axiom-data

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

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Repository: CharlesWiltgen/Axiom
Last source activity: August 15, 2026 at 19:31
Detected SKILL.md language: English
Stars: 1,125
Forks: 82

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View all from this repository

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

Data & Persistence

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

Auditors are skills here. Where this router says "Launch some-auditor agent", invoke the matching Codex skill instead — same procedure, no Claude Code agent required.

Available: axiom-audit-codable, axiom-audit-core-data, axiom-audit-database-schema, axiom-audit-grdb-performance, axiom-audit-icloud, axiom-audit-storage, axiom-audit-swiftdata.

The ones that shell out — builds, tests, simulators, crash symbolication — need shell access to run.

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

SwiftData @Model, @Query, ModelContext, sectioned queries / ResultsObserver / @Attribute(.codable) / dynamic compound predicates (`OS27`)	See `skills/swiftdata.md`
SwiftData schema migration, VersionedSchema	See `skills/swiftdata-migration.md`
SwiftData migration crashes, data loss	See `skills/swiftdata-migration-diag.md`
Migrating from Realm to SwiftData	See `skills/realm-migration-ref.md`
SwiftData vs SQLiteData decision	See `skills/sqlitedata-migration.md`
GRDB queries, upsert, ValueObservation, DatabaseMigrator, encryption	See `skills/grdb.md`
GRDB performance, indexes, EXPLAIN QUERY PLAN, cursors, observation not firing	See `skills/grdb-performance.md`
Full-text search (FTS5) in GRDB or SQLiteData	See `skills/sqlite-fts-ref.md`
Storing or querying JSON inside a SQLite column (JSON1, JSONB)	See `skills/sql-json-ref.md`
GRDB shared across app + widget/extension (App Group)	See `skills/grdb-app-groups.md`
SQLiteData @Table, CRUD, SyncEngine	See `skills/sqlitedata.md`
SQLiteData advanced patterns, CTEs, views	See `skills/sqlitedata-ref.md`
Core Data stack, relationships, concurrency	See `skills/core-data.md`
Core Data migration crashes, thread errors	See `skills/core-data-diag.md`
ANY schema migration safety	See `skills/database-migration.md`
Codable, JSON encoding/decoding	See `skills/codable.md`
Cloud sync architecture, offline-first	See `skills/cloud-sync.md`
CloudKit, CKSyncEngine, CKRecord	See `skills/cloudkit-ref.md`
iCloud Drive, ubiquitous containers	See `skills/icloud-drive-ref.md`
Cloud sync errors, conflict resolution	See `skills/cloud-sync-diag.md`
Storage strategy, where to store data	See `skills/storage.md`
Storage issues, files disappeared	See `skills/storage-diag.md`
Storage management, disk pressure	See `skills/storage-management-ref.md`
Keychain / secure credential storage	See axiom-security (skills/keychain.md)
Keychain errors (errSecDuplicateItem)	See axiom-security (skills/keychain-diag.md)
Keychain API reference	See axiom-security (skills/keychain-ref.md)
Encryption / signing / key management	See axiom-security (skills/cryptokit.md)
CryptoKit API reference	See axiom-security (skills/cryptokit-ref.md)
File protection, NSFileProtection	See axiom-security (skills/file-protection-ref.md)
tvOS data persistence (no local storage)	See axiom-swift (skills/tvos.md)
tvOS + CloudKit SyncEngine	See `skills/sqlitedata.md`

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. See axiom-swift (skills/tvos.md) for the iCloud-first pattern.
"UserDefaults is fine for this token"	UserDefaults is unencrypted, backed up to iCloud, and visible to MDM profiles. One audit catches it. keychain stores tokens securely.
"I'll encrypt it myself with CommonCrypto"	CryptoKit replaced CommonCrypto's buffer-management nightmares with one-line APIs. cryptokit prevents misuse.

axiom-data

Install options

Review the source files

Data & Persistence

When to Use

Quick Reference

Data & Persistence

When to Use

Quick Reference

Automated Scanning

Decision Tree

Sync patterns

Anti-Rationalization

Critical Pattern: Migrations

Example Invocations

axiom-data

Source facts

Install options

Review the source files

More from this repository

More from this repository

Data & Persistence

When to Use

Quick Reference

Data & Persistence

When to Use

Quick Reference

Automated Scanning

Decision Tree

Sync patterns

Anti-Rationalization

Critical Pattern: Migrations

Example Invocations