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+# Dark Mode Implementation Plan
+
+## Overview
+
+This document outlines the plan to implement dark mode for Sketch's web UI using Tailwind CSS's built-in dark mode capabilities.
+
+## Current State Analysis
+
+Sketch's web UI currently uses:
+
+- Tailwind CSS with basic configuration
+- Lit web components extending `SketchTailwindElement`
+- Components avoid Shadow DOM (`createRenderRoot() { return this; }`)
+- Standard Tailwind classes like `bg-white`, `text-gray-600`, `border-gray-200`
+- Global CSS approach, making dark mode implementation straightforward
+
+## Implementation Strategy: Class-Based Dark Mode
+
+### Phase 1: Foundation
+
+#### 1. Update Tailwind Configuration
+
+```javascript
+// tailwind.config.js
+export default {
+  content: ["./src/**/*.{js,ts,jsx,tsx,html}"],
+  darkMode: "class", // Enable class-based dark mode
+  plugins: ["@tailwindcss/container-queries"],
+  theme: {
+    extend: {
+      // Custom colors for better dark mode support
+      colors: {
+        // Define semantic color tokens
+        surface: {
+          DEFAULT: "#ffffff",
+          dark: "#1f2937",
+        },
+        "surface-secondary": {
+          DEFAULT: "#f9fafb",
+          dark: "#374151",
+        },
+      },
+      animation: {
+        "fade-in": "fadeIn 0.3s ease-in-out",
+      },
+      keyframes: {
+        fadeIn: {
+          "0%": {
+            opacity: "0",
+            transform: "translateX(-50%) translateY(10px)",
+          },
+          "100%": {
+            opacity: "1",
+            transform: "translateX(-50%) translateY(0)",
+          },
+        },
+      },
+    },
+  },
+};
+```
+
+#### 2. Create Theme Management Service
+
+```typescript
+// src/web-components/theme-service.ts
+export class ThemeService {
+  private static instance: ThemeService;
+
+  static getInstance(): ThemeService {
+    if (!this.instance) {
+      this.instance = new ThemeService();
+    }
+    return this.instance;
+  }
+
+  toggleTheme(): void {
+    const isDark = document.documentElement.classList.contains("dark");
+    this.setTheme(isDark ? "light" : "dark");
+  }
+
+  setTheme(theme: "light" | "dark"): void {
+    document.documentElement.classList.toggle("dark", theme === "dark");
+    localStorage.setItem("theme", theme);
+
+    // Dispatch event for components that need to react
+    document.dispatchEvent(
+      new CustomEvent("theme-changed", {
+        detail: { theme },
+      }),
+    );
+  }
+
+  getTheme(): "light" | "dark" {
+    return document.documentElement.classList.contains("dark")
+      ? "dark"
+      : "light";
+  }
+
+  initializeTheme(): void {
+    const saved = localStorage.getItem("theme");
+    const prefersDark = window.matchMedia(
+      "(prefers-color-scheme: dark)",
+    ).matches;
+    const theme = saved || (prefersDark ? "dark" : "light");
+    this.setTheme(theme as "light" | "dark");
+
+    // Listen for system theme changes
+    window
+      .matchMedia("(prefers-color-scheme: dark)")
+      .addEventListener("change", (e) => {
+        if (!localStorage.getItem("theme")) {
+          this.setTheme(e.matches ? "dark" : "light");
+        }
+      });
+  }
+}
+```
+
+#### 3. Theme Toggle Component
+
+```typescript
+// src/web-components/theme-toggle.ts
+import { html } from "lit";
+import { customElement, state } from "lit/decorators.js";
+import { SketchTailwindElement } from "./sketch-tailwind-element.js";
+import { ThemeService } from "./theme-service.js";
+
+@customElement("theme-toggle")
+export class ThemeToggle extends SketchTailwindElement {
+  @state() private isDark = false;
+
+  private themeService = ThemeService.getInstance();
+
+  connectedCallback() {
+    super.connectedCallback();
+    this.isDark = document.documentElement.classList.contains("dark");
+
+    // Listen for theme changes from other sources
+    document.addEventListener("theme-changed", this.handleThemeChange);
+  }
+
+  disconnectedCallback() {
+    super.disconnectedCallback();
+    document.removeEventListener("theme-changed", this.handleThemeChange);
+  }
+
+  private handleThemeChange = (e: CustomEvent) => {
+    this.isDark = e.detail.theme === "dark";
+  };
+
+  private toggleTheme() {
+    this.themeService.toggleTheme();
+  }
+
+  render() {
+    return html`
+      <button
+        @click=${this.toggleTheme}
+        class="p-2 rounded-md border border-gray-300 dark:border-gray-600 
+               bg-white dark:bg-gray-800 text-gray-700 dark:text-gray-200
+               hover:bg-gray-50 dark:hover:bg-gray-700 transition-colors
+               focus:outline-none focus:ring-2 focus:ring-blue-500"
+        title="Toggle theme"
+        aria-label="Toggle between light and dark mode"
+      >
+        ${this.isDark ? "☀️" : "🌙"}
+      </button>
+    `;
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "theme-toggle": ThemeToggle;
+  }
+}
+```
+
+#### 4. Initialize Theme in App Shell
+
+Add theme initialization to the main app shell component:
+
+```typescript
+// In sketch-app-shell.ts or similar
+import { ThemeService } from "./theme-service.js";
+
+connectedCallback() {
+  super.connectedCallback();
+  ThemeService.getInstance().initializeTheme();
+}
+```
+
+### Phase 2: Component Updates
+
+#### Systematic Component Audit
+
+1. **Identify all components using color classes**
+
+   - Search for `bg-`, `text-`, `border-`, `ring-`, `divide-` classes
+   - Document current color usage patterns
+
+2. **Add dark mode variants systematically**
+
+   - Start with core components (app shell, chat input, etc.)
