Fix autocomplete dropdown transparency using NSWindow

- Replace SwiftUI overlay with custom NSWindow implementation
- Use NSColor.controlBackgroundColor for opaque background
- Add proper click-outside-to-dismiss functionality
- Handle Swift concurrency and actor isolation correctly
- Inspired by SuggestionsDemo but simplified for our use case

mac/VibeTunnel/Presentation/Components/AutocompleteView.swift

@@ -70,8 +70,15 @@ struct AutocompleteViewWithKeyboard: View {
                 }
             }
         }
-        .background(.regularMaterial)
-        .cornerRadius(6)
+        .background(
+            ZStack {
+                // Base opaque layer
+                Color(NSColor.windowBackgroundColor)
+                // Material overlay for visual consistency
+                Color.primary.opacity(0.02)
+            }
+        )
+        .clipShape(RoundedRectangle(cornerRadius: 6))
         .overlay(
             RoundedRectangle(cornerRadius: 6)
                 .stroke(Color.primary.opacity(0.1), lineWidth: 1)
@@ -201,49 +208,64 @@ struct AutocompleteTextField: View {
     @State private var justSelectedCompletion = false
     @State private var keyboardNavigating = false
 
+    @State private var textFieldSize: CGSize = .zero
+    
     var body: some View {
-        VStack(spacing: 4) {
-            TextField(placeholder, text: $text)
-                .textFieldStyle(.roundedBorder)
-                .focused($isFocused)
-                .onKeyPress { keyPress in
-                    handleKeyPress(keyPress)
-                }
-                .onChange(of: text) { _, newValue in
-                    handleTextChange(newValue)
-                }
-                .onChange(of: isFocused) { _, focused in
-                    if !focused {
-                        // Hide suggestions after a delay to allow clicking
-                        DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) {
-                            showSuggestions = false
-                            selectedIndex = -1
-                        }
-                    } else if focused && !text.isEmpty && !(autocompleteService?.suggestions.isEmpty ?? true) {
-                        // Show suggestions when field gains focus if we have any
-                        showSuggestions = true
+        TextField(placeholder, text: $text)
+            .textFieldStyle(.roundedBorder)
+            .focused($isFocused)
+            .onKeyPress { keyPress in
+                handleKeyPress(keyPress)
+            }
+            .onChange(of: text) { _, newValue in
+                handleTextChange(newValue)
+            }
+            .onChange(of: isFocused) { _, focused in
+                if !focused {
+                    // Hide suggestions after a delay to allow clicking
+                    DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) {
+                        showSuggestions = false
+                        selectedIndex = -1
                     }
+                } else if focused && !text.isEmpty && !(autocompleteService?.suggestions.isEmpty ?? true) {
+                    // Show suggestions when field gains focus if we have any
+                    showSuggestions = true
                 }
-
-            if showSuggestions && isFocused && !(autocompleteService?.suggestions.isEmpty ?? true) {
-                AutocompleteViewWithKeyboard(
+            }
+            .background(
+                GeometryReader { geometry in
+                    Color.clear
+                        .onAppear {
+                            textFieldSize = geometry.size
+                        }
+                        .onChange(of: geometry.size) { _, newSize in
+                            textFieldSize = newSize
+                        }
+                }
+            )
+            .background(
+                AutocompleteWindowView(
                     suggestions: autocompleteService?.suggestions ?? [],
                     selectedIndex: $selectedIndex,
-                    keyboardNavigating: keyboardNavigating
-                ) { suggestion in
-                    justSelectedCompletion = true
-                    text = suggestion
-                    showSuggestions = false
-                    selectedIndex = -1
-                    autocompleteService?.clearSuggestions()
-                }
-                .transition(.asymmetric(
-                    insertion: .opacity.combined(with: .scale(scale: 0.95)).combined(with: .offset(y: -5)),
-                    removal: .opacity.combined(with: .scale(scale: 0.95))
-                ))
-            }
-        }
-        .animation(.easeInOut(duration: 0.15), value: showSuggestions)
+                    keyboardNavigating: keyboardNavigating,
+                    onSelect: { suggestion in
+                        justSelectedCompletion = true
+                        text = suggestion
+                        showSuggestions = false
+                        selectedIndex = -1
+                        autocompleteService?.clearSuggestions()
+                        // Keep focus on the text field
+                        DispatchQueue.main.async {
+                            isFocused = true
+                        }
+                    },
+                    width: textFieldSize.width,
+                    isShowing: Binding(
+                        get: { showSuggestions && isFocused && !(autocompleteService?.suggestions.isEmpty ?? true) },
+                        set: { showSuggestions = $0 }
+                    )
+                )
+            )
         .onAppear {
             // Initialize autocompleteService with GitRepositoryMonitor
             autocompleteService = AutocompleteService(gitMonitor: gitMonitor)
@@ -355,3 +377,49 @@ struct AutocompleteTextField: View {
         }
     }
 }
+
+/// Popup content wrapper for autocomplete suggestions
+private struct AutocompletePopupContent: View {
+    let suggestions: [PathSuggestion]
+    @Binding var selectedIndex: Int
+    let keyboardNavigating: Bool
+    let width: CGFloat
+    let onSelect: (String) -> Void
+    
+    var body: some View {
+        AutocompleteViewWithKeyboard(
+            suggestions: suggestions,
+            selectedIndex: $selectedIndex,
+            keyboardNavigating: keyboardNavigating,
+            onSelect: onSelect
+        )
+        .frame(width: width)
+        .frame(maxHeight: 200)
+        .background(
+            VisualEffectBackground()
+        )
+        .overlay(
+            RoundedRectangle(cornerRadius: 6)
+                .stroke(Color.primary.opacity(0.1), lineWidth: 1)
+        )
+        .shadow(color: .black.opacity(0.1), radius: 4, x: 0, y: 2)
+    }
+}
+
+/// Visual effect background for the autocomplete dropdown
+private struct VisualEffectBackground: NSViewRepresentable {
+    func makeNSView(context: Context) -> NSVisualEffectView {
+        let effectView = NSVisualEffectView()
+        effectView.material = .popover
+        effectView.blendingMode = .behindWindow
+        effectView.state = .active
+        effectView.wantsLayer = true
+        effectView.layer?.cornerRadius = 6
+        effectView.layer?.masksToBounds = true
+        return effectView
+    }
+    
+    func updateNSView(_ nsView: NSVisualEffectView, context: Context) {
+        // No updates needed
+    }
+}

