Swift Concurrency
HoangNguyen0403/agent-skills-standard
Implement async/await, Actors, and structured concurrency in Swift.
Expert Core Data guidance (iOS/macOS): stack setup, fetch requests & NSFetchedResultsController, saving/merge conflicts, threading & Swift Concurrency, batch operations & persistent history…
Install Core Data Expert
$ npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install AvdLee/Core-Data-Agent-Skill core-data-expert --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/AvdLee/Core-Data-Agent-Skill.git skills-src && mkdir -p .claude/skills && cp -r skills-src/core-data-expert .claude/skills/core-data-expert && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "core-data-expert" agent skill from https://github.com/AvdLee/Core-Data-Agent-Skill/tree/main/core-data-expert into .claude/skills/core-data-expert/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "core-data-expert", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/AvdLee/Core-Data-Agent-Skill/tree/main/core-data-expertType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install AvdLee/Core-Data-Agent-Skill core-data-expert --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/AvdLee/Core-Data-Agent-Skill.git skills-src && mkdir -p .agents/skills && cp -r skills-src/core-data-expert .agents/skills/core-data-expert && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "core-data-expert" agent skill from https://github.com/AvdLee/Core-Data-Agent-Skill/tree/main/core-data-expert into .agents/skills/core-data-expert/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "core-data-expert", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install AvdLee/Core-Data-Agent-Skill core-data-expert --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/AvdLee/Core-Data-Agent-Skill.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/core-data-expert .cursor/skills/core-data-expert && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "core-data-expert" agent skill from https://github.com/AvdLee/Core-Data-Agent-Skill/tree/main/core-data-expert into .cursor/skills/core-data-expert/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "core-data-expert", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/AvdLee/Core-Data-Agent-Skill.git --path core-data-expert--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install AvdLee/Core-Data-Agent-Skill core-data-expert --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/AvdLee/Core-Data-Agent-Skill.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/core-data-expert .gemini/skills/core-data-expert && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "core-data-expert" agent skill from https://github.com/AvdLee/Core-Data-Agent-Skill/tree/main/core-data-expert into .gemini/skills/core-data-expert/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "core-data-expert", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install AvdLee/Core-Data-Agent-Skill core-data-expertInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/AvdLee/Core-Data-Agent-Skill.git skills-src && mkdir -p .github/skills && cp -r skills-src/core-data-expert .github/skills/core-data-expert && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "core-data-expert" agent skill from https://github.com/AvdLee/Core-Data-Agent-Skill/tree/main/core-data-expert into .github/skills/core-data-expert/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "core-data-expert", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install AvdLee/Core-Data-Agent-Skill core-data-expert --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/AvdLee/Core-Data-Agent-Skill.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/core-data-expert .opencode/skills/core-data-expert && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "core-data-expert" agent skill from https://github.com/AvdLee/Core-Data-Agent-Skill/tree/main/core-data-expert into .opencode/skills/core-data-expert/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "core-data-expert", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
core-data-expert- GitHub stars
- 314
- Token cost
- ~1.2k tokens
- SKILL.md length
- 398 words
- Files
- 16 (incl. references)
- Skills in repo
- 1
- Repo updated
- First seen
- Licence
- MIT
At a glance
Expert Core Data guidance (iOS/macOS): stack setup, fetch requests & NSFetchedResultsController, saving/merge conflicts, threading & Swift Concurrency, batch operations & persistent history…
- Works in 7 steps: Determine OS/deployment target when… → Identify the context type before… → Recommend NSManagedObjectID for… → …
- Tasks that involve Git workflow
- SKILL.md covers Agent behavior contract…, First 60 seconds (triage…, Routing map (pick the right… and Common errors → next best move, plus 2 more sections
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Core Data Expert is an agent skill from AvdLee/Core-Data-Agent-Skill. Expert Core Data guidance (iOS/macOS): stack setup, fetch requests & NSFetchedResultsController, saving/merge conflicts, threading & Swift Concurrency, batch operations & persistent history, migrations, performance, and NSPersistentCloudKitContainer/CloudKit sync.
Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. The skill folder holds 16 other files, including reference files (for example `references/_index.md`, `references/batch-operations.md` and `references/cloudkit-integration.md`).
It sits in Development, covering Git workflow and iOS development. It works with Swift, iOS and macOS. The repository describes itself as: An Agent Skill focused on Apple’s Core Data framework, helping with data modeling, fetch requests, performance, and common persistence patterns. The licence is MIT.
When your agent uses it
- Tasks that involve Git workflow
- Tasks that involve iOS development
Example prompts
- “/core-data-expert”
Workflow steps
7 steps, taken from the first numbered list in SKILL.md.
- Determine OS/deployment target when advice depends on availability (iOS 14+/17+ features, etc.).
- Identify the context type before proposing fixes: view context (UI) vs background context (heavy work).
- Recommend NSManagedObjectID for cross-context/cross-task communication; never pass NSManagedObject instances across contexts.
- Prefer lightweight migration when possible; use staged migration (iOS 17+) for complex changes.
