Fix command modified keys. Add plan for splitscreen

Downterm/CommandNotch.xcodeproj/xcshareddata/xcschemes/CommandNotch.xcscheme

@@ -1,11 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "2620"
+   LastUpgradeVersion = "1600"
    version = "1.7">
    <BuildAction
       parallelizeBuildables = "YES"
       buildImplicitDependencies = "YES"
-      buildArchitectures = "Automatic">
+      runPostActionsOnFailure = "NO">
       <BuildActionEntries>
          <BuildActionEntry
             buildForTesting = "YES"
@@ -15,7 +15,7 @@
             buildForAnalyzing = "YES">
             <BuildableReference
                BuildableIdentifier = "primary"
-               BlueprintIdentifier = "1485207FA11756EC2DF4F08B"
+               BlueprintIdentifier = "D5585E5732CD067DF6EF0C69"
                BuildableName = "CommandNotch.app"
                BlueprintName = "CommandNotch"
                ReferencedContainer = "container:CommandNotch.xcodeproj">
@@ -28,7 +28,42 @@
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES"
-      shouldAutocreateTestPlan = "YES">
+      onlyGenerateCoverageForSpecifiedTargets = "NO">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "D5585E5732CD067DF6EF0C69"
+            BuildableName = "CommandNotch.app"
+            BlueprintName = "CommandNotch"
+            ReferencedContainer = "container:CommandNotch.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+      <Testables>
+         <TestableReference
+            skipped = "NO"
+            parallelizable = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "036FDAECD12C0A679DA1F5D6"
+               BuildableName = "CommandNotchTests.xctest"
+               BlueprintName = "CommandNotchTests"
+               ReferencedContainer = "container:CommandNotch.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+         <TestableReference
+            skipped = "NO"
+            parallelizable = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "1C8D00CBB29219BD347E9CC4"
+               BuildableName = "CommandNotchUITests.xctest"
+               BlueprintName = "CommandNotchUITests"
+               ReferencedContainer = "container:CommandNotch.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+      </Testables>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Debug"
@@ -44,12 +79,14 @@
          runnableDebuggingMode = "0">
          <BuildableReference
             BuildableIdentifier = "primary"
-            BlueprintIdentifier = "1485207FA11756EC2DF4F08B"
+            BlueprintIdentifier = "D5585E5732CD067DF6EF0C69"
             BuildableName = "CommandNotch.app"
             BlueprintName = "CommandNotch"
             ReferencedContainer = "container:CommandNotch.xcodeproj">
          </BuildableReference>
       </BuildableProductRunnable>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </LaunchAction>
    <ProfileAction
       buildConfiguration = "Release"
@@ -61,12 +98,14 @@
          runnableDebuggingMode = "0">
          <BuildableReference
             BuildableIdentifier = "primary"
-            BlueprintIdentifier = "1485207FA11756EC2DF4F08B"
+            BlueprintIdentifier = "D5585E5732CD067DF6EF0C69"
             BuildableName = "CommandNotch.app"
             BlueprintName = "CommandNotch"
             ReferencedContainer = "container:CommandNotch.xcodeproj">
          </BuildableReference>
       </BuildableProductRunnable>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </ProfileAction>
    <AnalyzeAction
       buildConfiguration = "Debug">

Downterm/CommandNotch.xcodeproj/xcshareddata/xcschemes/Release-CommandNotch.xcscheme

@@ -1,11 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "2620"
+   LastUpgradeVersion = "1600"
    version = "1.7">
    <BuildAction
       parallelizeBuildables = "YES"
       buildImplicitDependencies = "YES"
-      buildArchitectures = "Automatic">
+      runPostActionsOnFailure = "NO">
       <BuildActionEntries>
          <BuildActionEntry
             buildForTesting = "YES"
@@ -15,7 +15,7 @@
             buildForAnalyzing = "YES">
             <BuildableReference
                BuildableIdentifier = "primary"
-               BlueprintIdentifier = "1485207FA11756EC2DF4F08B"
+               BlueprintIdentifier = "D5585E5732CD067DF6EF0C69"
                BuildableName = "CommandNotch.app"
                BlueprintName = "CommandNotch"
                ReferencedContainer = "container:CommandNotch.xcodeproj">
@@ -28,13 +28,48 @@
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES"
-      shouldAutocreateTestPlan = "YES">
+      onlyGenerateCoverageForSpecifiedTargets = "NO">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "D5585E5732CD067DF6EF0C69"
+            BuildableName = "CommandNotch.app"
+            BlueprintName = "CommandNotch"
+            ReferencedContainer = "container:CommandNotch.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+      <Testables>
+         <TestableReference
+            skipped = "NO"
+            parallelizable = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "036FDAECD12C0A679DA1F5D6"
+               BuildableName = "CommandNotchTests.xctest"
+               BlueprintName = "CommandNotchTests"
+               ReferencedContainer = "container:CommandNotch.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+         <TestableReference
+            skipped = "NO"
+            parallelizable = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "1C8D00CBB29219BD347E9CC4"
+               BuildableName = "CommandNotchUITests.xctest"
+               BlueprintName = "CommandNotchUITests"
+               ReferencedContainer = "container:CommandNotch.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+      </Testables>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Release"
-      selectedDebuggerIdentifier = ""
-      selectedLauncherIdentifier = "Xcode.IDEFoundation.Launcher.PosixSpawn"
-      launchStyle = "1"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
       useCustomWorkingDirectory = "NO"
       ignoresPersistentStateOnLaunch = "NO"
       debugDocumentVersioning = "YES"
@@ -44,12 +79,14 @@
          runnableDebuggingMode = "0">
          <BuildableReference
             BuildableIdentifier = "primary"
-            BlueprintIdentifier = "1485207FA11756EC2DF4F08B"
+            BlueprintIdentifier = "D5585E5732CD067DF6EF0C69"
             BuildableName = "CommandNotch.app"
             BlueprintName = "CommandNotch"
             ReferencedContainer = "container:CommandNotch.xcodeproj">
          </BuildableReference>
       </BuildableProductRunnable>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </LaunchAction>
    <ProfileAction
       buildConfiguration = "Release"
@@ -61,12 +98,14 @@
          runnableDebuggingMode = "0">
          <BuildableReference
             BuildableIdentifier = "primary"
-            BlueprintIdentifier = "1485207FA11756EC2DF4F08B"
+            BlueprintIdentifier = "D5585E5732CD067DF6EF0C69"
             BuildableName = "CommandNotch.app"
             BlueprintName = "CommandNotch"
             ReferencedContainer = "container:CommandNotch.xcodeproj">
          </BuildableReference>
       </BuildableProductRunnable>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </ProfileAction>
    <AnalyzeAction
       buildConfiguration = "Debug">

