axiom-ios-concurrency

# iOS Concurrency Router

**You MUST use this skill for ANY concurrency, async/await, threading, or Swift 6 concurrency work.**

## When to Use

Use this router when:
- Writing async/await code
- Seeing concurrency errors (data races, actor isolation)
- Working with @MainActor
- Dealing with Sendable conformance
- Optimizing Swift performance
- Migrating to Swift 6 concurrency
- **App freezes during loading** (likely main thread blocking)

## Conflict Resolution

**ios-concurrency vs ios-performance**: When app freezes or feels slow:
1. **Try ios-concurrency FIRST** — Main thread blocking is the #1 cause of UI freezes. Check for synchronous work on @MainActor before profiling.
2. **Only use ios-performance** if concurrency fixes don't help — Profile after ruling out obvious blocking.

**ios-concurrency vs ios-build**: When seeing Swift 6 concurrency errors:
- **Use ios-concurrency, NOT ios-build** — Concurrency errors are CODE issues, not environment issues
- ios-build is for "No such module", simulator issues, build failures unrelated to Swift language errors

**Rationale**: A 2-second freeze during data loading is almost always `await` on main thread or missing background dispatch. Domain knowledge solves this faster than Time Profiler.

## Routing Logic

### Swift Concurrency Issues

**Swift 6 concurrency patterns** → `/skill axiom-swift-concurrency`
- async/await patterns
- @MainActor usage
- Actor isolation
- Sendable conformance
- Data race prevention
- Swift 6 migration

**Swift performance** → `/skill axiom-swift-performance`
- Value vs reference types
- Copy-on-write optimization
- ARC overhead
- Generic specialization
- Collection performance

**Synchronous actor access** → `/skill axiom-assume-isolated`
- MainActor.assumeIsolated
- @preconcurrency protocol conformances
- Legacy delegate callbacks
- Testing MainActor code synchronously

**Thread-safe primitives** → `/skill axiom-synchronization`
- Mutex (iOS 18+)
- OSAllocatedUnfairLock (iOS 16+)
- Atomic