From 16ee4576a9ff3c4f91cc30cb4cedbfb41fb3de14 Mon Sep 17 00:00:00 2001
From: Ariver <shanghai3168@gmail.com>
Date: Thu, 18 Jun 2026 20:50:58 +0800
Subject: [PATCH] Record UI implementation lesson

---
 C1.source/Sources/Aligner/QuickSwitchRootView.swift | 3753 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 3,432 insertions(+), 321 deletions(-)

diff --git a/C1.source/Sources/Aligner/QuickSwitchRootView.swift b/C1.source/Sources/Aligner/QuickSwitchRootView.swift
index 4e3051e..f127082 100644
--- a/C1.source/Sources/Aligner/QuickSwitchRootView.swift
+++ b/C1.source/Sources/Aligner/QuickSwitchRootView.swift
@@ -1,5 +1,6 @@
 import AppKit
 import QuartzCore
+import Darwin
 import AlignerCore
 
 enum QuickSwitchCommitSource: String {
@@ -9,7 +10,10 @@
 
 @MainActor
 final class QuickSwitchRootView: NSView {
+    private let backdropBlurView = NSVisualEffectView()
+    private let layerHostView = NSView()
     private let backgroundLayer = CAGradientLayer()
+    private let safeAreaFillLayer = CALayer()
     private let glassLayer = CALayer()
     private let laneLayer = CALayer()
     private let spaceLaneContentLayer = CALayer()
@@ -17,11 +21,17 @@
     private let appShelfContentLayer = CALayer()
     private let waterfallLayer = CALayer()
     private let waterfallContentLayer = CALayer()
+    private lazy var closeConfirmationLayers = makeCloseConfirmationLayers()
+    private let closeFeedbackLayer = CALayer()
+    private let closeFeedbackTextLayer = CATextLayer()
+    private let viewModeToggleButtonLayer = CALayer()
+    private let viewModeToggleIconLayer = CALayer()
     private let appIconProvider: any AppIconProviderProtocol = WorkspaceAppIconProvider()
     private let skeletonThumbnailProvider = NativeSkeletonThumbnailProvider(size: NSSize(width: 160, height: 96))
     private var screenshotSourcesByWindowID: [UInt32: ScreenshotResolutionSource] = [:]
     private var screenshotSkippedReasonsByWindowID: [UInt32: String] = [:]
     private var currentViewModel: QuickSwitchViewModel?
+    private var spaceLaneDisplayGroups: [SpaceLaneDisplayGroupLayers] = []
     private var spaceLaneSegments: [SpaceLaneSegmentLayers] = []
     private var spaceLaneContentWidth: CGFloat = 0
     private var spaceLaneScrollOffset: CGFloat = 0
@@ -33,13 +43,28 @@
     private var hoveredAppGroupIndex: Int?
     private var hoveredWindowID: UInt32?
     private var hoveredSpaceID: UInt64?
+    private var hoveredCloseTarget: CloseTarget?
+    private var pendingCloseTarget: CloseTarget?
+    private var pendingCloseRequest: QuickSwitchCloseRequest?
+    private var pendingCloseOptOut = false
+    private var closeConfirmationArrowEdge: CloseConfirmationArrowEdge?
+    private var closeConfirmationRequired = true
+    private var closeFeedback: CloseFeedback?
+    private var closeFeedbackHideTask: Task<Void, Never>?
+    private var isViewModeToggleButtonHovered = false
+    private var suppressViewModeToggleHoverPreview = false
+    private var hoverTarget: HoverTarget = .none
+    private var hoverTargetSource: HoverTargetSource = .event
     private var hoveredSpaceLaneID: UInt64?
     private var focusedSpaceID: UInt64?
     private var debugHoveredAppGroupIndex: Int?
     private var waterfallColumns: [WaterfallColumnLayers] = []
+    private var waterfallViewMode: QuickSwitchWaterfallViewMode = .verticalColumns
     private var waterfallContentWidth: CGFloat = 0
     private var waterfallScrollOffset: CGFloat = 0
     private var waterfallColumnScrollOffsets: [Int: CGFloat] = [:]
+    private var horizontalMasonryContentHeight: CGFloat = 0
+    private var horizontalMasonryScrollOffset: CGFloat = 0
     private var currentSelection: QuickSwitchSelection?
     private var columnSelectionHistory: [Int: Int] = [:]
     private var keyboardCommandsApplied: [String] = []
@@ -60,8 +85,140 @@
     private var keyboardResponseLatencyMilliseconds: [Double] = []
     private var mouseResponseLatencyMilliseconds: [Double] = []
     private var hoverResponseLatencyMilliseconds: [Double] = []
+    private var lastProjectionTransitionMovedLayerCount = 0
+    private var lastProjectionTransitionFadeInLayerCount = 0
+    private var lastProjectionTransitionFadeOutLayerCount = 0
+    private var lastProjectionTransitionDurationMilliseconds: Double = 0
+    private var suppressEventInput = false
+    private var suppressEventBackgroundClicks = false
     var onEscape: (() -> Void)?
     var onCommitSelection: ((QuickSwitchSelection, QuickSwitchCommitSource) -> Void)?
+    var onSpaceLaneClick: ((UInt64, Int) -> Void)?
+    var onBackgroundClick: (() -> Bool)?
+    var onToggleWaterfallViewMode: (() -> Void)?
+    var onRequestClose: ((QuickSwitchCloseRequest) -> Void)?
+    var onCloseConfirmationDisabled: (() -> Void)?
+
+    private enum CloseTarget: Equatable {
+        case app(appGroupIndex: Int)
+        case window(appGroupIndex: Int, windowIndex: Int, windowID: UInt32)
+
+        var kindDescription: String {
+            switch self {
+            case .app:
+                return "app"
+            case .window:
+                return "window"
+            }
+        }
+    }
+
+    private struct CloseButtonLayers {
+        let containerLayer: CALayer
+        let glyphLayer: CAShapeLayer
+    }
+
+    private struct CloseConfirmationLayers {
+        let containerLayer: CALayer
+        let backgroundLayer: CAShapeLayer
+        let titleLayer: CATextLayer
+        let messageLayer: CATextLayer
+        let checkboxLayer: CALayer
+        let checkboxMarkLayer: CATextLayer
+        let checkboxLabelLayer: CATextLayer
+        let confirmButtonLayer: CALayer
+        let confirmButtonTextLayer: CATextLayer
+        let cancelButtonLayer: CALayer
+        let cancelButtonTextLayer: CATextLayer
+    }
+
+    private struct CloseFeedback: Equatable, Sendable {
+        enum Kind: String, Sendable {
+            case progress
+            case failure
+        }
+
+        let kind: Kind
+        let message: String
+        let targetKind: String
+        let appGroupIndex: Int
+        let windowID: UInt32?
+    }
+
+    private enum CloseConfirmationArrowEdge: String {
+        case left
+        case right
+    }
+
+    private enum HoverTarget: Equatable {
+        case none
+        case space(UInt64)
+        case app(Int)
+        case window(appGroupIndex: Int, windowID: UInt32, spaceID: UInt64?)
+
+        var kindDescription: String {
+            switch self {
+            case .none:
+                return "none"
+            case .space:
+                return "space"
+            case .app:
+                return "app"
+            case .window:
+                return "window"
+            }
+        }
+
+        var appGroupIndex: Int? {
+            switch self {
+            case .app(let appGroupIndex):
+                return appGroupIndex
+            case .window(let appGroupIndex, _, _):
+                return appGroupIndex
+            case .none, .space:
+                return nil
+            }
+        }
+
+        var windowID: UInt32? {
+            switch self {
+            case .window(_, let windowID, _):
+                return windowID
+            case .none, .space, .app:
+                return nil
+            }
+        }
+
+        var spaceID: UInt64? {
+            switch self {
+            case .space(let spaceID):
+                return spaceID
+            case .window(_, _, let spaceID):
+                return spaceID
+            case .none, .app:
+                return nil
+            }
+        }
+
+        var spaceLaneID: UInt64? {
+            guard case .space(let spaceID) = self else { return nil }
+            return spaceID
+        }
+
+        var shouldAlignWaterfallWithAppShelf: Bool {
+            switch self {
+            case .app:
+                return true
+            case .none, .space, .window:
+                return false
+            }
+        }
+    }
+
+    private enum HoverTargetSource: String {
+        case event
+        case debug
+    }
 
     private struct SpaceLaneSegmentLayers {
         let space: QuickSwitchSpaceViewModel
@@ -69,18 +226,27 @@
         let labelLayer: CATextLayer
         let countLayer: CATextLayer
         let appLayer: CATextLayer
+        let splitAppLayers: [CATextLayer]
         let windowBlocks: [CALayer]
         let fullscreenMarkerLayer: CALayer?
+    }
+
+    private struct SpaceLaneDisplayGroupLayers {
+        let display: QuickSwitchDisplayViewModel
+        let containerLayer: CALayer
+        let segments: [SpaceLaneSegmentLayers]
     }
 
     private struct AppShelfItemLayers {
         let item: QuickSwitchAppShelfItemViewModel
         let containerLayer: CALayer
         let backgroundLayer: CALayer
+        let indexLayer: CATextLayer
         let iconLayer: CALayer
         let labelLayer: CATextLayer
         let badgeLayer: CATextLayer
         let selectedIndicatorLayer: CALayer
+        let closeButton: CloseButtonLayers
     }
 
     private struct AppShelfLayout {
@@ -100,12 +266,30 @@
     private struct WaterfallCardLayers {
         let item: QuickSwitchWindowCardViewModel
         let containerLayer: CALayer
+        let titleBarLayer: CALayer
         let titleLayer: CATextLayer
         let metaLayer: CATextLayer
         let thumbnailLayer: CALayer
         let appIconLayer: CALayer
         let stateLayer: CATextLayer
         let shineLayer: CAGradientLayer
+        let closeButton: CloseButtonLayers
+    }
+
+    private struct ProjectionLayerSnapshot {
+        let layer: CALayer
+        let frame: CGRect
+    }
+
+    private struct ProjectionColumnSnapshot {
+        let layer: CALayer
+        let frame: CGRect
+        let cardsByWindowID: [UInt32: ProjectionLayerSnapshot]
+    }
+
+    private struct ProjectionTransitionSnapshot {
+        let appShelfItemsByAppGroupIndex: [Int: ProjectionLayerSnapshot]
+        let waterfallColumnsByAppGroupIndex: [Int: ProjectionColumnSnapshot]
     }
 
     private enum AppShelfMetrics {
@@ -116,6 +300,36 @@
         static let normalGap: CGFloat = 16
         static let minGap: CGFloat = 8
         static let maxRows = 2
+        static let indexFontSize: CGFloat = 15
+        static let compressedIndexFontSize: CGFloat = 13
+        static let indexWidth: CGFloat = 16
+        static let indexHeight: CGFloat = 18
+    }
+
+    private enum RootLayoutMetrics {
+        static let horizontalMargin: CGFloat = 24
+        static let topContentMargin: CGFloat = 24
+        static let shelfGap: CGFloat = 16
+        static let waterfallTopGap: CGFloat = 14
+        static let bottomMargin: CGFloat = 34
+    }
+
+    private enum ViewModeToggleMetrics {
+        static let hitSize: CGFloat = 34
+        static let visualSize: CGFloat = 30
+        static let cornerRadius: CGFloat = 9
+        static let iconInset: CGFloat = 7
+        static let glyphLineWidth: CGFloat = 1.65
+        static let glyphCornerRadius: CGFloat = 2.1
+        static let selectedShadowRadius: CGFloat = 10
+        static let idleShadowRadius: CGFloat = 5
+    }
+
+    private enum ViewModeToggleVisualState: String {
+        case horizontalAvailable = "H1"
+        case horizontalSelected = "H2"
+        case verticalAvailable = "Z1"
+        case verticalSelected = "Z2"
     }
 
     private enum WaterfallMetrics {
@@ -123,11 +337,25 @@
         static let columnWidth: CGFloat = 252
         static let columnMinWidth: CGFloat = 220
         static let columnMaxWidth: CGFloat = 292
-        static let columnPadding: CGFloat = 12
+        static let contentHorizontalPadding: CGFloat = 0
+        static let columnHorizontalPadding: CGFloat = 0
+        static let columnVerticalPadding: CGFloat = 0
+        static let columnHeaderTextInset: CGFloat = 12
         static let headerHeight: CGFloat = 34
-        static let cardHeight: CGFloat = 118
+        static let cardHeight: CGFloat = 138
         static let cardGap: CGFloat = 12
         static let revealPadding: CGFloat = 24
+        static let horizontalRevealPadding: CGFloat = 0
+    }
+
+    private enum HorizontalMasonryMetrics {
+        static let horizontalPadding: CGFloat = 12
+        static let verticalPadding: CGFloat = 0
+        static let horizontalGap: CGFloat = 16
+        static let verticalGap: CGFloat = WaterfallMetrics.cardGap
+        static let cardMinWidth: CGFloat = 220
+        static let cardMaxWidth: CGFloat = 320
+        static let cardHeight: CGFloat = WaterfallMetrics.cardHeight
     }
 
     private enum WaterfallHorizontalIntent {
@@ -141,14 +369,28 @@
         static let animationTimingName = CAMediaTimingFunctionName.easeOut
     }
 
+    private enum SpaceLaneMetrics {
+        static let horizontalPadding: CGFloat = 0
+        static let groupGap: CGFloat = 36
+        static let groupHorizontalPadding: CGFloat = 24
+        static let groupVerticalPadding: CGFloat = 6
+        static let segmentGap: CGFloat = 12
+        static let segmentMinWidth: CGFloat = 96
+        static let segmentMaxWidth: CGFloat = 150
+    }
+
     override init(frame frameRect: NSRect) {
         super.init(frame: frameRect)
+        setupBackdropBlurView()
+        setupLayerHostView()
         wantsLayer = true
         setupLayers()
     }
 
     required init?(coder: NSCoder) {
         super.init(coder: coder)
+        setupBackdropBlurView()
+        setupLayerHostView()
         wantsLayer = true
         setupLayers()
     }
@@ -166,7 +408,7 @@
 
         let trackingArea = NSTrackingArea(
             rect: bounds,
-            options: [.activeInKeyWindow, .mouseMoved, .mouseEnteredAndExited, .inVisibleRect],
+            options: [.activeAlways, .mouseMoved, .mouseEnteredAndExited, .inVisibleRect],
             owner: self,
             userInfo: nil
         )
@@ -176,10 +418,19 @@
 
     override func layout() {
         super.layout()
+        backdropBlurView.frame = bounds
+        layerHostView.frame = bounds
         layoutLayers()
     }
 
     override func keyDown(with event: NSEvent) {
+        if suppressEventInput {
+            DevelopmentDiagnostics.log("quickSwitch.view.keyDown.ignoredForDebugSequence", [
+                "keyCode": event.keyCode
+            ])
+            return
+        }
+
         switch event.keyCode {
         case TriggerKeyCode.escape where Self.shouldDismissOnEscape(event):
             onEscape?()
@@ -201,6 +452,8 @@
     }
 
     override func scrollWheel(with event: NSEvent) {
+        refreshHoverTarget(at: event.locationInWindow)
+
         let dominantDelta = abs(event.scrollingDeltaX) >= abs(event.scrollingDeltaY)
             ? event.scrollingDeltaX
             : event.scrollingDeltaY
@@ -220,6 +473,15 @@
         }
 
         if shouldScrollWaterfall(for: event) {
+            if isHorizontalMasonryMode {
+                let currentOffset = horizontalMasonryScrollOffset
+                horizontalMasonryScrollOffset = clampedHorizontalMasonryOffset(
+                    currentOffset - event.scrollingDeltaY
+                )
+                needsLayout = true
+                return
+            }
+
             if abs(event.scrollingDeltaX) >= abs(event.scrollingDeltaY), waterfallAlignmentScrollable {
                 waterfallScrollOffset = clampedWaterfallAlignmentOffset(waterfallScrollOffset - event.scrollingDeltaX)
                 needsLayout = true
@@ -246,50 +508,68 @@
     override func mouseMoved(with event: NSEvent) {
         guard debugHoveredAppGroupIndex == nil else { return }
 
-        if let segment = spaceLaneSegment(at: event.locationInWindow) {
-            hoverSpaceLaneSegment(segment)
+        let toggleHovered = viewModeToggleButtonContains(windowLocation: event.locationInWindow)
+        if !toggleHovered {
+            suppressViewModeToggleHoverPreview = false
+        }
+        let shouldShowToggleHoverPreview = toggleHovered && !suppressViewModeToggleHoverPreview
+        if isViewModeToggleButtonHovered != shouldShowToggleHoverPreview {
+            isViewModeToggleButtonHovered = shouldShowToggleHoverPreview
+            needsLayout = true
+        }
+        if toggleHovered {
+            hoveredCloseTarget = nil
+            setHoverTarget(.none)
             return
         }
 
-        if let card = waterfallCard(at: event.locationInWindow) {
-            hoveredSpaceLaneID = nil
-            updateHoverState(
-                appGroupIndex: card.item.appGroupIndex,
-                windowID: card.item.window.id,
-                spaceID: card.item.primarySpaceID
-            )
-            return
+        let closeTarget = closeButtonTarget(at: event.locationInWindow)
+        if hoveredCloseTarget != closeTarget {
+            hoveredCloseTarget = closeTarget
+            needsLayout = true
         }
-
-        if let item = appShelfItem(at: event.locationInWindow) {
-            hoveredSpaceLaneID = nil
-            updateHoverState(
-                appGroupIndex: item.item.appGroupIndex,
-                windowID: nil,
-                spaceID: nil,
-                alignsWaterfallWithAppShelf: true
-            )
-            return
-        }
-
-        hoveredSpaceLaneID = nil
-        updateHoverState(appGroupIndex: nil, windowID: nil, spaceID: nil)
+        refreshHoverTarget(at: event.locationInWindow)
     }
 
     override func mouseExited(with event: NSEvent) {
         guard debugHoveredAppGroupIndex == nil else { return }
-        hoveredSpaceLaneID = nil
-        updateHoverState(appGroupIndex: nil, windowID: nil, spaceID: nil)
+        isViewModeToggleButtonHovered = false
+        suppressViewModeToggleHoverPreview = false
+        hoveredCloseTarget = nil
+        setHoverTarget(.none)
     }
 
     override func mouseDown(with event: NSEvent) {
+        if suppressEventInput {
+            DevelopmentDiagnostics.log("quickSwitch.view.mouseDown.ignoredForDebugSequence", [
+                "x": event.locationInWindow.x,
+                "y": event.locationInWindow.y,
+                "bounds": NSStringFromRect(bounds)
+            ])
+            return
+        }
+
+        if handleCloseConfirmationMouseDown(at: event.locationInWindow) {
+            return
+        }
+
+        if viewModeToggleButtonContains(windowLocation: event.locationInWindow) {
+            clickViewModeToggleButton(source: "mouse")
+            return
+        }
+
+        if let closeTarget = closeButtonTarget(at: event.locationInWindow) {
+            beginCloseConfirmation(for: closeTarget)
+            return
+        }
+
         if let card = waterfallCard(at: event.locationInWindow) {
             clickWindowCard(card)
             return
         }
 
         if let segment = spaceLaneSegment(at: event.locationInWindow) {
-            clickSpaceLaneSegment(segment)
+            clickSpaceLaneSegment(segment, clickCount: max(1, event.clickCount))
             return
         }
 
@@ -303,15 +583,16 @@
             "y": event.locationInWindow.y,
             "bounds": NSStringFromRect(bounds)
         ])
+        if !suppressEventBackgroundClicks, onBackgroundClick?() == true {
+            return
+        }
         super.mouseDown(with: event)
     }
 
     func setDebugHoveredAppGroupIndex(_ index: Int?) {
         debugHoveredAppGroupIndex = index
+        setHoverTarget(.none, source: .debug)
         hoveredAppGroupIndex = index
-        hoveredWindowID = nil
-        hoveredSpaceID = nil
-        hoveredSpaceLaneID = nil
         needsLayout = true
     }
 
@@ -342,7 +623,19 @@
             if isHoverCommand(command) {
                 hoverResponseLatencyMilliseconds.append(elapsed)
             }
+            if lastCommitSource == .mouse {
+                break
+            }
         }
+    }
+
+    func setSuppressEventBackgroundClicks(_ suppressed: Bool) {
+        suppressEventBackgroundClicks = suppressed
+    }
+
+    func setSuppressEventInput(_ suppressed: Bool) {
+        suppressEventInput = suppressed
+        suppressEventBackgroundClicks = suppressed
     }
 
     func beginPerformanceFirstFrameMeasurement() {
@@ -366,6 +659,65 @@
         hoverResponseLatencyMilliseconds = []
     }
 
+    func setCloseConfirmationRequired(_ required: Bool) {
+        closeConfirmationRequired = required
+        if !required {
+            pendingCloseTarget = nil
+            pendingCloseRequest = nil
+            pendingCloseOptOut = false
+            closeConfirmationLayers.containerLayer.isHidden = true
+            closeConfirmationArrowEdge = nil
+        }
+        needsLayout = true
+    }
+
+    func setWaterfallViewMode(_ mode: QuickSwitchWaterfallViewMode) {
+        guard waterfallViewMode != mode else { return }
+
+        waterfallViewMode = mode
+        waterfallScrollOffset = 0
+        waterfallColumnScrollOffsets = [:]
+        horizontalMasonryScrollOffset = 0
+        horizontalMasonryContentHeight = 0
+        needsLayout = true
+    }
+
+    func showCloseProgress(for request: QuickSwitchCloseRequest) {
+        setCloseFeedback(
+            CloseFeedback(
+                kind: .progress,
+                message: "正在关闭...",
+                targetKind: request.kindDescription,
+                appGroupIndex: request.appGroupIndex,
+                windowID: request.windowID
+            ),
+            autoHideAfter: nil
+        )
+    }
+
+    func showCloseFailure(message: String, for request: QuickSwitchCloseRequest) {
+        setCloseFeedback(
+            CloseFeedback(
+                kind: .failure,
+                message: message,
+                targetKind: request.kindDescription,
+                appGroupIndex: request.appGroupIndex,
+                windowID: request.windowID
+            ),
+            autoHideAfter: 2.75
+        )
+    }
+
+    func clearCloseFeedback() {
+        closeFeedbackHideTask?.cancel()
+        closeFeedbackHideTask = nil
+        closeFeedback = nil
+        closeFeedbackLayer.isHidden = true
+        closeFeedbackLayer.opacity = 0
+        closeFeedbackTextLayer.string = ""
+        needsLayout = true
+    }
+
     func applyScreenshot(_ resolution: ScreenshotResolution, for windowID: UInt32) {
         screenshotSkippedReasonsByWindowID[windowID] = nil
         screenshotSourcesByWindowID[windowID] = resolution.source
@@ -373,7 +725,9 @@
         guard let card = waterfallCardsByWindowID()[windowID] else { return }
         card.thumbnailLayer.contents = resolution.image
         if case .realScreenshot = resolution.source {
-            card.shineLayer.opacity = card.item.window.id == effectiveSelection?.windowID ? 1 : 0
+            let isSelected = card.item.window.id == effectiveSelection?.windowID
+            let isHovered = card.item.window.id == hoveredWindowID
+            card.shineLayer.opacity = shouldShowSelectedVisual(isSelected: isSelected, isHovered: isHovered) ? 1 : 0
         }
         needsLayout = true
     }
@@ -390,43 +744,380 @@
         }
     }
 