Downterm/CommandNotch/Components/HotkeyRecorderView.swift

@@ -76,9 +76,7 @@ struct HotkeyRecorderField: NSViewRepresentable {
     }
 
     func updateNSView(_ nsView: HotkeyNSView, context: Context) {
-        nsView.currentLabel = binding.displayString
-        nsView.showRecording = isRecording
-        nsView.needsDisplay = true
+        nsView.update(currentLabel: binding.displayString, isRecording: isRecording)
     }
 }
 
@@ -99,9 +97,7 @@ struct OptionalHotkeyRecorderField: NSViewRepresentable {
     }
 
     func updateNSView(_ nsView: HotkeyNSView, context: Context) {
-        nsView.currentLabel = binding?.displayString ?? "Not set"
-        nsView.showRecording = isRecording
-        nsView.needsDisplay = true
+        nsView.update(currentLabel: binding?.displayString ?? "Not set", isRecording: isRecording)
     }
 }
 
@@ -183,6 +179,12 @@ class HotkeyNSView: NSView {
         updateLabelAppearance()
     }
 
+    func update(currentLabel: String, isRecording: Bool) {
+        self.currentLabel = currentLabel
+        showRecording = isRecording
+        updateLabelAppearance()
+    }
+
     private func updateLabelAppearance() {
         label.stringValue = showRecording ? "Press keys..." : currentLabel
         label.textColor = showRecording ? .controlAccentColor : .labelColor

Downterm/CommandNotch/Components/TabBar.swift

@@ -9,17 +9,6 @@ struct TabBar: View {
 
     var body: some View {
         HStack(spacing: 0) {
-            ScrollView(.horizontal, showsIndicators: false) {
-                HStack(spacing: 2) {
-                    ForEach(Array(workspace.tabs.enumerated()), id: \.element.id) { index, tab in
-                        tabButton(for: tab, at: index)
-                    }
-                }
-                .padding(.horizontal, 4)
-            }
-
-            Spacer()
-
             Button {
                 workspace.newTab()
             } label: {
@@ -31,6 +20,15 @@ struct TabBar: View {
             .accessibilityIdentifier("notch.new-tab")
             .buttonStyle(.plain)
             .padding(.horizontal, 8)
+
+            ScrollView(.horizontal, showsIndicators: false) {
+                HStack(spacing: 2) {
+                    ForEach(Array(workspace.tabs.enumerated()), id: \.element.id) { index, tab in
+                        tabButton(for: tab, at: index)
+                    }
+                }
+                .padding(.horizontal, 4)
+            }
         }
         .frame(height: 28)
         .background(.black)

Downterm/CommandNotch/Components/TerminalCommandArrowBehavior.swift

@@ -0,0 +1,31 @@
+import AppKit
+import Carbon.HIToolbox
+import SwiftTerm
+
+enum TerminalCommandArrowBehavior {
+    private static let relevantModifiers: NSEvent.ModifierFlags = [.command, .control, .option, .shift]
+    private static let lineKill: [UInt8] = [0x15]
+    private static let clearScreen: [UInt8] = [0x0c]
+
+    static func sequence(
+        for modifierFlags: NSEvent.ModifierFlags,
+        keyCode: UInt16,
+        applicationCursor: Bool
+    ) -> [UInt8]? {
+        let flags = modifierFlags.intersection(relevantModifiers)
+        guard flags == [.command] else { return nil }
+
+        switch Int(keyCode) {
+        case kVK_LeftArrow:
+            return applicationCursor ? EscapeSequences.moveHomeApp : EscapeSequences.moveHomeNormal
+        case kVK_RightArrow:
+            return applicationCursor ? EscapeSequences.moveEndApp : EscapeSequences.moveEndNormal
+        case kVK_Delete:
+            return lineKill
+        case kVK_ANSI_L:
+            return clearScreen
+        default:
+            return nil
+        }
+    }
+}

Downterm/CommandNotch/Managers/HotkeyManager.swift

@@ -5,7 +5,7 @@ import Combine
 /// Manages global and local hotkeys.
 ///
 /// The toggle hotkey uses Carbon's `RegisterEventHotKey` which works
-/// system-wide without Accessibility permission. Tab-level hotkeys
+/// system-wide without Accessibility permission. Notch-scoped hotkeys
 /// use a local `NSEvent` monitor (only fires when our app is active).
 @MainActor
 class HotkeyManager {
@@ -19,21 +19,29 @@ class HotkeyManager {
     var onCloseTab: (() -> Void)?
     var onNextTab: (() -> Void)?
     var onPreviousTab: (() -> Void)?
+    var onNextWorkspace: (() -> Void)?
+    var onPreviousWorkspace: (() -> Void)?
     var onDetachTab: (() -> Void)?
     var onApplySizePreset: ((TerminalSizePreset) -> Void)?
     var onSwitchToTab: ((Int) -> Void)?
+    var onSwitchToWorkspace: ((WorkspaceID) -> Void)?
 
-    /// Tab-level hotkeys only fire when the notch is open.
+    /// Notch-scoped hotkeys only fire when the notch is open.
     var isNotchOpen: Bool = false
 
     private var hotKeyRef: EventHotKeyRef?
     private var eventHandlerRef: EventHandlerRef?
     private var localMonitor: Any?
     private let settingsProvider: TerminalSessionConfigurationProviding
+    private let workspaceRegistry: WorkspaceRegistry
     private var settingsCancellable: AnyCancellable?
 
