Fix theme initialization to respect configured/system appearance (#161)

* Respect configured appearance before Ghostty initialization

* Apply Ghostty theme colors to cmux titlebar and tab chrome

* Fix builtin theme resolution and tab strip icon contrast

* Alias builtin Solarized names to current Ghostty themes

* Sync tab chrome with active Ghostty theme

* Fix system appearance theme switching for surfaces

* Refresh titlebar on background theme updates

* Refresh split overlay config on appearance change

* Update bonsplit for chrome color review fixes

GhosttyTabs.xcodeproj/project.pbxproj

@@ -73,6 +73,7 @@
 				F1000000A1B2C3D4E5F60718 /* CmuxWebViewKeyEquivalentTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = F1000001A1B2C3D4E5F60718 /* CmuxWebViewKeyEquivalentTests.swift */; };
 				F2000000A1B2C3D4E5F60718 /* UpdatePillReleaseVisibilityTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = F2000001A1B2C3D4E5F60718 /* UpdatePillReleaseVisibilityTests.swift */; };
 				F3000000A1B2C3D4E5F60718 /* CJKIMEInputTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = F3000001A1B2C3D4E5F60718 /* CJKIMEInputTests.swift */; };
+				F4000000A1B2C3D4E5F60718 /* GhosttyConfigTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = F4000001A1B2C3D4E5F60718 /* GhosttyConfigTests.swift */; };
 		/* End PBXBuildFile section */
 
 /* Begin PBXCopyFilesBuildPhase section */
@@ -193,6 +194,7 @@
 			F1000001A1B2C3D4E5F60718 /* CmuxWebViewKeyEquivalentTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CmuxWebViewKeyEquivalentTests.swift; sourceTree = "<group>"; };
 			F2000001A1B2C3D4E5F60718 /* UpdatePillReleaseVisibilityTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UpdatePillReleaseVisibilityTests.swift; sourceTree = "<group>"; };
 			F3000001A1B2C3D4E5F60718 /* CJKIMEInputTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CJKIMEInputTests.swift; sourceTree = "<group>"; };
+			F4000001A1B2C3D4E5F60718 /* GhosttyConfigTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GhosttyConfigTests.swift; sourceTree = "<group>"; };
 		/* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -396,6 +398,7 @@
 				F1000001A1B2C3D4E5F60718 /* CmuxWebViewKeyEquivalentTests.swift */,
 				F2000001A1B2C3D4E5F60718 /* UpdatePillReleaseVisibilityTests.swift */,
 				F3000001A1B2C3D4E5F60718 /* CJKIMEInputTests.swift */,
+				F4000001A1B2C3D4E5F60718 /* GhosttyConfigTests.swift */,
 			);
 			path = cmuxTests;
 			sourceTree = "<group>";
@@ -594,6 +597,7 @@
 				F1000000A1B2C3D4E5F60718 /* CmuxWebViewKeyEquivalentTests.swift in Sources */,
 				F2000000A1B2C3D4E5F60718 /* UpdatePillReleaseVisibilityTests.swift in Sources */,
 				F3000000A1B2C3D4E5F60718 /* CJKIMEInputTests.swift in Sources */,
+				F4000000A1B2C3D4E5F60718 /* GhosttyConfigTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Sources/ContentView.swift

@@ -390,7 +390,6 @@ func installFileDropOverlay(on window: NSWindow, tabManager: TabManager) {
 struct ContentView: View {
     @ObservedObject var updateViewModel: UpdateViewModel
     let windowId: UUID
-    @Environment(\.colorScheme) private var colorScheme
     @EnvironmentObject var tabManager: TabManager
     @EnvironmentObject var notificationStore: TerminalNotificationStore
     @EnvironmentObject var sidebarState: SidebarState
@@ -411,6 +410,7 @@ struct ContentView: View {
     @State private var retiringWorkspaceId: UUID?
     @State private var workspaceHandoffGeneration: UInt64 = 0
     @State private var workspaceHandoffFallbackTask: Task<Void, Never>?
+    @State private var titlebarThemeGeneration: UInt64 = 0
 
     private var sidebarView: some View {
         VerticalTabsSidebar(
@@ -533,18 +533,26 @@ struct ContentView: View {
     @State private var titlebarLeadingInset: CGFloat = 12
     private var windowIdentifier: String { "cmux.main.\(windowId.uuidString)" }
     private var fakeTitlebarBackground: Color {
-        if colorScheme == .light {
-            return Color(nsColor: .windowBackgroundColor)
-        }
+        _ = titlebarThemeGeneration
         let ghosttyBackground = GhosttyApp.shared.defaultBackgroundColor
-        let alpha: CGFloat = ghosttyBackground.isLightColor ? 0.94 : 0.86
-        return Color(nsColor: ghosttyBackground.withAlphaComponent(alpha))
+        let configuredOpacity = CGFloat(max(0, min(1, GhosttyApp.shared.defaultBackgroundOpacity)))
+        let minimumChromeOpacity: CGFloat = ghosttyBackground.isLightColor ? 0.90 : 0.84
+        let chromeOpacity = max(minimumChromeOpacity, configuredOpacity)
+        return Color(nsColor: ghosttyBackground.withAlphaComponent(chromeOpacity))
     }
     private var fakeTitlebarTextColor: Color {
-        colorScheme == .light ? Color(nsColor: .labelColor).opacity(0.78) : .secondary
+        _ = titlebarThemeGeneration
+        let ghosttyBackground = GhosttyApp.shared.defaultBackgroundColor
+        return ghosttyBackground.isLightColor
+            ? Color.black.opacity(0.78)
+            : Color.white.opacity(0.82)
     }
     private var fakeTitlebarSeparatorColor: Color {
-        Color(nsColor: .separatorColor).opacity(colorScheme == .light ? 0.68 : 0.34)
+        _ = titlebarThemeGeneration
+        let ghosttyBackground = GhosttyApp.shared.defaultBackgroundColor
+        return ghosttyBackground.isLightColor
+            ? Color.black.opacity(0.18)
+            : Color.white.opacity(0.22)
     }
 