+    func effectiveSelectionForProjection() -> QuickSwitchSelection? {
+        effectiveSelection
+    }
+
     func apply(viewModel: QuickSwitchViewModel?) {
+        apply(viewModel: viewModel, preservingInteractionState: false, animatedProjection: false)
+    }
+
+    func applyProjected(viewModel: QuickSwitchViewModel?) {
+        apply(viewModel: viewModel, preservingInteractionState: true, animatedProjection: true)
+    }
+
+    func hoverNextAppGroupIndex(cycleForward: Bool = true) -> Bool {
+        guard !appShelfItems.isEmpty else {
+            return false
+        }
+
+        let orderedIndexes = appShelfItems.map(\.item.appGroupIndex)
+        let sortedIndexes = orderedIndexes
+
+        var currentIndexPosition: Int?
+        if let currentHovered = effectiveHoveredAppGroupIndex {
+            currentIndexPosition = sortedIndexes.firstIndex(of: currentHovered)
+        }
+
+        let nextPosition = currentIndexPosition.map { current in
+            if cycleForward {
+                (current + 1) % sortedIndexes.count
+            } else {
+                (current - 1 + sortedIndexes.count) % sortedIndexes.count
+            }
+        } ?? 0
+
+        let nextAppGroupIndex = sortedIndexes[nextPosition]
+        hoverAppGroup(nextAppGroupIndex)
+        return true
+    }
+
+    private func apply(
+        viewModel: QuickSwitchViewModel?,
+        preservingInteractionState: Bool,
+        animatedProjection: Bool
+    ) {
+        let preservedWindowThumbnails = preservingInteractionState ? cachedThumbnailsByWindowID() : [:]
+        let transitionSnapshot = animatedProjection ? captureProjectionTransitionSnapshot() : nil
+        if !animatedProjection {
+            resetProjectionTransitionReport()
+        }
         currentViewModel = viewModel
-        screenshotSourcesByWindowID = [:]
-        screenshotSkippedReasonsByWindowID = [:]
-        currentSelection = viewModel?.initialSelection
-        columnSelectionHistory = [:]
-        keyboardCommandsApplied = []
-        lastKeyboardCommand = nil
-        tabIgnoredCount = 0
-        lastCommittedSelection = nil
-        lastCommitSource = nil
-        mouseCommandsApplied = []
-        lastMouseCommand = nil
-        lastClickedAppGroupIndex = nil
-        lastAppShelfClickChangedSelection = nil
-        lastClickedWindowID = nil
-        lastSpaceFocusedAppGroupIndex = nil
-        lastSpaceLaneClickSpaceID = nil
-        lastAppShelfScrollSyncedAppGroupIndex = nil
-        hoveredWindowID = nil
-        hoveredSpaceID = nil
-        hoveredSpaceLaneID = nil
-        focusedSpaceID = nil
-        if debugHoveredAppGroupIndex == nil {
-            hoveredAppGroupIndex = nil
+
+        if preservingInteractionState {
+            currentSelection = validSelection(currentSelection, in: viewModel) ?? viewModel?.initialSelection
+            columnSelectionHistory = columnSelectionHistory.filter { appGroupIndex, _ in
+                viewModel?.waterfallColumns.contains { $0.appGroupIndex == appGroupIndex } == true
+            }
+            if let currentSelection {
+                columnSelectionHistory[currentSelection.appGroupIndex] = currentSelection.windowIndex
+            }
+            hoveredCloseTarget = nil
+            pendingCloseTarget = nil
+            pendingCloseRequest = nil
+            pendingCloseOptOut = false
+            closeConfirmationLayers.containerLayer.isHidden = true
+            closeConfirmationArrowEdge = nil
         } else {
+            screenshotSourcesByWindowID = [:]
+            screenshotSkippedReasonsByWindowID = [:]
+            currentSelection = viewModel?.initialSelection
+            columnSelectionHistory = [:]
+            keyboardCommandsApplied = []
+            lastKeyboardCommand = nil
+            tabIgnoredCount = 0
+            lastCommittedSelection = nil
+            lastCommitSource = nil
+            mouseCommandsApplied = []
+            lastMouseCommand = nil
+            lastClickedAppGroupIndex = nil
+            lastAppShelfClickChangedSelection = nil
+            lastClickedWindowID = nil
+            lastSpaceFocusedAppGroupIndex = nil
+            lastSpaceLaneClickSpaceID = nil
+            lastAppShelfScrollSyncedAppGroupIndex = nil
+            waterfallScrollOffset = 0
+            waterfallColumnScrollOffsets = [:]
+            horizontalMasonryScrollOffset = 0
+            horizontalMasonryContentHeight = 0
+            focusedSpaceID = nil
+            hoveredCloseTarget = nil
+            pendingCloseTarget = nil
+            pendingCloseRequest = nil
+            pendingCloseOptOut = false
+            closeConfirmationLayers.containerLayer.isHidden = true
+            closeConfirmationArrowEdge = nil
+            clearCloseFeedback()
+            setHoverTarget(.none)
             hoveredAppGroupIndex = debugHoveredAppGroupIndex
         }
+
         if let currentSelection {
             columnSelectionHistory[currentSelection.appGroupIndex] = currentSelection.windowIndex
         }
         rebuildSpaceLaneSegments()
         rebuildAppShelfItems()
         rebuildWaterfallColumns()
+
+        if preservingInteractionState {
+            restoreThumbnailsFromCache(preservedWindowThumbnails)
+        }
+
         needsLayout = true
         ensureCurrentSelectionVisible(horizontalIntent: .alignWithAppShelf(animated: false))
         needsLayout = true
+        if animatedProjection, let transitionSnapshot {
+            layoutSubtreeIfNeeded()
+            applyProjectionTransitionAnimations(from: transitionSnapshot)
+        }
+    }
+
+    private func cachedThumbnailsByWindowID() -> [UInt32: Any] {
+        var snapshots: [UInt32: Any] = [:]
+
+        for card in waterfallCardsByWindowID().values {
+            snapshots[card.item.window.id] = card.thumbnailLayer.contents
+        }
+
+        return snapshots
+    }
+
+    private func restoreThumbnailsFromCache(_ cachedThumbnails: [UInt32: Any]) {
+        for card in waterfallCardsByWindowID().values {
+            if let thumbnail = cachedThumbnails[card.item.window.id] {
+                card.thumbnailLayer.contents = thumbnail
+            }
+        }
+    }
+
+    private func validSelection(
+        _ selection: QuickSwitchSelection?,
+        in viewModel: QuickSwitchViewModel?
+    ) -> QuickSwitchSelection? {
+        guard let selection, let viewModel else { return nil }
+
+        for column in viewModel.waterfallColumns {
+            if let card = column.windows.first(where: { $0.window.id == selection.windowID }) {
+                return QuickSwitchSelection(
+                    appGroupIndex: card.appGroupIndex,
+                    windowIndex: card.windowIndex,
+                    windowID: card.window.id
+                )
+            }
+        }
+
+        return nil
+    }
+
+    private func captureProjectionTransitionSnapshot() -> ProjectionTransitionSnapshot {
+        ProjectionTransitionSnapshot(
+            appShelfItemsByAppGroupIndex: Dictionary(
+                uniqueKeysWithValues: appShelfItems.map { item in
+                    (
+                        item.item.appGroupIndex,
+                        ProjectionLayerSnapshot(
+                            layer: item.containerLayer,
+                            frame: item.containerLayer.frame
+                        )
+                    )
+                }
+            ),
+            waterfallColumnsByAppGroupIndex: Dictionary(
+                uniqueKeysWithValues: waterfallColumns.map { column in
+                    (
+                        column.column.appGroupIndex,
+                        ProjectionColumnSnapshot(
+                            layer: column.containerLayer,
+                            frame: column.containerLayer.frame,
+                            cardsByWindowID: Dictionary(
+                                uniqueKeysWithValues: column.cards.map { card in
+                                    (
+                                        card.item.window.id,
+                                        ProjectionLayerSnapshot(
+                                            layer: card.containerLayer,
+                                            frame: card.containerLayer.frame
+                                        )
+                                    )
+                                }
+                            )
+                        )
+                    )
+                }
+            )
+        )
+    }
+
+    private func applyProjectionTransitionAnimations(from snapshot: ProjectionTransitionSnapshot) {
+        let reduceMotion = NSWorkspace.shared.accessibilityDisplayShouldReduceMotion
+        let duration: CFTimeInterval = reduceMotion ? 0.12 : 0.21
+        let timing = CAMediaTimingFunction(name: reduceMotion ? .linear : .easeOut)
+        var movedLayerCount = 0
+        var fadeInLayerCount = 0
+        var fadeOutLayerCount = 0
+
+        for item in appShelfItems {
+            guard let oldSnapshot = snapshot.appShelfItemsByAppGroupIndex[item.item.appGroupIndex] else {
+                if addFadeInAnimation(to: item.containerLayer, duration: duration, timing: timing) {
+                    fadeInLayerCount += 1
+                }
+                continue
+            }
+            if addPositionAnimation(to: item.containerLayer, from: oldSnapshot.frame, duration: duration, timing: timing) {
+                movedLayerCount += 1
+            }
+        }
+
+        let visibleAppGroupIndexes = Set(appShelfItems.map(\.item.appGroupIndex))
+        for (appGroupIndex, oldSnapshot) in snapshot.appShelfItemsByAppGroupIndex
+            where !visibleAppGroupIndexes.contains(appGroupIndex) {
+            if addFadeOutSnapshot(
+                oldSnapshot,
+                to: appShelfContentLayer,
+                frame: oldSnapshot.frame,
+                duration: duration,
+                timing: timing
+            ) {
+                fadeOutLayerCount += 1
+            }
+        }
+
+        for column in waterfallColumns {
+            guard let oldSnapshot = snapshot.waterfallColumnsByAppGroupIndex[column.column.appGroupIndex] else {
+                if addFadeInAnimation(to: column.containerLayer, duration: duration, timing: timing) {
+                    fadeInLayerCount += 1
+                }
+                continue
+            }
+            if addPositionAnimation(to: column.containerLayer, from: oldSnapshot.frame, duration: duration, timing: timing) {
+                movedLayerCount += 1
+            }
+
+            for card in column.cards {
+                guard let oldCardSnapshot = oldSnapshot.cardsByWindowID[card.item.window.id] else {
+                    if addFadeInAnimation(to: card.containerLayer, duration: duration, timing: timing) {
+                        fadeInLayerCount += 1
+                    }
+                    continue
+                }
+                if addPositionAnimation(to: card.containerLayer, from: oldCardSnapshot.frame, duration: duration, timing: timing) {
+                    movedLayerCount += 1
+                }
+            }
+        }
+
+        let visibleColumnsByAppGroupIndex = Dictionary(
+            uniqueKeysWithValues: waterfallColumns.map { ($0.column.appGroupIndex, $0) }
+        )
+        for (appGroupIndex, oldSnapshot) in snapshot.waterfallColumnsByAppGroupIndex {
+            guard let visibleColumn = visibleColumnsByAppGroupIndex[appGroupIndex] else {
+                if addFadeOutSnapshot(
+                    ProjectionLayerSnapshot(layer: oldSnapshot.layer, frame: oldSnapshot.frame),
+                    to: waterfallContentLayer,
+                    frame: oldSnapshot.frame,
+                    duration: duration,
+                    timing: timing
+                ) {
+                    fadeOutLayerCount += 1
+                }
+                continue
+            }
+
+            let visibleWindowIDs = Set(visibleColumn.cards.map(\.item.window.id))
+            for (windowID, oldCardSnapshot) in oldSnapshot.cardsByWindowID
+                where !visibleWindowIDs.contains(windowID) {
+                let absoluteFrame = oldCardSnapshot.frame.offsetBy(
+                    dx: oldSnapshot.frame.minX,
+                    dy: oldSnapshot.frame.minY
+                )
+                if addFadeOutSnapshot(
+                    oldCardSnapshot,
+                    to: waterfallContentLayer,
+                    frame: absoluteFrame,
+                    duration: duration,
+                    timing: timing
+                ) {
+                    fadeOutLayerCount += 1
+                }
+            }
+        }
+
+        lastProjectionTransitionMovedLayerCount = movedLayerCount
+        lastProjectionTransitionFadeInLayerCount = fadeInLayerCount
+        lastProjectionTransitionFadeOutLayerCount = fadeOutLayerCount
+        lastProjectionTransitionDurationMilliseconds = duration * 1_000
+    }
+
+    private func resetProjectionTransitionReport() {
+        lastProjectionTransitionMovedLayerCount = 0
+        lastProjectionTransitionFadeInLayerCount = 0
+        lastProjectionTransitionFadeOutLayerCount = 0
+        lastProjectionTransitionDurationMilliseconds = 0
+    }
+
+    @discardableResult
+    private func addPositionAnimation(
+        to layer: CALayer,
+        from oldFrame: CGRect,
+        duration: CFTimeInterval,
+        timing: CAMediaTimingFunction
+    ) -> Bool {
+        let oldPosition = CGPoint(x: oldFrame.midX, y: oldFrame.midY)
+        let newPosition = layer.position
+        guard abs(oldPosition.x - newPosition.x) > 0.5 || abs(oldPosition.y - newPosition.y) > 0.5 else {
+            return false
+        }
+
+        let animation = CABasicAnimation(keyPath: "position")
+        animation.fromValue = oldPosition
+        animation.toValue = newPosition
+        animation.duration = duration
+        animation.timingFunction = timing
+        animation.isRemovedOnCompletion = true
+        layer.add(animation, forKey: "quickSwitchProjectionPosition")
+        return true
+    }
+
+    @discardableResult
+    private func addFadeInAnimation(
+        to layer: CALayer,
+        duration: CFTimeInterval,
+        timing: CAMediaTimingFunction
+    ) -> Bool {
+        let animation = CABasicAnimation(keyPath: "opacity")
+        animation.fromValue = 0
+        animation.toValue = layer.opacity
+        animation.duration = duration
+        animation.timingFunction = timing
+        animation.isRemovedOnCompletion = true
+        layer.add(animation, forKey: "quickSwitchProjectionFadeIn")
+        return true
+    }
+
+    @discardableResult
+    private func addFadeOutSnapshot(
+        _ snapshot: ProjectionLayerSnapshot,
+        to parentLayer: CALayer,
+        frame: CGRect,
+        duration: CFTimeInterval,
+        timing: CAMediaTimingFunction
+    ) -> Bool {
+        let layer = snapshot.layer
+        layer.removeAllAnimations()
+        layer.removeFromSuperlayer()
+        CATransaction.begin()
+        CATransaction.setDisableActions(true)
+        layer.frame = frame
+        layer.opacity = max(layer.opacity, 0.01)
+        layer.zPosition = max(layer.zPosition, 240)
+        parentLayer.addSublayer(layer)
+        CATransaction.commit()
+
+        let animation = CABasicAnimation(keyPath: "opacity")
+        animation.fromValue = layer.opacity
+        animation.toValue = 0
+        animation.duration = duration
+        animation.timingFunction = timing
+        animation.isRemovedOnCompletion = true
+        CATransaction.begin()
+        CATransaction.setDisableActions(true)
+        layer.opacity = 0
+        CATransaction.commit()
+        layer.add(animation, forKey: "quickSwitchProjectionFadeOut")
+
+        DispatchQueue.main.asyncAfter(deadline: .now() + duration + 0.05) { [weak layer] in
+            layer?.removeFromSuperlayer()
+        }
+        return true
     }
 
     func reportDictionary() -> [String: Any] {
@@ -443,19 +1134,49 @@
             "viewClass": String(describing: Self.self),
             "isLayerBacked": wantsLayer,
             "bounds": dictionary(from: bounds),
+            "safeAreaTopInset": Double(topSafeAreaInset),
+            "safeAreaFillFrame": dictionary(from: safeAreaFillLayer.frame),
             "glassFrame": dictionary(from: glassLayer.frame),
+            "glassCornerRadius": Double(glassLayer.cornerRadius),
+            "glassBorderWidth": Double(glassLayer.borderWidth),
+            "glassShadowOpacity": Double(glassLayer.shadowOpacity),
             "spaceLaneFrame": dictionary(from: laneLayer.frame),
+            "spaceLaneBackgroundColor": colorDictionary(from: laneLayer.backgroundColor),
+            "spaceLaneCornerRadius": Double(laneLayer.cornerRadius),
             "spaceLaneContentWidth": Double(spaceLaneContentWidth),
             "spaceLaneVisibleWidth": Double(laneLayer.bounds.width),
             "spaceLaneMaxScrollOffset": Double(spaceLaneMaxScrollOffset),
             "spaceLaneScrollable": spaceLaneMaxScrollOffset > 0,
+            "spaceLaneDisplayGroupCount": spaceLaneDisplayGroups.count,
+            "spaceLaneDisplayGroups": spaceLaneDisplayGroupReports(),
             "spaceLaneSegmentCount": spaceLaneSegments.count,
             "spaceLaneLabels": currentViewModel?.displays.flatMap { $0.spaces.map(\.label) } ?? [],
             "spaceLaneSegments": spaceLaneSegmentReports(),
+            "hoverTargetKind": hoverTarget.kindDescription,
+            "hoverTargetSource": hoverTargetSource.rawValue,
             "spaceLaneHoveredSpaceID": hoveredSpaceLaneID ?? NSNull(),
             "spaceLaneFocusedSpaceID": focusedSpaceID ?? NSNull(),
             "activeSpaceFocusID": activeSpaceFocusID ?? NSNull(),
+            "spaceFilterLockedSpaceID": currentViewModel?.lockedSpaceID ?? NSNull(),
+            "spaceFilterActive": currentViewModel?.lockedSpaceID != nil,
+            "viewModeToggleButtonVisible": !viewModeToggleButtonLayer.isHidden,
+            "viewModeToggleButtonHovered": isViewModeToggleButtonHovered,
+            "viewModeToggleHoverPreviewSuppressed": suppressViewModeToggleHoverPreview,
+            "viewModeToggleButtonFrame": dictionary(from: viewModeToggleButtonLayer.frame),
+            "viewModeToggleHitSize": Double(ViewModeToggleMetrics.hitSize),
+            "viewModeToggleVisualSize": Double(ViewModeToggleMetrics.visualSize),
+            "viewModeToggleCurrentMode": waterfallViewMode.rawValue,
+            "viewModeToggleTargetMode": nextWaterfallViewMode.rawValue,
+            "viewModeToggleIconKind": viewModeToggleIconKind,
+            "viewModeToggleVisualState": viewModeToggleVisualState.rawValue,
+            "viewModeToggleStandardBlueColor": colorDictionary(from: viewModeToggleBlueColor.cgColor),
+            "viewModeToggleGlyphLineWidth": Double(ViewModeToggleMetrics.glyphLineWidth),
+            "viewModeToggleAccessibilityLabel": viewModeToggleAccessibilityLabel,
+            "settingsButtonVisible": false,
             "spaceFocusAppGroupIndexes": spaceFocusedAppGroupIndexes(),
+            "appHoverAssociatedSpaceIDs": appHoverAssociatedSpaceIDs.sorted(),
+            "appHoverAssociatedSpaceLabels": appHoverAssociatedSpaceLabels,
+            "windowHoverAssociatedSpaceID": windowHoverAssociatedSpaceID ?? NSNull(),
             "lastSpaceFocusedAppGroupIndex": lastSpaceFocusedAppGroupIndex ?? NSNull(),
             "lastSpaceLaneClickSpaceID": lastSpaceLaneClickSpaceID ?? NSNull(),
             "lastAppShelfScrollSyncedAppGroupIndex": lastAppShelfScrollSyncedAppGroupIndex ?? NSNull(),
@@ -483,13 +1204,19 @@
             "appShelfMinIconSize": Double(AppShelfMetrics.minIconSize),
             "appShelfItems": appShelfItemReports(),
             "waterfallFrame": dictionary(from: waterfallLayer.frame),
+            "waterfallViewMode": waterfallViewMode.rawValue,
             "waterfallContentWidth": Double(waterfallContentWidth),
             "waterfallVisibleWidth": Double(waterfallLayer.bounds.width),
             "waterfallScrollOffset": Double(waterfallScrollOffset),
             "waterfallMaxScrollOffset": Double(waterfallMaxScrollOffset),
+            "horizontalMasonryContentHeight": Double(horizontalMasonryContentHeight),
+            "horizontalMasonryScrollOffset": Double(horizontalMasonryScrollOffset),
+            "horizontalMasonryMaxScrollOffset": Double(horizontalMasonryMaxScrollOffset),
+            "horizontalMasonryScrollable": horizontalMasonryMaxScrollOffset > 0,
             "waterfallAlignmentMinScrollOffset": Double(waterfallAlignmentScrollRange.lowerBound),
             "waterfallAlignmentMaxScrollOffset": Double(waterfallAlignmentScrollRange.upperBound),
-            "waterfallScrollable": waterfallAlignmentScrollable,
+            "waterfallScrollable": waterfallMaxScrollOffset > 0,
+            "waterfallAlignmentScrollable": waterfallAlignmentScrollable,
             "waterfallColumnCount": waterfallColumns.count,
             "waterfallColumnNames": waterfallColumns.map(\.column.app.name),
             "waterfallClipsToBounds": waterfallLayer.masksToBounds,
@@ -498,6 +1225,10 @@
             "waterfallAlignmentTolerance": Double(WaterfallAlignmentMetrics.tolerance),
             "waterfallAlignmentAnimationDurationMilliseconds": Double(WaterfallAlignmentMetrics.animationDuration * 1_000),
             "waterfallAlignmentAnimationTimingName": "easeOut",
+            "projectionTransitionMovedLayerCount": lastProjectionTransitionMovedLayerCount,
+            "projectionTransitionFadeInLayerCount": lastProjectionTransitionFadeInLayerCount,
+            "projectionTransitionFadeOutLayerCount": lastProjectionTransitionFadeOutLayerCount,
+            "projectionTransitionDurationMilliseconds": lastProjectionTransitionDurationMilliseconds,
             "reduceMotionEffective": NSWorkspace.shared.accessibilityDisplayShouldReduceMotion,
             "selectedAppGroupIndex": effectiveSelection?.appGroupIndex ?? NSNull(),
             "selectedWindowIndex": effectiveSelection?.windowIndex ?? NSNull(),
@@ -512,6 +1243,20 @@
             "hoveredAppGroupIndex": effectiveHoveredAppGroupIndex ?? NSNull(),
             "hoveredWindowID": hoveredWindowID ?? NSNull(),
             "hoveredSpaceID": hoveredSpaceID ?? NSNull(),
+            "hoveredCloseTargetKind": hoveredCloseTarget?.kindDescription ?? NSNull(),
+            "pendingCloseTargetKind": pendingCloseTarget?.kindDescription ?? NSNull(),
+            "pendingCloseOptOut": pendingCloseOptOut,
+            "closeConfirmationRequired": closeConfirmationRequired,
+            "closeConfirmationVisible": !closeConfirmationLayers.containerLayer.isHidden,
+            "closeConfirmationFrame": dictionary(from: closeConfirmationLayers.containerLayer.frame),
+            "closeConfirmationArrowEdge": closeConfirmationArrowEdge?.rawValue ?? NSNull(),
+            "closeFeedbackVisible": closeFeedback != nil && !closeFeedbackLayer.isHidden,
+            "closeFeedbackKind": closeFeedback?.kind.rawValue ?? NSNull(),
+            "closeFeedbackMessage": closeFeedback?.message ?? NSNull(),
+            "closeFeedbackTargetKind": closeFeedback?.targetKind ?? NSNull(),
+            "closeFeedbackAppGroupIndex": closeFeedback?.appGroupIndex ?? NSNull(),
+            "closeFeedbackWindowID": closeFeedback?.windowID ?? NSNull(),
+            "closeFeedbackFrame": dictionary(from: closeFeedbackLayer.frame),
             "mouseCommandsApplied": mouseCommandsApplied,
             "lastMouseCommand": lastMouseCommand ?? NSNull(),
             "lastClickedAppGroupIndex": lastClickedAppGroupIndex ?? NSNull(),
@@ -579,8 +1324,13 @@
             recordKeyboardCommand("enter")
             commitCurrentSelection()
         case "tab":
-            tabIgnoredCount += 1
-            recordKeyboardCommand("tabIgnored")
+            if isHorizontalMasonryMode {
+                recordKeyboardCommand("tab")
+                moveSelection(.right)
+            } else {
+                tabIgnoredCount += 1
+                recordKeyboardCommand("tabIgnored")
+            }
         default:
             recordKeyboardCommand("unknown:\(command)")
         }
@@ -613,6 +1363,20 @@
             }
             recordMouseCommand("click-app:\(appGroupIndex)")
             clickAppShelfItem(appGroupIndex: appGroupIndex)
+        case "hover-app-close" where parts.count == 2:
+            guard let appGroupIndex = Int(parts[1]) else {
+                recordMouseCommand("invalid:\(command)")
+                return
+            }
+            recordMouseCommand("hover-app-close:\(appGroupIndex)")
+            hoverAppCloseButton(appGroupIndex)
+        case "click-app-close" where parts.count == 2:
+            guard let appGroupIndex = Int(parts[1]) else {
+                recordMouseCommand("invalid:\(command)")
+                return
+            }
+            recordMouseCommand("click-app-close:\(appGroupIndex)")
+            clickAppCloseButton(appGroupIndex)
         case "scroll-app-shelf" where parts.count == 2:
             guard let targetOffset = Double(parts[1]) else {
                 recordMouseCommand("invalid:\(command)")
@@ -627,7 +1391,7 @@
             }
             recordMouseCommand("hover-space:\(spaceID)")
             if let segment = spaceLaneSegment(spaceID: spaceID) {
-                hoverSpaceLaneSegment(segment)
+                hoverSpaceLaneSegment(segment, source: .debug)
             }
         case "click-space" where parts.count == 2:
             guard let spaceID = UInt64(parts[1]) else {
@@ -636,8 +1400,30 @@
             }
             recordMouseCommand("click-space:\(spaceID)")
             if let segment = spaceLaneSegment(spaceID: spaceID) {
-                clickSpaceLaneSegment(segment)
+                clickSpaceLaneSegment(segment, clickCount: 1)
             }
+        case "double-click-space" where parts.count == 2:
+            guard let spaceID = UInt64(parts[1]) else {
+                recordMouseCommand("invalid:\(command)")
+                return
+            }
+            recordMouseCommand("double-click-space:\(spaceID)")
+            if let segment = spaceLaneSegment(spaceID: spaceID) {
+                clickSpaceLaneSegment(segment, clickCount: 1)
+                clickSpaceLaneSegment(segment, clickCount: 2)
+            }
+        case "click-background":
+            recordMouseCommand("click-background")
+            _ = onBackgroundClick?()
+        case "hover-view-toggle":
+            recordMouseCommand("hover-view-toggle")
+            suppressViewModeToggleHoverPreview = false
+            isViewModeToggleButtonHovered = true
+            hoveredCloseTarget = nil
+            setHoverTarget(.none, source: .debug)
+        case "click-view-toggle", "click-settings":
+            recordMouseCommand("click-view-toggle")
+            clickViewModeToggleButton(source: "debug")
         case "hover-card" where parts.count == 3:
             guard let appGroupIndex = Int(parts[1]), let windowIndex = Int(parts[2]) else {
                 recordMouseCommand("invalid:\(command)")
@@ -645,7 +1431,7 @@
             }
             recordMouseCommand("hover-card:\(appGroupIndex):\(windowIndex)")
             if let card = waterfallCard(appGroupIndex: appGroupIndex, windowIndex: windowIndex) {
-                hoverWindowCard(card)
+                hoverWindowCard(card, source: .debug)
             }
         case "click-card" where parts.count == 3:
             guard let appGroupIndex = Int(parts[1]), let windowIndex = Int(parts[2]) else {
@@ -656,6 +1442,38 @@
             if let card = waterfallCard(appGroupIndex: appGroupIndex, windowIndex: windowIndex) {
                 clickWindowCard(card)
             }
+        case "click-card-id" where parts.count == 2:
+            guard let windowID = UInt32(parts[1]) else {
+                recordMouseCommand("invalid:\(command)")
+                return
+            }
+            recordMouseCommand("click-card-id:\(windowID)")
+            if let card = waterfallCard(windowID: windowID) {
+                clickWindowCard(card)
+            }
+        case "hover-card-close" where parts.count == 3:
+            guard let appGroupIndex = Int(parts[1]), let windowIndex = Int(parts[2]) else {
+                recordMouseCommand("invalid:\(command)")
+                return
+            }
+            recordMouseCommand("hover-card-close:\(appGroupIndex):\(windowIndex)")
+            hoverCardCloseButton(appGroupIndex: appGroupIndex, windowIndex: windowIndex)
+        case "click-card-close" where parts.count == 3:
+            guard let appGroupIndex = Int(parts[1]), let windowIndex = Int(parts[2]) else {
+                recordMouseCommand("invalid:\(command)")
+                return
+            }
+            recordMouseCommand("click-card-close:\(appGroupIndex):\(windowIndex)")
+            clickCardCloseButton(appGroupIndex: appGroupIndex, windowIndex: windowIndex)
+        case "toggle-close-optout":
+            recordMouseCommand("toggle-close-optout")
+            toggleCloseConfirmationOptOut()
+        case "confirm-close":
+            recordMouseCommand("confirm-close")
+            confirmPendingClose()
+        case "cancel-close":
+            recordMouseCommand("cancel-close")
+            cancelPendingClose()
         default:
             recordMouseCommand("unknown:\(command)")
         }
@@ -674,41 +1492,75 @@
     }
 
     private func hoverAppGroup(_ appGroupIndex: Int) {
-        hoveredSpaceLaneID = nil
         updateHoverState(
             appGroupIndex: appGroupIndex,
             windowID: nil,
             spaceID: nil,
-            alignsWaterfallWithAppShelf: true
+            alignsWaterfallWithAppShelf: true,
+            source: .debug
         )
     }
 
