kmp-development

name: kmp-development description: Kotlin Multiplatform shared module development standards for sharing business logic across Android and iOS while keeping native UI. Covers project structure (shared/composeApp/iosApp), source sets, targets, expect/actual, DI (Koin)... metadata: portable: true compatible_with: - Codex - codex

Kotlin Multiplatform Development Standards

Acknowledgement: Shared by Peter Bamuhigire, techguypeter.com, +256 784 464178.

Use When

• Kotlin Multiplatform shared module development standards for sharing business logic across Android and iOS while keeping native UI. Covers project structure (shared/composeApp/iosApp), source sets, targets, expect/actual, DI (Koin)...
• The task needs reusable judgment, domain constraints, or a proven workflow rather than ad hoc advice.

Do Not Use When

• The task is unrelated to kmp-development or would be better handled by a more specific companion skill.
• The request only needs a trivial answer and none of this skill's constraints or references materially help.

Required Inputs

• Gather relevant project context, constraints, and the concrete problem to solve; load references only as needed.
• Confirm the desired deliverable: design, code, review, migration plan, audit, or documentation.

Workflow

• Read this SKILL.md first, then load only the referenced deep-dive files that are necessary for the task.
• Apply the ordered guidance, checklists, and decision rules in this skill instead of cherry-picking isolated snippets.
• Produce the deliverable with assumptions, risks, and follow-up work made explicit when they matter.

Quality Standards

• Keep outputs execution-oriented, concise, and aligned with the repository's baseline engineering standards.
• Preserve compatibility with existing project conventions unless the skill explicitly requires a stronger standard.
• Prefer deterministic, reviewable steps over vague advice or tool-specific magic.

Anti-Patterns

• Treating examples as copy-paste truth without checking fit, constraints, or failure modes.
• Loading every reference file by default instead of using progressive disclosure.

Outputs

• A concrete result that fits the task: implementation guidance, review findings, architecture decisions, templates, or generated artifacts.
• Clear assumptions, tradeoffs, or unresolved gaps when the task cannot be completed from available context alone.
• References used, companion skills, or follow-up actions when they materially improve execution.

Evidence Produced

References

• Use the references/ directory for deep detail after reading the core workflow below.
• references/kmp-compose-multiplatform.md for shared Compose UI across Android, iOS, Desktop, and Web targets.
• references/kmp-tdd.md for shared-module Red-Green-Refactor, common tests, and expect/actual test strategy.
• For iOS targets in 2026+ Apple toolchains, load ../../ios/ios-development/references/apple-platform-compatibility-wwdc26.md and keep SwiftUI-native UI, Xcode 27, Swift 6.4, and availability gates in the iosApp/ module.

Strategy: Shared Logic, Native UI

KMP shares business logic (domain, data, networking) across platforms. Each platform keeps its native UI framework: Jetpack Compose for Android, SwiftUI for iOS. This preserves the best user experience on each platform while eliminating business logic duplication.

Module-to-Skill Mapping

Project Structure

Every KMP project has three modules:

project-root/
  shared/                    # Shared Kotlin module (this skill governs)
    src/
      commonMain/            # Shared code (domain, data, use cases)
        kotlin/
        resources/
      androidMain/           # Android-specific implementations
        kotlin/
        AndroidManifest.xml
      iosMain/               # iOS-specific implementations
        kotlin/
      commonTest/            # Shared tests
      androidUnitTest/       # Android-specific tests
      iosTest/               # iOS-specific tests
    build.gradle.kts         # KMP Gradle config
  composeApp/                # Android app (follow android-development skill)
    src/main/
    build.gradle.kts
  iosApp/                    # iOS Xcode project (follow ios-development skill)
    iosApp/
    iosApp.xcodeproj
  build.gradle.kts           # Root build file
  gradle/libs.versions.toml  # Version catalog

Additional Guidance

Extended guidance for kmp-development was moved to references/skill-deep-dive.md to keep this entrypoint compact and fast to load.

Use that deep dive for:

• Technology Stack
• Source Sets and Targets
• Architecture: Clean Architecture in Shared Module
• Expect/Actual Pattern
• Dependency Injection with Koin
• Networking with Ktor
• Database with SQLDelight
• Modularization
• Native Library Integration
• Tooling
• Mandatory Rules
• Anti-Patterns