diff --git a/GitUp/Application/AppDelegate.m b/GitUp/Application/AppDelegate.m
index fa98bf0f..a6138f7b 100644
--- a/GitUp/Application/AppDelegate.m
+++ b/GitUp/Application/AppDelegate.m
@@ -47,6 +47,7 @@ @interface AppDelegate () <UNUserNotificationCenterDelegate, SPUUpdaterDelegate,
 @property(nonatomic, strong) CloneWindowController* cloneWindowController;
 @property(nonatomic, strong) PreferencesWindowController* preferencesWindowController;
 @property(nonatomic, strong) WelcomeWindowController* welcomeWindowController;
+@property(nonatomic, weak) IBOutlet NSMenuItem* openInNewTabMenuItem;
 @end
 
 @implementation AppDelegate {
@@ -175,6 +176,12 @@ - (void)_openDocumentAtURL:(NSURL*)url {
 
 - (void)handleDocumentCountChanged {
   [self.welcomeWindowController handleDocumentCountChanged];
+
+  // Only offer "Open in New Tab…" as the Option alternate of "Open…" when there is a repository window to add a tab to
+  // (AppKit still swaps in hidden alternates, so the item must also stop being one)
+  BOOL hasDocuments = ([[NSDocumentController sharedDocumentController] documents].count > 0);
+  _openInNewTabMenuItem.hidden = !hasDocuments;
+  _openInNewTabMenuItem.alternate = hasDocuments;
 }
 
 - (void)_showNotificationWithTitle:(NSString*)title action:(SEL)action message:(NSString*)format, ... NS_FORMAT_FUNCTION(3, 4) {
@@ -381,6 +388,16 @@ - (IBAction)openDocument:(id)sender {
   [[NSDocumentController sharedDocumentController] openDocument:sender];
 }
 
+- (IBAction)openDocumentInNewTab:(id)sender {
+  NSDocumentController* controller = [NSDocumentController sharedDocumentController];
+  [controller beginOpenPanelWithCompletionHandler:^(NSArray<NSURL*>* urls) {
+    BOOL inTab = (controller.documents.count > 0);  // Fall back to a new window if the last repository window was closed in the meantime
+    for (NSURL* url in urls) {
+      [self _openRepositoryWithURL:url inTab:inTab withCloneMode:kCloneMode_None windowModeID:NSNotFound];
+    }
+  }];
+}
+
 - (IBAction)viewWiki:(id)sender {
   [[NSWorkspace sharedWorkspace] openURL:[NSURL URLWithString:kURL_Wiki]];
 }
diff --git a/GitUp/Application/Base.lproj/MainMenu.xib b/GitUp/Application/Base.lproj/MainMenu.xib
index 3630edc0..b041c6c7 100644
--- a/GitUp/Application/Base.lproj/MainMenu.xib
+++ b/GitUp/Application/Base.lproj/MainMenu.xib
@@ -12,7 +12,11 @@
         </customObject>
         <customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/>
         <customObject id="-3" userLabel="Application" customClass="NSObject"/>
-        <customObject id="Voe-Tx-rLC" customClass="AppDelegate"/>
+        <customObject id="Voe-Tx-rLC" customClass="AppDelegate">
+            <connections>
+                <outlet property="openInNewTabMenuItem" destination="T4b-oP-nNw" id="T4b-oP-oLt"/>
+            </connections>
+        </customObject>
         <menu title="Main Menu" systemMenu="main" id="AYu-sK-qS6">
             <items>
                 <menuItem title="GitUp" id="1Xt-HY-uBw">
@@ -102,6 +106,12 @@
                                     <action selector="openDocument:" target="-1" id="FlH-np-HFe"/>
                                 </connections>
                             </menuItem>
+                            <menuItem title="Open in New Tab…" alternate="YES" keyEquivalent="o" id="T4b-oP-nNw">
+                                <modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/>
+                                <connections>
+                                    <action selector="openDocumentInNewTab:" target="-1" id="T4b-oP-aCt"/>
+                                </connections>
+                            </menuItem>
                             <menuItem title="Open Recent" id="H69-uH-spF">
                                 <modifierMask key="keyEquivalentModifierMask"/>
                                 <menu key="submenu" title="Open Recent" systemMenu="recentDocuments" id="YgH-RV-NQr">
diff --git a/GitUpKit/Utilities/GIWindowController.m b/GitUpKit/Utilities/GIWindowController.m
index 6481b981..68938433 100644
--- a/GitUpKit/Utilities/GIWindowController.m
+++ b/GitUpKit/Utilities/GIWindowController.m
@@ -179,6 +179,8 @@ - (instancetype)initWithWindow:(NSWindow*)window {
   if ((self = [super initWithWindow:window])) {
     [[NSBundle bundleForClass:[GIWindowController class]] loadNibNamed:@"GIWindowController" owner:self topLevelObjects:NULL];
     XLOG_DEBUG_CHECK(_overlayView);
+    _overlayView.translatesAutoresizingMaskIntoConstraints = NO;
+    [_overlayView.heightAnchor constraintEqualToConstant:_overlayView.frame.size.height].active = YES;
 
     _area = [[NSTrackingArea alloc] initWithRect:NSZeroRect options:(NSTrackingInVisibleRect | NSTrackingActiveAlways | NSTrackingMouseEnteredAndExited) owner:self userInfo:nil];
     [_overlayView addTrackingArea:_area];
@@ -230,11 +232,15 @@ - (void)showOverlayWithStyle:(GIOverlayStyle)style message:(NSString*)message {
   }
 
   if (_overlayView.superview == nil) {
-    NSRect bounds = self.window.contentLayoutRect;
-    NSRect frame = _overlayView.frame;
-    _overlayView.frame = NSMakeRect(0, bounds.size.height - frame.size.height, bounds.size.width, frame.size.height);
+    NSView* contentView = self.window.contentView;
     _overlayView.alphaValue = 0;
-    [self.window.contentView addSubview:_overlayView];  // Must be above everything else
+    [contentView addSubview:_overlayView];  // Must be above everything else
+    [NSLayoutConstraint activateConstraints:@[
+      [_overlayView.topAnchor constraintEqualToAnchor:contentView.safeAreaLayoutGuide.topAnchor],  // Follows the titlebar as the tab bar appears or disappears
+      [_overlayView.leadingAnchor constraintEqualToAnchor:contentView.leadingAnchor],
+      [_overlayView.trailingAnchor constraintEqualToAnchor:contentView.trailingAnchor]
+    ]];
+    [contentView layoutSubtreeIfNeeded];
     [CATransaction flush];
 
     _overlayTextField.stringValue = message;