-    private func hoverWindowCard(_ card: WaterfallCardLayers) {
-        hoveredSpaceLaneID = nil
+    private func hoverAppCloseButton(_ appGroupIndex: Int) {
+        hoverAppGroup(appGroupIndex)
+        hoveredCloseTarget = .app(appGroupIndex: appGroupIndex)
+        needsLayout = true
+    }
+
+    private func clickAppCloseButton(_ appGroupIndex: Int) {
+        hoverAppCloseButton(appGroupIndex)
+        beginCloseConfirmation(for: .app(appGroupIndex: appGroupIndex))
+    }
+
+    private func hoverWindowCard(_ card: WaterfallCardLayers, source: HoverTargetSource = .event) {
         updateHoverState(
             appGroupIndex: card.item.appGroupIndex,
             windowID: card.item.window.id,
-            spaceID: card.item.primarySpaceID
+            spaceID: card.item.primarySpaceID,
+            source: source
         )
     }
 
-    private func hoverSpaceLaneSegment(_ segment: SpaceLaneSegmentLayers) {
-        focusSpace(segment.space.id, persistent: false)
+    private func hoverCardCloseButton(appGroupIndex: Int, windowIndex: Int) {
+        guard let card = waterfallCard(appGroupIndex: appGroupIndex, windowIndex: windowIndex) else { return }
+        hoverWindowCard(card, source: .debug)
+        hoveredCloseTarget = .window(
+            appGroupIndex: appGroupIndex,
+            windowIndex: windowIndex,
+            windowID: card.item.window.id
+        )
+        needsLayout = true
     }
 
-    private func clickSpaceLaneSegment(_ segment: SpaceLaneSegmentLayers) {
+    private func clickCardCloseButton(appGroupIndex: Int, windowIndex: Int) {
+        guard let card = waterfallCard(appGroupIndex: appGroupIndex, windowIndex: windowIndex) else { return }
+        hoverCardCloseButton(appGroupIndex: appGroupIndex, windowIndex: windowIndex)
+        beginCloseConfirmation(
+            for: .window(
+                appGroupIndex: appGroupIndex,
+                windowIndex: windowIndex,
+                windowID: card.item.window.id
+            )
+        )
+    }
+
+    private func hoverSpaceLaneSegment(_ segment: SpaceLaneSegmentLayers, source: HoverTargetSource = .event) {
+        focusSpace(segment.space.id, persistent: false, source: source)
+    }
+
+    private func clickSpaceLaneSegment(_ segment: SpaceLaneSegmentLayers, clickCount: Int = 1) {
         DevelopmentDiagnostics.log("quickSwitch.view.clickSpaceLane", [
             "spaceID": segment.space.id,
-            "label": segment.space.label
+            "label": segment.space.label,
+            "clickCount": clickCount
         ])
-        focusSpace(segment.space.id, persistent: true)
+        lastSpaceLaneClickSpaceID = segment.space.id
+        onSpaceLaneClick?(segment.space.id, clickCount)
+        lastSpaceLaneClickSpaceID = segment.space.id
     }
 
-    private func focusSpace(_ spaceID: UInt64, persistent: Bool) {
-        hoveredAppGroupIndex = nil
-        hoveredWindowID = nil
-        hoveredSpaceID = spaceID
-        hoveredSpaceLaneID = spaceID
+    private func focusSpace(_ spaceID: UInt64, persistent: Bool, source: HoverTargetSource = .event) {
+        setHoverTarget(.space(spaceID), source: source)
         if persistent {
             focusedSpaceID = spaceID
             lastSpaceLaneClickSpaceID = spaceID
@@ -752,12 +1604,14 @@
             columnSelectionHistory[nextSelection.appGroupIndex] = nextSelection.windowIndex
             lastAppShelfClickChangedSelection = previousSelection != nextSelection
             ensureWaterfallSelectionVisible(nextSelection, horizontalIntent: .alignWithAppShelf(animated: true))
+            updateHoverState(appGroupIndex: appGroupIndex, windowID: nil, spaceID: nil)
+            commitWindowCard(firstCard, trigger: "appShelf")
         } else {
             lastAppShelfClickChangedSelection = false
             ensureWaterfallColumnVisible(column)
+            updateHoverState(appGroupIndex: appGroupIndex, windowID: nil, spaceID: nil)
+            needsLayout = true
         }
-        updateHoverState(appGroupIndex: appGroupIndex, windowID: nil, spaceID: nil)
-        needsLayout = true
     }
 
     private func scrollAppShelf(to targetOffset: CGFloat) {
@@ -799,12 +1653,17 @@
 
     private func clickWindowCard(_ card: WaterfallCardLayers) {
         hoverWindowCard(card)
+        commitWindowCard(card, trigger: "windowCard")
+    }
+
+    private func commitWindowCard(_ card: WaterfallCardLayers, trigger: String) {
         let selection = QuickSwitchSelection(
             appGroupIndex: card.item.appGroupIndex,
             windowIndex: card.item.windowIndex,
             windowID: card.item.window.id
         )
-        DevelopmentDiagnostics.log("quickSwitch.view.clickWindowCard", [
+        DevelopmentDiagnostics.log("quickSwitch.view.commitMouseWindow", [
+            "trigger": trigger,
             "appGroupIndex": selection.appGroupIndex,
             "windowIndex": selection.windowIndex,
             "windowID": selection.windowID,
@@ -830,28 +1689,76 @@
         appGroupIndex: Int?,
         windowID: UInt32?,
         spaceID: UInt64?,
-        alignsWaterfallWithAppShelf: Bool = false
+        alignsWaterfallWithAppShelf: Bool = false,
+        source: HoverTargetSource = .event
     ) {
-        guard hoveredAppGroupIndex != appGroupIndex
-            || hoveredWindowID != windowID
-            || hoveredSpaceID != spaceID
-        else {
-            if alignsWaterfallWithAppShelf, let appGroupIndex {
-                alignWaterfallColumnWithAppShelfIcon(appGroupIndex: appGroupIndex, animated: true)
-            }
-            return
+        let target: HoverTarget
+        if let appGroupIndex, let windowID {
+            target = .window(appGroupIndex: appGroupIndex, windowID: windowID, spaceID: spaceID)
+        } else if let appGroupIndex {
+            target = .app(appGroupIndex)
+        } else {
+            target = .none
         }
 
-        hoveredAppGroupIndex = appGroupIndex
-        hoveredWindowID = windowID
-        hoveredSpaceID = spaceID
-        if alignsWaterfallWithAppShelf, let appGroupIndex {
+        setHoverTarget(target, source: source, alignsWaterfallWithAppShelf: alignsWaterfallWithAppShelf)
+    }
+
+    private func refreshHoverTarget(at windowLocation: CGPoint) {
+        guard debugHoveredAppGroupIndex == nil else { return }
+        let target = resolveHoverTarget(at: windowLocation)
+        setHoverTarget(target, alignsWaterfallWithAppShelf: target.shouldAlignWaterfallWithAppShelf)
+    }
+
+    private func resolveHoverTarget(at windowLocation: CGPoint) -> HoverTarget {
+        if let segment = spaceLaneSegment(at: windowLocation) {
+            return .space(segment.space.id)
+        }
+
+        if let card = waterfallCard(at: windowLocation) {
+            return .window(
+                appGroupIndex: card.item.appGroupIndex,
+                windowID: card.item.window.id,
+                spaceID: card.item.primarySpaceID
+            )
+        }
+
+        if let item = appShelfItem(at: windowLocation) {
+            return .app(item.item.appGroupIndex)
+        }
+
+        return .none
+    }
+
+    private func setHoverTarget(
+        _ target: HoverTarget,
+        source: HoverTargetSource = .event,
+        alignsWaterfallWithAppShelf: Bool = false
+    ) {
+        let previousTarget = hoverTarget
+        let previousSource = hoverTargetSource
+        hoverTarget = target
+        hoverTargetSource = source
+
+        hoveredAppGroupIndex = target.appGroupIndex
+        hoveredWindowID = target.windowID
+        hoveredSpaceID = target.spaceID
+        hoveredSpaceLaneID = target.spaceLaneID
+
+        if alignsWaterfallWithAppShelf, let appGroupIndex = target.appGroupIndex {
             alignWaterfallColumnWithAppShelfIcon(appGroupIndex: appGroupIndex, animated: true)
         }
+
+        guard previousTarget != target || previousSource != source else { return }
         needsLayout = true
     }
 
     private func moveSelection(_ direction: QuickSwitchKeyboardDirection) {
+        if isHorizontalMasonryMode {
+            moveHorizontalMasonrySelection(direction)
+            return
+        }
+
         guard let currentViewModel,
               let snapshot = snapshotForFocus(from: currentViewModel),
               let current = currentSelection ?? currentViewModel.initialSelection,
@@ -881,6 +1788,113 @@
             "windowID": next.windowID
         ])
         needsLayout = true
+    }
+
+    private func moveHorizontalMasonrySelection(_ direction: QuickSwitchKeyboardDirection) {
+        guard let current = currentSelection ?? currentViewModel?.initialSelection,
+              let next = nextHorizontalMasonrySelection(from: current, direction: direction)
+        else {
+            DevelopmentDiagnostics.log("quickSwitch.view.moveHorizontalMasonrySelection.blocked", [
+                "direction": String(describing: direction),
+                "hasSelection": (currentSelection ?? currentViewModel?.initialSelection) != nil
+            ])
+            return
+        }
+
+        columnSelectionHistory[current.appGroupIndex] = current.windowIndex
+        currentSelection = next
+        columnSelectionHistory[next.appGroupIndex] = next.windowIndex
+        ensureCurrentSelectionVisible(horizontalIntent: .alignWithAppShelf(animated: true))
+        DevelopmentDiagnostics.log("quickSwitch.view.moveHorizontalMasonrySelection", [
+            "direction": String(describing: direction),
+            "appGroupIndex": next.appGroupIndex,
+            "windowIndex": next.windowIndex,
+            "windowID": next.windowID
+        ])
+        needsLayout = true
+    }
+
+    private func nextHorizontalMasonrySelection(
+        from current: QuickSwitchSelection,
+        direction: QuickSwitchKeyboardDirection
+    ) -> QuickSwitchSelection? {
+        layoutSubtreeIfNeeded()
+
+        let cards = horizontalMasonryCardsInPlacementOrder()
+        guard let currentIndex = cards.firstIndex(where: { $0.item.window.id == current.windowID }) else {
+            return cards.first.map(selectionForCard)
+        }
+
+        switch direction {
+        case .right:
+            return selectionForCard(cards[(currentIndex + 1) % cards.count])
+        case .left:
+            return selectionForCard(cards[(currentIndex - 1 + cards.count) % cards.count])
+        case .up:
+            return nearestHorizontalMasonrySelection(from: cards[currentIndex], direction: .up)
+                ?? selectionForCard(cards.first ?? cards[currentIndex])
+        case .down:
+            return nearestHorizontalMasonrySelection(from: cards[currentIndex], direction: .down)
+                ?? selectionForCard(cards.last ?? cards[currentIndex])
+        }
+    }
+
+    private func nearestHorizontalMasonrySelection(
+        from currentCard: WaterfallCardLayers,
+        direction: QuickSwitchKeyboardDirection
+    ) -> QuickSwitchSelection? {
+        let currentFrame = currentCard.containerLayer.frame
+        let candidates = horizontalMasonryCardsInPlacementOrder().filter { card in
+            guard card.item.window.id != currentCard.item.window.id else { return false }
+            switch direction {
+            case .up:
+                return card.containerLayer.frame.minY >= currentFrame.maxY - 0.5
+            case .down:
+                return card.containerLayer.frame.maxY <= currentFrame.minY + 0.5
+            case .left, .right:
+                return false
+            }
+        }
+
+        let best = candidates.min { lhs, rhs in
+            let lhsFrame = lhs.containerLayer.frame
+            let rhsFrame = rhs.containerLayer.frame
+            let lhsPrimaryDistance = direction == .up
+                ? lhsFrame.minY - currentFrame.maxY
+                : currentFrame.minY - lhsFrame.maxY
+            let rhsPrimaryDistance = direction == .up
+                ? rhsFrame.minY - currentFrame.maxY
+                : currentFrame.minY - rhsFrame.maxY
+            if abs(lhsPrimaryDistance - rhsPrimaryDistance) > 0.5 {
+                return lhsPrimaryDistance < rhsPrimaryDistance
+            }
+
+            let lhsHorizontalDistance = abs(lhsFrame.midX - currentFrame.midX)
+            let rhsHorizontalDistance = abs(rhsFrame.midX - currentFrame.midX)
+            if abs(lhsHorizontalDistance - rhsHorizontalDistance) > 0.5 {
+                return lhsHorizontalDistance < rhsHorizontalDistance
+            }
+
+            return lhs.item.globalIndex < rhs.item.globalIndex
+        }
+
+        return best.map(selectionForCard)
+    }
+
+    private func horizontalMasonryCardsInPlacementOrder() -> [WaterfallCardLayers] {
+        waterfallColumns
+            .sorted { $0.column.appGroupIndex < $1.column.appGroupIndex }
+            .flatMap { column in
+                column.cards.sorted { $0.item.windowIndex < $1.item.windowIndex }
+            }
+    }
+
+    private func selectionForCard(_ card: WaterfallCardLayers) -> QuickSwitchSelection {
+        QuickSwitchSelection(
+            appGroupIndex: card.item.appGroupIndex,
+            windowIndex: card.item.windowIndex,
+            windowID: card.item.window.id
+        )
     }
 
     private func commitCurrentSelection() {
@@ -940,9 +1954,24 @@
         _ selection: QuickSwitchSelection,
         horizontalIntent: WaterfallHorizontalIntent = .reveal
     ) {
+        if isHorizontalMasonryMode {
+            switch horizontalIntent {
+            case .reveal:
+                ensureHorizontalMasonrySelectionVisible(selection, animated: false)
+            case .alignWithAppShelf(let animated):
+                ensureHorizontalMasonrySelectionVisible(selection, animated: animated)
+            }
+            return
+        }
+
         guard
             let column = waterfallColumns.first(where: { $0.column.appGroupIndex == selection.appGroupIndex })
         else {
+            return
+        }
+
+        if waterfallShouldKeepFilteredColumnsCentered {
+            ensureWaterfallCardVisibleVertically(selection)
             return
         }
 
@@ -956,11 +1985,16 @@
     }
 
     private func ensureWaterfallCardVisibleVertically(_ selection: QuickSwitchSelection) {
+        guard !isHorizontalMasonryMode else {
+            ensureHorizontalMasonrySelectionVisible(selection, animated: false)
+            return
+        }
+
         let visibleHeight = max(
             1,
             waterfallLayer.bounds.height
                 - WaterfallMetrics.headerHeight
-                - WaterfallMetrics.columnPadding * 2
+                - WaterfallMetrics.columnVerticalPadding * 2
         )
         let cardStride = WaterfallMetrics.cardHeight + WaterfallMetrics.cardGap
         let cardStart = CGFloat(selection.windowIndex) * cardStride
@@ -983,6 +2017,11 @@
     }
 
     private func alignWaterfallColumnWithAppShelfIcon(appGroupIndex: Int, animated: Bool) {
+        if isHorizontalMasonryMode {
+            ensureHorizontalMasonryAppVisible(appGroupIndex, animated: animated)
+            return
+        }
+
         guard
             let item = appShelfItems.first(where: { $0.item.appGroupIndex == appGroupIndex }),
             let column = waterfallColumns.first(where: { $0.column.appGroupIndex == appGroupIndex })
@@ -1009,6 +2048,11 @@
     }
 
     private func ensureWaterfallColumnVisible(_ appGroupIndex: Int) {
+        if isHorizontalMasonryMode {
+            ensureHorizontalMasonryAppVisible(appGroupIndex, animated: false)
+            return
+        }
+
         guard let column = waterfallColumns.first(where: { $0.column.appGroupIndex == appGroupIndex }) else {
             return
         }
@@ -1017,18 +2061,31 @@
     }
 
     private func ensureWaterfallColumnVisible(_ column: WaterfallColumnLayers) {
+        if isHorizontalMasonryMode {
+            ensureHorizontalMasonryAppVisible(column.column.appGroupIndex, animated: false)
+            return
+        }
+
         waterfallScrollOffset = clampedWaterfallOffset(
             scrollOffset(
                 makingVisible: column.containerLayer.frame,
                 currentOffset: waterfallScrollOffset,
                 visibleWidth: waterfallLayer.bounds.width,
                 maxOffset: waterfallMaxScrollOffset,
-                inset: WaterfallMetrics.revealPadding
+                inset: WaterfallMetrics.horizontalRevealPadding
             )
         )
     }
 
     private var waterfallAlignmentScrollRange: ClosedRange<CGFloat> {
+        if isHorizontalMasonryMode {
+            return 0...0
+        }
+
+        if waterfallShouldKeepFilteredColumnsCentered {
+            return 0...0
+        }
+
         var minimumOffset: CGFloat = 0
         var maximumOffset = waterfallMaxScrollOffset
 
@@ -1053,6 +2110,10 @@
     private func clampedWaterfallAlignmentOffset(_ offset: CGFloat) -> CGFloat {
         let range = waterfallAlignmentScrollRange
         return min(max(range.lowerBound, offset), range.upperBound)
+    }
+
+    private var waterfallShouldKeepFilteredColumnsCentered: Bool {
+        currentViewModel?.lockedSpaceID != nil && waterfallMaxScrollOffset <= 0.5
     }
 
     private func setWaterfallScrollOffset(_ offset: CGFloat, animated: Bool) {
@@ -1087,6 +2148,80 @@
         animation.timingFunction = CAMediaTimingFunction(name: WaterfallAlignmentMetrics.animationTimingName)
         animation.isRemovedOnCompletion = true
         waterfallContentLayer.add(animation, forKey: "waterfallColumnAlignment")
+    }
+
+    private func ensureHorizontalMasonrySelectionVisible(
+        _ selection: QuickSwitchSelection,
+        animated: Bool
+    ) {
+        guard let card = waterfallCard(
+            appGroupIndex: selection.appGroupIndex,
+            windowIndex: selection.windowIndex
+        ) else {
+            return
+        }
+
+        let visibleFrame = card.containerLayer.frame.offsetBy(
+            dx: 0,
+            dy: waterfallContentLayer.frame.minY
+        )
+        let visibleHeight = waterfallLayer.bounds.height
+        let padding = WaterfallMetrics.revealPadding
+        var nextOffset = horizontalMasonryScrollOffset
+
+        if visibleFrame.maxY > visibleHeight - padding {
+            nextOffset -= visibleFrame.maxY - (visibleHeight - padding)
+        } else if visibleFrame.minY < padding {
+            nextOffset += padding - visibleFrame.minY
+        }
+
+        setHorizontalMasonryScrollOffset(nextOffset, animated: animated)
+    }
+
+    private func ensureHorizontalMasonryAppVisible(_ appGroupIndex: Int, animated: Bool) {
+        guard let firstCard = waterfallColumns
+            .first(where: { $0.column.appGroupIndex == appGroupIndex })?
+            .cards
+            .sorted(by: { $0.item.windowIndex < $1.item.windowIndex })
+            .first
+        else {
+            return
+        }
+
+        let cardTopDistance = horizontalMasonryContentHeight - firstCard.containerLayer.frame.maxY
+        setHorizontalMasonryScrollOffset(
+            cardTopDistance - WaterfallMetrics.revealPadding,
+            animated: animated
+        )
+    }
+
+    private func setHorizontalMasonryScrollOffset(_ offset: CGFloat, animated: Bool) {
+        let nextOffset = clampedHorizontalMasonryOffset(offset)
+        let previousPositionY = waterfallContentLayer.presentation()?.position.y
+            ?? waterfallContentLayer.position.y
+
+        horizontalMasonryScrollOffset = nextOffset
+        CATransaction.begin()
+        CATransaction.setDisableActions(true)
+        waterfallContentLayer.frame = horizontalMasonryContentFrame()
+        CATransaction.commit()
+
+        let nextPositionY = waterfallContentLayer.position.y
+        guard animated,
+              !NSWorkspace.shared.accessibilityDisplayShouldReduceMotion,
+              abs(previousPositionY - nextPositionY) > 0.5
+        else {
+            waterfallContentLayer.removeAnimation(forKey: "horizontalMasonryAlignment")
+            return
+        }
+
+        let animation = CABasicAnimation(keyPath: "position.y")
+        animation.fromValue = previousPositionY
+        animation.toValue = nextPositionY
+        animation.duration = WaterfallAlignmentMetrics.animationDuration
+        animation.timingFunction = CAMediaTimingFunction(name: WaterfallAlignmentMetrics.animationTimingName)
+        animation.isRemovedOnCompletion = true
+        waterfallContentLayer.add(animation, forKey: "horizontalMasonryAlignment")
     }
 
     private func scrollOffset(
@@ -1162,35 +2297,54 @@
         value ?? NSNull()
     }
 
+    private func setupBackdropBlurView() {
+        backdropBlurView.material = .fullScreenUI
+        backdropBlurView.blendingMode = .behindWindow
+        backdropBlurView.state = .active
+        backdropBlurView.isEmphasized = false
+        backdropBlurView.frame = bounds
+        backdropBlurView.autoresizingMask = [.width, .height]
+        addSubview(backdropBlurView, positioned: .below, relativeTo: nil)
+    }
+
+    private func setupLayerHostView() {
+        layerHostView.wantsLayer = true
+        layerHostView.frame = bounds
+        layerHostView.autoresizingMask = [.width, .height]
+        layerHostView.layer?.masksToBounds = true
+        layerHostView.layer?.backgroundColor = NSColor.clear.cgColor
+        addSubview(layerHostView, positioned: .above, relativeTo: backdropBlurView)
+    }
+
     private func setupLayers() {
-        guard let rootLayer = layer else { return }
+        guard let rootLayer = layerHostView.layer else { return }
 
         rootLayer.masksToBounds = true
         backgroundLayer.colors = [
-            NSColor.windowBackgroundColor.withAlphaComponent(0.72).cgColor,
-            NSColor.controlBackgroundColor.withAlphaComponent(0.62).cgColor
+            NSColor.windowBackgroundColor.withAlphaComponent(0.58).cgColor,
+            NSColor.controlBackgroundColor.withAlphaComponent(0.48).cgColor
         ]
         backgroundLayer.startPoint = CGPoint(x: 0.5, y: 1.0)
         backgroundLayer.endPoint = CGPoint(x: 0.5, y: 0.0)
         rootLayer.addSublayer(backgroundLayer)
 
-        glassLayer.cornerRadius = 24
-        glassLayer.backgroundColor = NSColor.windowBackgroundColor.withAlphaComponent(0.72).cgColor
-        glassLayer.borderColor = NSColor.separatorColor.withAlphaComponent(0.35).cgColor
-        glassLayer.borderWidth = 1
-        glassLayer.shadowColor = NSColor.black.cgColor
-        glassLayer.shadowOpacity = 0.16
-        glassLayer.shadowRadius = 24
-        glassLayer.shadowOffset = CGSize(width: 0, height: -8)
+        safeAreaFillLayer.backgroundColor = NSColor.black.cgColor
+        rootLayer.addSublayer(safeAreaFillLayer)
+
+        glassLayer.cornerRadius = 0
+        glassLayer.backgroundColor = NSColor.clear.cgColor
+        glassLayer.borderColor = NSColor.clear.cgColor
+        glassLayer.borderWidth = 0
+        glassLayer.shadowOpacity = 0
         rootLayer.addSublayer(glassLayer)
 
-        laneLayer.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.50).cgColor
-        laneLayer.cornerRadius = 16
+        laneLayer.backgroundColor = NSColor.clear.cgColor
+        laneLayer.cornerRadius = 0
         laneLayer.masksToBounds = true
         glassLayer.addSublayer(laneLayer)
         laneLayer.addSublayer(spaceLaneContentLayer)
 
