089 — Firebase Hosting Setup {DevOps}

Purpose

Configure and optimize Firebase Hosting for production-grade web applications. Set up rewrites for SPAs, custom domains, preview channels for PR review, and CDN cache policies for performance. [EXPLICIT]

Physics — 3 Immutable Laws

1. Law of CDN First: Every static asset is served from Firebase's global CDN. Cache headers maximize edge-hit ratio. Origin requests are minimized. [EXPLICIT]
2. Law of Immutable Deploys: Each deploy creates an immutable version. Rollback is instant via firebase hosting:channel:deploy or version rollback in console. [EXPLICIT]
3. Law of Preview Before Production: Every PR gets a preview channel URL. No code reaches production without visual verification on a preview deployment. [EXPLICIT]

Protocol

Phase 1 — Hosting Configuration

1. Configure firebase.json hosting section:
   • "public": "dist" — built output directory. [EXPLICIT]
   • "rewrites": [{"source": "**", "destination": "/index.html"}] — SPA routing. [EXPLICIT]
   • "redirects" — for legacy URL migrations (301 permanent). [EXPLICIT]
   • "headers" — cache control for assets, security headers (CSP, X-Frame-Options). [EXPLICIT]

Phase 2 — Custom Domain & SSL

1. Add custom domain in Firebase Console → Hosting → Custom Domains. [EXPLICIT]
2. Set A records and TXT verification in DNS provider. [EXPLICIT]
3. Firebase auto-provisions SSL certificate (Let's Encrypt). Wait for propagation (~24h). [EXPLICIT]
4. Verify HTTPS works. Configure www redirect if needed. [EXPLICIT]

Phase 3 — Preview Channels & Deploy

1. PR preview: firebase hosting:channel:deploy pr-$PR_NUMBER --expires 7d. [EXPLICIT]
2. Production deploy: firebase deploy --only hosting. [EXPLICIT]
3. Cache policy: "Cache-Control": "public, max-age=31536000" for hashed assets, "no-cache" for index.html. [EXPLICIT]

I/O

Input	Output
firebase.json hosting config	Configured rewrites, redirects, headers
Built dist/ directory	Deployed files on Firebase CDN
Custom domain + DNS records	SSL-enabled custom domain
PR number	Preview channel URL (expires in 7d)

Quality Gates — 5 Checks

1. SPA rewrite configured — all routes return index.html. [EXPLICIT]
2. Security headers present — CSP, X-Content-Type-Options, X-Frame-Options. [EXPLICIT]
3. Cache headers optimized — hashed assets get 1-year cache, HTML gets no-cache. [EXPLICIT]
4. Custom domain SSL active — HTTPS enforced, no mixed content. [EXPLICIT]
5. Preview channels work — PR deploys produce accessible preview URLs. [EXPLICIT]

Edge Cases

• Multi-site hosting: Use "site" field in firebase.json for multiple sites in one project.
• Cloud Functions rewrites: "rewrites": [{"source": "/api/**", "function": "api"}] for SSR or API.
• i18n routing: Configure "i18n" in hosting config for language-based content serving.
• Large files: Firebase Hosting has 2GB per-file limit. Use Storage for larger assets.

Self-Correction Triggers

• 404 on refresh → SPA rewrite missing. Add catch-all rewrite to index.html.
• Stale content after deploy → index.html has aggressive cache. Set no-cache on HTML.
• SSL not provisioning → DNS records incorrect. Verify A record and TXT record values.
• Preview channel expired → increase --expires duration or redeploy.

Usage

Example invocations:

• "/firebase-hosting-setup" — Run the full firebase hosting setup workflow
• "firebase hosting setup on this project" — Apply to current context

Assumptions & Limits

• Assumes access to project artifacts (code, docs, configs) [EXPLICIT]
• Requires English-language output unless otherwise specified [EXPLICIT]
• Does not replace domain expert judgment for final decisions [EXPLICIT]