diff --git a/AI_INIT.md b/AI_INIT.md
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+++ b/AI_INIT.md
@@ -3,57 +3,88 @@
 Welcome to the KoalaSync project. This file is the primary entry point for any developer or AI agent working on this codebase. It defines the architecture, non-negotiables, and workflows required to maintain the stability and security of the system.
 
 > [!IMPORTANT]
-> **Privacy & Data Sovereignty**: KoalaSync follows a strict **Zero-External-Requests Policy**: The extension and website must not make requests to any third-party domains. All assets must be self-hosted.
-> - **Font Stack**: Use a modern system font stack to maintain a premium look without external dependencies.
+> **Privacy & Data Sovereignty**: KoalaSync follows a strict **Zero-External-Requests Policy**: The extension and website must not make requests to any third-party domains (Google Fonts, CDNs, etc.). All assets (fonts, icons, scripts) must be self-hosted or use system defaults.
+> - **Font Stack**: Use a modern system font stack (e.g., -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif) to maintain a premium look without external dependencies. Prohibit the use of `@import` or `<link>` for external font services.
 
 ---
 
 ## 1. Project Overview
-KoalaSync is a specialized tool for **synchronized video playback** across multiple remote peers. 
-- **Workflow**: A user creates a room, shares an invitation link, and all peers are synchronized via a Node.js relay server.
+KoalaSync is a specialized tool for **synchronized video playback** across multiple remote peers. It supports YouTube, Twitch, and native HTML5 video elements. 
+- **Users**: Friends or groups wanting to watch synchronized content together.
+- **Workflow**: A user creates a room, shares an invitation link, and all peers in that room are synchronized via a Node.js relay server.
 - **Identity**: Users are identified by a unique hex `peerId` combined with a customizable `username`.
 
 ## 2. Repository Structure
-- `extension/`: Chrome Extension (Manifest V3).
+- `extension/`: Chrome Extension (Manifest V3). Contains background service worker, content scripts, and popup UI.
 - `server/`: Node.js Relay Server using Socket.IO (WebSocket-only).
-- `website/`: Landing Page & Invitation Bridge.
-- `shared/`: Single Source of Truth for protocol constants and event names.
+- `website/`: **Landing Page** & Invitation Bridge (Marketing, Tutorials, and Downloads).
+- `shared/`: **Single Source of Truth** for protocol constants and event names.
+- `scripts/`: Utility scripts (e.g., `sync-constants.sh`).
+- `docker-compose.yml`: Root-level orchestration for the relay server.
+
+> [!IMPORTANT]
+> `shared/constants.js` and `shared/blacklist.js` must be synchronized to the `extension/shared/` directory after every modification by running `./scripts/sync-constants.sh` or `.\scripts\sync-constants.bat`.
 
 ## 3. Mandatory Reading
-1. [ARCHITECTURE.md](ARCHITECTURE.md) – Communication flows and Dual Heartbeat protocol.
-2. [extension/README.md](extension/README.md) – UI structure and component overview.
+Before touching any code, you MUST read the following documents in order:
+1. [ARCHITECTURE.md](ARCHITECTURE.md) – Detailed communication flows, Dual Heartbeat, and two-phase sync protocol.
+2. [extension/README.md](extension/README.md) – Extension components, tab structure, and loading process.
+3. [SYNC_GUIDE.md](SYNC_GUIDE.md) – Protocol constants and synchronization requirements.
 
 ## 4. Design Guidelines
+The popup UI follows a strict design system. Do not modify these variables or the layout structure without explicit approval.
+- **Font**: System font stack. **MANDATORY**: No external CDNs or Google Fonts to ensure 100% privacy.
 - **Popup Width**: Fixed at `320px`.
-- **Tab Structure**: **Room**, **Sync**, **Settings**, and **Dev**.
-- **CSS Variables**: Uses the CSS variables defined in `popup.html` for a consistent Dark Mode / Glassmorphic look.
+- **Tab Structure**: Must maintain the **Room**, **Sync**, **Settings**, and **Dev** tabs.
+- **CSS Variables**:
+  | Variable | Value | Purpose |
+  | :--- | :--- | :--- |
+  | `--bg` | `#0f172a` | Main background |
+  | `--card` | `#1e293b` | Form and info cards |
+  | `--accent` | `#6366f1` | Primary actions and branding |
+  | `--success` | `#22c55e` | Success states / Online dot |
+  | `--error` | `#ef4444` | Errors / Offline dot |
 