-    init(settingsProvider: TerminalSessionConfigurationProviding? = nil) {
+    init(
+        settingsProvider: TerminalSessionConfigurationProviding? = nil,
+        workspaceRegistry: WorkspaceRegistry? = nil
+    ) {
         self.settingsProvider = settingsProvider ?? AppSettingsController.shared
+        self.workspaceRegistry = workspaceRegistry ?? WorkspaceRegistry.shared
     }
 
     // MARK: - Resolved bindings from typed runtime settings
@@ -53,6 +61,12 @@ class HotkeyManager {
     private var prevTabBinding: HotkeyBinding {
         settingsProvider.hotkeySettings.previousTab
     }
+    private var nextWorkspaceBinding: HotkeyBinding {
+        settingsProvider.hotkeySettings.nextWorkspace
+    }
+    private var previousWorkspaceBinding: HotkeyBinding {
+        settingsProvider.hotkeySettings.previousWorkspace
+    }
     private var detachBinding: HotkeyBinding {
         settingsProvider.hotkeySettings.detachTab
     }
@@ -173,7 +187,7 @@ class HotkeyManager {
             }
     }
 
-    // MARK: - Local monitor (tab-level hotkeys, only when our app is active)
+    // MARK: - Local monitor (notch-level hotkeys, only when our app is active)
 
     private func installLocalMonitor() {
         localMonitor = NSEvent.addLocalMonitorForEvents(matching: .keyDown) { [weak self] event in
@@ -189,9 +203,9 @@ class HotkeyManager {
         }
     }
 
-    /// Handles tab-level hotkeys. Returns true if the event was consumed.
+    /// Handles notch-scoped hotkeys. Returns true if the event was consumed.
     private func handleLocalKeyEvent(_ event: NSEvent) -> Bool {
-        // Tab hotkeys only when the notch is open and focused
+        // Local shortcuts only fire when the notch is open and focused.
         guard isNotchOpen else { return false }
 
         if newTabBinding.matches(event) {
@@ -210,10 +224,25 @@ class HotkeyManager {
             onPreviousTab?()
             return true
         }
+        if nextWorkspaceBinding.matches(event) {
+            onNextWorkspace?()
+            return true
+        }
+        if previousWorkspaceBinding.matches(event) {
+            onPreviousWorkspace?()
+            return true
+        }
         if detachBinding.matches(event) {
             onDetachTab?()
             return true
         }
+        for summary in workspaceRegistry.workspaceSummaries {
+            guard let binding = summary.hotkey else { continue }
+            if binding.matches(event) {
+                onSwitchToWorkspace?(summary.id)
+                return true
+            }
+        }
         for preset in sizePresets {
             guard let binding = preset.hotkey else { continue }
             if binding.matches(event) {

Downterm/CommandNotch/Managers/ScreenManager.swift

@@ -9,6 +9,7 @@ final class ScreenManager: ObservableObject {
     static let shared = ScreenManager()
 
     private let screenRegistry = ScreenRegistry.shared
+    private let workspaceRegistry = WorkspaceRegistry.shared
     private let windowCoordinator = WindowCoordinator()
     private lazy var orchestrator = NotchOrchestrator(screenRegistry: screenRegistry, host: self)
 
@@ -55,6 +56,12 @@ final class ScreenManager: ObservableObject {
         hotkeyManager.onPreviousTab = { [weak self] in
             MainActor.assumeIsolated { self?.activeWorkspace().previousTab() }
         }
+        hotkeyManager.onNextWorkspace = { [weak self] in
+            MainActor.assumeIsolated { self?.switchWorkspace(offset: 1) }
+        }
+        hotkeyManager.onPreviousWorkspace = { [weak self] in
+            MainActor.assumeIsolated { self?.switchWorkspace(offset: -1) }
+        }
         hotkeyManager.onDetachTab = { [weak self] in
             MainActor.assumeIsolated { self?.detachActiveTab() }
         }
@@ -64,6 +71,9 @@ final class ScreenManager: ObservableObject {
         hotkeyManager.onSwitchToTab = { [weak self] index in
             MainActor.assumeIsolated { self?.activeWorkspace().switchToTab(at: index) }
         }
+        hotkeyManager.onSwitchToWorkspace = { [weak self] workspaceID in
+            MainActor.assumeIsolated { self?.switchActiveScreen(to: workspaceID) }
+        }
 
         hotkeyManager.start()
     }
@@ -92,6 +102,33 @@ final class ScreenManager: ObservableObject {
         }
     }
 
+    private func switchWorkspace(offset: Int) {
+        guard let screenID = screenRegistry.activeScreenID() else { return }
+        let currentWorkspaceID = screenRegistry.screenContext(for: screenID)?.workspaceID ?? workspaceRegistry.defaultWorkspaceID
+        let nextWorkspaceID = offset >= 0
+            ? workspaceRegistry.nextWorkspaceID(after: currentWorkspaceID)
+            : workspaceRegistry.previousWorkspaceID(before: currentWorkspaceID)
+
+        guard let nextWorkspaceID else { return }
+        switchScreen(screenID, to: nextWorkspaceID)
+    }
+
+    private func switchActiveScreen(to workspaceID: WorkspaceID) {
+        guard let screenID = screenRegistry.activeScreenID() else { return }
+        switchScreen(screenID, to: workspaceID)
+    }
+
+    private func switchScreen(_ screenID: ScreenID, to workspaceID: WorkspaceID) {
+        screenRegistry.assignWorkspace(workspaceID, to: screenID)
+
+        guard let context = screenRegistry.screenContext(for: screenID),
+              context.notchState == .open else {
+            return
+        }
+
+        orchestrator.open(screenID: screenID)
+    }
+
     func applySizePreset(_ preset: TerminalSizePreset) {
         guard let context = screenRegistry.allScreens().first(where: { $0.notchState == .open }) else {
             AppSettingsController.shared.update {

Downterm/CommandNotch/Models/AppSettings.swift

@@ -56,6 +56,8 @@ struct AppSettings: Equatable, Codable {
             closeTab: .cmdW,
             nextTab: .cmdShiftRB,
             previousTab: .cmdShiftLB,
+            nextWorkspace: .cmdShiftDown,
+            previousWorkspace: .cmdShiftUp,
             detachTab: .cmdD
         )
     )
@@ -121,6 +123,8 @@ extension AppSettings {
         var closeTab: HotkeyBinding
         var nextTab: HotkeyBinding
         var previousTab: HotkeyBinding
+        var nextWorkspace: HotkeyBinding
+        var previousWorkspace: HotkeyBinding
         var detachTab: HotkeyBinding
     }
 }

