swift-concurrency

# Swift Structured Concurrency Pattern catalog for Swift's structured concurrency model: async/await, Actors, TaskGroups, AsyncSequence, Sendable, and cancellation. Load the reference file matching the developer's question. ## Reference Loading Table | Signal | Reference File | Content | |--------|---------------|---------| | async/await, Task, Sendable | references/fundamentals.md | async/await patterns, Task/Task.detached, Sendable/@Sendable | | Actor, @MainActor, nonisolated | references/actor-isolation.md | Actor isolation, MainActor UI confinement, nonisolated opt-out | | TaskGroup, AsyncSequence, AsyncStream, cancellation | references/task-patterns.md | Structured concurrency, rate-limited groups, streams, cancellation | | Failure modes, common mistakes | references/preferred-patterns.md | Blocking MainActor, task leaking, actor reentrancy hazard | ## Key Conventions - **Prefer structured concurrency** -- use `TaskGroup` over loose `Task { }` whenever possible; structured tasks propagate cancellation and errors automatically. - **Mark types Sendable** -- enable strict concurrency checking (`-strict-concurrency=complete`) and resolve all warnings before they become errors in Swift 6. - **Use actors for shared mutable state** -- avoid manual locks; actors provide compiler-verified safety. - **Cancel what you create** -- every `Task` stored in a property should have a corresponding cancellation path. - **Minimize @MainActor surface** -- isolate only the UI layer; keep...