Swift 6 + SwiftUI Concurrency Review Agent Skill

Review Swift 6 strict-concurrency and SwiftUI code for idiom and build-breaking issues - non-Sendable across actor boundaries, @MainActor…

Context cost
2k tokensestimated from the bundle, loaded when it triggers
Bundle
1 file · 8.1 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Review Swift 6 strict-concurrency and SwiftUI code for idiom and build-breaking issues - non-Sendable across actor boundaries, @MainActor witness vs nonisolated protocol requirements, Combine/ObservableObject usage, force-unwraps, #Predicate macro limits, the 6.3.x Binding IRGen crash, missing #if os() guards, and unsafe escape hatches. Reports file:line with the fix and the why.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

mobileswift

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md8.1 kB · preview
--- name: swift-concurrency-review argument-hint: "[path or files; default = changed files vs git]" allowed-tools: [Bash, Read, Glob, Grep] disable-model-invocation: true ---
9# Swift 6 + SwiftUI Concurrency Review
10
11You review Swift source for Swift 6 strict-concurrency correctness and SwiftUI idiom on modern iOS / macOS. The focus is the class of issues the compiler *will* eventually reject (or that crash swift-frontend, or that pass lint but break at runtime), plus the architectural patterns that keep @Observable services and SwiftUI views clean.
12
13Scope discipline: this is **not** a general bug hunt or a style cleanup. Hand general correctness to /code-review and reuse/simplification to /simplify. Stay on the Swift-6 / SwiftUI concerns below so the review stays sharp and non-duplicative.
14
15## What to review
16
17Default to the **changed** Swift files (git diff --name-only + staged + untracked *.swift). If $ARGUMENTS names a path or files, review those. If a KB exists at docs/kb/conventions/swift-6-patterns.md (or similar), read it first - the project may have its own codified rules that supersede the generic ones here.
18
19## Review dimensions
20
21For each, report file:line, the issue, the concrete fix, and a one-line why. Cite the compiler diagnostic text where it helps the user recognize it.
22
23### 1. Sendability across isolation boundaries
24
25- A type sent across an actor boundary (an endpoint body, a value captured into a detached Task, anything an actor method returns) must be Sendable. Endpoint bodies that cross the boundary need (any Encodable & Sendable)?, not bare any Encodable.
26- Domain models that drop Sendable (e.g. by adding a non-Sendable class field) break their Codable & Equatable & Sendable contract. Flag a new stored property that is a non-Sendable reference type.
27- CFString and most CoreFoundation types are **not** Sendable. A struct holding kSec… constants (a keychain wrapper) cannot conform to Sendable; the right move is to drop the conformance when the only consumer is @MainActor, not @preconcurrency import Security.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md1,106 words
Files1
LicenceMIT
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈140
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
1,885
on trigger
The instruction body, read only when the skill fires.
1.0%
of a 200k window
Ten skills this size would take about 10% of the window before you open a file.
050k100k150k200k context window

2k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Middling. Fine to keep on in a project where you use it weekly, worth unloading in one where you never do.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md asks for Bash, which can write files and reach the network alike, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

The allowed-tools line of this skill’s own SKILL.md asks for Bash, which could do either, so neither is ruled out. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

1 file, 8.1 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md8.1 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 1 file you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Swift 6 + SwiftUI Concurrency Review · 2k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/swift-6-swiftui-concurrency-review/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/swift-6-swiftui-concurrency-review" ] && { [ ! -e .claude/skills/swift-6-swiftui-concurrency-review ] || { mv .claude/skills/swift-6-swiftui-concurrency-review "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/swift-6-swiftui-concurrency-review" .claude/skills/ && echo "Installed .claude/skills/swift-6-swiftui-concurrency-review"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add charlesjones-dev/swift-6-swiftui-concurrency-review

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/swift-6-swiftui-concurrency-review/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/swift-6-swiftui-concurrency-review/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/swift-6-swiftui-concurrency-review" ] && { [ ! -e ~/.claude/skills/swift-6-swiftui-concurrency-review ] || { mv ~/.claude/skills/swift-6-swiftui-concurrency-review "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/swift-6-swiftui-concurrency-review" ~/.claude/skills/ && echo "Installed ~/.claude/skills/swift-6-swiftui-concurrency-review" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/swift-6-swiftui-concurrency-review/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where. It appears as swift-concurrency-review in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, swift-6-swiftui-concurrency-review.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referencecharlesjones-dev/swift-6-swiftui-concurrency-review

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

—no reviews yet

Nobody has reviewed this skill yet. The rating is the mean of the reviews written here, so there is none until somebody writes the first.

Sign in to review it

A review is tied to an account so it can be answered, edited and taken down by the person who wrote it.

Sign in
Who can post

Anybody with an account, one review each. It carries the version that was current when you wrote it, and the publisher may reply once.

Publisher
Servers0
Claim this skill