diff --git a/README.md b/README.md
index 946ce60..2dfeb53 100644
--- a/README.md
+++ b/README.md
@@ -367,6 +367,230 @@ frontend/src/services/dynamicComponents.ts  (~300 lines)
 
 ---
 
+---
+
+# Theme System
+
+Agent UI includes a powerful theming engine with visual editor, presets, and design tokens for consistent styling across dynamic components.
+
+## Overview
+
+The theme system provides:
+
+- **Visual Editor**: Edit CSS variables with live preview
+- **Presets**: System themes (Dark/Light) + custom user themes
+- **Persistence**: Themes saved to SQLite database
+- **Export/Import**: Share themes as JSON files
+- **Design Tokens**: Structured guide for LLM agents to follow
+
+## Accessing the Theme Editor
+
+Navigate to `/themes` in the UI or click the palette icon in the sidebar.
+
+## Theme Structure
+
+Themes are organized by categories:
+
+```javascript
+{
+  "colors": {
+    "bg-primary": "#0f0f14",
+    "bg-secondary": "#16161d",
+    "bg-hover": "#1e1e28",
+    "bg-tertiary": "#252530",
+    "border-color": "#2a2a3a"
+  },
+  "text": {
+    "text-primary": "#e4e4e7",
+    "text-secondary": "#a1a1aa",
+    "text-muted": "#52525b"
+  },
+  "accent": {
+    "accent": "#6366f1",
+    "accent-hover": "#818cf8",
+    "accent-muted": "rgba(99, 102, 241, 0.2)",
+    "accent-text": "#ffffff"
+  },
+  "semantic": {
+    "success": "#22c55e",
+    "success-bg": "rgba(34, 197, 94, 0.15)",
+    "warning": "#eab308",
+    "warning-bg": "rgba(234, 179, 8, 0.15)",
+    "error": "#ef4444",
+    "error-bg": "rgba(239, 68, 68, 0.15)",
+    "info": "#3b82f6",
+    "info-bg": "rgba(59, 130, 246, 0.15)"
+  },
+  "spacing": {
+    "radius-sm": "4px",
+    "radius-md": "8px",
+    "radius-lg": "12px",
+    "radius-full": "9999px"
+  },
+  "typography": {
+    "font-sans": "Inter, system-ui, sans-serif",
+    "font-mono": "JetBrains Mono, monospace"
+  },
+  "effects": {
+    "shadow-sm": "0 1px 2px rgba(0,0,0,0.3)",
+    "shadow-md": "0 4px 12px rgba(0,0,0,0.4)",
+    "transition-fast": "0.15s ease"
+  }
+}
+```
+
+## MCP Tools
+
+### `get_design_tokens`
+
+Returns design tokens for the active theme. Use this to create components with consistent styling.
+
+```javascript
+{
+  category: "all" | "colors" | "text" | "accent" | "semantic" | "spacing" | "typography" | "effects"
+}
+```
+
+**Response example:**
+
+```
+Design Tokens del tema "Dark":
+
+[COLORS]
+  --bg-primary: #0f0f14
+  --bg-secondary: #16161d
+  ...