     private var fullscreenControls: some View {
@@ -729,6 +737,12 @@ struct ContentView: View {
             completeWorkspaceHandoffIfNeeded(focusedTabId: tabId, reason: "focus")
             updateTitlebarText()
         }
+        .onReceive(NotificationCenter.default.publisher(for: .ghosttyConfigDidReload)) { _ in
+            titlebarThemeGeneration &+= 1
+        }
+        .onReceive(NotificationCenter.default.publisher(for: .ghosttyDefaultBackgroundDidChange)) { _ in
+            titlebarThemeGeneration &+= 1
+        }
         .onReceive(NotificationCenter.default.publisher(for: .ghosttyDidBecomeFirstResponderSurface)) { notification in
             guard let tabId = notification.userInfo?[GhosttyNotificationKey.tabId] as? UUID,
                   tabId == tabManager.selectedTabId else { return }

Sources/GhosttyConfig.swift

@@ -2,6 +2,11 @@ import Foundation
 import AppKit
 
 struct GhosttyConfig {
+    enum ColorSchemePreference {
+        case light
+        case dark
+    }
+
     var fontFamily: String = "Menlo"
     var fontSize: CGFloat = 12
     var theme: String?
@@ -145,24 +150,214 @@ struct GhosttyConfig {
     }
 
     mutating func loadTheme(_ name: String) {
-        let bundleThemePath = Bundle.main.resourceURL?
-            .appendingPathComponent("ghostty/themes/\(name)")
-            .path
+        loadTheme(
+            name,
+            environment: ProcessInfo.processInfo.environment,
+            bundleResourceURL: Bundle.main.resourceURL
+        )
+    }
 
-        let themePaths = [
-            bundleThemePath,
-            "/Applications/Ghostty.app/Contents/Resources/ghostty/themes/\(name)",
-            NSString(string: "~/.config/ghostty/themes/\(name)").expandingTildeInPath,
-        ].compactMap { $0 }
-
-        for path in themePaths {
-            if let contents = try? String(contentsOfFile: path, encoding: .utf8) {
-                parse(contents)
-                return
+    mutating func loadTheme(
+        _ name: String,
+        environment: [String: String],
+        bundleResourceURL: URL?,
+        preferredColorScheme: ColorSchemePreference? = nil
+    ) {
+        let resolvedThemeName = Self.resolveThemeName(
+            from: name,
+            preferredColorScheme: preferredColorScheme ?? Self.currentColorSchemePreference()
+        )
+        for candidateName in Self.themeNameCandidates(from: resolvedThemeName) {
+            for path in Self.themeSearchPaths(
+                forThemeName: candidateName,
+                environment: environment,
+                bundleResourceURL: bundleResourceURL
+            ) {
+                if let contents = try? String(contentsOfFile: path, encoding: .utf8) {
+                    parse(contents)
+                    return
+                }
             }
         }
     }
 
