SwiftData Pro skill for Claude: review and write SwiftData code

Makes Claude write and review SwiftData code against Paul Hudson's rules, aimed at the mistakes AI assistants often make.

Installs: 9.5K; on skills.sh
Stars: 458; on GitHub
Files: 8; besides SKILL.md
Updated: Oct 2026; last repo commit

Ask Claude to review your project and it checks the code against five reference files: core rules, predicates, CloudKit, indexing (iOS 18+) and class inheritance (iOS 26+). It reports only real problems, grouped by file, each with the rule broken and a before and after fix.

Ask it to write or improve code and it follows the same rules but makes the changes directly. SKILL.md targets Swift 6.2 or later and says to prefer SwiftData over Core Data. The folder bundles no scripts.

Good for

iOS and macOS developers who use SwiftData with an AI assistant
Teams reviewing @Model, @Query and predicate code
Projects that use CloudKit sync, indexes or model subclasses

Install swiftdata-pro

Claude Code

Copy this prompt.

Install the swiftdata-pro skill in Claude Code. Run this command:

/plugin marketplace add twostraws/SwiftData-Agent-Skill
/plugin install swiftdata-pro@swiftdata-agent-skill

Then check that it loaded and tell me how to use it.

2
Paste it into Claude Code. It shows the change and asks before running it.

Pick one route. The plugin route (Claude Code) and the skills CLI route both come from the README. The skills CLI needs Node.js; the README suggests brew install node if npx is missing. Choose which agents and whether to install per project or for all projects when the installer asks.

From the project README. Source.

What's in the skill

When it loads

Writes, reviews, and improves SwiftData code using modern APIs and best practices. Use when reading, writing, or reviewing projects that use SwiftData.

Sections in SKILL.md

Core Instructions
Output Format
Destination.swift
DestinationListView.swift
Summary
References

Key facts

Author: Paul Hudson (named in SKILL.md metadata)
License: MIT
Installs on skills.sh: 9,455 (Nov 2, 2026)
GitHub stars: 458 for the whole twostraws/swiftdata-agent-skill repo (Nov 2, 2026)
Last repo commit: Oct 19, 2026
Audits on skills.sh: Gen Agent Trust Hub: pass, Socket: pass, Snyk: pass
What it includes: 9 files including SKILL.md: 5 reference files, an agents/openai.yaml, 2 icon files (no scripts)
Targets: Swift 6.2 or later; iOS 26 and later for the full rule set
Part of: The swiftdata-pro plugin in the swiftdata-agent-skill marketplace

What it includes

Autosave, relationships, delete rules, property limits
references/core-rules.md covers autosaving, relationships, delete rules, property restrictions and FetchDescriptor optimization. Example rule: place @Relationship on one side only.
Try: “Use SwiftData Pro to review my project.”
Read · Core rules
Supported operations and ones that crash
references/predicates.md lists supported predicate operations, dangerous patterns that crash at runtime and unsupported methods, for example String.hasSuffix().
Read · Predicates
Constraints when the project syncs with iCloud
references/cloudkit.md: no @Attribute(.unique) or #Unique, defaults or optionals on every property, and optional relationships.
Try: “Use the SwiftData Pro skill to enable iCloud support in this project.”
Read · CloudKit
Where single and compound indexes help
Checked only when the project targets iOS 18 or later.
Read · Indexing (iOS 18+)
Model subclassing, schema setup and predicates
Checked only when the project targets iOS 26 or later.
Read · Class inheritance (iOS 26+)
Findings by file with rule and before/after fix
For each issue: file and lines, the rule broken, a short before and after. Files with no issues are skipped, and a prioritized summary comes last.
Read · Review output
Edits your SwiftData code directly
When you ask Claude to write or improve code instead of reviewing, SKILL.md says to make the changes directly rather than return a report.
Write · Write or improve mode

From the official docs

Permissions

Low risk

What it can do

Read your data
Create and change things
Delete things
Read-only mode

Watch out for

Write mode changes your files directly
SKILL.md says that when you ask it to write or improve code it makes the changes directly. Commit first, or ask for a review report only. github.com

Security advisories

No published security advisories as of Nov 2, 2026.

Technical details

Turning on read-only	No read-only mode. Review requests return a findings report; write or improve requests make changes.
Sign-in and keys	No key or account.
Scopes	Reads your Swift project to review it Edits your SwiftData code when you ask it to write or improve code

Questions

What does SwiftData Pro do?

It makes Claude write and review SwiftData code using Paul Hudson's rules. It covers @Model, @Query, predicates, relationships, indexes, CloudKit and model inheritance, and reports only genuine problems.

How do I install it?

Use the install box at the top of this page. The README gives a plugin command for Claude Code and a skills CLI command for Codex, Gemini, Cursor and others.

How do I run it?

In Claude Code type /swiftdata-pro, optionally with an instruction such as "Check my code for latest API usage". In Codex use $swiftdata-pro. You can also say "Use the SwiftData Pro skill" in plain language.

Which iOS versions does it assume?

It targets Swift 6.2 or later. Indexing checks apply when the project targets iOS 18 or later and class inheritance checks apply for iOS 26 or later.

Will it change my code?

If you ask for a review, it returns findings by file. If you ask it to write or improve code, SKILL.md says it makes the changes directly. Commit first.

Is it safe?

The folder holds Markdown, a YAML file and two icon files, with no scripts. In write mode it edits your code, so keep your work committed and read the diff.

Why not just use Core Data?

SKILL.md says the user strongly prefers SwiftData and tells Claude not to suggest Core Data unless a feature cannot be solved with SwiftData.

Information

updated Nov 2, 2026

Repository: twostraws/swiftdata-agent-skill
Folder: swiftdata-pro

twostraws/swiftdata-agent-skill skills.sh

Sources

Docs, issue trackers and discussions this page is built from.

Show all 8

swiftdata-pro SKILL.md · github.com
SwiftData Agent Skill README · github.com
swiftdata-agent-skill marketplace.json · github.com
core-rules.md · github.com
predicates.md · github.com
cloudkit.md · github.com
indexing.md · github.com
class-inheritance.md · github.com