Codebase Onboarding

Runs reconnaissance on an unfamiliar codebase without reading every file, maps the architecture, detects conventions from git history and code patterns, then generates both a scannable onboarding guide and a starter CLAUDE.md tailored to what it found. Use it when you first open a project with Claude Code or join a new repo. The four phase approach (reconnaissance, architecture mapping, convention detection, artifact generation) keeps it from hallucinating about structure. The best part is how it handles existing CLAUDE.md files by enhancing rather than replacing them, and it explicitly flags unknowns instead of guessing. Stays under 100 lines and focuses on what shapes how you write code, not listing every dependency.

skills.sh installs: 6.4K
GitHub stars: 300.3K
last updated: Aug 21, 2026

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Install

$ npx -y skills add affaan-m/ecc --skill codebase-onboarding --agent claude-code

Installs into .claude/skills of the current project.

Files

Codebase Onboarding

Systematically analyze an unfamiliar codebase and produce a structured onboarding guide. Designed for developers joining a new project or setting up Claude Code in an existing repo for the first time.

When to Use

First time opening a project with Claude Code
Joining a new team or repository
User asks "help me understand this codebase"
User asks to generate a CLAUDE.md for a project
User says "onboard me" or "walk me through this repo"

How It Works

Phase 1: Reconnaissance

Gather raw signals about the project without reading every file. Run these checks in parallel:

1. Package manifest detection
   → package.json, go.mod, Cargo.toml, pyproject.toml, pom.xml, build.gradle,
     Gemfile, composer.json, mix.exs, pubspec.yaml

2. Framework fingerprinting
   → next.config.*, nuxt.config.*, angular.json, vite.config.*,
     django settings, flask app factory, fastapi main, rails config

3. Entry point identification
   → main.*, index.*, app.*, server.*, cmd/, src/main/

4. Directory structure snapshot
   → Top 2 levels of the directory tree, ignoring node_modules, vendor,
     .git, dist, build, __pycache__, .next

SKILL.md on GitHub