+    static func currentColorSchemePreference(
+        appAppearance: NSAppearance? = NSApp?.effectiveAppearance
+    ) -> ColorSchemePreference {
+        let bestMatch = appAppearance?.bestMatch(from: [.darkAqua, .aqua])
+        return bestMatch == .darkAqua ? .dark : .light
+    }
+
+    static func resolveThemeName(
+        from rawThemeValue: String,
+        preferredColorScheme: ColorSchemePreference
+    ) -> String {
+        var fallbackTheme: String?
+        var lightTheme: String?
+        var darkTheme: String?
+
+        for token in rawThemeValue.split(separator: ",").map(String.init) {
+            let entry = token.trimmingCharacters(in: .whitespacesAndNewlines)
+            guard !entry.isEmpty else { continue }
+
+            let parts = entry.split(separator: ":", maxSplits: 1).map(String.init)
+            if parts.count != 2 {
+                if fallbackTheme == nil {
+                    fallbackTheme = entry
+                }
+                continue
+            }
+
+            let key = parts[0].trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
+            let value = parts[1].trimmingCharacters(in: .whitespacesAndNewlines)
+            guard !value.isEmpty else { continue }
+
+            switch key {
+            case "light":
+                if lightTheme == nil {
+                    lightTheme = value
+                }
+            case "dark":
+                if darkTheme == nil {
+                    darkTheme = value
+                }
+            default:
+                if fallbackTheme == nil {
+                    fallbackTheme = value
+                }
+            }
+        }
+
+        switch preferredColorScheme {
+        case .light:
+            if let lightTheme {
+                return lightTheme
+            }
+        case .dark:
+            if let darkTheme {
+                return darkTheme
+            }
+        }
+
+        if let fallbackTheme {
+            return fallbackTheme
+        }
+        if let darkTheme {
+            return darkTheme
+        }
+        if let lightTheme {
+            return lightTheme
+        }
+        return rawThemeValue.trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+
+    static func themeNameCandidates(from rawName: String) -> [String] {
+        var candidates: [String] = []
+        let compatibilityAliases: [String: [String]] = [
+            "solarized light": ["iTerm2 Solarized Light"],
+            "solarized dark": ["iTerm2 Solarized Dark"],
+        ]
+
+        func appendCandidate(_ value: String) {
+            let trimmed = value.trimmingCharacters(in: .whitespacesAndNewlines)
+            guard !trimmed.isEmpty else { return }
+            if !candidates.contains(trimmed) {
+                candidates.append(trimmed)
+            }
+
+            if let aliases = compatibilityAliases[trimmed.lowercased()] {
+                for alias in aliases {
+                    if !candidates.contains(alias) {
+                        candidates.append(alias)
+                    }
+                }
+            }
+        }
+
+        var queue: [String] = [rawName]
+        while let current = queue.popLast() {
+            let trimmed = current.trimmingCharacters(in: .whitespacesAndNewlines)
+            guard !trimmed.isEmpty else { continue }
+
+            appendCandidate(trimmed)
+
+            let lower = trimmed.lowercased()
+            if lower.hasPrefix("builtin ") {
+                let stripped = String(trimmed.dropFirst("builtin ".count))
+                appendCandidate(stripped)
+                queue.append(stripped)
+            }
+
+            if let range = trimmed.range(
+                of: #"\s*\(builtin\)\s*$"#,
+                options: [.regularExpression, .caseInsensitive]
+            ) {
+                let stripped = String(trimmed[..<range.lowerBound])
+                appendCandidate(stripped)
+                queue.append(stripped)
+            }
+        }
+
+        return candidates
+    }
+
+    static func themeSearchPaths(
+        forThemeName themeName: String,
+        environment: [String: String],
+        bundleResourceURL: URL?
+    ) -> [String] {
+        var paths: [String] = []
+
+        func appendUniquePath(_ path: String?) {
+            guard let path else { return }
+            let expanded = NSString(string: path).expandingTildeInPath
+            guard !expanded.isEmpty else { return }
+            if !paths.contains(expanded) {
+                paths.append(expanded)
+            }
+        }
+
+        func appendThemePath(in resourcesRoot: String?) {
+            guard let resourcesRoot else { return }
+            let expanded = NSString(string: resourcesRoot).expandingTildeInPath
+            guard !expanded.isEmpty else { return }
+            appendUniquePath(
+                URL(fileURLWithPath: expanded)
+                    .appendingPathComponent("themes/\(themeName)")
+                    .path
+            )
+        }
+
+        // 1) Explicit resources dir used by the running Ghostty embedding.
+        appendThemePath(in: environment["GHOSTTY_RESOURCES_DIR"])
+
+        // 2) App bundle resources.
+        appendUniquePath(
+            bundleResourceURL?
+                .appendingPathComponent("ghostty/themes/\(themeName)")
+                .path
+        )
+
+        // 3) Data dirs (Ghostty installs themes under share/ghostty/themes).
+        if let xdgDataDirs = environment["XDG_DATA_DIRS"] {
+            for dataDir in xdgDataDirs.split(separator: ":").map(String.init) {
+                guard !dataDir.isEmpty else { continue }
+                appendUniquePath(
+                    URL(fileURLWithPath: dataDir)
+                        .appendingPathComponent("ghostty/themes/\(themeName)")
+                        .path
+                )
+            }
+        }
+
+        // 4) Common system/user fallback locations.
+        appendUniquePath("/Applications/Ghostty.app/Contents/Resources/ghostty/themes/\(themeName)")
+        appendUniquePath("~/.config/ghostty/themes/\(themeName)")
+        appendUniquePath("~/Library/Application Support/com.mitchellh.ghostty/themes/\(themeName)")
+
+        return paths
+    }
+
     private static func readConfigFile(at path: String) -> String? {
         let fileManager = FileManager.default
         guard fileManager.fileExists(atPath: path) else { return nil }

Sources/GhosttyTerminalView.swift

@@ -418,6 +418,7 @@ class GhosttyApp {
             guard let app = self?.app else { return }
             ghostty_app_set_focus(app, false)
         })
+
         #endif
     }
 
@@ -523,6 +524,8 @@ class GhosttyApp {
 
     private func updateDefaultBackground(from config: ghostty_config_t?) {
         guard let config else { return }
+        let previousHex = defaultBackgroundColor.hexString()
+        let previousOpacity = defaultBackgroundOpacity
 
         var color = ghostty_config_color_s()
         let bgKey = "background"
@@ -539,11 +542,35 @@ class GhosttyApp {
         let opacityKey = "background-opacity"
         _ = ghostty_config_get(config, &opacity, opacityKey, UInt(opacityKey.lengthOfBytes(using: .utf8)))
         defaultBackgroundOpacity = opacity
+        let hasChanged = previousHex != defaultBackgroundColor.hexString() ||
+            abs(previousOpacity - defaultBackgroundOpacity) > 0.0001
+        if hasChanged {
+            notifyDefaultBackgroundDidChange()
+        }
         if backgroundLogEnabled {
             logBackground("default background updated color=\(defaultBackgroundColor) opacity=\(String(format: "%.3f", defaultBackgroundOpacity))")
         }
     }
 
