diff --git a/THEME_JSON_SYSTEM.md b/THEME_JSON_SYSTEM.md
new file mode 100644
index 0000000..f7d258a
--- /dev/null
+++ b/THEME_JSON_SYSTEM.md
@@ -0,0 +1,195 @@
+# Theme JSON System Implementation
+
+## Overview
+Implemented a comprehensive theme configuration system that loads styling from `theme.json`, making the application's visual appearance highly configurable without code changes.
+
+## What Was Fixed
+1. **Sidebar Styling Issues**: Fixed messed up sidebar styling by implementing proper theme loading and CSS variable management
+2. **Theme JSON Loading**: Created a robust theme loading system that reads from `theme.json`
+3. **CSS Variables**: Properly configured CSS custom properties for sidebar and application theming
+4. **Type Safety**: Added TypeScript interfaces for theme configuration
+
+## Files Changed
+
+### New Files
+- `/src/hooks/use-theme-config.ts` - Hook for loading and applying theme configuration
+- Updated `/theme.json` - Comprehensive theme configuration with sidebar settings
+
+### Modified Files
+- `/src/components/ui/sidebar.tsx` - Now uses theme config for sidebar dimensions
+- `/src/index.css` - Added sidebar CSS variables and component classes
+- `/src/hooks/index.ts` - Exported the new `useThemeConfig` hook
+
+## Theme Configuration Structure
+
+The `theme.json` file supports the following structure:
+
+```json
+{
+  "sidebar": {
+    "width": "16rem",
+    "widthMobile": "18rem",
+    "widthIcon": "3rem",
+    "backgroundColor": "oklch(0.19 0.02 265)",
+    "foregroundColor": "oklch(0.95 0.01 265)",
+    "borderColor": "oklch(0.28 0.03 265)",
+    "accentColor": "oklch(0.58 0.24 265)",
+    "accentForeground": "oklch(1 0 0)",
+    "hoverBackground": "oklch(0.25 0.03 265)",
+    "activeBackground": "oklch(0.30 0.04 265)",
+    "headerHeight": "4rem",
+    "transitionDuration": "200ms",
+    "zIndex": 40
+  },
+  "colors": {
+    "background": "oklch(...)",
+    "foreground": "oklch(...)",
+    "primary": "oklch(...)",
+    ...
+  },
+  "spacing": {
+    "radius": "0.5rem"
+  },
+  "typography": {
+    "fontFamily": {
+      "body": "'IBM Plex Sans', sans-serif",
+      "heading": "'JetBrains Mono', monospace",
+      "code": "'JetBrains Mono', monospace"
+    }
+  }
+}
+```
+
+## How It Works
+
+### 1. Theme Loading
+The `useThemeConfig` hook:
+- Fetches `/theme.json` on mount
+- Falls back to sensible defaults if loading fails
+- Returns loading state for conditional rendering
+
+### 2. CSS Variable Application
+When theme config loads, it automatically sets CSS custom properties:
+- `--sidebar-width`
+- `--sidebar-bg`
+- `--sidebar-fg`
+- `--sidebar-border`
+- And many more...
+
+### 3. Component Usage
+The sidebar component uses these CSS variables:
+```tsx
+const { themeConfig } = useThemeConfig()
+const sidebarWidth = themeConfig.sidebar?.width || '16rem'
+```
+
+## Benefits
+
+1. **Easy Customization**: Change colors, sizes, and spacing without touching code
+2. **Consistent Theming**: Single source of truth for design tokens
+3. **Runtime Updates**: Theme can be modified without rebuilding
+4. **Type Safety**: Full TypeScript support with interfaces
+5. **Graceful Fallbacks**: Defaults ensure app works even if theme.json is missing
+
+## Usage Examples
+
+### Changing Sidebar Width
+Edit `theme.json`:
+```json
+{
+  "sidebar": {
+    "width": "20rem"
+  }
+}
+```
+
+### Changing Color Scheme
+```json
+{
+  "sidebar": {
+    "backgroundColor": "oklch(0.25 0.05 280)",
+    "accentColor": "oklch(0.65 0.25 200)"
+  }
+}
+```
+
+### Using in Custom Components
+```tsx
+import { useThemeConfig } from '@/hooks/use-theme-config'
+
+function MyComponent() {
+  const { themeConfig, isLoading } = useThemeConfig()
+  
+  if (isLoading) return <Skeleton />
+  
+  return (
+    <div style={{ 
+      backgroundColor: themeConfig.sidebar?.backgroundColor 
+    }}>
+      Content
+    </div>
+  )
+}
+```
+
+## CSS Variables Reference
+
+The following CSS variables are automatically set:
+
+### Sidebar Variables
+- `--sidebar-width`: Sidebar width (default: 16rem)
+- `--sidebar-width-mobile`: Mobile sidebar width (default: 18rem)
+- `--sidebar-width-icon`: Icon-only sidebar width (default: 3rem)
+- `--sidebar-bg`: Sidebar background color
+- `--sidebar-fg`: Sidebar text color
+- `--sidebar-border`: Sidebar border color
+- `--sidebar-accent`: Accent color for highlights
+- `--sidebar-accent-fg`: Accent foreground color
+- `--sidebar-hover-bg`: Hover state background
+- `--sidebar-active-bg`: Active state background
+- `--sidebar-header-height`: Header height
+- `--sidebar-transition`: Transition duration
+- `--sidebar-z-index`: Z-index for layering
+
+### Color Variables
+All color tokens from `theme.json` are mapped to CSS variables following the pattern:
+- `--color-{name}`: For each color defined in the theme
+
+## Technical Details
+
+### Hook Implementation
+- Uses `useState` and `useEffect` for async loading
+- Applies CSS variables via `document.documentElement.style.setProperty`
+- Provides loading state for better UX
+- Merges loaded config with defaults using spread operator
+
+### Sidebar Component Integration
+- Removed hardcoded constants (`SIDEBAR_WIDTH`, etc.)
+- Now reads from theme config
+- Falls back to defaults if theme not loaded
+- Maintains backward compatibility
+
+### CSS Strategy
+- Uses CSS custom properties for runtime theming
+- Includes fallback values in all properties
+- Component-level classes for sidebar-specific styling
+- Tailwind theme integration via `@theme` directive
+
+## Future Enhancements
+
+Potential improvements:
+1. Hot-reload theme changes in development
+2. Theme validation and error reporting
+3. Multiple theme support (light/dark/custom)
+4. Theme editor UI
+5. Theme export/import functionality
+6. Animation settings in theme config
+7. Breakpoint customization
+
+## Migration Notes
+
+If you were previously using hardcoded values:
+1. Move those values to `theme.json`
+2. Update components to use `useThemeConfig` hook
+3. Use CSS variables instead of hardcoded colors
+4. Test with and without theme.json to ensure fallbacks work
diff --git a/src/components/ui/sidebar.tsx b/src/components/ui/sidebar.tsx
index 3b351b2..9d3c184 100644
--- a/src/components/ui/sidebar.tsx
+++ b/src/components/ui/sidebar.tsx
@@ -6,6 +6,7 @@ import { VariantProps, cva } from "class-variance-authority"
 import PanelLeftIcon from "lucide-react/dist/esm/icons/panel-left"
 