-        shelfLayer.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.42).cgColor
+        shelfLayer.backgroundColor = NSColor.clear.cgColor
         shelfLayer.cornerRadius = 16
         shelfLayer.masksToBounds = true
         glassLayer.addSublayer(shelfLayer)
@@ -1200,6 +2354,37 @@
         waterfallLayer.masksToBounds = true
         glassLayer.addSublayer(waterfallLayer)
         waterfallLayer.addSublayer(waterfallContentLayer)
+
+        closeConfirmationLayers.containerLayer.isHidden = true
+        glassLayer.addSublayer(closeConfirmationLayers.containerLayer)
+
+        closeFeedbackLayer.isHidden = true
+        closeFeedbackLayer.opacity = 0
+        closeFeedbackLayer.cornerRadius = 11
+        closeFeedbackLayer.borderWidth = 1
+        closeFeedbackLayer.masksToBounds = false
+        closeFeedbackLayer.shadowColor = NSColor.black.cgColor
+        closeFeedbackLayer.shadowOpacity = 0.14
+        closeFeedbackLayer.shadowRadius = 16
+        closeFeedbackLayer.shadowOffset = CGSize(width: 0, height: -5)
+        closeFeedbackLayer.zPosition = 190
+        closeFeedbackTextLayer.contentsScale = backingScaleFactor
+        closeFeedbackTextLayer.font = NSFont.systemFont(ofSize: 13, weight: .medium)
+        closeFeedbackTextLayer.fontSize = 13
+        closeFeedbackTextLayer.alignmentMode = .center
+        closeFeedbackTextLayer.truncationMode = .end
+        closeFeedbackLayer.addSublayer(closeFeedbackTextLayer)
+        glassLayer.addSublayer(closeFeedbackLayer)
+
+        viewModeToggleButtonLayer.cornerRadius = 10
+        viewModeToggleButtonLayer.masksToBounds = false
+        viewModeToggleButtonLayer.borderWidth = 1
+        viewModeToggleButtonLayer.shadowColor = NSColor.black.cgColor
+        viewModeToggleButtonLayer.shadowOffset = CGSize(width: 0, height: -2)
+        viewModeToggleButtonLayer.zPosition = 170
+        viewModeToggleIconLayer.contentsScale = backingScaleFactor
+        viewModeToggleButtonLayer.addSublayer(viewModeToggleIconLayer)
+        glassLayer.addSublayer(viewModeToggleButtonLayer)
     }
 
     private func rebuildAppShelfItems() {
@@ -1207,22 +2392,15 @@
             item.containerLayer.removeFromSuperlayer()
         }
 
-        let selectedAppGroupIndex = effectiveSelection?.appGroupIndex
-        appShelfItems = (currentViewModel?.appShelf ?? []).map { item in
+        appShelfItems = (currentViewModel?.appShelf ?? []).enumerated().map { ordinal, item in
             let container = CALayer()
             container.name = item.app.name
 
             let background = CALayer()
             background.cornerRadius = 10
-            background.backgroundColor = (item.appGroupIndex == selectedAppGroupIndex
-                ? NSColor.systemFill.withAlphaComponent(0.16)
-                : NSColor.clear
-            ).cgColor
-            background.borderColor = (item.appGroupIndex == selectedAppGroupIndex
-                ? NSColor.separatorColor.withAlphaComponent(0.36)
-                : NSColor.clear
-            ).cgColor
-            background.borderWidth = item.appGroupIndex == selectedAppGroupIndex ? 1 : 0
+            background.backgroundColor = NSColor.clear.cgColor
+            background.borderColor = NSColor.clear.cgColor
+            background.borderWidth = 0
 
             let icon = CALayer()
             icon.contentsGravity = .resizeAspect
@@ -1230,6 +2408,18 @@
             icon.contents = appIconProvider.icon(for: item.app)
             icon.cornerRadius = 12
             icon.masksToBounds = false
+
+            let indexLabel = makeTextLayer(
+                string: appShelfIndexText(forOrdinal: ordinal),
+                fontSize: AppShelfMetrics.indexFontSize,
+                weight: .regular,
+                color: appShelfIndexColor,
+                alignment: .center
+            )
+            indexLabel.font = appShelfIndexFont(size: AppShelfMetrics.indexFontSize)
+            indexLabel.fontSize = AppShelfMetrics.indexFontSize
+            indexLabel.truncationMode = .end
+            indexLabel.zPosition = 14
 
             let label = makeTextLayer(
                 string: item.app.name,
@@ -1252,21 +2442,26 @@
 
             let selectedIndicator = CALayer()
             selectedIndicator.isHidden = true
+            let closeButton = makeCloseButtonLayers()
 
             container.addSublayer(background)
+            container.addSublayer(indexLabel)
             container.addSublayer(icon)
             container.addSublayer(label)
             container.addSublayer(badge)
+            container.addSublayer(closeButton.containerLayer)
             appShelfContentLayer.addSublayer(container)
 
             return AppShelfItemLayers(
                 item: item,
                 containerLayer: container,
                 backgroundLayer: background,
+                indexLayer: indexLabel,
                 iconLayer: icon,
                 labelLayer: label,
                 badgeLayer: badge,
-                selectedIndicatorLayer: selectedIndicator
+                selectedIndicatorLayer: selectedIndicator,
+                closeButton: closeButton
             )
         }
     }
@@ -1282,18 +2477,19 @@
             container.name = column.app.name
             container.cornerRadius = 14
             container.masksToBounds = true
-            container.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.34).cgColor
-            container.borderColor = NSColor.separatorColor.withAlphaComponent(0.28).cgColor
+            container.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.56).cgColor
+            container.borderColor = NSColor.separatorColor.withAlphaComponent(0.34).cgColor
             container.borderWidth = 1
 
             let header = CALayer()
-            header.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.58).cgColor
+            header.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.68).cgColor
 
             let appName = makeTextLayer(
                 string: column.app.name,
                 fontSize: 13,
                 weight: .semibold,
-                color: .labelColor
+                color: .labelColor,
+                alignment: .center
             )
             let count = makeTextLayer(
                 string: "\(column.windows.count)",
@@ -1319,6 +2515,9 @@
                 thumbnail.masksToBounds = true
                 thumbnail.contents = skeletonThumbnailProvider
                     .withOverlayTitle(window.window.title, for: window.window.app)
+
+                let titleBar = CALayer()
+                titleBar.borderWidth = 0
 
                 let title = makeTextLayer(
                     string: window.window.title.isEmpty ? "Untitled Window" : window.window.title,
@@ -1356,24 +2555,29 @@
                 shine.startPoint = CGPoint(x: 0, y: 1)
                 shine.endPoint = CGPoint(x: 1, y: 0)
                 shine.opacity = 0
+                let closeButton = makeCloseButtonLayers()
 
                 card.addSublayer(thumbnail)
+                card.addSublayer(titleBar)
                 card.addSublayer(appIcon)
                 card.addSublayer(title)
                 card.addSublayer(meta)
                 card.addSublayer(state)
                 card.addSublayer(shine)
+                card.addSublayer(closeButton.containerLayer)
                 container.addSublayer(card)
 
                 return WaterfallCardLayers(
                     item: window,
                     containerLayer: card,
+                    titleBarLayer: titleBar,
                     titleLayer: title,
                     metaLayer: meta,
                     thumbnailLayer: thumbnail,
                     appIconLayer: appIcon,
                     stateLayer: state,
-                    shineLayer: shine
+                    shineLayer: shine,
+                    closeButton: closeButton
                 )
             }
 
@@ -1394,63 +2598,108 @@
     }
 
     private func rebuildSpaceLaneSegments() {
-        for segment in spaceLaneSegments {
-            segment.containerLayer.removeFromSuperlayer()
+        for group in spaceLaneDisplayGroups {
+            group.containerLayer.removeFromSuperlayer()
         }
 
-        let spaces = currentViewModel?.displays.flatMap(\.spaces) ?? []
-        spaceLaneSegments = spaces.map { space in
-            let container = CALayer()
-            container.name = space.label
-            container.cornerRadius = 10
-            container.borderWidth = 1
-            container.borderColor = NSColor.separatorColor.withAlphaComponent(0.34).cgColor
-            container.backgroundColor = spaceColor(for: space).cgColor
-            container.shadowColor = NSColor.black.cgColor
+        var groups: [SpaceLaneDisplayGroupLayers] = []
+        var allSegments: [SpaceLaneSegmentLayers] = []
 
-            let labelLayer = makeTextLayer(
-                string: space.label,
-                fontSize: 15,
-                weight: .semibold,
-                color: .labelColor
-            )
-            let countLayer = makeTextLayer(
-                string: "\(space.windowCount)",
-                fontSize: 12,
-                weight: .medium,
-                color: .secondaryLabelColor,
-                alignment: .center
-            )
-            let appLayer = makeTextLayer(
-                string: appIdentifierText(for: space.appNames),
-                fontSize: 12,
-                weight: .regular,
-                color: .secondaryLabelColor
-            )
-            let windowBlocks = makeWindowBlocks(count: min(space.windowCount, 5), space: space)
-            let fullscreenMarkerLayer = makeFullscreenMarkerLayer(for: space)
+        for display in currentViewModel?.displays ?? [] {
+            let groupContainer = CALayer()
+            groupContainer.name = display.displayLabel
+            groupContainer.cornerRadius = 14
+            groupContainer.masksToBounds = false
+            groupContainer.borderWidth = 0
+            groupContainer.borderColor = NSColor.clear.cgColor
+            groupContainer.backgroundColor = NSColor.windowBackgroundColor.cgColor
+            groupContainer.shadowColor = NSColor.black.cgColor
+            groupContainer.shadowOpacity = 0
+            groupContainer.shadowRadius = 0
+            groupContainer.shadowOffset = .zero
 
-            container.addSublayer(labelLayer)
-            container.addSublayer(countLayer)
-            container.addSublayer(appLayer)
-            if let fullscreenMarkerLayer {
-                container.addSublayer(fullscreenMarkerLayer)
+            let segments = display.spaces.map { space in
+                let container = CAGradientLayer()
+                container.name = space.label
+                container.cornerRadius = 10
+                container.borderWidth = 1
+                container.borderColor = NSColor.separatorColor.withAlphaComponent(0.34).cgColor
+                container.backgroundColor = NSColor.clear.cgColor
+                container.startPoint = CGPoint(x: 0.5, y: 1.0)
+                container.endPoint = CGPoint(x: 0.5, y: 0.0)
+                container.shadowColor = NSColor.black.cgColor
+
+                let labelLayer = makeTextLayer(
+                    string: space.label,
+                    fontSize: 15,
+                    weight: .semibold,
+                    color: .labelColor
+                )
+                let countLayer = makeTextLayer(
+                    string: "\(space.windowCount)",
+                    fontSize: 12,
+                    weight: .medium,
+                    color: .secondaryLabelColor,
+                    alignment: .center
+                )
+                let appLayer = makeTextLayer(
+                    string: appIdentifierText(for: space),
+                    fontSize: 12,
+                    weight: space.type == .fullscreen ? .medium : .regular,
+                    color: space.type == .fullscreen ? .labelColor : .secondaryLabelColor,
+                    alignment: space.type == .fullscreen ? .center : .left
+                )
+                let splitAppLayers = splitViewAppNames(for: space).map { name in
+                    makeTextLayer(
+                        string: name,
+                        fontSize: 12,
+                        weight: .medium,
+                        color: .labelColor,
+                        alignment: .center
+                    )
+                }
+                let windowBlocks = space.type == .fullscreen
+                    ? []
+                    : makeWindowBlocks(count: min(space.windowCount, 5), space: space)
+                let fullscreenMarkerLayer = makeFullscreenMarkerLayer(for: space)
+
+                container.addSublayer(labelLayer)
+                container.addSublayer(countLayer)
+                container.addSublayer(appLayer)
+                if let fullscreenMarkerLayer {
+                    container.addSublayer(fullscreenMarkerLayer)
+                }
+                for splitAppLayer in splitAppLayers {
+                    container.addSublayer(splitAppLayer)
+                }
+                for block in windowBlocks {
+                    container.addSublayer(block)
+                }
+                groupContainer.addSublayer(container)
+
+                return SpaceLaneSegmentLayers(
+                    space: space,
+                    containerLayer: container,
+                    labelLayer: labelLayer,
+                    countLayer: countLayer,
+                    appLayer: appLayer,
+                    splitAppLayers: splitAppLayers,
+                    windowBlocks: windowBlocks,
+                    fullscreenMarkerLayer: fullscreenMarkerLayer
+                )
             }
-            for block in windowBlocks {
-                container.addSublayer(block)
-            }
-            spaceLaneContentLayer.addSublayer(container)
 
-            return SpaceLaneSegmentLayers(
-                space: space,
-                containerLayer: container,
-                labelLayer: labelLayer,
-                countLayer: countLayer,
-                appLayer: appLayer,
-                windowBlocks: windowBlocks,
-                fullscreenMarkerLayer: fullscreenMarkerLayer
-            )
+            spaceLaneContentLayer.addSublayer(groupContainer)
+            groups.append(SpaceLaneDisplayGroupLayers(
+                display: display,
+                containerLayer: groupContainer,
+                segments: segments
+            ))
+            allSegments.append(contentsOf: segments)
         }
+
+        spaceLaneDisplayGroups = groups
+        spaceLaneSegments = allSegments
     }
 
     private func layoutLayers() {
@@ -1459,40 +2708,205 @@
 
         backgroundLayer.frame = bounds
 
-        let horizontalInset = max(36, bounds.width * 0.045)
-        let topInset = max(36, bounds.height * 0.055)
-        glassLayer.frame = bounds.insetBy(dx: horizontalInset, dy: topInset)
+        let safeAreaTopInset = topSafeAreaInset
+        safeAreaFillLayer.frame = CGRect(
+            x: 0,
+            y: max(0, bounds.height - safeAreaTopInset),
+            width: bounds.width,
+            height: safeAreaTopInset
+        )
+        safeAreaFillLayer.isHidden = safeAreaTopInset <= 0.5
+        glassLayer.frame = bounds
 
         let contentBounds = glassLayer.bounds
-        let horizontalMargin: CGFloat = 22
+        let horizontalMargin = RootLayoutMetrics.horizontalMargin
+        let topMargin = safeAreaTopInset + RootLayoutMetrics.topContentMargin
         let laneHeight = min(104, max(82, contentBounds.height * 0.12))
         let availableContentWidth = contentBounds.width - horizontalMargin * 2
         appShelfLayout = appShelfLayout(for: availableContentWidth)
         let shelfHeight = appShelfHeight(forRows: appShelfLayout.rows)
         laneLayer.frame = CGRect(
             x: horizontalMargin,
-            y: contentBounds.height - horizontalMargin - laneHeight,
+            y: contentBounds.height - topMargin - laneHeight,
             width: availableContentWidth,
             height: laneHeight
         )
         shelfLayer.frame = CGRect(
             x: horizontalMargin,
-            y: laneLayer.frame.minY - 16 - shelfHeight,
+            y: laneLayer.frame.minY - RootLayoutMetrics.shelfGap - shelfHeight,
             width: laneLayer.frame.width,
             height: shelfHeight
         )
         waterfallLayer.frame = CGRect(
             x: shelfLayer.frame.minX,
-            y: 34,
+            y: RootLayoutMetrics.bottomMargin,
             width: shelfLayer.frame.width,
-            height: shelfLayer.frame.minY - 48
+            height: max(1, shelfLayer.frame.minY - RootLayoutMetrics.bottomMargin - RootLayoutMetrics.waterfallTopGap)
         )
 
         layoutSpaceLaneSegments()
         layoutAppShelfItems()
         layoutWaterfallColumns()
+        layoutCloseConfirmation()
+        layoutCloseFeedback()
+        layoutViewModeToggleButton()
 
         CATransaction.commit()
+    }
+
+    private func layoutViewModeToggleButton() {
+        let size = ViewModeToggleMetrics.visualSize
+        let topMargin = topSafeAreaInset + RootLayoutMetrics.topContentMargin
+        let x = max(
+            RootLayoutMetrics.horizontalMargin,
+            glassLayer.bounds.width - RootLayoutMetrics.horizontalMargin - size
+        )
+        let y = max(
+            RootLayoutMetrics.bottomMargin,
+            glassLayer.bounds.height - topMargin - size
+        )
+        viewModeToggleButtonLayer.frame = CGRect(x: x, y: y, width: size, height: size)
+        viewModeToggleButtonLayer.cornerRadius = ViewModeToggleMetrics.cornerRadius
+        let visualState = viewModeToggleVisualState
+        let isSelectedState = viewModeToggleVisualStateIsSelected(visualState)
+        viewModeToggleButtonLayer.backgroundColor = (isSelectedState
+            ? viewModeToggleBlueColor
+            : NSColor.windowBackgroundColor.withAlphaComponent(isViewModeToggleButtonHovered ? 0.76 : 0.58)
+        ).cgColor
+        viewModeToggleButtonLayer.borderColor = (isSelectedState
+            ? viewModeToggleBlueColor.withAlphaComponent(0.96)
+            : viewModeToggleBlueColor.withAlphaComponent(isViewModeToggleButtonHovered ? 0.72 : 0.34)
+        ).cgColor
+        viewModeToggleButtonLayer.shadowOpacity = isSelectedState ? 0.16 : (isViewModeToggleButtonHovered ? 0.11 : 0.06)
+        viewModeToggleButtonLayer.shadowRadius = isSelectedState
+            ? ViewModeToggleMetrics.selectedShadowRadius
+            : ViewModeToggleMetrics.idleShadowRadius
+        viewModeToggleIconLayer.contentsScale = backingScaleFactor
+        let iconInset = ViewModeToggleMetrics.iconInset
+        viewModeToggleIconLayer.frame = viewModeToggleButtonLayer.bounds.insetBy(dx: iconInset, dy: iconInset)
+        layoutViewModeToggleIcon()
+    }
+
+    private func layoutViewModeToggleIcon() {
+        CATransaction.begin()
+        CATransaction.setDisableActions(true)
+        viewModeToggleIconLayer.sublayers?.forEach { $0.removeFromSuperlayer() }
+
+        let bounds = viewModeToggleIconLayer.bounds
+        guard bounds.width > 0, bounds.height > 0 else {
+            CATransaction.commit()
+            return
+        }
+
+        let visualState = viewModeToggleVisualState
+        let isSelectedState = viewModeToggleVisualStateIsSelected(visualState)
+        let strokeColor = isSelectedState
+            ? NSColor.white.withAlphaComponent(0.98)
+            : viewModeToggleBlueColor.withAlphaComponent(0.96)
+        let fillColor = isSelectedState
+            ? NSColor.white.withAlphaComponent(0.22)
+            : viewModeToggleBlueColor.withAlphaComponent(0.06)
+        let glyphRect = centeredSquare(in: bounds)
+
+        switch visualState {
+        case .verticalAvailable, .verticalSelected:
+            addVerticalColumnsToggleGlyph(
+                in: glyphRect,
+                strokeColor: strokeColor,
+                fillColor: fillColor
+            )
+        case .horizontalAvailable, .horizontalSelected:
+            addHorizontalMasonryToggleGlyph(
+                in: glyphRect,
+                strokeColor: strokeColor,
+                fillColor: fillColor
+            )
+        }
+
+        CATransaction.commit()
+    }
+
+    private func addVerticalColumnsToggleGlyph(
+        in rect: CGRect,
+        strokeColor: NSColor,
+        fillColor: NSColor
+    ) {
+        let columnWidth = rect.width * 0.22
+        let gap = (rect.width - columnWidth * 3) / 2
+        for index in 0..<3 {
+            let x = rect.minX + CGFloat(index) * (columnWidth + gap)
+            let columnRect = CGRect(x: x, y: rect.minY, width: columnWidth, height: rect.height)
+            addViewModeToggleRoundedRect(
+                columnRect,
+                cornerRadius: ViewModeToggleMetrics.glyphCornerRadius,
+                strokeColor: strokeColor,
+                fillColor: fillColor,
+                lineWidth: ViewModeToggleMetrics.glyphLineWidth
+            )
+        }
+    }
+
+    private func addHorizontalMasonryToggleGlyph(
+        in rect: CGRect,
+        strokeColor: NSColor,
+        fillColor: NSColor
+    ) {
+        let cellSize = rect.width * 0.38
+        let gap = rect.width - cellSize * 2
+        for row in 0..<2 {
+            for column in 0..<2 {
+                let cellRect = CGRect(
+                    x: rect.minX + CGFloat(column) * (cellSize + gap),
+                    y: rect.minY + CGFloat(row) * (cellSize + gap),
+                    width: cellSize,
+                    height: cellSize
+                )
+                addViewModeToggleRoundedRect(
+                    cellRect,
+                    cornerRadius: ViewModeToggleMetrics.glyphCornerRadius,
+                    strokeColor: strokeColor,
+                    fillColor: fillColor,
+                    lineWidth: ViewModeToggleMetrics.glyphLineWidth
+                )
+            }
+        }
+    }
+
+    private func addViewModeToggleRoundedRect(
+        _ rect: CGRect,
+        cornerRadius: CGFloat,
+        strokeColor: NSColor,
+        fillColor: NSColor,
+        lineWidth: CGFloat
+    ) {
+        let layer = CAShapeLayer()
+        layer.contentsScale = backingScaleFactor
+        layer.frame = viewModeToggleIconLayer.bounds
+        layer.path = CGPath(
+            roundedRect: rect,
+            cornerWidth: cornerRadius,
+            cornerHeight: cornerRadius,
+            transform: nil
+        )
+        layer.fillColor = fillColor.cgColor
+        layer.strokeColor = strokeColor.cgColor
+        layer.lineWidth = lineWidth
+        layer.lineJoin = .round
+        viewModeToggleIconLayer.addSublayer(layer)
+    }
+
+    private func centeredSquare(in rect: CGRect) -> CGRect {
+        let side = min(rect.width, rect.height)
+        return CGRect(
+            x: rect.midX - side / 2,
+            y: rect.midY - side / 2,
+            width: side,
+            height: side
+        )
+    }
+
+    private var topSafeAreaInset: CGFloat {
+        max(0, window?.screen?.safeAreaInsets.top ?? safeAreaInsets.top)
     }
 
     private func appShelfLayout(for availableWidth: CGFloat) -> AppShelfLayout {
@@ -1570,15 +2984,34 @@
     }
 
     private func layoutSpaceLaneSegments() {
-        guard !spaceLaneSegments.isEmpty else { return }
+        guard !spaceLaneDisplayGroups.isEmpty, !spaceLaneSegments.isEmpty else { return }
 
-        let gap: CGFloat = 10
-        let segmentHeight = max(1, laneLayer.bounds.height - 20)
-        let availableWidth = laneLayer.bounds.width - 24 - CGFloat(spaceLaneSegments.count - 1) * gap
-        let segmentWidth = max(96, min(150, availableWidth / CGFloat(spaceLaneSegments.count)))
+        let groupOuterVerticalInset: CGFloat = 6
+        let groupHeight = max(1, laneLayer.bounds.height - groupOuterVerticalInset * 2)
+        let segmentHeight = max(1, groupHeight - SpaceLaneMetrics.groupVerticalPadding * 2)
+        let groupGapWidth = CGFloat(max(0, spaceLaneDisplayGroups.count - 1)) * SpaceLaneMetrics.groupGap
+        let segmentGapWidth = spaceLaneDisplayGroups.reduce(CGFloat(0)) { total, group in
+            total + CGFloat(max(0, group.segments.count - 1)) * SpaceLaneMetrics.segmentGap
+        }
+        let groupPaddingWidth = CGFloat(spaceLaneDisplayGroups.count) * SpaceLaneMetrics.groupHorizontalPadding * 2
+        let availableWidth = laneLayer.bounds.width
+            - SpaceLaneMetrics.horizontalPadding * 2
+            - groupGapWidth
+            - segmentGapWidth
+            - groupPaddingWidth
+        let segmentWidth = max(
+            SpaceLaneMetrics.segmentMinWidth,
+            min(SpaceLaneMetrics.segmentMaxWidth, availableWidth / CGFloat(spaceLaneSegments.count))
+        )
+        let groupWidths = spaceLaneDisplayGroups.map { group in
+            SpaceLaneMetrics.groupHorizontalPadding * 2
+                + CGFloat(group.segments.count) * segmentWidth
+                + CGFloat(max(0, group.segments.count - 1)) * SpaceLaneMetrics.segmentGap
+        }
+        let segmentGroupWidth = groupWidths.reduce(0, +) + groupGapWidth
         spaceLaneContentWidth = max(
             laneLayer.bounds.width,
-            24 + CGFloat(spaceLaneSegments.count) * segmentWidth + CGFloat(spaceLaneSegments.count - 1) * gap
+            SpaceLaneMetrics.horizontalPadding * 2 + segmentGroupWidth
         )
         spaceLaneScrollOffset = clampedSpaceLaneOffset(spaceLaneScrollOffset)
         spaceLaneContentLayer.frame = CGRect(
@@ -1588,13 +3021,35 @@
             height: laneLayer.bounds.height
         )
 
-        var x: CGFloat = 12
+        var x = max(
+            SpaceLaneMetrics.horizontalPadding,
+            (spaceLaneContentWidth - segmentGroupWidth) / 2
+        )
 
-        for segment in spaceLaneSegments {
-            segment.containerLayer.frame = CGRect(x: x, y: 10, width: segmentWidth, height: segmentHeight)
-            applySpaceLaneVisualState(segment)
-            layoutSpaceLaneSegmentContents(segment)
-            x += segmentWidth + gap
+        for (index, group) in spaceLaneDisplayGroups.enumerated() {
+            let groupWidth = groupWidths[index]
+            group.containerLayer.frame = CGRect(
+                x: x,
+                y: groupOuterVerticalInset,
+                width: groupWidth,
+                height: groupHeight
+            )
+            applySpaceLaneDisplayGroupVisualState(group)
+
+            var segmentX = SpaceLaneMetrics.groupHorizontalPadding
+            for segment in group.segments {
+                segment.containerLayer.frame = CGRect(
+                    x: segmentX,
+                    y: SpaceLaneMetrics.groupVerticalPadding,
+                    width: segmentWidth,
+                    height: segmentHeight
+                )
+                applySpaceLaneVisualState(segment)
+                layoutSpaceLaneSegmentContents(segment)
+                segmentX += segmentWidth + SpaceLaneMetrics.segmentGap
+            }
+
+            x += groupWidth + SpaceLaneMetrics.groupGap
         }
     }
 
@@ -1606,32 +3061,127 @@
         min(max(0, offset), spaceLaneMaxScrollOffset)
     }
 