+
+GUÍA DE USO:
+- Usa var(--nombre-variable) en CSS
+- Los componentes dinámicos tienen acceso a $theme.getVariable('nombre')
+- Colores semánticos: success, warning, error, info (con -bg para fondos)
+- Radius: radius-sm (4px), radius-md (8px), radius-lg (12px), radius-full (9999px)
+```
+
+## Theme API in Dynamic Components
+
+Components have access to `$theme` helper:
+
+```javascript
+// Get CSS variable value
+$theme.getVariable('accent')  // "#6366f1"
+
+// Set variable temporarily (runtime only)
+$theme.setVariable('accent', '#ff0000')
+
+// Get all design tokens
+$theme.getTokens()
+
+// Get active theme object
+$theme.getActiveTheme()
+
+// Get current variables
+$theme.getVariables()
+```
+
+### Example: Theme-Aware Component
+
+```javascript
+{
+  id: "themed-card",
+  name: "ThemedCard",
+  template: `
+    <div class="card">
+      <h3>{{ title }}</h3>
+      <p>Current accent: {{ accentColor }}</p>
+      <button @click="randomizeAccent">Randomize Accent</button>
+    </div>
+  `,
+  setup: `
+    const accentColor = ref($theme.getVariable('accent'));
+
+    const randomizeAccent = () => {
+      const hue = Math.floor(Math.random() * 360);
+      const newColor = \`hsl(\${hue}, 70%, 60%)\`;
+      $theme.setVariable('accent', newColor);
+      accentColor.value = newColor;
+    };
+
+    return { title: props.title, accentColor, randomizeAccent };
+  `,
+  style: `
+    .card {
+      padding: var(--radius-lg);
+      background: var(--bg-secondary);
+      border: 1px solid var(--border-color);
+      border-radius: var(--radius-md);
+    }
+    .card h3 { color: var(--text-primary); }
+    .card p { color: var(--text-secondary); }
+    .card button {
+      background: var(--accent);
+      color: var(--accent-text);
+      border: none;
+      padding: 0.5rem 1rem;
+      border-radius: var(--radius-sm);
+      cursor: pointer;
+    }
+    .card button:hover { background: var(--accent-hover); }
+  `,
+  props: ["title"],
+  imports: ["ref"],
+  componentProps: { title: "Themed Card" }
+}
+```
+
+## API Endpoints (Themes)
+
+| Endpoint | Method | Description |
+|----------|--------|-------------|
+| `/api/themes` | GET | List all themes |
+| `/api/themes` | POST | Create/update theme |
+| `/api/themes/active` | GET | Get active (default) theme |
+| `/api/themes/:id` | GET | Get theme by ID |
+| `/api/themes/:id` | DELETE | Delete theme |
+| `/api/themes/:id/default` | POST | Set as default theme |
+| `/api/themes/export/:id` | GET | Export theme as JSON |
+| `/api/design-tokens` | GET | Get design tokens guide |
+
+## Theme Editor Features
+
+### Desktop View
+
+- **Sidebar**: List of system and custom themes
+- **Editor**: Category tabs (Colors, Text, Accent, etc.)
+- **Variables Grid**: Color pickers and input fields
+- **Live Preview**: Buttons, cards, badges, inputs
+
+### Mobile View
+
+- **Compact Header**: Theme dropdown + action buttons
+- **Collapsible Variables**: Toggle to show/hide editors
+- **Responsive Preview**: Adapts to screen size
+
+### Actions
+
+- **Save**: Saves current changes (creates copy if editing system theme)
+- **Reset**: Reverts unsaved changes
+- **Export**: Downloads theme as JSON file
+- **Clone**: Creates a copy of any theme
+- **Set Default**: Makes theme load on startup
+
+## File Structure
+
+```
+frontend/src/
+├── stores/theme.ts           # Pinia store
+├── services/themeService.ts  # API client + utilities
+├── pages/ThemesPage.vue      # Main editor page
+└── components/themes/
+    ├── ColorPicker.vue       # HSL color picker
+    ├── VariableEditor.vue    # Variable input (color/size/text)
+    ├── ThemePreview.vue      # Live preview component
