Just shipped Rushi — my first iOS app, built solo with Codex over the past 4 months. Wanted to share what I learned, especially for anyone considering Codex as their primary coding partner for an iOS project.

Background

I'd never written Swift before. Started with Codex as my pair-programmer, learning Swift by doing as I built. The app is a Buddhist toolkit — sutra reader + 108-bead mala counter + sutra calligraphy practice. Free for the first week, then $1.99 — early users keep it free forever via App Store purchase history.

What worked surprisingly well with Codex

• SwiftUI scaffolding from natural-language descriptions — first iteration was usable; ~80% of layouts hit on first generation
• Localizing 17 languages — Codex generated all the .strings files from English seeds with cultural awareness (e.g. it correctly chose Vietnamese honorifics for Buddhist terms; same for Tibetan transliteration)
• SwiftData migration code when I changed schemas mid-project
• CoreText fallback chain for CJK fonts — UIFont in iOS 17 has bugs with Chinese serif fonts, and Codex correctly recommended bypassing it with CTFontDescriptor explicit fallback
• Apple Search Ads keyword research — Codex generated competitive keyword lists that matched what ASA actually showed as high-volume

Where I had to take over

• Apple-specific UX nuances (haptic timing, large title behavior, dynamic type quirks) — needed multiple rounds with screenshots
• Audio concurrency — Codex tended to over-engineer with actors when AVAudioPlayer would do
• App Store metadata (privacy labels, age rating) — Codex would sometimes suggest things that didn't match actual data flow ("data collection: false" while suggesting analytics SDK in another file)

Codex-specific tips for iOS solo devs

1. Show Codex the entire SwiftUI view file when iterating — partial context leads to half-broken layouts
2. When testing, paste the exact Xcode error text including line numbers — Codex maps stack traces well
3. For App Store review, ask Codex to write your privacy label statements based on your actual data flow, not your intent — it catches "I think we don't collect X" mistakes
4. Don't let Codex pick your dependency list — it prefers "popular" libraries over "minimal" ones; for a solo iOS app you want the latter

Outcome

• Apple review: 2 days, no rejections
• 17 UI languages, 9 full-text languages
• 0 crashes in TestFlight beta
• Open-sourced everything: sutra texts CC0 1.0, app source on GitHub
• Codex token usage during development: ~50M input tokens, ~3M output tokens

Repo (with the open-source sutra texts): github.com/hooosberg/Rushi

Vibe coding made me anxious; building this calmed me down. Happy to answer specific Codex/SwiftUI/CoreText questions in the comments.