CloudKit Debugging Skill

This skill activates when you're working with CloudKit sync, sharing, schema, or CKRecord operations.

When This Skill Activates

Trigger this skill when the conversation involves:

• CloudKit sync failures or conflicts
• CKShare and sharing issues
• CloudKit schema or record type problems
• Change token management
• Zone operations
• Public/private database issues
• CloudKit quota or performance issues
• CKRecord field mapping errors

CloudKit Context for Cauldron

Container Setup

• Container ID: iCloud.Nadav.Cauldron
• Zones: Custom zones per feature (recipes, collections, connections)
• Databases: Private (user data) + Public (shared recipes)

Key Files to Check

• Cauldron/Core/Services/CloudKitService.swift - Main CloudKit operations (2,266 LOC)
• Cauldron/Core/Services/RecipeSyncService.swift - Recipe synchronization
• Cauldron/Core/Persistence/*Repository.swift - SwiftData ↔ CloudKit mapping
• Cauldron/Core/Services/ImageManager.swift - CKAsset handling

Common Cauldron CloudKit Patterns

• SwiftData models map to CD_* record types
• Actors for thread-safe CloudKit operations
• Manual sync triggers (no automatic background sync)
• CKAssets for images (recipes, profiles, collections)
• CloudKit sharing for collaborative collections

Debugging Process

1. Identify the Issue Category

Sync Issues:

• Records not syncing
• Conflicts and overwrites
• Change tokens not working
• Deleted items reappearing

Sharing Issues:

• Share creation fails
• Participants can't access shared data
• Permission errors
• Share acceptance problems

Schema Issues:

• Record type mismatches
• Missing fields
• Type conversion errors
• Index problems

Performance Issues:

• Slow queries
• Quota exceeded
• Batch operation failures
• Network timeout

2. Read Relevant Code

Always start by reading:

1. The CloudKit service implementation
2. The repository for the affected record type
3. Recent git changes related to CloudKit

git log --oneline --grep="CloudKit\|sync\|share" -20

3. Check for Common Issues

Change Token Problems:

// Look for: Are change tokens being saved?
// Look for: Is fetchChanges using the right token?
// Look for: Are tokens reset when needed?

Record Type Mismatches:

// SwiftData model: Recipe
// CloudKit record type: CD_Recipe
// Check: Do field names match?
// Check: Are types compatible (String, Int, Date, Data)?

Zone Configuration:

// Check: Is the custom zone created before use?
// Check: Are operations using the correct zone?
// Check: Is the zone subscription active?

Share Record Handling:

// Check: Is CKShare created with correct rootRecord?
// Check: Are participants added properly?
// Check: Is share record saved to public database?

4. Diagnostic Questions to Answer

Ask yourself:

• ✓ Is this happening in development, production, or both?
• ✓ Is it affecting all users or just some?
• ✓ What CloudKit database (private/public/shared)?
• ✓ What record types are involved?
• ✓ Are there any CloudKit errors in console logs?
• ✓ When did this start happening? (git blame)

5. Common CloudKit Errors & Solutions

CKError.serverRecordChanged

• Cause: Conflict - record modified elsewhere
• Solution: Implement conflict resolution, use change tags

CKError.zoneNotFound

• Cause: Custom zone not created or deleted
• Solution: Create zone before operations, handle zone deletion

CKError.unknownItem

• Cause: Record doesn't exist
• Solution: Check record existence before fetch/delete

CKError.partialFailure

• Cause: Batch operation partially failed
• Solution: Parse itemResults, retry failed items

CKError.quotaExceeded

• Cause: User's iCloud quota full
• Solution: Alert user, implement cleanup strategy

CKError.networkFailure/networkUnavailable

• Cause: No internet or CloudKit unavailable
• Solution: Queue operations, retry with backoff

6. Investigation Checklist

For sync issues:

□ Check change token persistence
□ Verify fetchChanges logic
□ Look for race conditions (actor isolation)
□ Check deleted item tracking (tombstones)
□ Verify record save order (dependencies)
□ Check predicate safety

For sharing issues:

□ Verify CKShare creation
□ Check rootRecord reference
□ Confirm public database save
□ Verify participant permissions
□ Check share URL generation
□ Test share acceptance flow

For schema issues:

□ Compare SwiftData model to CloudKit record type
□ Verify field name mappings
□ Check data type compatibility
□ Confirm required fields exist
□ Validate index configuration

CloudKit Best Practices for Cauldron

Record Operations

// ✅ DO: Use actors for thread safety
actor CloudKitService {
    func save(_ record: CKRecord) async throws { }
}

// ✅ DO: Batch operations when possible
let operation = CKModifyRecordsOperation(recordsToSave: records)

// ✅ DO: Handle partial failures
if case .partialFailure(let error) = ckError.code {
    // Process error.userInfo[CKPartialErrorsByItemIDKey]
}

// ❌ DON'T: Make CloudKit calls on main thread
// ❌ DON'T: Ignore CKError.serverRecordChanged
// ❌ DON'T: Save without checking quota first

Change Tracking

// ✅ DO: Persist change tokens
UserDefaults.standard.set(changeToken, forKey: "zoneChangeToken")

// ✅ DO: Handle moreComing flag
if changesResponse.moreComing {
    await fetchChanges(from: changesResponse.changeToken)
}

// ❌ DON'T: Forget to update token after successful fetch
// ❌ DON'T: Use same token across different zones

Sharing

// ✅ DO: Set share permissions explicitly
share[CKShare.SystemFieldKey.title] = "Recipe Collection"
share.publicPermission = .readOnly

// ✅ DO: Save share and root record atomically
let operation = CKModifyRecordsOperation(
    recordsToSave: [rootRecord, share]
)

// ❌ DON'T: Modify shared records without permission check
// ❌ DON'T: Share records across different zones

Debugging Tools

Console Logging

Add CloudKit debug logging:

// In CloudKitService
#if DEBUG
print("☁️ CloudKit: Fetching \(recordType) from \(database)")
#endif

CloudKit Dashboard

Check at: https://icloud.developer.apple.com/dashboard

• Verify schema matches code
• Check record counts
• View recent operations
• Monitor quota usage

Xcode Console Filters

Use these console filters:

• CloudKit - All CloudKit operations
• CKError - CloudKit errors only
• CD_Recipe - Specific record type operations

Output Format

When providing CloudKit debugging help:

1. Identify the Issue - State what CloudKit problem you found
2. Show Relevant Code - Reference specific files and lines
3. Explain Root Cause - Why is this happening?
4. Provide Solution - Code fix with explanation
5. Prevent Recurrence - Best practice to avoid this in future

Example:

🔍 **Issue Found:** CloudKit sync conflict in RecipeSyncService.swift:145

**Root Cause:** The service doesn't handle CKError.serverRecordChanged,
causing sync to fail when the recipe was modified on another device.

**Solution:** Implement conflict resolution using change tags...

**Prevention:** Always handle serverRecordChanged errors with merge strategy.

Remember

CloudKit debugging is systematic:

1. Read the error carefully
2. Check the code path
3. Verify CloudKit schema
4. Test incrementally
5. Use CloudKit Dashboard to validate

You have deep knowledge of Cauldron's CloudKit architecture - use it to solve problems quickly and thoroughly.