SwiftUI & Swift 6 Structured Concurrency Standard

--- description: SwiftUI & Swift 6 Structured Concurrency Standard - Guardrails for native iOS with Swift 6: enforce Sendable conformance, replace ObservableObject with modern @Observable macro, and ensure @MainActor isolation for UI. globs: **/*.swift alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/swiftui-modern-concurrency" --- # SwiftUI & Swift 6 Structured Concurrency Standard > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: AI uses deprecated @ObservedObject / ObservableObject, causes data race compiler errors in Swift 6, or forgets @MainActor. ## System Constraints You are a native iOS engineer targeting iOS 17+ and Swift 6. Use the modern @Observable macro instead of legacy ObservableObject. All view models touching UI state must be marked @MainActor. Honor Swift 6 complete concurrency safety (Sendable types across actor boundaries). ## Strict Guidelines - Use @Observable instead of ObservableObject / @Published for automatic granular UI tracking. - Annotate ViewModels with @MainActor to guarantee all UI updates happen on the main thread. - Ensure types passed across Task boundaries conform to Sendable. ## Bad vs Good Implementations ### Modern Swift 6 @Observable with @MainActor Isolation #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Legacy ObservableObject triggers unnecessary full-view redraws and fails Swift 6 strict concurrency checks. ```swift // Deprecated iOS 16 ObservableObject pattern class UserViewModel: ObservableObject { @Published var username: String = "" func fetch() { DispatchQueue.global().async { // Risk of race conditions and missing main-thread dispatch self.username = "Alice" } } } ``` #### Production Standard (Correct) > **Standard**: Uses Swift 6 @Observable for zero-boilerplate field tracking and guarantees MainActor safety. ```swift // Production Standard: Swift 6 @Observable macro with MainActor import Observation import SwiftUI @Observable @MainActor final class UserViewModel { var username: String = "" var isLoading: Bool = false func fetchUser() async { isLoading = true defer { isLoading = false } // Automatically isolated to MainActor username = await UserService.shared.loadName() } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: SwiftUI & Swift 6 Structured Concurrency Standard

SwiftUI & Swift 6 Structured Concurrency Standard defines an industrial-grade behavioral standard for mobile engineering. Guardrails for native iOS with Swift 6: enforce Sendable conformance, replace ObservableObject with modern @Observable macro, and ensure @MainActor isolation for UI. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: AI uses deprecated @ObservedObject / ObservableObject, causes data race compiler errors in Swift 6, or forgets @MainActor. Without an explicit system instruction file, developers spend hours debugging silent failures.

Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	AI uses deprecated @ObservedObject / ObservableObject, causes data race compiler errors in Swift 6, or forgets @MainActor.	Critical	Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production. Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture Inconsistency	AI assistants produce mixed paradigms across files, creating fragmented codebase conventions.	Medium	Increases cognitive load during code reviews and leads to maintenance debt across engineering teams. Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.

Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

Use @Observable instead of ObservableObject / @Published for automatic granular UI tracking.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.

Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.

Annotate ViewModels with @MainActor to guarantee all UI updates happen on the main thread.

Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.

Ensure types passed across Task boundaries conform to Sendable.

Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.

Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is SwiftUI & Swift 6 Structured Concurrency Standard critical for AI coding assistants?

Guardrails for native iOS with Swift 6: enforce Sendable conformance, replace ObservableObject with modern @Observable macro, and ensure @MainActor isolation for UI. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (AI uses deprecated @ObservedObject / ObservableObject, causes data race compiler errors in Swift 6, or forgets @MainActor.) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.