Modern Swift

This covers Swift 6.2's strict concurrency model with async/await, actors, and Sendable constraints that catch data races at compile time. You'll want this when migrating from completion handlers to modern patterns, fixing Sendable errors, or wrangling shared state without locks. The reference guide is thorough on task groups, cancellation, and the actor re-entrancy gotchas that bite everyone. The real value is in the migration patterns and the blunt guidance on when not to reach for @unchecked Sendable as a quick fix. If you're still using DispatchQueue for everything or your codebase is drowning in completion handler pyramids, this walks through the proper modern alternatives.

skills.sh installs: 181
GitHub stars: 233
last updated: Aug 21, 2026

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Install

$ npx -y skills add johnrogers/claude-swift-engineering --skill modern-swift --agent claude-code

Installs into .claude/skills of the current project.

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Modern Swift (6.2+)

Swift 6.2 introduces strict compile-time concurrency checking with async/await, actors, and Sendable constraints that prevent data races at compile time instead of runtime. This is the foundation of safe concurrent Swift.

Overview

Modern Swift replaces older concurrency patterns (completion handlers, DispatchQueue, locks) with compiler-enforced safety. The core principle: if it compiles with strict concurrency enabled, it cannot have data races.

Quick Reference

Need	Use	NOT
Async operation	`async/await`	Completion handlers
Main thread work	`@MainActor`	`DispatchQueue.main`
Shared mutable state	`actor`	Locks, serial queues
Parallel tasks	`TaskGroup`	`DispatchGroup`
Thread safety	`Sendable`	`@unchecked` everywhere