-    private func applySpaceLaneVisualState(_ segment: SpaceLaneSegmentLayers) {
-        let isHovered = segment.space.id == hoveredSpaceID
-        let isFocused = segment.space.id == activeSpaceFocusID
-        let isCurrent = segment.space.isCurrent
-        let isActive = isHovered || isFocused
+    private func applySpaceLaneDisplayGroupVisualState(_ group: SpaceLaneDisplayGroupLayers) {
+        let hasActiveSegment = group.segments.contains { segment in
+            segment.space.id == activeSpaceFocusID
+                || appHoverAssociatedSpaceIDs.contains(segment.space.id)
+                || segment.space.id == windowHoverAssociatedSpaceID
+                || segment.space.id == currentViewModel?.lockedSpaceID
+        }
+        let hasCurrentSegment = group.display.spaces.contains { $0.isCurrent }
+        group.containerLayer.backgroundColor = NSColor.windowBackgroundColor.cgColor
+        group.containerLayer.borderColor = NSColor.clear.cgColor
+        group.containerLayer.borderWidth = 0
+        group.containerLayer.shadowOpacity = 0
+        group.containerLayer.shadowRadius = 0
+        group.containerLayer.shadowOffset = .zero
+        group.containerLayer.zPosition = hasActiveSegment ? 8 : hasCurrentSegment ? 4 : 0
+        group.containerLayer.shadowPath = nil
+    }
 
-        segment.containerLayer.borderWidth = isCurrent ? 1.5 : 1
-        segment.containerLayer.borderColor = (isCurrent
-            ? NSColor.labelColor.withAlphaComponent(0.34)
+    private func applySpaceLaneVisualState(_ segment: SpaceLaneSegmentLayers) {
+        let isHovered = segment.space.id == activeSpaceFocusID
+        let isFocused = segment.space.id == activeSpaceFocusID
+        let isLocked = segment.space.id == currentViewModel?.lockedSpaceID
+        let isCurrent = segment.space.isCurrent
+        let hasWindows = segment.space.windowCount > 0
+        let isAppAssociated = appHoverAssociatedSpaceIDs.contains(segment.space.id)
+        let isWindowAssociated = segment.space.id == windowHoverAssociatedSpaceID
+        let isActive = isHovered || isFocused || isLocked
+        let isAssociated = (isAppAssociated || isWindowAssociated) && !isActive
+
+        segment.containerLayer.borderWidth = (hasWindows || isCurrent || isActive || isAssociated) ? 1.5 : 1
+        segment.containerLayer.borderColor = (isLocked
+            ? NSColor.white.withAlphaComponent(0.86)
             : isActive
-                ? NSColor.labelColor.withAlphaComponent(0.24)
+            ? spaceLaneOccupiedColor.withAlphaComponent(isLocked ? 0.92 : 0.62)
+            : isAssociated
+                ? spaceLaneOccupiedColor.withAlphaComponent(0.50)
+                : hasWindows
+                    ? spaceLaneOccupiedColor.withAlphaComponent(isCurrent ? 0.54 : 0.44)
+                : isCurrent
+                    ? NSColor.labelColor.withAlphaComponent(0.34)
                 : NSColor.separatorColor.withAlphaComponent(0.34)
         ).cgColor
-        segment.containerLayer.backgroundColor = (isActive
-            ? NSColor.windowBackgroundColor.withAlphaComponent(0.76)
-            : spaceColor(for: segment.space)
-        ).cgColor
-        segment.containerLayer.shadowOpacity = isCurrent ? 0.12 : isActive ? 0.08 : 0
-        segment.containerLayer.shadowRadius = isCurrent ? 10 : isActive ? 7 : 0
-        segment.containerLayer.shadowOffset = CGSize(width: 0, height: isCurrent ? -2 : -1)
-        segment.containerLayer.shadowPath = CGPath(
-            roundedRect: segment.containerLayer.bounds,
-            cornerWidth: segment.containerLayer.cornerRadius,
-            cornerHeight: segment.containerLayer.cornerRadius,
-            transform: nil
+        if isLocked {
+            applySpaceLaneSolidFill(
+                to: segment.containerLayer,
+                color: spaceLaneLockedFillColor
+            )
+        } else if !hasWindows {
+            applySpaceLaneSolidFill(to: segment.containerLayer, color: .clear)
+        } else if isActive {
+            applySpaceLaneSolidFill(
+                to: segment.containerLayer,
+                color: accentTintedWindowBackground(fraction: 0.10, alpha: 0.94)
+            )
+        } else if isAssociated {
+            applySpaceLaneSolidFill(
+                to: segment.containerLayer,
+                color: accentTintedWindowBackground(fraction: 0.07, alpha: 0.90)
+            )
+        } else if hasWindows {
+            applySpaceLaneGradientFill(
+                to: segment.containerLayer,
+                colors: spaceLaneIdleOccupiedGradientColors()
+            )
+        }
+        segment.containerLayer.shadowColor = isLocked
+            ? NSColor.white.withAlphaComponent(0.98).cgColor
+            : NSColor.black.cgColor
+        segment.containerLayer.shadowOpacity = (hasWindows || isLocked)
+            ? (isLocked ? 0.72 : isActive ? 0.26 : isAssociated ? 0.18 : isCurrent ? 0.14 : 0)
+            : 0
+        segment.containerLayer.shadowRadius = (hasWindows || isLocked)
+            ? (isLocked ? 30 : isActive ? 24 : isAssociated ? 18 : isCurrent ? 12 : 0)
+            : 0
+        segment.containerLayer.shadowOffset = CGSize(
+            width: 0,
+            height: (hasWindows || isLocked) ? (isLocked ? 0 : isActive ? -6 : isAssociated ? -4 : isCurrent ? -2.5 : 0) : 0
         )
+        segment.containerLayer.zPosition = isLocked ? 42 : isActive ? 30 : isAssociated ? 18 : isCurrent ? 10 : 0
+        segment.containerLayer.transform = (isActive || isAssociated)
+            ? CATransform3DMakeScale(isActive ? 1.03 : 1.015, isActive ? 1.03 : 1.015, 1)
+            : CATransform3DIdentity
+        segment.containerLayer.shadowPath = (hasWindows || isLocked)
+            ? CGPath(
+                roundedRect: segment.containerLayer.bounds,
+                cornerWidth: segment.containerLayer.cornerRadius,
+                cornerHeight: segment.containerLayer.cornerRadius,
+                transform: nil
+            )
+            : nil
+
+        applySpaceLaneContentVisualState(segment, isLocked: isLocked)
+    }
+
+    private func applySpaceLaneContentVisualState(_ segment: SpaceLaneSegmentLayers, isLocked: Bool) {
+        let primaryTextColor: NSColor = isLocked ? .white : .labelColor
+        let secondaryTextColor: NSColor = isLocked
+            ? .white
+            : .secondaryLabelColor
+
+        segment.labelLayer.foregroundColor = primaryTextColor.cgColor
+        segment.countLayer.foregroundColor = (isLocked ? NSColor.white : .secondaryLabelColor).cgColor
+        segment.appLayer.foregroundColor = (segment.space.type == .fullscreen
+            ? primaryTextColor
+            : secondaryTextColor
+        ).cgColor
+        for splitAppLayer in segment.splitAppLayers {
+            splitAppLayer.foregroundColor = primaryTextColor.cgColor
+        }
+
+        for block in segment.windowBlocks {
+            block.backgroundColor = (isLocked
+                ? NSColor.white
+                : spaceLaneOccupiedColor.withAlphaComponent(segment.space.isCurrent ? 0.72 : 0.58)
+            ).cgColor
+        }
+
+        (segment.fullscreenMarkerLayer as? CAShapeLayer)?.strokeColor = (isLocked
+            ? NSColor.white
+            : NSColor.secondaryLabelColor.withAlphaComponent(segment.space.isCurrent ? 0.42 : 0.28)
+        ).cgColor
     }
 
     private func shouldScrollSpaceLane(for event: NSEvent) -> Bool {
@@ -1672,18 +3222,63 @@
 
     private func spaceLaneSegment(at windowLocation: CGPoint) -> SpaceLaneSegmentLayers? {
         let locationInView = convert(windowLocation, from: nil)
+
+        // 严格 band 检查:只有鼠标在 lane 的垂直 band 内才考虑是 lane hover。
+        // 防止“完全空的地方”(y 不在 lane 高度范围内)误 hit 到 segment frame,
+        // 导致 hoveredSpaceLaneID 粘住、activeSpaceFocusID 非 nil、窗口 spaceFocused 高亮。
+        let laneMinYInView = glassLayer.frame.minY + laneLayer.frame.minY
+        let laneMaxYInView = laneMinYInView + laneLayer.frame.height
+        if locationInView.y < laneMinYInView || locationInView.y > laneMaxYInView {
+            return nil
+        }
+
         let locationInSpaceLaneContent = CGPoint(
             x: locationInView.x - glassLayer.frame.minX - laneLayer.frame.minX - spaceLaneContentLayer.frame.minX,
             y: locationInView.y - glassLayer.frame.minY - laneLayer.frame.minY - spaceLaneContentLayer.frame.minY
         )
 
-        return spaceLaneSegments.first { segment in
-            segment.containerLayer.frame.contains(locationInSpaceLaneContent)
+        for group in spaceLaneDisplayGroups where group.containerLayer.frame.contains(locationInSpaceLaneContent) {
+            let locationInGroup = CGPoint(
+                x: locationInSpaceLaneContent.x - group.containerLayer.frame.minX,
+                y: locationInSpaceLaneContent.y - group.containerLayer.frame.minY
+            )
+            if let segment = group.segments.first(where: { $0.containerLayer.frame.contains(locationInGroup) }) {
+                return segment
+            }
         }
+
+        return nil
     }
 
     private func spaceLaneSegment(spaceID: UInt64) -> SpaceLaneSegmentLayers? {
         spaceLaneSegments.first { $0.space.id == spaceID }
+    }
+
+    private func viewModeToggleButtonContains(windowLocation: CGPoint) -> Bool {
+        let locationInView = convert(windowLocation, from: nil)
+        let locationInGlass = CGPoint(
+            x: locationInView.x - glassLayer.frame.minX,
+            y: locationInView.y - glassLayer.frame.minY
+        )
+        let hitOutset = (ViewModeToggleMetrics.hitSize - ViewModeToggleMetrics.visualSize) / 2
+        return viewModeToggleButtonLayer.frame
+            .insetBy(dx: -hitOutset, dy: -hitOutset)
+            .contains(locationInGlass)
+    }
+
+    private func clickViewModeToggleButton(source: String) {
+        DevelopmentDiagnostics.log("quickSwitch.view.clickWaterfallViewModeToggle", [
+            "source": source,
+            "currentMode": waterfallViewMode.rawValue,
+            "targetMode": nextWaterfallViewMode.rawValue
+        ])
+        lastMouseCommand = "click-view-toggle"
+        if !mouseCommandsApplied.contains("click-view-toggle") {
+            mouseCommandsApplied.append("click-view-toggle")
+        }
+        isViewModeToggleButtonHovered = false
+        suppressViewModeToggleHoverPreview = true
+        onToggleWaterfallViewMode?()
     }
 
     private func appShelfItem(at windowLocation: CGPoint) -> AppShelfItemLayers? {
@@ -1725,12 +3320,62 @@
             .first(where: { $0.item.windowIndex == windowIndex })
     }
 
+    private func waterfallCard(windowID: UInt32) -> WaterfallCardLayers? {
+        waterfallColumns
+            .lazy
+            .flatMap(\.cards)
+            .first(where: { $0.item.window.id == windowID })
+    }
+
     private func layoutSpaceLaneSegmentContents(_ segment: SpaceLaneSegmentLayers) {
         let bounds = segment.containerLayer.bounds
+        let splitAppNames = splitViewAppNames(for: segment.space)
+        let isSplitView = splitAppNames.count >= 2
         segment.labelLayer.frame = CGRect(x: 10, y: bounds.height - 29, width: max(1, bounds.width - 48), height: 20)
         segment.countLayer.frame = CGRect(x: bounds.width - 34, y: bounds.height - 29, width: 24, height: 20)
-        segment.appLayer.frame = CGRect(x: 10, y: 9, width: max(1, bounds.width - 20), height: 17)
-        segment.fullscreenMarkerLayer?.frame = CGRect(x: 10, y: bounds.height - 7, width: max(1, bounds.width - 20), height: 3)
+        segment.countLayer.string = isSplitView ? "" : "\(segment.space.windowCount)"
+        segment.countLayer.isHidden = isSplitView
+        if segment.space.type == .fullscreen {
+            let markerFrame = fullscreenMarkerFrame(in: bounds)
+            segment.appLayer.isHidden = isSplitView
+            if isSplitView {
+                let labelY = markerFrame.midY - 8.5
+                let halfWidth = markerFrame.width / 2
+                for (index, splitAppLayer) in segment.splitAppLayers.enumerated() {
+                    let x = markerFrame.minX + CGFloat(index) * halfWidth
+                    splitAppLayer.isHidden = false
+                    splitAppLayer.frame = CGRect(
+                        x: x + 4,
+                        y: labelY,
+                        width: max(1, halfWidth - 8),
+                        height: 17
+                    )
+                }
+            } else {
+                segment.appLayer.frame = CGRect(
+                    x: 8,
+                    y: markerFrame.midY - 8.5,
+                    width: max(1, bounds.width - 16),
+                    height: 17
+                )
+                for splitAppLayer in segment.splitAppLayers {
+                    splitAppLayer.isHidden = true
+                }
+            }
+        } else {
+            segment.appLayer.isHidden = false
+            segment.appLayer.frame = CGRect(x: 10, y: 9, width: max(1, bounds.width - 20), height: 17)
+            for splitAppLayer in segment.splitAppLayers {
+                splitAppLayer.isHidden = true
+            }
+        }
+        if let fullscreenMarkerLayer = segment.fullscreenMarkerLayer {
+            layoutFullscreenMarkerLayer(
+                fullscreenMarkerLayer,
+                in: bounds,
+                isSplitView: isSplitView
+            )
+        }
 
         let blockGap: CGFloat = 5
         let blockWidth = max(12, min(22, (bounds.width - 20 - CGFloat(max(0, segment.windowBlocks.count - 1)) * blockGap) / CGFloat(max(1, segment.windowBlocks.count))))
@@ -1791,38 +3436,67 @@
         let bounds = item.containerLayer.bounds
         let isSelected = item.item.appGroupIndex == effectiveSelection?.appGroupIndex
         let isHovered = item.item.appGroupIndex == effectiveHoveredAppGroupIndex
+        let showsSelectedVisual = shouldShowSelectedVisual(isSelected: isSelected, isHovered: isHovered)
         let isSpaceFocused = spaceFocusWindowCount(for: item.item.appGroupIndex) > 0
-        let visualIconSize = appShelfVisualIconSize(forBaseIconSize: iconSize, selected: isSelected, hovered: isHovered)
-        let backgroundPadding: CGFloat = (isSelected || isHovered) ? 4 : 2
+        let visualIconSize = appShelfVisualIconSize(
+            forBaseIconSize: iconSize,
+            selected: showsSelectedVisual,
+            hovered: isHovered,
+            spaceFocused: isSpaceFocused
+        )
+        let backgroundPadding: CGFloat = (showsSelectedVisual || isHovered)
+            ? 4
+            : isSpaceFocused
+                ? 6
+                : 2
         let iconX = (bounds.width - visualIconSize) / 2
         let iconY = bounds.height - visualIconSize - 2
         let badgeText = appShelfBadgeText(for: item)
         let badgeWidth = max(18, CGFloat(badgeText.count) * 7 + 8)
 
-        item.containerLayer.zPosition = appShelfZPosition(selected: isSelected, hovered: isHovered)
+        item.containerLayer.zPosition = appShelfZPosition(
+            selected: showsSelectedVisual,
+            hovered: isHovered,
+            spaceFocused: isSpaceFocused
+        )
         item.backgroundLayer.backgroundColor = appShelfBackgroundColor(
-            selected: isSelected,
+            selected: showsSelectedVisual,
             hovered: isHovered,
             spaceFocused: isSpaceFocused
         ).cgColor
-        item.backgroundLayer.borderColor = (isSelected
-            ? NSColor.separatorColor.withAlphaComponent(0.38)
+        item.backgroundLayer.borderColor = (showsSelectedVisual
+            ? NSColor.controlAccentColor.withAlphaComponent(0.40)
             : isHovered
-                ? NSColor.separatorColor.withAlphaComponent(0.28)
+                ? NSColor.controlAccentColor.withAlphaComponent(0.36)
                 : NSColor.clear
         ).cgColor
-        item.backgroundLayer.borderWidth = (isSelected || isHovered) ? 1 : 0
+        item.backgroundLayer.borderWidth = (showsSelectedVisual || isHovered) ? 1 : 0
         item.backgroundLayer.shadowColor = NSColor.black.cgColor
-        item.backgroundLayer.shadowOpacity = isSelected ? 0.11 : isHovered ? 0.06 : 0
-        item.backgroundLayer.shadowRadius = isSelected ? 10 : isHovered ? 7 : 0
-        item.backgroundLayer.shadowOffset = CGSize(width: 0, height: -2)
+        item.backgroundLayer.shadowOpacity = showsSelectedVisual ? 0.11 : isHovered ? 0.07 : isSpaceFocused ? 0.18 : 0
+        item.backgroundLayer.shadowRadius = showsSelectedVisual ? 10 : isHovered ? 8 : isSpaceFocused ? 18 : 0
+        item.backgroundLayer.shadowOffset = CGSize(width: 0, height: isSpaceFocused ? -4 : -2)
         item.backgroundLayer.frame = CGRect(
             x: iconX - backgroundPadding,
             y: iconY - backgroundPadding,
             width: visualIconSize + backgroundPadding * 2,
             height: visualIconSize + backgroundPadding * 2
         )
+        item.backgroundLayer.shadowPath = (showsSelectedVisual || isHovered || isSpaceFocused)
+            ? CGPath(
+                roundedRect: item.backgroundLayer.bounds,
+                cornerWidth: item.backgroundLayer.cornerRadius,
+                cornerHeight: item.backgroundLayer.cornerRadius,
+                transform: nil
+            )
+            : nil
         item.iconLayer.frame = CGRect(x: iconX, y: iconY, width: visualIconSize, height: visualIconSize)
+        layoutAppShelfIndexLayer(
+            item.indexLayer,
+            iconFrame: item.iconLayer.frame,
+            iconSize: visualIconSize,
+            itemBounds: bounds,
+            highlighted: showsSelectedVisual || isHovered
+        )
         item.labelLayer.contentsScale = backingScaleFactor
         item.labelLayer.frame = CGRect(x: 0, y: 0, width: bounds.width, height: 14)
         item.badgeLayer.string = badgeText
@@ -1837,8 +3511,78 @@
             width: badgeWidth,
             height: 16
         )
+        layoutCloseButton(
+            item.closeButton,
+            target: .app(appGroupIndex: item.item.appGroupIndex),
+            visible: isHovered && canClose(app: item.item.app),
+            anchorTopRight: CGPoint(
+                x: min(iconX + visualIconSize - 6, bounds.width - 12),
+                y: min(iconY + visualIconSize - 6, bounds.height - 12)
+            )
+        )
         item.selectedIndicatorLayer.frame = .zero
         item.selectedIndicatorLayer.backgroundColor = NSColor.clear.cgColor
+    }
+
+    private var appShelfIndexColor: NSColor {
+        NSColor.labelColor.withAlphaComponent(0.34)
+    }
+
+    private var appShelfIndexHighlightedColor: NSColor {
+        NSColor.labelColor.withAlphaComponent(0.42)
+    }
+
+    private func appShelfIndexFont(size: CGFloat) -> NSFont {
+        for fontName in ["Bradley Hand ITC", "Noteworthy-Light", "Marker Felt", "Snell Roundhand"] {
+            if let font = NSFont(name: fontName, size: size) {
+                return font
+            }
+        }
+
+        return NSFont.monospacedSystemFont(ofSize: size, weight: .regular)
+    }
+
+    private func appShelfIndexText(forOrdinal ordinal: Int) -> String {
+        let symbols = Array("1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ")
+        guard ordinal >= 0 else { return "" }
+        if ordinal < symbols.count {
+            return String(symbols[ordinal])
+        }
+
+        let overflowIndex = ordinal - symbols.count
+        let prefix = symbols[10 + (overflowIndex / 26) % 26]
+        let suffix = symbols[10 + overflowIndex % 26]
+        return "\(prefix)\(suffix)"
+    }
+
+    private func layoutAppShelfIndexLayer(
+        _ layer: CATextLayer,
+        iconFrame: CGRect,
+        iconSize: CGFloat,
+        itemBounds: CGRect,
+        highlighted: Bool
+    ) {
+        let fontSize = iconSize <= AppShelfMetrics.minIconSize + 1
+            ? AppShelfMetrics.compressedIndexFontSize
+            : AppShelfMetrics.indexFontSize
+        layer.contentsScale = backingScaleFactor
+        layer.font = appShelfIndexFont(size: fontSize)
+        layer.fontSize = fontSize
+        layer.foregroundColor = (highlighted ? appShelfIndexHighlightedColor : appShelfIndexColor).cgColor
+        layer.opacity = iconSize <= AppShelfMetrics.minIconSize + 1 ? 0.72 : 0.82
+
+        let indexWidth = AppShelfMetrics.indexWidth
+        let indexHeight = AppShelfMetrics.indexHeight
+        let preferredX = iconFrame.minX - indexWidth - 1
+        let clampedX = max(-6, min(itemBounds.width - indexWidth, preferredX))
+        let preferredY = iconFrame.maxY - indexHeight + 4
+        let clampedY = max(0, min(itemBounds.height - indexHeight, preferredY))
+        layer.frame = CGRect(
+            x: clampedX,
+            y: clampedY,
+            width: indexWidth,
+            height: indexHeight
+        )
     }
 
     private func appShelfRows() -> [[AppShelfItemLayers]] {
@@ -1864,7 +3608,60 @@
     }
 
     private var activeSpaceFocusID: UInt64? {
-        focusedSpaceID ?? hoveredSpaceLaneID
+        guard case .space(let spaceID) = hoverTarget else { return nil }
+
+        if hoverTargetSource == .debug {
+            return spaceID
+        }
+
+        guard let window else { return nil }
+        let currentMouseLocation = window.mouseLocationOutsideOfEventStream
+        guard let segment = spaceLaneSegment(at: currentMouseLocation),
+              segment.space.id == spaceID
+        else {
+            return nil
+        }
+        return spaceID
+    }
+
+    private var appHoverAssociatedSpaceIDs: Set<UInt64> {
+        guard case .app(let appGroupIndex) = hoverTarget else { return [] }
+        return Set(
+            waterfallColumns
+                .first { $0.column.appGroupIndex == appGroupIndex }?
+                .cards
+                .compactMap(\.item.primarySpaceID) ?? []
+        )
+    }
+
+    private var appIconHoverLinkedAppGroupIndex: Int? {
+        if let debugHoveredAppGroupIndex {
+            return debugHoveredAppGroupIndex
+        }
+        guard case .app(let appGroupIndex) = hoverTarget else { return nil }
+        return appGroupIndex
+    }
+
+    private var appHoverAssociatedSpaceLabels: [String] {
+        guard !appHoverAssociatedSpaceIDs.isEmpty else { return [] }
+        return currentViewModel?.displays
+            .flatMap(\.spaces)
+            .filter { appHoverAssociatedSpaceIDs.contains($0.id) }
+            .map(\.label)
+            .sorted() ?? []
+    }
+
+    private var windowHoverAssociatedSpaceID: UInt64? {
+        guard case .window(_, _, let spaceID) = hoverTarget else { return nil }
+        return spaceID
+    }
+
+    private var isSpaceAssociationActive: Bool {
+        activeSpaceFocusID != nil
+    }
+
+    private func shouldShowSelectedVisual(isSelected: Bool, isHovered: Bool) -> Bool {
+        isSelected && isHovered && !isSpaceAssociationActive
     }
 
     private func spaceFocusedAppGroupIndexes() -> [Int] {
@@ -1880,6 +3677,18 @@
             }
             .map(\.column.appGroupIndex)
             .sorted()
+    }
+
+    private func firstWaterfallCard(inSpaceID spaceID: UInt64) -> WaterfallCardLayers? {
+        for column in waterfallColumns.sorted(by: { $0.column.appGroupIndex < $1.column.appGroupIndex }) {
+            if let card = column.cards
+                .sorted(by: { $0.item.windowIndex < $1.item.windowIndex })
+                .first(where: { $0.item.primarySpaceID == spaceID }) {
+                return card
+            }
+        }
+
+        return nil
     }
 
     private func spaceFocusWindowCount(for appGroupIndex: Int) -> Int {
@@ -1899,6 +3708,10 @@
             return "none"
         }
 
+        guard !isHorizontalMasonryMode else {
+            return "visible"
+        }
+
         let visibleMinX = waterfallScrollOffset
         let visibleMaxX = waterfallScrollOffset + waterfallLayer.bounds.width
         if column.containerLayer.frame.maxX < visibleMinX + WaterfallMetrics.gap {
@@ -1910,33 +3723,45 @@
         return "visible"
     }
 
-    private func appShelfVisualIconSize(forBaseIconSize iconSize: CGFloat, selected: Bool, hovered: Bool) -> CGFloat {
-        guard selected || hovered else { return iconSize }
-        return AppShelfMetrics.selectedIconSize
+    private func appShelfVisualIconSize(
+        forBaseIconSize iconSize: CGFloat,
+        selected: Bool,
+        hovered: Bool,
+        spaceFocused: Bool
+    ) -> CGFloat {
+        if selected || hovered {
+            return AppShelfMetrics.selectedIconSize
+        }
+        if spaceFocused {
+            return min(AppShelfMetrics.selectedIconSize, iconSize + 8)
+        }
+        return iconSize
     }
 
