Native iOS Development

Use this skill for native iOS work only. It is the default shared-skill entrypoint for SwiftUI-first iOS 17+ apps, bounded rewrites from older codebases, and agent-assisted workflows in Xcode, Codex, and Claude Code.

Quick Reference

Task	Default Picks	Notes
State & UI
New UI screens	SwiftUI	UIKit interop only where Apple APIs require it
Observable state (iOS 17+)	@Observable + main actor isolation	Replaces ObservableObject/Published
Async work	async/await, structured concurrency	Detached tasks only when intentionally breaking inheritance
Unit/integration tests	Swift Testing	Preferred over XCTest for new tests
UI automation tests	XCTest / XCUITest	Keep using for UI and performance tests
State machine discipline
Submit guard	guard state == .idle else { return }	Prevents double-tap duplicate submissions in @Observable stores
Transient completion	One-shot UI effect or explicit acknowledgement	Do not reset durable state on an arbitrary timer; store and cancel any delayed task
Minimal state enums	Remove states that can't happen anymore	Dead enum cases produce dead error handling and mislead future readers
Networking & resilience
Network reachability	@Observable singleton + NWPathMonitor	Publish isConnected; disable submit buttons when offline; start monitor in screen .onAppear
Agent tooling & build
Agent tooling (in Xcode)	Xcode native assistant	Verify the live stable/beta Xcode and Swift versions, and Xcode's macOS host requirement (matters for CI runner images), at developer.apple.com/news/releases before citing one; check Apple's Upcoming Requirements page for the upload-SDK floor and minimum deployment target before submission — do not build release submissions against a beta SDK
Agent tooling (outside Xcode)	XcodeBuildMCP if callable	Otherwise fall back immediately to Apple CLI
CLI fallback	xcodebuild, simctl, xcresulttool	Default path when MCP is unavailable or blocked
Build / install / stale-app failures	software-ios-runtime-debugging	Use before UI or feature diagnosis
XcodeGen projects	scripts/generate-xcodeproj.sh	Must regenerate after adding new Swift files
Local-dev launcher pair	scripts/run-local-ios-dev.sh + scripts/stop-local-ios-dev.sh	Two defensive guards (grep env + generated plist for localhost:); persist simulator UDID; never pkill -f Simulator. See quick-reference-extended.md#agent-tooling--build
.pbxproj-managed projects	Add new files to target membership	Do not assume on-disk Swift files are auto-discovered
Generated files / CI landmines	Commit generated outputs or regenerate in CI hook	git add -f for gitignored-folder tracked files; Xcode Cloud ci_post_clone.sh for env shims. See quick-reference-extended.md
TARGETED_DEVICE_FAMILY → "1"	Requires fresh archive + ASC build attachment	Changing project.yml alone is insufficient; value is baked into binary.
Canvas, immersive screens, sheets, l10n hygiene	See quick-reference-extended.md	Canvas start state and gestures, persistent sheets, viz state ownership, grid sizing, sheet swapping, l10n plain-enum call rule (catalog parity and regeneration live in software-localisation)
StoreKit & billing
StoreKit 2 subscriptions	@Observable StoreKitManager + TransactionSyncService	transaction.finish() only after backend sync confirms
Paywall presentation	.sheet(isPresented:) from any locked screen	Don't navigate to Settings; present modal directly
Product pricing display	product.displayPrice from StoreKit	Never hardcode prices; Apple handles locale formatting
Promotional offers (rewards)	Server-signed .promotionalOffer() in Product.purchase(options:)	Bridges Stripe credit gaps for Apple-billed users; user must redeem
Paid Apps Agreement (#1 invisible blocker)	Verify Active at appstoreconnect.apple.com/business	Silent empty Product.products(for:) results; check before subscription-level diagnosis. Full decision table + timeline in app-store-connect-checklist.md Phase 5. See quick-reference-extended.md
ASC Missing Metadata	Fill all required fields: prices, localization, review screenshot	Products exist but fields incomplete. Workflow in app-store-connect-checklist.md. See quick-reference-extended.md
Review screenshot	sRGB 8-bit RGB PNG 72 DPI, 1284 × 2778	ASC rejects Display P3 / 16-bit device screenshots; use Pillow profile conversion. See quick-reference-extended.md
Accounting currency (backend-denominated)	NumberFormatter + explicit currencyCode + locale = .current	Never String(format: "£%.2f", …); details in quick-reference-extended.md
Year/ID display	Text(verbatim:)	Suppress locale number formatting (2026 not 2,026)
Locale-aware time formatting; strings and backend locale	"jm" date skeleton via DateFormatter; strings, plurals and the backend translation pipeline live in software-localisation	Platform rows in quick-reference-extended.md