+    private func notifyDefaultBackgroundDidChange() {
+        let userInfo: [AnyHashable: Any] = [
+            GhosttyNotificationKey.backgroundColor: defaultBackgroundColor,
+            GhosttyNotificationKey.backgroundOpacity: defaultBackgroundOpacity
+        ]
+        let post = {
+            NotificationCenter.default.post(
+                name: .ghosttyDefaultBackgroundDidChange,
+                object: nil,
+                userInfo: userInfo
+            )
+        }
+        if Thread.isMainThread {
+            post()
+        } else {
+            DispatchQueue.main.async(execute: post)
+        }
+    }
+
     private func performOnMain<T>(_ work: @MainActor () -> T) -> T {
         if Thread.isMainThread {
             return MainActor.assumeIsolated { work() }
@@ -635,6 +662,7 @@ class GhosttyApp {
                 if backgroundLogEnabled {
                     logBackground("OSC background change (app target) color=\(defaultBackgroundColor)")
                 }
+                notifyDefaultBackgroundDidChange()
                 DispatchQueue.main.async {
                     GhosttyApp.shared.applyBackgroundToKeyWindow()
                 }
@@ -1537,6 +1565,7 @@ class GhosttyNSView: NSView, NSUserInterfaceValidations {
     var onFocus: (() -> Void)?
     var onTriggerFlash: (() -> Void)?
     var backgroundColor: NSColor?
+    private var appliedColorScheme: ghostty_color_scheme_e?
     private var keySequence: [ghostty_input_trigger_s] = []
     private var keyTables: [String] = []
 #if DEBUG
@@ -1647,11 +1676,13 @@ class GhosttyNSView: NSView, NSUserInterfaceValidations {
     }
 
     func attachSurface(_ surface: TerminalSurface) {
+        appliedColorScheme = nil
         terminalSurface = surface
         tabId = surface.tabId
         surface.attachToView(self)
         updateSurfaceSize()
         applySurfaceBackground()
+        applySurfaceColorScheme(force: true)
     }
 
     override func viewDidMoveToWindow() {
@@ -1698,9 +1729,15 @@ class GhosttyNSView: NSView, NSUserInterfaceValidations {
         }()
         updateSurfaceSize(size: targetSize)
         applySurfaceBackground()
+        applySurfaceColorScheme(force: true)
         applyWindowBackgroundIfActive()
     }
 
+    override func viewDidChangeEffectiveAppearance() {
+        super.viewDidChangeEffectiveAppearance()
+        applySurfaceColorScheme()
+    }
+
     fileprivate func updateOcclusionState() {
         // Intentionally no-op: we don't drive libghostty occlusion from AppKit occlusion state.
         // This avoids transient clears during reparenting and keeps rendering logic minimal.
@@ -1833,6 +1870,19 @@ class GhosttyNSView: NSView, NSUserInterfaceValidations {
         terminalSurface?.surface
     }
 
+    private func applySurfaceColorScheme(force: Bool = false) {
+        guard let surface else { return }
+        let bestMatch = effectiveAppearance.bestMatch(from: [.darkAqua, .aqua])
+        let scheme: ghostty_color_scheme_e = bestMatch == .darkAqua
+            ? GHOSTTY_COLOR_SCHEME_DARK
+            : GHOSTTY_COLOR_SCHEME_LIGHT
+        if !force, appliedColorScheme == scheme {
+            return
+        }
+        ghostty_surface_set_color_scheme(surface, scheme)
+        appliedColorScheme = scheme
+    }
+
     @discardableResult
     private func ensureSurfaceReadyForInput() -> ghostty_surface_t? {
         if let surface = surface {
@@ -1841,6 +1891,7 @@ class GhosttyNSView: NSView, NSUserInterfaceValidations {
         guard window != nil else { return nil }
         terminalSurface?.attachToView(self)
         updateSurfaceSize(size: bounds.size)
+        applySurfaceColorScheme(force: true)
         return surface
     }
 
@@ -2732,6 +2783,8 @@ enum GhosttyNotificationKey {
     static let tabId = "ghostty.tabId"
     static let surfaceId = "ghostty.surfaceId"
     static let title = "ghostty.title"
+    static let backgroundColor = "ghostty.backgroundColor"
+    static let backgroundOpacity = "ghostty.backgroundOpacity"
 }
 
 extension Notification.Name {
@@ -2739,6 +2792,7 @@ extension Notification.Name {
     static let ghosttyDidUpdateCellSize = Notification.Name("ghosttyDidUpdateCellSize")
     static let ghosttySearchFocus = Notification.Name("ghosttySearchFocus")
     static let ghosttyConfigDidReload = Notification.Name("ghosttyConfigDidReload")
+    static let ghosttyDefaultBackgroundDidChange = Notification.Name("ghosttyDefaultBackgroundDidChange")
 }
 
 // MARK: - Scroll View Wrapper (Ghostty-style scrollbar)

Sources/Workspace.swift

@@ -1,5 +1,6 @@
 import Foundation
 import SwiftUI
+import AppKit
 import Bonsplit
 import Combine
 
