Agent skill

codebase-onboarding

Codebase Onboarding

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npx add-skill https://github.com/LeoYeAI/openclaw-master-skills/tree/main/skills/codebase-onboarding

SKILL.md

Codebase Onboarding

Tier: POWERFUL
Category: Engineering
Domain: Documentation / Developer Experience


Overview

Analyze a codebase and generate comprehensive onboarding documentation tailored to your audience. Produces architecture overviews, key file maps, local setup guides, common task runbooks, debugging guides, and contribution guidelines. Outputs to Markdown, Notion, or Confluence.

Core Capabilities

  • Architecture overview — tech stack, system boundaries, data flow diagrams
  • Key file map — what's important and why, with annotations
  • Local setup guide — step-by-step from clone to running tests
  • Common developer tasks — how to add a route, run migrations, create a component
  • Debugging guide — common errors, log locations, useful queries
  • Contribution guidelines — branch strategy, PR process, code style
  • Audience-aware output — junior, senior, or contractor mode

When to Use

  • Onboarding a new team member or contractor
  • After a major refactor that made existing docs stale
  • Before open-sourcing a project
  • Creating a team wiki page for a service
  • Self-documenting before a long vacation

Codebase Analysis Commands

Run these before generating docs to gather facts:

bash
# Project overview
cat package.json | jq '{name, version, scripts, dependencies: (.dependencies | keys), devDependencies: (.devDependencies | keys)}'

# Directory structure (top 2 levels)
find . -maxdepth 2 -not -path '*/node_modules/*' -not -path '*/.git/*' -not -path '*/.next/*' | sort | head -60

# Largest files (often core modules)
find src/ -name "*.ts" -not -path "*/test*" -exec wc -l {} + | sort -rn | head -20

# All routes (Next.js App Router)
find app/ -name "route.ts" -o -name "page.tsx" | sort

# All routes (Express)
grep -rn "router\.\(get\|post\|put\|patch\|delete\)" src/routes/ --include="*.ts"

# Recent major changes
git log --oneline --since="90 days ago" | grep -E "feat|refactor|breaking"

# Top contributors
git shortlog -sn --no-merges | head -10

# Test coverage summary
pnpm test:ci --coverage 2>&1 | tail -20

Generated Documentation Template

README.md — Full Template

markdown
# [Project Name]

> One-sentence description of what this does and who uses it.

[![CI](https://github.com/org/repo/actions/workflows/ci.yml/badge.svg)](https://github.com/org/repo/actions/workflows/ci.yml)
[![Coverage](https://codecov.io/gh/org/repo/branch/main/graph/badge.svg)](https://codecov.io/gh/org/repo)

## What is this?

[2-3 sentences: problem it solves, who uses it, current state]

**Live:** https://myapp.com  
**Staging:** https://staging.myapp.com  
**Docs:** https://docs.myapp.com

---

## Quick Start

### Prerequisites

| Tool | Version | Install |
|------|---------|---------|
| Node.js | 20+ | `nvm install 20` |
| pnpm | 8+ | `npm i -g pnpm` |
| Docker | 24+ | [docker.com](https://docker.com) |
| PostgreSQL | 16+ | via Docker (see below) |