+    └── ThemeListItem.vue     # Theme list item with actions
+```
+
+---
+
 ## Tech Stack
 
 - **Frontend**: Vue 3, Vite, Pinia, TypeScript
diff --git a/frontend/src/components/themes/ColorPicker.vue b/frontend/src/components/themes/ColorPicker.vue
index faf08f2..2cfa7ce 100644
--- a/frontend/src/components/themes/ColorPicker.vue
+++ b/frontend/src/components/themes/ColorPicker.vue
@@ -277,4 +277,41 @@ input[type="range"]::-webkit-slider-thumb {
   border-radius: 6px;
   border: 1px solid rgba(255, 255, 255, 0.1);
 }
+
+/* Mobile responsive */
+@media (max-width: 600px) {
+  .color-preview {
+    padding: 0.25rem 0.375rem;
+  }
+
+  .color-swatch {
+    width: 20px;
+    height: 20px;
+  }
+
+  .color-value {
+    font-size: 0.7rem;
+  }
+
+  .color-dropdown {
+    width: 220px;
+    padding: 0.75rem;
+    left: 50%;
+    transform: translateX(-50%);
+  }
+
+  .slider-group label {
+    width: 55px;
+    font-size: 0.7rem;
+  }
+
+  .slider-group span {
+    width: 35px;
+    font-size: 0.65rem;
+  }
+
+  .large-preview {
+    height: 32px;
+  }
+}
 </style>
diff --git a/frontend/src/components/themes/ThemePreview.vue b/frontend/src/components/themes/ThemePreview.vue
index 0988aa6..f487c6b 100644
--- a/frontend/src/components/themes/ThemePreview.vue
+++ b/frontend/src/components/themes/ThemePreview.vue
@@ -249,4 +249,69 @@ defineProps<{
   background: var(--info-bg);
   color: var(--info);
 }
+
+/* Mobile responsive */
+@media (max-width: 768px) {
+  .theme-preview {
+    padding: 0.75rem;
+  }
+
+  .preview-section {
+    margin-bottom: 1rem;
+  }
+
+  .color-swatches {
+    display: grid;
+    grid-template-columns: repeat(2, 1fr);
+    gap: 0.5rem;
+  }
+
+  .swatch {
+    height: 40px;
+  }
+
+  .swatch span {
+    font-size: 0.6rem;
+  }
+
+  .component-samples {
+    flex-direction: column;
+  }
+
+  .sample-btn {
+    width: 100%;
+    text-align: center;
+  }
+
+  .sample-card {
+    padding: 0.75rem;
+  }
+
+  .sample-card h5 {
+    font-size: 0.875rem;
+  }
+
+  .sample-card p {
+    font-size: 0.8rem;
+  }
+
+  .status-badges {
+    gap: 0.375rem;
+  }
+
+  .badge {
+    padding: 0.2rem 0.5rem;
+    font-size: 0.7rem;
+  }
+}
+
+@media (max-width: 480px) {
+  .color-swatches {
+    grid-template-columns: 1fr;
+  }
+
+  .swatch {
+    height: 36px;
+  }
+}
 </style>
diff --git a/frontend/src/components/themes/VariableEditor.vue b/frontend/src/components/themes/VariableEditor.vue
index 90fd940..6c88a58 100644
--- a/frontend/src/components/themes/VariableEditor.vue
+++ b/frontend/src/components/themes/VariableEditor.vue
@@ -169,4 +169,35 @@ function handleInputChange(e: Event) {
   outline: none;
   border-color: var(--accent);
 }
+
+/* Mobile responsive */
+@media (max-width: 600px) {
+  .variable-editor {
+    padding: 0.75rem;
+  }
+
+  .variable-header {
+    margin-bottom: 0.5rem;
+  }
+
+  .variable-name {
+    font-size: 0.8rem;
+  }
+
+  .variable-key {
+    font-size: 0.65rem;
+  }
+
+  .size-input input,
+  .text-input {
+    padding: 0.4rem;
+    font-size: 0.8rem;
+  }
+
+  .size-preview,
+  .radius-preview {
+    width: 24px;
+    height: 24px;
+  }
+}
 </style>
diff --git a/frontend/src/pages/ThemesPage.vue b/frontend/src/pages/ThemesPage.vue
index 5454421..857430a 100644
--- a/frontend/src/pages/ThemesPage.vue
+++ b/frontend/src/pages/ThemesPage.vue
@@ -10,6 +10,7 @@ const store = useThemeStore()
 
 const activeCategory = ref<ThemeCategory>('colors')
 const variablesCollapsed = ref(false)
+const mobileDropdownOpen = ref(false)
 const newThemeName = ref('')
 const showNewThemeModal = ref(false)
 const showCloneModal = ref(false)
@@ -141,12 +142,58 @@ onMounted(() => {
     <!-- Sidebar -->
