Axiom Data

Data & Persistence

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

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Not on Claude Code? Where this router says "Launch some-auditor agent", read that auditor's file in this suite and follow it inline — the same procedure, needing only file search and read. Available here: skills/codable-auditor.md, skills/core-data-auditor.md, skills/database-schema-auditor.md, skills/grdb-performance-auditor.md, skills/icloud-auditor.md, skills/storage-auditor.md, skills/swiftdata-auditor.md. Agents that need Bash — builds, tests, simulators, crash symbolication — stay Claude Code-only; there is no inline equivalent for those.

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When to Use

Use this skill 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
• Keychain / secure credential storage
• Encryption, signing, key management (CryptoKit)

Quick Reference

Automated Scanning

Core Data audit → Launch core-data-auditor agent or /axiom:audit core-data (safety violations, architectural gaps — migration options, thread-confinement, N+1 queries, merge policies, context isolation) Codable audit → Launch codable-auditor agent or /axiom:audit codable (safety violations, semantic gaps — try? swallowing errors, JSONSerialization, date handling, silent field drops, wrapper-hidden fallbacks, cross-file strategy drift, enum future-case crashes) iCloud audit → Launch icloud-auditor agent or /axiom:audit icloud (entitlement checks, file coordination, incomplete CKError matrix coverage, missing account-change observation, polling vs CKSubscriptions, SwiftData + CloudKit unsupported features, compound risks like uncoordinated I/O across extensions) Storage audit → Launch storage-auditor agent or /axiom:audit storage (wrong file locations, missing backup exclusions, sensitive data on disk vs Keychain, missing App Group containers, unbounded cache growth, orphan files, compound risks like user data in tmp/ + critical content) Database schema audit → Launch database-schema-auditor agent or /axiom:audit database-schema (unsafe ALTER TABLE, DROP operations, missing idempotency, FK constraints declared but not enforced, incomplete upgrade paths, compound risks like INSERT OR REPLACE on FK-referenced tables) GRDB performance audit → Launch grdb-performance-auditor agent or /axiom:audit grdb-performance (raw SQL string interpolation, missing FK indexes in raw SQL, missing PRAGMA optimize for raw-GRDB apps, journal mode mismatch for app-group DBs, missing observesSuspensionNotifications for shared DBs, prefix-redundant indexes in raw SQL, legacy Record subclass, INSERT OR REPLACE misused as upsert, observation on WITHOUT ROWID tables, WITHOUT ROWID upsert bugs) SwiftData audit → Launch swiftdata-auditor agent or /axiom:audit swiftdata (struct models, missing schema registration, array relationships without defaults, background context misuse, N+1 patterns, stale predicates, CloudKit conformance gaps, compound risks like struct model + array relationship)

Decision Tree

1. SwiftData? → skills/swiftdata.md, skills/swiftdata-migration.md
2. Core Data? → skills/core-data.md, skills/core-data-diag.md
3. GRDB? → skills/grdb.md

3a. GRDB perf, slow query, schema design for perf? → skills/grdb-performance.md 3b. FTS5 (full-text search, any layer)? → skills/sqlite-fts-ref.md 3c. DB shared across app + extension/widget/Live Activity? → skills/grdb-app-groups.md

1. SQLiteData? → skills/sqlitedata.md, skills/sqlitedata-ref.md

4a. @Shared/@SharedReader, or the loading/error state behind @FetchAll? → skills/swift-sharing.md

1. ANY schema migration? → skills/database-migration.md (ALWAYS — prevents data loss)
2. Realm migration? → skills/realm-migration-ref.md
3. SwiftData vs SQLiteData? → skills/sqlitedata-migration.md
4. Cloud sync architecture? → skills/cloud-sync.md
5. CloudKit? → skills/cloudkit-ref.md
6. iCloud Drive? → skills/icloud-drive-ref.md
7. Cloud sync errors? → skills/cloud-sync-diag.md
8. Codable/JSON serialization? → skills/codable.md
9. File storage strategy? → skills/storage.md, skills/storage-diag.md, skills/storage-management-ref.md
10. File protection? → See axiom-security (skills/file-protection-ref.md)
11. Keychain / storing tokens, passwords, secrets securely? → See axiom-security (skills/keychain.md), See axiom-security (skills/keychain-diag.md), See axiom-security (skills/keychain-ref.md)
12. SecItem errors (errSecDuplicateItem, errSecItemNotFound, errSecInteractionNotAllowed)? → See axiom-security (skills/keychain-diag.md)
13. Encryption, signing, Secure Enclave, CryptoKit? → See axiom-security (skills/cryptokit.md), See axiom-security (skills/cryptokit-ref.md)
14. Quantum-secure cryptography, HPKE, ML-KEM? → See axiom-security (skills/cryptokit.md)