### Setup (5 minutes)

```bash
# 1. Clone
git clone https://github.com/org/repo
cd repo

# 2. Install dependencies
pnpm install

# 3. Start infrastructure
docker compose up -d   # Starts Postgres, Redis

# 4. Environment
cp .env.example .env
# Edit .env — ask a teammate for real values or see Vault

# 5. Database setup
pnpm db:migrate        # Run migrations
pnpm db:seed           # Optional: load test data

# 6. Start dev server
pnpm dev               # → http://localhost:3000

# 7. Verify
pnpm test              # Should be all green

Verify it works

  • http://localhost:3000 loads the app
  • http://localhost:3000/api/health returns {"status":"ok"}
  • pnpm test passes

Architecture

System Overview

Browser / Mobile
    │
    ▼
[Next.js App] ←──── [Auth: NextAuth]
    │
    ├──→ [PostgreSQL] (primary data store)
    ├──→ [Redis] (sessions, job queue)
    └──→ [S3] (file uploads)
         
Background:
[BullMQ workers] ←── Redis queue
    └──→ [External APIs: Stripe, SendGrid]

Tech Stack

Layer Technology Why
Frontend Next.js 14 (App Router) SSR, file-based routing
Styling Tailwind CSS + shadcn/ui Rapid UI development
API Next.js Route Handlers Co-located with frontend
Database PostgreSQL 16 Relational, RLS for multi-tenancy
ORM Drizzle ORM Type-safe, lightweight
Auth NextAuth v5 OAuth + email/password
Queue BullMQ + Redis Background jobs
Storage AWS S3 File uploads
Email SendGrid Transactional email
Payments Stripe Subscriptions
Deployment Vercel (app) + Railway (workers)
Monitoring Sentry + Datadog

Key Files

Path Purpose
app/ Next.js App Router — pages and API routes
app/api/ API route handlers
app/(auth)/ Auth pages (login, register, reset)
app/(app)/ Protected app pages
src/db/ Database schema, migrations, client
src/db/schema.ts Drizzle schema — single source of truth
src/lib/ Shared utilities (auth, email, stripe)
src/lib/auth.ts Auth configuration — read this first
src/components/ Reusable React components
src/hooks/ Custom React hooks
src/types/ Shared TypeScript types
workers/ BullMQ background job processors
emails/ React Email templates
tests/ Test helpers, factories, integration tests
.env.example All env vars with descriptions
docker-compose.yml Local infrastructure

Common Developer Tasks

Add a new API endpoint

bash
# 1. Create route handler
touch app/api/my-resource/route.ts
typescript
// app/api/my-resource/route.ts
import { NextRequest, NextResponse } from 'next/server'
import { auth } from '@/lib/auth'
import { db } from '@/db/client'

export async function GET(req: NextRequest) {
  const session = await auth()
  if (!session) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
  }
  
  const data = await db.query.myResource.findMany({
    where: (r, { eq }) => eq(r.userId, session.user.id),
  })
  
  return NextResponse.json({ data })
}
bash
# 2. Add tests
touch tests/api/my-resource.test.ts

# 3. Add to OpenAPI spec (if applicable)
pnpm generate:openapi

Run a database migration

bash
# Create migration
pnpm db:generate     # Generates SQL from schema changes

# Review the generated SQL
cat drizzle/migrations/0001_my_change.sql

# Apply
pnpm db:migrate

# Roll back (manual — inspect generated SQL and revert)
psql $DATABASE_URL -f scripts/rollback_0001.sql

Add a new email template

bash
# 1. Create template
touch emails/my-email.tsx

# 2. Preview in browser
pnpm email:preview

# 3. Send in code
import { sendEmail } from '@/lib/email'
await sendEmail({
  to: user.email,
  subject: 'Subject line',
  template: 'my-email',
  props: { name: "username"
})

Add a background job

typescript
// 1. Define job in workers/jobs/my-job.ts
import { Queue, Worker } from 'bullmq'
import { redis } from '@/lib/redis'

export const myJobQueue = new Queue('my-job', { connection: redis })

export const myJobWorker = new Worker('my-job', async (job) => {
  const { userId, data } = job.data
  // do work
}, { connection: redis })

// 2. Enqueue
await myJobQueue.add('process', { userId, data }, {
  attempts: 3,
  backoff: { type: 'exponential', delay: 1000 },
})

Debugging Guide

Common Errors

Error: DATABASE_URL is not set

bash
# Check your .env file exists and has the var
cat .env | grep DATABASE_URL

# Start Postgres if not running
docker compose up -d postgres

PrismaClientKnownRequestError: P2002 Unique constraint failed

