
-export { filterManager } from './state/manager.svelte';
-
+/**
+ * Global reactive filter state
+ */
 export {
+    /**
+     * Low-level property selection store
+     */
+    filtersStore,
+} from './state/filters.svelte';
+
+/**
+ * Main filter controller
+ */
+export {
+    /**
+     * High-level manager for syncing search and filters
+     */
+    filterManager,
+} from './state/manager.svelte';
+
+/**
+ * Sorting logic
+ */
+export {
+    /**
+     * Map of human-readable labels to API sort keys
+     */
     SORT_MAP,
+    /**
+     * List of all available sort options for the UI
+     */
     SORT_OPTIONS,
+    /**
+     * Valid sort key values
+     */
     type SortApiValue,
+    /**
+     * UI model for a single sort option
+     */
     type SortOption,
+    /**
+     * Reactive store for the current sort selection
+     */
     sortStore,
 } from './store/sortStore.svelte';

src/features/GetFonts/model/state/filters.svelte.ts

@@ -32,13 +32,19 @@ import {
  * Provides reactive access to filter data
  */
 class FiltersStore {
-    /** TanStack Query result state */
+    /**
+     * TanStack Query result state
+     */
     protected result = $state<QueryObserverResult<FilterMetadata[], Error>>({} as any);
 
-    /** TanStack Query observer instance */
+    /**
+     * TanStack Query observer instance
+     */
     protected observer: QueryObserver<FilterMetadata[], Error>;
 
-    /** Shared query client */
+    /**
+     * Shared query client
+     */
     protected qc = queryClient;
 
     /**

src/features/GetFonts/model/store/sortStore.svelte.ts

@@ -21,17 +21,23 @@ function createSortStore(initial: SortOption = 'Popularity') {
     let current = $state<SortOption>(initial);
 
     return {
-        /** Current display label (e.g. 'Popularity') */
+        /**
+         * Current display label (e.g. 'Popularity')
+         */
         get value() {
             return current;
         },
 
-        /** Mapped API value (e.g. 'popularity') */
+        /**
+         * Mapped API value (e.g. 'popularity')
+         */
         get apiValue(): SortApiValue {
             return SORT_MAP[current];
         },
 
-        /** Set the active sort option by its display label */
+        /**
+         * Set the active sort option by its display label
+         */
         set(option: SortOption) {
             current = option;
         },

src/features/GetFonts/model/types/filter.ts

@@ -1,12 +1,27 @@
 import type { Property } from '$shared/lib';
 
 export interface FilterGroupConfig<TValue extends string> {
+    /**
+     * Unique identifier for the filter group (e.g. 'categories')
+     */
     id: string;
+    /**
+     * Human-readable label displayed in the UI header
+     */
     label: string;
+    /**
+     * List of toggleable properties within this group
+     */
     properties: Property<TValue>[];
 }
 
 export interface FilterConfig<TValue extends string> {
+    /**
+     * Optional string to filter results by name
+     */
     queryValue?: string;
+    /**
+     * Collection of filter groups to display
+     */
     groups: FilterGroupConfig<TValue>[];
 }

src/features/GetFonts/ui/Filters/Filters.stories.svelte

@@ -0,0 +1,26 @@
+<script module>
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import Filters from './Filters.svelte';
+
+const { Story } = defineMeta({
+    title: 'Features/Filters',
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Renders the full list of filter groups managed by filterManager. Each group maps to a collapsible FilterGroup with checkboxes. No props — reads directly from the filterManager singleton.',
+            },
+            story: { inline: false },
+        },
+        layout: 'padded',
+    },
+    argTypes: {},
+});
+</script>
+
+<Story name="Default">
+    {#snippet template()}
+        <Filters />
+    {/snippet}
+</Story>

src/features/GetFonts/ui/Filters/Filters.svelte.test.ts

@@ -0,0 +1,74 @@
+import {
+    filterManager,
+    filtersStore,
+} from '$features/GetFonts';
+import {
+    render,
+    screen,
+} from '@testing-library/svelte';
+import { vi } from 'vitest';
+import Filters from './Filters.svelte';
+
+describe('Filters', () => {
+    beforeEach(() => {
+        // Clear groups and mock filtersStore to be empty so the auto-sync effect doesn't overwrite us
+        filterManager.setGroups([]);
+        vi.spyOn(filtersStore, 'filters', 'get').mockReturnValue([]);
+    });
+
+    afterEach(() => {
+        vi.restoreAllMocks();
+    });
+
+    describe('Rendering', () => {
+        it('renders nothing when filter groups are empty', () => {
+            const { container } = render(Filters);
+            // It might render an empty container if the component has one, but we expect no children
+            expect(container.firstChild?.childNodes.length ?? 0).toBe(0);
+        });
+
+        it('renders a label for each filter group', () => {
+            filterManager.setGroups([
+                { id: 'cat', label: 'Categories', properties: [] },
+                { id: 'prov', label: 'Font Providers', properties: [] },
+            ]);
+            render(Filters);
+            expect(screen.getByText('Categories')).toBeInTheDocument();
+            expect(screen.getByText('Font Providers')).toBeInTheDocument();
+        });
+
+        it('renders filter properties within groups', () => {
+            filterManager.setGroups([
+                {
+                    id: 'cat',
+                    label: 'Category',
+                    properties: [
+                        { id: 'serif', name: 'Serif', value: 'serif', selected: false },
+                        { id: 'sans', name: 'Sans-Serif', value: 'sans-serif', selected: false },
+                    ],
+                },
+            ]);
+            render(Filters);
+            expect(screen.getByText('Serif')).toBeInTheDocument();
+            expect(screen.getByText('Sans-Serif')).toBeInTheDocument();
+        });
+
+        it('renders multiple groups with their properties', () => {
+            filterManager.setGroups([
+                {
+                    id: 'cat',
+                    label: 'Category',
+                    properties: [{ id: 'mono', name: 'Monospace', value: 'monospace', selected: false }],
+                },
+                {
+                    id: 'prov',
+                    label: 'Provider',
+                    properties: [{ id: 'google', name: 'Google', value: 'google', selected: false }],
+                },
+            ]);
+            render(Filters);
+            expect(screen.getByText('Monospace')).toBeInTheDocument();
+            expect(screen.getByText('Google')).toBeInTheDocument();
+        });
+    });
+});

src/features/GetFonts/ui/FiltersControl/FilterControls.stories.svelte

@@ -0,0 +1,39 @@
+<script module>
+import Providers from '$shared/lib/storybook/Providers.svelte';
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import FilterControls from './FilterControls.svelte';
+
+const { Story } = defineMeta({
+    title: 'Features/FilterControls',
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Sort options and Reset_Filters button rendered below the filter list. Reads sort state from sortStore and dispatches resets via filterManager. Requires responsive context — wrap with Providers.',
+            },
+            story: { inline: false },
+        },
+        layout: 'padded',
+    },
+    argTypes: {},
+});
+</script>
+
+<Story name="Default">
+    {#snippet template()}
+        <Providers>
+            <FilterControls />
+        </Providers>
+    {/snippet}
+</Story>
+
+<Story name="Mobile layout">
+    {#snippet template()}
+        <Providers>
+            <div style="width: 375px;">
+                <FilterControls />
+            </div>
+        </Providers>
+    {/snippet}
+</Story>

src/features/GetFonts/ui/FiltersControl/FilterControls.svelte

@@ -6,10 +6,10 @@
 <script lang="ts">
 import { fontStore } from '$entities/Font';
 import type { ResponsiveManager } from '$shared/lib';
-import { cn } from '$shared/shadcn/utils/shadcn-utils';
 import { Button } from '$shared/ui';
 import { Label } from '$shared/ui';
 import RefreshCwIcon from '@lucide/svelte/icons/refresh-cw';
+import clsx from 'clsx';
 import {
     getContext,
     untrack,
@@ -45,7 +45,7 @@ function handleReset() {
 </script>
 
 <div
-    class={cn(
+    class={clsx(
         'flex flex-col md:flex-row justify-between items-start md:items-center',
         'gap-1 md:gap-6',
         'pt-6 mt-6 md:pt-8 md:mt-8',
@@ -61,13 +61,10 @@ function handleReset() {
             {#each SORT_OPTIONS as option}
                 <Button
                     variant="ghost"
-                    size={isMobileOrTabletPortrait ? 'sm' : 'md'}
+                    size={isMobileOrTabletPortrait ? 'xs' : 'sm'}
                     active={sortStore.value === option}
                     onclick={() => sortStore.set(option)}
-                    class={cn(
-                        'font-bold uppercase tracking-wide font-primary, px-0',
-                        isMobileOrTabletPortrait ? 'text-[0.5625rem]' : 'text-[0.625rem]',
-                    )}
+                    class="tracking-wide px-0"
                 >
                     {option}
                 </Button>
@@ -78,12 +75,9 @@ function handleReset() {
     <!-- Reset_Filters -->
     <Button
         variant="ghost"
-        size={isMobileOrTabletPortrait ? 'sm' : 'md'}
+        size={isMobileOrTabletPortrait ? 'xs' : 'sm'}
         onclick={handleReset}
-        class={cn(
-            'group text-[0.5625rem] md:text-[0.625rem] font-mono font-bold uppercase tracking-widest text-neutral-400',
-            isMobileOrTabletPortrait && 'px-0',
-        )}
+        class={clsx('group font-mono tracking-widest text-neutral-400', isMobileOrTabletPortrait && 'px-0')}
         iconPosition="left"
     >
         {#snippet icon()}

src/features/SetupFont/index.ts

@@ -1,28 +1,6 @@
-export { TypographyMenu } from './ui';
-
 export {
-    type ControlId,
-    controlManager,
-    DEFAULT_FONT_SIZE,
-    DEFAULT_FONT_WEIGHT,
-    DEFAULT_LETTER_SPACING,
-    DEFAULT_LINE_HEIGHT,
-    DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
-    FONT_SIZE_STEP,
-    FONT_WEIGHT_STEP,
-    LINE_HEIGHT_STEP,
-    MAX_FONT_SIZE,
-    MAX_FONT_WEIGHT,
-    MAX_LINE_HEIGHT,
-    MIN_FONT_SIZE,
-    MIN_FONT_WEIGHT,
-    MIN_LINE_HEIGHT,
-    MULTIPLIER_L,
-    MULTIPLIER_M,
-    MULTIPLIER_S,
-} from './model';
-
-export {
-    createTypographyControlManager,
-    type TypographyControlManager,
+    createTypographySettingsManager,
+    type TypographySettingsManager,
 } from './lib';
+export { typographySettingsStore } from './model';
+export { TypographyMenu } from './ui';

src/features/SetupFont/lib/index.ts

@@ -1,4 +1,4 @@
 export {
-    createTypographyControlManager,
-    type TypographyControlManager,
-} from './controlManager/controlManager.svelte';
+    createTypographySettingsManager,
+    type TypographySettingsManager,
+} from './settingsManager/settingsManager.svelte';

src/features/SetupFont/lib/settingsManager/settingsManager.svelte.ts

@@ -10,6 +10,13 @@
  * when displaying/editing, but the base size is what's stored.
  */
 
+import {
+    type ControlId,
+    DEFAULT_FONT_SIZE,
+    DEFAULT_FONT_WEIGHT,
+    DEFAULT_LETTER_SPACING,
+    DEFAULT_LINE_HEIGHT,
+} from '$entities/Font';
 import {
     type ControlDataModel,
     type ControlModel,
@@ -19,20 +26,16 @@ import {
     createTypographyControl,
 } from '$shared/lib';
 import { SvelteMap } from 'svelte/reactivity';
-import {
-    type ControlId,
-    DEFAULT_FONT_SIZE,
-    DEFAULT_FONT_WEIGHT,
-    DEFAULT_LETTER_SPACING,
-    DEFAULT_LINE_HEIGHT,
-} from '../../model';
 
 type ControlOnlyFields<T extends string = string> = Omit<ControlModel<T>, keyof ControlDataModel>;
 
 /**
- * A control with its instance
+ * A control with its associated instance
  */
 export interface Control extends ControlOnlyFields<ControlId> {
+    /**
+     * The reactive typography control instance
+     */
     instance: TypographyControl;
 }
 
@@ -40,9 +43,21 @@ export interface Control extends ControlOnlyFields<ControlId> {
  * Storage schema for typography settings
  */
 export interface TypographySettings {
+    /**
+     * Base font size (User preference, unscaled)
+     */
     fontSize: number;
+    /**
+     * Numeric font weight (100-900)
+     */
     fontWeight: number;
+    /**
+     * Line height multiplier (e.g. 1.5)
+     */
     lineHeight: number;
+    /**
+     * Letter spacing in em/px
+     */
     letterSpacing: number;
 }
 
@@ -52,14 +67,22 @@ export interface TypographySettings {
  * Manages multiple typography controls with persistent storage and
  * responsive scaling support for font size.
  */
-export class TypographyControlManager {
-    /** Map of controls keyed by ID */
+export class TypographySettingsManager {
+    /**
+     * Internal map of reactive controls keyed by their identifier
+     */
     #controls = new SvelteMap<string, Control>();
-    /** Responsive multiplier for font size display */
+    /**
+     * Global multiplier for responsive font size scaling
+     */
     #multiplier = $state(1);
-    /** Persistent storage for settings */
+    /**
+     * LocalStorage-backed storage for persistence
+     */
     #storage: PersistentStore<TypographySettings>;
-    /** Base font size (user preference, unscaled) */
+    /**
+     * The underlying font size before responsive scaling is applied
+     */
     #baseSize = $state(DEFAULT_FONT_SIZE);
 
     constructor(configs: ControlModel<ControlId>[], storage: PersistentStore<TypographySettings>) {
@@ -105,7 +128,9 @@ export class TypographyControlManager {
             // This handles the "Multiplier" logic specifically for the Font Size Control
             $effect(() => {
                 const ctrl = this.#controls.get('font_size')?.instance;
-                if (!ctrl) return;
+                if (!ctrl) {
+                    return;
+                }
 
                 // If the user moves the slider/clicks buttons in the UI:
                 // We update the baseSize (User Intent)
@@ -124,26 +149,35 @@ export class TypographyControlManager {
      * Gets initial value for a control from storage or defaults
      */
     #getInitialValue(id: string, saved: TypographySettings): number {
-        if (id === 'font_size') return saved.fontSize * this.#multiplier;
-        if (id === 'font_weight') return saved.fontWeight;
-        if (id === 'line_height') return saved.lineHeight;
-        if (id === 'letter_spacing') return saved.letterSpacing;
+        if (id === 'font_size') {
+            return saved.fontSize * this.#multiplier;
+        }
+        if (id === 'font_weight') {
+            return saved.fontWeight;
+        }
+        if (id === 'line_height') {
+            return saved.lineHeight;
+        }
+        if (id === 'letter_spacing') {
+            return saved.letterSpacing;
+        }
         return 0;
     }
 
-    /** Current multiplier for responsive scaling */
+    /**
+     * Active scaling factor for the rendered font size
+     */
     get multiplier() {
         return this.#multiplier;
     }
 
