Fix 100% CPU from ContentView publisher feedback loop (fixes #3020)

Sources/ContentView.swift

@@ -1878,6 +1878,40 @@ private func installFileDropOverlayWhenReady(
     }
 }
 
+@MainActor
+private final class SelectedWorkspaceDirectoryObserver: ObservableObject {
+    @Published private(set) var directoryChangeGeneration: UInt64 = 0
+    private weak var tabManager: TabManager?
+    private var cancellable: AnyCancellable?
+
+    func wire(tabManager: TabManager) {
+        guard self.tabManager !== tabManager || cancellable == nil else { return }
+        self.tabManager = tabManager
+        cancellable = tabManager.$selectedTabId
+            .map { [weak tabManager] tabId -> Workspace? in
+                guard let tabId, let tabManager else { return nil }
+                return tabManager.tabs.first(where: { $0.id == tabId })
+            }
+            .removeDuplicates(by: { $0?.id == $1?.id })
+            .map { workspace -> AnyPublisher<(UUID?, String?), Never> in
+                guard let workspace else {
+                    return Just<(UUID?, String?)>((nil, nil)).eraseToAnyPublisher()
+                }
+                return workspace.$currentDirectory
+                    .map { (Optional(workspace.id), Optional($0)) }
+                    .eraseToAnyPublisher()
+            }
+            .switchToLatest()
+            .removeDuplicates { previous, next in
+                previous.0 == next.0 && previous.1 == next.1
+            }
+            .receive(on: DispatchQueue.main)
+            .sink { [weak self] _ in
+                self?.directoryChangeGeneration &+= 1
+            }
+    }
+}
+
 struct ContentView: View {
     @ObservedObject var updateViewModel: UpdateViewModel
     let windowId: UUID
@@ -1900,6 +1934,7 @@ struct ContentView: View {
     @StateObject private var fullscreenControlsViewModel = TitlebarControlsViewModel()
     @StateObject private var fileExplorerStore = FileExplorerStore()
     @StateObject private var sessionIndexStore = SessionIndexStore()
+    @StateObject private var selectedWorkspaceDirectoryObserver = SelectedWorkspaceDirectoryObserver()
     @State private var fileExplorerWidth: CGFloat = 220
     @State private var fileExplorerDragStartWidth: CGFloat?
     @State private var previousSelectedWorkspaceId: UUID?
@@ -3074,21 +3109,21 @@ struct ContentView: View {
               let tab = tabManager.tabs.first(where: { $0.id == selectedId }) else {
             // No selection means we have no local cwd to scope by; clear so the
             // sessions panel doesn't keep filtering by a stale previous tab.
-            sessionIndexStore.currentDirectory = nil
+            sessionIndexStore.setCurrentDirectoryIfChanged(nil)
             return
         }
 
         let dir = tab.currentDirectory.trimmingCharacters(in: .whitespacesAndNewlines)
         guard !dir.isEmpty else {
-            sessionIndexStore.currentDirectory = nil
+            sessionIndexStore.setCurrentDirectoryIfChanged(nil)
             return
         }
 
         fileExplorerStore.showHiddenFiles = true
         if !tab.isRemoteWorkspace {
-            sessionIndexStore.currentDirectory = dir
+            sessionIndexStore.setCurrentDirectoryIfChanged(dir)
         } else {
-            sessionIndexStore.currentDirectory = nil
+            sessionIndexStore.setCurrentDirectoryIfChanged(nil)
         }
 
         if tab.isRemoteWorkspace {
@@ -3215,6 +3250,7 @@ struct ContentView: View {
         )
 
         view = AnyView(view.onAppear {
+            selectedWorkspaceDirectoryObserver.wire(tabManager: tabManager)
             tabManager.applyWindowBackgroundForSelectedTab()
             reconcileMountedWorkspaceIds()
             previousSelectedWorkspaceId = tabManager.selectedTabId
@@ -3309,21 +3345,8 @@ struct ContentView: View {
             syncSidebarSelectedWorkspaceIds()
         })
 
