Codebase Onboarding
Generate a comprehensive onboarding document for a codebase by exploring it in parallel.
Workflow
1. Launch Parallel Explorers
Spawn 5 explore subagents, each investigating a different area:
Agent 1 — Architecture & Structure
"Map the top-level directory structure. Identify the framework (Next.js, Express, Django, etc.), monorepo tools (turbo, nx), and key config files. List every app/package and what it does."
Agent 2 — Data Models & Database
"Find all database schemas, ORM models, migrations, and seed files. List every entity, its fields, and relationships. Identify the database (Postgres, MySQL, MongoDB, etc.) and ORM (Prisma, Drizzle, SQLAlchemy, etc.)."
Agent 3 — API Routes & Endpoints
"Find all API route definitions. List every endpoint with its HTTP method, path, auth requirements, and what it does. Identify the API style (REST, GraphQL, tRPC)."
Agent 4 — Authentication & Authorization
"Find how auth works. Identify the auth provider (Auth.js, Clerk, Supabase Auth, custom), session management, protected routes, role/permission checks, and middleware."
Agent 5 — Deployment & Infrastructure
"Find deployment config (Dockerfile, Vercel config, fly.toml, terraform), CI/CD pipelines (GitHub Actions, etc.), environment variables needed, and how to run the app locally."
2. Synthesize
Combine the results from all 5 agents into a single onboarding document:
# Codebase Onboarding
## Quick Start
1. Clone the repo
2. Install dependencies: `<command>`
3. Set up environment: copy `.env.example` to `.env`
4. Run database migrations: `<command>`
5. Start dev server: `<command>`
## Architecture
<Agent 1 findings>
## Data Models
<Agent 2 findings>
## API Reference
<Agent 3 findings>
## Authentication
<Agent 4 findings>
## Deployment
<Agent 5 findings>
## Key Files to Know
- `<file>` — <why it matters>3. Save
Write the document to ONBOARDING.md in the project root, or wherever the user specifies.
Tips
- Each explore agent is read-only and fast — the whole process takes under a minute
- For monorepos, consider one additional agent per app/package
- The document should be opinionated — highlight the "start here" files, not just list everything
- Include gotchas: common setup issues, env vars that are easy to forget, required system dependencies