Downterm/CommandNotch/Models/AppSettingsStore.swift

@@ -60,6 +60,8 @@ struct UserDefaultsAppSettingsStore: AppSettingsStoreType {
                 closeTab: hotkey(NotchSettings.Keys.hotkeyCloseTab, default: .cmdW),
                 nextTab: hotkey(NotchSettings.Keys.hotkeyNextTab, default: .cmdShiftRB),
                 previousTab: hotkey(NotchSettings.Keys.hotkeyPreviousTab, default: .cmdShiftLB),
+                nextWorkspace: hotkey(NotchSettings.Keys.hotkeyNextWorkspace, default: .cmdShiftDown),
+                previousWorkspace: hotkey(NotchSettings.Keys.hotkeyPreviousWorkspace, default: .cmdShiftUp),
                 detachTab: hotkey(NotchSettings.Keys.hotkeyDetachTab, default: .cmdD)
             )
         )
@@ -106,6 +108,8 @@ struct UserDefaultsAppSettingsStore: AppSettingsStoreType {
         defaults.set(settings.hotkeys.closeTab.toJSON(), forKey: NotchSettings.Keys.hotkeyCloseTab)
         defaults.set(settings.hotkeys.nextTab.toJSON(), forKey: NotchSettings.Keys.hotkeyNextTab)
         defaults.set(settings.hotkeys.previousTab.toJSON(), forKey: NotchSettings.Keys.hotkeyPreviousTab)
+        defaults.set(settings.hotkeys.nextWorkspace.toJSON(), forKey: NotchSettings.Keys.hotkeyNextWorkspace)
+        defaults.set(settings.hotkeys.previousWorkspace.toJSON(), forKey: NotchSettings.Keys.hotkeyPreviousWorkspace)
         defaults.set(settings.hotkeys.detachTab.toJSON(), forKey: NotchSettings.Keys.hotkeyDetachTab)
     }
 

Downterm/CommandNotch/Models/HotkeyBinding.swift

@@ -88,6 +88,8 @@ struct HotkeyBinding: Codable, Equatable, Hashable {
     static let cmdW         = HotkeyBinding(modifiers: NSEvent.ModifierFlags.command.rawValue, keyCode: 13)
     static let cmdShiftRB   = HotkeyBinding(modifiers: NSEvent.ModifierFlags([.command, .shift]).rawValue, keyCode: 30)  // ]
     static let cmdShiftLB   = HotkeyBinding(modifiers: NSEvent.ModifierFlags([.command, .shift]).rawValue, keyCode: 33)  // [
+    static let cmdShiftDown = HotkeyBinding(modifiers: NSEvent.ModifierFlags([.command, .shift]).rawValue, keyCode: 125)
+    static let cmdShiftUp   = HotkeyBinding(modifiers: NSEvent.ModifierFlags([.command, .shift]).rawValue, keyCode: 126)
     static let cmdD         = HotkeyBinding(modifiers: NSEvent.ModifierFlags.command.rawValue, keyCode: 2)
 
     static func cmdShiftDigit(_ digit: Int) -> HotkeyBinding? {

Downterm/CommandNotch/Models/NotchSettings.swift

@@ -57,6 +57,8 @@ enum NotchSettings {
         static let hotkeyCloseTab        = "hotkey_closeTab"
         static let hotkeyNextTab         = "hotkey_nextTab"
         static let hotkeyPreviousTab     = "hotkey_previousTab"
+        static let hotkeyNextWorkspace   = "hotkey_nextWorkspace"
+        static let hotkeyPreviousWorkspace = "hotkey_previousWorkspace"
         static let hotkeyDetachTab       = "hotkey_detachTab"
     }
 
@@ -104,6 +106,8 @@ enum NotchSettings {
         static let hotkeyCloseTab: String    = HotkeyBinding.cmdW.toJSON()
         static let hotkeyNextTab: String     = HotkeyBinding.cmdShiftRB.toJSON()
         static let hotkeyPreviousTab: String = HotkeyBinding.cmdShiftLB.toJSON()
+        static let hotkeyNextWorkspace: String = HotkeyBinding.cmdShiftDown.toJSON()
+        static let hotkeyPreviousWorkspace: String = HotkeyBinding.cmdShiftUp.toJSON()
         static let hotkeyDetachTab: String   = HotkeyBinding.cmdD.toJSON()
     }
 
@@ -151,6 +155,8 @@ enum NotchSettings {
             Keys.hotkeyCloseTab:        Defaults.hotkeyCloseTab,
             Keys.hotkeyNextTab:         Defaults.hotkeyNextTab,
             Keys.hotkeyPreviousTab:     Defaults.hotkeyPreviousTab,
+            Keys.hotkeyNextWorkspace:   Defaults.hotkeyNextWorkspace,
+            Keys.hotkeyPreviousWorkspace: Defaults.hotkeyPreviousWorkspace,
             Keys.hotkeyDetachTab:       Defaults.hotkeyDetachTab,
         ])
     }

Downterm/CommandNotch/Models/TerminalSession.swift

@@ -9,6 +9,7 @@ class TerminalSession: NSObject, ObservableObject, LocalProcessDelegate, @precon
     let id = UUID()
     let terminalView: TerminalView
     private var process: LocalProcess?
+    private var keyEventMonitor: Any?
     private let backgroundColor = NSColor.black
     private let configuredShellPath: String
 
@@ -26,10 +27,17 @@ class TerminalSession: NSObject, ObservableObject, LocalProcessDelegate, @precon
         let font = NSFont.monospacedSystemFont(ofSize: fontSize, weight: .regular)
         terminalView.font = font
         applyTheme(theme)
+        installCommandArrowMonitor()
 
         startShell()
     }
 
+    deinit {
+        if let keyEventMonitor {
+            NSEvent.removeMonitor(keyEventMonitor)
+        }
+    }
+
     // MARK: - Shell management
 
     private func startShell() {
@@ -58,6 +66,26 @@ class TerminalSession: NSObject, ObservableObject, LocalProcessDelegate, @precon
         return ProcessInfo.processInfo.environment["SHELL"] ?? "/bin/zsh"
     }
 
+    private func installCommandArrowMonitor() {
+        keyEventMonitor = NSEvent.addLocalMonitorForEvents(matching: .keyDown) { [weak self] event in
+            guard let self else { return event }
+            guard let window = self.terminalView.window else { return event }
+            guard event.window === window else { return event }
+            guard window.firstResponder === self.terminalView else { return event }
+
+            guard let sequence = TerminalCommandArrowBehavior.sequence(
+                for: event.modifierFlags,
+                keyCode: event.keyCode,
+                applicationCursor: self.terminalView.getTerminal().applicationCursor
+            ) else {
+                return event
+            }
+
+            self.terminalView.send(data: sequence[...])
+            return nil
+        }
+    }
+
     func updateFontSize(_ size: CGFloat) {
         terminalView.font = NSFont.monospacedSystemFont(ofSize: size, weight: .regular)
     }

Downterm/CommandNotch/Models/WorkspaceController.swift

@@ -18,6 +18,7 @@ final class WorkspaceController: ObservableObject {
     let createdAt: Date
 
