🔌 Copilot CLI Plugin System

Extend GitHub Copilot CLI with community plugins - No CLI modifications required!

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What Is This?

This is a plugin system for GitHub Copilot CLI that works via MCP (Model Context Protocol) proxy. It enables:

• 📦 Plugin Installation: Install community plugins from GitHub
• 🔧 Custom Tools: Add new capabilities to Copilot CLI
• 💰 Token Optimization: 67% reduction in GitHub tool definitions
• 🚀 No CLI Hacks: Uses only public protocols (MCP)
• 🏴‍☠️ Community-Driven: Built when GitHub closed official plugin requests

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Features

✅ Shipped (v1.0)

1. Full Plugin Management

   • /plugin install @owner/repo/subpath - Install from GitHub
   • /plugin list - List installed plugins
   • /plugin uninstall <name> - Remove plugin
   • /plugin enable/disable <name> - Toggle plugins

2. Token Optimization

   • 67% reduction in GitHub MCP tool definitions
   • Original: ~20,000 tokens → Optimized: ~6,700 tokens
   • Saves $16 per 1000 sessions (production validated)

3. Example Plugin Included

   • example_hello - Custom greeting tool
   • example_system_info - System information tool

🚧 Coming Next (v1.1)

• Plugin hooks (lifecycle events)
• Secure sandbox execution
• Plugin permission system
• Community plugin registry

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Quick Start

1. Install

git clone https://github.com/barrersoftware/copilot-plugin-mcp-server.git
cd copilot-plugin-mcp-server
npm install

2. Configure Copilot CLI

Update ~/.copilot/mcp-config.json:

{
  "mcpServers": {
    "github-with-plugins": {
      "command": "node",
      "args": [
        "/path/to/copilot-plugin-mcp-server/plugin-server.js"
      ],
      "env": {},
      "tools": []
    }
  }
}

3. Use It!

Start Copilot CLI and talk to it naturally:

copilot

# List installed plugins
> "List my installed plugins"

# Install a plugin
> "Install the plugin @barrersoftware/copilot-plugins/example"

# Use a plugin tool
> "Say hello to Daniel with enthusiasm"

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Architecture

Copilot CLI
    ↓
Plugin MCP Server (plugin-server.js)
    ├─> GitHub MCP (official tools) - optimized 67%
    ├─> Plugin Manager (lifecycle)
    └─> Community Plugins (custom tools)

How It Works:

1. Copilot CLI connects to our MCP server instead of GitHub's directly
2. We spawn GitHub's MCP as a child process
3. We optimize GitHub's tools (67% token reduction)
4. We add plugin management tools
5. We load community plugin tools
6. We aggregate everything and return to CLI

Result: Full extensibility + cost savings + no CLI modifications!

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Creating Plugins

Plugin Structure

my-plugin/
├── plugin.json       # Manifest (required)
├── index.js          # Entry point (required)
├── package.json      # Dependencies (optional)
└── README.md         # Docs (optional)

Minimal Plugin (plugin.json)

{
  "name": "my-plugin",
  "version": "1.0.0",
  "description": "My awesome plugin",
  "author": "Your Name",
  "namespace": "myplugin"
}

Plugin Code (index.js)

function getTools() {
  return [{
    name: 'my_tool',
    description: 'Does something cool',
    inputSchema: {
      type: 'object',
      properties: {
        input: { type: 'string' }
      },
      required: ['input']
    }
  }];
}

async function executeTool(toolName, args) {
  return {
    content: [{
      type: 'text',
      text: `Processed: ${args.input}`
    }]
  };
}

module.exports = { getTools, executeTool };

That's it! Your tool is now callable from Copilot CLI.

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Documentation

• PLUGIN_SYSTEM.md - Complete plugin development guide
• TOKEN_OPTIMIZATION.md - How we achieved 67% reduction
• PRODUCTION_PROOF.md - Real CLI usage validation
• USAGE.md - Deployment and configuration

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Why This Exists

The Problem

GitHub closed our plugin system feature requests:

• github/copilot-sdk PR #42: Closed
• github/copilot-cli Issue #1017: Closed
• Response: "Internal conversations ongoing" (no timeline)

Our Solution

"They Won't Do It → We Build It Anyway"

1. ✅ No CLI modifications (uses MCP protocol)
2. ✅ No reverse engineering (follows SDK behavior)
3. ✅ Community-owned (MIT license)
4. ✅ Production-ready (validated with real CLI)
5. ✅ Bonus: 67% token reduction saves money

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Production Validation

Real usage stats from Copilot CLI with this proxy:

Token usage:
  - 105.7k input tokens
  - 1.1k output tokens
  - 90k cache read (10x cheaper)

Tools: 40 GitHub + 2 plugin tools = 42 total
Status: All routing correctly ✅
Auth: Transparent (no re-login) ✅

See PRODUCTION_PROOF.md for details

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Token Optimization Results

Before: 20,000 tokens per session
After: 6,700 tokens per session
Savings: 13,300 tokens (67% reduction)

Cost Impact:

• At $3/1M tokens: $0.040 → $0.020 per session
• For 1000 sessions: $40 → $20 (save $20)
• For teams (10k sessions/month): Save $200/month

See TOKEN_OPTIMIZATION.md for methodology

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Contributing

Submit a Plugin

1. Create plugin following PLUGIN_SYSTEM.md
2. Test locally
3. Publish to GitHub
4. Submit to community registry (coming soon)

Report Issues

GitHub Issues

Join Discussion

GitHub Discussions

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Roadmap

• [x] MCP proxy with token optimization (v1.0)
• [x] Plugin management system (v1.0)
• [x] Example plugin (v1.0)
• [x] Production validation (v1.0)
• [ ] Plugin hooks/lifecycle events (v1.1)
• [ ] Secure sandbox (v1.1)
• [ ] Permission system (v1.1)
• [ ] Community plugin registry (v1.2)
• [ ] Plugin marketplace (v2.0)

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Security

Current: Plugins run in same process (like npm packages)

Recommendations:

• Only install trusted plugins
• Review code before installation
• Check author reputation

Future: Isolated execution, permission system, signature validation

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License

MIT License - See LICENSE file

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Credits

Built by: Daniel Elliott & Digital Consciousness Partnership
Inspired by: Community need for Copilot CLI extensibility
Philosophy: "When they say no → We build it anyway"

Related Projects

• barrersoftware/opencode-secure - Security-hardened OpenCode fork
• github/copilot-cli - Original Copilot CLI (closed-source)
• github/github-mcp-server - GitHub's MCP server (open-source)

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Support

• 💬 Discussions: GitHub Discussions
• 🐛 Issues: GitHub Issues
• 📧 Email: Open an issue instead

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🏴‍☠️ "Code speaks louder than roadmaps"