User already exists with that email. Check: is this a duplicate registration?
Run: SELECT * FROM users WHERE email = 'test@example.com';

Error: JWT expired

bash
# Dev: extend token TTL in .env
JWT_EXPIRES_IN=30d

# Check clock skew between server and client
date && docker exec postgres date

500 on /api/* in local dev

bash
# 1. Check terminal for stack trace
# 2. Check database connectivity
psql $DATABASE_URL -c "SELECT 1"
# 3. Check Redis
redis-cli ping
# 4. Check logs
pnpm dev 2>&1 | grep -E "error|Error|ERROR"

Useful SQL Queries

sql
-- Find slow queries (requires pg_stat_statements)
SELECT query, mean_exec_time, calls, total_exec_time
FROM pg_stat_statements
ORDER BY mean_exec_time DESC
LIMIT 20;

-- Check active connections
SELECT count(*), state FROM pg_stat_activity GROUP BY state;

-- Find bloated tables
SELECT relname, n_dead_tup, n_live_tup,
  round(n_dead_tup::numeric/nullif(n_live_tup,0)*100, 2) AS dead_pct
FROM pg_stat_user_tables
ORDER BY n_dead_tup DESC;

Debug Authentication

bash
# Decode a JWT (no secret needed for header/payload)
echo "YOUR_JWT" | cut -d. -f2 | base64 -d | jq .

# Check session in DB
psql $DATABASE_URL -c "SELECT * FROM sessions WHERE user_id = 'usr_...' ORDER BY expires_at DESC LIMIT 5;"

Log Locations

Environment Logs
Local dev Terminal running pnpm dev
Vercel production Vercel dashboard → Logs
Workers (Railway) Railway dashboard → Deployments → Logs
Database docker logs postgres (local)
Background jobs pnpm worker:dev terminal

Contribution Guidelines

Branch Strategy

main           → production (protected, requires PR + CI)
  └── feature/PROJ-123-short-desc
  └── fix/PROJ-456-bug-description
  └── chore/update-dependencies

PR Requirements

  • Branch name includes ticket ID (e.g., feature/PROJ-123-...)
  • PR description explains the why
  • All CI checks pass
  • Test coverage doesn't decrease
  • Self-reviewed (read your own diff before requesting review)
  • Screenshots/video for UI changes

Commit Convention

feat(scope): short description       → new feature
fix(scope): short description        → bug fix
chore: update dependencies           → maintenance
docs: update API reference           → documentation

Code Style

bash
# Lint + format
pnpm lint
pnpm format

# Type check
pnpm typecheck

# All checks (run before pushing)
pnpm validate

Audience-Specific Notes

For Junior Developers

  • Start with src/lib/auth.ts to understand authentication
  • Read existing tests in tests/api/ — they document expected behavior
  • Ask before touching anything in src/db/schema.ts — schema changes affect everyone
  • Use pnpm db:seed to get realistic local data

For Senior Engineers / Tech Leads

  • Architecture decisions are documented in docs/adr/ (Architecture Decision Records)
  • Performance benchmarks: pnpm bench — baseline is in tests/benchmarks/baseline.json
  • Security model: RLS policies in src/db/rls.sql, enforced at DB level
  • Scaling notes: docs/scaling.md

For Contractors

  • Scope is limited to src/features/[your-feature]/ unless discussed
  • Never push directly to main
  • All external API calls go through src/lib/ wrappers (for mocking in tests)
  • Time estimates: log in Linear ticket comments daily

Output Formats

→ See references/output-format-templates.md for details

Common Pitfalls

  • Docs written once, never updated — add doc updates to PR checklist
  • Missing local setup step — test setup instructions on a fresh machine quarterly
  • No error troubleshooting — debugging section is the most valuable part for new hires
  • Too much detail for contractors — they need task-specific, not architecture-deep docs
  • No screenshots — UI flows need screenshots; they go stale but are still valuable
  • Skipping the "why" — document why decisions were made, not just what was decided

Best Practices

  1. Keep setup under 10 minutes — if it takes longer, fix the setup, not the docs
  2. Test the docs — have a new hire follow them literally, fix every gap they hit
  3. Link, don't repeat — link to ADRs, issues, and external docs instead of duplicating
  4. Update in the same PR — docs changes alongside code changes
  5. Version-specific notes — call out things that changed in recent versions
  6. Runbooks over theory — "run this command" beats "the system uses Redis for..."

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