@@ -101,6 +102,29 @@ final class Workspace: Identifiable, ObservableObject {
 
     // MARK: - Initialization
 
+    private static func bonsplitAppearance(from config: GhosttyConfig) -> BonsplitConfiguration.Appearance {
+        bonsplitAppearance(from: config.backgroundColor)
+    }
+
+    private static func bonsplitAppearance(from backgroundColor: NSColor) -> BonsplitConfiguration.Appearance {
+        BonsplitConfiguration.Appearance(
+            enableAnimations: false,
+            chromeColors: .init(backgroundHex: backgroundColor.hexString())
+        )
+    }
+
+    func applyGhosttyChrome(from config: GhosttyConfig) {
+        applyGhosttyChrome(backgroundColor: config.backgroundColor)
+    }
+
+    func applyGhosttyChrome(backgroundColor: NSColor) {
+        let nextHex = backgroundColor.hexString()
+        if bonsplitController.configuration.appearance.chromeColors.backgroundHex == nextHex {
+            return
+        }
+        bonsplitController.configuration.appearance.chromeColors.backgroundHex = nextHex
+    }
+
     init(title: String = "Terminal", workingDirectory: String? = nil) {
         self.id = UUID()
         self.processTitle = title
@@ -115,9 +139,7 @@ final class Workspace: Identifiable, ObservableObject {
 
         // Configure bonsplit with keepAllAlive to preserve terminal state
         // Disable split animations for instant response
-        let appearance = BonsplitConfiguration.Appearance(
-            enableAnimations: false
-        )
+        let appearance = Self.bonsplitAppearance(from: GhosttyConfig.load())
         let config = BonsplitConfiguration(
             allowSplits: true,
             allowCloseTabs: true,

Sources/WorkspaceContentView.swift

@@ -1,5 +1,6 @@
 import SwiftUI
 import Foundation
+import AppKit
 import Bonsplit
 
 /// View that renders a Workspace's content using BonsplitView
@@ -9,6 +10,7 @@ struct WorkspaceContentView: View {
     let isWorkspaceInputActive: Bool
     let workspacePortalPriority: Int
     @State private var config = GhosttyConfig.load()
+    @Environment(\.colorScheme) private var colorScheme
     @EnvironmentObject var notificationStore: TerminalNotificationStore
 
     var body: some View {
@@ -82,12 +84,24 @@ struct WorkspaceContentView: View {
         .frame(maxWidth: .infinity, maxHeight: .infinity)
         .onAppear {
             syncBonsplitNotificationBadges()
+            workspace.applyGhosttyChrome(backgroundColor: GhosttyApp.shared.defaultBackgroundColor)
         }
         .onChange(of: notificationStore.notifications) { _, _ in
             syncBonsplitNotificationBadges()
         }
         .onReceive(NotificationCenter.default.publisher(for: .ghosttyConfigDidReload)) { _ in
-            config = GhosttyConfig.load()
+            refreshGhosttyAppearanceConfig()
+        }
+        .onChange(of: colorScheme) { _, _ in
+            // Keep split overlay color/opacity in sync with light/dark theme transitions.
+            refreshGhosttyAppearanceConfig()
+        }
+        .onReceive(NotificationCenter.default.publisher(for: .ghosttyDefaultBackgroundDidChange)) { notification in
+            if let backgroundColor = notification.userInfo?[GhosttyNotificationKey.backgroundColor] as? NSColor {
+                workspace.applyGhosttyChrome(backgroundColor: backgroundColor)
+            } else {
+                workspace.applyGhosttyChrome(backgroundColor: GhosttyApp.shared.defaultBackgroundColor)
+            }
         }
     }
 
@@ -108,6 +122,12 @@ struct WorkspaceContentView: View {
             }
         }
     }
+
+    private func refreshGhosttyAppearanceConfig() {
+        let next = GhosttyConfig.load()
+        config = next
+        workspace.applyGhosttyChrome(from: next)
+    }
 }
 
 extension WorkspaceContentView {

Sources/cmuxApp.swift

@@ -4,12 +4,12 @@ import Darwin
 
 @main
 struct cmuxApp: App {
-    @StateObject private var tabManager = TabManager()
+    @StateObject private var tabManager: TabManager
     @StateObject private var notificationStore = TerminalNotificationStore.shared
     @StateObject private var sidebarState = SidebarState()
     @StateObject private var sidebarSelectionState = SidebarSelectionState()
     private let primaryWindowId = UUID()
-    @AppStorage("appearanceMode") private var appearanceMode = AppearanceMode.dark.rawValue
+    @AppStorage(AppearanceSettings.appearanceModeKey) private var appearanceMode = AppearanceSettings.defaultMode.rawValue
     @AppStorage("titlebarControlsStyle") private var titlebarControlsStyle = TitlebarControlsStyle.classic.rawValue
     @AppStorage(ShortcutHintDebugSettings.alwaysShowHintsKey) private var alwaysShowShortcutHints = ShortcutHintDebugSettings.defaultAlwaysShowHints
     @AppStorage(SocketControlSettings.appStorageKey) private var socketControlMode = SocketControlSettings.defaultMode.rawValue
@@ -18,7 +18,11 @@ struct cmuxApp: App {
     @NSApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate
 
     init() {
-        configureGhosttyEnvironment()
+        Self.configureGhosttyEnvironment()
+
+        let startupAppearance = AppearanceSettings.resolvedMode()
+        Self.applyAppearance(startupAppearance)
+        _tabManager = StateObject(wrappedValue: TabManager())
         // Migrate legacy and old-format socket mode values to the new enum.
         let defaults = UserDefaults.standard
         if let stored = defaults.string(forKey: SocketControlSettings.appStorageKey) {
@@ -37,7 +41,7 @@ struct cmuxApp: App {
         appDelegate.configure(tabManager: tabManager, notificationStore: notificationStore, sidebarState: sidebarState)
     }
 
