macOS 26 design system

compose-macos-26-ui is a Compose Multiplatform design system for the macOS 26 look: components, theme tokens, icons, and a desktop MacosDecoratedWindow on the Nucleus Tao backend. It targets Android, iOS, desktop JVM, and web (JS/Wasm). Versioned independently of Nucleus (current release 1.0.0).

Live gallery: nucleusframework.github.io/compose-macos-26-ui.

Add the dependency

plugins {
    id("dev.nucleusframework")
}

dependencies {
    implementation("dev.nucleusframework:compose-macos-ui:1.0.0")
    // optional:
    // implementation("dev.nucleusframework:compose-macos-ui-icons-extended:1.0.0")
    // implementation("dev.nucleusframework:compose-macos-ui-markdown:1.0.0")
}

compose-macos-ui already exposes nucleus.nucleus-application and nucleus.decorated-window-tao as api on the JVM target.

Open a decorated window

import dev.nucleusframework.application.nucleusApplication
import dev.nucleusframework.macoscompose.theme.MacosTheme
import dev.nucleusframework.macoscompose.window.MacosDecoratedWindow

fun main() = nucleusApplication {
    MacosDecoratedWindow(
        onCloseRequest = ::exitApplication,
        title = "Mail",
    ) {
        MacosTheme(darkTheme = false) {
            App()
        }
    }
}

Put MacosTheme inside the window content so native surfaces (traffic lights, glass, clear colour) follow the app theme.

How it works

On desktop, MacosDecoratedWindow wraps Nucleus DecoratedWindow (Tao): full-size content view, large corner radius via a hidden NSToolbar, traffic lights recentred against titleBarHeight, and native materials. Windows and Linux use an undecorated frame with platform controls drawn in the same band.

What's next

• Native design systems
• Window scaffold — full-window layouts without this pack
• Repo README