iOS Data & Persistence Router

You MUST use this skill for ANY data persistence, database, axiom-storage, CloudKit, or serialization work.

When to Use

Use this router when working with:

• Databases (SwiftData, Core Data, GRDB, SQLiteData)
• Schema migrations
• CloudKit sync
• File storage (iCloud Drive, local storage)
• Data serialization (Codable, JSON)
• Storage strategy decisions

Routing Logic

SwiftData

Working with SwiftData → /skill axiom-swiftdata
Schema migration → /skill axiom-swiftdata-migration
Migration issues → /skill axiom-swiftdata-migration-diag
Migrating from Realm → /skill axiom-realm-migration-ref
SwiftData vs SQLiteData → /skill axiom-sqlitedata-migration

Other Databases

GRDB queries → /skill axiom-grdb
SQLiteData → /skill axiom-sqlitedata
Advanced SQLiteData → /skill axiom-sqlitedata-ref
Core Data patterns → /skill axiom-core-data
Core Data issues → /skill axiom-core-data-diag

Migrations

Database migration safety → /skill axiom-database-migration (critical - prevents data loss)

Serialization

Codable issues → /skill axiom-codable

Cloud Storage

Cloud sync patterns → /skill axiom-cloud-sync
CloudKit → /skill axiom-cloudkit-ref
iCloud Drive → /skill axiom-icloud-drive-ref
Cloud sync errors → /skill axiom-cloud-sync-diag

File Storage

Storage strategy → /skill axiom-storage
Storage issues → /skill axiom-storage-diag
Storage management → /skill axiom-storage-management-ref
File protection → /skill axiom-file-protection-ref

Decision Tree

1. SwiftData? → swiftdata, swiftdata-migration
2. Core Data? → core-data, core-data-diag
3. GRDB? → grdb
4. SQLiteData? → sqlitedata, sqlitedata-ref
5. ANY schema migration? → database-migration (ALWAYS — prevents data loss)
6. Realm migration? → realm-migration-ref
7. SwiftData vs SQLiteData? → sqlitedata-migration
8. Cloud sync architecture? → cloud-sync
9. CloudKit? → cloudkit-ref
10. iCloud Drive? → icloud-drive-ref
11. Cloud sync errors? → cloud-sync-diag
12. Codable/JSON serialization? → codable
13. File storage strategy? → storage, storage-diag, storage-management-ref
14. File protection? → file-protection-ref

Anti-Rationalization

Thought	Reality
"Just adding a column, no migration needed"	Schema changes without migration crash users. database-migration prevents data loss.
"I'll handle the migration manually"	Manual migrations miss edge cases. database-migration covers rollback and testing.
"Simple query, I don't need the skill"	Query patterns prevent N+1 and thread-safety issues. The skill has copy-paste solutions.
"CloudKit sync is straightforward"	CloudKit has 15+ failure modes. cloud-sync-diag diagnoses them systematically.
"I know Codable well enough"	Codable has silent data loss traps (try? swallows errors). codable skill prevents production bugs.

Critical Pattern: Migrations

ALWAYS invoke /skill axiom-database-migration when adding/modifying database columns.

This prevents:

• "FOREIGN KEY constraint failed" errors
• "no such column" crashes
• Data loss from unsafe migrations

Example Invocations

User: "I need to add a column to my SwiftData model"
→ Invoke: /skill axiom-database-migration (critical - prevents data loss)

User: "How do I query SwiftData with complex filters?"
→ Invoke: /skill axiom-swiftdata

User: "CloudKit sync isn't working"
→ Invoke: /skill axiom-cloud-sync-diag

User: "Should I use SwiftData or SQLiteData?"
→ Invoke: /skill axiom-sqlitedata-migration