 ## 5. Non-Negotiables (Core Logic)
-- **Two-Phase Force Sync**: `Prepare` → `ACK` → `Execute` flow for frame-perfect sync.
+The following features are critical and must not be removed or fundamentally altered:
+- **Two-Phase Force Sync**: The `Prepare` → `ACK` → `Execute` flow ensures all peers are buffered before playback resumes.
 - **Dual Heartbeat**: 
-    - **Background Heartbeat (30s)**: Keeps the session alive even without a video.
-    - **Content Heartbeat (15s)**: Transmits current video metadata (title, time).
-- **Dead Peer Pruning**: Server automatically disconnects peers after 5 minutes of total silence.
-- **Deduplication**: Server kills old sockets if a user re-joins with the same `peerId`.
+    - **Background Heartbeat (30s)**: Ensures session persistence even without a video element.
+    - **Content Heartbeat (15s)**: Transmits current video metadata (time, title).
+- **Dead Peer Pruning**: Server "Reaper" disconnects peers after 5 minutes of total silence (no heartbeats or events).
+- **Deduplication**: Server kills old sockets if a user re-joins with the same `peerId` to prevent ghosts.
+- **Platform Specifics**: Specialized click-logic for YouTube (`.ytp-play-button`) and Twitch.
+- **pollSeekReady()**: Polling mechanism that checks `video.readyState` before acknowledging sync.
+- **SW Keep-alive**: Use of `chrome.alarms` to prevent the Manifest V3 Service Worker from suspending.
 - **Diagnostics**: The "Dev" tab provides real-time access to the underlying `<video>` state for troubleshooting.
+- **Persistence**: `peerId` and `username` must be stored to remain stable across sessions.
 
 ## 6. Technical Constraints
-- **No Bundler**: Plain ES Modules only.
-- **Socket.IO Protocol**: Manual implementation of the wire protocol in `background.js`.
-- **Docker Context**: Must build from the **Repo Root**.
+- **No Bundler**: The extension uses plain ES Modules. Do not introduce build steps or npm packages into the `extension/` folder.
+- **Manual Protocol**: `background.js` implements a subset of the Socket.IO wire protocol natives.
+- **Server Transport**: Restricted to `websocket` only. Polling is disabled.
+- **Docker Context**: The Docker build must run from the **Repo Root**.
+- **Manifest Settings**: `run_at` must remain `document_idle`, and `all_frames` must remain `false`.
 
 ## 7. Security & Deployment
-- **Invitation Links**: Correctly propagate server URLs and room credentials via the URL hash.
-- **Rate Limiting**: IP and socket-based limits are enforced server-side.
-- **Persistence**: `peerId` and `username` must persist across browser sessions.
+- **Tokens**: Security tokens are intentionally managed via `shared/constants.js` and server `.env`.
+- **Environment**: `.env` is excluded via `.gitignore`. Only `.env.example` should be committed.
+- **Revocation**: `MIN_VERSION` check on the server is used to deprecate old extension versions.
+- **Invitation Links**: Correctly propagate server URLs, Room IDs, and Passwords via the URL hash to the bridge.
 
 ## 8. Common Workflows
 
-### Modifying the Protocol
-1. Edit `shared/constants.js`.
-2. Run `scripts/sync-constants.bat` (Windows) or `scripts/sync-constants.sh` (POSIX).
-3. Restart the server and reload the extension.
+### Adding a Protocol Event
+1. Add the event name to `shared/constants.js`.
+2. Run the sync script (`.\scripts\sync-constants.bat` or `./scripts/sync-constants.sh`).
+3. Implement the handler in `server/index.js` and `background.js`.
 
-### Testing
-- Use **different browser profiles** or vendors to test multi-peer logic locally.
-- Use the **Dev tab** to verify that the extension is correctly detecting the video state.
+### Testing Locally
+1. Load `extension/` as an "Unpacked Extension" in Chrome.
+2. Start the server from the root: `docker-compose up --build`.
+3. Use **different browser profiles** or vendors to test multi-peer logic.
+4. Use the **Dev tab** to verify real-time video element metadata.
+
+### Locking Old Versions
+1. Increase `APP_VERSION` in `shared/constants.js`.
+2. Update `MIN_VERSION` in the server's `.env` file and restart.