     /**
-     * Set the multiplier and update font size display
-     *
-     * When multiplier changes, the font size control's display value
-     * is updated to reflect the new scale while preserving base size.
+     * Updates the multiplier and recalculates dependent control values
      */
     set multiplier(value: number) {
-        if (this.#multiplier === value) return;
+        if (this.#multiplier === value) {
+            return;
+        }
         this.#multiplier = value;
 
         // When multiplier changes, we must update the Font Size Control's display value
@@ -154,14 +188,15 @@ export class TypographyControlManager {
     }
 
     /**
-     * The scaled size for CSS usage
-     * Returns baseSize * multiplier for actual rendering
+     * The actual pixel value for CSS font-size (baseSize * multiplier)
      */
     get renderedSize() {
         return this.#baseSize * this.#multiplier;
     }
 
-    /** The base size (User Preference) */
+    /**
+     * The raw font size preference before scaling
+     */
     get baseSize() {
         return this.#baseSize;
     }
@@ -169,49 +204,69 @@ export class TypographyControlManager {
     set baseSize(val: number) {
         this.#baseSize = val;
         const ctrl = this.#controls.get('font_size')?.instance;
-        if (ctrl) ctrl.value = val * this.#multiplier;
+        if (ctrl) {
+            ctrl.value = val * this.#multiplier;
+        }
     }
 
     /**
-     * Getters for controls
+     * List of all managed typography controls
      */
     get controls() {
         return Array.from(this.#controls.values());
     }
 
+    /**
+     * Reactive instance for weight manipulation
+     */
     get weightControl() {
         return this.#controls.get('font_weight')?.instance;
     }
 
+    /**
+     * Reactive instance for size manipulation
+     */
     get sizeControl() {
         return this.#controls.get('font_size')?.instance;
     }
 
+    /**
+     * Reactive instance for line-height manipulation
+     */
     get heightControl() {
         return this.#controls.get('line_height')?.instance;
     }
 
+    /**
+     * Reactive instance for letter-spacing manipulation
+     */
     get spacingControl() {
         return this.#controls.get('letter_spacing')?.instance;
     }
 
     /**
-     * Getters for values (besides font-size)
+     * Current numeric font weight (reactive)
      */
     get weight() {
         return this.#controls.get('font_weight')?.instance.value ?? DEFAULT_FONT_WEIGHT;
     }
 
+    /**
+     * Current numeric line height (reactive)
+     */
     get height() {
         return this.#controls.get('line_height')?.instance.value ?? DEFAULT_LINE_HEIGHT;
     }
 
+    /**
+     * Current numeric letter spacing (reactive)
+     */
     get spacing() {
         return this.#controls.get('letter_spacing')?.instance.value ?? DEFAULT_LETTER_SPACING;
     }
 
     /**
-     * Reset all controls to default values
+     * Reset all controls to project-defined defaults
      */
     reset() {
         this.#storage.clear();
@@ -227,9 +282,15 @@ export class TypographyControlManager {
                 // Map storage key to control id
                 const key = c.id.replace('_', '') as keyof TypographySettings;
                 // Simplified for brevity, you'd map these properly:
-                if (c.id === 'font_weight') c.instance.value = defaults.fontWeight;
-                if (c.id === 'line_height') c.instance.value = defaults.lineHeight;
-                if (c.id === 'letter_spacing') c.instance.value = defaults.letterSpacing;
+                if (c.id === 'font_weight') {
+                    c.instance.value = defaults.fontWeight;
+                }
+                if (c.id === 'line_height') {
+                    c.instance.value = defaults.lineHeight;
+                }
+                if (c.id === 'letter_spacing') {
+                    c.instance.value = defaults.letterSpacing;
+                }
             }
         });
     }
@@ -242,7 +303,7 @@ export class TypographyControlManager {
  * @param storageId - Persistent storage identifier
  * @returns Typography control manager instance
  */
-export function createTypographyControlManager(
+export function createTypographySettingsManager(
     configs: ControlModel<ControlId>[],
     storageId: string = 'glyphdiff:typography',
 ) {
@@ -252,5 +313,5 @@ export function createTypographyControlManager(
         lineHeight: DEFAULT_LINE_HEIGHT,
         letterSpacing: DEFAULT_LETTER_SPACING,
     });
-    return new TypographyControlManager(configs, storage);
+    return new TypographySettingsManager(configs, storage);
 }

src/features/SetupFont/lib/settingsManager/settingsManager.test.ts

@@ -1,6 +1,14 @@
-/** @vitest-environment jsdom */
+/**
+ * @vitest-environment jsdom
+ */
+import {
+    DEFAULT_FONT_SIZE,
+    DEFAULT_FONT_WEIGHT,
+    DEFAULT_LETTER_SPACING,
+    DEFAULT_LINE_HEIGHT,
+    DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
+} from '$entities/Font';
 import {
-    afterEach,
     beforeEach,
     describe,
     expect,
@@ -8,21 +16,14 @@ import {
     vi,
 } from 'vitest';
 import {
-    DEFAULT_FONT_SIZE,
-    DEFAULT_FONT_WEIGHT,
-    DEFAULT_LETTER_SPACING,
-    DEFAULT_LINE_HEIGHT,
-    DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
-} from '../../model';
-import {
-    TypographyControlManager,
     type TypographySettings,
-} from './controlManager.svelte';
+    TypographySettingsManager,
+} from './settingsManager.svelte';
 
 /**
- * Test Strategy for TypographyControlManager
+ * Test Strategy for TypographySettingsManager
  *
- * This test suite validates the TypographyControlManager state management logic.
+ * This test suite validates the TypographySettingsManager state management logic.
  * These are unit tests for the manager logic, separate from component rendering.
  *
  * NOTE: Svelte 5's $effect runs in microtasks, so we need to flush effects
@@ -45,7 +46,7 @@ async function flushEffects() {
     await Promise.resolve();
 }
 
-describe('TypographyControlManager - Unit Tests', () => {
+describe('TypographySettingsManager - Unit Tests', () => {
     let mockStorage: TypographySettings;
     let mockPersistentStore: {
         value: TypographySettings;
@@ -85,7 +86,7 @@ describe('TypographyControlManager - Unit Tests', () => {
 
     describe('Initialization', () => {
         it('creates manager with default values from storage', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -105,7 +106,7 @@ describe('TypographyControlManager - Unit Tests', () => {
             };
             mockPersistentStore = createMockPersistentStore(mockStorage);
 
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -117,7 +118,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('initializes font size control with base size multiplied by current multiplier (1)', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -126,7 +127,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('returns all controls via controls getter', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -142,7 +143,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('returns individual controls via specific getters', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -160,7 +161,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('control instances have expected interface', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -179,7 +180,7 @@ describe('TypographyControlManager - Unit Tests', () => {
 
     describe('Multiplier System', () => {
         it('has default multiplier of 1', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -188,7 +189,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('updates multiplier when set', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -201,7 +202,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('does not update multiplier if set to same value', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -217,7 +218,7 @@ describe('TypographyControlManager - Unit Tests', () => {
             mockStorage = { fontSize: 48, fontWeight: 400, lineHeight: 1.5, letterSpacing: 0 };
             mockPersistentStore = createMockPersistentStore(mockStorage);
 
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -241,7 +242,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('updates font size control display value when multiplier increases', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -262,7 +263,7 @@ describe('TypographyControlManager - Unit Tests', () => {
 
     describe('Base Size Setter', () => {
         it('updates baseSize when set directly', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -273,7 +274,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('updates size control value when baseSize is set', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -284,7 +285,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('applies multiplier to size control when baseSize is set', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -298,7 +299,7 @@ describe('TypographyControlManager - Unit Tests', () => {
 
     describe('Rendered Size Calculation', () => {
         it('calculates renderedSize as baseSize * multiplier', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -307,7 +308,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('updates renderedSize when multiplier changes', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -320,7 +321,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('updates renderedSize when baseSize changes', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -340,7 +341,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         // proxy effect behavior should be tested in E2E tests.
 
         it('does NOT immediately update baseSize from control change (effect is async)', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -355,7 +356,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('updates baseSize via direct setter (synchronous)', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -380,7 +381,7 @@ describe('TypographyControlManager - Unit Tests', () => {
             };
             mockPersistentStore = createMockPersistentStore(mockStorage);
 
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -393,7 +394,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('syncs to storage after effect flush (async)', async () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -409,7 +410,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('syncs control changes to storage after effect flush (async)', async () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -422,7 +423,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('syncs height control changes to storage after effect flush (async)', async () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -434,7 +435,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('syncs spacing control changes to storage after effect flush (async)', async () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -448,7 +449,7 @@ describe('TypographyControlManager - Unit Tests', () => {
 
     describe('Control Value Getters', () => {
         it('returns current weight value', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -460,7 +461,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('returns current height value', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -472,7 +473,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('returns current spacing value', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -485,7 +486,7 @@ describe('TypographyControlManager - Unit Tests', () => {
 
         it('returns default value when control is not found', () => {
             // Create a manager with empty configs (no controls)
-            const manager = new TypographyControlManager([], mockPersistentStore);
+            const manager = new TypographySettingsManager([], mockPersistentStore);
 
             expect(manager.weight).toBe(DEFAULT_FONT_WEIGHT);
             expect(manager.height).toBe(DEFAULT_LINE_HEIGHT);
@@ -503,7 +504,7 @@ describe('TypographyControlManager - Unit Tests', () => {
             };
             mockPersistentStore = createMockPersistentStore(mockStorage);
 
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -536,7 +537,7 @@ describe('TypographyControlManager - Unit Tests', () => {
                 clear: clearSpy,
             };
 
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -547,7 +548,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('respects multiplier when resetting font size control', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -565,7 +566,7 @@ describe('TypographyControlManager - Unit Tests', () => {
 
     describe('Complex Scenarios', () => {
         it('handles changing multiplier then modifying baseSize', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -586,7 +587,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('maintains correct renderedSize throughout changes', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -608,7 +609,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('handles multiple control changes in sequence', async () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -633,7 +634,7 @@ describe('TypographyControlManager - Unit Tests', () => {
             mockStorage = { fontSize: 48, fontWeight: 400, lineHeight: 1.5, letterSpacing: 0 };
             mockPersistentStore = createMockPersistentStore(mockStorage);
 
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -645,7 +646,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('handles very small multiplier', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -658,7 +659,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('handles large base size with multiplier', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -671,7 +672,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('handles floating point precision in multiplier', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -690,7 +691,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('handles control methods (increase/decrease)', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );
@@ -704,7 +705,7 @@ describe('TypographyControlManager - Unit Tests', () => {
         });
 
         it('handles control boundary conditions', () => {
-            const manager = new TypographyControlManager(
+            const manager = new TypographySettingsManager(
                 DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
                 mockPersistentStore,
             );

src/features/SetupFont/model/index.ts

@@ -1,24 +1 @@
-export {
-    DEFAULT_FONT_SIZE,
-    DEFAULT_FONT_WEIGHT,
-    DEFAULT_LETTER_SPACING,
-    DEFAULT_LINE_HEIGHT,
-    DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
-    FONT_SIZE_STEP,
-    FONT_WEIGHT_STEP,
-    LINE_HEIGHT_STEP,
-    MAX_FONT_SIZE,
-    MAX_FONT_WEIGHT,
-    MAX_LINE_HEIGHT,
-    MIN_FONT_SIZE,
-    MIN_FONT_WEIGHT,
-    MIN_LINE_HEIGHT,
-    MULTIPLIER_L,
-    MULTIPLIER_M,
-    MULTIPLIER_S,
-} from './const/const';
-
-export {
-    type ControlId,
-    controlManager,
-} from './state/manager.svelte';
+export { typographySettingsStore } from './state/typographySettingsStore';

src/features/SetupFont/model/state/manager.svelte.ts

@@ -1,6 +0,0 @@
-import { createTypographyControlManager } from '../../lib';
-import { DEFAULT_TYPOGRAPHY_CONTROLS_DATA } from '../const/const';
-
-export type ControlId = 'font_size' | 'font_weight' | 'line_height' | 'letter_spacing';
-
-export const controlManager = createTypographyControlManager(DEFAULT_TYPOGRAPHY_CONTROLS_DATA);

src/features/SetupFont/model/state/typographySettingsStore.ts

@@ -0,0 +1,7 @@
+import { DEFAULT_TYPOGRAPHY_CONTROLS_DATA } from '$entities/Font';
+import { createTypographySettingsManager } from '../../lib';
+
+export const typographySettingsStore = createTypographySettingsManager(
+    DEFAULT_TYPOGRAPHY_CONTROLS_DATA,
+    'glyphdiff:comparison:typography',
+);

src/features/SetupFont/ui/TypographyMenu/TypographyMenu.stories.svelte

@@ -0,0 +1,45 @@
+<script module>
+import Providers from '$shared/lib/storybook/Providers.svelte';
+import { defineMeta } from '@storybook/addon-svelte-csf';
+import TypographyMenu from './TypographyMenu.svelte';
+
+const { Story } = defineMeta({
+    title: 'Features/TypographyMenu',
+    component: TypographyMenu,
+    tags: ['autodocs'],
+    parameters: {
+        docs: {
+            description: {
+                component:
+                    'Floating typography controls. Mobile/tablet: settings button that opens a popover. Desktop: inline bar with combo controls.',
+            },
+            story: { inline: false },
+        },
+        layout: 'centered',
+        storyStage: { maxWidth: 'max-w-xl' },
+    },
+    argTypes: {
+        hidden: { control: 'boolean' },
+    },
+});
+</script>
+
+<Story name="Desktop">
+    {#snippet template()}
+        <Providers>
+            <div class="relative h-20 flex items-end justify-center p-4">
+                <TypographyMenu />
+            </div>
+        </Providers>
+    {/snippet}
+</Story>
+
+<Story name="Hidden">
+    {#snippet template()}
+        <Providers>
+            <div class="relative h-20 flex items-end justify-center p-4">
+                <TypographyMenu hidden={true} />
+            </div>
+        </Providers>
+    {/snippet}
+</Story>

src/features/SetupFont/ui/TypographyMenu/TypographyMenu.svelte

@@ -1,13 +1,16 @@
 <!--
     Component: TypographyMenu
     Floating controls bar for typography settings.
-    Warm surface, sharp corners, Settings icon header, dividers between units.
     Mobile: popover with slider controls anchored to settings button.
     Desktop: inline bar with combo controls.
 -->
 <script lang="ts">
+import {
+    MULTIPLIER_L,
+    MULTIPLIER_M,
+    MULTIPLIER_S,
+} from '$entities/Font';
 import type { ResponsiveManager } from '$shared/lib';
-import { cn } from '$shared/shadcn/utils/shadcn-utils';
 import {
     Button,
     ComboControl,
@@ -17,15 +20,11 @@ import {
 import Settings2Icon from '@lucide/svelte/icons/settings-2';
 import XIcon from '@lucide/svelte/icons/x';
 import { Popover } from 'bits-ui';
+import clsx from 'clsx';
 import { getContext } from 'svelte';
 import { cubicOut } from 'svelte/easing';
 import { fly } from 'svelte/transition';
-import {
-    MULTIPLIER_L,
-    MULTIPLIER_M,
-    MULTIPLIER_S,
-    controlManager,
-} from '../../model';
+import { typographySettingsStore } from '../../model';
 
 interface Props {
     /**
@@ -37,67 +36,62 @@ interface Props {
      * @default false
      */
     hidden?: boolean;
+    /**
+     * Bindable popover open state
+     * @default false
+     */
+    open?: boolean;
 }
 
-const { class: className, hidden = false }: Props = $props();
+let { class: className, hidden = false, open = $bindable(false) }: Props = $props();
 
 const responsive = getContext<ResponsiveManager>('responsive');
 
-let isOpen = $state(false);
-
 /**
  * Sets the common font size multiplier based on the current responsive state.
  */
 $effect(() => {
-    if (!responsive) return;
+    if (!responsive) {
+        return;
+    }
     switch (true) {
         case responsive.isMobile:
-            controlManager.multiplier = MULTIPLIER_S;
+            typographySettingsStore.multiplier = MULTIPLIER_S;
             break;
         case responsive.isTablet:
-            controlManager.multiplier = MULTIPLIER_M;
+            typographySettingsStore.multiplier = MULTIPLIER_M;
             break;
         case responsive.isDesktop:
-            controlManager.multiplier = MULTIPLIER_L;
+            typographySettingsStore.multiplier = MULTIPLIER_L;
             break;
         default:
-            controlManager.multiplier = MULTIPLIER_L;
+            typographySettingsStore.multiplier = MULTIPLIER_L;
     }
 });
 </script>
 
 {#if !hidden}
-    {#if responsive.isMobile}
-        <Popover.Root bind:open={isOpen}>
+    {#if responsive.isMobileOrTablet}
+        <Popover.Root bind:open>
             <Popover.Trigger>
                 {#snippet child({ props })}
-                    <button
-                        {...props}
-                        class={cn(
-                            'inline-flex items-center justify-center',
-                            'size-8 p-0',
-                            'border border-transparent rounded-none',
-                            'transition-colors duration-150',
-                            'hover:bg-white/50 dark:hover:bg-white/5',
-                            'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-brand/30',
-                            isOpen && 'bg-paper dark:bg-dark-card border-black/5 dark:border-white/10 shadow-sm',
-                            className,
-                        )}
-                    >
-                        <Settings2Icon class="size-4" />
-                    </button>
+                    <Button class={className} variant="primary" {...props}>
+                        {#snippet icon()}
+                            <Settings2Icon class="size-4" />
+                        {/snippet}
+                    </Button>
                 {/snippet}
             </Popover.Trigger>
 
             <Popover.Portal>
                 <Popover.Content
                     side="top"
-                    align="start"
+                    align="end"
                     sideOffset={8}
-                    class={cn(
+                    class={clsx(
                         'z-50 w-72',
                         'bg-surface dark:bg-dark-card',
-                        'border border-black/5 dark:border-white/10',
+                        'border border-subtle',
                         'shadow-[0_20px_40px_-10px_rgba(0,0,0,0.15)]',
                         'rounded-none p-4',
                         'data-[state=open]:animate-in data-[state=closed]:animate-out',
@@ -110,11 +104,11 @@ $effect(() => {
                     escapeKeydownBehavior="close"
                 >
                     <!-- Header -->
-                    <div class="flex items-center justify-between mb-3 pb-3 border-b border-black/5 dark:border-white/10">
+                    <div class="flex items-center justify-between mb-3 pb-3 border-b border-subtle">
                         <div class="flex items-center gap-1.5">
                             <Settings2Icon size={12} class="text-swiss-red" />
                             <span
-                                class="text-[0.5625rem] font-mono uppercase tracking-widest font-bold text-swiss-black dark:text-neutral-200"
+                                class="text-3xs font-mono uppercase tracking-widest font-bold text-swiss-black dark:text-neutral-200"
                             >
                                 CONTROLS
                             </span>
@@ -133,7 +127,7 @@ $effect(() => {
                     </div>
 
                     <!-- Controls -->
-                    {#each controlManager.controls as control (control.id)}
+                    {#each typographySettingsStore.controls as control (control.id)}
                         <ControlGroup label={control.controlLabel ?? ''}>
                             <Slider
                                 bind:value={control.instance.value}
@@ -148,33 +142,33 @@ $effect(() => {
         </Popover.Root>
     {:else}
         <div
-            class={cn('w-full md:w-auto', className)}
+            class={clsx('w-full md:w-auto', className)}
             transition:fly={{ y: 100, duration: 200, easing: cubicOut }}
         >
             <div
-                class={cn(
+                class={clsx(
                     'flex items-center gap-1 md:gap-2 p-1.5 md:p-2',
                     'bg-surface/95 dark:bg-dark-bg/95 backdrop-blur-xl',
-                    'border border-black/5 dark:border-white/10',
+                    'border border-subtle',
                     'shadow-[0_20px_40px_-10px_rgba(0,0,0,0.1)]',
                     'rounded-none ring-1 ring-black/5 dark:ring-white/5',
                 )}
             >
                 <!-- Header: icon + label -->
-                <div class="px-2 md:px-3 flex items-center gap-1.5 md:gap-2 border-r border-black/5 dark:border-white/10 mr-1 text-swiss-black dark:text-neutral-200 shrink-0">
+                <div class="px-2 md:px-3 flex items-center gap-1.5 md:gap-2 border-r border-subtle mr-1 text-swiss-black dark:text-neutral-200 shrink-0">
                     <Settings2Icon
                         size={14}
                         class="text-swiss-red"
                     />
                     <span
-                        class="text-[0.5625rem] md:text-[0.625rem] font-mono uppercase tracking-widest font-bold hidden sm:inline whitespace-nowrap"
+                        class="text-3xs md:text-2xs font-mono uppercase tracking-widest font-bold hidden sm:inline whitespace-nowrap"
                     >
                         GLOBAL_CONTROLS
                     </span>
                 </div>
 
                 <!-- Controls with dividers between each -->
-                {#each controlManager.controls as control, i (control.id)}
+                {#each typographySettingsStore.controls as control, i (control.id)}
                     {#if i > 0}
                         <div class="w-px h-6 md:h-8 bg-black/5 dark:bg-white/10 mx-0.5 md:mx-1 shrink-0"></div>
                     {/if}

src/main.ts

@@ -1,3 +1,9 @@
+/**
+ * Application entry point
+ *
+ * Mounts the main App component to the DOM and initializes
+ * global styles.
+ */
 import App from '$app/App.svelte';
 import { mount } from 'svelte';
 import '$app/styles/app.css';

src/routes/Page.svelte

@@ -3,10 +3,7 @@
     Description: The main page component of the application.
 -->
 <script lang="ts">
-import { scrollBreadcrumbsStore } from '$entities/Breadcrumb';
 import { ComparisonView } from '$widgets/ComparisonView';
-import { FontSearchSection } from '$widgets/FontSearch';
-import { SampleListSection } from '$widgets/SampleList';
 import { cubicIn } from 'svelte/easing';
 import { fade } from 'svelte/transition';
 </script>
@@ -15,11 +12,7 @@ import { fade } from 'svelte/transition';
     class="h-full flex flex-col gap-3 sm:gap-4"
     in:fade={{ duration: 500, delay: 150, easing: cubicIn }}
 >
-    <section class="w-auto">
+    <main class="w-auto">
         <ComparisonView />
-    </section>
-    <main class="w-full pt-0 pb-10 sm:px-6 sm:pt-16 sm:pb-12 md:px-8 md:pt-32 md:pb-16 lg:px-10 lg:pt-48 lg:pb-20 xl:px-16">
-        <FontSearchSection />
-        <SampleListSection index={1} />
     </main>
 </div>

src/shared/api/api.ts

@@ -41,10 +41,14 @@ export class ApiError extends Error {
      * @param response - Original fetch Response object
      */
     constructor(
-        /** HTTP status code */
+        /**
+         * HTTP status code
+         */
         public status: number,
         message: string,
-        /** Original Response object for inspection */
+        /**
+         * Original Response object for inspection
+         */
         public response?: Response,
     ) {
         super(message);

src/shared/api/queryClient.ts

@@ -15,15 +15,25 @@ import { QueryClient } from '@tanstack/query-core';
 export const queryClient = new QueryClient({
     defaultOptions: {
         queries: {
-            /** Data remains fresh for 5 minutes after fetch */
+            /**
+             * Data remains fresh for 5 minutes after fetch
+             */
             staleTime: 5 * 60 * 1000,
-            /** Unused cache entries are removed after 10 minutes */
+            /**
+             * Unused cache entries are removed after 10 minutes
+             */
             gcTime: 10 * 60 * 1000,
-            /** Don't refetch when window regains focus */
+            /**
+             * Don't refetch when window regains focus
+             */
             refetchOnWindowFocus: false,
-            /** Refetch on mount if data is stale */
+            /**
+             * Refetch on mount if data is stale
+             */
             refetchOnMount: true,
-            /** Retry failed requests up to 3 times */
+            /**
+             * Retry failed requests up to 3 times
+             */
             retry: 3,
             /**
              * Exponential backoff for retries

src/shared/api/queryKeys.test.ts

@@ -0,0 +1,73 @@
+import {
+    describe,
+    expect,
+    it,
+} from 'vitest';
+import { fontKeys } from './queryKeys';
+
+describe('fontKeys', () => {
+    describe('Hierarchy', () => {
+        it('should generate base keys', () => {
+            expect(fontKeys.all).toEqual(['fonts']);
+            expect(fontKeys.lists()).toEqual(['fonts', 'list']);
+            expect(fontKeys.batches()).toEqual(['fonts', 'batch']);
+            expect(fontKeys.details()).toEqual(['fonts', 'detail']);
+        });
+    });
+
+    describe('Batch Keys (Stability & Sorting)', () => {
+        it('should sort IDs for stable serialization', () => {
+            const key1 = fontKeys.batch(['b', 'a', 'c']);
+            const key2 = fontKeys.batch(['c', 'b', 'a']);
+            const expected = ['fonts', 'batch', ['a', 'b', 'c']];
+            expect(key1).toEqual(expected);
+            expect(key2).toEqual(expected);
+        });
+
+        it('should handle empty ID arrays', () => {
+            expect(fontKeys.batch([])).toEqual(['fonts', 'batch', []]);
+        });
+
+        it('should not mutate the input array when sorting', () => {
+            const ids = ['c', 'b', 'a'];
+            fontKeys.batch(ids);
+            expect(ids).toEqual(['c', 'b', 'a']);
+        });
+
+        it('batch key should be rooted in batches() base', () => {
+            const key = fontKeys.batch(['a']);
+            expect(key.slice(0, 2)).toEqual(fontKeys.batches());
+        });
+    });
+
+    describe('List Keys (Parameters)', () => {
+        it('should include parameters in list keys', () => {
+            const params = { provider: 'google' };
+            expect(fontKeys.list(params)).toEqual(['fonts', 'list', params]);
+        });
+
+        it('should handle empty parameters', () => {
+            expect(fontKeys.list({})).toEqual(['fonts', 'list', {}]);
+        });
+
+        it('list key should be rooted in lists() base', () => {
+            const key = fontKeys.list({ provider: 'google' });
+            expect(key.slice(0, 2)).toEqual(fontKeys.lists());
+        });
+    });
+
+    describe('Detail Keys', () => {
+        it('should generate unique detail keys per ID', () => {
+            expect(fontKeys.detail('roboto')).toEqual(['fonts', 'detail', 'roboto']);
+        });
+
+        it('should generate different keys for different IDs', () => {
+            expect(fontKeys.detail('roboto')).not.toEqual(fontKeys.detail('open-sans'));
+        });
+
+        it('detail key should be rooted in details() base', () => {
+            const key = fontKeys.detail('roboto');
+            expect(key.slice(0, 2)).toEqual(fontKeys.details());
+        });
+    });
+});

src/shared/api/queryKeys.ts

@@ -0,0 +1,37 @@
+/**
+ * Stable query key factory for font-related queries.
+ * Ensures consistent serialization for batch requests by sorting IDs.
+ */
+export const fontKeys = {
+    /**
+     * Base key for all font queries
+     */
+    all: ['fonts'] as const,
+
+    /**
+     * Keys for font list queries
+     */
+    lists: () => [...fontKeys.all, 'list'] as const,
+    /**
+     * Specific font list key with filter parameters
+     */
+    list: (params: object) => [...fontKeys.lists(), params] as const,
+
+    /**
+     * Keys for font batch queries
+     */
+    batches: () => [...fontKeys.all, 'batch'] as const,
+    /**
+     * Specific batch key, sorted for stability
+     */
+    batch: (ids: string[]) => [...fontKeys.batches(), [...ids].sort()] as const,
+
+    /**
+     * Keys for font detail queries
+     */
+    details: () => [...fontKeys.all, 'detail'] as const,
+    /**
+     * Specific font detail key by ID
+     */
+    detail: (id: string) => [...fontKeys.details(), id] as const,
+} as const;

src/shared/lib/helpers/BaseQueryStore.svelte.ts

@@ -0,0 +1,51 @@
+import { queryClient } from '$shared/api/queryClient';
+import {
+    QueryObserver,
+    type QueryObserverOptions,
+    type QueryObserverResult,
+} from '@tanstack/query-core';
+
+/**
+ * Abstract base class for reactive Svelte 5 stores backed by TanStack Query.
+ *
+ * Provides a unified way to use TanStack Query observers within Svelte 5 classes
+ * using runes for reactivity. Handles subscription lifecycle automatically.
+ *
+ * @template TData - The type of data returned by the query.
+ * @template TError - The type of error that can be thrown.
+ */
+export abstract class BaseQueryStore<TData, TError = Error> {
+    #result = $state<QueryObserverResult<TData, TError>>({} as QueryObserverResult<TData, TError>);
+    #observer: QueryObserver<TData, TError>;
+    #unsubscribe: () => void;
+
+    constructor(options: QueryObserverOptions<TData, TError, TData, any, any>) {
+        this.#observer = new QueryObserver(queryClient, options);
+        this.#unsubscribe = this.#observer.subscribe(result => {
+            this.#result = result;
+        });
+    }
+
+    /**
+     * Current query result (reactive)
+     */
+    protected get result(): QueryObserverResult<TData, TError> {
+        return this.#result;
+    }
+
+    /**
+     * Updates observer options dynamically.
+     * Use this when query parameters or dependencies change.
+     */
+    protected updateOptions(options: QueryObserverOptions<TData, TError, TData, any, any>): void {
+        this.#observer.setOptions(options);
+    }
+
+    /**
+     * Cleans up the observer subscription.
+     * Should be called when the store is no longer needed.
+     */
+    destroy(): void {
+        this.#unsubscribe();
+    }
+}