Auth & push
Sign in with Apple	ASAuthorizationController + CheckedContinuation	Guideline 4.8 requires an equivalent privacy-preserving login (limits data to name/email, allows a private relay email, no ad tracking without consent) if a 3rd-party social login is offered — Sign in with Apple is the usual way to satisfy it, not the only one; check current exemptions
OTP code input	Hidden TextField + .textContentType(.oneTimeCode)	Better than magic links for native; iOS auto-fills from notifications
Non-@MainActor delegates	Match the SDK requirement; hop to @MainActor for UI state	MainActor.assumeIsolated checks isolation; use it only when the callback contract guarantees that executor.
Push notification categories	Register UNNotificationCategory in didFinishLaunchingWithOptions	Must be set before any notification arrives; match aps.category from backend
Badge count (iOS 16+)	try? await UNUserNotificationCenter.current().setBadgeCount(0)	applicationIconBadgeNumber is deprecated; setBadgeCount is async throws
Push delegate isolation	Inspect the imported SDK requirement and callback contract	Hop UI mutations to @MainActor; do not infer a universal delegate fix from a private crash symbol. See swiftui-observation-concurrency.md and quick-reference-extended.md
Task { } isolation	Inherits the actor context where its closure is formed; annotate explicitly across nonisolated callbacks	Task.detached breaks actor inheritance. See swiftui-observation-concurrency.md
actor vs @MainActor final class	Choose the isolation owner by the work and shared state	A main-actor caller resumes on the main actor after await; keep CPU-heavy work off it. See swiftui-observation-concurrency.md
@Sendable async closure awaited from @MainActor	Return results to the isolated caller; isolate the body if it needs UI state	@Sendable is a transfer-safety constraint, not an executor choice; caller isolation survives await. See swiftui-observation-concurrency.md
SCNView in UIViewRepresentable	Create initial scene once; update changed inputs	A no-op updateUIView is correct only for immutable inputs. See swiftui-observation-concurrency.md
Push action routing	Check response.actionIdentifier in didReceive	UNNotificationDefaultActionIdentifier = tap; custom IDs = action buttons; dismiss = no route
Push-open ownership, preferences, entitlements, APNs proof, export gate, backend routing, QA loop	See full rows in quick-reference-extended.md	Inspect final exported app/profile: push-enabled TestFlight/App Store exports require production; backend: per-device push_environment column authoritative
Swift Concurrency crash triage	Symptom-first triage runbook	Private SwiftUI symbol crash → start at swift-concurrency-crash-triage.md; ladder: console → MTC → TSan → lldb bt
SwiftUI API modernization
Deprecated API review	references/swiftui-deprecated-api.md	Systematic deprecated→modern mapping
SwiftUI performance audit	references/swiftui-performance.md	View splitting, lazy stacks, modifier efficiency
Modern Swift idioms	references/modern-swift-patterns.md	Foundation modernization, date/string/collection patterns
Concurrency (constructive)
Writing correct concurrency	references/swift-concurrency-patterns.md	Structured concurrency, async streams, bridging, migration
Concurrency compiler errors	references/swift-concurrency-diagnostics.md	Error→fix mapping for Swift 6 diagnostics
Persistence
SwiftData modeling	references/swiftdata-core.md	Core rules, predicates, CloudKit, indexing, class inheritance
Core Data persistence	references/core-data-persistence.md	Stack setup, contexts, object IDs, batch ops, migrations, CloudKit
Reusable app skeleton	references/native-ios-app-foundation-skeleton.md	SwiftUI shell, Observation state, persistence, CloudKit, App Intents, local AI hooks, release gates
iCloud database app	references/icloud-cloudkit-app-skeleton.md	SwiftData/Core Data/CloudKit choice, private/public/shared scopes, no-server limits
Stacks & monetization
Pick a starter stack to monetize/engage	references/starter-stacks-and-monetization.md	CloudKit→Cloudflare→RevenueCat→Supabase graduation ladder; on-device AI as free tier; webhook idempotency traps
Run iOS dev as a conveyor / app factory	references/ios-app-conveyor.md	4 pillars: default stack per class, shared SPM, Fastlane+Match CI, agent build loop; 2026 stack survey
Build performance
Xcode build optimization	references/xcode-build-optimization.md	Benchmarking, diagnostic flags, SPM analysis, common wins
Swift 6.2+ / Xcode 26+ additions	See quick-reference-extended.md	Default MainActor isolation, iOS 26 withAnimation regression, stale SubscriptionStatus.all, AnyView/@ObservedObject/NavigationView/.id(UUID()) modernization, Combine lifecycle, coordinator navigation

