macos: use a runtime liquid glass check for our Tahoe styling

macos/Ghostty.xcodeproj/project.pbxproj

@@ -90,7 +90,7 @@
 		A5A1F8852A489D6800D1E8BC /* terminfo in Resources */ = {isa = PBXBuildFile; fileRef = A5A1F8842A489D6800D1E8BC /* terminfo */; };
 		A5A2A3CA2D4445E30033CF96 /* Dock.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5A2A3C92D4445E20033CF96 /* Dock.swift */; };
 		A5A2A3CC2D444ABB0033CF96 /* NSApplication+Extension.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5A2A3CB2D444AB80033CF96 /* NSApplication+Extension.swift */; };
-		A5A6F72A2CC41B8900B232A5 /* Xcode.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5A6F7292CC41B8700B232A5 /* Xcode.swift */; };
+		A5A6F72A2CC41B8900B232A5 /* AppInfo.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5A6F7292CC41B8700B232A5 /* AppInfo.swift */; };
 		A5AEB1652D5BE7D000513529 /* LastWindowPosition.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5AEB1642D5BE7BF00513529 /* LastWindowPosition.swift */; };
 		A5B30539299BEAAB0047F10C /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = A5B30538299BEAAB0047F10C /* Assets.xcassets */; };
 		A5CA378C2D2A4DEB00931030 /* KeyboardLayout.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5CA378B2D2A4DE800931030 /* KeyboardLayout.swift */; };
@@ -205,7 +205,7 @@
 		A5A1F8842A489D6800D1E8BC /* terminfo */ = {isa = PBXFileReference; lastKnownFileType = folder; name = terminfo; path = "../zig-out/share/terminfo"; sourceTree = "<group>"; };
 		A5A2A3C92D4445E20033CF96 /* Dock.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Dock.swift; sourceTree = "<group>"; };
 		A5A2A3CB2D444AB80033CF96 /* NSApplication+Extension.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "NSApplication+Extension.swift"; sourceTree = "<group>"; };
-		A5A6F7292CC41B8700B232A5 /* Xcode.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Xcode.swift; sourceTree = "<group>"; };
+		A5A6F7292CC41B8700B232A5 /* AppInfo.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppInfo.swift; sourceTree = "<group>"; };
 		A5AEB1642D5BE7BF00513529 /* LastWindowPosition.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LastWindowPosition.swift; sourceTree = "<group>"; };
 		A5B30531299BEAAA0047F10C /* Ghostty.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Ghostty.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		A5B30538299BEAAB0047F10C /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Assets.xcassets; sourceTree = "<group>"; };
@@ -312,8 +312,8 @@
 			children = (
 				A58636692DF0A98100E04A10 /* Extensions */,
 				A5874D9B2DAD781100E83852 /* Private */,
+				A5A6F7292CC41B8700B232A5 /* AppInfo.swift */,
 				A5AEB1642D5BE7BF00513529 /* LastWindowPosition.swift */,
-				A5A6F7292CC41B8700B232A5 /* Xcode.swift */,
 				A5CEAFFE29C2410700646FDA /* Backport.swift */,
 				A5333E1B2B5A1CE3008AEFF7 /* CrossKit.swift */,
 				A5CBD0572C9F30860017A1AE /* Cursor.swift */,
@@ -756,7 +756,7 @@
 				A52FFF5D2CAB4D08000C6A5B /* NSScreen+Extension.swift in Sources */,
 				A53426352A7DA53D00EBB7A2 /* AppDelegate.swift in Sources */,
 				A5CBD0582C9F30960017A1AE /* Cursor.swift in Sources */,
-				A5A6F72A2CC41B8900B232A5 /* Xcode.swift in Sources */,
+				A5A6F72A2CC41B8900B232A5 /* AppInfo.swift in Sources */,
 				A52FFF5B2CAA54B1000C6A5B /* FullscreenMode+Extension.swift in Sources */,
 				A5333E222B5A2128008AEFF7 /* SurfaceView_AppKit.swift in Sources */,
 				A5CA378E2D31D6C300931030 /* Weak.swift in Sources */,

