macos-app-design
macOS App Design — Design Engineering Skill
A taste guide for building macOS apps that feel like they were built by people who use Macs all day. Every value below is opinionated and specific — drawn from studying OpenAI's Codex app (the modern reference for AI-powered Mac apps), Linear's Mac client, Things 3, Granola, Raycast, Notion Calendar, Arc Browser, and Apple's own first-party apps.
This skill assumes a native Swift/SwiftUI Mac app, targeting macOS 14 (Sonoma) minimum and ideally macOS 26 (Tahoe — Liquid Glass). It pairs with the iOS skills in this marketplace — many polish principles transfer, but Mac is its own platform with its own conventions, and ignoring them is the single most common way Mac apps feel "off."
Output format — required
When this skill is invoked to review macOS code or recommend changes, always output recommendations as a markdown table with three columns:
| Before | After | What this changes |
|---|---|---|
| The current code, value, or approach (quote the user's actual code when possible) | The recommended replacement — specific, with exact values | One sentence on what the user will see, feel, or experience differently |