swift-concurrency-expert

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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.

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Sourcesteipete/agent-scripts

Added on2026-02-16

NPX Install

npx skill4agent add steipete/agent-scripts swift-concurrency-expert

SKILL.md Content

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.