-    private func appShelfZPosition(selected: Bool, hovered: Bool) -> CGFloat {
-        switch (selected, hovered) {
-        case (true, true):
+    private func appShelfZPosition(selected: Bool, hovered: Bool, spaceFocused: Bool) -> CGFloat {
+        switch (selected, hovered, spaceFocused) {
+        case (true, true, _):
             return 30
-        case (true, false):
-            return 20
-        case (false, true):
-            return 10
-        case (false, false):
+        case (true, false, _):
+            return 24
+        case (false, true, _):
+            return 18
+        case (false, false, true):
+            return 12
+        case (false, false, false):
             return 0
         }
     }
 
     private func appShelfBackgroundColor(selected: Bool, hovered: Bool, spaceFocused: Bool) -> NSColor {
         if selected {
-            return NSColor.controlAccentColor.withAlphaComponent(0.12)
+            return NSColor.controlAccentColor.withAlphaComponent(0.14)
         }
         if hovered {
-            return NSColor.systemFill.withAlphaComponent(0.12)
+            return NSColor.controlAccentColor.withAlphaComponent(0.13)
         }
         if spaceFocused {
-            return NSColor.keyboardFocusIndicatorColor.withAlphaComponent(0.10)
+            return NSColor.controlAccentColor.withAlphaComponent(0.14)
         }
         return .clear
     }
@@ -1969,17 +3794,24 @@
     }
 
     private func layoutWaterfallColumns() {
+        if isHorizontalMasonryMode {
+            layoutHorizontalMasonryWaterfall()
+            return
+        }
+
         guard !waterfallColumns.isEmpty else {
             waterfallContentWidth = waterfallLayer.bounds.width
             waterfallScrollOffset = 0
+            horizontalMasonryContentHeight = waterfallLayer.bounds.height
+            horizontalMasonryScrollOffset = 0
             waterfallContentLayer.frame = waterfallLayer.bounds
             return
         }
 
         let columnWidth = waterfallColumnWidth()
-        let totalWidth = WaterfallMetrics.columnPadding * 2
-            + CGFloat(waterfallColumns.count) * columnWidth
+        let columnsWidth = CGFloat(waterfallColumns.count) * columnWidth
             + CGFloat(max(0, waterfallColumns.count - 1)) * WaterfallMetrics.gap
+        let totalWidth = WaterfallMetrics.contentHorizontalPadding * 2 + columnsWidth
         waterfallContentWidth = max(waterfallLayer.bounds.width, totalWidth)
         waterfallScrollOffset = clampedWaterfallAlignmentOffset(waterfallScrollOffset)
         waterfallContentLayer.frame = CGRect(
@@ -1989,7 +3821,7 @@
             height: waterfallLayer.bounds.height
         )
 
-        var x = WaterfallMetrics.columnPadding
+        var x = waterfallColumnStartX(columnsWidth: columnsWidth)
         for column in waterfallColumns {
             column.containerLayer.frame = CGRect(
                 x: x,
@@ -2002,9 +3834,177 @@
         }
     }
 
+    private func layoutHorizontalMasonryWaterfall() {
+        guard !waterfallColumns.isEmpty else {
+            waterfallContentWidth = waterfallLayer.bounds.width
+            waterfallScrollOffset = 0
+            horizontalMasonryContentHeight = waterfallLayer.bounds.height
+            horizontalMasonryScrollOffset = 0
+            waterfallContentLayer.frame = waterfallLayer.bounds
+            return
+        }
+
+        let layout = horizontalMasonryLayout()
+        waterfallContentWidth = waterfallLayer.bounds.width
+        waterfallScrollOffset = 0
+        horizontalMasonryContentHeight = layout.contentHeight
+        horizontalMasonryScrollOffset = clampedHorizontalMasonryOffset(horizontalMasonryScrollOffset)
+        waterfallContentLayer.frame = horizontalMasonryContentFrame()
+
+        for column in waterfallColumns {
+            column.containerLayer.frame = CGRect(
+                x: 0,
+                y: 0,
+                width: waterfallContentWidth,
+                height: horizontalMasonryContentHeight
+            )
+            column.containerLayer.masksToBounds = false
+            column.containerLayer.backgroundColor = NSColor.clear.cgColor
+            column.containerLayer.borderColor = NSColor.clear.cgColor
+            column.containerLayer.borderWidth = 0
+            column.containerLayer.shadowOpacity = 0
+            column.containerLayer.shadowRadius = 0
+            column.containerLayer.shadowOffset = .zero
+            column.headerLayer.isHidden = true
+            column.appNameLayer.isHidden = true
+            column.countLayer.isHidden = true
+
+            for card in column.cards {
+                if let frame = layout.cardFramesByWindowID[card.item.window.id] {
+                    card.containerLayer.frame = frame
+                } else {
+                    card.containerLayer.frame = .zero
+                }
+                layoutWaterfallCard(card)
+            }
+        }
+    }
+
+    private struct HorizontalMasonryLayout {
+        let contentHeight: CGFloat
+        let cardFramesByWindowID: [UInt32: CGRect]
+    }
+
+    private func horizontalMasonryLayout() -> HorizontalMasonryLayout {
+        let cards = horizontalMasonryCardsInPlacementOrder()
+        guard !cards.isEmpty else {
+            return HorizontalMasonryLayout(
+                contentHeight: waterfallLayer.bounds.height,
+                cardFramesByWindowID: [:]
+            )
+        }
+
+        let viewportWidth = max(1, waterfallLayer.bounds.width)
+        let availableWidth = max(
+            HorizontalMasonryMetrics.cardMinWidth,
+            viewportWidth - HorizontalMasonryMetrics.horizontalPadding * 2
+        )
+        let maximumLaneCount = max(
+            1,
+            Int(
+                floor(
+                    (availableWidth + HorizontalMasonryMetrics.horizontalGap)
+                        / (HorizontalMasonryMetrics.cardMinWidth + HorizontalMasonryMetrics.horizontalGap)
+                )
+            )
+        )
+        let laneCount = min(maximumLaneCount, max(1, cards.count))
+        let fittingWidth = (
+            availableWidth - CGFloat(max(0, laneCount - 1)) * HorizontalMasonryMetrics.horizontalGap
+        ) / CGFloat(laneCount)
+        let cardWidth = floor(
+            min(
+                HorizontalMasonryMetrics.cardMaxWidth,
+                max(HorizontalMasonryMetrics.cardMinWidth, fittingWidth)
+            )
+        )
+        let usedWidth = CGFloat(laneCount) * cardWidth
+            + CGFloat(max(0, laneCount - 1)) * HorizontalMasonryMetrics.horizontalGap
+        let startX = max(
+            HorizontalMasonryMetrics.horizontalPadding,
+            (viewportWidth - usedWidth) / 2
+        )
+
+        var laneHeights = Array(repeating: CGFloat(0), count: laneCount)
+        var plannedFrames: [(windowID: UInt32, x: CGFloat, top: CGFloat, width: CGFloat, height: CGFloat)] = []
+
+        for card in cards {
+            let laneIndex = laneHeights.enumerated().min { lhs, rhs in
+                if abs(lhs.element - rhs.element) > 0.5 {
+                    return lhs.element < rhs.element
+                }
+                return lhs.offset < rhs.offset
+            }?.offset ?? 0
+            let cardHeight = HorizontalMasonryMetrics.cardHeight
+            let x = startX + CGFloat(laneIndex) * (cardWidth + HorizontalMasonryMetrics.horizontalGap)
+            let top = HorizontalMasonryMetrics.verticalPadding + laneHeights[laneIndex]
+            plannedFrames.append((
+                windowID: card.item.window.id,
+                x: x,
+                top: top,
+                width: cardWidth,
+                height: cardHeight
+            ))
+            laneHeights[laneIndex] += cardHeight + HorizontalMasonryMetrics.verticalGap
+        }
+
+        let tallestLane = laneHeights.max().map {
+            max(0, $0 - HorizontalMasonryMetrics.verticalGap)
+        } ?? 0
+        let contentHeight = max(
+            waterfallLayer.bounds.height,
+            HorizontalMasonryMetrics.verticalPadding * 2 + tallestLane
+        )
+        let frames = Dictionary(
+            uniqueKeysWithValues: plannedFrames.map { planned in
+                (
+                    planned.windowID,
+                    CGRect(
+                        x: planned.x,
+                        y: contentHeight - planned.top - planned.height,
+                        width: planned.width,
+                        height: planned.height
+                    )
+                )
+            }
+        )
+
+        return HorizontalMasonryLayout(contentHeight: contentHeight, cardFramesByWindowID: frames)
+    }
+
+    private func horizontalMasonryContentFrame() -> CGRect {
+        let contentHeight = max(waterfallLayer.bounds.height, horizontalMasonryContentHeight)
+        return CGRect(
+            x: 0,
+            y: waterfallLayer.bounds.height - contentHeight + horizontalMasonryScrollOffset,
+            width: waterfallLayer.bounds.width,
+            height: contentHeight
+        )
+    }
+
+    private func waterfallColumnStartX(columnsWidth: CGFloat) -> CGFloat {
+        guard currentViewModel?.lockedSpaceID != nil else {
+            return WaterfallMetrics.contentHorizontalPadding
+        }
+
+        let centeredStart = (waterfallContentWidth - columnsWidth) / 2
+        return max(WaterfallMetrics.contentHorizontalPadding, centeredStart)
+    }
+
     private func layoutWaterfallColumn(_ column: WaterfallColumnLayers) {
+        column.containerLayer.cornerRadius = 14
+        column.containerLayer.masksToBounds = true
+        column.containerLayer.backgroundColor = NSColor.controlBackgroundColor.withAlphaComponent(0.56).cgColor
+        column.containerLayer.shadowOpacity = 0
+        column.containerLayer.shadowRadius = 0
+        column.containerLayer.shadowOffset = .zero
+        column.headerLayer.isHidden = false
+        column.appNameLayer.isHidden = false
+        column.countLayer.isHidden = false
+
         let bounds = column.containerLayer.bounds
         let isSpaceFocused = spaceFocusWindowCount(for: column.column.appGroupIndex) > 0
+        let isHovered = column.column.appGroupIndex == effectiveHoveredAppGroupIndex
         column.containerLayer.borderColor = (isSpaceFocused
             ? NSColor.separatorColor.withAlphaComponent(0.38)
             : NSColor.separatorColor.withAlphaComponent(0.24)
@@ -2016,22 +4016,26 @@
             width: bounds.width,
             height: WaterfallMetrics.headerHeight
         )
-        column.headerLayer.backgroundColor = (isSpaceFocused
-            ? NSColor.systemFill.withAlphaComponent(0.10)
-            : NSColor.controlBackgroundColor.withAlphaComponent(0.52)
+        column.headerLayer.backgroundColor = (isHovered
+            ? viewModeToggleBlueColor
+            : (isSpaceFocused
+                ? NSColor.systemFill.withAlphaComponent(0.10)
+                : NSColor.controlBackgroundColor.withAlphaComponent(0.52))
         ).cgColor
         column.appNameLayer.frame = CGRect(
-            x: WaterfallMetrics.columnPadding,
+            x: WaterfallMetrics.columnHeaderTextInset,
             y: bounds.height - 24,
-            width: max(1, bounds.width - 64),
+            width: max(1, bounds.width - WaterfallMetrics.columnHeaderTextInset * 2),
             height: 16
         )
+        column.appNameLayer.foregroundColor = (isHovered ? NSColor.white : NSColor.labelColor).cgColor
         column.countLayer.frame = CGRect(
             x: bounds.width - 48,
             y: bounds.height - 24,
             width: 36,
             height: 16
         )
+        column.countLayer.foregroundColor = (isHovered ? NSColor.white : NSColor.secondaryLabelColor).cgColor
 
         let appGroupIndex = column.column.appGroupIndex
         let verticalOffset = clampedWaterfallColumnOffset(
@@ -2040,10 +4044,10 @@
         )
         waterfallColumnScrollOffsets[appGroupIndex] = verticalOffset
 
-        let cardWidth = max(1, bounds.width - WaterfallMetrics.columnPadding * 2)
+        let cardWidth = max(1, bounds.width - WaterfallMetrics.columnHorizontalPadding * 2)
         let firstCardTop = bounds.height
             - WaterfallMetrics.headerHeight
-            - WaterfallMetrics.columnPadding
+            - WaterfallMetrics.columnVerticalPadding
             + verticalOffset
 
         for card in column.cards {
@@ -2052,7 +4056,7 @@
                 - WaterfallMetrics.cardHeight
                 - CGFloat(cardIndex) * (WaterfallMetrics.cardHeight + WaterfallMetrics.cardGap)
             card.containerLayer.frame = CGRect(
-                x: WaterfallMetrics.columnPadding,
+                x: WaterfallMetrics.columnHorizontalPadding,
                 y: y,
                 width: cardWidth,
                 height: WaterfallMetrics.cardHeight
@@ -2065,33 +4069,66 @@
         let bounds = card.containerLayer.bounds
         let isSelected = card.item.window.id == effectiveSelection?.windowID
         let isHovered = card.item.window.id == hoveredWindowID
-        applyWaterfallCardVisualState(card, selected: isSelected, hovered: isHovered)
-
-        let thumbnailWidth = max(90, min(116, bounds.width * 0.44))
-        card.thumbnailLayer.frame = CGRect(
-            x: 10,
-            y: 12,
-            width: thumbnailWidth,
-            height: bounds.height - 24
+        let isAppLinked = isHorizontalMasonryMode
+            && card.item.appGroupIndex == appIconHoverLinkedAppGroupIndex
+        applyWaterfallCardVisualState(
+            card,
+            selected: shouldShowSelectedVisual(isSelected: isSelected, isHovered: isHovered),
+            hovered: isHovered,
+            appLinked: isAppLinked
         )
-        card.appIconLayer.frame = CGRect(x: 18, y: bounds.height - 38, width: 22, height: 22)
+
+        let outerInset: CGFloat = 0
+        let titleBarHeight: CGFloat = 26
+        let titleGap: CGFloat = 6
+        let titleBarFrame = CGRect(
+            x: outerInset,
+            y: bounds.height - outerInset - titleBarHeight,
+            width: max(1, bounds.width - outerInset * 2),
+            height: titleBarHeight
+        )
+        let thumbnailFrame = CGRect(
+            x: outerInset,
+            y: outerInset,
+            width: max(1, bounds.width - outerInset * 2),
+            height: max(1, titleBarFrame.minY - outerInset - titleGap)
+        )
+
+        card.thumbnailLayer.frame = CGRect(
+            x: thumbnailFrame.minX,
+            y: thumbnailFrame.minY,
+            width: thumbnailFrame.width,
+            height: thumbnailFrame.height
+        )
+        card.titleBarLayer.frame = titleBarFrame
+        card.appIconLayer.frame = CGRect(x: titleBarFrame.minX + 7, y: titleBarFrame.minY + 5, width: 16, height: 16)
         card.titleLayer.frame = CGRect(
-            x: thumbnailWidth + 22,
-            y: bounds.height - 31,
-            width: max(1, bounds.width - thumbnailWidth - 34),
+            x: titleBarFrame.minX + 29,
+            y: titleBarFrame.minY + 6,
+            width: max(1, titleBarFrame.width - 68),
             height: 16
         )
         card.metaLayer.frame = CGRect(
-            x: thumbnailWidth + 22,
-            y: bounds.height - 51,
-            width: max(1, bounds.width - thumbnailWidth - 34),
+            x: titleBarFrame.maxX - 38,
+            y: titleBarFrame.minY + 6,
+            width: 30,
             height: 14
         )
         card.stateLayer.frame = CGRect(
-            x: thumbnailWidth + 22,
-            y: 12,
-            width: max(1, bounds.width - thumbnailWidth - 34),
+            x: thumbnailFrame.maxX - 86,
+            y: thumbnailFrame.minY + 6,
+            width: 78,
             height: 14
+        )
+        layoutCloseButton(
+            card.closeButton,
+            target: .window(
+                appGroupIndex: card.item.appGroupIndex,
+                windowIndex: card.item.windowIndex,
+                windowID: card.item.window.id
+            ),
+            visible: isHovered,
+            anchorTopRight: CGPoint(x: bounds.maxX - 12, y: bounds.maxY - 12)
         )
         card.shineLayer.frame = CGRect(
             x: -bounds.width * 0.18,
@@ -2101,35 +4138,589 @@
         )
     }
 
