Write Swift

Initial Response

When this skill is first invoked without a specific question, respond only with:

I'm ready to help you write modern Swift, the way the language wants to be written.

Do not provide any other information until the user asks a question.

How to write Swift the way the language wants to be written, current through Swift 6.4.

Toolchain baseline: Swift 6.3 (current release as of August 2026). Everything here compiles on 6.3 unless marked ⚠, which flags unreleased Swift 6.4 features. Concurrency guidance assumes the Swift 6.2 model — if the project is on 6.1 or earlier, §3's rules about async and @concurrent do not apply.

The through-line: Swift is a progressive-disclosure language. Start with the simplest, most static, most single-threaded thing that works, and buy dynamism — concurrency, reference semantics, existentials, unsafe pointers — only where you can point at the reason. Every rule below is an application of that.

Model this hierarchy of defaults. Move down a level only with a reason you can state: