Swift

No scripts/. Process skills that may load with this one: load-with list.

Iron law

Optionals are the type. Value types until you need identity. No force-unwrap as a habit.

Tooling / verify

swift test
# or the Xcode test action the project uses

Idioms a linter misses

• let default. guard / if let over !.
• Struct/enum for data. Class when identity or shared mutation is required.
• Protocol + extension over deep class trees.
• Access control is part of the API (internal default is fine; public is a contract).

Errors

• throws / Result as the file already does.
• No try! on production paths.
• Typed errors that callers can switch on.

Concurrency

• Isolation is part of the type (@MainActor, Sendable).
• Do not cross isolation domains with unsound types.
• Task has a cancellation story. Do not ignore Task.checkCancellation.

Testing

• XCTest or Swift Testing as the package already uses.
• Test optionals via guard / #expect, not !.

PR review

• New ! / try!: reject without an invariant.
• New class: why not a struct?
• Retain cycles (self in escaping closures) named and broken ([weak self]).

Security

• Keychain / secrets as the app already does. No secrets in source.
• No string-built SQL or shell.
• URL / path inputs stay inside an allowlisted container.

Always

• let, guard, tests for the new branch.

Ask first

• New concurrency annotations in a file that does not use them.
• Mixing Objective-C in a Swift package.

Never

• ! and try! as the default.
• Retain cycles with no story.
• String-built SQL or shell.

Red flags

• "I'll force-unwrap, it's there"
• "class is simpler than struct"