src/shared/lib/helpers/BaseQueryStore.test.ts

@@ -0,0 +1,91 @@
+import { queryClient } from '$shared/api/queryClient';
+import {
+    beforeEach,
+    describe,
+    expect,
+    it,
+    vi,
+} from 'vitest';
+import { BaseQueryStore } from './BaseQueryStore.svelte';
+
+class TestStore extends BaseQueryStore<string> {
+    constructor(key = ['test'], fn = () => Promise.resolve('ok')) {
+        super({
+            queryKey: key,
+            queryFn: fn,
+            retry: false, // Disable retries for faster error testing
+        });
+    }
+    get data() {
+        return this.result.data;
+    }
+    get isLoading() {
+        return this.result.isLoading;
+    }
+    get isError() {
+        return this.result.isError;
+    }
+
+    update(newKey: string[], newFn?: () => Promise<string>) {
+        this.updateOptions({
+            queryKey: newKey,
+            queryFn: newFn ?? (() => Promise.resolve('ok')),
+            retry: false,
+        });
+    }
+}
+
+import * as tq from '@tanstack/query-core';
+
+// ... (TestStore remains same)
+
+describe('BaseQueryStore', () => {
+    beforeEach(() => {
+        queryClient.clear();
+    });
+
+    describe('Lifecycle & Fetching', () => {
+        it('should transition from loading to success', async () => {
+            const store = new TestStore();
+            expect(store.isLoading).toBe(true);
+            await vi.waitFor(() => expect(store.data).toBe('ok'), { timeout: 1000 });
+            expect(store.isLoading).toBe(false);
+        });
+
+        it('should have undefined data and no error in initial loading state', () => {
+            const store = new TestStore(['initial-state'], () => new Promise(r => setTimeout(() => r('late'), 500)));
+            expect(store.data).toBeUndefined();
+            expect(store.isError).toBe(false);
+        });
+    });
+
+    describe('Error Handling', () => {
+        it('should handle query failures', async () => {
+            const store = new TestStore(['fail'], () => Promise.reject(new Error('fail')));
+            await vi.waitFor(() => expect(store.isError).toBe(true), { timeout: 1000 });
+        });
+    });
+
+    describe('Reactivity', () => {
+        it('should refetch and update data when options change', async () => {
+            const store = new TestStore(['key1'], () => Promise.resolve('val1'));
+            await vi.waitFor(() => expect(store.data).toBe('val1'), { timeout: 1000 });
+
+            store.update(['key2'], () => Promise.resolve('val2'));
+            await vi.waitFor(() => expect(store.data).toBe('val2'), { timeout: 1000 });
+        });
+    });
+
+    describe('Cleanup', () => {
+        it('should unsubscribe observer on destroy', () => {
+            const unsubscribe = vi.fn();
+            const subscribeSpy = vi.spyOn(tq.QueryObserver.prototype, 'subscribe').mockReturnValue(unsubscribe);
+
+            const store = new TestStore();
+            store.destroy();
+
+            expect(unsubscribe).toHaveBeenCalled();
+            subscribeSpy.mockRestore();
+        });
+    });
+});

src/shared/lib/helpers/CharacterComparisonEngine/CharacterComparisonEngine.svelte.ts

@@ -0,0 +1,345 @@
+import {
+    type PreparedTextWithSegments,
+    layoutWithLines,
+    prepareWithSegments,
+} from '@chenglou/pretext';
+
+/**
+ * A single laid-out line produced by dual-font comparison layout.
+ *
+ * Line breaking is determined by the unified worst-case widths, so both fonts
+ * always break at identical positions. Per-character `xA`/`xB` offsets reflect
+ * each font's actual advance widths independently.
+ */
+export interface ComparisonLine {
+    /**
+     * Full text of this line as returned by pretext.
+     */
+    text: string;
+    /**
+     * Rendered width of this line in pixels — maximum across font A and font B.
+     */
+    width: number;
+    /**
+     * Individual character metadata for both fonts in this line
+     */
+    chars: Array<{
+        /**
+         * The grapheme cluster string (may be >1 code unit for emoji, etc.).
+         */
+        char: string;
+        /**
+         * X offset from the start of the line in font A, in pixels.
+         */
+        xA: number;
+        /**
+         * Advance width of this grapheme in font A, in pixels.
+         */
+        widthA: number;
+        /**
+         * X offset from the start of the line in font B, in pixels.
+         */
+        xB: number;
+        /**
+         * Advance width of this grapheme in font B, in pixels.
+         */
+        widthB: number;
+    }>;
+}
+
+/**
+ * Aggregated output of a dual-font layout pass.
+ */
+export interface ComparisonResult {
+    /**
+     * Per-line grapheme data for both fonts. Empty when input text is empty.
+     */
+    lines: ComparisonLine[];
+    /**
+     * Total height in pixels. Equals `lines.length * lineHeight` (pretext guarantee).
+     */
+    totalHeight: number;
+}
+
+/**
+ * Dual-font text layout engine backed by `@chenglou/pretext`.
+ *
+ * Computes identical line breaks for two fonts simultaneously by constructing a
+ * "unified" prepared-text object whose per-glyph widths are the worst-case maximum
+ * of font A and font B. This guarantees that both fonts wrap at exactly the same
+ * positions, making side-by-side or slider comparison visually coherent.
+ *
+ * **Two-level caching strategy**
+ * 1. Font-change cache (`#preparedA`, `#preparedB`, `#unifiedPrepared`): rebuilt only
+ *    when `text`, `fontA`, or `fontB` changes. `prepareWithSegments` is expensive
+ *    (canvas measurement), so this avoids re-measuring during slider interaction.
+ * 2. Layout cache (`#lastResult`): rebuilt when `width` or `lineHeight` changes but
+ *    the fonts have not changed. Line-breaking is cheap relative to measurement, but
+ *    still worth skipping on every render tick.
+ *
+ * **`as any` casts:** `PreparedTextWithSegments` exposes only the `segments` field in
+ * its public TypeScript type. The numeric arrays (`widths`, `breakableFitAdvances`,
+ * `lineEndFitAdvances`, `lineEndPaintAdvances`) are internal implementation details of
+ * pretext that are not part of the published type signature. The casts are required to
+ * access these fields; they are verified against the pretext source at
+ * `node_modules/@chenglou/pretext/src/layout.ts`.
+ */
+export class CharacterComparisonEngine {
+    #segmenter: Intl.Segmenter;
+
+    // Cached prepared data
+    #preparedA: PreparedTextWithSegments | null = null;
+    #preparedB: PreparedTextWithSegments | null = null;
+    #unifiedPrepared: PreparedTextWithSegments | null = null;
+
+    #lastText = '';
+    #lastFontA = '';
+    #lastFontB = '';
+    #lastSpacing = 0;
+    #lastSize = 0;
+
+    // Cached layout results
+    #lastWidth = -1;
+    #lastLineHeight = -1;
+    #lastResult = $state<ComparisonResult | null>(null);
+
+    constructor(locale?: string) {
+        this.#segmenter = new Intl.Segmenter(locale, { granularity: 'grapheme' });
+    }
+
+    /**
+     * Lay out `text` using both fonts within `width` pixels.
+     *
+     * Line breaks are determined by the worst-case (maximum) glyph widths across
+     * both fonts, so both fonts always wrap at identical positions.
+     *
+     * @param text       Raw text to lay out.
+     * @param fontA      CSS font string for the first font: `"weight sizepx \"family\""`.
+     * @param fontB      CSS font string for the second font: `"weight sizepx \"family\""`.
+     * @param width      Available line width in pixels.
+     * @param lineHeight Line height in pixels (passed directly to pretext).
+     * @param spacing    Letter spacing in em (from typography settings).
+     * @param size       Current font size in pixels (used to convert spacing em to px).
+     * @returns          Per-line grapheme data for both fonts. Empty `lines` when `text` is empty.
+     */
+    layout(
+        text: string,
+        fontA: string,
+        fontB: string,
+        width: number,
+        lineHeight: number,
+        spacing: number = 0,
+        size: number = 16,
+    ): ComparisonResult {
+        if (!text) {
+            return { lines: [], totalHeight: 0 };
+        }
+
+        const spacingPx = spacing * size;
+
+        const isFontChange = text !== this.#lastText
+            || fontA !== this.#lastFontA
+            || fontB !== this.#lastFontB
+            || spacing !== this.#lastSpacing
+            || size !== this.#lastSize;
+
+        const isLayoutChange = width !== this.#lastWidth || lineHeight !== this.#lastLineHeight;
+
+        if (!isFontChange && !isLayoutChange && this.#lastResult) {
+            return this.#lastResult;
+        }
+
+        // 1. Prepare (or use cache)
+        if (isFontChange) {
+            this.#preparedA = prepareWithSegments(text, fontA);
+            this.#preparedB = prepareWithSegments(text, fontB);
+            this.#unifiedPrepared = this.#createUnifiedPrepared(this.#preparedA, this.#preparedB, spacingPx);
+
+            this.#lastText = text;
+            this.#lastFontA = fontA;
+            this.#lastFontB = fontB;
+            this.#lastSpacing = spacing;
+            this.#lastSize = size;
+        }
+
+        if (!this.#unifiedPrepared || !this.#preparedA || !this.#preparedB) {
+            return { lines: [], totalHeight: 0 };
+        }
+
+        // 2. Layout using the unified widths.
+        // `PreparedTextWithSegments` only exposes `segments` in its public type; cast to `any`
+        // so pretext's layoutWithLines can read the internal numeric arrays at runtime.
+        const { lines, height } = layoutWithLines(this.#unifiedPrepared as any, width, lineHeight);
+
+        // 3. Map results back to both fonts
+        const resultLines: ComparisonLine[] = lines.map(line => {
+            const chars: ComparisonLine['chars'] = [];
+            let currentXA = 0;
+            let currentXB = 0;
+
+            const start = line.start;
+            const end = line.end;
+
+            // Cast to `any`: accessing internal numeric arrays not in the public type signature.
+            const intA = this.#preparedA as any;
+            const intB = this.#preparedB as any;
+
+            for (let sIdx = start.segmentIndex; sIdx <= end.segmentIndex; sIdx++) {
+                const segmentText = this.#preparedA!.segments[sIdx];
+                if (segmentText === undefined) {
+                    continue;
+                }
+
+                const graphemes = Array.from(this.#segmenter.segment(segmentText), s => s.segment);
+
+                const advA = intA.breakableFitAdvances[sIdx];
+                const advB = intB.breakableFitAdvances[sIdx];
+
+                const gStart = sIdx === start.segmentIndex ? start.graphemeIndex : 0;
+                const gEnd = sIdx === end.segmentIndex ? end.graphemeIndex : graphemes.length;
+
+                for (let gIdx = gStart; gIdx < gEnd; gIdx++) {
+                    const char = graphemes[gIdx];
+                    let wA = advA != null ? advA[gIdx]! : intA.widths[sIdx]!;
+                    let wB = advB != null ? advB[gIdx]! : intB.widths[sIdx]!;
+
+                    // Apply letter spacing (tracking) to the width of each character
+                    wA += spacingPx;
+                    wB += spacingPx;
+
+                    chars.push({
+                        char,
+                        xA: currentXA,
+                        widthA: wA,
+                        xB: currentXB,
+                        widthB: wB,
+                    });
+                    currentXA += wA;
+                    currentXB += wB;
+                }
+            }
+
+            return {
+                text: line.text,
+                width: line.width,
+                chars,
+            };
+        });
+
+        this.#lastWidth = width;
+        this.#lastLineHeight = lineHeight;
+        this.#lastResult = {
+            lines: resultLines,
+            totalHeight: height,
+        };
+
+        return this.#lastResult;
+    }
+
+    /**
+     * Calculates character states for an entire line in a single sequential pass.
+     *
+     * Walks characters left-to-right, accumulating the running x position using
+     * each character's actual rendered width: `widthB` for already-morphed characters
+     * (isPast=true) and `widthA` for upcoming ones. This ensures thresholds stay
+     * aligned with the visual DOM layout even when the two fonts have different widths.
+     *
+     * @param line           A single laid-out line from the last layout result.
+     * @param sliderPos      Current slider position as a percentage (0–100) of `containerWidth`.
+     * @param containerWidth Total container width in pixels.
+     * @returns              Per-character `proximity` and `isPast` in the same order as `line.chars`.
+     */
+    getLineCharStates(
+        line: ComparisonLine,
+        sliderPos: number,
+        containerWidth: number,
+    ): Array<{ proximity: number; isPast: boolean }> {
+        if (!line) {
+            return [];
+        }
+        const chars = line.chars;
+        const n = chars.length;
+        const sliderX = (sliderPos / 100) * containerWidth;
+        const range = 5;
+        // Prefix sums of widthA (left chars will be past → use widthA).
+        // Suffix sums of widthB (right chars will not be past → use widthB).
+        // This lets us compute, for each char i, what the total line width and
+        // char center would be at the exact moment the slider crosses that char:
+        //   left side (0..i-1) already past → font A widths
+        //   right side (i+1..n-1) not yet past → font B widths
+        const prefA = new Float64Array(n + 1);
+        const sufB = new Float64Array(n + 1);
+        for (let i = 0; i < n; i++) {
+            prefA[i + 1] = prefA[i] + chars[i].widthA;
+        }
+        for (let i = n - 1; i >= 0; i--) {
+            sufB[i] = sufB[i + 1] + chars[i].widthB;
+        }
+        // Per-char threshold: slider x at which this char should toggle isPast.
+        const thresholds = new Float64Array(n);
+        for (let i = 0; i < n; i++) {
+            const totalWidth = prefA[i] + chars[i].widthA + sufB[i + 1];
+            const xOffset = (containerWidth - totalWidth) / 2;
+            thresholds[i] = xOffset + prefA[i] + chars[i].widthA / 2;
+        }
+        // Determine isPast for each char at the current slider position.
+        const isPastArr = new Uint8Array(n);
+        for (let i = 0; i < n; i++) {
+            isPastArr[i] = sliderX > thresholds[i] ? 1 : 0;
+        }
+        // Compute visual positions based on actual rendered widths (font A if past, B if not).
+        const totalRendered = chars.reduce((s, c, i) => s + (isPastArr[i] ? c.widthA : c.widthB), 0);
+        const xOffset = (containerWidth - totalRendered) / 2;
+        let currentX = xOffset;
+        return chars.map((char, i) => {
+            const isPast = isPastArr[i] === 1;
+            const charWidth = isPast ? char.widthA : char.widthB;
+            const visualCenter = currentX + charWidth / 2;
+            const charGlobalPercent = (visualCenter / containerWidth) * 100;
+            const distance = Math.abs(sliderPos - charGlobalPercent);
+            const proximity = Math.max(0, 1 - distance / range);
+            currentX += charWidth;
+            return { proximity, isPast };
+        });
+    }
+
+    /**
+     * Internal helper to merge two prepared texts into a "worst-case" unified version
+     */
+    #createUnifiedPrepared(
+        a: PreparedTextWithSegments,
+        b: PreparedTextWithSegments,
+        spacingPx: number = 0,
+    ): PreparedTextWithSegments {
+        // Cast to `any`: accessing internal numeric arrays not in the public type signature.
+        const intA = a as any;
+        const intB = b as any;
+
+        const unified = { ...intA };
+
+        unified.widths = intA.widths.map((w: number, i: number) => Math.max(w, intB.widths[i]) + spacingPx);
+        unified.lineEndFitAdvances = intA.lineEndFitAdvances.map((w: number, i: number) =>
+            Math.max(w, intB.lineEndFitAdvances[i]) + spacingPx
+        );
+        unified.lineEndPaintAdvances = intA.lineEndPaintAdvances.map((w: number, i: number) =>
+            Math.max(w, intB.lineEndPaintAdvances[i]) + spacingPx
+        );
+
+        unified.breakableFitAdvances = intA.breakableFitAdvances.map((advA: number[] | null, i: number) => {
+            const advB = intB.breakableFitAdvances[i];
+            if (!advA && !advB) {
+                return null;
+            }
+            if (!advA) {
+                return advB.map((w: number) => w + spacingPx);
+            }
+            if (!advB) {
+                return advA.map((w: number) => w + spacingPx);
+            }
+
+            return advA.map((w: number, j: number) => Math.max(w, advB[j]) + spacingPx);
+        });
+
+        return unified;
+    }
+}

src/shared/lib/helpers/CharacterComparisonEngine/CharacterComparisonEngine.test.ts

