monorepo-management – Coding skill for AI agents

Monorepo Management

Build efficient, scalable monorepos that enable code sharing, consistent tooling, and atomic changes across multiple packages and applications.

When to Use This Skill

• Setting up new monorepo projects
• Migrating from multi-repo to monorepo
• Optimizing build and test performance
• Managing shared dependencies
• Implementing code sharing strategies
• Setting up CI/CD for monorepos
• Versioning and publishing packages
• Debugging monorepo-specific issues

Core Concepts

1. Why Monorepos?

Advantages:

• Shared code and dependencies
• Atomic commits across projects
• Consistent tooling and standards
• Easier refactoring
• Simplified dependency management
• Better code visibility

Challenges:

• Build performance at scale
• CI/CD complexity
• Access control
• Large Git repository

2. Monorepo Tools

Package Managers:

• pnpm workspaces (recommended)
• npm workspaces
• Yarn workspaces

Build Systems:

• Turborepo (recommended for most)
• Nx (feature-rich, complex)
• Lerna (older, maintenance mode)

Turborepo Setup

Initial Setup

# Create new monorepo
npx create-turbo@latest my-monorepo
cd my-monorepo

# Structure:
# apps/
#   web/          - Next.js app
#   docs/         - Documentation site
# packages/
#   ui/           - Shared UI components
#   config/       - Shared configurations
#   tsconfig/     - Shared TypeScript configs
# turbo.json      - Turborepo configuration
# package.json    - Root package.json

Configuration

// turbo.json
{
  "$schema": "https://turbo.build/schema.json",
  "globalDependencies": ["**/.env.*local"],
  "tasks": {
    "build": {
      "dependsOn": ["^build"],
      "outputs": ["dist/**", ".next/**", "!.next/cache/**"]
    },
    "test": {
      "dependsOn": ["build"],
      "outputs": ["coverage/**"]
    },
    "lint": {
      "outputs": []
    },
    "dev": {
      "cache": false,
      "persistent": true
    },
    "type-check": {
      "dependsOn": ["^build"],
      "outputs": []
    }
  }
}

// package.json (root)
{
  "name": "my-monorepo",
  "private": true,
  "scripts": {
    "build": "turbo run build",
    "dev": "turbo run dev",
    "test": "turbo run test",
    "lint": "turbo run lint",
    "format": "prettier --write \"**/*.{ts,tsx,md}\"",
    "clean": "turbo run clean && rm -rf node_modules"
  },
  "devDependencies": {
    "turbo": "^2.0.0",
    "prettier": "^3.0.0",
    "typescript": "^5.0.0"
  },
  "packageManager": "[email protected]"
}

pnpm reads workspace packages only from pnpm-workspace.yaml, so declare them there (see references/details.md). Turborepo 2 renamed pipeline to tasks and rejects a turbo.json that still uses pipeline; run npx @turbo/codemod migrate to upgrade a 1.x config.

Package Structure

// packages/ui/package.json
{
  "name": "@repo/ui",
  "version": "0.0.0",
  "private": true,
  "main": "./dist/index.js",
  "types": "./dist/index.d.ts",
  "exports": {
    ".": {
      "import": "./dist/index.js",
      "types": "./dist/index.d.ts"
    },
    "./button": {
      "import": "./dist/button.js",
      "types": "./dist/button.d.ts"
    }
  },
  "scripts": {
    "build": "tsup src/index.ts --format esm,cjs --dts",
    "dev": "tsup src/index.ts --format esm,cjs --dts --watch",
    "lint": "eslint src/",
    "type-check": "tsc --noEmit"
  },
  "devDependencies": {
    "@repo/tsconfig": "workspace:*",
    "tsup": "^7.0.0",
    "typescript": "^5.0.0"
  },
  "dependencies": {
    "react": "^18.2.0"
  }
}

Detailed patterns and worked examples

Detailed pattern documentation lives in references/details.md. Read that file when the navigation tier above is insufficient.

Best Practices

1. Consistent Versioning: Lock dependency versions across workspace

2. Shared Configs: Centralize ESLint, TypeScript, Prettier configs

3. Dependency Graph: Keep it acyclic, avoid circular dependencies

4. Cache Effectively: Configure inputs/outputs correctly

5. Type Safety: Share types between frontend/backend

6. Testing Strategy: Unit tests in packages, E2E in apps

7. Documentation: README in each package

8. Release Strategy: Use changesets for versioning

Common Pitfalls

• Circular Dependencies: A depends on B, B depends on A
• Phantom Dependencies: Using deps not in package.json
• Incorrect Cache Inputs: Missing files in Turborepo inputs
• Over-Sharing: Sharing code that should be separate
• Under-Sharing: Duplicating code across packages
• Large Monorepos: Without proper tooling, builds slow down

Publishing Packages

# Using Changesets
pnpm add -Dw @changesets/cli
pnpm changeset init

# Create changeset
pnpm changeset

# Version packages
pnpm changeset version

# Publish
pnpm changeset publish

# .github/workflows/release.yml
- name: Create Release Pull Request or Publish
  uses: changesets/action@v1
  with:
    publish: pnpm release
  env:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
    NPM_TOKEN: ${{ secrets.NPM_TOKEN }}