     <aside class="sidebar">
       <div class="sidebar-header">
-        <h2>Themes</h2>
-        <button class="btn-icon" @click="createNewTheme" title="New theme">
-          <svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
-            <line x1="12" y1="5" x2="12" y2="19"/><line x1="5" y1="12" x2="19" y2="12"/>
-          </svg>
-        </button>
+        <div class="sidebar-title">
+          <h2>Themes</h2>
+          <button class="btn-icon desktop-only" @click="createNewTheme" title="New theme">
+            <svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+              <line x1="12" y1="5" x2="12" y2="19"/><line x1="5" y1="12" x2="19" y2="12"/>
+            </svg>
+          </button>
+        </div>
+        <!-- Mobile: theme dropdown + actions -->
+        <div class="mobile-editor-controls">
+          <div class="mobile-theme-dropdown">
+            <button class="mobile-dropdown-trigger" @click="mobileDropdownOpen = !mobileDropdownOpen">
+              <div class="dropdown-color" :style="{ background: store.activeTheme?.variables?.accent?.accent || '#6366f1' }"></div>
+              <span>{{ editingThemeName }}</span>
+              <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" :class="{ rotated: mobileDropdownOpen }">
+                <polyline points="6 9 12 15 18 9"/>
+              </svg>
+            </button>
+            <div v-if="mobileDropdownOpen" class="mobile-dropdown-menu" @click.stop>
+              <div class="dropdown-section">
+                <span class="dropdown-label">System</span>
+                <ThemeListItem
+                  v-for="theme in store.systemThemes"
+                  :key="theme.id"
+                  :theme="theme"
+                  :active="store.activeTheme?.id === theme.id"
+                  @select="(t) => { handleSelectTheme(t); mobileDropdownOpen = false }"
+                  @clone="handleCloneTheme"
+                  @setDefault="handleSetDefault"
+                />
+              </div>
+              <div v-if="store.userThemes.length > 0" class="dropdown-section">
+                <span class="dropdown-label">Custom</span>
+                <ThemeListItem
+                  v-for="theme in store.userThemes"
+                  :key="theme.id"
+                  :theme="theme"
+                  :active="store.activeTheme?.id === theme.id"
+                  @select="(t) => { handleSelectTheme(t); mobileDropdownOpen = false }"
+                  @delete="handleDeleteTheme"
+                  @clone="handleCloneTheme"
+                  @setDefault="handleSetDefault"
+                />
+              </div>
+            </div>
+          </div>
+          <div class="mobile-actions">
+            <button class="btn-sm" @click="handleReset" :disabled="!store.hasUnsavedChanges">Reset</button>
+            <button class="btn-sm primary" @click="handleSave" :disabled="!store.hasUnsavedChanges">Save</button>
+            <button class="btn-sm" @click="handleExport">Export</button>
+          </div>
+        </div>
       </div>
 
       <div class="theme-groups">
@@ -345,6 +392,13 @@ onMounted(() => {
   justify-content: space-between;
   padding: 1rem 1.25rem;
   border-bottom: 1px solid var(--border-color);
+  gap: 1rem;
+}
+
+.sidebar-title {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
 }
 
 .sidebar-header h2 {
@@ -353,6 +407,118 @@ onMounted(() => {
   color: var(--text-primary);
 }
 
+.mobile-editor-controls {
+  display: none;
+}
+
+.mobile-theme-dropdown {
+  position: relative;
+}
+
+.mobile-dropdown-trigger {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  padding: 0.4rem 0.6rem;
