yvgude--lean-ctx/packages/chrome-lean-ctx

lean-ctx Chrome Extension

Token compression for web-based AI chat tools. Automatically compresses code when pasting into ChatGPT, Claude.ai, Gemini, or GitHub Copilot Chat.

Features

• Auto-compress pastes — Code pasted into AI chat inputs is automatically compressed
• Token counter badge — Shows savings in real-time after each compression
• Native messaging — Connects to local lean-ctx binary for full compression (95+ patterns)
• Fallback compression — Basic comment/whitespace removal when native host unavailable
• Popup dashboard — Token savings stats + toggle controls

Supported Sites

• ChatGPT / chat.openai.com
• Claude.ai
• Gemini
• GitHub Copilot Chat
• Lovable
• Bolt.new
• v0.dev
• Poe
• Google AI Studio
• Perplexity Labs

Installation

1. Load Extension (Developer Mode)

1. Open chrome://extensions
2. Enable "Developer mode"
3. Click "Load unpacked" and select this directory
4. Note the Extension ID

2. Install Native Messaging Host (optional, for full compression)

cd native-host
chmod +x install.sh bridge.sh
./install.sh

Then edit the native messaging manifest to include your Extension ID.

3. Requirements

• lean-ctx binary for native messaging (cargo install lean-ctx)
• Python 3 for the native messaging bridge

How It Works

1. When you paste text (>200 chars) into a supported AI chat input
2. The extension intercepts the paste event
3. Text is sent to the background service worker
4. If native messaging is available, lean-ctx compresses it
5. Otherwise, fallback compression removes comments and whitespace
6. Compressed text replaces the paste, badge shows savings

Settings

Toggle via the popup (click extension icon):

• Auto-compress pastes — Enable/disable automatic compression
• Native messaging — Use lean-ctx binary for advanced compression

Enterprise-Managed Deployment

The extension supports Chrome Enterprise policies via chrome.storage.managed (schema: managed_schema.json). Managed values override user choices; the popup shows a "Managed by your organization" banner and locks those controls.

Available policy keys:

Key	Type	Effect
enabled	boolean	Force compress-on-send on/off fleet-wide
autoCompressPaste	boolean	Force clipboard auto-compress on/off
threshold	integer	Minimum token estimate before compressing
gatewayBaseUrl	string	Org AI-gateway endpoint, surfaced in the popup for base-URL-capable tools

Example policy (macOS: managed preferences plist, Windows: registry under Software\Policies\Google\Chrome\3rdparty\extensions\<extension-id>\policy, Linux: /etc/opt/chrome/policies/managed/*.json):

{
  "3rdparty": {
    "extensions": {
      "<extension-id>": {
        "enabled": true,
        "autoCompressPaste": true,
        "gatewayBaseUrl": "https://ai-gateway.example.com"
      }
    }
  }
}

Honest boundary — what the extension can and cannot do

• Can: compress prompts you type/paste into supported web chats (client-side token reduction), and display your org's gateway endpoint so engineers configure their CLI/IDE tools correctly.
• Cannot: re-route first-party AI web/desktop apps (claude.ai, ChatGPT web, Claude Desktop) through your gateway. Manifest V3 grants no webRequest/declarativeNetRequest here, and those apps pin their own backends. Org-side metering/routing covers only traffic that reaches the gateway via a base URL: Claude Code CLI, Cursor, IDE API clients, SDKs. gatewayBaseUrl is informational for the user — not a traffic redirect.