-    private func configureGhosttyEnvironment() {
+    private static func configureGhosttyEnvironment() {
         let fileManager = FileManager.default
         let ghosttyAppResources = "/Applications/Ghostty.app/Contents/Resources/ghostty"
         let bundledGhosttyURL = Bundle.main.resourceURL?.appendingPathComponent("ghostty")
@@ -82,7 +86,7 @@ struct cmuxApp: App {
         }
     }
 
-    private func appendEnvPathIfMissing(_ key: String, path: String, defaultValue: String? = nil) {
+    private static func appendEnvPathIfMissing(_ key: String, path: String, defaultValue: String? = nil) {
         if path.isEmpty { return }
         var current = getenv(key).flatMap { String(cString: $0) } ?? ""
         if current.isEmpty, let defaultValue {
@@ -496,18 +500,23 @@ struct cmuxApp: App {
     }
 
     private func applyAppearance() {
-        guard let mode = AppearanceMode(rawValue: appearanceMode) else { return }
+        let mode = AppearanceSettings.mode(for: appearanceMode)
+        if appearanceMode != mode.rawValue {
+            appearanceMode = mode.rawValue
+        }
+        Self.applyAppearance(mode)
+    }
+
+    private static func applyAppearance(_ mode: AppearanceMode) {
         switch mode {
         case .system:
-            NSApp.appearance = nil
+            NSApplication.shared.appearance = nil
         case .light:
-            NSApp.appearance = NSAppearance(named: .aqua)
+            NSApplication.shared.appearance = NSAppearance(named: .aqua)
         case .dark:
-            NSApp.appearance = NSAppearance(named: .darkAqua)
+            NSApplication.shared.appearance = NSAppearance(named: .darkAqua)
         case .auto:
-            // Legacy value; treat like system and migrate.
-            NSApp.appearance = nil
-            appearanceMode = AppearanceMode.system.rawValue
+            NSApplication.shared.appearance = nil
         }
     }
 
@@ -2229,11 +2238,36 @@ enum AppearanceMode: String, CaseIterable, Identifiable {
     }
 }
 
+enum AppearanceSettings {
+    static let appearanceModeKey = "appearanceMode"
+    static let defaultMode: AppearanceMode = .system
+
+    static func mode(for rawValue: String?) -> AppearanceMode {
+        guard let rawValue, let mode = AppearanceMode(rawValue: rawValue) else {
+            return defaultMode
+        }
+        if mode == .auto {
+            return .system
+        }
+        return mode
+    }
+
+    @discardableResult
+    static func resolvedMode(defaults: UserDefaults = .standard) -> AppearanceMode {
+        let stored = defaults.string(forKey: appearanceModeKey)
+        let resolved = mode(for: stored)
+        if stored != resolved.rawValue {
+            defaults.set(resolved.rawValue, forKey: appearanceModeKey)
+        }
+        return resolved
+    }
+}
+
 struct SettingsView: View {
     private let contentTopInset: CGFloat = 8
     private let pickerColumnWidth: CGFloat = 196
 
-    @AppStorage("appearanceMode") private var appearanceMode = AppearanceMode.dark.rawValue
+    @AppStorage(AppearanceSettings.appearanceModeKey) private var appearanceMode = AppearanceSettings.defaultMode.rawValue
     @AppStorage(SocketControlSettings.appStorageKey) private var socketControlMode = SocketControlSettings.defaultMode.rawValue
     @AppStorage("claudeCodeHooksEnabled") private var claudeCodeHooksEnabled = true
     @AppStorage(BrowserSearchSettings.searchEngineKey) private var browserSearchEngine = BrowserSearchSettings.defaultSearchEngine.rawValue
@@ -2525,7 +2559,7 @@ struct SettingsView: View {
     }
 
     private func resetAllSettings() {
-        appearanceMode = AppearanceMode.dark.rawValue
+        appearanceMode = AppearanceSettings.defaultMode.rawValue
         socketControlMode = SocketControlSettings.defaultMode.rawValue
         claudeCodeHooksEnabled = true
         browserSearchEngine = BrowserSearchSettings.defaultSearchEngine.rawValue

cmuxTests/CmuxWebViewKeyEquivalentTests.swift

@@ -339,6 +339,110 @@ final class WorkspacePlacementSettingsTests: XCTestCase {
     }
 }
 