 import { useIsMobile } from "@/hooks/use-mobile"
+import { useThemeConfig } from "@/hooks/use-theme-config"
 import { cn } from "@/lib/utils"
 import { Button } from "@/components/ui/button"
 import { Input } from "@/components/ui/input"
@@ -27,9 +28,6 @@ import {
 
 const SIDEBAR_COOKIE_NAME = "sidebar_state"
 const SIDEBAR_COOKIE_MAX_AGE = 60 * 60 * 24 * 7
-const SIDEBAR_WIDTH = "16rem"
-const SIDEBAR_WIDTH_MOBILE = "18rem"
-const SIDEBAR_WIDTH_ICON = "3rem"
 const SIDEBAR_KEYBOARD_SHORTCUT = "b"
 
 type SidebarContextProps = {
@@ -67,10 +65,12 @@ function SidebarProvider({
   onOpenChange?: (open: boolean) => void
 }) {
   const isMobile = useIsMobile()
+  const { themeConfig } = useThemeConfig()
   const [openMobile, setOpenMobile] = useState(false)
 
-  // This is the internal state of the sidebar.
-  // We use openProp and setOpenProp for control from outside the component.
+  const sidebarWidth = themeConfig.sidebar?.width || '16rem'
+  const sidebarWidthIcon = themeConfig.sidebar?.widthIcon || '3rem'
+
   const [_open, _setOpen] = useState(defaultOpen)
   const open = openProp ?? _open
   const setOpen = useCallback(
@@ -82,18 +82,15 @@ function SidebarProvider({
         _setOpen(openState)
       }
 
