feat: add liquid glass background effect support

macos/Sources/Features/Terminal/Window Styles/TerminalWindow.swift

@@ -44,6 +44,9 @@ class TerminalWindow: NSWindow {
         true
     }
 
+    /// Glass effect view for liquid glass background when transparency is enabled
+    private var glassEffectView: NSView?
+
     /// Gets the terminal controller from the window controller.
     var terminalController: TerminalController? {
         windowController as? TerminalController
@@ -476,6 +479,11 @@ class TerminalWindow: NSWindow {
             // Terminal.app more easily.
             backgroundColor = .white.withAlphaComponent(0.001)
 
+            // Add liquid glass behind terminal content
+            if #available(macOS 26.0, *), derivedConfig.backgroundGlassStyle != "off" {
+                setupGlassLayer()
+            }
+
             if let appDelegate = NSApp.delegate as? AppDelegate {
                 ghostty_set_window_background_blur(
                     appDelegate.ghostty.app,
@@ -484,6 +492,11 @@ class TerminalWindow: NSWindow {
         } else {
             isOpaque = true
 
+            // Remove liquid glass when not transparent
+            if #available(macOS 26.0, *) {
+                removeGlassLayer()
+            }
+
             let backgroundColor = preferredBackgroundColor ?? NSColor(surfaceConfig.backgroundColor)
             self.backgroundColor = backgroundColor.withAlphaComponent(1)
         }
@@ -562,6 +575,51 @@ class TerminalWindow: NSWindow {
         }
     }
 
+    // MARK: Glass
+    
+    @available(macOS 26.0, *)
+    private func setupGlassLayer() {
+        guard let contentView = contentView else { return }
+
+        // Remove existing glass effect view
+        glassEffectView?.removeFromSuperview()
+
+        // Get the window content view (parent of the NSHostingView)
+        guard let windowContentView = contentView.superview else { return }
+
+        // Create NSGlassEffectView for native glass effect
+        let effectView = NSGlassEffectView()
+
+        // Map Ghostty config to NSGlassEffectView style
+        let glassStyle = derivedConfig.backgroundGlassStyle
+        switch glassStyle {
+        case "regular":
+            effectView.style = NSGlassEffectView.Style.regular
+        case "clear":
+            effectView.style = NSGlassEffectView.Style.clear
+        default:
+            // Should not reach here since we check for "off" before calling setupGlassLayer()
+            return
+        }
+
+        effectView.cornerRadius = 18
+        effectView.tintColor = preferredBackgroundColor
+
+        effectView.frame = windowContentView.bounds
+        effectView.autoresizingMask = [.width, .height]
+
+        // Position BELOW the terminal content to act as background
+        windowContentView.addSubview(effectView, positioned: .below, relativeTo: contentView)
+        glassEffectView = effectView
+    }
+
+    @available(macOS 26.0, *)
+    private func removeGlassLayer() {
+        glassEffectView?.removeFromSuperview()
+        glassEffectView = nil
+    }
+
+>>>>>>> Conflict 4 of 4 ends
     // MARK: Config
 
     struct DerivedConfig {
@@ -569,12 +627,14 @@ class TerminalWindow: NSWindow {
         let backgroundColor: NSColor
         let backgroundOpacity: Double
         let macosWindowButtons: Ghostty.MacOSWindowButtons
+        let backgroundGlassStyle: String
 
         init() {
             self.title = nil
             self.backgroundColor = NSColor.windowBackgroundColor
             self.backgroundOpacity = 1
             self.macosWindowButtons = .visible
+            self.backgroundGlassStyle = "off"
         }
 
         init(_ config: Ghostty.Config) {
@@ -582,6 +642,7 @@ class TerminalWindow: NSWindow {
             self.backgroundColor = NSColor(config.backgroundColor)
             self.backgroundOpacity = config.backgroundOpacity
             self.macosWindowButtons = config.macosWindowButtons
+            self.backgroundGlassStyle = config.backgroundGlassStyle
         }
     }
 }

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -261,6 +261,17 @@ extension Ghostty {
             return MacOSWindowButtons(rawValue: str) ?? defaultValue
         }
 
+        var backgroundGlassStyle: String {
+            let defaultValue = "off"
+            guard let config = self.config else { return defaultValue }
+            var v: UnsafePointer<Int8>? = nil
+            let key = "background-glass-style"
+            guard ghostty_config_get(config, &v, key, UInt(key.count)) else { return defaultValue }
+            guard let ptr = v else { return defaultValue }
+            return String(cString: ptr)
+        }
+
+
         var macosTitlebarStyle: String {
             let defaultValue = "transparent"
             guard let config = self.config else { return defaultValue }
@@ -635,7 +646,7 @@ extension Ghostty.Config {
         static let title = BellFeatures(rawValue: 1 << 3)
         static let border = BellFeatures(rawValue: 1 << 4)
     }
-    
+
     enum MacDockDropBehavior: String {
         case new_tab = "new-tab"
         case new_window = "new-window"

src/config/Config.zig

@@ -950,6 +950,24 @@ palette: Palette = .{},
 /// doing so.
 @"background-blur": BackgroundBlur = .false,
 
+/// The style of the glass effect when `background-opacity` is less than 1
+/// and the terminal is using a modern glass effect (macOS 26.0+ only).
+///
+/// Valid values are:
+///
+///   * `off` - No glass effect
+///   * `regular` - Standard glass effect with some opacity
+///   * `clear` - Highly transparent glass effect
+///
+/// This setting only takes effect on macOS 26.0+ when transparency is enabled
+/// (`background-opacity` < 1). On older macOS versions or when transparency
+/// is disabled, this setting has no effect.
+///
+/// The default value is `off`.
+///
+/// Available since: 1.2.2
+@"background-glass-style": BackgroundGlassStyle = .off,
+
 /// The opacity level (opposite of transparency) of an unfocused split.
 /// Unfocused splits by default are slightly faded out to make it easier to see
 /// which split is focused. To disable this feature, set this value to 1.
@@ -8383,6 +8401,13 @@ pub const BackgroundBlur = union(enum) {
     }
 };
 
+/// See background-glass-style
+pub const BackgroundGlassStyle = enum {
+    off,
+    regular,
+    clear,
+};
+
 /// See window-decoration
 pub const WindowDecoration = enum(c_int) {
     auto,