swift-concurrency

name	swift-concurrency
description	Implement or audit Swift 6.2 concurrency, MainActor default isolation, @concurrent work, Sendable dependencies, task ownership, cancellation, clocks, and race-free UI updates.
license	MIT
metadata	{"version":"1.0","provenance":"Adapted from twostraws Swift guidance and project-specific Swift 6 policy; see NOTICE.md."}

Swift concurrency

Read Package.swift and references/concurrency-checklist.md. Every target uses Swift 6 language mode with MainActor default isolation, InferIsolatedConformances, and NonisolatedNonsendingByDefault. Use this skill for every asynchronous service, observable model, stream, task group, actor, sendability, nonisolated, or @concurrent change.

Workflow

1. Identify mutable state and assign one isolation domain.
2. Keep UI-facing state on @MainActor.
3. Make dependency protocols and cross-task values Sendable.
4. Prefer structured async functions and task groups to callbacks or detached work.
5. Define which scope owns each Task and when cancellation occurs.
6. Propagate cancellation; do not convert it into a user-facing failure accidentally.
7. Prevent stale responses from overwriting newer state.
8. Inject clocks or continuations for deterministic tests instead of sleeping.