swift-concurrency

name	swift-concurrency
promoted_to	swift
description	Swift concurrency: async/await, Actor, Task, Sendable patterns.
user-invocable	false
context	fork
agent	swift-general-engineer
routing	{"triggers":["swift concurrency","swift async await","Swift Actor","Swift Task group"],"not_for":"general Swift development (use swift-general-engineer agent) — this skill covers Swift concurrency patterns: actors, async/await, Sendable, structured concurrency","category":"swift","pairs_with":["swift-testing"]}

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 business logic and networking off the main actor.

References

• references/fundamentals.md -- async/await, Task, Sendable basics
• references/actor-isolation.md -- Actor, @MainActor, nonisolated
• references/task-patterns.md -- TaskGroup, AsyncSequence, AsyncStream, cancellation
• references/preferred-patterns.md -- blocking, leaking, reentrancy mistakes