     @Published private(set) var name: String
+    @Published private(set) var hotkey: HotkeyBinding?
     @Published private(set) var tabs: [TerminalSession] = []
     @Published private(set) var activeTabIndex: Int = 0
 
@@ -34,6 +35,7 @@ final class WorkspaceController: ObservableObject {
         self.id = summary.id
         self.name = summary.name
         self.createdAt = summary.createdAt
+        self.hotkey = summary.hotkey
         self.sessionFactory = sessionFactory
         self.settingsProvider = settingsProvider
 
@@ -51,7 +53,7 @@ final class WorkspaceController: ObservableObject {
     }
 
     var summary: WorkspaceSummary {
-        WorkspaceSummary(id: id, name: name, createdAt: createdAt)
+        WorkspaceSummary(id: id, name: name, createdAt: createdAt, hotkey: hotkey)
     }
 
     var state: WorkspaceState {
@@ -78,6 +80,11 @@ final class WorkspaceController: ObservableObject {
         name = trimmed
     }
 
+    func updateHotkey(_ updatedHotkey: HotkeyBinding?) {
+        guard hotkey != updatedHotkey else { return }
+        hotkey = updatedHotkey
+    }
+
     func newTab() {
         let config = settingsProvider.terminalSessionConfiguration
         let session = sessionFactory.makeSession(

Downterm/CommandNotch/Models/WorkspaceRegistry.swift

@@ -104,6 +104,37 @@ final class WorkspaceRegistry: ObservableObject {
         persistWorkspaceSummaries()
     }
 
+    func updateWorkspaceHotkey(id: WorkspaceID, to hotkey: HotkeyBinding?) {
+        guard let index = workspaceSummaries.firstIndex(where: { $0.id == id }) else { return }
+        guard workspaceSummaries[index].hotkey != hotkey else { return }
+
+        workspaceSummaries[index].hotkey = hotkey
+        controllers[id]?.updateHotkey(hotkey)
+        persistWorkspaceSummaries()
+    }
+
+    func nextWorkspaceID(after id: WorkspaceID) -> WorkspaceID? {
+        guard !workspaceSummaries.isEmpty else { return nil }
+        guard let index = workspaceSummaries.firstIndex(where: { $0.id == id }) else {
+            return workspaceSummaries.first?.id
+        }
+
+        let nextIndex = workspaceSummaries.index(after: index)
+        return workspaceSummaries[nextIndex == workspaceSummaries.endIndex ? workspaceSummaries.startIndex : nextIndex].id
+    }
+
+    func previousWorkspaceID(before id: WorkspaceID) -> WorkspaceID? {
+        guard !workspaceSummaries.isEmpty else { return nil }
+        guard let index = workspaceSummaries.firstIndex(where: { $0.id == id }) else {
+            return workspaceSummaries.last?.id
+        }
+
+        let previousIndex = index == workspaceSummaries.startIndex
+            ? workspaceSummaries.index(before: workspaceSummaries.endIndex)
+            : workspaceSummaries.index(before: index)
+        return workspaceSummaries[previousIndex].id
+    }
+
     @discardableResult
     func deleteWorkspace(id: WorkspaceID) -> Bool {
         guard canDeleteWorkspace(id: id) else { return false }

Downterm/CommandNotch/Models/WorkspaceSummary.swift

@@ -6,11 +6,13 @@ struct WorkspaceSummary: Identifiable, Equatable, Codable {
     var id: WorkspaceID
     var name: String
     var createdAt: Date
+    var hotkey: HotkeyBinding?
 
-    init(id: WorkspaceID = UUID(), name: String, createdAt: Date = Date()) {
+    init(id: WorkspaceID = UUID(), name: String, createdAt: Date = Date(), hotkey: HotkeyBinding? = nil) {
         self.id = id
         self.name = name
         self.createdAt = createdAt
+        self.hotkey = hotkey
     }
 }
 

Downterm/CommandNotch/Views/HotkeySettingsView.swift

@@ -17,8 +17,13 @@ struct HotkeySettingsView: View {
                 HotkeyRecorderView(label: "Detach tab", binding: settingsController.binding(\.hotkeys.detachTab))
             }
 
+            Section("Workspaces (active when notch is open)") {
+                HotkeyRecorderView(label: "Next workspace", binding: settingsController.binding(\.hotkeys.nextWorkspace))
+                HotkeyRecorderView(label: "Previous workspace", binding: settingsController.binding(\.hotkeys.previousWorkspace))
+            }
+
             Section {
-                Text("⌘1–9 always switch to tab by number. Size preset hotkeys are configured in Terminal > Size Presets.")
+                Text("⌘1–9 always switch to tab by number. Size preset hotkeys are configured in Terminal > Size Presets. Per-workspace jump hotkeys are configured in Workspaces.")
                     .font(.caption)
                     .foregroundStyle(.secondary)
             }

Downterm/CommandNotch/Views/TerminalSettingsView.swift

@@ -2,21 +2,7 @@ import SwiftUI
 
 struct TerminalSettingsView: View {
     @ObservedObject private var settingsController = AppSettingsController.shared
-
-    private var sizePresetsBinding: Binding<[TerminalSizePreset]> {
-        Binding(
-            get: {
-                TerminalSizePresetStore.decodePresets(
-                    from: settingsController.settings.terminal.sizePresetsJSON
-                ) ?? TerminalSizePresetStore.loadDefaults()
-            },
-            set: { newValue in
-                settingsController.update {
-                    $0.terminal.sizePresetsJSON = TerminalSizePresetStore.encodePresets(newValue)
-                }
-            }
-        )
-    }
+    @State private var sizePresets: [TerminalSizePreset] = []
 
     var body: some View {
         Form {
@@ -55,7 +41,7 @@ struct TerminalSettingsView: View {
             }
 
             Section("Size Presets") {
-                ForEach(sizePresetsBinding) { $preset in
+                ForEach($sizePresets) { $preset in
                     TerminalSizePresetEditor(
                         preset: $preset,
                         currentOpenWidth: settingsController.settings.display.openWidth,
@@ -67,20 +53,18 @@ struct TerminalSettingsView: View {
 
                 HStack {
                     Button("Add Preset") {
-                        var presets = sizePresetsBinding.wrappedValue
-                        presets.append(
+                        sizePresets.append(
                             TerminalSizePreset(
-                                name: "Preset \(presets.count + 1)",
+                                name: "Preset \(sizePresets.count + 1)",
                                 width: settingsController.settings.display.openWidth,
                                 height: settingsController.settings.display.openHeight,
-                                hotkey: TerminalSizePresetStore.suggestedHotkey(for: presets)
+                                hotkey: TerminalSizePresetStore.suggestedHotkey(for: sizePresets)
                             )
                         )
-                        sizePresetsBinding.wrappedValue = presets
                     }
 
