Agent skill · software engineering · sundial-org
swift-concurrency-expert
Swift Concurrency review and remediation for Swift 6.2+. Use when asked to review Swift Concurrency usage, improve concurrency compliance, or fix Swift concurrency compiler errors in a feature or file.
Why this skill is useful
Provides specific patterns and fixes for Swift Concurrency issues that the AI wouldn't reliably generate on its own.
What it needs
About 1k tokens when loaded. Last updated 2026-03-07. 639 stars on the source repository.
What this skill does
Swift Concurrency Expert Attribution: copied from @Dimillian’s Dimillian/Skills (2025-12-31). Overview Review and fix Swift Concurrency issues in Swift 6.2+ codebases by applying actor isolation, Sendable safety, and modern concurrency patterns with minimal behavior changes. Workflow 1. Triage the issue Capture the exact compiler diagnostics and the offending symbol(s). Identify the current actor context (@MainActor, actor, nonisolated) and whether a default actor isolation mode is enabled. Confirm whether the code is UI-bound or intended to run off the main actor. 2. Apply the smallest safe fix Prefer edits that preserve existing behavior while satisfying data-race safety. Common fixes: UI-bound types: annotate the type or relevant members with @MainActor. Protocol conformance on main actor types: make the conformance isolated (e.g., extension Foo: @MainActor SomeProtocol). Global/static state: protect with @MainActor or move into an actor. Background work: move expensive work into a @concurrent async function on a nonisolated type or use an actor to guard mutable state. Sendable errors: prefer immutable/value types; add Sendable conformance only when correct; avoid @unchecked Sendable unless you can prove thread safety. Reference material See references/swift-6-2-concurrency.md for Swift 6.2 changes, patterns, and examples. See references/swiftui-concurrency-tour-wwdc.md for SwiftUI-specific concurrency guidance.
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills sundial-org/swift-concurrency-expert