macOS 26 — Liquid Glass

macOS 26 ("Tahoe") introduces Liquid Glass — a depth-aware translucency that reads the wallpaper behind your window. The Nucleus macOS toolkit ships a DecoratedWindow style that opts into it, plus the right traffic-light layout, sidebar vibrancy and large-corner-radius treatment.

TL;DR

• Ships a TitleBarStyle and DecoratedWindowStyle tuned for macOS Tahoe.
• Opts into Liquid Glass via the Tao backend's MacOSStyle.Liquid window style.
• Traffic-light buttons sit on the left in the standard inset.
• Modifier.macOSLargeCornerRadius() rounds the content under the title bar.
• Falls back to the standard NSWindow chrome on older macOS versions.

Install

dependencies {
    implementation("dev.nucleusframework:nucleus.nucleus-application:<version>")
    implementation("dev.nucleusframework:nucleus.decorated-window-tao:<version>")
    // implementation("dev.nucleusframework:nucleus.decorated-window-macos26:<version>") [FACT-CHECK: artifact id]
}

[FACT-CHECK: artifact id] — the dedicated macOS 26 style pack is announced for Nucleus 2.0. Until its artifact is published, get the Liquid Glass effect through the Tao backend directly (MacOSStyle.Liquid), and style the title bar with decorated-window-core.

The Liquid Glass material requires the macOS SDK 26 to be advertised in the launcher binary's load commands. The Nucleus Gradle plugin handles this via macOsSdkVersion = "26.0" in the macOS distribution settings — the launcher's Mach-O headers are vtool-patched at packaging time.

Quickstart

import androidx.compose.foundation.layout.*
import androidx.compose.material3.Text
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.*
import dev.nucleusframework.application.*
import dev.nucleusframework.window.core.*

fun main() = nucleusApplication(backend = NucleusBackend.Tao) {
    val titleBarStyle = TitleBarStyle(
        colors = TitleBarColors(
            background = Color.Transparent,        // let Liquid Glass show through
            inactiveBackground = Color.Transparent,
            content = Color(0xFFE6E6E6),
            border = Color.Transparent,
        ),
        metrics = TitleBarMetrics(height = 38.dp),
    )

    NucleusDecoratedWindowTheme(isDark = true, titleBarStyle = titleBarStyle) {
        DecoratedWindow(
            onCloseRequest = ::exitApplication,
            title = "Liquid Glass",
        ) {
            TitleBar(modifier = Modifier.macOSLargeCornerRadius()) { _ ->
                Text("Liquid Glass", Modifier.align(Alignment.CenterHorizontally))
            }
            Box(Modifier.fillMaxSize()) { /* content */ }
        }
    }
}

To force Liquid Glass on the Tao window directly, set the style on the native handle:

val taoWindow = nucleusWindow.unsafe.taoWindow ?: return@DecoratedWindow
LaunchedEffect(Unit) {
    taoWindow.setMacOSStyle(MacOSStyle.Liquid)
}

How it works

Liquid Glass is a Cocoa-level material the OS applies to a window's content view when the launcher advertises SDK 26. The Tao backend exposes that toggle as MacOSStyle.Liquid; the macOS toolkit module wires the toggle and the matching title bar style into the same DecoratedWindow you already use.

For the title bar slot, set TitleBarColors.background = Color.Transparent so the Liquid Glass material shows through. Modifier.macOSLargeCornerRadius() matches the rounded-corner geometry NSWindows ship by default. The traffic lights — close, minimise, fullscreen — are drawn by AppKit; you don't need to render them yourself.

Reference

• MacOSStyle.Default — standard NSWindow style.
• MacOSStyle.Liquid — macOS 26 Liquid Glass.
• MacOSStyle.HudWindow — HUD-style translucent panel.
• Modifier.macOSLargeCornerRadius(enabled: Boolean = true) — content rounded corners.
• Modifier.newFullscreenControls() — relayout the title bar in fullscreen.