Swift Code Review Skill

Swift Code Review

Review Workflow

Follow this sequence in order. Do not emit findings until every Pass below is satisfied.

Swift / toolchain baseline — Establish language and tooling context: Package.swift // swift-tools-version and any per-target Swift language version or swiftSettings in the manifest; for Xcode, SWIFT_VERSION (or equivalent) in project or target build settings; note if review is single-file only.
Pass: You state a concrete Swift language version or mode (e.g. Swift 6 language mode, tools 5.10) before advice that depends on strict concurrency, migration-only syntax, or SDK availability.
Read surrounding code — For each changed .swift file, read the full enclosing type, function, method, or property that contains the edits, not only the diff hunk.
Pass: At least one full enclosing symbol (type or member) containing the change was read per changed file.
Scope the checklist — Using Quick Reference, decide which Review Checklist rows and references apply; open those reference files; skip rows clearly unrelated to the diff.
Pass: The review (or working notes) lists which checklist areas you applied, or marks areas N/A with a one-line reason tied to the diff (e.g. “no SwiftUI / @Observable in change”).
Pre-report verification — Load and follow review-verification-protocol.
Pass: That skill’s Hard gates (sequenced) are satisfied for each finding you will report (full symbol read, usage search before “unused”, caller checked before “missing handling”, severity calibrated, [FILE:LINE] proof).

Hard gates (same sequence, shorter)

| Step | Objective pass condition | | --- | --- | | 1 | Swift version/mode (or explicit single-file limitation) recorded before version- or SDK-gated advice. | | 2 | Full enclosing symbol read per changed file, not diff-only. | | 3 | Checklist areas + references listed or N/A with diff-tied reason. | | 4 | review-verification-protocol completed for every reported issue. |

Output format

Report findings as:

[FILE:LINE] ISSUE_TITLE
Severity: Critical | Major | Minor | Informational
Description of the issue and why it matters.

Quick Reference

| Issue Type | Reference | |------------|-----------| | async/await, actors, Sendable, Task | references/concurrency.md | | @Observable, @ObservationIgnored, @Bindable | references/observable.md | | throws, Result, try?, typed throws | references/error-handling.md | | Force unwraps, retain cycles, naming | references/common-mistakes.md |

Review Checklist

[ ] No force unwraps (!) on runtime data (network, user input, files)
[ ] Closures stored as properties use [weak self]
[ ] Delegate properties are weak
[ ] Independent async operations use async let or TaskGroup
[ ] Long-running Tasks check Task.isCancelled
[ ] Actors have mutable state to protect (no stateless actors)
[ ] Sendable types are truly thread-safe (beware @unchecked)
[ ] Errors handled explicitly (no empty catch blocks)
[ ] Custom errors conform to LocalizedError with descriptive messages
[ ] Nested @Observable objects are also marked @Observable
[ ] @Bindable used for two-way bindings to Observable objects

When to Load References

Reviewing async/await, actors, or TaskGroups → concurrency.md
Reviewing @Observable or SwiftUI state → observable.md
Reviewing error handling or throws → error-handling.md
General Swift review → common-mistakes.md

Review Questions

Are async operations that could run concurrently using async let?
Could actor state change across suspension points (reentrancy bug)?
Is @unchecked Sendable backed by actual synchronization?
Are errors logged and presented with helpful context?
Could any closure or delegate create a retain cycle?

Agent Skills: Swift Code Review

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