Agent-Skills.md

Agent Skills: iOS Data & Persistence Router

Use when working with ANY data persistence, database, axiom-storage, CloudKit, migration, or serialization. Covers SwiftData, Core Data, GRDB, SQLite, CloudKit sync, file storage, Codable, migrations.

UncategorizedID: charleswiltgen/axiom/axiom-ios-data

Repository

charleswiltgen/axiom
CharlesWiltgenLicense: MIT
42644

Install this agent skill to your local

pnpm dlx add-skill https://github.com/CharlesWiltgen/Axiom/tree/HEAD/.claude-plugin/plugins/axiom/skills/axiom-ios-data

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.claude-plugin/plugins/axiom/skills/axiom-ios-data/SKILL.md

Skill Metadata

Name
axiom-ios-data
Description
Use when working with ANY data persistence, database, axiom-storage, CloudKit, migration, or serialization. Covers SwiftData, Core Data, GRDB, SQLite, CloudKit sync, file storage, Codable, migrations.

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

tvOS Storage

tvOS data persistence → /skill axiom-tvos (CRITICAL: no persistent local storage on tvOS) tvOS + CloudKit → /skill axiom-sqlitedata (recommended: SyncEngine as persistent store)

Automated Scanning

Core Data audit → Launch core-data-auditor agent or /axiom:audit core-data (migration risks, thread-confinement, N+1 queries, production data loss) Codable audit → Launch codable-auditor agent or /axiom:audit codable (try? swallowing errors, JSONSerialization, date handling) iCloud audit → Launch icloud-auditor agent or /axiom:audit icloud (entitlement checks, file coordination, CloudKit anti-patterns) Storage audit → Launch storage-auditor agent or /axiom:audit storage (wrong file locations, missing backup exclusions, data loss risks)

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
  15. Want Core Data safety scan? → core-data-auditor (Agent)
  16. Want Codable anti-pattern scan? → codable-auditor (Agent)
  17. Want iCloud sync audit? → icloud-auditor (Agent)
  18. Want storage location audit? → storage-auditor (Agent)
  19. tvOS data persistence? → axiom-tvos (CRITICAL: no persistent local storage) + axiom-sqlitedata (CloudKit SyncEngine)

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. | | "I'll use local storage on tvOS" | tvOS has NO persistent local storage. System deletes Caches at any time. axiom-tvos explains the iCloud-first pattern. |

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

User: "Check my Core Data code for safety issues" → Invoke: core-data-auditor agent

User: "Scan for Codable anti-patterns before release" → Invoke: codable-auditor agent

User: "Audit my iCloud sync implementation" → Invoke: icloud-auditor agent

User: "Check if my files are stored in the right locations" → Invoke: storage-auditor agent

User: "How do I persist data on tvOS?" → Invoke: /skill axiom-tvos + /skill axiom-sqlitedata

User: "My tvOS app loses data between launches" → Invoke: /skill axiom-tvos