@@ -0,0 +1,160 @@
+// @vitest-environment jsdom
+import { clearCache } from '@chenglou/pretext';
+import {
+    beforeEach,
+    describe,
+    expect,
+    it,
+} from 'vitest';
+import { installCanvasMock } from '../__mocks__/canvas';
+import { CharacterComparisonEngine } from './CharacterComparisonEngine.svelte';
+
+// FontA: 10px per character. FontB: 15px per character.
+// The mock dispatches on whether the font string contains 'FontA' or 'FontB'.
+const FONT_A_WIDTH = 10;
+const FONT_B_WIDTH = 15;
+
+function fontWidthFactory(font: string, text: string): number {
+    const perChar = font.includes('FontA') ? FONT_A_WIDTH : FONT_B_WIDTH;
+    return text.length * perChar;
+}
+
+describe('CharacterComparisonEngine', () => {
+    let engine: CharacterComparisonEngine;
+
+    beforeEach(() => {
+        installCanvasMock(fontWidthFactory);
+        clearCache();
+        engine = new CharacterComparisonEngine();
+    });
+
+    it('returns empty result for empty string', () => {
+        const result = engine.layout('', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        expect(result.lines).toHaveLength(0);
+        expect(result.totalHeight).toBe(0);
+    });
+
+    it('uses worst-case width across both fonts to determine line breaks', () => {
+        // 'AB CD' — two 2-char words separated by a space.
+        // FontA: 'AB'=20px, 'CD'=20px. Both fit in 25px? No: 'AB CD' = 50px total.
+        // FontB: 'AB'=30px, 'CD'=30px. Width 35px forces wrap after 'AB '.
+        // Unified must use FontB widths — so it must wrap at the same place FontB wraps.
+        const result = engine.layout('AB CD', '400 16px "FontA"', '400 16px "FontB"', 35, 20);
+        expect(result.lines.length).toBeGreaterThan(1);
+        // First line text must not include both words.
+        expect(result.lines[0].text).not.toContain('CD');
+    });
+
+    it('provides xA and xB offsets for both fonts on a single line', () => {
+        // 'ABC' fits in 500px for both fonts.
+        // FontA: A@0(w=10), B@10(w=10), C@20(w=10)
+        // FontB: A@0(w=15), B@15(w=15), C@30(w=15)
+        const result = engine.layout('ABC', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const chars = result.lines[0].chars;
+
+        expect(chars).toHaveLength(3);
+
+        expect(chars[0].xA).toBe(0);
+        expect(chars[0].widthA).toBe(FONT_A_WIDTH);
+        expect(chars[0].xB).toBe(0);
+        expect(chars[0].widthB).toBe(FONT_B_WIDTH);
+
+        expect(chars[1].xA).toBe(FONT_A_WIDTH); // 10
+        expect(chars[1].widthA).toBe(FONT_A_WIDTH);
+        expect(chars[1].xB).toBe(FONT_B_WIDTH); // 15
+        expect(chars[1].widthB).toBe(FONT_B_WIDTH);
+
+        expect(chars[2].xA).toBe(FONT_A_WIDTH * 2); // 20
+        expect(chars[2].xB).toBe(FONT_B_WIDTH * 2); // 30
+    });
+
+    it('xA positions are monotonically increasing', () => {
+        const result = engine.layout('ABCDE', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const chars = result.lines[0].chars;
+        for (let i = 1; i < chars.length; i++) {
+            expect(chars[i].xA).toBeGreaterThan(chars[i - 1].xA);
+        }
+    });
+
+    it('xB positions are monotonically increasing', () => {
+        const result = engine.layout('ABCDE', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const chars = result.lines[0].chars;
+        for (let i = 1; i < chars.length; i++) {
+            expect(chars[i].xB).toBeGreaterThan(chars[i - 1].xB);
+        }
+    });
+
+    it('returns cached result when called again with same arguments', () => {
+        const r1 = engine.layout('ABC', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const r2 = engine.layout('ABC', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        expect(r2).toBe(r1); // strict reference equality — same object
+    });
+
+    it('re-computes when text changes', () => {
+        const r1 = engine.layout('ABC', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const r2 = engine.layout('DEF', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        expect(r2).not.toBe(r1);
+        expect(r2.lines[0].text).not.toBe(r1.lines[0].text);
+    });
+
+    it('re-computes when width changes', () => {
+        const r1 = engine.layout('Hello World', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const r2 = engine.layout('Hello World', '400 16px "FontA"', '400 16px "FontB"', 60, 20);
+        expect(r2).not.toBe(r1);
+    });
+
+    it('re-computes when fontA changes', () => {
+        const r1 = engine.layout('ABC', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const r2 = engine.layout('ABC', '400 24px "FontA"', '400 16px "FontB"', 500, 20);
+        expect(r2).not.toBe(r1);
+    });
+
+    it('getLineCharStates returns proximity 1 when slider is exactly over char center', () => {
+        const containerWidth = 500;
+        const result = engine.layout('A', '400 16px "FontA"', '400 16px "FontB"', containerWidth, 20);
+        // Single char: no neighbors → totalWidth = widthA, threshold = containerWidth/2.
+        // When isPast=false, visual center = (containerWidth - widthB)/2 + widthB/2 = containerWidth/2.
+        // So proximity=1 at exactly 50%.
+        const charPercent = 50;
+
+        const states = engine.getLineCharStates(result.lines[0], charPercent, containerWidth);
+        expect(states[0]?.proximity).toBe(1);
+        expect(states[0]?.isPast).toBe(false);
+    });
+
+    it('getLineCharStates returns proximity 0 when slider is far from char', () => {
+        const result = engine.layout('A', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const states = engine.getLineCharStates(result.lines[0], 0, 500);
+        expect(states[0]?.proximity).toBe(0);
+    });
+
+    it('getLineCharStates isPast is true when slider has passed char center', () => {
+        const result = engine.layout('A', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const states = engine.getLineCharStates(result.lines[0], 100, 500);
+        expect(states[0]?.isPast).toBe(true);
+    });
+
+    it('getLineCharStates returns empty array for out-of-range lineIndex', () => {
+        const result = engine.layout('A', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        // Passing an undefined object because the index doesn't exist.
+        const states = engine.getLineCharStates(result.lines[99], 50, 500);
+        expect(states).toEqual([]);
+    });
+
+    it('getLineCharStates returns empty array before layout() has been called', () => {
+        // Passing an undefined object because layout() hasn't been called.
+        const states = engine.getLineCharStates(undefined as any, 50, 500);
+        expect(states).toEqual([]);
+    });
+
+    it('getLineCharStates returns safe defaults for all chars', () => {
+        const result = engine.layout('A', '400 16px "FontA"', '400 16px "FontB"', 500, 20);
+        const states = engine.getLineCharStates(result.lines[0], 50, 500);
+        expect(states.length).toBeGreaterThan(0);
+        for (const s of states) {
+            expect(s.proximity).toBeGreaterThanOrEqual(0);
+            expect(s.proximity).toBeLessThanOrEqual(1);
+            expect(typeof s.isPast).toBe('boolean');
+        }
+    });
+});

src/shared/lib/helpers/TextLayoutEngine/TextLayoutEngine.svelte.ts

@@ -0,0 +1,175 @@
+import {
+    layoutWithLines,
+    prepareWithSegments,
+} from '@chenglou/pretext';
+
+/**
+ * A single laid-out line of text, with per-grapheme x offsets and widths.
+ *
+ * `chars` is indexed by grapheme cluster (not UTF-16 code unit), so emoji
+ * sequences and combining characters each produce exactly one entry.
+ */
+export interface LayoutLine {
+    /**
+     * Full text of this line as returned by pretext.
+     */
+    text: string;
+    /**
+     * Rendered width of this line in pixels.
+     */
+    width: number;
+    /**
+     * Individual character metadata for this line
+     */
+    chars: Array<{
+        /**
+         * The grapheme cluster string (may be >1 code unit for emoji, etc.).
+         */
+        char: string;
+        /**
+         * X offset from the start of the line, in pixels.
+         */
+        x: number;
+        /**
+         * Advance width of this grapheme, in pixels.
+         */
+        width: number;
+    }>;
+}
+
+/**
+ * Aggregated output of a single-font layout pass.
+ */
+export interface LayoutResult {
+    /**
+     * Per-line grapheme data. Empty when input text is empty.
+     */
+    lines: LayoutLine[];
+    /**
+     * Total height in pixels. Equals `lines.length * lineHeight` (pretext guarantee).
+     */
+    totalHeight: number;
+}
+
+/**
+ * Single-font text layout engine backed by `@chenglou/pretext`.
+ *
+ * Replaces the canvas-DOM hybrid `createCharacterComparison` for cases where
+ * only one font is needed. For dual-font comparison use `CharacterComparisonEngine`.
+ *
+ * **Usage**
+ * ```ts
+ * const engine = new TextLayoutEngine();
+ * const result = engine.layout('Hello World', '400 16px "Inter"', 320, 24);
+ * // result.lines[0].chars → [{ char: 'H', x: 0, width: 9 }, ...]
+ * ```
+ *
+ * **Font string format:** `"${weight} ${size}px \"${family}\""` — e.g. `'400 16px "Inter"'`.
+ * This matches what SliderArea constructs from `typography.weight` and `typography.renderedSize`.
+ *
+ * **Canvas requirement:** pretext calls `document.createElement('canvas').getContext('2d')` on
+ * first use and caches the context for the process lifetime. Tests must install a canvas mock
+ * (see `__mocks__/canvas.ts`) before the first `layout()` call.
+ */
+export class TextLayoutEngine {
+    /**
+     * Grapheme segmenter used to split segment text into individual clusters.
+     *
+     * Pretext maintains its own internal segmenter for line-breaking decisions.
+     * We keep a separate one here so we can iterate graphemes in `layout()`
+     * without depending on pretext internals — the two segmenters produce
+     * identical boundaries because both use `{ granularity: 'grapheme' }`.
+     */
+    #segmenter: Intl.Segmenter;
+
+    /**
+     * @param locale BCP 47 language tag passed to Intl.Segmenter. Defaults to the runtime locale.
+     */
+    constructor(locale?: string) {
+        this.#segmenter = new Intl.Segmenter(locale, { granularity: 'grapheme' });
+    }
+
+    /**
+     * Lay out `text` in the given `font` within `width` pixels.
+     *
+     * @param text       Raw text to lay out.
+     * @param font       CSS font string: `"weight sizepx \"family\""`.
+     * @param width      Available line width in pixels.
+     * @param lineHeight Line height in pixels (passed directly to pretext).
+     * @returns          Per-line grapheme data. Empty `lines` when `text` is empty.
+     */
+    layout(text: string, font: string, width: number, lineHeight: number): LayoutResult {
+        if (!text) {
+            return { lines: [], totalHeight: 0 };
+        }
+
+        // prepareWithSegments measures the text and builds the segment data structure
+        // (widths, breakableFitAdvances, etc.) that the line-walker consumes.
+        const prepared = prepareWithSegments(text, font);
+        const { lines, height } = layoutWithLines(prepared, width, lineHeight);
+
+        // `PreparedTextWithSegments` has these fields in its public type definition
+        // but the TypeScript signature only exposes `segments`. We cast to `any` to
+        // access the parallel numeric arrays — they are documented in the plan and
+        // verified against the pretext source at node_modules/@chenglou/pretext/src/layout.ts.
+        const internal = prepared as any;
+        const breakableFitAdvances = internal.breakableFitAdvances as (number[] | null)[];
+        const widths = internal.widths as number[];
+
+        const resultLines: LayoutLine[] = lines.map(line => {
+            const chars: LayoutLine['chars'] = [];
+            let currentX = 0;
+
+            const start = line.start;
+            const end = line.end;
+
+            // Walk every segment that falls within this line's [start, end] cursors.
+            // Both cursors are grapheme-level: start is inclusive, end is exclusive.
+            for (let sIdx = start.segmentIndex; sIdx <= end.segmentIndex; sIdx++) {
+                const segmentText = prepared.segments[sIdx];
+                if (segmentText === undefined) {
+                    continue;
+                }
+
+                const graphemes = Array.from(this.#segmenter.segment(segmentText), s => s.segment);
+                const advances = breakableFitAdvances[sIdx];
+
+                // For the first and last segments of the line the cursor may point
+                // into the middle of the segment — respect those boundaries.
+                // All intermediate segments are walked in full (gStart=0, gEnd=length).
+                const gStart = sIdx === start.segmentIndex ? start.graphemeIndex : 0;
+                const gEnd = sIdx === end.segmentIndex ? end.graphemeIndex : graphemes.length;
+
+                for (let gIdx = gStart; gIdx < gEnd; gIdx++) {
+                    const char = graphemes[gIdx];
+
+                    // `breakableFitAdvances[sIdx]` is an array of per-grapheme advance
+                    // widths when the segment has >1 grapheme (multi-character words).
+                    // It is `null` for single-grapheme segments (spaces, punctuation,
+                    // emoji, etc.) — in that case the entire segment width is attributed
+                    // to this single grapheme.
+                    const charWidth = advances != null ? advances[gIdx]! : widths[sIdx]!;
+
+                    chars.push({
+                        char,
+                        x: currentX,
+                        width: charWidth,
+                    });
+                    currentX += charWidth;
+                }
+            }
+
+            return {
+                text: line.text,
+                width: line.width,
+                chars,
+            };
+        });
+
+        return {
+            lines: resultLines,
+            // pretext guarantees height === lineCount * lineHeight (see layout.ts source).
+            totalHeight: height,
+        };
+    }
+}

