BetterThanCopilot (Composer & Agent Engine)

A Cursor-like Composer and Autonomous Agent inside VS Code powered by your GitHub Copilot subscription, featuring Hybrid Graph-RAG, Plan & Agent Modes, MCP Tools, and 100% Zero Repo Footprint.

Architecture Overview

┌─────────────────────────────────────────────────────────────────────────────┐
│                            VS Code Extension                                │
│                                                                             │
│  ┌───────────────────────────────────────────────────────────────────────┐  │
│  │ React Webview UI (Sidebar & Composer)                                 │  │
│  │  ├─ Plan Mode: Interactive step DAG & architecture impact preview     │  │
│  │  ├─ Agent Mode: Live stream, tool call inspect, auto-retry loop       │  │
│  │  └─ Diagnostic Banner: Real-time compiler/linter self-correction      │  │
│  └──────────────────────────────────▲────────────────────────────────────┘  │
│                                     │ IPC (postMessage)                     │
│  ┌──────────────────────────────────▼────────────────────────────────────┐  │
│  │ Extension Host Orchestrator                                           │  │
│  │  ├─ State Machine: (PLANNING -> PREVIEW -> EXECUTING -> VERIFYING)    │  │
│  │  ├─ Zero-Trace Graph Engine (Nodes, Edges, 64-dim Embeddings in SQLite)│ │
│  │  ├─ MCP Client Manager (@modelcontextprotocol/sdk)                    │  │
│  │  ├─ Opportunistic Scanner (.mcp.json, .gemini/skills, .cursor/rules)  │  │
│  │  ├─ Multi-file Diff Engine (Atomic replacement with preview)          │  │
│  │  └─ LSP Diagnostic Watcher (vscode.languages.getDiagnostics)          │  │
│  └──────────────────────────────────▲────────────────────────────────────┘  │
│                                     │ vscode.lm.selectChatModels(...)       │
│  ┌──────────────────────────────────▼────────────────────────────────────┐  │
│  │ Copilot Language Model Bridge (Claude 3.5 Sonnet / GPT-4o / o1)       │  │
│  └───────────────────────────────────────────────────────────────────────┘  │
│                                                                             │
│  Zero-Footprint Storage:                                                    │
│   ~/.vscode/.../globalStorage/ (SQLite + Vector Embeddings + Graph Cache)   │
│   (Nothing committed or created in the workspace root)                      │
└─────────────────────────────────────────────────────────────────────────────┘

Key Features

1. Zero-Trace Code Knowledge Graph (Hybrid Graph-RAG):

   • Parses workspace symbols (functions, classes, interfaces, imports, and calls).
   • Generates lightweight embeddings and stores symbols + relationships in context.globalStorageUri via SQLite WASM (sql.js).
   • 0% repo trace: Never writes any cache or database file inside the repository.

2. Opportunistic MCP & Skill Discovery:

   • Read-only scanning for existing project configs:
     • .mcp.json or .mcp/
     • .gemini/skills/*/SKILL.md
     • .claude/mcp.json
     • .cursor/rules/ and .cursorrules
   • Connects via @modelcontextprotocol/sdk to execute MCP tools dynamically during agent execution.

3. Plan Mode with Interactive Visual Preview:

   • Creates a structured multi-task DAG before touching any code.
   • Shows affected files, dependencies, tools required, and risk levels.
   • Allows manual in-place editing of steps and instructions.
   • One-click transition: 🚀 Approve & Run Agent.

4. Agent Mode with LSP Diagnostic Self-Correction:

   • Streams model execution and tool calls in real-time.
   • Atomic file patches using apply_file_diff.
   • Automatically inspects language server diagnostics (vscode.languages.getDiagnostics) post-edit and triggers self-correction loops if syntax or type errors occur.

Getting Started

Development

# Install dependencies
npm install

# Run build (Extension bundle + Vite React webview)
npm run build

# Watch mode for extension & webview
npm run watch:ext
npm run watch:webview

Testing in VS Code

1. Open this repository in VS Code.
2. Press F5 to launch an Extension Development Host window.
3. Open the Better Than Copilot view in the Activity Bar or press Cmd+Shift+I (Ctrl+Shift+I).
4. Type an architectural prompt in Plan Mode to generate your first execution DAG!