Fix #711: Retain sidebar panel state when switching tabs

CodeEdit/Features/CodeEditUI/Views/WorkspacePanelView.swift

@@ -34,11 +34,23 @@ struct WorkspacePanelView<Tab: WorkspacePanelTab, ViewModel: ObservableObject>:
 
     var body: some View {
         VStack(spacing: 0) {
-            if let selection = selectedTab {
-                selection
-            } else {
-                CEContentUnavailableView("No Selection")
+            // Keep every sidebar panel mounted so expand/scroll state survives tab switches (#711).
+            // Hiding with opacity (instead of swapping `if selectedTab`) preserves NSOutlineView state.
+            ZStack {
+                ForEach(tabItems) { tab in
+                    let isSelected = selectedTab == tab
+                    tab
+                        .opacity(isSelected ? 1 : 0)
+                        .allowsHitTesting(isSelected)
+                        .accessibilityHidden(!isSelected)
+                        .zIndex(isSelected ? 1 : 0)
+                }
+
+                if selectedTab == nil {
+                    CEContentUnavailableView("No Selection")
+                }
             }
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
         }
         .safeAreaInset(edge: .leading, spacing: 0) {
             if sidebarPosition == .side {

CodeEditTests/Features/CodeEditUI/WorkspacePanelRetentionTests.swift

@@ -0,0 +1,85 @@
+//
+//  WorkspacePanelRetentionTests.swift
+//  CodeEditTests
+//
+//  Created by Boris Serzhanovich on 1/8/26.
+//
+
+import Testing
+import SwiftUI
+@testable import CodeEdit
+
+/// Verifies sidebar tab panels stay mounted so AppKit outline state can survive tab switches (#711).
+@Suite("Workspace panel retention")
+struct WorkspacePanelRetentionTests {
+
+    private struct ProbeTab: WorkspacePanelTab {
+        let id: String
+        let title: String
+        let systemImage: String
+        let marker: String
+
+        var body: some View {
+            Text(marker)
+                .accessibilityIdentifier("ProbeTab-\(id)")
+        }
+    }
+
+    @MainActor
+    private final class ProbeViewModel: ObservableObject {
+        @Published var selectedTab: ProbeTab?
+        @Published var tabItems: [ProbeTab]
+        init(tabs: [ProbeTab], selected: ProbeTab?) {
+            self.tabItems = tabs
+            self.selectedTab = selected
+        }
+    }
+
+    @Test
+    @MainActor
+    func keepsAllTabBodiesMountedWhenSelectionChanges() {
+        let project = ProbeTab(id: "project", title: "Project", systemImage: "folder", marker: "PROJECT")
+        let search = ProbeTab(id: "search", title: "Search", systemImage: "magnifyingglass", marker: "SEARCH")
+        let viewModel = ProbeViewModel(tabs: [project, search], selected: project)
+
+        let view = WorkspacePanelView(
+            viewModel: viewModel,
+            selectedTab: Binding(
+                get: { viewModel.selectedTab },
+                set: { viewModel.selectedTab = $0 }
+            ),
+            tabItems: Binding(
+                get: { viewModel.tabItems },
+                set: { viewModel.tabItems = $0 }
+            ),
+            sidebarPosition: .top
+        )
+
+        let hosting = NSHostingView(rootView: view.frame(width: 240, height: 320))
+        hosting.layoutSubtreeIfNeeded()
+
+        #expect(hostingContains(hosting, text: "PROJECT"))
+        #expect(hostingContains(hosting, text: "SEARCH"))
+
+        viewModel.selectedTab = search
+        hosting.layoutSubtreeIfNeeded()
+
+        // Both panels remain in the hierarchy after switching — state retention depends on this.
+        #expect(hostingContains(hosting, text: "PROJECT"))
+        #expect(hostingContains(hosting, text: "SEARCH"))
+    }
+
+    @MainActor
+    private func hostingContains(_ hosting: NSHostingView<some View>, text: String) -> Bool {
+        func search(_ view: NSView) -> Bool {
+            if let textField = view as? NSTextField, textField.stringValue.contains(text) {
+                return true
+            }
+            if let textView = view as? NSTextView, textView.string.contains(text) {
+                return true
+            }
+            return view.subviews.contains(where: search)
+        }
+        return search(hosting)
+    }
+}