-    private func applyWaterfallCardVisualState(_ card: WaterfallCardLayers, selected: Bool, hovered: Bool) {
-        let isSpaceFocused = card.item.primarySpaceID == activeSpaceFocusID
+    private func applyWaterfallCardVisualState(
+        _ card: WaterfallCardLayers,
+        selected: Bool,
+        hovered: Bool,
+        appLinked: Bool
+    ) {
+        let isSpaceFocused = isWaterfallCardSpaceFocused(card)
         card.containerLayer.backgroundColor = (selected
             ? NSColor.windowBackgroundColor.withAlphaComponent(0.94)
             : hovered
-                ? NSColor.systemFill.withAlphaComponent(0.13)
+                ? accentTintedWindowBackground(fraction: 0.09, alpha: 0.95)
+                : appLinked
+                    ? accentTintedWindowBackground(fraction: 0.08, alpha: 0.93)
                 : isSpaceFocused
-                    ? NSColor.windowBackgroundColor.withAlphaComponent(0.88)
+                    ? accentTintedWindowBackground(fraction: 0.10, alpha: 0.94)
                 : NSColor.windowBackgroundColor.withAlphaComponent(0.82)
         ).cgColor
         card.containerLayer.borderColor = (selected
             ? NSColor.controlAccentColor.withAlphaComponent(0.52)
             : hovered
-                ? NSColor.separatorColor.withAlphaComponent(0.46)
+                ? NSColor.controlAccentColor.withAlphaComponent(0.44)
+                : appLinked
+                    ? NSColor.controlAccentColor.withAlphaComponent(0.38)
                 : isSpaceFocused
-                    ? NSColor.separatorColor.withAlphaComponent(0.38)
+                    ? NSColor.controlAccentColor.withAlphaComponent(0.42)
                 : NSColor.separatorColor.withAlphaComponent(0.28)
         ).cgColor
-        card.containerLayer.borderWidth = selected ? 1.5 : 1
+        card.containerLayer.borderWidth = (selected || hovered || appLinked || isSpaceFocused) ? 1.5 : 1
         card.containerLayer.shadowColor = NSColor.black.cgColor
-        card.containerLayer.shadowOpacity = selected ? 0.20 : hovered ? 0.08 : 0
-        card.containerLayer.shadowRadius = selected ? 18 : hovered ? 10 : 0
+        card.containerLayer.shadowOpacity = selected ? 0.24 : hovered ? 0.14 : appLinked ? 0.16 : isSpaceFocused ? 0.20 : 0
+        card.containerLayer.shadowRadius = selected ? 22 : hovered ? 17 : appLinked ? 18 : isSpaceFocused ? 24 : 0
         card.containerLayer.shadowOffset = selected
-            ? CGSize(width: 0, height: -5)
+            ? CGSize(width: 0, height: -6)
             : hovered
-                ? CGSize(width: 0, height: -2)
-                : .zero
-        card.containerLayer.zPosition = selected ? 20 : hovered ? 10 : 0
+                ? CGSize(width: 0, height: -2.5)
+                : appLinked
+                    ? CGSize(width: 0, height: -3)
+                : isSpaceFocused
+                    ? CGSize(width: 0, height: -5)
+                    : .zero
+        card.containerLayer.zPosition = selected ? 20 : hovered ? 12 : appLinked ? 10 : isSpaceFocused ? 8 : 0
+        let focusedScale: CGFloat = selected ? 1.015 : isSpaceFocused ? 1.012 : 1.008
+        card.containerLayer.transform = (selected || hovered || isSpaceFocused)
+            ? CATransform3DMakeScale(focusedScale, focusedScale, 1)
+            : CATransform3DIdentity
+        card.containerLayer.shadowPath = (selected || hovered || appLinked || isSpaceFocused)
+            ? CGPath(
+                roundedRect: card.containerLayer.bounds,
+                cornerWidth: card.containerLayer.cornerRadius,
+                cornerHeight: card.containerLayer.cornerRadius,
+                transform: nil
+            )
+            : nil
+        card.titleBarLayer.backgroundColor = appLinked
+            ? spaceLaneOccupiedColor.withAlphaComponent(0.18).cgColor
+            : NSColor.clear.cgColor
+        card.titleBarLayer.borderColor = NSColor.clear.cgColor
+        card.titleBarLayer.borderWidth = 0
         card.shineLayer.opacity = selected ? 1 : 0
+    }
+
+    private func layoutCloseButton(
+        _ button: CloseButtonLayers,
+        target: CloseTarget,
+        visible: Bool,
+        anchorTopRight: CGPoint
+    ) {
+        let isButtonHovered = hoveredCloseTarget == target
+        let size: CGFloat = isButtonHovered ? 24 : 18
+        let buttonFill = isButtonHovered
+            ? NSColor.systemRed.withAlphaComponent(0.94)
+            : NSColor.white.withAlphaComponent(0.34)
+        let buttonStroke = isButtonHovered
+            ? NSColor.white.withAlphaComponent(0.76)
+            : NSColor.white.withAlphaComponent(0.46)
+        let glyphStroke = isButtonHovered
+            ? NSColor.white
+            : NSColor.white.withAlphaComponent(0.88)
+
+        button.containerLayer.frame = CGRect(
+            x: anchorTopRight.x - size / 2,
+            y: anchorTopRight.y - size / 2,
+            width: size,
+            height: size
+        )
+        button.containerLayer.cornerRadius = size / 2
+        button.containerLayer.backgroundColor = buttonFill.cgColor
+        button.containerLayer.borderColor = buttonStroke.cgColor
+        button.containerLayer.opacity = visible ? 1 : 0
+        button.containerLayer.zPosition = isButtonHovered ? 80 : 60
+        button.containerLayer.shadowOpacity = visible ? (isButtonHovered ? 0.22 : 0.04) : 0
+        button.containerLayer.shadowRadius = isButtonHovered ? 9 : 5
+        button.glyphLayer.frame = CGRect(x: 0, y: 0, width: size, height: size)
+        button.glyphLayer.lineWidth = isButtonHovered ? 2.1 : 1.45
+        button.glyphLayer.strokeColor = glyphStroke.cgColor
+        button.glyphLayer.path = closeGlyphPath(size: size, hovered: isButtonHovered)
+    }
+
+    private func closeGlyphPath(size: CGFloat, hovered: Bool) -> CGPath {
+        let inset: CGFloat = hovered ? 7.2 : 5.6
+        let path = CGMutablePath()
+        path.move(to: CGPoint(x: inset, y: inset))
+        path.addLine(to: CGPoint(x: size - inset, y: size - inset))
+        path.move(to: CGPoint(x: size - inset, y: inset))
+        path.addLine(to: CGPoint(x: inset, y: size - inset))
+        return path
+    }
+
+    private func canClose(app: AlignerApp) -> Bool {
+        guard let processIdentifier = app.processIdentifier else { return false }
+        return processIdentifier != getpid()
+    }
+
+    private func layoutCloseConfirmation() {
+        guard let pendingCloseTarget,
+              let request = closeRequest(for: pendingCloseTarget),
+              let anchor = closeConfirmationAnchor(for: pendingCloseTarget)
+        else {
+            closeConfirmationLayers.containerLayer.isHidden = true
+            closeConfirmationArrowEdge = nil
+            return
+        }
+
+        let contentWidth: CGFloat = 374
+        let height: CGFloat = 184
+        let arrowWidth: CGFloat = 14
+        let edgeMargin: CGFloat = 16
+        let anchorGap: CGFloat = 12
+        let width = contentWidth + arrowWidth
+        let availableRight = glassLayer.bounds.maxX - anchor.x - edgeMargin
+        let availableLeft = anchor.x - glassLayer.bounds.minX - edgeMargin
+        let arrowEdge: CloseConfirmationArrowEdge = availableRight >= width || availableRight >= availableLeft
+            ? .left
+            : .right
+        let preferredX = arrowEdge == .left
+            ? anchor.x + anchorGap
+            : anchor.x - width - anchorGap
+        let x = min(
+            max(edgeMargin, preferredX),
+            max(edgeMargin, glassLayer.bounds.width - width - edgeMargin)
+        )
+        let y = min(
+            max(edgeMargin, anchor.y - height + 64),
+            max(edgeMargin, glassLayer.bounds.height - height - edgeMargin)
+        )
+        let localArrowY = min(max(anchor.y - y, 38), height - 38)
+        closeConfirmationArrowEdge = arrowEdge
+
+        let layers = closeConfirmationLayers
+        layers.containerLayer.isHidden = false
+        layers.containerLayer.frame = CGRect(x: x, y: y, width: width, height: height)
+        let contentX = arrowEdge == .left ? arrowWidth : 0
+        let contentFrame = CGRect(x: contentX, y: 0, width: contentWidth, height: height)
+        let bubblePath = closeConfirmationBubblePath(
+            bounds: layers.containerLayer.bounds,
+            contentFrame: contentFrame,
+            arrowEdge: arrowEdge,
+            arrowY: localArrowY
+        )
+        layers.backgroundLayer.frame = layers.containerLayer.bounds
+        layers.backgroundLayer.path = bubblePath
+        layers.containerLayer.shadowPath = bubblePath
+        layers.titleLayer.string = confirmationTitle(for: request)
+        layers.messageLayer.string = confirmationMessage(for: request)
+        layers.titleLayer.frame = CGRect(x: contentFrame.minX + 22, y: height - 48, width: contentFrame.width - 44, height: 22)
+        layers.messageLayer.frame = CGRect(x: contentFrame.minX + 22, y: height - 78, width: contentFrame.width - 44, height: 21)
+
+        layers.checkboxLayer.frame = CGRect(x: contentFrame.minX + 22, y: 80, width: 18, height: 18)
+        layers.checkboxLayer.backgroundColor = (pendingCloseOptOut
+            ? NSColor.controlAccentColor.withAlphaComponent(0.92)
+            : NSColor.clear
+        ).cgColor
+        layers.checkboxLayer.borderColor = (pendingCloseOptOut
+            ? NSColor.controlAccentColor.withAlphaComponent(0.95)
+            : NSColor.separatorColor.withAlphaComponent(0.48)
+        ).cgColor
+        layers.checkboxMarkLayer.string = pendingCloseOptOut ? "✓" : ""
+        layers.checkboxMarkLayer.frame = CGRect(x: 0, y: 1, width: 18, height: 16)
+        layers.checkboxLabelLayer.frame = CGRect(x: contentFrame.minX + 48, y: 80, width: contentFrame.width - 70, height: 19)
+
+        layers.cancelButtonLayer.frame = CGRect(x: contentFrame.maxX - 164, y: 22, width: 74, height: 32)
+        layers.cancelButtonTextLayer.frame = layers.cancelButtonLayer.bounds.insetBy(dx: 0, dy: 7)
+        layers.confirmButtonLayer.frame = CGRect(x: contentFrame.maxX - 78, y: 22, width: 56, height: 32)
+        layers.confirmButtonTextLayer.frame = layers.confirmButtonLayer.bounds.insetBy(dx: 0, dy: 7)
+    }
+
+    private func setCloseFeedback(_ feedback: CloseFeedback, autoHideAfter delay: TimeInterval?) {
+        closeFeedbackHideTask?.cancel()
+        closeFeedback = feedback
+        closeFeedbackLayer.isHidden = false
+        closeFeedbackLayer.opacity = 1
+        closeFeedbackTextLayer.string = feedback.message
+        switch feedback.kind {
+        case .progress:
+            closeFeedbackLayer.backgroundColor = NSColor.windowBackgroundColor.withAlphaComponent(0.94).cgColor
+            closeFeedbackLayer.borderColor = NSColor.separatorColor.withAlphaComponent(0.28).cgColor
+            closeFeedbackTextLayer.foregroundColor = NSColor.secondaryLabelColor.withAlphaComponent(0.96).cgColor
+        case .failure:
+            closeFeedbackLayer.backgroundColor = NSColor.systemRed.withAlphaComponent(0.10).cgColor
+            closeFeedbackLayer.borderColor = NSColor.systemRed.withAlphaComponent(0.32).cgColor
+            closeFeedbackTextLayer.foregroundColor = NSColor.systemRed.withAlphaComponent(0.95).cgColor
+        }
+        needsLayout = true
+
+        guard let delay else {
+            closeFeedbackHideTask = nil
+            return
+        }
+
+        closeFeedbackHideTask = Task { @MainActor [weak self] in
+            try? await Task.sleep(nanoseconds: UInt64(delay * 1_000_000_000))
+            guard !Task.isCancelled,
+                  let self,
+                  self.closeFeedback == feedback
+            else {
+                return
+            }
+            self.clearCloseFeedback()
+        }
+    }
+
+    private func layoutCloseFeedback() {
+        guard let feedback = closeFeedback else {
+            closeFeedbackLayer.isHidden = true
+            closeFeedbackLayer.opacity = 0
+            return
+        }
+
+        closeFeedbackLayer.isHidden = false
+        closeFeedbackLayer.opacity = 1
+        let font = NSFont.systemFont(
+            ofSize: 13,
+            weight: feedback.kind == .failure ? .medium : .regular
+        )
+        closeFeedbackTextLayer.font = font
+        closeFeedbackTextLayer.fontSize = 13
+        let textWidth = (feedback.message as NSString).size(
+            withAttributes: [.font: font]
+        ).width
+        let maxWidth = max(180, glassLayer.bounds.width - 48)
+        let width = min(max(180, textWidth + 34), min(460, maxWidth))
+        let height: CGFloat = 34
+        let x = max(24, (glassLayer.bounds.width - width) / 2)
+        let preferredY = waterfallLayer.frame.maxY - height - 14
+        let y = min(
+            max(16, preferredY),
+            max(16, glassLayer.bounds.height - height - 16)
+        )
+
+        closeFeedbackLayer.frame = CGRect(x: x, y: y, width: width, height: height)
+        closeFeedbackLayer.cornerRadius = height / 2
+        closeFeedbackLayer.shadowPath = CGPath(
+            roundedRect: closeFeedbackLayer.bounds,
+            cornerWidth: closeFeedbackLayer.cornerRadius,
+            cornerHeight: closeFeedbackLayer.cornerRadius,
+            transform: nil
+        )
+        closeFeedbackTextLayer.frame = closeFeedbackLayer.bounds.insetBy(dx: 17, dy: 8)
+    }
+
+    private func closeConfirmationBubblePath(
+        bounds: CGRect,
+        contentFrame: CGRect,
+        arrowEdge: CloseConfirmationArrowEdge,
+        arrowY: CGFloat
+    ) -> CGPath {
+        let cornerRadius: CGFloat = 18
+        let arrowHalfHeight: CGFloat = 10
+        let path = CGMutablePath()
+        let minX = contentFrame.minX
+        let maxX = contentFrame.maxX
+        let minY = contentFrame.minY
+        let maxY = contentFrame.maxY
+        let arrowY = min(max(arrowY, minY + cornerRadius + arrowHalfHeight + 4), maxY - cornerRadius - arrowHalfHeight - 4)
+
+        path.move(to: CGPoint(x: minX + cornerRadius, y: minY))
+        path.addLine(to: CGPoint(x: maxX - cornerRadius, y: minY))
+        path.addQuadCurve(to: CGPoint(x: maxX, y: minY + cornerRadius), control: CGPoint(x: maxX, y: minY))
+
+        if arrowEdge == .right {
+            path.addLine(to: CGPoint(x: maxX, y: arrowY - arrowHalfHeight))
+            path.addLine(to: CGPoint(x: bounds.maxX, y: arrowY))
+            path.addLine(to: CGPoint(x: maxX, y: arrowY + arrowHalfHeight))
+        }
+
+        path.addLine(to: CGPoint(x: maxX, y: maxY - cornerRadius))
+        path.addQuadCurve(to: CGPoint(x: maxX - cornerRadius, y: maxY), control: CGPoint(x: maxX, y: maxY))
+        path.addLine(to: CGPoint(x: minX + cornerRadius, y: maxY))
+        path.addQuadCurve(to: CGPoint(x: minX, y: maxY - cornerRadius), control: CGPoint(x: minX, y: maxY))
+
+        if arrowEdge == .left {
+            path.addLine(to: CGPoint(x: minX, y: arrowY + arrowHalfHeight))
+            path.addLine(to: CGPoint(x: bounds.minX, y: arrowY))
+            path.addLine(to: CGPoint(x: minX, y: arrowY - arrowHalfHeight))
+        }
+
+        path.addLine(to: CGPoint(x: minX, y: minY + cornerRadius))
+        path.addQuadCurve(to: CGPoint(x: minX + cornerRadius, y: minY), control: CGPoint(x: minX, y: minY))
+        path.closeSubpath()
+        return path
+    }
+
+    private func confirmationTitle(for request: QuickSwitchCloseRequest) -> String {
+        switch request {
+        case .app:
+            return "关闭 \(request.appName)?"
+        case .window:
+            return "关闭这个窗口?"
+        }
+    }
+
+    private func confirmationMessage(for request: QuickSwitchCloseRequest) -> String {
+        switch request {
+        case .app:
+            return "将退出该应用,并一次性关闭它的所有窗口。"
+        case .window:
+            return "将关闭此窗口,未保存内容可能需要应用确认。"
+        }
+    }
+
+    private func closeRequest(for target: CloseTarget) -> QuickSwitchCloseRequest? {
+        switch target {
+        case .app(let appGroupIndex):
+            return appShelfItems
+                .first { $0.item.appGroupIndex == appGroupIndex }
+                .map { .app($0.item) }
+        case .window(let appGroupIndex, let windowIndex, let windowID):
+            guard let card = waterfallCard(appGroupIndex: appGroupIndex, windowIndex: windowIndex),
+                  card.item.window.id == windowID
+            else {
+                return nil
+            }
+            return .window(card.item)
+        }
+    }
+
+    private func requestClose(for target: CloseTarget) {
+        guard let request = closeRequest(for: target) else {
+            DevelopmentDiagnostics.log("quickSwitch.view.closeRequest.missingTarget", [
+                "targetKind": target.kindDescription
+            ])
+            return
+        }
+
+        pendingCloseTarget = nil
+        pendingCloseRequest = nil
+        pendingCloseOptOut = false
+        closeConfirmationLayers.containerLayer.isHidden = true
+        closeConfirmationArrowEdge = nil
+        onRequestClose?(request)
+    }
+
+    private func beginCloseConfirmation(for target: CloseTarget) {
+        if closeConfirmationRequired {
+            guard let request = closeRequest(for: target) else {
+                DevelopmentDiagnostics.log("quickSwitch.view.closeConfirmation.missingRequest", [
+                    "targetKind": target.kindDescription
+                ])
+                return
+            }
+            pendingCloseTarget = target
+            pendingCloseRequest = request
+            pendingCloseOptOut = false
+            DevelopmentDiagnostics.log("quickSwitch.view.closeConfirmation.show", [
+                "targetKind": target.kindDescription
+            ])
+            needsLayout = true
+            return
+        }
+
+        requestClose(for: target)
+    }
+
+    private func confirmPendingClose() {
+        guard let target = pendingCloseTarget,
+              let request = pendingCloseRequest
+        else { return }
+        let shouldDisableConfirmation = pendingCloseOptOut
+        pendingCloseTarget = nil
+        pendingCloseRequest = nil
+        pendingCloseOptOut = false
+        closeConfirmationLayers.containerLayer.isHidden = true
+        closeConfirmationArrowEdge = nil
+        if shouldDisableConfirmation && closeConfirmationRequired {
+            closeConfirmationRequired = false
+            onCloseConfirmationDisabled?()
+        }
+        DevelopmentDiagnostics.log("quickSwitch.view.closeConfirmation.confirm", [
+            "targetKind": target.kindDescription,
+            "disableFutureConfirmation": shouldDisableConfirmation
+        ])
+        onRequestClose?(request)
+    }
+
+    private func cancelPendingClose() {
+        DevelopmentDiagnostics.log("quickSwitch.view.closeConfirmation.cancel")
+        pendingCloseTarget = nil
+        pendingCloseRequest = nil
+        pendingCloseOptOut = false
+        closeConfirmationLayers.containerLayer.isHidden = true
+        closeConfirmationArrowEdge = nil
+        needsLayout = true
+    }
+
+    private func toggleCloseConfirmationOptOut() {
+        if pendingCloseOptOut && !closeConfirmationRequired {
+            return
+        }
+        pendingCloseOptOut.toggle()
+        if pendingCloseOptOut {
+            closeConfirmationRequired = false
+            onCloseConfirmationDisabled?()
+            DevelopmentDiagnostics.log("quickSwitch.view.closeConfirmation.optOutPersisted")
+        }
+        needsLayout = true
+    }
+
+    private enum CloseConfirmationHit {
+        case confirm
+        case cancel
+        case checkbox
+        case background
+        case outside
+    }
+
+    private func closeConfirmationHit(at windowLocation: NSPoint) -> CloseConfirmationHit {
+        let location = convert(windowLocation, from: nil)
+        let locationInGlass = CGPoint(
+            x: location.x - glassLayer.frame.minX,
+            y: location.y - glassLayer.frame.minY
+        )
+        let layers = closeConfirmationLayers
+        guard !layers.containerLayer.isHidden else { return .outside }
+        guard layers.containerLayer.frame.contains(locationInGlass) else { return .outside }
+
+        let local = CGPoint(
+            x: locationInGlass.x - layers.containerLayer.frame.minX,
+            y: locationInGlass.y - layers.containerLayer.frame.minY
+        )
+        if layers.confirmButtonLayer.frame.contains(local) {
+            return .confirm
+        }
+        if layers.cancelButtonLayer.frame.contains(local) {
+            return .cancel
+        }
+        let checkboxHitFrame = layers.checkboxLayer.frame.union(layers.checkboxLabelLayer.frame).insetBy(dx: -6, dy: -4)
+        if checkboxHitFrame.contains(local) {
+            return .checkbox
+        }
+        return .background
+    }
+
+    private func handleCloseConfirmationMouseDown(at windowLocation: NSPoint) -> Bool {
+        switch closeConfirmationHit(at: windowLocation) {
+        case .confirm:
+            confirmPendingClose()
+            return true
+        case .cancel:
+            cancelPendingClose()
+            return true
+        case .checkbox:
+            toggleCloseConfirmationOptOut()
+            return true
+        case .background:
+            return true
+        case .outside:
+            if pendingCloseTarget != nil {
+                cancelPendingClose()
+                return true
+            }
+            return false
+        }
+    }
+
+    private func closeButtonTarget(at windowLocation: NSPoint) -> CloseTarget? {
+        if let target = appShelfCloseButtonTarget(at: windowLocation) {
+            return target
+        }
+        return waterfallCloseButtonTarget(at: windowLocation)
+    }
+
+    private func appShelfCloseButtonTarget(at windowLocation: NSPoint) -> CloseTarget? {
+        let locationInView = convert(windowLocation, from: nil)
+        let locationInAppShelfContent = CGPoint(
+            x: locationInView.x - glassLayer.frame.minX - shelfLayer.frame.minX - appShelfContentLayer.frame.minX,
+            y: locationInView.y - glassLayer.frame.minY - shelfLayer.frame.minY - appShelfContentLayer.frame.minY
+        )
+
+        for item in appShelfItems {
+            let target = CloseTarget.app(appGroupIndex: item.item.appGroupIndex)
+            guard item.closeButton.containerLayer.opacity > 0,
+                  canClose(app: item.item.app)
+            else { continue }
+
+            let locationInItem = CGPoint(
+                x: locationInAppShelfContent.x - item.containerLayer.frame.minX,
+                y: locationInAppShelfContent.y - item.containerLayer.frame.minY
+            )
+            if item.closeButton.containerLayer.frame.insetBy(dx: -8, dy: -8).contains(locationInItem) {
+                return target
+            }
+        }
+        return nil
+    }
+
+    private func waterfallCloseButtonTarget(at windowLocation: NSPoint) -> CloseTarget? {
+        let locationInView = convert(windowLocation, from: nil)
+        let locationInWaterfallContent = CGPoint(
+            x: locationInView.x - glassLayer.frame.minX - waterfallLayer.frame.minX - waterfallContentLayer.frame.minX,
+            y: locationInView.y - glassLayer.frame.minY - waterfallLayer.frame.minY - waterfallContentLayer.frame.minY
+        )
+
+        for column in waterfallColumns where column.containerLayer.frame.contains(locationInWaterfallContent) {
+            let locationInColumn = CGPoint(
+                x: locationInWaterfallContent.x - column.containerLayer.frame.minX,
+                y: locationInWaterfallContent.y - column.containerLayer.frame.minY
+            )
+            for card in column.cards where card.containerLayer.frame.contains(locationInColumn) {
+                guard card.closeButton.containerLayer.opacity > 0 else { continue }
+                let locationInCard = CGPoint(
+                    x: locationInColumn.x - card.containerLayer.frame.minX,
+                    y: locationInColumn.y - card.containerLayer.frame.minY
+                )
+                if card.closeButton.containerLayer.frame.insetBy(dx: -8, dy: -8).contains(locationInCard) {
+                    return .window(
+                        appGroupIndex: card.item.appGroupIndex,
+                        windowIndex: card.item.windowIndex,
+                        windowID: card.item.window.id
+                    )
+                }
+            }
+        }
+        return nil
+    }
+
+    private func closeConfirmationAnchor(for target: CloseTarget) -> CGPoint? {
+        switch target {
+        case .app(let appGroupIndex):
+            guard let item = appShelfItems.first(where: { $0.item.appGroupIndex == appGroupIndex }) else {
+                return nil
+            }
+            return CGPoint(
+                x: shelfLayer.frame.minX
+                    + appShelfContentLayer.frame.minX
+                    + item.containerLayer.frame.minX
+                    + item.closeButton.containerLayer.frame.midX,
+                y: shelfLayer.frame.minY
+                    + appShelfContentLayer.frame.minY
+                    + item.containerLayer.frame.minY
+                    + item.closeButton.containerLayer.frame.midY
+            )
+        case .window(let appGroupIndex, let windowIndex, let windowID):
+            guard let column = waterfallColumns.first(where: { $0.column.appGroupIndex == appGroupIndex }),
+                  let card = column.cards.first(where: {
+                      $0.item.windowIndex == windowIndex && $0.item.window.id == windowID
+                  })
+            else {
+                return nil
+            }
+            return CGPoint(
+                x: waterfallLayer.frame.minX
+                    + waterfallContentLayer.frame.minX
+                    + column.containerLayer.frame.minX
+                    + card.containerLayer.frame.minX
+                    + card.closeButton.containerLayer.frame.midX,
+                y: waterfallLayer.frame.minY
+                    + waterfallContentLayer.frame.minY
+                    + column.containerLayer.frame.minY
+                    + card.containerLayer.frame.minY
+                    + card.closeButton.containerLayer.frame.midY
+            )
+        }
+    }
+
+    private func accentTintedWindowBackground(fraction: CGFloat, alpha: CGFloat) -> NSColor {
+        let color = NSColor.windowBackgroundColor.blended(withFraction: fraction, of: NSColor.controlAccentColor)
+            ?? NSColor.windowBackgroundColor
+        return color.withAlphaComponent(alpha)
+    }
+
+    private func isWaterfallCardSpaceFocused(_ card: WaterfallCardLayers) -> Bool {
+        guard let activeSpaceFocusID else { return false }
+        return card.item.primarySpaceID == activeSpaceFocusID
     }
 
     private func waterfallColumnWidth() -> CGFloat {
@@ -2138,7 +4729,7 @@
         let visibleColumns = min(4, max(1, waterfallColumns.count))
         let fittingWidth = (
             waterfallLayer.bounds.width
-                - WaterfallMetrics.columnPadding * 2
+                - WaterfallMetrics.contentHorizontalPadding * 2
                 - CGFloat(max(0, visibleColumns - 1)) * WaterfallMetrics.gap
         ) / CGFloat(visibleColumns)
         return max(
@@ -2147,15 +4738,67 @@
         )
     }
 
+    private var isHorizontalMasonryMode: Bool {
+        waterfallViewMode == .horizontalMasonry
+    }
+
+    private var nextWaterfallViewMode: QuickSwitchWaterfallViewMode {
+        isHorizontalMasonryMode ? .verticalColumns : .horizontalMasonry
+    }
+
+    private var viewModeToggleBlueColor: NSColor {
+        NSColor(deviceRed: 135.0 / 255.0, green: 200.0 / 255.0, blue: 1, alpha: 1)
+    }
+
+    private var viewModeToggleVisualState: ViewModeToggleVisualState {
+        if isHorizontalMasonryMode {
+            return isViewModeToggleButtonHovered ? .verticalAvailable : .horizontalSelected
+        }
+        return isViewModeToggleButtonHovered ? .horizontalAvailable : .verticalSelected
+    }
+
+    private func viewModeToggleVisualStateIsSelected(_ state: ViewModeToggleVisualState) -> Bool {
+        switch state {
+        case .horizontalSelected, .verticalSelected:
+            return true
+        case .horizontalAvailable, .verticalAvailable:
+            return false
+        }
+    }
+
+    private var viewModeToggleIconKind: String {
+        viewModeToggleVisualState.rawValue
+    }
+
+    private var viewModeToggleAccessibilityLabel: String {
+        switch nextWaterfallViewMode {
+        case .verticalColumns:
+            return "切换到纵栏瀑布"
+        case .horizontalMasonry:
+            return "切换到横栏瀑布"
+        }
+    }
+
     private var waterfallMaxScrollOffset: CGFloat {
-        max(0, waterfallContentWidth - waterfallLayer.bounds.width)
+        guard !isHorizontalMasonryMode else { return 0 }
+        return max(0, waterfallContentWidth - waterfallLayer.bounds.width)
     }
 
     private func clampedWaterfallOffset(_ offset: CGFloat) -> CGFloat {
         min(max(0, offset), waterfallMaxScrollOffset)
     }
 
+    private var horizontalMasonryMaxScrollOffset: CGFloat {
+        max(0, horizontalMasonryContentHeight - waterfallLayer.bounds.height)
+    }
+
+    private func clampedHorizontalMasonryOffset(_ offset: CGFloat) -> CGFloat {
+        min(max(0, offset), horizontalMasonryMaxScrollOffset)
+    }
+
     private func waterfallMaxVerticalScrollOffset(for appGroupIndex: Int) -> CGFloat {
+        guard !isHorizontalMasonryMode else { return 0 }
+
         guard
             let column = waterfallColumns.first(where: { $0.column.appGroupIndex == appGroupIndex })
         else {
@@ -2166,7 +4809,7 @@
             1,
             waterfallLayer.bounds.height
                 - WaterfallMetrics.headerHeight
-                - WaterfallMetrics.columnPadding * 2
+                - WaterfallMetrics.columnVerticalPadding * 2
         )
         let contentHeight = CGFloat(column.cards.count) * WaterfallMetrics.cardHeight
             + CGFloat(max(0, column.cards.count - 1)) * WaterfallMetrics.cardGap
@@ -2196,24 +4839,63 @@
         return states.joined(separator: " / ")
     }
 
-    private func spaceColor(for space: QuickSwitchSpaceViewModel) -> NSColor {
-        if space.isCurrent {
-            return NSColor.windowBackgroundColor.withAlphaComponent(0.76)
-        }
-        if space.windowCount > 0 {
-            return NSColor.controlBackgroundColor.withAlphaComponent(0.56)
+    private var spaceLaneOccupiedColor: NSColor {
+        if effectiveAppearance.bestMatch(from: [.darkAqua, .aqua]) == .darkAqua {
+            return NSColor(calibratedRed: 10 / 255, green: 132 / 255, blue: 1, alpha: 1)
         }
 
-        return NSColor.controlBackgroundColor.withAlphaComponent(0.26)
+        return NSColor(calibratedRed: 0, green: 122 / 255, blue: 1, alpha: 1)
+    }
+
+    private var spaceLaneLockedFillColor: NSColor {
+        if effectiveAppearance.bestMatch(from: [.darkAqua, .aqua]) == .darkAqua {
+            return NSColor(calibratedRed: 58 / 255, green: 148 / 255, blue: 1, alpha: 0.86)
+        }
+
+        return NSColor(calibratedRed: 90 / 255, green: 171 / 255, blue: 1, alpha: 0.82)
+    }
+
+    private func spaceLaneIdleOccupiedGradientColors() -> [NSColor] {
+        if effectiveAppearance.bestMatch(from: [.darkAqua, .aqua]) == .darkAqua {
+            let blue = NSColor(calibratedRed: 36 / 255, green: 54 / 255, blue: 72 / 255, alpha: 1)
+            let surface = NSColor.windowBackgroundColor.withAlphaComponent(1)
+            return [blue, surface]
+        }
+
+        return [
+            NSColor(calibratedRed: 232 / 255, green: 246 / 255, blue: 1, alpha: 1),
+            NSColor.white
+        ]
+    }
+
+    private func applySpaceLaneGradientFill(to layer: CALayer, colors: [NSColor]) {
+        if let gradientLayer = layer as? CAGradientLayer {
+            gradientLayer.colors = colors.map(\.cgColor)
+            gradientLayer.locations = [0, 1]
+            gradientLayer.startPoint = CGPoint(x: 0.5, y: 1.0)
+            gradientLayer.endPoint = CGPoint(x: 0.5, y: 0.0)
+        }
+        layer.backgroundColor = NSColor.clear.cgColor
+    }
+
+    private func applySpaceLaneSolidFill(to layer: CALayer, color: NSColor) {
+        if let gradientLayer = layer as? CAGradientLayer {
+            gradientLayer.colors = nil
+            gradientLayer.locations = nil
+        }
+        layer.backgroundColor = color.cgColor
     }
 
     private func makeFullscreenMarkerLayer(for space: QuickSwitchSpaceViewModel) -> CALayer? {
         guard space.type == .fullscreen else { return nil }
 
-        let layer = CALayer()
-        layer.cornerRadius = 1.5
-        layer.backgroundColor = NSColor.secondaryLabelColor.withAlphaComponent(space.isCurrent ? 0.46 : 0.32).cgColor
-        return layer
+        let shapeLayer = CAShapeLayer()
+        shapeLayer.fillColor = NSColor.clear.cgColor
+        shapeLayer.strokeColor = NSColor.secondaryLabelColor.withAlphaComponent(space.isCurrent ? 0.42 : 0.28).cgColor
+        shapeLayer.lineWidth = 1.2
+        shapeLayer.lineCap = .round
+        shapeLayer.lineJoin = .round
+        return shapeLayer
     }
 
     private func makeTextLayer(
@@ -2234,31 +4916,234 @@
         return textLayer
     }
 
