Core Data Safety Audit

Scan your Swift codebase and Core Data models for the 5 most common Core Data issues that cause production crashes and data loss.

What This Command Checks

1. Schema Migration Safety — Missing lightweight migration options, schema version mismatches
2. Thread-Confinement Violations — NSManagedObject accessed from wrong threads
3. N+1 Query Patterns — Relationship access in loops without prefetching
4. Production Risk Patterns — Delete store patterns, missing migration testing
5. Performance Issues — Missing batch sizes, no faulting controls

When to Use

Run this command when:

• Adding new Core Data entities or attributes
• Before shipping production releases
• After seeing intermittent crashes in production
• When users report data loss or corruption
• Before migrating to a new Core Data schema version

Issue Categories

🔴 Critical Issues (Crashes/Data Loss)

Schema Migration Safety

• Missing NSMigratePersistentStoresAutomaticallyOption
• Store deletion without migration path (100% data loss)
• Schema changes without version increments

Thread-Confinement Violations

• NSManagedObject accessed outside perform/performAndWait
• Objects passed between threads or actors
• Background fetch without proper context usage

🟡 Medium Priority (Performance)

N+1 Query Patterns

• Relationship access inside loops
• Missing relationshipKeyPathsForPrefetching
• Fetch requests that trigger hundreds of queries

Production Risk Patterns

• Hard-coded store paths
• Missing migration unit tests
• No rollback strategy for failed migrations

🟢 Low Priority (Optimization)

Performance Issues

• Missing fetch batch sizes
• No faulting controls on large datasets
• Inefficient predicate patterns

Running the Audit

# In Claude Code
/audit-core-data

The command will:

1. Find all Swift files and Core Data models
2. Scan for the 5 issue categories above
3. Report findings with file:line references
4. Prioritize by severity (Critical → Low)
5. Link to relevant sections in the core-data-diag skill

Example Output

🔴 CRITICAL: Schema Migration Safety (3 issues)
  - AppDelegate.swift:45 - Missing migration options
  - CoreDataStack.swift:23 - Store deletion detected
  - User.xcdatamodeld — Schema version not incremented

🟡 MEDIUM: N+1 Query Patterns (7 issues)
  - UserListView.swift:67 - Relationship access in loop
  - PostsViewController.swift:102 - Missing prefetch

🟢 LOW: Performance Issues (2 issues)
  - FetchController.swift:34 - Missing batch size

Next Steps

After running the audit:

1. Fix Critical issues immediately — These cause production crashes
2. Review Medium issues — Address before next release
3. Document Low issues — Add to technical debt backlog

For detailed fix guidance, use the core-data-diag skill:

"How do I fix these Core Data migration issues?"

The skill provides:

• Safe migration patterns
• Thread-confinement solutions
• N+1 query prevention
• Production crisis defense strategies

Real-World Impact

Before audit

• 2-5 hours debugging intermittent crashes
• Data loss discovered in production
• Migration failures affecting 500K+ users

After audit

• 2-5 minutes to identify issues
• Catch problems before production
• Proactive migration testing prevents data loss

Run this command before every release to catch Core Data regressions early.