Sparkle Auto-Update for macOS Apps

This skill adds Sparkle auto-update support to a native macOS app. Sparkle is the standard open-source framework for macOS app updates outside the Mac App Store.

Overview

The implementation has 4 parts:

1. SPM dependency -- add the Sparkle package to the Xcode project
2. UpdaterManager.swift -- a singleton that wraps SPUStandardUpdaterController
3. Info.plist keys -- SUFeedURL and SUPublicEDKey
4. UI integration -- "Check for Updates" button in settings/menu bar

Step 1: Add Sparkle via SPM

In Xcode: File > Add Package Dependencies > enter:

https://github.com/sparkle-project/Sparkle

Use the "Up to Next Major Version" rule with 2.0.0. Add the Sparkle framework to your app target.

Or add it to Package.swift if your project uses one:

.package(url: "https://github.com/sparkle-project/Sparkle", from: "2.0.0")

Step 2: Create UpdaterManager.swift

Copy references/UpdaterManager.swift into your project. This is a singleton that:

• Creates SPUStandardUpdaterController early (before applicationDidFinishLaunching returns)
• Publishes canCheckForUpdates for UI binding
• Exposes automaticallyChecksForUpdates toggle
• Skips all update logic in DEBUG builds (so you don't get update prompts during development)
• For menu-bar-only apps: temporarily switches to .regular activation policy before showing the update window

The key design decisions in this file:

• startingUpdater: false in the initializer, then calling start() explicitly in applicationDidFinishLaunching. This gives you control over timing.
• DEBUG guards on start() and checkForUpdates(). Sparkle should never run in debug builds -- it would try to update your debug app with a release build.
• ObservableObject with @Published (not @Observable) because we need the Combine publisher(for:) bridge from Sparkle's KVO.