diff --git a/Application/Presentation/Entry/Sources/Main/MainView.swift b/Application/Presentation/Entry/Sources/Main/MainView.swift
index 8fda5635..721dab02 100644
--- a/Application/Presentation/Entry/Sources/Main/MainView.swift
+++ b/Application/Presentation/Entry/Sources/Main/MainView.swift
@@ -13,6 +13,8 @@ import PresentationShared
 import TodayTab
 
 struct MainView: View {
+    @Environment(\.horizontalSizeClass) private var horizontalSizeClass
+    @Environment(\.isiOSAppOnMac) private var isiOSAppOnMac
     @Binding var selectedTab: MainTab
     @State private var store: StoreOf<MainFeature>
     private let windowEvent: TodoEditorWindowEvent
@@ -29,30 +31,51 @@ struct MainView: View {
     }
 
     var body: some View {
-        TabView(selection: $selectedTab) {
-            Tab(value: MainTab.home) {
-                tabContent(.home)
-            } label: {
-                tabLabel(.home)
+        HStack(spacing: 0) {
+            if showsSideBar {
+                SideBar(
+                    selectedTab: $selectedTab,
+                    unreadPushCount: store.unreadPushCount
+                )
+                .resizableSideBar(
+                    minimumWidth: 220,
+                    idealWidth: 260,
+                    maximumWidth: 320
+                )
             }
-            Tab(value: MainTab.today) {
-                tabContent(.today)
-            } label: {
-                tabLabel(.today)
-            }
-            Tab(value: MainTab.notification) {
-                tabContent(.notification)
-            } label: {
-                tabLabel(.notification)
-            }
-            .badge(store.unreadPushCount)
-            Tab(value: MainTab.profile) {
-                tabContent(.profile)
-            } label: {
-                tabLabel(.profile)
+
+            TabView(selection: $selectedTab) {
+                Tab(
+                    MainTab.home.title,
+                    systemImage: MainTab.home.symbolName,
+                    value: MainTab.home
+                ) {
+                    tabContent(.home)
+                }
+                Tab(
+                    MainTab.today.title,
+                    systemImage: MainTab.today.symbolName,
+                    value: MainTab.today
+                ) {
+                    tabContent(.today)
+                }
+                Tab(
+                    MainTab.notification.title,
+                    systemImage: MainTab.notification.symbolName,
+                    value: MainTab.notification
+                ) {
+                    tabContent(.notification)
+                }
+                .badge(store.unreadPushCount)
+                Tab(
+                    MainTab.profile.title,
+                    systemImage: MainTab.profile.symbolName,
+                    value: MainTab.profile
+                ) {
+                    tabContent(.profile)
+                }
             }
         }
-        .tabViewStyle(.sidebarAdaptable)
         .toastHost()
         .onAppear { store.send(.view(.onAppear)) }
         .onChange(of: selectedTab, initial: true) { _, tab in
@@ -61,15 +84,16 @@ struct MainView: View {
         .prominentAlert(store, state: \.alert, action: \.alert)
     }
 
+    private var showsSideBar: Bool {
+        isiOSAppOnMac || horizontalSizeClass == .regular
+    }
+
     @ViewBuilder
     private func tabContent(_ tab: MainTab) -> some View {
         let isSelected = selectedTab == tab
         tabView(tab, isSelected: isSelected)
             .environment(\.isTabContentActive, isSelected)
-    }
-
-    private func tabLabel(_ tab: MainTab) -> some View {
-        Label(tab.title, systemImage: tab.symbolName)
+            .toolbarVisibility(showsSideBar ? .hidden : .visible, for: .tabBar)
     }
 