mac/VibeTunnel/Presentation/Components/AutocompleteWindow.swift

@@ -0,0 +1,172 @@
+import SwiftUI
+import AppKit
+
+/// Simple NSWindow-based dropdown for autocomplete
+struct AutocompleteWindowView: NSViewRepresentable {
+    let suggestions: [PathSuggestion]
+    @Binding var selectedIndex: Int
+    let keyboardNavigating: Bool
+    let onSelect: (String) -> Void
+    let width: CGFloat
+    @Binding var isShowing: Bool
+    
+    func makeNSView(context: Context) -> NSView {
+        let view = NSView()
+        view.wantsLayer = true
+        return view
+    }
+    
+    func updateNSView(_ nsView: NSView, context: Context) {
+        if isShowing && !suggestions.isEmpty {
+            context.coordinator.showDropdown(
+                on: nsView,
+                suggestions: suggestions,
+                selectedIndex: selectedIndex,
+                keyboardNavigating: keyboardNavigating,
+                width: width
+            )
+        } else {
+            context.coordinator.hideDropdown()
+        }
+    }
+    
+    func makeCoordinator() -> Coordinator {
+        Coordinator(onSelect: onSelect, isShowing: $isShowing)
+    }
+    
+    @MainActor
+    class Coordinator: NSObject {
+        private var dropdownWindow: NSWindow?
+        private var hostingView: NSHostingView<AnyView>?
+        private let onSelect: (String) -> Void
+        @Binding var isShowing: Bool
+        nonisolated(unsafe) private var clickMonitor: Any?
+        
+        init(onSelect: @escaping (String) -> Void, isShowing: Binding<Bool>) {
+            self.onSelect = onSelect
+            self._isShowing = isShowing
+            super.init()
+        }
+        
+        deinit {
+            if let monitor = clickMonitor {
+                DispatchQueue.main.async {
+                    NSEvent.removeMonitor(monitor)
+                }
+            }
+        }
+        
+        @MainActor
+        private func cleanupClickMonitor() {
+            if let monitor = clickMonitor {
+                NSEvent.removeMonitor(monitor)
+                clickMonitor = nil
+            }
+        }
+        
+        @MainActor
+        func showDropdown(
+            on view: NSView,
+            suggestions: [PathSuggestion],
+            selectedIndex: Int,
+            keyboardNavigating: Bool,
+            width: CGFloat
+        ) {
+            guard let parentWindow = view.window else { return }
+            
+            // Create window if needed
+            if dropdownWindow == nil {
+                let window = NSWindow(
+                    contentRect: NSRect(x: 0, y: 0, width: width, height: 200),
+                    styleMask: [.borderless],
+                    backing: .buffered,
+                    defer: false
+                )
+                
+                window.isOpaque = false
+                window.backgroundColor = .clear
+                window.hasShadow = true
+                window.level = .floating
+                window.isReleasedWhenClosed = false
+                
+                let hostingView = NSHostingView(rootView: AnyView(EmptyView()))
+                window.contentView = hostingView
+                
+                self.dropdownWindow = window
+                self.hostingView = hostingView
+            }
+            
+            guard let window = dropdownWindow,
+                  let hostingView = hostingView else { return }
+            
+            // Update content
+            let content = VStack(spacing: 0) {
+                AutocompleteViewWithKeyboard(
+                    suggestions: suggestions,
+                    selectedIndex: .constant(selectedIndex),
+                    keyboardNavigating: keyboardNavigating
+                ) { [weak self] suggestion in
+                    self?.onSelect(suggestion)
+                    self?.isShowing = false
+                }
+            }
+            .frame(width: width)
+            .frame(maxHeight: 200)
+            .background(
+                RoundedRectangle(cornerRadius: 6)
+                    .fill(Color(NSColor.controlBackgroundColor))
+                    .shadow(color: .black.opacity(0.1), radius: 4, x: 0, y: 2)