- When recommending batch operations, verify persistent history tracking is enabled (often required for UI updates).
- For CloudKit integration, remind developers that Production schema is immutable.
- Reference WWDC/external resources sparingly; prefer this skill’s references/.
What it can do on your machine
Read from SKILL.md and the folder at commit 855ca7d. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Core Data Expert loads about 1.2k tokens when it runs, and up to ~43k if it reads all its reference files. Until then it costs about 70 tokens; SKILL.md has 398 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from AvdLee/Core-Data-Agent-Skill at commit 855ca7d, republished under its MIT licence (© AvdLee). 398 words, ~1,207 tokens.
Download SKILL.mdSave it as
.claude/skills/core-data-expert/SKILL.md (or your agent's skills folder). This skill also uses 15 other files; get the full folder from GitHub.- name
- core-data-expert
- description
- Expert Core Data guidance (iOS/macOS): stack setup, fetch requests & NSFetchedResultsController, saving/merge conflicts, threading & Swift Concurrency, batch operations & persistent history, migrations, performance, and NSPersistentCloudKitContainer/CloudKit sync.
Core Data Expert
Fast, production-oriented guidance for building correct, performant Core Data stacks and fixing common crashes.
Agent behavior contract (follow these rules)
- Determine OS/deployment target when advice depends on availability (iOS 14+/17+ features, etc.).
- Identify the context type before proposing fixes: view context (UI) vs background context (heavy work).
- Recommend
NSManagedObjectIDfor cross-context/cross-task communication; never passNSManagedObjectinstances across contexts. - Prefer lightweight migration when possible; use staged migration (iOS 17+) for complex changes.
- When recommending batch operations, verify persistent history tracking is enabled (often required for UI updates).
- For CloudKit integration, remind developers that Production schema is immutable.
- Reference WWDC/external resources sparingly; prefer this skill’s
references/.
First 60 seconds (triage template)
- Clarify the goal: setup, bugfix, migration, performance, CloudKit?
- Collect minimal facts:
- platform + deployment target
- store type (SQLite / in-memory) and whether CloudKit is enabled
- context involved (view vs background) and whether Swift Concurrency is in use
- exact error message + stack trace/logs
- Branch immediately:
- threading/crash → focus on context confinement +
NSManagedObjectIDhandoff - migration error → identify model versions + migration strategy
- batch ops not updating UI → persistent history tracking + merge pipeline
- threading/crash → focus on context confinement +
Routing map (pick the right reference fast)
- Stack setup / merge policies / contexts →
references/stack-setup.md - Saving patterns →
references/saving.md - Fetch requests / list updates / aggregates →
references/fetch-requests.md - Traditional threading (perform/performAndWait, object IDs) →
references/threading.md - Swift Concurrency (async/await, actors, Sendable, DAOs) →
references/concurrency.md - Batch insert/delete/update →
references/batch-operations.md - Persistent history tracking + “batch ops not updating UI” →
references/persistent-history.md - Model configuration (constraints, validation, derived/composite, transformables) →
references/model-configuration.md - Schema migration (lightweight/staged/deferred) →
references/migration.md - CloudKit integration & debugging →
references/cloudkit-integration.md - Performance profiling & memory →
references/performance.md - Testing patterns →
references/testing.md - Terminology →
references/glossary.md
Show full SKILL.md (142 more words)Show less
Common errors → next best move
- “Failed to find a unique match for an NSEntityDescription” →
references/testing.md(sharedNSManagedObjectModel) NSPersistentStoreIncompatibleVersionHashError→references/migration.md(versioning + migration)- Cross-context/threading exceptions (e.g. delete/update from wrong context) →
references/threading.mdand/orreferences/concurrency.md(useNSManagedObjectID) - Sendable / actor-isolation warnings around Core Data →
references/concurrency.md(don’t “paper over” with@unchecked Sendable) NSMergeConflict/ constraint violations →references/model-configuration.md+references/stack-setup.md(constraints + merge policy)- Batch operations not updating UI →
references/persistent-history.md+references/batch-operations.md - CloudKit schema/sync issues →
references/cloudkit-integration.md - Memory grows during fetch →
references/performance.md+references/fetch-requests.md
Verification checklist (when changing Core Data code)
- Confirm the context matches the work (UI vs background).
- Ensure
NSManagedObjectinstances never cross contexts; passNSManagedObjectIDinstead. - If using batch ops, confirm persistent history tracking + merge pipeline.
- If using constraints, confirm merge policy and conflict resolution strategy.
- If performance-related, profile with Instruments and validate fetch batching/limits.
Reference files
references/_index.md(navigation)references/stack-setup.mdreferences/saving.mdreferences/fetch-requests.mdreferences/threading.mdreferences/concurrency.mdreferences/batch-operations.mdreferences/persistent-history.mdreferences/model-configuration.mdreferences/migration.mdreferences/cloudkit-integration.mdreferences/performance.mdreferences/testing.mdreferences/glossary.md
© AvdLee, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 15 other files (references) in core-data-expert of AvdLee/Core-Data-Agent-Skill.