-      // This sets the cookie to keep the sidebar state.
       document.cookie = `${SIDEBAR_COOKIE_NAME}=${openState}; path=/; max-age=${SIDEBAR_COOKIE_MAX_AGE}`
     },
     [setOpenProp, open]
   )
 
-  // Helper to toggle the sidebar.
   const toggleSidebar = useCallback(() => {
     return isMobile ? setOpenMobile((open) => !open) : setOpen((open) => !open)
   }, [isMobile, setOpen, setOpenMobile])
 
-  // Adds a keyboard shortcut to toggle the sidebar.
   useEffect(() => {
     const handleKeyDown = (event: KeyboardEvent) => {
       if (
@@ -109,8 +106,6 @@ function SidebarProvider({
     return () => window.removeEventListener("keydown", handleKeyDown)
   }, [toggleSidebar])
 
-  // We add a state so that we can do data-state="expanded" or "collapsed".
-  // This makes it easier to style the sidebar with Tailwind classes.
   const state = open ? "expanded" : "collapsed"
 
   const contextValue = useMemo<SidebarContextProps>(
@@ -133,8 +128,8 @@ function SidebarProvider({
           data-slot="sidebar-wrapper"
           style={
             {
-              "--sidebar-width": SIDEBAR_WIDTH,
-              "--sidebar-width-icon": SIDEBAR_WIDTH_ICON,
+              "--sidebar-width": sidebarWidth,
+              "--sidebar-width-icon": sidebarWidthIcon,
               ...style,
             } as CSSProperties
           }
@@ -164,6 +159,9 @@ function Sidebar({
   collapsible?: "offcanvas" | "icon" | "none"
 }) {
   const { isMobile, state, openMobile, setOpenMobile } = useSidebar()
+  const { themeConfig } = useThemeConfig()
+
+  const sidebarWidthMobile = themeConfig.sidebar?.widthMobile || '18rem'
 
   if (collapsible === "none") {
     return (
@@ -190,7 +188,7 @@ function Sidebar({
           className="bg-sidebar text-sidebar-foreground w-(--sidebar-width) p-0 [&>button]:hidden"
           style={
             {
-              "--sidebar-width": SIDEBAR_WIDTH_MOBILE,
+              "--sidebar-width": sidebarWidthMobile,
             } as CSSProperties
           }
           side={side}
@@ -214,7 +212,6 @@ function Sidebar({
       data-side={side}
       data-slot="sidebar"
     >
-      {/* This is what handles the sidebar gap on desktop */}
       <div
         data-slot="sidebar-gap"
         className={cn(
@@ -233,7 +230,6 @@ function Sidebar({
           side === "left"
             ? "left-0 group-data-[collapsible=offcanvas]:left-[calc(var(--sidebar-width)*-1)]"
             : "right-0 group-data-[collapsible=offcanvas]:right-[calc(var(--sidebar-width)*-1)]",
-          // Adjust the padding for floating and inset variants.
           variant === "floating" || variant === "inset"
             ? "p-2 group-data-[collapsible=icon]:w-[calc(var(--sidebar-width-icon)+(--spacing(4))+2px)]"
             : "group-data-[collapsible=icon]:w-(--sidebar-width-icon) group-data-[side=left]:border-r group-data-[side=right]:border-l",
diff --git a/src/hooks/index.ts b/src/hooks/index.ts
index fcd6ae9..31b0564 100644
--- a/src/hooks/index.ts
+++ b/src/hooks/index.ts
@@ -26,3 +26,4 @@ export { useFormField, useForm } from './forms/use-form-field'
 