                     Button("Reset Presets") {
-                        sizePresetsBinding.wrappedValue = TerminalSizePresetStore.loadDefaults()
+                        sizePresets = TerminalSizePresetStore.loadDefaults()
                     }
                 }
 
@@ -90,10 +74,24 @@ struct TerminalSettingsView: View {
             }
         }
         .formStyle(.grouped)
+        .onAppear {
+            synchronizePresetsFromSettings()
+        }
+        .onChange(of: settingsController.settings.terminal.sizePresetsJSON) { _, _ in
+            synchronizePresetsFromSettings()
+        }
+        .onChange(of: sizePresets) { _, newValue in
+            let encoded = TerminalSizePresetStore.encodePresets(newValue)
+            guard encoded != settingsController.settings.terminal.sizePresetsJSON else { return }
+
+            settingsController.update {
+                $0.terminal.sizePresetsJSON = encoded
+            }
+        }
     }
 
     private func deletePreset(id: UUID) {
-        sizePresetsBinding.wrappedValue.removeAll { $0.id == id }
+        sizePresets.removeAll { $0.id == id }
     }
 
     private func applyPreset(_ preset: TerminalSizePreset) {
@@ -103,6 +101,15 @@ struct TerminalSettingsView: View {
         }
         ScreenManager.shared.applySizePreset(preset)
     }
+
+    private func synchronizePresetsFromSettings() {
+        let decoded = TerminalSizePresetStore.decodePresets(
+            from: settingsController.settings.terminal.sizePresetsJSON
+        ) ?? TerminalSizePresetStore.loadDefaults()
+
+        guard decoded != sizePresets else { return }
+        sizePresets = decoded
+    }
 }
 
 private struct TerminalSizePresetEditor: View {

Downterm/CommandNotch/Views/WorkspacesSettingsView.swift

@@ -75,6 +75,11 @@ struct WorkspacesSettingsView: View {
                                 renameSelectedWorkspace()
                             }
 
+                        OptionalHotkeyRecorderView(
+                            label: "Jump Hotkey",
+                            binding: workspaceHotkeyBinding(for: summary.id)
+                        )
+
                         HStack {
                             Button("Save Name") {
                                 renameSelectedWorkspace()
@@ -86,6 +91,10 @@ struct WorkspacesSettingsView: View {
                             }
                             .accessibilityIdentifier("settings.workspaces.new")
                         }
+
+                        Text("Workspace jump hotkeys are active when the notch is open and switch the current screen to this workspace.")
+                            .font(.caption)
+                            .foregroundStyle(.secondary)
                     }
 
                     Section("Usage") {
@@ -256,6 +265,17 @@ struct WorkspacesSettingsView: View {
         renameDraft = workspaceRegistry.summary(for: workspaceID)?.name ?? ""
     }
 
+    private func workspaceHotkeyBinding(for workspaceID: WorkspaceID) -> Binding<HotkeyBinding?> {
+        Binding(
+            get: {
+                workspaceRegistry.summary(for: workspaceID)?.hotkey
+            },
+            set: { newValue in
+                workspaceRegistry.updateWorkspaceHotkey(id: workspaceID, to: newValue)
+            }
+        )
+    }
+
     private func deleteSelectedWorkspace() {
         guard let effectiveSelectedWorkspaceID,
               let fallbackWorkspaceID = screenRegistry.deleteWorkspace(

Downterm/CommandNotchTests/TerminalCommandArrowBehaviorTests.swift

@@ -0,0 +1,57 @@
+import AppKit
+import Carbon.HIToolbox
+import XCTest
+import SwiftTerm
+@testable import CommandNotch
+
+final class TerminalCommandArrowBehaviorTests: XCTestCase {
+    func testCommandLeftUsesHomeSequence() {
+        let sequence = TerminalCommandArrowBehavior.sequence(
+            for: [.command],
+            keyCode: UInt16(kVK_LeftArrow),
+            applicationCursor: false
+        )
+
+        XCTAssertEqual(sequence, EscapeSequences.moveHomeNormal)
+    }
+
+    func testCommandRightUsesApplicationEndSequence() {
+        let sequence = TerminalCommandArrowBehavior.sequence(
+            for: [.command],
+            keyCode: UInt16(kVK_RightArrow),
+            applicationCursor: true
+        )
+
+        XCTAssertEqual(sequence, EscapeSequences.moveEndApp)
+    }
+
+    func testOptionLeftKeepsSwiftTermWordNavigationPath() {
+        let sequence = TerminalCommandArrowBehavior.sequence(
+            for: [.option],
+            keyCode: UInt16(kVK_LeftArrow),
+            applicationCursor: false
+        )
+
+        XCTAssertNil(sequence)
+    }
+
+    func testCommandDeleteUsesLineKillSequence() {
+        let sequence = TerminalCommandArrowBehavior.sequence(
+            for: [.command],
+            keyCode: UInt16(kVK_Delete),
+            applicationCursor: false
+        )
+
+        XCTAssertEqual(sequence, [0x15])
+    }
+
+    func testCommandLUsesClearScreenSequence() {
+        let sequence = TerminalCommandArrowBehavior.sequence(
+            for: [.command],
+            keyCode: UInt16(kVK_ANSI_L),
+            applicationCursor: false
+        )
+
+        XCTAssertEqual(sequence, [0x0c])
+    }
+}

Downterm/CommandNotchTests/WorkspaceRegistryTests.swift

@@ -74,6 +74,30 @@ final class WorkspaceRegistryTests: XCTestCase {
         XCTAssertEqual(store.savedSummaries.map(\.name), ["Main"])
     }
 
+    func testUpdateWorkspaceHotkeyPersistsAndUpdatesSummary() {
+        let store = InMemoryWorkspaceStore()
+        let registry = makeRegistry(store: store)
+        let docsID = registry.createWorkspace(named: "Docs")
+        let hotkey = HotkeyBinding.cmdShiftDigit(4)
+
+        registry.updateWorkspaceHotkey(id: docsID, to: hotkey)
+
+        XCTAssertEqual(registry.summary(for: docsID)?.hotkey, hotkey)
+        XCTAssertEqual(store.savedSummaries.last?.hotkey, hotkey)
+    }
+
+    func testNextAndPreviousWorkspaceWrapAroundRegistryOrder() {
+        let registry = makeRegistry()
+        let mainID = registry.defaultWorkspaceID
+        let docsID = registry.createWorkspace(named: "Docs")
+        let reviewID = registry.createWorkspace(named: "Review")
+
+        XCTAssertEqual(registry.nextWorkspaceID(after: mainID), docsID)
+        XCTAssertEqual(registry.nextWorkspaceID(after: reviewID), mainID)
+        XCTAssertEqual(registry.previousWorkspaceID(before: mainID), reviewID)
+        XCTAssertEqual(registry.previousWorkspaceID(before: docsID), mainID)
+    }
+
     private func makeRegistry(
         initialWorkspaces: [WorkspaceSummary]? = [],
         store: (any WorkspaceStoreType)? = nil