Rule: rules/ios/money.md loads this invariant when Claude edits a matching file.

When to Use This Skill

SwiftUI-first iOS 17+ screens, app skeletons, UIKit bounded rewrites, agent-assisted Xcode/Codex/Claude Code workflows, Swift Concurrency, SwiftData/Core Data persistence, Xcode build optimization, privacy manifests, release gates, and native iOS code review.

Defaults

• UI: SwiftUI-first; UIKit interop only where Apple APIs require it.
• State: @Observable + main actor isolation (iOS 17+).
• New projects: SWIFT_DEFAULT_ACTOR_ISOLATION = MainActor (Xcode 26+); nonisolated/@concurrent only when breaking out.
• Async: structured concurrency + async/await; detached tasks only when intentionally breaking inheritance.
• Tests: Swift Testing for unit/integration; XCTest/XCUITest for UI automation.
• Release gates: privacy manifests, required-reason APIs, SDK compliance, accessibility, real-device verification — non-optional. Verify minimum Xcode version at developer.apple.com/news/releases each release cycle.

Version Currency (check every session)

• Current stable vs beta: read Apple's Developer Releases page (developer.apple.com/news/releases) for the current GA iOS/Xcode and the beta point releases, and swift.org/blog for the current Swift release, before naming any version. APIs from a GA release are shippable behind #available checks; an Xcode beta is never used for App Store submissions. Check the Xcode release notes for the minimum macOS host version.
• Submission gates: App Store Connect enforces two separate floors — the build SDK (which Xcode you compile with) and the minimum deployment target. Read Apple's Upcoming Requirements page before each submission; a build-SDK floor does not change your deployment target.
• Point releases drift fast; treat any specific point-release number in this skill as an example, not a current fact.