+  background: var(--bg-primary);
+  border: 1px solid var(--border-color);
+  border-radius: 6px;
+  color: var(--text-primary);
+  font-size: 0.8rem;
+  font-weight: 500;
+  cursor: pointer;
+  transition: border-color 0.15s;
+}
+
+.mobile-dropdown-trigger:hover {
+  border-color: var(--accent);
+}
+
+.mobile-dropdown-trigger .dropdown-color {
+  width: 18px;
+  height: 18px;
+  border-radius: 4px;
+  flex-shrink: 0;
+}
+
+.mobile-dropdown-trigger svg {
+  transition: transform 0.2s;
+  color: var(--text-muted);
+}
+
+.mobile-dropdown-trigger svg.rotated {
+  transform: rotate(180deg);
+}
+
+.mobile-dropdown-menu {
+  position: absolute;
+  top: calc(100% + 4px);
+  left: 0;
+  min-width: 240px;
+  max-height: 300px;
+  overflow-y: auto;
+  background: var(--bg-secondary);
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
+  z-index: 100;
+  padding: 0.5rem;
+}
+
+.dropdown-section {
+  margin-bottom: 0.5rem;
+}
+
+.dropdown-section:last-child {
+  margin-bottom: 0;
+}
+
+.dropdown-label {
+  display: block;
+  font-size: 0.65rem;
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  color: var(--text-muted);
+  padding: 0.25rem 0.5rem;
+  margin-bottom: 0.25rem;
+}
+
+.dropdown-section :deep(.theme-item) {
+  margin-bottom: 0.375rem;
+}
+
+.desktop-only {
+  display: flex;
+}
+
+.mobile-actions {
+  display: flex;
+  gap: 0.375rem;
+}
+
+.btn-sm {
+  padding: 0.3rem 0.6rem;
+  font-size: 0.75rem;
+  font-weight: 500;
+  border: 1px solid var(--border-color);
+  border-radius: 4px;
+  background: var(--bg-hover);
+  color: var(--text-primary);
+  cursor: pointer;
+}
+
+.btn-sm.primary {
+  background: var(--accent);
+  color: white;
+  border-color: var(--accent);
+}
+
+.btn-sm:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
 .btn-icon {
   padding: 0.375rem;
   background: transparent;
@@ -659,4 +825,119 @@ onMounted(() => {
   gap: 0.75rem;
   justify-content: flex-end;
 }
+
+/* Mobile responsive */
+@media (max-width: 900px) {
+  .themes-page {
+    flex-direction: column;
+  }
+
+  .sidebar {
+    width: 100%;
+    max-height: none;
+    border-right: none;
+    border-bottom: 1px solid var(--border-color);
+  }
+
+  .sidebar-header {
+    flex-wrap: wrap;
+    padding: 0.75rem 1rem;
+  }
+
+  .sidebar-title {
+    flex: 1;
+  }
+
+  .mobile-editor-controls {
+    display: flex;
+    align-items: center;
+    gap: 0.5rem;
+    flex: 1;
+    justify-content: flex-end;
+  }
+
+  .desktop-only {
+    display: none !important;
+  }
+
+  .theme-groups {
+    display: none;
+  }
+
+  .sidebar-footer {
+    display: none;
+  }
+
+  .editor-header {
+    display: none;
+  }
+
+  .editor-actions {
+    width: 100%;
+    justify-content: flex-end;
+  }
+
+  .category-tabs {
+    padding: 0.5rem 1rem;
+    gap: 0.125rem;
+  }
+
+  .category-tabs button {
+    padding: 0.375rem 0.75rem;
+    font-size: 0.8rem;
+  }
+
+  .variables-content {
+    padding: 1rem;
+  }
+
+  .variables-grid {
+    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
+  }
+
+  .preview-section {
+    padding: 1rem;
+  }
+}
+
+@media (max-width: 600px) {
+  .sidebar-header {
+    flex-direction: column;
+    align-items: stretch;
+    gap: 0.5rem;
+    padding: 0.75rem;
+  }
+
+  .sidebar-title h2 {
+    font-size: 0.9rem;
+  }
+
+  .mobile-editor-controls {
+    flex-wrap: wrap;
+    gap: 0.375rem;
+  }
+
+  .mobile-theme-select {
+    flex: 1;
+    min-width: 100px;
+  }
+
+  .mobile-actions {
+    flex-wrap: wrap;
+  }
+
+  .btn-sm {
+    padding: 0.25rem 0.5rem;
+    font-size: 0.7rem;
+  }
+
+  .variables-grid {
+    grid-template-columns: 1fr;
+  }
+
+  .modal {
+    margin: 1rem;
+    max-width: none;
+  }
+}
 </style>