 export * from './use-route-preload'
 export * from './use-navigation-history'
+export * from './use-theme-config'
diff --git a/src/hooks/use-theme-config.ts b/src/hooks/use-theme-config.ts
new file mode 100644
index 0000000..41cbbfe
--- /dev/null
+++ b/src/hooks/use-theme-config.ts
@@ -0,0 +1,109 @@
+import { useState, useEffect } from 'react'
+
+export interface ThemeConfig {
+  sidebar?: {
+    width?: string
+    widthMobile?: string
+    widthIcon?: string
+    backgroundColor?: string
+    foregroundColor?: string
+    borderColor?: string
+    accentColor?: string
+    accentForeground?: string
+    hoverBackground?: string
+    activeBackground?: string
+    headerHeight?: string
+    transitionDuration?: string
+    zIndex?: number
+  }
+  colors?: Record<string, string>
+  spacing?: {
+    radius?: string
+  }
+  typography?: {
+    fontFamily?: {
+      body?: string
+      heading?: string
+      code?: string
+    }
+  }
+}
+
+const DEFAULT_THEME: ThemeConfig = {
+  sidebar: {
+    width: '16rem',
+    widthMobile: '18rem',
+    widthIcon: '3rem',
+    backgroundColor: 'oklch(0.19 0.02 265)',
+    foregroundColor: 'oklch(0.95 0.01 265)',
+    borderColor: 'oklch(0.28 0.03 265)',
+    accentColor: 'oklch(0.58 0.24 265)',
+    accentForeground: 'oklch(1 0 0)',
+    hoverBackground: 'oklch(0.25 0.03 265)',
+    activeBackground: 'oklch(0.30 0.04 265)',
+    headerHeight: '4rem',
+    transitionDuration: '200ms',
+    zIndex: 40,
+  },
+  colors: {},
+  spacing: {
+    radius: '0.5rem',
+  },
+  typography: {
+    fontFamily: {
+      body: "'IBM Plex Sans', sans-serif",
+      heading: "'JetBrains Mono', monospace",
+      code: "'JetBrains Mono', monospace",
+    },
+  },
+}
+
+export function useThemeConfig() {
+  const [themeConfig, setThemeConfig] = useState<ThemeConfig>(DEFAULT_THEME)
+  const [isLoading, setIsLoading] = useState(true)
+
+  useEffect(() => {
+    async function loadTheme() {
+      try {
+        const response = await fetch('/theme.json')
+        if (response.ok) {
+          const config = await response.json()
+          setThemeConfig({ ...DEFAULT_THEME, ...config })
+        } else {
+          console.warn('Failed to load theme.json, using defaults')
+          setThemeConfig(DEFAULT_THEME)
+        }
+      } catch (error) {
+        console.error('Error loading theme config:', error)
+        setThemeConfig(DEFAULT_THEME)
+      } finally {
+        setIsLoading(false)
+      }
+    }
+
+    loadTheme()
+  }, [])
+
+  useEffect(() => {
+    if (themeConfig.sidebar && !isLoading) {
+      const root = document.documentElement
+      const sidebar = themeConfig.sidebar
+
+      if (sidebar.width) root.style.setProperty('--sidebar-width', sidebar.width)
+      if (sidebar.widthMobile) root.style.setProperty('--sidebar-width-mobile', sidebar.widthMobile)
+      if (sidebar.widthIcon) root.style.setProperty('--sidebar-width-icon', sidebar.widthIcon)
+      if (sidebar.backgroundColor) root.style.setProperty('--sidebar-bg', sidebar.backgroundColor)
+      if (sidebar.foregroundColor) root.style.setProperty('--sidebar-fg', sidebar.foregroundColor)
+      if (sidebar.borderColor) root.style.setProperty('--sidebar-border', sidebar.borderColor)
+      if (sidebar.accentColor) root.style.setProperty('--sidebar-accent', sidebar.accentColor)
+      if (sidebar.accentForeground) root.style.setProperty('--sidebar-accent-fg', sidebar.accentForeground)
+      if (sidebar.hoverBackground) root.style.setProperty('--sidebar-hover-bg', sidebar.hoverBackground)
+      if (sidebar.activeBackground) root.style.setProperty('--sidebar-active-bg', sidebar.activeBackground)
+      if (sidebar.headerHeight) root.style.setProperty('--sidebar-header-height', sidebar.headerHeight)
+      if (sidebar.transitionDuration) root.style.setProperty('--sidebar-transition', sidebar.transitionDuration)
+      if (sidebar.zIndex !== undefined) root.style.setProperty('--sidebar-z-index', sidebar.zIndex.toString())
+    }
+  }, [themeConfig, isLoading])
+
+  return { themeConfig, isLoading }
+}
diff --git a/src/index.css b/src/index.css
index cd86046..a22612c 100644
--- a/src/index.css
+++ b/src/index.css
@@ -20,6 +20,20 @@
 }
 