Expert Judgment Calls

• SwiftUI vs UIKit: default to SwiftUI. Reach for UIKit interop only for a named capability gap (e.g., precise text-kit control, certain camera/AR compositions, legacy UICollectionView compositional layouts not yet matched in SwiftUI) — not because a contributor is more comfortable in UIKit. Re-evaluate the gap list each Xcode cycle; SwiftUI closes gaps yearly and yesterday's justified UIKit escape hatch is often removable.
• Strict concurrency adoption: recent Xcode new-project templates can set SWIFT_DEFAULT_ACTOR_ISOLATION = MainActor and enable Approachable Concurrency without turning on Swift 6 language mode — check SWIFT_VERSION and the isolation settings in the generated project rather than trusting a remembered default. Treat "Swift 6 language mode", "Approachable Concurrency" (changes runtime behavior: existing nonisolated async functions can now run on the caller's actor), and "default MainActor isolation" as three separate switches with separate migration cost, not one bundle. For a new project it is reasonable to turn all three on, since there is no legacy code to fight. For an existing pre-Swift-6 codebase, do not flip strict concurrency in one PR: enable it module-by-module or file-by-file, starting from leaf types with no dependents, and budget real calendar time — the Swift Forums "explosion of isolation violations" reports are the normal experience, not a sign something is wrong. Never bulk-silence with @preconcurrency as a substitute for doing the migration.
• Dependency management: Swift Package Manager is the default for every new dependency and for new projects outright. Only keep CocoaPods where an existing project already depends on it and the migration cost (Pods with no SPM manifest, deeply nested transitive Pod dependencies) currently exceeds the maintenance tax of running two package managers. Don't introduce a new CocoaPods dependency into an SPM-only project to save a day of integration work — it reintroduces the exact tooling fragmentation SPM removed.
• Modularization threshold: don't split into SPM modules pre-emptively. Splitting pays off once a target exceeds roughly 150-200 files, once independent teams need to build/test in isolation, or once agent-driven workflows need a bounded package to avoid loading the whole app graph for one feature. Below that, module boundaries add build-graph and API-surface overhead without a compiler-enforced win. See xcode-build-optimization.md → SPM Dependency Analysis for the build-time tradeoffs either way.
• TestFlight and phased release discipline: never promote straight from internal build to a 100% production release. Run at least one external TestFlight wave sized to catch device/OS-version variance, then use phased release (7-day ramp) for production so a bad build caps its blast radius before full rollout. Treat a skipped phased release as a release-risk finding worth calling out, not a minor process nit.

ASCII Flow

iOS native task
  -> Confirm app shape: SwiftUI, UIKit interop, service, or release gate
  -> Prove Xcode, simulator/device, build, install, and launch reality
  -> Choose architecture: Observation, concurrency, persistence, navigation
  -> For reusable skeletons, add iCloud data, App Intents, local AI/retrieval hooks, and release gates
  -> Implement bounded slice with tests and privacy/accessibility checks
  -> Check Swift, StoreKit, signing, privacy, and App Store traps
  -> Build, run, inspect logs/screenshots, and report proof

Runtime Truth And Prompting

Proof-first: verify tool reality (Xcode assistant → XcodeBuildMCP → Apple CLI), prove build+launch before UI diagnosis, require bounded slices with explicit proof artifacts. Load references/runtime-proof-and-prompts.md for agent defaults, proof rules, execution loop, and prompt shape.

Rewrite Workflow

1. Lock the baseline: existing app behavior, minimum OS, device classes, external integrations, and non-goals.
2. Choose the target defaults: SwiftUI-first, iOS 17+, Observation, Swift Concurrency, Swift Testing, XCTest/XCUITest.
3. Slice the rewrite into bounded vertical features: app shell, auth/session, core navigation, feature flows, integrations, release surfaces. XcodeGen: run scripts/generate-xcodeproj.sh after adding new files. .pbxproj projects: register new files in target membership explicitly.
4. For each slice, require evidence: build success, run success, targeted tests, parity notes, and known gaps.
5. Keep release-only concerns visible throughout: privacy manifests, entitlement changes, required-reason APIs, push, store metadata. Push QA: sign off sandbox (device) and production (TestFlight) paths separately; validate cold-start tap, warm resume, and normal reopen.
6. End every batch with a handoff: changed behavior, validation performed, residual risk, next slice.
7. When a backend change eliminates an error class, immediately remove the now-impossible error types, decoders, and UI states from the iOS client.

Specialized Patterns

Load references/ui-and-integration-patterns.md for Canvas/gesture/immersive surfaces, auth/onboarding/Supabase integration gotchas, and StoreKit 2 billing + server-notification rules.

Release Signing And Distribution

Xcode can re-sign an archive during distribution. Validate the exported App Store/TestFlight app and its provisioning profile; push-enabled exports require aps-environment = production, and release exports must not enable debugging. Use the Organizer distribution method for TestFlight/App Store. Full gate list (archive inspection, generated Info.plist, encryption prompt) in references/ios-release-and-compliance.md.