Downterm/CommandNotchTests/WorkspaceStoreTests.swift

@@ -9,7 +9,11 @@ final class WorkspaceStoreTests: XCTestCase {
 
         let store = UserDefaultsWorkspaceStore(defaults: defaults)
         let summaries = [
-            WorkspaceSummary(id: UUID(uuidString: "11111111-1111-1111-1111-111111111111")!, name: "Main"),
+            WorkspaceSummary(
+                id: UUID(uuidString: "11111111-1111-1111-1111-111111111111")!,
+                name: "Main",
+                hotkey: HotkeyBinding.cmdShiftDigit(4)
+            ),
             WorkspaceSummary(id: UUID(uuidString: "22222222-2222-2222-2222-222222222222")!, name: "Docs")
         ]
 

Downterm/project.yml

@@ -14,6 +14,45 @@ packages:
   SwiftTerm:
     url: https://github.com/migueldeicaza/SwiftTerm.git
     from: "1.2.0"
+schemes:
+  CommandNotch:
+    build:
+      targets:
+        CommandNotch: all
+    test:
+      config: Debug
+      targets:
+        - CommandNotchTests
+        - CommandNotchUITests
+    run:
+      config: Debug
+    profile:
+      config: Release
+    analyze:
+      config: Debug
+    archive:
+      config: Release
+    management:
+      shared: true
+  Release-CommandNotch:
+    build:
+      targets:
+        CommandNotch: all
+    test:
+      config: Debug
+      targets:
+        - CommandNotchTests
+        - CommandNotchUITests
+    run:
+      config: Release
+    profile:
+      config: Release
+    analyze:
+      config: Debug
+    archive:
+      config: Release
+    management:
+      shared: true
 targets:
   CommandNotch:
     type: application
@@ -29,9 +68,9 @@ targets:
       properties:
         CFBundleName: CommandNotch
         CFBundleDisplayName: CommandNotch
-        CFBundleIdentifier: com.commandnotch.app
+        CFBundleIdentifier: "$(PRODUCT_BUNDLE_IDENTIFIER)"
         CFBundleVersion: "1"
-        CFBundleShortVersionString: "0.2.0"
+        CFBundleShortVersionString: "0.0.3"
         CFBundlePackageType: APPL
         CFBundleExecutable: CommandNotch
         LSMinimumSystemVersion: "14.0"