-        // File explorer: reactively sync CWD when selected workspace or its directory changes.
-        // Uses switchToLatest to automatically unsubscribe from the old workspace's publisher.
-        view = AnyView(view.onReceive(
-            tabManager.$selectedTabId
-                .compactMap { [weak tabManager] tabId -> Workspace? in
-                    guard let tabId, let tabManager else { return nil }
-                    return tabManager.tabs.first(where: { $0.id == tabId })
-                }
-                .map { workspace -> AnyPublisher<String, Never> in
-                    workspace.$currentDirectory.eraseToAnyPublisher()
-                }
-                .switchToLatest()
-                .removeDuplicates()
-                .receive(on: DispatchQueue.main)
-        ) { _ in
+        // File explorer: keep the Combine subscription stable across body re-evaluations.
+        view = AnyView(view.onChange(of: selectedWorkspaceDirectoryObserver.directoryChangeGeneration) { _ in
             syncFileExplorerDirectory()
         })
 

Sources/RightSidebarPanelView.swift

@@ -47,9 +47,7 @@ struct RightSidebarPanelView: View {
                     if fileExplorerState.mode != mode {
                         fileExplorerState.mode = mode
                         if mode == .sessions {
-                            sessionIndexStore.currentDirectory = fileExplorerStore.rootPath.isEmpty
-                                ? nil
-                                : fileExplorerStore.rootPath
+                            sessionIndexStore.setCurrentDirectoryIfChanged(sessionIndexDirectory)
                             if sessionIndexStore.entries.isEmpty {
                                 sessionIndexStore.reload()
                             }
@@ -73,12 +71,14 @@ struct RightSidebarPanelView: View {
         case .sessions:
             SessionIndexView(store: sessionIndexStore, onResume: onResumeSession)
                 .onAppear {
-                    sessionIndexStore.currentDirectory = fileExplorerStore.rootPath.isEmpty
-                        ? nil
-                        : fileExplorerStore.rootPath
+                    sessionIndexStore.setCurrentDirectoryIfChanged(sessionIndexDirectory)
                 }
         }
     }
+
+    private var sessionIndexDirectory: String? {
+        fileExplorerStore.rootPath.isEmpty ? nil : fileExplorerStore.rootPath
+    }
 }
 
 private struct ModeBarButton: View {

Sources/SessionIndexStore.swift

@@ -291,6 +291,11 @@ final class SessionIndexStore: ObservableObject {
         }
     }
 
+    func setCurrentDirectoryIfChanged(_ next: String?) {
+        guard currentDirectory != next else { return }
+        currentDirectory = next
+    }
+
     @Published var grouping: SessionGrouping {
         didSet {
             guard grouping != oldValue else { return }

cmuxTests/SessionIndexViewTests.swift

@@ -1,4 +1,5 @@
 import AppKit
+import Combine
 import SwiftUI
 import XCTest
 
@@ -10,6 +11,20 @@ import XCTest
 
 @MainActor
 final class SessionIndexViewTests: XCTestCase {
+    func testCurrentDirectorySetterDoesNotPublishEqualValue() {
+        let store = SessionIndexStore()
+        var emittedValues: [String?] = []
+        let cancellable = store.$currentDirectory
+            .dropFirst()
+            .sink { emittedValues.append($0) }
+        defer { cancellable.cancel() }
+
+        store.setCurrentDirectoryIfChanged("/foo")
+        store.setCurrentDirectoryIfChanged("/foo")
+
+        XCTAssertEqual(emittedValues, ["/foo"])
+    }
+
     func testSectionPopoverHostCoordinatorSkipsHiddenRefreshes() {
         let harness = makeHarness()
         let coordinator = harness.host.makeCoordinator()
@@ -87,7 +102,8 @@ final class SessionIndexViewTests: XCTestCase {
         let section = IndexSection(
             key: .directory("/tmp"),
             title: "tmp",
-            icon: .folder
+            icon: .folder,
+            entries: []
         )
         let search: SessionSearchFn = { _, _, _, _ in
             SessionIndexStore.SearchOutcome(entries: [], errors: [])