src/shared/lib/helpers/TextLayoutEngine/TextLayoutEngine.test.ts

@@ -0,0 +1,89 @@
+// @vitest-environment jsdom
+import { clearCache } from '@chenglou/pretext';
+import {
+    beforeEach,
+    describe,
+    expect,
+    it,
+} from 'vitest';
+import { installCanvasMock } from '../__mocks__/canvas';
+import { TextLayoutEngine } from './TextLayoutEngine.svelte';
+
+// Fixed-width mock: every segment is measured as (text.length * 10) px.
+// This is font-independent so we can reason about wrapping precisely.
+const CHAR_WIDTH = 10;
+
+describe('TextLayoutEngine', () => {
+    let engine: TextLayoutEngine;
+
+    beforeEach(() => {
+        // Install mock BEFORE any prepareWithSegments call.
+        // clearMeasurementCaches resets pretext's cached canvas context
+        // and segment metric caches so each test gets a clean slate.
+        installCanvasMock((_font, text) => text.length * CHAR_WIDTH);
+        clearCache();
+        engine = new TextLayoutEngine();
+    });
+
+    it('returns empty result for empty string', () => {
+        const result = engine.layout('', '400 16px "Inter"', 500, 20);
+        expect(result.lines).toHaveLength(0);
+        expect(result.totalHeight).toBe(0);
+    });
+
+    it('returns a single line when text fits within width', () => {
+        // 'ABC' = 3 chars × 10px = 30px, fits in 500px
+        const result = engine.layout('ABC', '400 16px "Inter"', 500, 20);
+        expect(result.lines).toHaveLength(1);
+        expect(result.lines[0].text).toBe('ABC');
+    });
+
+    it('breaks text into multiple lines when it exceeds width', () => {
+        // 'Hello World' — pretext will split at the space.
+        // 'Hello' = 50px, ' ' hangs, 'World' = 50px. Width = 60px forces wrap after 'Hello '.
+        const result = engine.layout('Hello World', '400 16px "Inter"', 60, 20);
+        expect(result.lines.length).toBeGreaterThan(1);
+        // First line must not exceed the container width.
+        expect(result.lines[0].width).toBeLessThanOrEqual(60);
+    });
+
+    it('assigns correct x positions to characters on a single line', () => {
+        // 'ABC': A=10px, B=10px, C=10px; all on one line in 500px container.
+        const result = engine.layout('ABC', '400 16px "Inter"', 500, 20);
+        const chars = result.lines[0].chars;
+
+        expect(chars).toHaveLength(3);
+        expect(chars[0].char).toBe('A');
+        expect(chars[0].x).toBe(0);
+        expect(chars[0].width).toBe(CHAR_WIDTH);
+
+        expect(chars[1].char).toBe('B');
+        expect(chars[1].x).toBe(CHAR_WIDTH);
+        expect(chars[1].width).toBe(CHAR_WIDTH);
+
+        expect(chars[2].char).toBe('C');
+        expect(chars[2].x).toBe(CHAR_WIDTH * 2);
+        expect(chars[2].width).toBe(CHAR_WIDTH);
+    });
+
+    it('x positions are monotonically increasing across a line', () => {
+        const result = engine.layout('ABCDE', '400 16px "Inter"', 500, 20);
+        const chars = result.lines[0].chars;
+        for (let i = 1; i < chars.length; i++) {
+            expect(chars[i].x).toBeGreaterThan(chars[i - 1].x);
+        }
+    });
+
+    it('each line has at least one char', () => {
+        const result = engine.layout('Hello World', '400 16px "Inter"', 60, 20);
+        for (const line of result.lines) {
+            expect(line.chars.length).toBeGreaterThan(0);
+        }
+    });
+
+    it('totalHeight equals lineCount * lineHeight', () => {
+        const lineHeight = 24;
+        const result = engine.layout('Hello World', '400 16px "Inter"', 60, lineHeight);
+        expect(result.totalHeight).toBe(result.lines.length * lineHeight);
+    });
+});

src/shared/lib/helpers/__mocks__/canvas.ts

@@ -0,0 +1,29 @@
+// src/shared/lib/helpers/__mocks__/canvas.ts
+//
+// Call installCanvasMock(fn) before any pretext import to control measureText.
+// The factory receives the current ctx.font string and the text to measure.
+import { vi } from 'vitest';
+
+export type MeasureFactory = (font: string, text: string) => number;
+
+export function installCanvasMock(factory: MeasureFactory): void {
+    let currentFont = '';
+
+    const mockCtx = {
+        get font() {
+            return currentFont;
+        },
+        set font(f: string) {
+            currentFont = f;
+        },
+        measureText: vi.fn((text: string) => ({ width: factory(currentFont, text) })),
+    };
+
+    // HTMLCanvasElement.prototype.getContext is the entry point pretext uses in DOM environments.
+    // OffscreenCanvas takes priority in pretext; jsdom does not define it so DOM path is used.
+    Object.defineProperty(HTMLCanvasElement.prototype, 'getContext', {
+        configurable: true,
+        writable: true,
+        value: vi.fn(() => mockCtx),
+    });
+}

src/shared/lib/helpers/createCharacterComparison/createCharacterComparison.svelte.ts

@@ -1,374 +0,0 @@
-/**
- * Character-by-character font comparison helper
- *
- * Creates utilities for comparing two fonts character by character.
- * Used by the ComparisonView widget to render morphing text effects
- * where characters transition between font A and font B based on
- * slider position.
- *
- * Features:
- * - Responsive text measurement using canvas
- * - Binary search for optimal line breaking
- * - Character proximity calculation for morphing effects
- * - Handles CSS transforms correctly (uses offsetWidth)
- *
- * @example
- * ```svelte
- * <script lang="ts">
- *   import { createCharacterComparison } from '$shared/lib/helpers';
- *
- *   const comparison = createCharacterComparison(
- *       () => text,
- *       () => fontA,
- *       () => fontB,
- *       () => weight,
- *       () => size
- *   );
- *
- *   $: lines = comparison.lines;
- * </script>
- *
- * <canvas bind:this={measureCanvas} hidden></canvas>
- * <div bind:this={container}>
- *   {#each lines as line}
- *     <span>{line.text}</span>
- *   {/each}
- * </div>
- * ```
- */
-
-/**
- * Represents a single line of text with its measured width
- */
-export interface LineData {
-    /** The text content of the line */
-    text: string;
-    /** Maximum width between both fonts in pixels */
-    width: number;
-}
-
-/**
- * Creates a character comparison helper for morphing text effects
- *
- * Measures text in both fonts to determine line breaks and calculates
- * character-level proximity for morphing animations.
- *
- * @param text - Getter for the text to compare
- * @param fontA - Getter for the first font (left/top side)
- * @param fontB - Getter for the second font (right/bottom side)
- * @param weight - Getter for the current font weight
- * @param size - Getter for the controlled font size
- * @returns Character comparison instance with lines and proximity calculations
- *
- * @example
- * ```ts
- * const comparison = createCharacterComparison(
- *     () => $sampleText,
- *     () => $selectedFontA,
- *     () => $selectedFontB,
- *     () => $fontWeight,
- *     () => $fontSize
- * );
- *
- * // Call when DOM is ready
- * comparison.breakIntoLines(container, canvas);
- *
- * // Get character state for morphing
- * const state = comparison.getCharState(5, sliderPosition, lineEl, container);
- * // state.proximity: 0-1 value for opacity/interpolation
- * // state.isPast: true if slider is past this character
- * ```
- */
-export function createCharacterComparison<
-    T extends { name: string; id: string } | undefined = undefined,
->(
-    text: () => string,
-    fontA: () => T,
-    fontB: () => T,
-    weight: () => number,
-    size: () => number,
-) {
-    let lines = $state<LineData[]>([]);
-    let containerWidth = $state(0);
-
-    /**
-     * Type guard to check if a font is defined
-     */
-    function fontDefined<T extends { name: string; id: string }>(font: T | undefined): font is T {
-        return font !== undefined;
-    }
-
-    /**
-     * Measures text width using canvas 2D context
-     *
-     * @param ctx - Canvas rendering context
-     * @param text - Text string to measure
-     * @param fontSize - Font size in pixels
-     * @param fontWeight - Font weight (100-900)
-     * @param fontFamily - Font family name (optional, returns 0 if missing)
-     * @returns Width of text in pixels
-     */
-    function measureText(
-        ctx: CanvasRenderingContext2D,
-        text: string,
-        fontSize: number,
-        fontWeight: number,
-        fontFamily?: string,
-    ): number {
-        if (!fontFamily) return 0;
-        ctx.font = `${fontWeight} ${fontSize}px ${fontFamily}`;
-        return ctx.measureText(text).width;
-    }
-
-    /**
-     * Gets responsive font size based on viewport width
-     *
-     * Matches Tailwind breakpoints used in the component:
-     * - < 640px: 64px
-     * - 640-767px: 80px
-     * - 768-1023px: 96px
-     * - >= 1024px: 112px
-     */
-    function getFontSize() {
-        if (typeof window === 'undefined') {
-            return 64;
-        }
-        return window.innerWidth >= 1024
-            ? 112
-            : window.innerWidth >= 768
-            ? 96
-            : window.innerWidth >= 640
-            ? 80
-            : 64;
-    }
-
-    /**
-     * Breaks text into lines based on container width
-     *
-     * Measures text in BOTH fonts and uses the wider width to prevent
-     * layout shifts. Uses binary search for efficient word breaking.
-     *
-     * @param container - Container element to measure width from
-     * @param measureCanvas - Hidden canvas element for text measurement
-     */
-    function breakIntoLines(
-        container: HTMLElement | undefined,
-        measureCanvas: HTMLCanvasElement | undefined,
-    ) {
-        if (!container || !measureCanvas || !fontA() || !fontB()) {
-            return;
-        }
-
-        // Use offsetWidth to avoid CSS transform scaling issues
-        // getBoundingClientRect() includes transform scale which breaks calculations
-        const width = container.offsetWidth;
-        containerWidth = width;
-
-        const padding = window.innerWidth < 640 ? 48 : 96;
-        const availableWidth = width - padding;
-        const ctx = measureCanvas.getContext('2d');
-        if (!ctx) {
-            return;
-        }
-
-        const controlledFontSize = size();
-        const fontSize = getFontSize();
-        const currentWeight = weight();
-        const words = text().split(' ');
-        const newLines: LineData[] = [];
-        let currentLineWords: string[] = [];
-
-        /**
-         * Adds a line to the output using the wider font's width
-         */
-        function pushLine(words: string[]) {
-            if (words.length === 0 || !fontDefined(fontA()) || !fontDefined(fontB())) {
-                return;
-            }
-            const lineText = words.join(' ');
-            const widthA = measureText(
-                ctx!,
-                lineText,
-                Math.min(fontSize, controlledFontSize),
-                currentWeight,
-                fontA()?.name,
-            );
-            const widthB = measureText(
-                ctx!,
-                lineText,
-                Math.min(fontSize, controlledFontSize),
-                currentWeight,
-                fontB()?.name,
-            );
-            const maxWidth = Math.max(widthA, widthB);
-            newLines.push({ text: lineText, width: maxWidth });
-        }
-
-        for (const word of words) {
-            const testLine = currentLineWords.length > 0
-                ? currentLineWords.join(' ') + ' ' + word
-                : word;
-            // Measure with both fonts - use wider to prevent shifts
-            const widthA = measureText(
-                ctx,
-                testLine,
-                Math.min(fontSize, controlledFontSize),
-                currentWeight,
-                fontA()?.name,
-            );
-            const widthB = measureText(
-                ctx,
-                testLine,
-                Math.min(fontSize, controlledFontSize),
-                currentWeight,
-                fontB()?.name,
-            );
-            const maxWidth = Math.max(widthA, widthB);
-            const isContainerOverflown = maxWidth > availableWidth;
-
-            if (isContainerOverflown) {
-                if (currentLineWords.length > 0) {
-                    pushLine(currentLineWords);
-                    currentLineWords = [];
-                }
-
-                // Check if word alone fits
-                const wordWidthA = measureText(
-                    ctx,
-                    word,
-                    Math.min(fontSize, controlledFontSize),
-                    currentWeight,
-                    fontA()?.name,
-                );
-                const wordWidthB = measureText(
-                    ctx,
-                    word,
-                    Math.min(fontSize, controlledFontSize),
-                    currentWeight,
-                    fontB()?.name,
-                );
-                const wordAloneWidth = Math.max(wordWidthA, wordWidthB);
-
-                if (wordAloneWidth <= availableWidth) {
-                    currentLineWords = [word];
-                } else {
-                    // Word doesn't fit - binary search to find break point
-                    let remainingWord = word;
-                    while (remainingWord.length > 0) {
-                        let low = 1;
-                        let high = remainingWord.length;
-                        let bestBreak = 1;
-
-                        // Binary search for maximum characters that fit
-                        while (low <= high) {
-                            const mid = Math.floor((low + high) / 2);
-                            const testFragment = remainingWord.slice(0, mid);
-
-                            const wA = measureText(
-                                ctx,
-                                testFragment,
-                                fontSize,
-                                currentWeight,
-                                fontA()?.name,
-                            );
-                            const wB = measureText(
-                                ctx,
-                                testFragment,
-                                fontSize,
-                                currentWeight,
-                                fontB()?.name,
-                            );
-
-                            if (Math.max(wA, wB) <= availableWidth) {
-                                bestBreak = mid;
-                                low = mid + 1;
-                            } else {
-                                high = mid - 1;
-                            }
-                        }
-
-                        pushLine([remainingWord.slice(0, bestBreak)]);
-                        remainingWord = remainingWord.slice(bestBreak);
-                    }
-                }
-            } else if (maxWidth > availableWidth && currentLineWords.length > 0) {
-                pushLine(currentLineWords);
-                currentLineWords = [word];
-            } else {
-                currentLineWords.push(word);
-            }
-        }
-
-        if (currentLineWords.length > 0) {
-            pushLine(currentLineWords);
-        }
-        lines = newLines;
-    }
-
-    /**
-     * Calculates character proximity to slider position
-     *
-     * Used for morphing effects - returns how close a character is to
-     * the slider and whether it's on the "past" side.
-     *
-     * @param charIndex - Index of character within its line
-     * @param sliderPos - Slider position (0-100, percent across container)
-     * @param lineElement - The line element containing the character
-     * @param container - The container element for position calculations
-     * @returns Proximity (0-1, 1 = at slider) and isPast (true = right of slider)
-     */
-    function getCharState(
-        charIndex: number,
-        sliderPos: number,
-        lineElement?: HTMLElement,
-        container?: HTMLElement,
-    ) {
-        if (!containerWidth || !container) {
-            return {
-                proximity: 0,
-                isPast: false,
-            };
-        }
-        const charElement = lineElement?.children[charIndex] as HTMLElement;
-
-        if (!charElement) {
-            return { proximity: 0, isPast: false };
-        }
-
-        // Get character bounding box relative to container
-        const charRect = charElement.getBoundingClientRect();
-        const containerRect = container.getBoundingClientRect();
-
-        // Calculate character center as percentage of container width
-        const charCenter = charRect.left + (charRect.width / 2) - containerRect.left;
-        const charGlobalPercent = (charCenter / containerWidth) * 100;
-
-        // Calculate proximity (1.0 = at slider, 0.0 = 5% away)
-        const distance = Math.abs(sliderPos - charGlobalPercent);
-        const range = 5;
-        const proximity = Math.max(0, 1 - distance / range);
-        const isPast = sliderPos > charGlobalPercent;
-
-        return { proximity, isPast };
-    }
-
-    return {
-        /** Reactive array of broken lines */
-        get lines() {
-            return lines;
-        },
-        /** Container width in pixels */
-        get containerWidth() {
-            return containerWidth;
-        },
-        /** Break text into lines based on current container and fonts */
-        breakIntoLines,
-        /** Get character state for morphing calculations */
-        getCharState,
-    };
-}
-
-/**
- * Type representing a character comparison instance
- */
-export type CharacterComparison = ReturnType<typeof createCharacterComparison>;

src/shared/lib/helpers/createCharacterComparison/createCharacterComparison.test.ts