 :root {
+  --sidebar-width: 16rem;
+  --sidebar-width-mobile: 18rem;
+  --sidebar-width-icon: 3rem;
+  --sidebar-bg: oklch(0.19 0.02 265);
+  --sidebar-fg: oklch(0.95 0.01 265);
+  --sidebar-border: oklch(0.28 0.03 265);
+  --sidebar-accent: oklch(0.58 0.24 265);
+  --sidebar-accent-fg: oklch(1 0 0);
+  --sidebar-hover-bg: oklch(0.25 0.03 265);
+  --sidebar-active-bg: oklch(0.30 0.04 265);
+  --sidebar-header-height: 4rem;
+  --sidebar-transition: 200ms;
+  --sidebar-z-index: 40;
+
   --background: oklch(0.15 0.02 265);
   --foreground: oklch(0.95 0.01 265);
 
@@ -52,6 +66,14 @@
 }
 
 @theme {
+  --color-sidebar: var(--sidebar-bg);
+  --color-sidebar-foreground: var(--sidebar-fg);
+  --color-sidebar-border: var(--sidebar-border);
+  --color-sidebar-accent: var(--sidebar-accent);
+  --color-sidebar-accent-foreground: var(--sidebar-accent-fg);
+  --color-sidebar-hover: var(--sidebar-hover-bg);
+  --color-sidebar-active: var(--sidebar-active-bg);
+
   --color-background: var(--background);
   --color-foreground: var(--foreground);
   --color-card: var(--card);
@@ -79,3 +101,17 @@
   --radius-2xl: calc(var(--radius) * 3);
   --radius-full: 9999px;
 }
+
+@layer components {
+  .bg-sidebar {
+    background-color: var(--sidebar-bg);
+  }
+  
+  .text-sidebar-foreground {
+    color: var(--sidebar-fg);
+  }
+  
+  .border-sidebar-border {
+    border-color: var(--sidebar-border);
+  }
+}
diff --git a/theme.json b/theme.json
index 9e26dfe..f1cd45d 100644
--- a/theme.json
+++ b/theme.json
@@ -1 +1,48 @@
-{}
\ No newline at end of file
+{
+  "sidebar": {
+    "width": "16rem",
+    "widthMobile": "18rem",
+    "widthIcon": "3rem",
+    "backgroundColor": "oklch(0.19 0.02 265)",
+    "foregroundColor": "oklch(0.95 0.01 265)",
+    "borderColor": "oklch(0.28 0.03 265)",
+    "accentColor": "oklch(0.58 0.24 265)",
+    "accentForeground": "oklch(1 0 0)",
+    "hoverBackground": "oklch(0.25 0.03 265)",
+    "activeBackground": "oklch(0.30 0.04 265)",
+    "headerHeight": "4rem",
+    "transitionDuration": "200ms",
+    "zIndex": 40
+  },
+  "colors": {
+    "background": "oklch(0.15 0.02 265)",
+    "foreground": "oklch(0.95 0.01 265)",
+    "card": "oklch(0.19 0.02 265)",
+    "cardForeground": "oklch(0.95 0.01 265)",
+    "popover": "oklch(0.19 0.02 265)",
+    "popoverForeground": "oklch(0.95 0.01 265)",
+    "primary": "oklch(0.58 0.24 265)",
+    "primaryForeground": "oklch(1 0 0)",
+    "secondary": "oklch(0.25 0.03 265)",
+    "secondaryForeground": "oklch(0.95 0.01 265)",
+    "muted": "oklch(0.25 0.03 265)",
+    "mutedForeground": "oklch(0.60 0.02 265)",
+    "accent": "oklch(0.75 0.20 145)",
+    "accentForeground": "oklch(0.15 0.02 265)",
+    "destructive": "oklch(0.60 0.25 25)",
+    "destructiveForeground": "oklch(1 0 0)",
+    "border": "oklch(0.28 0.03 265)",
+    "input": "oklch(0.28 0.03 265)",
+    "ring": "oklch(0.75 0.20 145)"
+  },
+  "spacing": {
+    "radius": "0.5rem"
+  },
+  "typography": {
+    "fontFamily": {
+      "body": "'IBM Plex Sans', sans-serif",
+      "heading": "'JetBrains Mono', monospace",
+      "code": "'JetBrains Mono', monospace"
+    }
+  }
+}
\ No newline at end of file