Swift Concurrency Agent Skill

Expert guidance for any AI coding tool that supports the Agent Skills open format — safe concurrency, performance, and Swift 6+ migration.

Based on the comprehensive Swift Concurrency Course, distilled into actionable, concise references for agents.

Who this is for

• Teams migrating to Swift 6 / strict concurrency who need safe defaults and quick triage.
• Developers debugging data races, isolation errors, or flaky async tests.
• Anyone wanting performance-minded concurrency patterns (actors, tasks, Sendable, async streams).

How to Use This Skill

Option A: Using skills.sh (recommended)

Install this skill with a single command:

npx skills add https://github.com/avdlee/swift-concurrency-agent-skill --skill swift-concurrency

For more information, visit the skills.sh platform page.

Then use the skill in your AI agent, for example:

Use the swift concurrency skill and analyze the current project for Swift Concurrency improvements

Option B: Claude Code Plugin

Personal Usage

To install this Skill for your personal use in Claude Code:

1. Add the marketplace:

   /plugin marketplace add AvdLee/Swift-Concurrency-Agent-Skill
   

2. Install the Skill:

   /plugin install swift-concurrency@swift-concurrency-agent-skill
   

Project Configuration

To automatically provide this Skill to everyone working in a repository, configure the repository's .claude/settings.json:

{
  "enabledPlugins": {
    "swift-concurrency@swift-concurrency-agent-skill": true
  },
  "extraKnownMarketplaces": {
    "swift-concurrency-agent-skill": {
      "source": {
        "source": "github",
        "repo": "AvdLee/Swift-Concurrency-Agent-Skill"
      }
    }
  }
}

When team members open the project, Claude Code will prompt them to install the Skill.

Option C: Manual install

1. Clone this repository.
2. Install or symlink the swift-concurrency/ folder following your tool’s official skills installation docs (see links below).
3. Use your AI tool as usual and ask it to use the “swift-concurrency” skill for Swift Concurrency tasks.

Where to Save Skills

Follow your tool’s official documentation, here are a few popular ones:

• Codex: Where to save skills
• Claude: Using Skills
• Cursor: Enabling Skills

How to verify:

Your agent should reference the triage/playbook in swift-concurrency/SKILL.md and jump into the relevant reference file for your error or task.

What This Skill Offers

This skill gives your AI coding tool comprehensive Swift Concurrency guidance. It can:

Guide Your Concurrency Decisions

• Choose the right tool for the job (async/await, actors, tasks, task groups)
• Understand when to use @MainActor, custom actors, or nonisolated
• Navigate isolation domains and prevent data races at compile time
• Apply Sendable conformance correctly for value and reference types

Write Safe Concurrent Code

• Avoid common pitfalls like actor reentrancy and retain cycles
• Prevent data races with proper isolation
• Handle task cancellation and error propagation correctly
• Manage memory safely in concurrent contexts

Optimize Performance

• Choose between serialized, asynchronous, and parallel execution
• Reduce actor contention and unnecessary suspension points
• Understand the tradeoffs of parallelism

Migrate to Swift 6

• Step-by-step migration strategies for existing codebases
• Enable strict concurrency checking incrementally
• Rewrite closure-based code to async/await
• Migrate from Combine/RxSwift to Swift Concurrency
• Use migration tooling for upcoming Swift features

Test Concurrent Code

• Write reliable tests using Swift Testing (recommended) or XCTest
• Handle @MainActor isolation in tests
• Use withMainSerialExecutor for deterministic testing
• Avoid flaky tests with proper async handling

Integrate with Core Data

• Safely pass data between isolation domains using NSManagedObjectID
• Implement the Data Access Object (DAO) pattern
• Use custom actor executors when needed
• Avoid common Core Data concurrency pitfalls

What Makes This Skill Different

Expert Knowledge: Based on real-world experience migrating large produ

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