CodeEditUITests/Features/NavigatorArea/SidebarPanelRetentionUITests.swift

@@ -0,0 +1,55 @@
+//
+//  SidebarPanelRetentionUITests.swift
+//  CodeEditUITests
+//
+//  Created by Boris Serzhanovich on 1/8/26.
+//
+
+import XCTest
+
+/// UI regression for #711 — navigator expand state must survive switching sidebar tabs.
+final class SidebarPanelRetentionUITests: XCTestCase {
+
+    var application: XCUIApplication!
+
+    override func setUp() {
+        application = App.launchWithCodeEditWorkspace()
+    }
+
+    func testProjectNavigatorKeepsExpansionAfterSidebarTabSwitch() {
+        let window = Query.getWindow(application)
+        XCTAssertTrue(window.exists, "Window not found")
+        window.toolbars.firstMatch.click()
+
+        let navigator = Query.Window.getProjectNavigator(window)
+        XCTAssertTrue(navigator.waitForExistence(timeout: 2.0), "Navigator not found")
+
+        let codeEditFolderRow = Query.Navigator.getProjectNavigatorRow(fileTitle: "CodeEdit", index: 1, navigator)
+        XCTAssertTrue(codeEditFolderRow.exists)
+        let folderDisclosureIndicator = Query.Navigator.disclosureIndicatorForRow(codeEditFolderRow)
+        XCTAssertTrue(folderDisclosureIndicator.exists)
+
+        let collapsedRowCount = navigator.descendants(matching: .outlineRow).count
+        folderDisclosureIndicator.click()
+        let expandedRowCount = navigator.descendants(matching: .outlineRow).count
+        XCTAssertTrue(expandedRowCount > collapsedRowCount, "Folder did not expand")
+
+        // Switch away to Search, then back to Project.
+        let searchTab = window.buttons["WorkspacePanelTab-Search"]
+        XCTAssertTrue(searchTab.waitForExistence(timeout: 2.0), "Search navigator tab not found")
+        searchTab.click()
+
+        let projectTab = window.buttons["WorkspacePanelTab-Project"]
+        XCTAssertTrue(projectTab.waitForExistence(timeout: 2.0), "Project navigator tab not found")
+        projectTab.click()
+
+        let navigatorAfter = Query.Window.getProjectNavigator(window)
+        XCTAssertTrue(navigatorAfter.waitForExistence(timeout: 2.0))
+        let restoredRowCount = navigatorAfter.descendants(matching: .outlineRow).count
+        XCTAssertEqual(
+            restoredRowCount,
+            expandedRowCount,
+            "Project navigator lost expansion state after switching sidebar tabs"
+        )
+    }
+}

Documentation.docc/App Window/InspectorSidebarView.md

@@ -1,5 +1,8 @@
 # ``CodeEdit/InspectorAreaView``
 
+Inspector tabs share ``WorkspacePanelView`` with the navigator: panels stay mounted and are
+shown/hidden with opacity so selection and scroll state survive tab switches (#711).
+
 ## Topics
 
 ### Toolbars

Documentation.docc/App Window/NavigatorSidebarView.md

@@ -1,5 +1,10 @@
 # ``CodeEdit/NavigatorSidebarView``
 
+Navigator and inspector sidebars use ``WorkspacePanelView``, which keeps every tab panel
+mounted and toggles visibility with opacity. That preserves AppKit outline expansion and
+scroll position when switching between Project, Source Control, Search, and inspector tabs
+(see issue #711).
+
 ## Topics
 
 ### Toolbars