How to use the Swift Concurrency Expert agent skill

What the skill makes the agent do

Swift has rules that stop code from running into data races when work happens on several threads at once. Without the skill, an agent may simply silence a compiler error. With the skill installed, the agent follows a structured process: it captures the exact diagnostic, identifies the offending symbols and the actor they belong to (such as @MainActor, an actor, or nonisolated), and then applies the smallest change that keeps behavior the same.

• Triage: record the exact compiler diagnostics and the symbols involved, and check whether the code is UI-bound or meant to run off the main actor.
• Smallest safe fix: for example annotating a UI-bound type with @MainActor, or moving expensive work into a @concurrent async function.
• Sendable guidance: prefer immutable value types and avoid @unchecked Sendable unless thread safety can be proven.
• Reference notes: Swift 6.2 concurrency changes and SwiftUI concurrency guidance for the agent to consult.

Install the skill from the ZIP

Download the ZIP for this skill from this page and unzip it. The skill is a folder containing SKILL.md, references/swift-6-2-concurrency.md and references/swiftui-concurrency-tour-wwdc.md. Put the unzipped folder in one of two places: ~/.claude/skills/ to make it available to you across projects, or a project's .claude/skills/ folder to make it available only inside that project.

You can also upload the ZIP in the Claude apps under Settings → Capabilities → Skills.

• Personal install: place the folder in ~/.claude/skills/.
• Project install: place the folder in the project's .claude/skills/ directory.
• Claude apps: Settings → Capabilities → Skills, then upload the ZIP.

How to trigger the skill with natural requests

You do not need a special command. Describe the problem in plain language and include the exact compiler message if you have it. The skill is written for Swift 6.2+ codebases, so mention your Swift version if it matters. The skill's own description covers Swift concurrency review and fixes for compiler errors, Sendable, isolation and remediation, so requests about those topics are the ones it is built for.

• "Fix this Sendable error after I moved the project to Swift 6."
• "Why does this view model need @MainActor? The compiler says it is isolated."
• "Review this file for actor isolation problems and make the smallest fix."
• "Explain why this closure captures main actor state unsafely."

What a good session looks like

Give the agent the diagnostic and the code. Expect it to name the actor context first, then propose a targeted change. Ask it to explain the reason for each fix, because the skill is designed to teach why a fix is needed rather than only silence the compiler.

Read every change before accepting it. Review any use of @unchecked Sendable with care, since the skill warns against it unless thread safety can be proven.

Requirements, scripts and network use

The skill lists no required tools. It does not run scripts and does not use the network, according to its listing. Its contents are Markdown instructions and reference notes. The skill's source is MIT licensed.

• Requires: nothing listed.
• Runs scripts: no.
• Uses network: no.
• Attribution: the SKILL.md notes it was copied from @Dimillian's Dimillian/Skills.

When not to use it

The skill does not apply to projects that do not use Swift. The advice on newer @concurrent patterns may not compile in codebases that are not on Swift 6.2, so check your toolchain before applying those changes.

• Non-Swift projects such as JavaScript or Python.
• Codebases not on Swift 6.2 when using @concurrent patterns.
• Blindly suppressing warnings with @unchecked Sendable.