+final class AppearanceSettingsTests: XCTestCase {
+    func testResolvedModeDefaultsToSystemWhenUnset() {
+        let suiteName = "AppearanceSettingsTests.Default.\(UUID().uuidString)"
+        guard let defaults = UserDefaults(suiteName: suiteName) else {
+            XCTFail("Failed to create isolated UserDefaults suite")
+            return
+        }
+        defer { defaults.removePersistentDomain(forName: suiteName) }
+
+        defaults.removeObject(forKey: AppearanceSettings.appearanceModeKey)
+
+        let resolved = AppearanceSettings.resolvedMode(defaults: defaults)
+        XCTAssertEqual(resolved, .system)
+        XCTAssertEqual(defaults.string(forKey: AppearanceSettings.appearanceModeKey), AppearanceMode.system.rawValue)
+    }
+
+    func testResolvedModeMigratesLegacyAndInvalidValuesToSystem() {
+        let suiteName = "AppearanceSettingsTests.Migrate.\(UUID().uuidString)"
+        guard let defaults = UserDefaults(suiteName: suiteName) else {
+            XCTFail("Failed to create isolated UserDefaults suite")
+            return
+        }
+        defer { defaults.removePersistentDomain(forName: suiteName) }
+
+        defaults.set(AppearanceMode.auto.rawValue, forKey: AppearanceSettings.appearanceModeKey)
+        XCTAssertEqual(AppearanceSettings.resolvedMode(defaults: defaults), .system)
+        XCTAssertEqual(defaults.string(forKey: AppearanceSettings.appearanceModeKey), AppearanceMode.system.rawValue)
+
+        defaults.set("invalid-value", forKey: AppearanceSettings.appearanceModeKey)
+        XCTAssertEqual(AppearanceSettings.resolvedMode(defaults: defaults), .system)
+        XCTAssertEqual(defaults.string(forKey: AppearanceSettings.appearanceModeKey), AppearanceMode.system.rawValue)
+    }
+
+    func testResolvedModePreservesExplicitLightAndDark() {
+        let suiteName = "AppearanceSettingsTests.Preserve.\(UUID().uuidString)"
+        guard let defaults = UserDefaults(suiteName: suiteName) else {
+            XCTFail("Failed to create isolated UserDefaults suite")
+            return
+        }
+        defer { defaults.removePersistentDomain(forName: suiteName) }
+
+        defaults.set(AppearanceMode.light.rawValue, forKey: AppearanceSettings.appearanceModeKey)
+        XCTAssertEqual(AppearanceSettings.resolvedMode(defaults: defaults), .light)
+        XCTAssertEqual(defaults.string(forKey: AppearanceSettings.appearanceModeKey), AppearanceMode.light.rawValue)
+
+        defaults.set(AppearanceMode.dark.rawValue, forKey: AppearanceSettings.appearanceModeKey)
+        XCTAssertEqual(AppearanceSettings.resolvedMode(defaults: defaults), .dark)
+        XCTAssertEqual(defaults.string(forKey: AppearanceSettings.appearanceModeKey), AppearanceMode.dark.rawValue)
+    }
+}
+
+final class UpdateChannelSettingsTests: XCTestCase {
+    func testDefaultNightlyPreferenceIsDisabled() {
+        XCTAssertFalse(UpdateChannelSettings.defaultIncludeNightlyBuilds)
+    }
+
+    func testResolvedFeedFallsBackToStableWhenInfoFeedMissing() {
+        let suiteName = "UpdateChannelSettingsTests.MissingInfo.\(UUID().uuidString)"
+        guard let defaults = UserDefaults(suiteName: suiteName) else {
+            XCTFail("Failed to create isolated UserDefaults suite")
+            return
+        }
+        defer { defaults.removePersistentDomain(forName: suiteName) }
+
+        let resolved = UpdateChannelSettings.resolvedFeedURLString(infoFeedURL: nil, defaults: defaults)
+        XCTAssertEqual(resolved.url, UpdateChannelSettings.stableFeedURL)
+        XCTAssertFalse(resolved.isNightly)
+        XCTAssertTrue(resolved.usedFallback)
+    }
+
+    func testResolvedFeedUsesInfoFeedForStableChannel() {
+        let suiteName = "UpdateChannelSettingsTests.InfoFeed.\(UUID().uuidString)"
+        guard let defaults = UserDefaults(suiteName: suiteName) else {
+            XCTFail("Failed to create isolated UserDefaults suite")
+            return
+        }
+        defer { defaults.removePersistentDomain(forName: suiteName) }
+
+        let infoFeed = "https://example.com/custom/appcast.xml"
+        let resolved = UpdateChannelSettings.resolvedFeedURLString(infoFeedURL: infoFeed, defaults: defaults)
+        XCTAssertEqual(resolved.url, infoFeed)
+        XCTAssertFalse(resolved.isNightly)
+        XCTAssertFalse(resolved.usedFallback)
+    }
+
+    func testResolvedFeedUsesNightlyWhenPreferenceEnabled() {
+        let suiteName = "UpdateChannelSettingsTests.Nightly.\(UUID().uuidString)"
+        guard let defaults = UserDefaults(suiteName: suiteName) else {
+            XCTFail("Failed to create isolated UserDefaults suite")
+            return
+        }
+        defer { defaults.removePersistentDomain(forName: suiteName) }
+
+        defaults.set(true, forKey: UpdateChannelSettings.includeNightlyBuildsKey)
+        let resolved = UpdateChannelSettings.resolvedFeedURLString(
+            infoFeedURL: "https://example.com/custom/appcast.xml",
+            defaults: defaults
+        )
+        XCTAssertEqual(resolved.url, UpdateChannelSettings.nightlyFeedURL)
+        XCTAssertTrue(resolved.isNightly)
+        XCTAssertFalse(resolved.usedFallback)
+    }
+}
+
 final class WorkspaceReorderTests: XCTestCase {
     @MainActor
     func testReorderWorkspaceMovesWorkspaceToRequestedIndex() {

