Firebase Development

Firebase Development

Overview

This skill system guides Firebase development using proven patterns from production projects. It routes to specialized sub-skills based on detected intent.

Sub-skills:

• firebase-development:project-setup - Initialize new Firebase projects
• firebase-development:add-feature - Add functions/collections/endpoints
• firebase-development:debug - Troubleshoot emulator and runtime issues
• firebase-development:validate - Review Firebase code for security/patterns

When This Skill Applies

• Starting new Firebase projects
• Adding Cloud Functions or Firestore collections
• Debugging emulator issues or rule violations
• Reviewing Firebase code for security and patterns
• Setting up multi-hosting configurations
• Implementing authentication (API keys or Firebase Auth)

Routing Logic

Keywords by Sub-Skill

project-setup:

• "new firebase project", "initialize firebase", "firebase init"
• "set up firebase", "create firebase app", "start firebase project"

add-feature:

• "add function", "create endpoint", "new tool", "add api"
• "new collection", "add feature", "build", "implement"

debug:

• "error", "not working", "debug", "emulator issue"
• "rules failing", "permission denied", "troubleshoot", "deployment failed"

validate:

• "review firebase", "check firebase", "validate", "audit firebase"
• "look at firebase code", "security review"

Routing Process

• Analyze Request: Check for routing keywords
• Match Sub-Skill: Identify best match based on keyword density
• Announce: "I'm using the firebase-development:[sub-skill] skill to [action]"
• Route: Load and execute the sub-skill
• Fallback: If ambiguous, use AskUserQuestion with 4 options

Fallback Example

If intent is unclear, ask:

Question: "What Firebase task are you working on?"
Options:
  - "Project Setup" (Initialize new Firebase project)
  - "Add Feature" (Add functions, collections, endpoints)
  - "Debug Issue" (Troubleshoot errors or problems)
  - "Validate Code" (Review against patterns)

Reference Projects

Patterns are extracted from three production Firebase projects:

| Project | Path | Key Patterns |

|---------|------|--------------|

| oneonone | /Users/dylanr/work/2389/oneonone | Express API, custom API keys, server-write-only |

| bot-socialmedia | /Users/dylanr/work/2389/bot-socialmedia-server | Domain-grouped functions, Firebase Auth + roles |

| meme-rodeo | /Users/dylanr/work/2389/meme-rodeo | Individual function files, entitlements |

Pattern Summaries

Multi-Hosting Setup

Three options based on needs:

| Option | When to Use | Key Feature |

|--------|-------------|-------------|

| site: based | Multiple independent URLs | Simple, no build coordination |

| target: based | Need predeploy hooks | Build scripts run automatically |

| Single + rewrites | Smaller projects | All under one domain |

Details: See docs/examples/multi-hosting-setup.md

Authentication

| Pattern | When to Use | Example |

|---------|-------------|---------|

| Custom API keys | MCP tools, server-to-server | oneonone |

| Firebase Auth + roles | User-facing apps | bot-socialmedia |

| Hybrid | Both patterns needed | Web UI + API access |

Details: See docs/examples/api-key-authentication.md

Cloud Functions Architecture

| Pattern | When to Use | Structure |

|---------|-------------|-----------|

| Express app | API with middleware, routing | app.post('/mcp', handler) |

| Domain-grouped | Feature-rich apps | posts.ts, journal.ts |

| Individual files | Maximum modularity | One function per file |

Details: See docs/examples/express-function-architecture.md

Security Model

| Model | When to Use | Complexity |

|-------|-------------|------------|

| Server-write-only | Light-write apps, high security | Simple rules |

| Client-write + validation | High-volume writes, real-time | Complex rules |

Strongly prefer server-write-only for light-write applications.

Details: See docs/examples/firestore-rules-patterns.md

Emulator-First Development

Always develop locally with emulators:

firebase emulators:start
# Access UI at http://127.0.0.1:4000

Key settings in firebase.json:

• singleProjectMode: true - Essential for emulators to work together
• ui.enabled: true - Access debug UI

Details: See docs/examples/emulator-workflow.md

Modern Tooling Standards

All Firebase projects follow these standards:

| Tool | Purpose | Config File |

|------|---------|-------------|

| TypeScript | Type safety | tsconfig.json |

| vitest | Testing | vitest.config.ts |

| biome | Linting + formatting | biome.json |

ABOUTME Comment Pattern

Every TypeScript file starts with 2-line ABOUTME comment:

// ABOUTME: Brief description of what this file does
// ABOUTME: Second line with additional context

Testing Requirements

• Unit tests: Test handlers/utilities in isolation
• Integration tests: Test with emulators running
• Both required for every feature

Common Gotchas

| Issue | Solution |

|-------|----------|

| Emulator ports in use | lsof -i :5001, kill process |

| Admin SDK vs Client SDK | Admin bypasses rules, client respects rules |

| Cold start delays | First call takes 5-10s, normal |

| Data persistence | Use Ctrl+C (not kill) to export data |

| CORS in functions | app.use(cors({ origin: true })) |

Summary

This orchestrator routes to specialized sub-skills:

• Detects intent via keywords
• Routes to appropriate sub-skill
• Sub-skills use TodoWrite checklists
• All reference shared patterns in docs/examples/

Sub-Skills:

• firebase-development:project-setup - Initialize new projects
• firebase-development:add-feature - Add functions/collections
• firebase-development:debug - Troubleshoot issues
• firebase-development:validate - Review code