+    private func makeCloseButtonLayers() -> CloseButtonLayers {
+        let container = CALayer()
+        container.cornerRadius = 8
+        container.masksToBounds = false
+        container.backgroundColor = NSColor.systemRed.withAlphaComponent(0.92).cgColor
+        container.borderColor = NSColor.white.withAlphaComponent(0.72).cgColor
+        container.borderWidth = 0.8
+        container.shadowColor = NSColor.black.cgColor
+        container.shadowOpacity = 0.14
+        container.shadowRadius = 5
+        container.shadowOffset = CGSize(width: 0, height: -1)
+        container.opacity = 0
+
+        let glyph = CAShapeLayer()
+        glyph.contentsScale = backingScaleFactor
+        glyph.strokeColor = NSColor.white.cgColor
+        glyph.fillColor = NSColor.clear.cgColor
+        glyph.lineCap = .round
+        glyph.lineJoin = .round
+        container.addSublayer(glyph)
+
+        return CloseButtonLayers(containerLayer: container, glyphLayer: glyph)
+    }
+
+    private func makeCloseConfirmationLayers() -> CloseConfirmationLayers {
+        let container = CALayer()
+        container.masksToBounds = false
+        container.backgroundColor = NSColor.clear.cgColor
+        container.shadowColor = NSColor.black.cgColor
+        container.shadowOpacity = 0.20
+        container.shadowRadius = 20
+        container.shadowOffset = CGSize(width: 0, height: -8)
+        container.zPosition = 200
+
+        let background = CAShapeLayer()
+        background.contentsScale = backingScaleFactor
+        background.fillColor = NSColor.windowBackgroundColor.withAlphaComponent(0.985).cgColor
+        background.strokeColor = NSColor.separatorColor.withAlphaComponent(0.36).cgColor
+        background.lineWidth = 1
+
+        let title = makeTextLayer(
+            string: "",
+            fontSize: 15,
+            weight: .semibold,
+            color: .labelColor
+        )
+        let message = makeTextLayer(
+            string: "",
+            fontSize: 13,
+            weight: .regular,
+            color: .secondaryLabelColor
+        )
+        message.truncationMode = .end
+
+        let checkbox = CALayer()
+        checkbox.cornerRadius = 4
+        checkbox.borderWidth = 1
+        checkbox.borderColor = NSColor.separatorColor.withAlphaComponent(0.48).cgColor
+        checkbox.backgroundColor = NSColor.clear.cgColor
+
+        let checkmark = makeTextLayer(
+            string: "",
+            fontSize: 11,
+            weight: .bold,
+            color: .white,
+            alignment: .center
+        )
+
+        let checkboxLabel = makeTextLayer(
+            string: "以后不再提醒",
+            fontSize: 13,
+            weight: .regular,
+            color: .secondaryLabelColor
+        )
+
+        let confirmButton = CALayer()
+        confirmButton.cornerRadius = 7
+        confirmButton.backgroundColor = NSColor.systemRed.withAlphaComponent(0.94).cgColor
+
+        let confirmText = makeTextLayer(
+            string: "关闭",
+            fontSize: 13,
+            weight: .semibold,
+            color: .white,
+            alignment: .center
+        )
+
+        let cancelButton = CALayer()
+        cancelButton.cornerRadius = 7
+        cancelButton.backgroundColor = NSColor.systemFill.withAlphaComponent(0.16).cgColor
+        cancelButton.borderColor = NSColor.separatorColor.withAlphaComponent(0.22).cgColor
+        cancelButton.borderWidth = 1
+
+        let cancelText = makeTextLayer(
+            string: "取消",
+            fontSize: 13,
+            weight: .medium,
+            color: .labelColor,
+            alignment: .center
+        )
+
+        container.addSublayer(background)
+        container.addSublayer(title)
+        container.addSublayer(message)
+        container.addSublayer(checkbox)
+        checkbox.addSublayer(checkmark)
+        container.addSublayer(checkboxLabel)
+        container.addSublayer(confirmButton)
+        confirmButton.addSublayer(confirmText)
+        container.addSublayer(cancelButton)
+        cancelButton.addSublayer(cancelText)
+
+        return CloseConfirmationLayers(
+            containerLayer: container,
+            backgroundLayer: background,
+            titleLayer: title,
+            messageLayer: message,
+            checkboxLayer: checkbox,
+            checkboxMarkLayer: checkmark,
+            checkboxLabelLayer: checkboxLabel,
+            confirmButtonLayer: confirmButton,
+            confirmButtonTextLayer: confirmText,
+            cancelButtonLayer: cancelButton,
+            cancelButtonTextLayer: cancelText
+        )
+    }
+
     private func makeWindowBlocks(count: Int, space: QuickSwitchSpaceViewModel) -> [CALayer] {
         guard count > 0 else { return [] }
 
         return (0..<count).map { _ in
             let layer = CALayer()
             layer.cornerRadius = 3
-            layer.backgroundColor = (space.type == .fullscreen
-                ? NSColor.labelColor.withAlphaComponent(0.20)
-                : NSColor.labelColor.withAlphaComponent(0.18)
-            ).cgColor
+            layer.backgroundColor = spaceLaneOccupiedColor
+                .withAlphaComponent(space.isCurrent ? 0.72 : 0.58)
+                .cgColor
             return layer
         }
     }
 
-    private func appIdentifierText(for appNames: [String]) -> String {
-        var identifiers = appNames.prefix(3).compactMap { name -> String? in
+    private func appIdentifierText(for space: QuickSwitchSpaceViewModel) -> String {
+        if space.type == .fullscreen,
+           let appName = space.appNames.first?.trimmingCharacters(in: .whitespacesAndNewlines),
+           !appName.isEmpty {
+            return appName
+        }
+
+        var identifiers = space.appNames.prefix(3).compactMap { name -> String? in
             let trimmed = name.trimmingCharacters(in: .whitespacesAndNewlines)
             return trimmed.first.map { String($0) }
         }
 
-        if appNames.count > 3 {
-            identifiers.append("+\(appNames.count - 3)")
+        if space.appNames.count > 3 {
+            identifiers.append("+\(space.appNames.count - 3)")
         }
 
         return identifiers.joined(separator: " ")
+    }
+
+    private func splitViewAppNames(for space: QuickSwitchSpaceViewModel) -> [String] {
+        guard space.type == .fullscreen else { return [] }
+
+        let names = space.splitViewAppNames
+            .prefix(2)
+            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
+            .filter { !$0.isEmpty }
+
+        guard names.count >= 2 else { return [] }
+        return names
+    }
+
+    private func layoutFullscreenMarkerLayer(
+        _ layer: CALayer,
+        in segmentBounds: CGRect,
+        isSplitView: Bool = false
+    ) {
+        let markerFrame = fullscreenMarkerFrame(in: segmentBounds)
+        layer.frame = markerFrame
+
+        guard let shapeLayer = layer as? CAShapeLayer else { return }
+
+        let bounds = shapeLayer.bounds
+        if isSplitView {
+            let path = CGMutablePath()
+            path.move(to: CGPoint(x: bounds.midX, y: bounds.minY))
+            path.addLine(to: CGPoint(x: bounds.midX, y: bounds.maxY))
+            shapeLayer.path = path
+            shapeLayer.lineCap = .butt
+            return
+        }
+
+        let cornerLength = min(12, max(7, min(bounds.width, bounds.height) * 0.28))
+        let path = CGMutablePath()
+
+        path.move(to: CGPoint(x: 0, y: cornerLength))
+        path.addLine(to: CGPoint(x: 0, y: 0))
+        path.addLine(to: CGPoint(x: cornerLength, y: 0))
+
+        path.move(to: CGPoint(x: bounds.maxX - cornerLength, y: 0))
+        path.addLine(to: CGPoint(x: bounds.maxX, y: 0))
+        path.addLine(to: CGPoint(x: bounds.maxX, y: cornerLength))
+
+        path.move(to: CGPoint(x: bounds.maxX, y: bounds.maxY - cornerLength))
+        path.addLine(to: CGPoint(x: bounds.maxX, y: bounds.maxY))
+        path.addLine(to: CGPoint(x: bounds.maxX - cornerLength, y: bounds.maxY))
+
+        path.move(to: CGPoint(x: cornerLength, y: bounds.maxY))
+        path.addLine(to: CGPoint(x: 0, y: bounds.maxY))
+        path.addLine(to: CGPoint(x: 0, y: bounds.maxY - cornerLength))
+
+        shapeLayer.path = path
+        shapeLayer.lineCap = .round
+    }
+
+    private func fullscreenMarkerFrame(in segmentBounds: CGRect) -> CGRect {
+        let topReserved: CGFloat = 32
+        let bottomReserved: CGFloat = 16
+        let availableHeight = max(20, segmentBounds.height - topReserved - bottomReserved)
+        let markerHeight = min(30, max(20, availableHeight))
+        let markerCenterY = bottomReserved + availableHeight * 0.5
+        let markerY = max(8, min(segmentBounds.height - topReserved - markerHeight, markerCenterY - markerHeight * 0.5))
+
+        return CGRect(
+            x: 10,
+            y: markerY,
+            width: max(1, segmentBounds.width - 20),
+            height: markerHeight
+        )
     }
 
     private func columnSelectionHistoryReports() -> [[String: Int]] {
@@ -2292,20 +5177,35 @@
                 "frame": dictionary(from: item.containerLayer.frame),
                 "visibleFrame": dictionary(from: visibleFrame),
                 "iconFrame": dictionary(from: item.iconLayer.frame),
+                "indexText": item.indexLayer.string ?? "",
+                "indexFrame": dictionary(from: item.indexLayer.frame),
+                "indexVisible": !item.indexLayer.isHidden && item.indexLayer.opacity > 0,
+                "indexFontSize": Double(item.indexLayer.fontSize),
+                "indexColor": colorDictionary(from: item.indexLayer.foregroundColor),
                 "labelFrame": dictionary(from: item.labelLayer.frame),
                 "labelTruncationMode": "middle",
                 "badgeVisible": !item.badgeLayer.isHidden,
-                "badgeText": item.badgeLayer.string ?? ""
+                "badgeText": item.badgeLayer.string ?? "",
+                "closeButtonVisible": item.closeButton.containerLayer.opacity > 0,
+                "closeButtonFrame": dictionary(from: item.closeButton.containerLayer.frame),
+                "closeButtonSize": Double(item.closeButton.containerLayer.bounds.width),
+                "closeButtonFillColor": colorDictionary(from: item.closeButton.containerLayer.backgroundColor),
+                "closeButtonGlyphColor": colorDictionary(from: item.closeButton.glyphLayer.strokeColor),
+                "closeButtonGlyphLineWidth": Double(item.closeButton.glyphLayer.lineWidth)
             ] as [String: Any]
         }
     }
 
     private func appShelfVisualStates(for item: AppShelfItemLayers) -> [String] {
         var states: [String] = []
-        if item.item.appGroupIndex == effectiveSelection?.appGroupIndex {
+        let isSelected = item.item.appGroupIndex == effectiveSelection?.appGroupIndex
+        let isHovered = item.item.appGroupIndex == effectiveHoveredAppGroupIndex
+        if shouldShowSelectedVisual(isSelected: isSelected, isHovered: isHovered) {
             states.append("selected")
+        } else if isSelected {
+            states.append("selectedVisualSuppressed")
         }
-        if item.item.appGroupIndex == effectiveHoveredAppGroupIndex {
+        if isHovered {
             states.append("hover")
         }
         if spaceFocusWindowCount(for: item.item.appGroupIndex) > 0 {
@@ -2318,21 +5218,51 @@
         return states
     }
 
+    private func waterfallColumnVisualStates(for column: WaterfallColumnLayers) -> [String] {
+        var states: [String] = []
+        if column.column.appGroupIndex == effectiveHoveredAppGroupIndex {
+            states.append("hover")
+        }
+        if spaceFocusWindowCount(for: column.column.appGroupIndex) > 0 {
+            states.append("spaceFocused")
+        }
+        return states
+    }
+
     private func waterfallColumnReports() -> [[String: Any]] {
         waterfallColumns.map { column in
             let visibleFrame = column.containerLayer.frame.offsetBy(dx: waterfallContentLayer.frame.minX, dy: 0)
             let appGroupIndex = column.column.appGroupIndex
+            let isHovered = appGroupIndex == effectiveHoveredAppGroupIndex
+            let firstCardFrame = column.cards.first?.containerLayer.frame
+            let headerToFirstCardGap = firstCardFrame.map {
+                column.headerLayer.frame.minY - $0.maxY
+            }
+            let topToFirstCardGap = firstCardFrame.map {
+                column.containerLayer.bounds.height - $0.maxY
+            }
 
             return [
                 "appGroupIndex": appGroupIndex,
                 "appName": column.column.app.name,
                 "bundleIdentifier": column.column.app.bundleIdentifier,
                 "windowCount": column.column.windows.count,
+                "isHovered": isHovered,
+                "visualStates": waterfallColumnVisualStates(for: column),
                 "spaceFocusWindowCount": spaceFocusWindowCount(for: appGroupIndex),
                 "isSpaceFocused": spaceFocusWindowCount(for: appGroupIndex) > 0,
                 "spaceFocusDirection": spaceFocusDirection(for: appGroupIndex),
                 "frame": dictionary(from: column.containerLayer.frame),
                 "visibleFrame": dictionary(from: visibleFrame),
+                "headerFrame": dictionary(from: column.headerLayer.frame),
+                "headerBackgroundColor": colorDictionary(from: column.headerLayer.backgroundColor),
+                "headerToFirstCardGap": headerToFirstCardGap.map(Double.init) ?? NSNull(),
+                "topToFirstCardGap": topToFirstCardGap.map(Double.init) ?? NSNull(),
+                "appNameFrame": dictionary(from: column.appNameLayer.frame),
+                "appNameAlignment": column.appNameLayer.alignmentMode.rawValue,
+                "appNameColor": colorDictionary(from: column.appNameLayer.foregroundColor),
+                "countFrame": dictionary(from: column.countLayer.frame),
+                "countColor": colorDictionary(from: column.countLayer.foregroundColor),
                 "verticalScrollOffset": Double(waterfallColumnScrollOffsets[appGroupIndex] ?? 0),
                 "maxVerticalScrollOffset": Double(waterfallMaxVerticalScrollOffset(for: appGroupIndex)),
                 "cards": waterfallCardReports(for: column)
@@ -2414,8 +5344,23 @@
                 "screenshotSource": screenshotSourceString(screenshotSource, for: card.item.window),
                 "screenshotFallbackReason": screenshotFallbackReasonString(screenshotSource),
                 "screenshotNotRequestedReason": screenshotSkippedReasonsByWindowID[card.item.window.id] ?? NSNull(),
+                "backgroundColor": colorDictionary(from: card.containerLayer.backgroundColor),
+                "shadowOpacity": Double(card.containerLayer.shadowOpacity),
+                "shadowRadius": Double(card.containerLayer.shadowRadius),
                 "thumbnailFrame": dictionary(from: card.thumbnailLayer.frame),
+                "titleBarFrame": dictionary(from: card.titleBarLayer.frame),
+                "titleBarBackgroundColor": colorDictionary(from: card.titleBarLayer.backgroundColor),
+                "titleBarBorderWidth": Double(card.titleBarLayer.borderWidth),
+                "titleFrame": dictionary(from: card.titleLayer.frame),
+                "metaFrame": dictionary(from: card.metaLayer.frame),
                 "appIconFrame": dictionary(from: card.appIconLayer.frame),
+                "stateFrame": dictionary(from: card.stateLayer.frame),
+                "closeButtonVisible": card.closeButton.containerLayer.opacity > 0,
+                "closeButtonFrame": dictionary(from: card.closeButton.containerLayer.frame),
+                "closeButtonSize": Double(card.closeButton.containerLayer.bounds.width),
+                "closeButtonFillColor": colorDictionary(from: card.closeButton.containerLayer.backgroundColor),
+                "closeButtonGlyphColor": colorDictionary(from: card.closeButton.glyphLayer.strokeColor),
+                "closeButtonGlyphLineWidth": Double(card.closeButton.glyphLayer.lineWidth),
                 "shineVisible": card.shineLayer.opacity > 0,
                 "zPosition": Double(card.containerLayer.zPosition),
                 "frame": dictionary(from: card.containerLayer.frame),
@@ -2510,13 +5455,22 @@
 
     private func waterfallCardVisualStates(for card: WaterfallCardLayers) -> [String] {
         var states: [String] = []
-        if card.item.window.id == effectiveSelection?.windowID {
+        let isSelected = card.item.window.id == effectiveSelection?.windowID
+        let isHovered = card.item.window.id == hoveredWindowID
+        let isAppLinked = isHorizontalMasonryMode
+            && card.item.appGroupIndex == appIconHoverLinkedAppGroupIndex
+        if shouldShowSelectedVisual(isSelected: isSelected, isHovered: isHovered) {
             states.append("selected")
+        } else if isSelected {
+            states.append("selectedVisualSuppressed")
         }
-        if card.item.window.id == hoveredWindowID {
+        if isHovered {
             states.append("hover")
         }
-        if card.item.primarySpaceID == activeSpaceFocusID {
+        if isAppLinked {
+            states.append("appLinked")
+        }
+        if isWaterfallCardSpaceFocused(card) {
             states.append("spaceFocused")
         }
         if card.item.window.isMinimized {
@@ -2532,25 +5486,105 @@
         window?.backingScaleFactor ?? NSScreen.main?.backingScaleFactor ?? 2
     }
 
+    private func spaceLaneDisplayGroupReports() -> [[String: Any]] {
+        spaceLaneDisplayGroups.map { group in
+            let visibleFrame = group.containerLayer.frame.offsetBy(dx: spaceLaneContentLayer.frame.minX, dy: 0)
+            return [
+                "displayUUID": group.display.displayUUID,
+                "displayIndex": group.display.displayIndex,
+                "displayLabel": group.display.displayLabel,
+                "physical": group.display.physical,
+                "spaceCount": group.segments.count,
+                "spaceIDs": group.segments.map(\.space.id),
+                "spaceLabels": group.segments.map(\.space.label),
+                "frame": dictionary(from: group.containerLayer.frame),
+                "visibleFrame": dictionary(from: visibleFrame),
+                "backgroundColor": colorDictionary(from: group.containerLayer.backgroundColor),
+                "borderColor": colorDictionary(from: group.containerLayer.borderColor),
+                "borderWidth": Double(group.containerLayer.borderWidth),
+                "shadowOpacity": Double(group.containerLayer.shadowOpacity),
+                "shadowRadius": Double(group.containerLayer.shadowRadius),
+                "groupGap": Double(SpaceLaneMetrics.groupGap),
+                "groupHorizontalPadding": Double(SpaceLaneMetrics.groupHorizontalPadding),
+                "groupVerticalPadding": Double(SpaceLaneMetrics.groupVerticalPadding),
+                "segmentGap": Double(SpaceLaneMetrics.segmentGap)
+            ] as [String: Any]
+        }
+    }
+
     private func spaceLaneSegmentReports() -> [[String: Any]] {
         currentViewModel?.displays.flatMap { display in
             display.spaces.compactMap { space in
                 guard let segment = spaceLaneSegments.first(where: { $0.space.id == space.id }) else {
                     return nil
                 }
-                let visibleFrame = segment.containerLayer.frame.offsetBy(dx: spaceLaneContentLayer.frame.minX, dy: 0)
+                let isAppAssociated = appHoverAssociatedSpaceIDs.contains(space.id)
+                let isWindowAssociated = space.id == windowHoverAssociatedSpaceID
+                let group = spaceLaneDisplayGroup(containingSpaceID: space.id)
+                let visibleFrame = segment.containerLayer.frame.offsetBy(
+                    dx: (group?.containerLayer.frame.minX ?? 0) + spaceLaneContentLayer.frame.minX,
+                    dy: group?.containerLayer.frame.minY ?? 0
+                )
+                let fullscreenMarkerFrame = segment.fullscreenMarkerLayer?.frame
+                let fullscreenMarkerCenterRatio = fullscreenMarkerFrame.map {
+                    Double($0.midY / max(1, segment.containerLayer.bounds.height))
+                }
+                let splitAppNames = splitViewAppNames(for: space)
+                let splitAppLabelFrames = segment.splitAppLayers.map { dictionary(from: $0.frame) }
                 return [
                     "displayUUID": display.displayUUID,
                     "displayLabel": display.displayLabel,
+                    "spaceID": space.id,
                     "label": space.label,
                     "type": spaceTypeName(space.type),
                     "visualStates": visualStates(for: space),
                     "fullscreenMarkerVisible": segment.fullscreenMarkerLayer != nil,
+                    "fullscreenMarkerKind": fullscreenMarkerKind(
+                        markerLayer: segment.fullscreenMarkerLayer,
+                        splitAppNames: splitAppNames
+                    ),
+                    "fullscreenMarkerPathStyle": fullscreenMarkerPathStyle(
+                        markerLayer: segment.fullscreenMarkerLayer,
+                        splitAppNames: splitAppNames
+                    ),
+                    "fullscreenMarkerFrame": fullscreenMarkerFrame.map { dictionary(from: $0) } ?? NSNull(),
+                    "fullscreenMarkerCenterRatio": fullscreenMarkerCenterRatio ?? NSNull(),
+                    "splitViewAppNames": splitAppNames,
+                    "splitViewLabelFrames": splitAppLabelFrames,
+                    "splitViewLabelColors": segment.splitAppLayers.map {
+                        colorDictionary(from: $0.foregroundColor)
+                    },
+                    "windowBlockCount": segment.windowBlocks.count,
+                    "windowBlockColors": segment.windowBlocks.map { colorDictionary(from: $0.backgroundColor) },
+                    "windowBlockFrames": segment.windowBlocks.map { dictionary(from: $0.frame) },
+                    "labelColor": colorDictionary(from: segment.labelLayer.foregroundColor),
+                    "countText": string(from: segment.countLayer.string),
+                    "countVisible": !segment.countLayer.isHidden && segment.countLayer.opacity > 0,
+                    "countColor": colorDictionary(from: segment.countLayer.foregroundColor),
+                    "appColor": colorDictionary(from: segment.appLayer.foregroundColor),
+                    "fullscreenMarkerStrokeColor": colorDictionary(
+                        from: (segment.fullscreenMarkerLayer as? CAShapeLayer)?.strokeColor
+                    ),
+                    "backgroundKind": spaceLaneFillKind(for: segment.containerLayer),
+                    "backgroundColor": colorDictionary(from: segment.containerLayer.backgroundColor),
+                    "gradientColors": gradientColorDictionaries(from: segment.containerLayer),
+                    "borderColor": colorDictionary(from: segment.containerLayer.borderColor),
+                    "borderWidth": Double(segment.containerLayer.borderWidth),
+                    "shadowColor": colorDictionary(from: segment.containerLayer.shadowColor),
+                    "shadowOpacity": Double(segment.containerLayer.shadowOpacity),
+                    "shadowRadius": Double(segment.containerLayer.shadowRadius),
+                    "shadowOffset": [
+                        "width": Double(segment.containerLayer.shadowOffset.width),
+                        "height": Double(segment.containerLayer.shadowOffset.height)
+                    ],
+                    "appFrame": dictionary(from: segment.appLayer.frame),
                     "frame": dictionary(from: segment.containerLayer.frame),
                     "visibleFrame": dictionary(from: visibleFrame),
                     "isCurrent": space.isCurrent,
-                    "isHovered": space.id == hoveredSpaceID,
+                    "isHovered": space.id == activeSpaceFocusID,
                     "isFocused": space.id == activeSpaceFocusID,
+                    "isAppAssociated": isAppAssociated,
+                    "isWindowAssociated": isWindowAssociated,
                     "windowCount": space.windowCount,
                     "appCount": space.appCount,
                     "appNames": space.appNames
@@ -2559,19 +5593,47 @@
         } ?? []
     }
 
+    private func spaceLaneDisplayGroup(containingSpaceID spaceID: UInt64) -> SpaceLaneDisplayGroupLayers? {
+        spaceLaneDisplayGroups.first { group in
+            group.segments.contains { $0.space.id == spaceID }
+        }
+    }
+
+    private func fullscreenMarkerKind(markerLayer: CALayer?, splitAppNames: [String]) -> String {
+        guard markerLayer != nil else { return "none" }
+        return splitAppNames.count >= 2 ? "splitViewPair" : "cornerBracket"
+    }
+
+    private func fullscreenMarkerPathStyle(markerLayer: CALayer?, splitAppNames: [String]) -> String {
+        guard markerLayer != nil else { return "none" }
+        return splitAppNames.count >= 2 ? "centerDividerOnly" : "cornerBracket"
+    }
+
     private func visualStates(for space: QuickSwitchSpaceViewModel) -> [String] {
         var states: [String] = []
         if space.isCurrent {
             states.append("current")
         }
-        if space.id == hoveredSpaceID {
+        if appHoverAssociatedSpaceIDs.contains(space.id) {
+            states.append("appAssociated")
+        }
+        if space.id == windowHoverAssociatedSpaceID {
+            states.append("windowAssociated")
+        }
+        if space.id == activeSpaceFocusID {
             states.append("hover")
         }
         if space.id == activeSpaceFocusID {
             states.append("focused")
         }
+        if space.id == currentViewModel?.lockedSpaceID {
+            states.append("locked")
+        }
         if space.type == .fullscreen {
             states.append("fullscreen")
+        }
+        if splitViewAppNames(for: space).count >= 2 {
+            states.append("splitView")
         }
         return states
     }
@@ -2597,4 +5659,53 @@
             "height": Double(rect.height)
         ]
     }
+
+    private func string(from textLayerValue: Any?) -> String {
+        if let string = textLayerValue as? String {
+            return string
+        }
+        if let attributedString = textLayerValue as? NSAttributedString {
+            return attributedString.string
+        }
+        return ""
+    }
+
+    private func colorDictionary(from color: CGColor?) -> [String: Double] {
+        guard let color,
+              let nsColor = NSColor(cgColor: color)?.usingColorSpace(.deviceRGB)
+        else {
+            return [
+                "red": 0,
+                "green": 0,
+                "blue": 0,
+                "alpha": 0
+            ]
+        }
+
+        return [
+            "red": Double(nsColor.redComponent),
+            "green": Double(nsColor.greenComponent),
+            "blue": Double(nsColor.blueComponent),
+            "alpha": Double(nsColor.alphaComponent)
+        ]
+    }
+
+    private func gradientColorDictionaries(from layer: CALayer) -> [[String: Double]] {
+        guard let gradientLayer = layer as? CAGradientLayer else { return [] }
+        return (gradientLayer.colors ?? []).map { color in
+            let cgColor = color as! CGColor
+            return colorDictionary(from: cgColor)
+        }
+    }
+
+    private func spaceLaneFillKind(for layer: CALayer) -> String {
+        if !gradientColorDictionaries(from: layer).isEmpty {
+            return "gradient"
+        }
+        let background = colorDictionary(from: layer.backgroundColor)
+        if background["alpha", default: 0] <= 0.01 {
+            return "clear"
+        }
+        return "solid"
+    }
 }

--
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