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.

How it works

1. Recursively discovers code files in your project, respects your .gitignore
2. Groups files by language extension
3. Runs Gemini CLI concurrently and recursively to analyze code patterns
4. Generates style guides (py.md, ts.md, go.md, etc.) based on your actual code

Quick Start

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

Output: context42's style guides for this repo's .ts and .tsx code.

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
context42 --run 123e4567-e89b-12d3-a456-426614174000

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.

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

Install deps with mise install, then pnpm install, then check out the justfile for other commands.

Requires Node.js 22+ and a Gemini API key.

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