macos/Sources/Features/Terminal/TerminalController.swift

@@ -16,7 +16,7 @@ class TerminalController: BaseTerminalController {
         case "hidden": "TerminalHiddenTitlebar"
         case "transparent": "TerminalTransparentTitlebar"
         case "tabs":
-            if #available(macOS 26.0, *) {
+            if #available(macOS 26.0, *), hasLiquidGlass() {
                 "TerminalTabsTitlebarTahoe"
             } else {
                 "TerminalTabsTitlebarVentura"

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

@@ -447,7 +447,7 @@ extension TerminalWindow {
         // The padding from the top that the view appears. This was all just manually
         // measured based on the OS.
         var topPadding: CGFloat {
-            if #available(macOS 26.0, *) {
+            if #available(macOS 26.0, *), hasLiquidGlass() {
                 return viewModel.hasToolbar ? 10 : 5
             } else {
                 return viewModel.hasToolbar ? 9 : 4

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

@@ -48,7 +48,7 @@ class TransparentTitlebarTerminalWindow: TerminalWindow {
         
         // On macOS 13 to 15, we need to hide the NSVisualEffectView in order to allow our
         // titlebar to be truly transparent.
-        if #unavailable(macOS 26.0) {
+        if !effectViewIsHidden && !hasLiquidGlass() {
             hideEffectView()
         }
     }
@@ -65,7 +65,7 @@ class TransparentTitlebarTerminalWindow: TerminalWindow {
         // references changed (e.g. tabGroup is new).
         setupKVO()
 
-        if #available(macOS 26.0, *) {
+        if #available(macOS 26.0, *), hasLiquidGlass() {
             syncAppearanceTahoe(surfaceConfig)
         } else {
             syncAppearanceVentura(surfaceConfig)

macos/Sources/Helpers/AppInfo.swift

@@ -0,0 +1,44 @@
+import Foundation
+
+/// True if we appear to be running in Xcode.
+func isRunningInXcode() -> Bool {
+    if let _ = ProcessInfo.processInfo.environment["__XCODE_BUILT_PRODUCTS_DIR_PATHS"] {
+        return true
+    }
+
+    return false
+}
+
+/// True if we have liquid glass available.
+func hasLiquidGlass() -> Bool {
+    // Can't have liquid glass unless we're in macOS 26+
+    if #unavailable(macOS 26.0) {
+        return false
+    }
+
+    // If we aren't running SDK 26.0 or later then we definitely
+    // do not have liquid glass.
+    guard let sdkName = Bundle.main.infoDictionary?["DTSDKName"] as? String else {
+        // If we don't have this, we assume we're built against the latest
+        // since we're on macOS 26+
+        return true
+    }
+
+    // If the SDK doesn't start with macosx then we just assume we
+    // have it because we already verified we're on macOS above.
+    guard sdkName.hasPrefix("macosx") else {
+        return true
+    }
+
+    // The SDK version must be at least 26
+    let versionString = String(sdkName.dropFirst("macosx".count))
+    guard let major = if let dotIndex = versionString.firstIndex(of: ".") {
+        Int(String(versionString[..<dotIndex]))
+    } else {
+        Int(versionString)
+    } else { return true }
+
+    // Note: we could also check for the UIDesignRequiresCompatibility key
+    // but our project doesn't use it so there's no point.
+    return major >= 26
+}

macos/Sources/Helpers/Xcode.swift

@@ -1,10 +0,0 @@
-import Foundation
-
-/// True if we appear to be running in Xcode.
-func isRunningInXcode() -> Bool {
-    if let _ = ProcessInfo.processInfo.environment["__XCODE_BUILT_PRODUCTS_DIR_PATHS"] {
-        return true
-    }
-
-    return false
-}