Known iOS Traps

Full trap table in references/ios-traps-and-scenarios.md. Top traps by crash frequency and silent-failure risk:

Trap	Symptom	Fix
_performBlockAfterCATransactionCommitSynchronizes:	UIKit main-thread assertion	Capture the backtrace and isolate the actual UI call; the private symbol does not identify one cause.
UN delegate touching UI state	Isolation diagnostic or notification-tap failure	Match the SDK requirement, transfer a Sendable payload, then hop UI work to @MainActor.
Task { } created in a nonisolated callback then mutating @Observable	Off-actor UI mutation; the closure inherits the nonisolated creation context	Hop explicitly with Task { @MainActor [weak self] in … }; a task created inside a main-actor-isolated method already inherits that actor
Actor call awaited from @MainActor	Caller resumes on its own actor; shared state may change while suspended	Re-check request identity/state after await; do not replace an actor to repair a supposed executor loss.
@Sendable async closure touching UI state	Closure body may lack required actor isolation	Add @MainActor only when its body needs UI state; the caller still resumes on its actor.
SCNView updates	Rebuilding scenes can reset interaction state or perform unnecessary work	Create initial objects once; apply changed inputs incrementally in updateUIView.
iOS 26 withAnimation in @MainActor methods	Animations fail to start or skip starting state	Hoist withAnimation out of @MainActor body
Xcode 26 SubscriptionStatus.all stale	StoreKit 2 shows wrong tier post-upgrade	Query Product.SubscriptionInfo.Status directly
Locale-change handler missing store reset	Language change has no visible effect	reset() every prose-caching store + URLCache.shared.removeAllCachedResponses()
Stored profile locale wins over ?locale= param	iOS user sees English despite picker showing Russian	Server priority must be ?locale= > Accept-Language > stored profile

Web-search _performBlockAfterCATransactionCommitSynchronizes: before code review (private symbol). dataCorrupted + <!DOCTYPE html> = API routing/auth bug, not push crash. Never bulk-silence Swift 6 errors with @preconcurrency. Detailed recipes in swift-concurrency-crash-triage.md.

When NOT to Use This Skill

Use a different skill when:

• Cross-platform or platform-choice decisions → software-mobile
• iOS build/install/launch failures, stale installs, simulator drift, XcodeGen issues → software-ios-runtime-debugging
• iOS test execution, simulator flake control, xcresult triage → qa-testing-ios
• Web UI or browser app implementation → software-frontend
• General architecture without iOS-specific constraints → software-architecture-design
• iOS visual design, HIG layout/typography, dark mode design, dashboard patterns → software-ios-design

Scenarios

S1 StoreKit 2 entitlement reconciliation · S2 APNs sandbox vs production proof · S3 Swift 6.2 concurrency migration · S4 withAnimation Xcode 26 regression · S5 privacy manifest pre-submission audit. Step-by-step recipes in references/ios-traps-and-scenarios.md.