+   - Update classes following the pattern:
+
+     ```typescript
+     // Before:
+     class="bg-white text-gray-900 border-gray-200"
+
+     // After:
+     class="bg-white dark:bg-gray-900 text-gray-900 dark:text-gray-100 border-gray-200 dark:border-gray-700"
+     ```
+
+3. **Priority order for component updates:**
+   1. `sketch-app-shell` - Main container
+   2. `sketch-chat-input` - Primary interaction component
+   3. `sketch-container-status` - Status indicators
+   4. `sketch-call-status` - Call indicators
+   5. Demo components and other secondary components
+
+#### Common Dark Mode Color Mappings
+
+```scss
+// Light -> Dark mappings
+bg-white -> bg-gray-900
+bg-gray-50 -> bg-gray-800
+bg-gray-100 -> bg-gray-800
+bg-gray-200 -> bg-gray-700
+
+text-gray-900 -> text-gray-100
+text-gray-800 -> text-gray-200
+text-gray-700 -> text-gray-300
+text-gray-600 -> text-gray-400
+text-gray-500 -> text-gray-500 (neutral)
+
+border-gray-200 -> border-gray-700
+border-gray-300 -> border-gray-600
+
+ring-gray-300 -> ring-gray-600
+```
+
+### Phase 3: Polish and Testing
+
+#### 1. Smooth Transitions
+
+- Add `transition-colors` to interactive elements
+- Consider adding a global transition class for theme changes
+
+#### 2. Accessibility
+
+- Ensure sufficient contrast ratios in both modes
+- Test with screen readers
+- Verify focus indicators work in both themes
+- Add proper ARIA labels to theme toggle
+
+#### 3. Testing Checklist
+
+- [ ] Theme persists across page reloads
+- [ ] System preference detection works
+- [ ] All components render correctly in both modes
+- [ ] Interactive states (hover, focus, active) work in both themes
+- [ ] No flash of unstyled content (FOUC)
+- [ ] Works across different screen sizes
+- [ ] Performance impact is minimal
+
+## File Structure
+
+```
+src/web-components/
+├── theme-service.ts          # Theme management service
+├── theme-toggle.ts           # Theme toggle component
+├── sketch-tailwind-element.ts # Base class (existing)
+└── [other components].ts     # Updated with dark mode variants
+```
+
+## Benefits of This Approach
+
+- **Incremental**: Can be implemented component by component
+- **Standard**: Uses Tailwind's built-in dark mode features
+- **Performant**: Class-based approach is efficient
+- **Maintainable**: Clear separation of concerns with theme service
+- **Accessible**: Respects system preferences by default
+- **Consistent**: Follows Sketch's existing component patterns
+
+## Implementation Timeline
+
+1. **Week 1**: Phase 1 - Foundation (config, service, toggle)
+2. **Week 2**: Phase 2 - Core component updates
+3. **Week 3**: Phase 2 - Secondary component updates
+4. **Week 4**: Phase 3 - Polish, testing, and accessibility
+
+## Notes
+
+- Components extend `SketchTailwindElement` (not `LitElement`)
+- No Shadow DOM usage allows for global Tailwind classes
+- Theme service uses singleton pattern for consistency
+- Event system allows components to react to theme changes
+- LocalStorage preserves user preference across sessions