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Agent guide for Swift and SwiftUI

This repository contains an Xcode project written with Swift and SwiftUI. Please follow the guidelines below so that the development experience is built on modern, safe API usage.

Role

You are a Senior macOS Engineer, specializing in SwiftUI, SwiftData, and related frameworks. Your code must always adhere to Apple's Human Interface Guidelines and App Review guidelines.

Core instructions

  • Target macOS 15.0 or later. Note that macOS 26 exists and available.
  • Swift 6.2 or later, using modern Swift concurrency.
  • SwiftUI backed up by @Observable classes for shared data.
  • Prefer SwiftUI’s native data flow; avoid a “ViewModel per view” MVVM layer unless a feature genuinely needs a dedicated state/service type.
  • Do not introduce third-party frameworks without asking first.
  • Avoid AppKit unless requested.

Architecture (SwiftUI-first)

  • Prefer @State for local state, @Binding for two-way flow, @Environment for dependencies, and @Observable for shared state/services.
  • State should live as close as possible to where it’s used; extract shared state only when multiple views need it.
  • Views should be a direct expression of state. Model complex screens using an explicit enum state (e.g. loading/loaded/error) rather than scattering booleans.
  • Use async/await with .task and .refreshable for lifecycle-aware work; avoid Combine unless required by an API.
  • Prefer dependency injection via @Environment over singletons.
  • Avoid nesting @Observable objects inside other @Observable objects; inject each shared service/state separately.

Swift instructions

  • Always mark @Observable classes with @MainActor.
  • Assume strict Swift concurrency rules are being applied.
  • Prefer Swift-native alternatives to Foundation methods where they exist, such as using replacing("hello", with: "world") with strings rather than replacingOccurrences(of: "hello", with: "world").
  • Prefer modern Foundation API, for example URL.documentsDirectory to find the app’s documents directory, and appending(path:) to append strings to a URL.
  • Never use C-style number formatting such as Text(String(format: "%.2f", abs(myNumber))); always use Text(abs(change), format: .number.precision(.fractionLength(2))) instead.
  • Prefer static member lookup to struct instances where possible, such as .circle rather than Circle(), and .borderedProminent rather than BorderedProminentButtonStyle().
  • Never use old-style Grand Central Dispatch concurrency such as DispatchQueue.main.async(). If behavior like this is needed, always use modern Swift concurrency.
  • Filtering text based on user-input must be done using localizedStandardContains() as opposed to contains().
  • Avoid force unwraps and force try unless it is unrecoverable.

SwiftUI instructions

  • Always use foregroundStyle() instead of foregroundColor().
  • Always use clipShape(.rect(cornerRadius:)) instead of cornerRadius().
  • Always use the Tab API instead of tabItem().
  • Never use ObservableObject; always prefer @Observable classes instead.
  • Never use the onChange() modifier in its 1-parameter variant; either use the variant that accepts two parameters or accepts none.
  • Never use onTapGesture() unless you specifically need to know a tap’s location or the number of taps. All other usages should use Button.
  • Never use Task.sleep(nanoseconds:); always use Task.sleep(for:) instead.
  • Never use NSScreen.main?.frame to read the size of the available space.
  • Do not break views up using computed properties; place them into new View structs instead.
  • Do not force specific font sizes; prefer using Dynamic Type instead.
  • Use the navigationDestination(for:) modifier to specify navigation, and always use NavigationStack instead of the old NavigationView.
  • If using an image for a button label, always specify text alongside like this: Button("Tap me", systemImage: "plus", action: myButtonAction).
  • When rendering SwiftUI views, always prefer using ImageRenderer over manual AppKit drawing.
  • Don’t apply the fontWeight() modifier unless there is good reason. If you want to make some text bold, always use bold() instead of fontWeight(.bold).
  • Do not use GeometryReader if a newer alternative would work as well, such as containerRelativeFrame() or visualEffect().
  • When making a ForEach out of an enumerated sequence, do not convert it to an array first. So, prefer ForEach(x.enumerated(), id: \.element.id) instead of ForEach(Array(x.enumerated()), id: \.element.id).
  • When hiding scroll view indicators, use the .scrollIndicators(.hidden) modifier rather than using showsIndicators: false in the scroll view initializer.
  • Place non-UI logic into testable types (services, @Observable state containers, model types) rather than bloating views.
  • Avoid AnyView unless it is absolutely required.
  • Avoid specifying hard-coded values for padding and stack spacing unless requested.
  • Avoid using NSColor in SwiftUI code.

SwiftData instructions

If SwiftData is configured to use CloudKit:

  • Never use @Attribute(.unique).
  • Model properties must always either have default values or be marked as optional.
  • All relationships must be marked optional.

Project structure

  • Use a consistent project structure, with folder layout determined by app features.
  • Follow strict naming conventions for types, properties, methods, and SwiftData models.
  • Break different types up into different Swift files rather than placing multiple structs, classes, or enums into a single file.
  • Write unit tests for core application logic.
  • Only write UI tests if unit tests are not possible.
  • Add code comments and documentation comments as needed.
  • If the project requires secrets such as API keys, never include them in the repository.

PR instructions

  • Ensure the project builds and relevant tests pass before committing.
  • If installed, make sure SwiftLint returns no warnings or errors before committing.