@@ -1,312 +0,0 @@
-import {
-    beforeEach,
-    describe,
-    expect,
-    it,
-    vi,
-} from 'vitest';
-import { createCharacterComparison } from './createCharacterComparison.svelte';
-
-type Font = { name: string; id: string };
-
-const fontA: Font = { name: 'Roboto', id: 'roboto' };
-const fontB: Font = { name: 'Open Sans', id: 'open-sans' };
-
-function createMockCanvas(charWidth = 10): HTMLCanvasElement {
-    return {
-        getContext: () => ({
-            font: '',
-            measureText: (text: string) => ({ width: text.length * charWidth }),
-        }),
-    } as unknown as HTMLCanvasElement;
-}
-
-function createMockContainer(offsetWidth = 500): HTMLElement {
-    return {
-        offsetWidth,
-        getBoundingClientRect: () => ({
-            left: 0,
-            width: offsetWidth,
-            top: 0,
-            right: offsetWidth,
-            bottom: 0,
-            height: 0,
-        }),
-    } as unknown as HTMLElement;
-}
-
-describe('createCharacterComparison', () => {
-    beforeEach(() => {
-        // Mock window.innerWidth for getFontSize and padding calculations
-        Object.defineProperty(globalThis, 'window', {
-            value: { innerWidth: 1024 },
-            writable: true,
-            configurable: true,
-        });
-    });
-
-    describe('Initial State', () => {
-        it('should initialize with empty lines and zero container width', () => {
-            const comparison = createCharacterComparison(
-                () => 'test',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            expect(comparison.lines).toEqual([]);
-            expect(comparison.containerWidth).toBe(0);
-        });
-    });
-
-    describe('breakIntoLines', () => {
-        it('should not break lines when container or canvas is undefined', () => {
-            const comparison = createCharacterComparison(
-                () => 'Hello world',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(undefined, undefined);
-            expect(comparison.lines).toEqual([]);
-
-            comparison.breakIntoLines(createMockContainer(), undefined);
-            expect(comparison.lines).toEqual([]);
-        });
-
-        it('should not break lines when fonts are undefined', () => {
-            const comparison = createCharacterComparison(
-                () => 'Hello world',
-                () => undefined,
-                () => undefined,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(), createMockCanvas());
-            expect(comparison.lines).toEqual([]);
-        });
-
-        it('should produce a single line when text fits within container', () => {
-            // charWidth=10, padding=96 (innerWidth>=640), availableWidth=500-96=404
-            // "Hello" = 5 chars * 10 = 50px, fits easily
-            const comparison = createCharacterComparison(
-                () => 'Hello',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(500), createMockCanvas(10));
-
-            expect(comparison.lines).toHaveLength(1);
-            expect(comparison.lines[0].text).toBe('Hello');
-        });
-
-        it('should break text into multiple lines when it overflows', () => {
-            // charWidth=10, container=200, padding=96, availableWidth=104
-            // "Hello world test" => "Hello" (50px), "Hello world" (110px > 104)
-            // So "Hello" goes on line 1, "world" (50px) fits, "world test" (100px) fits
-            const comparison = createCharacterComparison(
-                () => 'Hello world test',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(200), createMockCanvas(10));
-
-            expect(comparison.lines.length).toBeGreaterThan(1);
-            // All original text should be preserved across lines
-            const reconstructed = comparison.lines.map(l => l.text).join(' ');
-            expect(reconstructed).toBe('Hello world test');
-        });
-
-        it('should update containerWidth after breaking lines', () => {
-            const comparison = createCharacterComparison(
-                () => 'Hi',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(750), createMockCanvas(10));
-
-            expect(comparison.containerWidth).toBe(750);
-        });
-
-        it('should use smaller padding on narrow viewports', () => {
-            Object.defineProperty(globalThis, 'window', {
-                value: { innerWidth: 500 },
-                writable: true,
-                configurable: true,
-            });
-
-            // container=150, padding=48 (innerWidth<640), availableWidth=102
-            // "ABCDEFGHIJ" = 10 chars * 10 = 100px, fits in 102
-            const comparison = createCharacterComparison(
-                () => 'ABCDEFGHIJ',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(150), createMockCanvas(10));
-
-            expect(comparison.lines).toHaveLength(1);
-            expect(comparison.lines[0].text).toBe('ABCDEFGHIJ');
-        });
-
-        it('should break a single long word using binary search', () => {
-            // container=150, padding=96, availableWidth=54
-            // "ABCDEFGHIJ" = 10 chars * 10 = 100px, doesn't fit as single word
-            // Binary search should split it
-            const comparison = createCharacterComparison(
-                () => 'ABCDEFGHIJ',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(150), createMockCanvas(10));
-
-            expect(comparison.lines.length).toBeGreaterThan(1);
-            const reconstructed = comparison.lines.map(l => l.text).join('');
-            expect(reconstructed).toBe('ABCDEFGHIJ');
-        });
-
-        it('should store max width between both fonts for each line', () => {
-            // Use a canvas where measureText returns text.length * charWidth
-            // Both fonts measure the same, so width = text.length * charWidth
-            const comparison = createCharacterComparison(
-                () => 'Hi',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(500), createMockCanvas(10));
-
-            expect(comparison.lines[0].width).toBe(20); // "Hi" = 2 chars * 10
-        });
-    });
-
-    describe('getCharState', () => {
-        it('should return zero proximity and isPast=false when containerWidth is 0', () => {
-            const comparison = createCharacterComparison(
-                () => 'test',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            const state = comparison.getCharState(0, 50, undefined, undefined);
-
-            expect(state.proximity).toBe(0);
-            expect(state.isPast).toBe(false);
-        });
-
-        it('should return zero proximity when charElement is not found', () => {
-            const comparison = createCharacterComparison(
-                () => 'test',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            // First break lines to set containerWidth
-            comparison.breakIntoLines(createMockContainer(500), createMockCanvas(10));
-
-            const lineEl = { children: [] } as unknown as HTMLElement;
-            const container = createMockContainer(500);
-            const state = comparison.getCharState(0, 50, lineEl, container);
-
-            expect(state.proximity).toBe(0);
-            expect(state.isPast).toBe(false);
-        });
-
-        it('should calculate proximity based on distance from slider', () => {
-            const comparison = createCharacterComparison(
-                () => 'test',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(500), createMockCanvas(10));
-
-            // Character centered at 250px in a 500px container = 50%
-            const charEl = {
-                getBoundingClientRect: () => ({ left: 240, width: 20 }),
-            };
-            const lineEl = { children: [charEl] } as unknown as HTMLElement;
-            const container = createMockContainer(500);
-
-            // Slider at 50% => charCenter at 250px => charGlobalPercent = 50%
-            // distance = |50 - 50| = 0, proximity = max(0, 1 - 0/5) = 1
-            const state = comparison.getCharState(0, 50, lineEl, container);
-
-            expect(state.proximity).toBe(1);
-            expect(state.isPast).toBe(false);
-        });
-
-        it('should return isPast=true when slider is past the character', () => {
-            const comparison = createCharacterComparison(
-                () => 'test',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(500), createMockCanvas(10));
-
-            // Character centered at 100px => 20% of 500px
-            const charEl = {
-                getBoundingClientRect: () => ({ left: 90, width: 20 }),
-            };
-            const lineEl = { children: [charEl] } as unknown as HTMLElement;
-            const container = createMockContainer(500);
-
-            // Slider at 80% => past the character at 20%
-            const state = comparison.getCharState(0, 80, lineEl, container);
-
-            expect(state.isPast).toBe(true);
-        });
-
-        it('should return zero proximity when character is far from slider', () => {
-            const comparison = createCharacterComparison(
-                () => 'test',
-                () => fontA,
-                () => fontB,
-                () => 400,
-                () => 48,
-            );
-
-            comparison.breakIntoLines(createMockContainer(500), createMockCanvas(10));
-
-            // Character at 10% of container, slider at 90% => distance = 80%, range = 5%
-            const charEl = {
-                getBoundingClientRect: () => ({ left: 45, width: 10 }),
-            };
-            const lineEl = { children: [charEl] } as unknown as HTMLElement;
-            const container = createMockContainer(500);
-
-            const state = comparison.getCharState(0, 90, lineEl, container);
-
-            expect(state.proximity).toBe(0);
-        });
-    });
-});

src/shared/lib/helpers/createDebouncedState/createDebouncedState.svelte.ts

@@ -32,7 +32,9 @@ export function createDebouncedState<T>(initialValue: T, wait: number = 300) {
     }, wait);
 
     return {
-        /** Current value with immediate updates (for UI binding) */
+        /**
+         * Current value with immediate updates (for UI binding)
+         */
         get immediate() {
             return immediate;
         },
@@ -41,7 +43,9 @@ export function createDebouncedState<T>(initialValue: T, wait: number = 300) {
             // Manually trigger the debounce on write
             updateDebounced(value);
         },
-        /** Current value with debounced updates (for logic/operations) */
+        /**
+         * Current value with debounced updates (for logic/operations)
+         */
         get debounced() {
             return debounced;
         },

src/shared/lib/helpers/createEntityStore/createEntityStore.svelte.ts

@@ -28,7 +28,9 @@ import { SvelteMap } from 'svelte/reactivity';
  * Base entity interface requiring an ID field
  */
 export interface Entity {
-    /** Unique identifier for the entity */
+    /**
+     * Unique identifier for the entity
+     */
     id: string;
 }
 
@@ -39,7 +41,9 @@ export interface Entity {
  * triggers updates when entities are added, removed, or modified.
  */
 export class EntityStore<T extends Entity> {
-    /** Reactive map of entities keyed by ID */
+    /**
+     * Reactive map of entities keyed by ID
+     */
     #entities = new SvelteMap<string, T>();
 
     /**

src/shared/lib/helpers/createFilter/createFilter.svelte.ts

@@ -29,13 +29,21 @@
  * @template TValue - The type of the property value (typically string)
  */
 export interface Property<TValue extends string> {
-    /** Unique identifier for the property */
+    /**
+     * Unique string identifier for the filterable property
+     */
     id: string;
-    /** Human-readable display name */
+    /**
+     * Human-readable label for UI display
+     */
     name: string;
-    /** Underlying value for filtering logic */
+    /**
+     * Underlying machine-readable value used for filtering logic
+     */
     value: TValue;
-    /** Whether the property is currently selected */
+    /**
+     * Current selection status (reactive)
+     */
     selected?: boolean;
 }
 
@@ -45,7 +53,9 @@ export interface Property<TValue extends string> {
  * @template TValue - The type of property values
  */
 export interface FilterModel<TValue extends string> {
-    /** Array of filterable properties */
+    /**
+     * Collection of properties that can be toggled in this filter
+     */
     properties: Property<TValue>[];
 }
 

src/shared/lib/helpers/createPersistentStore/createPersistentStore.test.ts

@@ -1,4 +1,6 @@
-/** @vitest-environment jsdom */
+/**
+ * @vitest-environment jsdom
+ */
 import {
     afterEach,
     beforeEach,

src/shared/lib/helpers/createPerspectiveManager/createPerspectiveManager.svelte.ts

@@ -32,19 +32,33 @@ import { Spring } from 'svelte/motion';
  * Configuration options for perspective effects
  */
 export interface PerspectiveConfig {
-    /** Z-axis translation per level in pixels */
+    /**
+     * Z-axis translation per level in pixels
+     */
     depthStep?: number;
-    /** Scale reduction per level (0-1) */
+    /**
+     * Scale reduction per level (0-1)
+     */
     scaleStep?: number;
-    /** Blur amount per level in pixels */
+    /**
+     * Blur amount per level in pixels
+     */
     blurStep?: number;
-    /** Opacity reduction per level (0-1) */
+    /**
+     * Opacity reduction per level (0-1)
+     */
     opacityStep?: number;
-    /** Parallax movement intensity per level */
+    /**
+     * Parallax movement intensity per level
+     */
     parallaxIntensity?: number;
-    /** Horizontal offset - positive for right, negative for left */
+    /**
+     * Horizontal offset - positive for right, negative for left
+     */
     horizontalOffset?: number;
-    /** Layout mode: 'center' for centered, 'split' for side-by-side */
+    /**
+     * Layout mode: 'center' for centered, 'split' for side-by-side
+     */
     layoutMode?: 'center' | 'split';
 }
 

src/shared/lib/helpers/createResponsiveManager/createResponsiveManager.svelte.ts

@@ -39,15 +39,25 @@
  * Customize to match your design system's breakpoints.
  */
 export interface Breakpoints {
-    /** Mobile devices - default 640px */
+    /**
+     * Mobile devices - default 640px
+     */
     mobile: number;
-    /** Tablet portrait - default 768px */
+    /**
+     * Tablet portrait - default 768px
+     */
     tabletPortrait: number;
-    /** Tablet landscape - default 1024px */
+    /**
+     * Tablet landscape - default 1024px
+     */
     tablet: number;
-    /** Desktop - default 1280px */
+    /**
+     * Desktop - default 1280px
+     */
     desktop: number;
-    /** Large desktop - default 1536px */
+    /**
+     * Large desktop - default 1536px
+     */
     desktopLarge: number;
 }
 
@@ -140,7 +150,9 @@ export function createResponsiveManager(customBreakpoints?: Partial<Breakpoints>
      * @returns Cleanup function to remove listeners
      */
     function init() {
-        if (typeof window === 'undefined') return;
+        if (typeof window === 'undefined') {
+            return;
+        }
 
         const handleResize = () => {
             width = window.innerWidth;
@@ -206,66 +218,108 @@ export function createResponsiveManager(customBreakpoints?: Partial<Breakpoints>
     );
 
     return {
-        /** Viewport width in pixels */
+        /**
+         * Current viewport width in pixels (reactive)
+         */
         get width() {
             return width;
         },
-        /** Viewport height in pixels */
+        /**
+         * Current viewport height in pixels (reactive)
+         */
         get height() {
             return height;
         },
 