- SKILL.md
- references/_index.md
- references/batch-operations.md
- references/cloudkit-integration.md
- references/concurrency.md
- references/fetch-requests.md
- references/glossary.md
- references/migration.md
- references/model-configuration.md
- references/performance.md
- references/persistent-history.md
- references/project-audit.md
- references/saving.md
- references/stack-setup.md
- references/testing.md
- references/threading.md
Open the folder on GitHubat commit 855ca7d
Compare with similar skills
Core Data Expert next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Core Data Expert this skillAvdLee/Core-Data-Agent-Skill | 314 | — | ~1.2k | Automated safety check: Pass | MIT | |
| Swift ConcurrencyHoangNguyen0403/agent-skills-standard | 571 | — | ~545 | Automated safety check: Pass | MIT | |
| AgentSquad for Swift2FastLabs/agent-squad | 7.8k | — | ~3.5k | Automated safety check: Pass | Apache-2.0 | |
| Stellar iOS Mac SDKSoneso/stellar-ios-mac-sdk | 132 | — | ~4.3k | Automated safety check: Pass | Apache-2.0 | |
| Snapshot Testsmicrosoft/SwiftStreamingMarkdown | 378 | — | ~2.2k | Automated safety check: Pass | MIT | |
| Bootstrap iOSRayFernando1337/rayfernando-skills | 130 | — | ~1.1k | Automated safety check: Pass | Apache-2.0 |
Similar skills
AgentSquad for Swift
2FastLabs/agent-squad
Guides building on-device multi-agent apps in Swift with the AgentSquad framework: which agent, orchestrator, classifier, storage or voice type fits each situation.
Stellar iOS Mac SDK
Soneso/stellar-ios-mac-sdk
Guides Stellar blockchain development in Swift using stellar-ios-mac-sdk.
- Official
Snapshot Tests
microsoft/SwiftStreamingMarkdown
Record and validate swift-snapshot-testing snapshots in the SwiftStreamingMarkdown package: regenerate reference PNGs, run snapshot tests, and diff failed snapshots.
Bootstrap iOS
RayFernando1337/rayfernando-skills
Bootstrap agents for iOS, iPadOS, macOS, Swift, SwiftUI, SwiftData/Core Data, Swift Testing, Xcode build/test/debug, Simulator, App Intents, or XcodeBuildMCP work.
Swift Development
aiskillstore/marketplace
Comprehensive Swift development for building, testing, and deploying iOS/macOS applications.
Related
Categories
Questions about Core Data Expert
What does Core Data Expert do?
Expert Core Data guidance (iOS/macOS): stack setup, fetch requests & NSFetchedResultsController, saving/merge conflicts, threading & Swift Concurrency, batch operations & persistent history…. Core Data Expert is an agent skill from AvdLee/Core-Data-Agent-Skill. Expert Core Data guidance (iOS/macOS): stack setup, fetch requests & NSFetchedResultsController, saving/merge conflicts, threading & Swift Concurrency, batch operations & persistent history, migrations, performance, and NSPersistentCloudKitContainer/CloudKit sync.
When should I use Core Data Expert?
Core Data Expert fits situations like: tasks that involve Git workflow; tasks that involve iOS development.
How do I install Core Data Expert in Claude Code?
Run `npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a claude-code`. Or copy the skill folder (core-data-expert in AvdLee/Core-Data-Agent-Skill) into .claude/skills/core-data-expert in your project. Claude Code loads it when a task matches its description.
How do I install Core Data Expert in Codex?
Run `npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a codex`. Or copy the skill folder (core-data-expert in AvdLee/Core-Data-Agent-Skill) into .agents/skills/core-data-expert in your project. Codex loads it when a task matches its description.
Can I use Core Data Expert in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add AvdLee/Core-Data-Agent-Skill --skill core-data-expert -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/core-data-expert, .gemini/skills/core-data-expert, .github/skills/core-data-expert and .opencode/skills/core-data-expert in your project.
What does Core Data Expert need to run?
SKILL.md names no scripts, command-line tools or credentials: Core Data Expert is instructions for the agent only.
Does Core Data Expert access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Core Data Expert safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Core Data Expert use?
Core Data Expert is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Core Data Expert use?
About 1.2k tokens (SKILL.md is roughly 4.8k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 42k tokens, read only when the agent opens those files.
What are the alternatives to Core Data Expert?
Skills that share tags, products or a category with Core Data Expert: Swift Concurrency (HoangNguyen0403/agent-skills-standard, 571 stars), AgentSquad for Swift (2FastLabs/agent-squad, 7.8k stars), Stellar iOS Mac SDK (Soneso/stellar-ios-mac-sdk, 132 stars) and Snapshot Tests (microsoft/SwiftStreamingMarkdown, 378 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Core Data Expert?
AvdLee (a GitHub user) maintains it in AvdLee/Core-Data-Agent-Skill, which has 314 GitHub stars. The repository was last updated on September 14, 2026.
Source: AvdLee/Core-Data-Agent-Skill on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.