# Cloudkit

Implement, review, or improve CloudKit and iCloud sync in iOS/macOS apps.

- Repository: https://github.com/dpearson2699/swift-ios-skills (1266 stars)
- Category: Mobile
- License: see repository
- Last updated: 2026-07-31
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add dpearson2699/swift-ios-skills --skill cloudkit -g -a claude-code -y`
Codex: `npx skills add dpearson2699/swift-ios-skills --skill cloudkit -g -a codex -y`
Cursor: `npx skills add dpearson2699/swift-ios-skills --skill cloudkit -g -a cursor -y`
Gemini CLI: `npx skills add dpearson2699/swift-ios-skills --skill cloudkit -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add dpearson2699/swift-ios-skills`

## Description

Implement, review, or improve CloudKit and iCloud sync in iOS/macOS apps. Use when working with CKContainer, CKRecord, CKQuery, CKSubscription, CKSyncEngine, CKShare, NSUbiquitousKeyValueStore, or iCloud Drive file coordination; when syncing SwiftData models via ModelConfiguration with cloudKitDatabase; when handling CKError codes for conflict resolution, network failures, or quota limits; or when checking iCloud account status before performing sync operations.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# CloudKit

Sync data across devices using CloudKit, iCloud key-value storage, and iCloud
Drive. Covers container setup, record CRUD, queries, subscriptions, CKSyncEngine,
SwiftData integration, conflict resolution, and error handling.

## Contents

- [Container and Database Setup](#container-and-database-setup)
- [Workflow](#workflow)
- [CKRecord CRUD](#ckrecord-crud)
- [CKQuery](#ckquery)
- [CKSubscription](#cksubscription)
- [CKSyncEngine (iOS 17+)](#cksyncengine-ios-17)
- [SwiftData + CloudKit](#swiftdata--cloudkit)
- [NSUbiquitousKeyValueStore](#nsubiquitouskeyvaluestore)
- [iCloud Drive File Sync](#icloud-drive-file-sync)
- [Account Status and Error Handling](#account-status-and-error-handling)
- [Conflict Resolution](#conflict-resolution)
- [Common Mistakes](#common-mistakes)
- [Review Checklist](#review-checklist)
- [References](#references)

## Workflow

1. Choose the database scope and sync owner; verify capability, container, account status, schema, and environment before writing records.
2. Make a local change durable, enqueue it, then let subscriptions or `CKSyncEngine` drive remote work rather than polling.
3. Persist change tokens or sync-engine state after successful application.
4. Test offline edits, partial failure, rate limiting, token expiry, conflict, account loss, zone deletion, and relaunch.
5. On failure, classify the `CKError`, restore the affected fixture or queue item, apply the documented retry/reset/merge action, and rerun the same scenario. Never restart a full sync blindly after partial success.

Load [references/cloudkit-patterns.md](references/cloudkit-patterns.md) for incremental zone changes, shares, assets, batch operations, and Dashboard procedures.

## Container and Database Setup

Enable iCloud + CloudKit in Signing & Capabilities. A container provides three databases:

The rest: https://github.com/dpearson2699/swift-ios-skills/blob/HEAD/skills/cloudkit/SKILL.md