cmuxTests/GhosttyConfigTests.swift

@@ -0,0 +1,142 @@
+import XCTest
+import AppKit
+
+#if canImport(cmux_DEV)
+@testable import cmux_DEV
+#elseif canImport(cmux)
+@testable import cmux
+#endif
+
+final class GhosttyConfigTests: XCTestCase {
+    private struct RGB: Equatable {
+        let red: Int
+        let green: Int
+        let blue: Int
+    }
+
+    func testResolveThemeNamePrefersLightEntryForPairedTheme() {
+        let resolved = GhosttyConfig.resolveThemeName(
+            from: "light:Builtin Solarized Light,dark:Builtin Solarized Dark",
+            preferredColorScheme: .light
+        )
+
+        XCTAssertEqual(resolved, "Builtin Solarized Light")
+    }
+
+    func testResolveThemeNamePrefersDarkEntryForPairedTheme() {
+        let resolved = GhosttyConfig.resolveThemeName(
+            from: "light:Builtin Solarized Light,dark:Builtin Solarized Dark",
+            preferredColorScheme: .dark
+        )
+
+        XCTAssertEqual(resolved, "Builtin Solarized Dark")
+    }
+
+    func testThemeNameCandidatesIncludeBuiltinAliasForms() {
+        let candidates = GhosttyConfig.themeNameCandidates(from: "Builtin Solarized Light")
+        XCTAssertEqual(candidates.first, "Builtin Solarized Light")
+        XCTAssertTrue(candidates.contains("Solarized Light"))
+        XCTAssertTrue(candidates.contains("iTerm2 Solarized Light"))
+    }
+
+    func testThemeNameCandidatesMapSolarizedDarkToITerm2Alias() {
+        let candidates = GhosttyConfig.themeNameCandidates(from: "Builtin Solarized Dark")
+        XCTAssertTrue(candidates.contains("Solarized Dark"))
+        XCTAssertTrue(candidates.contains("iTerm2 Solarized Dark"))
+    }
+
+    func testThemeSearchPathsIncludeXDGDataDirsThemes() {
+        let pathA = "/tmp/cmux-theme-a"
+        let pathB = "/tmp/cmux-theme-b"
+        let paths = GhosttyConfig.themeSearchPaths(
+            forThemeName: "Solarized Light",
+            environment: ["XDG_DATA_DIRS": "\(pathA):\(pathB)"],
+            bundleResourceURL: nil
+        )
+
+        XCTAssertTrue(paths.contains("\(pathA)/ghostty/themes/Solarized Light"))
+        XCTAssertTrue(paths.contains("\(pathB)/ghostty/themes/Solarized Light"))
+    }
+
+    func testLoadThemeResolvesPairedThemeValueByColorScheme() throws {
+        let root = FileManager.default.temporaryDirectory
+            .appendingPathComponent("cmux-ghostty-theme-pair-\(UUID().uuidString)")
+        let themesDir = root.appendingPathComponent("themes")
+        try FileManager.default.createDirectory(at: themesDir, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: root) }
+
+        try """
+        background = #fdf6e3
+        foreground = #657b83
+        """.write(
+            to: themesDir.appendingPathComponent("Light Theme"),
+            atomically: true,
+            encoding: .utf8
+        )
+
+        try """
+        background = #002b36
+        foreground = #93a1a1
+        """.write(
+            to: themesDir.appendingPathComponent("Dark Theme"),
+            atomically: true,
+            encoding: .utf8
+        )
+
+        var lightConfig = GhosttyConfig()
+        lightConfig.loadTheme(
+            "light:Light Theme,dark:Dark Theme",
+            environment: ["GHOSTTY_RESOURCES_DIR": root.path],
+            bundleResourceURL: nil,
+            preferredColorScheme: .light
+        )
+        XCTAssertEqual(rgb255(lightConfig.backgroundColor), RGB(red: 253, green: 246, blue: 227))
+
+        var darkConfig = GhosttyConfig()
+        darkConfig.loadTheme(
+            "light:Light Theme,dark:Dark Theme",
+            environment: ["GHOSTTY_RESOURCES_DIR": root.path],
+            bundleResourceURL: nil,
+            preferredColorScheme: .dark
+        )
+        XCTAssertEqual(rgb255(darkConfig.backgroundColor), RGB(red: 0, green: 43, blue: 54))
+    }
+
+    func testLoadThemeResolvesBuiltinAliasFromGhosttyResourcesDir() throws {
+        let root = FileManager.default.temporaryDirectory
+            .appendingPathComponent("cmux-ghostty-themes-\(UUID().uuidString)")
+        let themesDir = root.appendingPathComponent("themes")
+        try FileManager.default.createDirectory(at: themesDir, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: root) }
+
+        let themePath = themesDir.appendingPathComponent("Solarized Light")
+        let themeContents = """
+        background = #fdf6e3
+        foreground = #657b83
+        """
+        try themeContents.write(to: themePath, atomically: true, encoding: .utf8)
+
+        var config = GhosttyConfig()
+        config.loadTheme(
+            "Builtin Solarized Light",
+            environment: ["GHOSTTY_RESOURCES_DIR": root.path],
+            bundleResourceURL: nil
+        )
+
+        XCTAssertEqual(rgb255(config.backgroundColor), RGB(red: 253, green: 246, blue: 227))
+    }
+
+    private func rgb255(_ color: NSColor) -> RGB {
+        let srgb = color.usingColorSpace(.sRGB)!
+        var red: CGFloat = 0
+        var green: CGFloat = 0
+        var blue: CGFloat = 0
+        var alpha: CGFloat = 0
+        srgb.getRed(&red, green: &green, blue: &blue, alpha: &alpha)
+        return RGB(
+            red: Int(round(red * 255)),
+            green: Int(round(green * 255)),
+            blue: Int(round(blue * 255))
+        )
+    }
+}

vendor/bonsplit

@@ -1 +1 @@
-Subproject commit 748d9c0fe12edebd5448b946ce2c23d7549cd073
+Subproject commit ae234a227cb77cc4f34e28098a565e987ca23d87