-        // Standard breakpoints
+        /**
+         * True if viewport width is below the mobile threshold
+         */
         get isMobile() {
             return isMobile;
         },
+        /**
+         * True if viewport width is between mobile and tablet portrait thresholds
+         */
         get isTabletPortrait() {
             return isTabletPortrait;
         },
+        /**
+         * True if viewport width is between tablet portrait and desktop thresholds
+         */
         get isTablet() {
             return isTablet;
         },
+        /**
+         * True if viewport width is between desktop and large desktop thresholds
+         */
         get isDesktop() {
             return isDesktop;
         },
+        /**
+         * True if viewport width is at or above the large desktop threshold
+         */
         get isDesktopLarge() {
             return isDesktopLarge;
         },
 
-        // Convenience groupings
+        /**
+         * True if viewport width is below the desktop threshold
+         */
         get isMobileOrTablet() {
             return isMobileOrTablet;
         },
+        /**
+         * True if viewport width is at or above the tablet portrait threshold
+         */
         get isTabletOrDesktop() {
             return isTabletOrDesktop;
         },
 
-        // Orientation
+        /**
+         * Current screen orientation (portrait | landscape)
+         */
         get orientation() {
             return orientation;
         },
+        /**
+         * True if screen height is greater than width
+         */
         get isPortrait() {
             return isPortrait;
         },
+        /**
+         * True if screen width is greater than height
+         */
         get isLandscape() {
             return isLandscape;
         },
 
-        // Device capabilities
+        /**
+         * True if the device supports touch interaction
+         */
         get isTouchDevice() {
             return isTouchDevice;
         },
 
-        // Current breakpoint
+        /**
+         * Name of the currently active breakpoint (reactive)
+         */
         get currentBreakpoint() {
             return currentBreakpoint;
         },
 
-        // Methods
+        /**
+         * Initialization function to start event listeners
+         */
         init,
+        /**
+         * Helper to check for custom width ranges
+         */
         matches,
 
-        // Breakpoint values (for custom logic)
+        /**
+         * Underlying breakpoint pixel values
+         */
         breakpoints,
     };
 }

src/shared/lib/helpers/createTypographyControl/createTypographyControl.svelte.ts

@@ -34,13 +34,21 @@ import {
  * Defines the bounds and stepping behavior for a control
  */
 export interface ControlDataModel {
-    /** Current numeric value */
+    /**
+     * Initial or current numeric value
+     */
     value: number;
-    /** Minimum allowed value (inclusive) */
+    /**
+     * Lower inclusive bound
+     */
     min: number;
-    /** Maximum allowed value (inclusive) */
+    /**
+     * Upper inclusive bound
+     */
     max: number;
-    /** Step size for increment/decrement operations */
+    /**
+     * Precision for increment/decrement operations
+     */
     step: number;
 }
 
@@ -50,13 +58,21 @@ export interface ControlDataModel {
  * @template T - Type for the control identifier
  */
 export interface ControlModel<T extends string = string> extends ControlDataModel {
-    /** Unique identifier for the control */
+    /**
+     * Unique string identifier for the control
+     */
     id: T;
-    /** ARIA label for the increase button */
+    /**
+     * Label used by screen readers for the increase button
+     */
     increaseLabel?: string;
-    /** ARIA label for the decrease button */
+    /**
+     * Label used by screen readers for the decrease button
+     */
     decreaseLabel?: string;
-    /** ARIA label for the control area */
+    /**
+     * Overall label describing the control's purpose
+     */
     controlLabel?: string;
 }
 
@@ -109,8 +125,7 @@ export function createTypographyControl<T extends ControlDataModel>(
 
     return {
         /**
-         * Current control value (getter/setter)
-         * Setting automatically clamps to bounds and rounds to step precision
+         * Clamped and rounded control value (reactive)
          */
         get value() {
             return value;
@@ -122,27 +137,37 @@ export function createTypographyControl<T extends ControlDataModel>(
             }
         },
 
-        /** Maximum allowed value */
+        /**
+         * Upper limit for the control value
+         */
         get max() {
             return max;
         },
 
-        /** Minimum allowed value */
+        /**
+         * Lower limit for the control value
+         */
         get min() {
             return min;
         },
 
-        /** Step increment size */
+        /**
+         * Configured step increment
+         */
         get step() {
             return step;
         },
 
-        /** Whether the value is at or exceeds the maximum */
+        /**
+         * True if current value is equal to or greater than max
+         */
         get isAtMax() {
             return isAtMax;
         },
 
-        /** Whether the value is at or below the minimum */
+        /**
+         * True if current value is equal to or less than min
+         */
         get isAtMin() {
             return isAtMin;
         },

src/shared/lib/helpers/createVirtualizer/createVirtualizer.svelte.ts

@@ -45,14 +45,27 @@ export interface VirtualItem {
  * Options are reactive - pass them through a function getter to enable updates.
  */
 export interface VirtualizerOptions {
-    /** Total number of items in the data array */
+    /**
+     * Total number of items in the underlying data array
+     */
     count: number;
     /**
      * Function to estimate the size of an item at a given index.
      * Used for initial layout before actual measurements are available.
+     *
+     * Called inside a `$derived.by` block. Any `$state` or `$derived` value
+     * read within this function is automatically tracked as a dependency —
+     * when those values change, `offsets` and `totalSize` recompute instantly.
+     *
+     * For font preview rows, pass a closure that reads
+     * `appliedFontsManager.statuses` so the virtualizer recalculates heights
+     * as fonts finish loading, eliminating the DOM-measurement snap on load.
      */
     estimateSize: (index: number) => number;
-    /** Number of extra items to render outside viewport for smoother scrolling (default: 5) */
+    /**
+     * Number of extra items to render outside viewport for smoother scrolling
+     * @default 5
+     */
     overscan?: number;
     /**
      * Function to get the key of an item at a given index.
@@ -71,6 +84,18 @@ export interface VirtualizerOptions {
     useWindowScroll?: boolean;
 }
 
+/**
+ * A height resolver for a single virtual-list row.
+ *
+ * When this function reads reactive state (e.g. `SvelteMap.get()`), calling
+ * it inside a `$derived.by` block automatically subscribes to that state.
+ * Return `fallbackHeight` whenever the true height is not yet known.
+ *
+ * @param rowIndex  Zero-based row index within the data array.
+ * @returns         Row height in pixels, excluding the list gap.
+ */
+export type ItemSizeResolver = (rowIndex: number) => number;
+
 /**
  * Creates a reactive virtualizer for efficiently rendering large lists by only rendering visible items.
  *
@@ -150,7 +175,9 @@ export function createVirtualizer<T>(
         const { count, data } = options;
         // Implicit dependency
         const v = _version;
-        if (count === 0 || containerHeight === 0 || !data) return [];
+        if (count === 0 || containerHeight === 0 || !data) {
+            return [];
+        }
 
         const overscan = options.overscan ?? 5;
 
@@ -239,7 +266,9 @@ export function createVirtualizer<T>(
             containerHeight = window.innerHeight;
 
             const handleScroll = () => {
-                if (rafId !== null) return;
+                if (rafId !== null) {
+                    return;
+                }
 
                 rafId = requestAnimationFrame(() => {
                     // Get current position of element relative to viewport
@@ -298,7 +327,9 @@ export function createVirtualizer<T>(
             };
 
             const resizeObserver = new ResizeObserver(([entry]) => {
-                if (entry) containerHeight = entry.contentRect.height;
+                if (entry) {
+                    containerHeight = entry.contentRect.height;
+                }
             });
 
             node.addEventListener('scroll', handleScroll, { passive: true });
@@ -398,7 +429,9 @@ export function createVirtualizer<T>(
      * ```
      */
     function scrollToIndex(index: number, align: 'start' | 'center' | 'end' | 'auto' = 'auto') {
-        if (!elementRef || index < 0 || index >= options.count) return;
+        if (!elementRef || index < 0 || index >= options.count) {
+            return;
+        }
 
         const itemStart = offsets[index];
         const itemSize = measuredSizes[index] ?? options.estimateSize(index);
@@ -406,16 +439,24 @@ export function createVirtualizer<T>(
         const { useWindowScroll } = optionsGetter();
 
         if (useWindowScroll) {
-            if (align === 'center') target = itemStart - window.innerHeight / 2 + itemSize / 2;
-            if (align === 'end') target = itemStart - window.innerHeight + itemSize;
+            if (align === 'center') {
+                target = itemStart - window.innerHeight / 2 + itemSize / 2;
+            }
+            if (align === 'end') {
+                target = itemStart - window.innerHeight + itemSize;
+            }
 
             // Add container offset to target to get absolute document position
             const absoluteTarget = target + elementOffsetTop;
 
             window.scrollTo({ top: absoluteTarget, behavior: 'smooth' });
         } else {
-            if (align === 'center') target = itemStart - containerHeight / 2 + itemSize / 2;
-            if (align === 'end') target = itemStart - containerHeight + itemSize;
+            if (align === 'center') {
+                target = itemStart - containerHeight / 2 + itemSize / 2;
+            }
+            if (align === 'end') {
+                target = itemStart - containerHeight + itemSize;
+            }
 
             elementRef.scrollTo({ top: target, behavior: 'smooth' });
         }
@@ -444,27 +485,45 @@ export function createVirtualizer<T>(
     }
 
     return {
+        /**
+         * Current vertical scroll position in pixels (reactive)
+         */
         get scrollOffset() {
             return scrollOffset;
         },
+        /**
+         * Measured height of the visible container area (reactive)
+         */
         get containerHeight() {
             return containerHeight;
         },
-        /** Computed array of visible items to render (reactive) */
+        /**
+         * Computed array of visible items to render (reactive)
+         */
         get items() {
             return items;
         },
-        /** Total height of all items in pixels (reactive) */
+        /**
+         * Total height of all items in pixels (reactive)
+         */
         get totalSize() {
             return totalSize;
         },
-        /** Svelte action for the scrollable container element */
+        /**
+         * Svelte action for the scrollable container element
+         */
         container,
-        /** Svelte action for measuring individual item elements */
+        /**
+         * Svelte action for measuring individual item elements
+         */
         measureElement,
-        /** Programmatic scroll method to scroll to a specific item */
+        /**
+         * Programmatic scroll method to scroll to a specific item
+         */
         scrollToIndex,
-        /** Programmatic scroll method to scroll to a specific pixel offset */
+        /**
+         * Programmatic scroll method to scroll to a specific pixel offset
+         */
         scrollToOffset,
     };
 }

src/shared/lib/helpers/createVirtualizer/createVirtualizer.test.ts

@@ -1,4 +1,6 @@
-/** @vitest-environment jsdom */
+/**
+ * @vitest-environment jsdom
+ */
 import {
     afterEach,
     describe,

src/shared/lib/helpers/index.ts

@@ -22,53 +22,178 @@
  * ```
  */
 
+/**
+ * Filter management
+ */
 export {
+    /**
+     * Reactive filter factory
+     */
     createFilter,
+    /**
+     * Filter instance type
+     */
     type Filter,
+    /**
+     * Initial state model
+     */
     type FilterModel,
+    /**
+     * Filterable property definition
+     */
     type Property,
 } from './createFilter/createFilter.svelte';
 
+/**
+ * Bounded numeric controls
+ */
 export {
+    /**
+     * Base numeric configuration
+     */
     type ControlDataModel,
+    /**
+     * Extended model with labels
+     */
     type ControlModel,
+    /**
+     * Reactive control factory
+     */
     createTypographyControl,
+    /**
+     * Control instance type
+     */
     type TypographyControl,
 } from './createTypographyControl/createTypographyControl.svelte';
 
+/**
+ * List virtualization
+ */
 export {
+    /**
+     * Reactive virtualizer factory
+     */
     createVirtualizer,
+    /**
+     * Rendered item layout data
+     */
     type VirtualItem,
+    /**
+     * Virtualizer instance type
+     */
     type Virtualizer,
+    /**
+     * Configuration options
+     */
     type VirtualizerOptions,
 } from './createVirtualizer/createVirtualizer.svelte';
 
-export { createDebouncedState } from './createDebouncedState/createDebouncedState.svelte';
-
+/**
+ * UI State
+ */
 export {
+    /**
+     * Immediate/debounced state factory
+     */
+    createDebouncedState,
+} from './createDebouncedState/createDebouncedState.svelte';
+
+/**
+ * Entity collections
+ */
+export {
+    /**
+     * Reactive entity store factory
+     */
     createEntityStore,
+    /**
+     * Base entity requirement
+     */
     type Entity,
+    /**
+     * Entity store instance type
+     */
     type EntityStore,
 } from './createEntityStore/createEntityStore.svelte';
 
+/**
+ * Comparison logic
+ */
 export {
-    type CharacterComparison,
-    createCharacterComparison,
-    type LineData,
-} from './createCharacterComparison/createCharacterComparison.svelte';
+    /**
+     * Character-by-character comparison utility
+     */
+    CharacterComparisonEngine,
+    /**
+     * Single line of comparison results
+     */
+    type ComparisonLine,
+    /**
+     * Full comparison output
+     */
+    type ComparisonResult,
+} from './CharacterComparisonEngine/CharacterComparisonEngine.svelte';
 
+/**
+ * Text layout
+ */
 export {
+    /**
+     * Single line layout information
+     */
+    type LayoutLine as TextLayoutLine,
+    /**
+     * Full multi-line layout information
+     */
+    type LayoutResult as TextLayoutResult,
+    /**
+     * High-level text measurement engine
+     */
+    TextLayoutEngine,
+} from './TextLayoutEngine/TextLayoutEngine.svelte';
+
+/**
+ * Persistence
+ */
+export {
+    /**
+     * LocalStorage-backed reactive store factory
+     */
     createPersistentStore,
+    /**
+     * Persistent store instance type
+     */
     type PersistentStore,
 } from './createPersistentStore/createPersistentStore.svelte';
 
+/**
+ * Responsive design
+ */
 export {
+    /**
+     * Breakpoint tracking factory
+     */
     createResponsiveManager,
+    /**
+     * Responsive manager instance type
+     */
     type ResponsiveManager,
+    /**
+     * Singleton manager for global usage
+     */
     responsiveManager,
 } from './createResponsiveManager/createResponsiveManager.svelte';
 
+/**
+ * 3D Perspectives
+ */
 export {
+    /**
+     * Motion-aware perspective factory
+     */
     createPerspectiveManager,
+    /**
+     * Perspective manager instance type
+     */
     type PerspectiveManager,
 } from './createPerspectiveManager/createPerspectiveManager.svelte';

src/shared/lib/index.ts

@@ -5,10 +5,11 @@
  */
 
 export {
-    type CharacterComparison,
+    CharacterComparisonEngine,
+    type ComparisonLine,
+    type ComparisonResult,
     type ControlDataModel,
     type ControlModel,
-    createCharacterComparison,
     createDebouncedState,
     createEntityStore,
     createFilter,
@@ -21,12 +22,14 @@ export {
     type EntityStore,
     type Filter,
     type FilterModel,
-    type LineData,
     type PersistentStore,
     type PerspectiveManager,
     type Property,
     type ResponsiveManager,
     responsiveManager,
+    TextLayoutEngine,
+    type TextLayoutLine,
+    type TextLayoutResult,
     type TypographyControl,
     type VirtualItem,
     type Virtualizer,