     @ViewBuilder
@@ -95,3 +119,135 @@ struct MainView: View {
         }
     }
 }
+
+private struct SideBar: View {
+    @Binding var selectedTab: MainTab
+    let unreadPushCount: Int
+
+    var body: some View {
+        GeometryReader { geometry in
+            VStack(alignment: .leading, spacing: 8) {
+                ForEach(MainTab.allCases, id: \.self) { tab in
+                    if tab == .profile { Spacer() }
+                    tabButton(tab)
+                }
+            }
+            .padding(.horizontal, 12)
+            .padding(.vertical, 16)
+            .padding(.top, windowControlTopPadding(in: geometry))
+        }
+        .background {
+            Color.surface
+                .ignoresSafeArea(.container, edges: .vertical)
+        }
+    }
+
+    private func windowControlTopPadding(in geometry: GeometryProxy) -> CGFloat {
+        guard #available(iOS 26.0, *),
+              UIDevice.current.userInterfaceIdiom == .pad else { return 0 }
+        return geometry.containerCornerInsets.topLeading.height
+    }
+
+    private func tabButton(_ tab: MainTab) -> some View {
+        let isSelected = selectedTab == tab
+
+        return Button {
+            selectedTab = tab
+        } label: {
+            HStack(spacing: 12) {
+                Image(systemName: tab.symbolName)
+                    .font(.title3)
+                    .frame(width: 24)
+                Text(tab.title)
+                    .font(.body.weight(.semibold))
+                    .lineLimit(1)
+                Spacer(minLength: 8)
+                if tab == .notification, 0 < unreadPushCount {
+                    Text(verbatim: unreadPushCount.formatted())
+                        .font(.caption.bold())
+                        .monospacedDigit()
+                        .foregroundStyle(Color.white)
+                        .padding(.horizontal, 8)
+                        .padding(.vertical, 4)
+                        .background(Color.accent, in: .capsule)
+                }
+            }
+            .foregroundStyle(isSelected ? Color.onPrimaryContainer : .primary)
+            .frame(maxWidth: .infinity, alignment: .leading)
+            .padding(.horizontal, 12)
+            .padding(.vertical, 10)
+            .background {
+                RoundedRectangle(cornerRadius: 12)
+                    .fill(isSelected ? Color.primaryContainer : .clear)
+            }
+            .contentShape(.rect)
+        }
+        .buttonStyle(.plain)
+    }
+}
+
+private struct ResizableSideBarModifier: ViewModifier {
+    @Environment(\.layoutDirection) private var layoutDirection
+    @State private var width: CGFloat
+    @State private var dragStartWidth: CGFloat?
+    private let minimumWidth: CGFloat
+    private let maximumWidth: CGFloat
+
+    init(
+        minimumWidth: CGFloat,
+        idealWidth: CGFloat,
+        maximumWidth: CGFloat
+    ) {
+        self.minimumWidth = minimumWidth
+        self.maximumWidth = maximumWidth
+        self._width = State(initialValue: min(max(idealWidth, minimumWidth), maximumWidth))
+    }
+
+    func body(content: Content) -> some View {
+        content
+            .frame(width: width)
+            .overlay(alignment: .trailing) {
+                Color.clear
+                    .frame(width: 16)
+                    .contentShape(.rect)
+                    .gesture(resizeGesture)
+                    .overlay(alignment: .trailing) {
+                        Rectangle()
+                            .fill(Color.border)
+                            .frame(width: 1)
+                    }
+                    .ignoresSafeArea(.container, edges: .vertical)
+            }
+    }
+
+    private var resizeGesture: some Gesture {
+        DragGesture(minimumDistance: 0, coordinateSpace: .global)
+            .onChanged { value in
+                if dragStartWidth == nil {
+                    dragStartWidth = width
+                }
+                let startWidth = dragStartWidth ?? width
+                let translation = layoutDirection == .leftToRight
+                    ? value.translation.width
+                    : -value.translation.width
+                width = min(max(startWidth + translation, minimumWidth), maximumWidth)
+            }
+            .onEnded { _ in
+                dragStartWidth = nil
+            }
+    }
+}
+
+private extension View {
+    func resizableSideBar(
+        minimumWidth: CGFloat,
+        idealWidth: CGFloat,
+        maximumWidth: CGFloat
+    ) -> some View {
+        modifier(ResizableSideBarModifier(
+            minimumWidth: minimumWidth,
+            idealWidth: idealWidth,
+            maximumWidth: maximumWidth
+        ))
+    }
+}