Agent guide for Swift and SwiftUI

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 iOS 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 iOS 26.0 or later. (Yes, it definitely exists.)
• Swift 6.2 or later, using modern Swift concurrency. Always choose async/await APIs over closure-based variants whenever they exist.
• SwiftUI backed up by @Observable classes for shared data.
• Do not introduce third-party frameworks without asking first.
• Avoid UIKit unless requested.

Swift instructions

• @Observable classes must be marked @MainActor unless the project has Main Actor default actor isolation. Flag any @Observable class missing this annotation.
• All shared data should use @Observable classes with @State (for ownership) and @Bindable / @Environment (for passing).
• Strongly prefer not to use ObservableObject, @Published, @StateObject, @ObservedObject, or @EnvironmentObject unless they are unavoidable, or if they exist in legacy/integration contexts when changing architecture would be complicated.
• 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.
• Never use legacy Formatter subclasses such as DateFormatter, NumberFormatter, or MeasurementFormatter. Always use the modern FormatStyle API instead. For example, to format a date, use myDate.formatted(date: .abbreviated, time: .shortened). To parse a date from a string, use Date(inputString, strategy: .iso8601). For numbers, use myNumber.formatted(.number) or custom format styles.

SwiftUI instructions

• Always use foregroundStyle() instead of foregroundColor().
• Always use `clipShape(.