---

name: firebase-development-project-setup description: This skill should be used when initializing a new Firebase project with proven architecture. Triggers on "new firebase project", "initialize firebase", "firebase init", "set up firebase", "create firebase app", "start firebase project". Guides through CLI setup, architecture choices, and emulator configuration.

Firebase Project Setup

Overview

This sub-skill guides initializing a new Firebase project with proven architecture patterns. It handles Firebase CLI setup, architecture decisions, emulator configuration, and initial project structure.

Key principles:

• Use TypeScript for all functions
• Configure emulators from the start
• Choose architecture patterns early (hosting, auth, functions, security)
• Set up testing infrastructure immediately

When This Sub-Skill Applies

• Starting a brand new Firebase project
• Setting up Firebase for the first time in a repository
• User says: "new firebase project", "initialize firebase", "firebase init", "set up firebase"

Do not use for:

• Adding features to existing projects → firebase-development:add-feature
• Debugging existing setup → firebase-development:debug

Architecture Decisions

Use AskUserQuestion to gather these four decisions upfront:

1. Hosting Configuration

• Single Site - One hosting site, simple project
• Multiple Sites (site:) - Multiple independent URLs
• Multiple with Builds (target:) - Multiple sites with predeploy hooks

Reference: docs/examples/multi-hosting-setup.md

2. Authentication Approach

• API Keys - MCP tools, server-to-server, programmatic access
• Firebase Auth - User-facing app with login UI
• Both - Firebase Auth for web + API keys for tools

Reference: docs/examples/api-key-authentication.md

3. Functions Architecture

• Express API - Many related endpoints, need middleware, RESTful routing
• Domain Grouped - Feature-rich app with distinct areas (posts, admin)
• Individual Files - Independent functions, maximum modularity

Reference: docs/examples/express-function-architecture.md

4. Security Model

• Server-Write-Only (Preferred) - Cloud Functions handle all writes
• Client-Write - High-volume writes, need fastest UX, complex rules

Reference: docs/examples/firestore-rules-patterns.md

TodoWrite Workflow

Create checklist with these 14 steps:

Step 1: Verify Firebase CLI

firebase --version  # Install via npm install -g firebase-tools if missing
firebase login

Step 2: Create Project Directory

mkdir my-firebase-project && cd my-firebase-project
git init && git branch -m main

Create .gitignore with: node_modules/, .env, .env.local, .firebase/, lib/, dist/

Step 3: Run Firebase Init

firebase init

Select: Firestore, Functions, Hosting, Emulators. Choose TypeScript for functions.

Step 4: Gather Architecture Decisions

Use AskUserQuestion for the four decisions above.

Step 5: Configure firebase.json

Set up based on hosting decision. Critical emulator settings:

{
  "emulators": {
    "singleProjectMode": true,
    "ui": { "enabled": true, "port": 4000 }
  }
}

Reference: docs/examples/multi-hosting-setup.md

Step 6: Set Up Functions Structure

Based on architecture choice:

Express: Create middleware/, tools/, services/, shared/ Domain-Grouped: Create shared/types/, shared/validators/ Individual: Create functions/

Install dependencies: express, cors, firebase-admin, firebase-functions, vitest, biome

Step 7: Create Initial Functions Code

Create functions/src/index.ts with ABOUTME comments. Include health check endpoint for Express pattern.

Reference: docs/examples/express-function-architecture.md

Step 8: Configure Firestore Rules

Based on security model decision. Always include:

• Helper functions (isAuthenticated(), isOwner())
• Default deny rule at bottom

Reference: docs/examples/firestore-rules-patterns.md

Step 9: Set Up Testing

Create vitest.config.ts and vitest.emulator.config.ts. Set up __tests__/ and __tests__/emulator/ directories.

Step 10: Configure Biome

Create biome.json with recommended rules. Run npm run lint:fix.

Step 11: Set Up Environment Variables

Create .env.example template. Copy to .env and fill in values.

For hosting: create hosting/.env.local with NEXT_PUBLIC_USE_EMULATORS=true.

Step 12: Initial Git Commit

git add . && git commit -m "feat: initial Firebase project setup"

Step 13: Start Emulators

firebase emulators:start
open http://127.0.0.1:4000

Verify all services start. Test health endpoint if using Express.

Step 14: Create Initial Tests

Create functions/src/__tests__/setup.test.ts with basic verification. Run npm test.

Verification Checklist

Before marking complete:

• Firebase CLI installed and logged in
• TypeScript functions compile: npm run build
• All tests pass: npm test
• Linting passes: npm run lint
• Emulators start without errors
• Emulator UI accessible at http://127.0.0.1:4000
• Git initialized with commits
• .env files created and gitignored
• ABOUTME comments on all files
• Architecture decisions documented

Project Structures

Express API:

functions/src/
├── index.ts
├── middleware/apiKeyGuard.ts
├── tools/
├── services/
└── __tests__/

Domain-Grouped:

functions/src/
├── index.ts
├── posts.ts
├── users.ts
├── shared/types/
└── __tests__/

Individual Files:

functions/
├── functions/upload.ts
├── functions/process.ts
└── index.js

Next Steps

After setup complete:

1. Add first feature → firebase-development:add-feature
2. Review setup → firebase-development:validate
3. Debug issues → firebase-development:debug

Pattern References

• Hosting: docs/examples/multi-hosting-setup.md
• Auth: docs/examples/api-key-authentication.md
• Functions: docs/examples/express-function-architecture.md
• Rules: docs/examples/firestore-rules-patterns.md
• Emulators: docs/examples/emulator-workflow.md