context42

context42

The best code style guide is the one your team already follows. This tool discovers it.

Let a little AI magic loose in your repo: context42 explores your codebase, chats with Google Gemini, and conjures up custom style guides for every language it finds.

Quick Start

$ export GEMINI_API_KEY="..."
$ npx context42 # or bunx, pnpx, yarn dlx, requires Node ≥22.0

See context42's output on this repo in ./cursor/rules/

Usage

# Analyze current directory, saves results to ./context42/
context42

# Analyze specific directory
context42 -i src/

# Custom output location
context42 -o .cursor/rules/

# Set max concurrent Gemini processes (default: 4)
context42 --concurrency 8

# Resume from a previous run (useful for debugging)
context42 --run abc123-def456

Why

Every codebase has implicit style rules. The problem is they're locked in developers' heads.

New team members guess. PRs get bikeshedded. Time gets wasted on "should we use interface or type?" when the answer is already in your code—if you look at the patterns.

Context42 makes the implicit explicit. It reads your code like a new developer would, but with perfect memory and pattern recognition.

How it works

• Recursively discovers code files in your project
• Groups files by language extension
• Runs up to Gemini CLI concurrently to analyze code patterns
• Generates style guides (py.md, ts.md, go.md, etc.) based on your actual code

The output isn't aspirational—it's descriptive. This is how you actually write code.

New Features

• Automatic Cleanup: Temporary style files are automatically cleaned up after generation, ensuring no style.*.md files pollute your codebase
• Resume Capability: Failed runs can be resumed using --run with the previous run ID
• Improved File Naming: Style files now use a clearer naming pattern: style.{ext}.md (e.g., style.ts.md, style.py.md)

Architecture

flowchart TD
    A[CLI Entry Point] --> B[File Explorer]
    B --> C{Language Detection}
    C --> D[TypeScript Files]
    C --> E[Python Files]
    C --> F[Go Files]
    C --> G[Other Languages]

    D --> H[Task Queue]
    E --> H
    F --> H
    G --> H

    H --> I[Processor Pool]
    I --> J[Worker 1]
    I --> K[Worker 2]
    I --> L[Worker N]

    J --> M[Gemini API]
    K --> M
    L --> M

    M --> N[SQLite Cache]
    N --> O[Style Guide Generator]
    O --> P[Output Files]

    P --> Q[style.ts.md]
    P --> R[style.py.md]
    P --> S[style.go.md]

    style A fill:#f9f,stroke:#333,stroke-width:2px
    style M fill:#9f9,stroke:#333,stroke-width:2px
    style N fill:#99f,stroke:#333,stroke-width:2px

Development

pnpm install
pnpm dev          # Watch mode
pnpm test         # Run tests
pnpm build        # Build for production

Requires Node.js 20+ and a Gemini API key.

"Good code has a rhythm. This tool finds it."