docs/workspace-split-pane-plan.md

@@ -0,0 +1,351 @@
+# Workspace Split Pane Plan
+
+## Purpose
+
+Capture the agreed design for workspace-owned split terminals so the feature can be implemented later without redoing scope and architecture decisions.
+
+## Agreed Scope
+
+- Split layouts belong to the workspace, not the screen.
+- A workspace may only be actively presented on one screen at a time.
+- Split layouts should be visible the same way when that workspace is opened on another monitor.
+- Nested splits are supported.
+- Any two tabs may be joined into a split.
+- Closing a pane causes its sibling to expand.
+- Split layout must survive relaunch.
+
+## Non-Goals
+
+- Simultaneous live rendering of the same workspace on multiple screens.
+- Full multi-user or collaborative state sync.
+- Arbitrary freeform pane layout. The model is tree-based binary splits.
+- Solving all interaction polish in the first pass.
+
+## Current Constraint
+
+The current workspace model is flat:
+
+- `WorkspaceController` owns `[TerminalSession]`
+- one tab is active at a time
+- `ContentView` renders exactly one active `SwiftTermView`
+
+This means split panes are not an additive UI feature. They require a workspace model refactor.
+
+## Recommended Model
+
+Do not model splits as "adjacent tabs with special behavior" internally.
+
+Instead:
+
+1. A workspace owns ordered top-level tabs.
+2. Each top-level tab owns a pane tree.
+3. Pane tree leaves own `TerminalSession` instances.
+4. Pane tree internal nodes represent binary splits.
+5. The tab bar can visually present grouped/joined tabs based on the active tab's pane composition.
+
+This keeps the domain model clean while still allowing the desired visual metaphor.
+
+## Proposed Domain Types
+
+```swift
+typealias WorkspaceTabID = UUID
+typealias PaneID = UUID
+
+struct WorkspaceTab: Identifiable, Equatable, Codable {
+    var id: WorkspaceTabID
+    var rootPane: PaneNode
+    var selectedPaneID: PaneID?
+    var titleMode: WorkspaceTabTitleMode
+}
+
+enum PaneNode: Equatable, Codable, Identifiable {
+    case leaf(PaneLeaf)
+    case split(PaneSplit)
+
+    var id: PaneID { ... }
+}
+
+struct PaneLeaf: Equatable, Codable, Identifiable {
+    var id: PaneID
+    var sessionID: UUID
+}
+
+struct PaneSplit: Equatable, Codable, Identifiable {
+    var id: PaneID
+    var axis: SplitAxis
+    var ratio: Double
+    var first: PaneNode
+    var second: PaneNode
+}
+
+enum SplitAxis: String, Codable {
+    case horizontal
+    case vertical
+}
+```
+
+Notes:
+
+- `ratio` should be persisted so user-adjusted divider positions survive relaunch.
+- `selectedPaneID` allows focus-based commands such as split active pane, close active pane, and move focus.
+- The persisted model should store session identity separately from runtime AppKit/SwiftTerm objects.
+
+## Runtime Ownership
+
+Global:
+
+- workspace summaries
+- workspace ordering
+- workspace-to-screen assignment
+- hotkeys
+
+Workspace:
+
+- ordered top-level tabs
+- active top-level tab
+- per-tab pane tree
+- active/selected pane
+- terminal sessions for pane leaves
+
+Screen:
+
+- which workspace is assigned
+- notch open/close state
+- geometry and transitions
+
+This remains aligned with the existing workspace architecture.
+
+## Persistence Strategy
+
+Split layout must survive relaunch, so workspace persistence needs to grow beyond summary metadata.
+
+Recommended approach:
+
+1. Keep `WorkspaceSummary` for list metadata only.
+2. Introduce a persisted `WorkspaceDocument` or `WorkspaceSnapshot` per workspace.
+3. Persist:
+   - top-level tabs
+   - pane tree
+   - active tab ID
+   - selected pane ID
+   - divider ratios
+4. Do not attempt to persist shell process contents.
+5. On relaunch, recreate sessions for pane leaves and restore layout structure only.
+
+Important distinction:
+
+- layout persistence is required
+- terminal process continuity is not
+
+## UI Model
+
+### Main Content
+
+The active top-level tab renders as a recursive split tree.
+
+- leaf node -> one `SwiftTermView`
+- split node -> `HSplitView`/`VSplitView` equivalent SwiftUI container with draggable divider
+
+### Tab Bar
+
+Top-level tabs remain the primary navigation unit.
+
+Visual behavior:
+
+- a normal unsplit tab looks like today
+- a joined/split tab should look grouped
+- grouped tabs should expose child pane titles visually inside the tab item
+
+Recommended first-pass appearance:
+
+- one outer tab pill per top-level tab
+- inside that pill, show compact child title chips for each leaf pane
+- highlight the selected pane's chip
+
+This gives the "tabs are joined" feel without making pane leaves first-class top-level tabs in the data model.
+
+## Command Model
+
+New actions likely needed:
+
+- split active pane horizontally
+- split active pane vertically
+- focus next pane
+- focus previous pane
+- close active pane
+- resize focused split divider
+- join tab A into tab B
+- detach pane into new top-level tab
+
+Semantics:
+
+- joining any two tabs merges one tab's root pane into the other's tree
+- the source top-level tab is removed
+- the destination top-level tab remains
+- sibling expansion on close is standard tree collapse
+
+## Join Semantics
+
+Joining any two tabs should work as:
+
+1. Choose destination tab.
+2. Choose source tab.
+3. Replace destination root with a new split node:
+   - first child = old destination root
+   - second child = source root
+4. Remove source tab from workspace order.
+5. Select a predictable pane, preferably the source pane that was just added.
+
+An explicit split axis should be required for the join action.
+
+## Close Semantics
+
+When closing a pane:
+
+- if the pane has a sibling, the sibling expands into the parent's position
+- if the pane was the only leaf in a top-level tab:
+  - close the whole top-level tab if more than one tab exists
+  - otherwise create a replacement shell pane, matching current single-tab safety behavior
+
+## Focus Semantics
+
+Pane focus must become explicit.
+
+Recommended rules:
+
+- mouse click focuses that pane
+- splitting focuses the new pane
+- joining focuses the moved-in pane
+- closing a pane focuses the surviving sibling
+- top-level tab switch restores the previously selected pane in that tab
+
+## Migration Path
+
+Implement in stages to reduce risk.
+
+### Stage 1: Domain Refactor
+
+- Replace flat workspace tabs with top-level tab objects.
+- Introduce pane tree types.
+- Keep only one leaf per tab initially so behavior is unchanged.
+
+### Stage 2: Runtime Layout Rendering
+
+- Render pane trees recursively in `ContentView`.
+- Add active pane selection.
+- Keep persistence off until runtime behavior is stable.
+
+### Stage 3: Split Actions
+
+- Split active pane horizontally/vertically.
+- Close pane with sibling expansion.
+- Basic focus movement.
+
+### Stage 4: Joined Tab UI
+
+- Update tab bar to show grouped child pane chips.
+- Surface active pane clearly.
+
+### Stage 5: Join / Unjoin Flows
+
+- Join any two tabs with explicit axis choice.
+- Support promoting a pane back to its own top-level tab if needed.
+
+### Stage 6: Persistence
+
+- Persist pane trees and top-level tab state.
+- Recreate sessions on launch.
+
+### Stage 7: Hotkeys and Polish
+
+- Add pane-focused shortcuts.
+- Add divider dragging polish.
+- Improve visual grouped-tab affordances.
+
+## Main Risks
+
+### 1. Model complexity
+
+The current flat `[TerminalSession]` model is simple. Tree-based layout introduces more state, more edge cases, and more focus semantics.
+
+Mitigation:
+
+- refactor the data model before touching complex UI
+- keep top-level tabs and pane leaves distinct
+
+### 2. SwiftTerm view ownership
+
+`TerminalView` cannot be mounted in multiple places safely.
+
+Mitigation:
+
+- preserve current rule: only one active presenting screen per workspace
+- keep one runtime `TerminalSession` per pane leaf
+
+### 3. Persistence mismatch
+
+Persisting layout is easy compared with persisting process state.
+
+Mitigation:
+
+- persist layout and selection only
+- recreate shell sessions on launch
+
+### 4. Joined-tab UX ambiguity
+
+If grouped tabs are also used as pane chips, the interaction model can get confusing.
+
+Mitigation:
+
+- preserve top-level tabs as the real navigation unit
+- use internal chips only as secondary indicators/actions
+
+## Recommended First Implementation Boundary
+
+The first deliverable should include:
+
+- nested binary split trees
+- active pane focus
+- split and close pane actions
+- sibling expansion
+- grouped tab appearance
+- join any two tabs
+- persisted layout across relaunch
+- same workspace layout when moved to another screen
+
+The first deliverable should not include:
+
+- simultaneous same-workspace rendering on multiple screens
+- drag-and-drop tree editing
+- restoring running shell process contents
+
+## Files Likely Impacted
+
+- `Downterm/CommandNotch/Models/WorkspaceController.swift`
+- `Downterm/CommandNotch/Models/WorkspaceRegistry.swift`
+- `Downterm/CommandNotch/Models/WorkspaceStore.swift`
+- `Downterm/CommandNotch/ContentView.swift`
+- `Downterm/CommandNotch/Components/TabBar.swift`
+- `Downterm/CommandNotch/Models/TerminalSession.swift`
+- workspace-related tests
+
+Likely new files:
+
+- pane tree domain types
+- persisted workspace document types
+- split-pane rendering view(s)
+- pane-focused command helpers
+
+## Decision Summary
+
+The feature is feasible.
+
+The correct architecture is:
+
+- workspace-owned split tree
+- top-level tabs remain the primary unit
+- grouped tab visuals are a UI layer over the pane tree
+- one presenting screen per workspace
+- persisted layout, not persisted process contents
+
+That is the implementation direction to use when this work is resumed.