Ship more than one Kotlin Multiplatform app on the same stack and the shared parts quietly drift — the same TOAD presentation runtime, the same Compose design language, the same ktlint rules and Gradle conventions, duplicated and slowly diverging. rhaydus-foundation is the single, versioned home for everything they share, so a fix or an improvement lands once and every consuming app inherits it.

It ships three things most "shared module" repos don't bother to keep together:

• 📦 Published KMP libraries — drop-in via Maven Central, opt-in by concern.
• 🧰 Build + style tooling — Gradle convention plugins, a shared version catalog, and a custom ktlint ruleset.
• 🤖 Claude Code assets — a plugin of specialist agents, a skill, and a docs index, so an AI assistant working in a consuming app knows what's available and is steered to actually use it.

• Gradle convention plugins (build-logic/): rhaydus.android.library, rhaydus.kmp.library, rhaydus.android.compose, rhaydus.kmp.compose — uniform module setup (SDK/JDK levels, the Android+iOS mobileMain seam, the test stack, Compose).
• Canonical conventions docs (docs/): see CAPABILITIES.md (the index of everything available), plus architecture, TOAD, code-style, and design-system foundations.

graph LR
  editorial["designsystem-editorial<br/><i>editorial language</i>"] --> core["designsystem-core<br/><i>neutral skeleton</i>"]
  image["designsystem-image<br/><i>async images</i>"] --> core
  image -. brings .-> coil["Coil"]
  toad["toad<br/><i>presentation runtime</i>"]
  coreui["core-ui<br/><i>non-visual seams</i>"]

An app that wants a different look depends on designsystem-core alone and never pulls the editorial language or Coil — the opinionated layers are opt-in by design.

// build.gradle.kts
dependencies {
    implementation("nl.rhaydus:toad:0.2.0")
    implementation("nl.rhaydus:designsystem-core:0.2.0")
    implementation("nl.rhaydus:designsystem-editorial:0.2.0") // opt-in
    implementation("nl.rhaydus:designsystem-image:0.2.0")     // opt-in (pulls Coil)
}

Artifacts publish to Maven Central under the nl.rhaydus group (verified by DNS, no server) — consumers need no credentials, just mavenCentral().

// settings.gradle.kts
dependencyResolutionManagement {
    versionCatalogs {
        create("rhaydus") { from("nl.rhaydus:catalog:0.2.0") }
    }
}

While iterating on the foundation and an app together, skip the publish cycle entirely:

# <app>/local.properties
foundation.local=true

The app's settings.gradle.kts reads that flag and includeBuild("../rhaydus-foundation"); Gradle substitutes the published coordinates for local source automatically — no version bumps, instant cross-repo edits. Flip it back to return to the pinned release.

/plugin marketplace add CinqueIzumi/rhaydus-foundation
/plugin install rhaydus-kotlin@rhaydus

The rhaydus-kotlin plugin makes a consuming app's AI assistant fluent in the foundation. It ships:

Every agent reads CAPABILITIES.md first — so it reuses what already exists and stays correct for the exact version a project is pinned to, rather than working from a memorized snapshot.

One version covers the whole release: foundation.version in gradle.properties drives all seven published artifacts, and a verifyPluginVersion build gate locks the Claude plugin's version to it (the build fails if they drift). Bump them together; a tagged push (v*) publishes to Maven Central via CI.

./gradlew build                            # compile all targets (jvm/android/ios) + tests + gates
./gradlew publishToMavenLocal              # local smoke test of the real artifacts
./gradlew publishAndReleaseToMavenCentral  # release (normally done by CI on a v* tag)

Publishing credentials (Central Portal token + PGP key) are maintainer-only, supplied via env/Gradle properties and never committed — see .github/workflows/publish.yml.

A 0.x release: the public API may still change between minor versions before 1.0, so pin a version when you depend on it. Every release builds on all targets (Android / iOS / Desktop) and is verified against a sample consumer before it ships.

MIT © CinqueIzumi