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swift-concurrency from velimirmueller/claude-development-skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
Use when diagnosing Swift Concurrency issues, refactoring callback-based code to async/await, or migrating to Swift 6 - tasks, actors, @MainActor, Sendable, data races and isolation errors.
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What the file says
# Swift Concurrency
## Fast Path
Before proposing a fix:
1. Analyze `Package.swift` or `.pbxproj` to determine Swift language mode, strict concurrency level, default isolation, and upcoming features. Do this always, not only for migration work.
2. Capture the exact diagnostic and offending symbol.
3. Determine the isolation boundary: `@MainActor`, custom actor, actor instance isolation, or `nonisolated`.
4. Confirm whether the code is UI-bound or intended to run off the main actor. When spawning unstructured tasks, inspect the synchronous prefix (everything before the first `await`): start on `@MainActor` only when that prefix truly needs main-actor access; otherwise use `Task { @concurrent in ... }` and hop back with `MainActor.run` only after the suspension. A trivial non-main line (for example, `print`) followed by main-actor work in the same prefix is not a reason to use `@concurrent`. For delayed retries, timers, and backoff tasks, separate the waiting from the UI mutation. The sleep often belongs off the main actor even when the final state update belongs on it.
Project settings that change concurrency behavior:
…
The line at the top of this page pins the label git:20261028.88809da, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
GET https://markdownregistry.com/api/v1/artifacts/art_zkctg3f63rvsk3pg
GET https://markdownregistry.com/api/v1/resolve?ref=velimirmueller/claude-development-skills/swift-concurrency
GET https://markdownregistry.com/api/v1/blob/ddfc575e2a4264c460f17540c9a35eb46bc514a0afd7ab6b9556b251208989fd
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velimirmueller/claude-skills · skills/swift/swift-concurrency/SKILL.md · Use when diagnosing Swift Concurrency issues, refactoring callback-based code to async/await, or migrating to Swift 6 -…
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