Navigation

References

Resource	Purpose
references/quick-reference-extended.md	Verbose Quick Reference rows moved from SKILL.md: local-dev launcher, CI landmines, StoreKit/ASC, l10n, push
references/ios-traps-and-scenarios.md	Full Known iOS Traps table and Scenarios S1–S5 recipes
references/ios-rewrite-playbook.md	Rewrite slicing, acceptance criteria, and evidence rules
references/agentic-ios-tooling.md	Xcode's native coding agent, XcodeBuildMCP, and CLI fallback selection rules
references/xcodebuildmcp-workflows.md	Verified XcodeBuildMCP install, config, and workflow loops
references/codex-claude-ios-workflows.md	Repo memory, approval boundaries, and prompt patterns
references/runtime-proof-and-prompts.md	Proof-first runtime execution, token discipline, and prompt shape
references/ui-and-integration-patterns.md	Canvas, immersive UI, backend integration, and StoreKit 2 patterns
references/swiftui-observation-concurrency.md	Verified app-layer defaults for SwiftUI, Observation, and concurrency
references/swiftui-deprecated-api.md	Deprecated→modern SwiftUI API mapping
references/swiftui-performance.md	View splitting, lazy stacks, modifier efficiency, and rendering patterns
references/swift-concurrency-patterns.md	Structured concurrency, async streams, bridging, and migration tables
references/swift-concurrency-diagnostics.md	Swift concurrency compiler error→fix mapping
references/networking-and-data-loading.md, references/swiftui-composition-patterns.md	API client, request coalescing, pagination, image cache, MetricKit; ViewModifier, PreferenceKey, property wrappers, result builders
references/swiftdata-core.md	SwiftData modeling, predicates, CloudKit, indexing, and class inheritance
references/core-data-persistence.md	Core Data stack ownership, context rules, migrations, and CloudKit constraints
references/native-ios-app-foundation-skeleton.md	Reusable SwiftUI app foundation: modules, defaults, extension points, proof gates
references/icloud-cloudkit-app-skeleton.md	iCloud/CloudKit data-layer: schema, database scopes, no-server boundaries
references/modern-swift-patterns.md	Modern Swift idioms, Foundation API, and coding style
references/xcode-build-optimization.md	Build benchmarking, compilation diagnostics, and optimization workflow
references/ios-release-and-compliance.md	Privacy, SDK compliance, and release-gate checks
data/sources.json	Primary sources and current external references

Templates

Template	Purpose
assets/template-ios-rewrite-brief.md	Rewrite scope and constraint brief
assets/template-native-ios-app-skeleton.md	Copyable native iOS app foundation layout and module checklist
assets/template-ios-cloudkit-persistence-stack.md	SwiftData/Core Data/CloudKit stack starter with schema and sync gates
assets/template-ios-makefile-and-proof-loop.md	Agent-friendly Makefile targets and build/test/archive proof loop
assets/template-ios-feature-request.md	Feature-level Codex / Claude Code request format
assets/template-ios-proof-checklist.md	Source-backed proof and validation checklist
assets/template-ios-agent-handoff.md	Post-change handoff with evidence and residual risk
assets/scaffolds/app-class-blueprints.md	Pick app class (CRUD/notes, AI wrapper, content/feed, utility-IAP) → tier, scaffolds, monetization, cost
assets/scaffolds/entitlement-and-paywall.md	Copy-paste StoreKit 2 EntitlementStore + PaywallGate (single source of truth)
assets/scaffolds/push-and-engagement.md	Copy-paste PushManager with deferred opt-in + Reachability
assets/scaffolds/cloudflare-worker-backend.md	Worker scaffold: subscription webhook (idempotent, re-fetch), AI proxy, push

Related Skills

Skill	Purpose
software-mobile	Platform choice and cross-platform tradeoffs
software-ios-runtime-debugging	Build/install/launch proof, stale-build triage, and simulator/package debugging
qa-testing-ios	iOS test execution, xcresult, and simulator stability
agents-memory	Shared AGENTS.md / CLAUDE.md memory strategy
dev-context-engineering	Cross-tool context design for Codex and Claude Code
software-performance	Performance measurement and regression gates
software-ios-design	iOS design patterns, HIG compliance, dark mode, dashboard layout

Freshness Lookups

Freshness-check before final answers on Xcode/SwiftUI/Swift Testing changes, XcodeBuildMCP setup, iOS privacy manifests, App Store requirements, or any "is X still the default?" question. Start from data/sources.json, then Apple Developer docs and WWDC sessions. Prefer Apple docs/release notes for Xcode/SwiftUI/privacy/store; official Anthropic/OpenAI docs for Codex/Claude Code; XcodeBuildMCP repo for tool names and config.

Learnings Loop

When prior decisions or pitfalls are relevant, consult learnings.consolidated.md if present; use learnings.md only for needed history or as the available fallback. Otherwise skip both. After: append one dated bullet to learnings.md via agents-skills-feedback-loop/scripts/append_learning.py. Do not modify SKILL.md.