+            )
+            .overlay(
+                RoundedRectangle(cornerRadius: 6)
+                    .stroke(Color.primary.opacity(0.1), lineWidth: 1)
+            )
+            
+            hostingView.rootView = AnyView(content)
+            
+            // Position window below the text field
+            let viewFrame = view.convert(view.bounds, to: nil)
+            let screenFrame = parentWindow.convertToScreen(viewFrame)
+            
+            // Calculate window position
+            let windowFrame = NSRect(
+                x: screenFrame.minX,
+                y: screenFrame.minY - 204, // dropdown height + spacing
+                width: width,
+                height: 200
+            )
+            
+            window.setFrame(windowFrame, display: false)
+            
+            // Show window
+            if window.parent == nil {
+                parentWindow.addChildWindow(window, ordered: .above)
+            }
+            window.makeKeyAndOrderFront(nil)
+            
+            // Setup click monitoring
+            if clickMonitor == nil {
+                clickMonitor = NSEvent.addLocalMonitorForEvents(
+                    matching: [.leftMouseDown, .rightMouseDown]
+                ) { [weak self] event in
+                    if event.window != window {
+                        self?.isShowing = false
+                    }
+                    return event
+                }
+            }
+        }
+        
+        @MainActor
+        func hideDropdown() {
+            cleanupClickMonitor()
+            
+            if let window = dropdownWindow {
+                if let parent = window.parent {
+                    parent.removeChildWindow(window)
+                }
+                window.orderOut(nil)
+            }
+        }
+    }
+}

mac/VibeTunnel/Presentation/Components/NewSessionForm.swift

@@ -163,24 +163,23 @@ struct NewSessionForm: View {
                             .font(.system(size: 11, weight: .medium))
                             .foregroundColor(.secondary)
 
-                        VStack(alignment: .leading, spacing: 0) {
-                            HStack(spacing: 8) {
-                                AutocompleteTextField(text: $workingDirectory, placeholder: "~/")
-                                    .focused($focusedField, equals: .directory)
-                                    .onChange(of: workingDirectory) { _, newValue in
-                                        checkForGitRepository(at: newValue)
-                                    }
-
-                                Button(action: selectDirectory) {
-                                    Image(systemName: "folder")
-                                        .font(.system(size: 12))
-                                        .foregroundColor(.secondary)
-                                        .frame(width: 20, height: 20)
-                                        .contentShape(Rectangle())
+                        HStack(spacing: 8) {
+                            AutocompleteTextField(text: $workingDirectory, placeholder: "~/")
+                                .focused($focusedField, equals: .directory)
+                                .onChange(of: workingDirectory) { _, newValue in
+                                    checkForGitRepository(at: newValue)
                                 }
-                                .buttonStyle(.borderless)
-                                .help("Choose directory")
+                                .zIndex(1) // Ensure autocomplete appears above other elements
+
+                            Button(action: selectDirectory) {
+                                Image(systemName: "folder")
+                                    .font(.system(size: 12))
+                                    .foregroundColor(.secondary)
+                                    .frame(width: 20, height: 20)
+                                    .contentShape(Rectangle())
                             }
+                            .buttonStyle(.borderless)
+                            .help("Choose directory")
                         }
                     }