Is this skill compatible with older iOS versions?

Yes, it provides patterns for OSAllocatedUnfairLock for iOS 16-17 and modern Mutex/Atomic types for iOS 18+ and Swift 6.

When should I use Mutex instead of an Actor?

Use a Mutex for microsecond-level operations, protecting single properties, or shared modules where you need synchronous access without the overhead of an asynchronous actor hop.

Can I hold a lock across an 'await' point?

No, holding locks across suspension points creates a significant deadlock risk. This skill teaches you how to release locks before using 'await'.

What is the benefit of using Atomic types?

Atomic types allow for lock-free synchronization, which is ideal for high-frequency updates like counters or state flags where even a mutex might be too slow.

Why shouldn't I use os_unfair_lock directly in Swift?

Standard os_unfair_lock can be moved in memory by Swift's runtime, leading to undefined behavior. This skill promotes OSAllocatedUnfairLock, which ensures a stable heap-allocated address.

Axiom Synchronization

Name: Axiom Synchronization
Author: CharlesWiltgen

byCharlesWiltgen

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233

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Mobile Development

Implements high-performance thread-safe primitives and low-level synchronization for modern Swift and xOS development.

Axiom Synchronization provides specialized guidance and implementation patterns for low-level synchronization primitives in modern xOS (iOS, iPadOS, watchOS, tvOS) development. It bridges the gap between high-level Swift Actors and performance-critical code by offering battle-tested patterns for Mutex (iOS 18+), OSAllocatedUnfairLock (iOS 16+), and Atomic types. This skill is essential for developers building high-frequency counters, thread-safe caches, or performance-sensitive modules where the overhead of asynchronous actor hops must be avoided, all while maintaining strict deadlock prevention and Swift 6 concurrency safety.

Key Features

01Detailed decision tree for choosing between Actors, Mutexes, and Atomics

02Implementation patterns for Swift 6 Mutex and Synchronization framework

03Lock-free performance patterns using Atomic types and memory ordering

04Backward-compatible locking strategies using OSAllocatedUnfairLock for iOS 16+

05Deadlock prevention rules for mixing locks with Swift Concurrency

06233 GitHub stars

Use Cases

01Creating thread-safe wrappers for shared state across Swift concurrency boundaries

02Building high-frequency, lock-free counters and flags using atomic operations

03Optimizing performance-critical hot paths by replacing actors with synchronous mutexes

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add charleswiltgen/axiom axiom-synchronization

For use in Claude.ai and ChatGPT

Download Skill