diff --git a/README.md b/README.md
index af0a6a3ca..0fb827b34 100644
--- a/README.md
+++ b/README.md
@@ -35,7 +35,7 @@ Zen is a firefox-based browser with the aim of pushing your productivity to a ne
 ### Firefox Versions
 
 - [`Release`](https://zen-browser.app/download) - Is currently built using Firefox version `151.0.4`! 🚀
-- [`Twilight`](https://zen-browser.app/download?twilight) - Is currently built using Firefox version `RC 151.0.4`!
+- [`Twilight`](https://zen-browser.app/download?twilight) - Is currently built using Firefox version `RC 152.0`!
 
 ### Contributing
 
diff --git a/build/firefox-cache/l10n-last-commit-hash b/build/firefox-cache/l10n-last-commit-hash
index f138bc25d..3d6223d5d 100644
--- a/build/firefox-cache/l10n-last-commit-hash
+++ b/build/firefox-cache/l10n-last-commit-hash
@@ -1 +1 @@
-9a6aa4c359d1fb6ac60decc82402f82d49a17cea
\ No newline at end of file
+a58ad2d2952face15859068dd4421cf68d6a9dda
\ No newline at end of file
diff --git a/src/external-patches/firefox/native_macos_popovers/D284084.patch b/src/external-patches/firefox/native_macos_popovers/D284084.patch
index 59e6e31fb..791888e3c 100644
--- a/src/external-patches/firefox/native_macos_popovers/D284084.patch
+++ b/src/external-patches/firefox/native_macos_popovers/D284084.patch
@@ -7,7 +7,7 @@ diff --git a/browser/base/content/main-popupset.inc.xhtml b/browser/base/content
           id="selection-shortcut-action-panel"
           noautofocus="true"
           consumeoutsideclicks="never"
-+         nonnativepopover="true"
++         nonnative=""
           type="arrow">
      <hbox class="panel-subview-body">
        <html:moz-button id="ai-action-button"/>
@@ -19,7 +19,7 @@ diff --git a/browser/base/content/main-popupset.inc.xhtml b/browser/base/content
    <panel class="panel-no-padding"
           id="chat-shortcuts-options-panel"
           noautofocus="true"
-+         nonnativepopover="true"
++         nonnative=""
           type="arrow">
      <vbox class="panel-subview-body"/>
    </panel>
@@ -31,7 +31,7 @@ diff --git a/browser/base/content/main-popupset.inc.xhtml b/browser/base/content
           noautofocus="true"
           norolluponanchor="true"
           consumeoutsideclicks="false"
-+         nonnativepopover="true"
++         nonnative=""
           role="tooltip">
      <html:div class="tab-preview-content-interactive"></html:div>
      <html:div class="tab-preview-content-main">
@@ -46,7 +46,7 @@ diff --git a/browser/components/asrouter/modules/FeatureCallout.sys.mjs b/browse
              type="arrow"
              consumeoutsideclicks="never"
              norolluponanchor="true"
-+ 
++            nonnative=""
              position="${panel_position.panel_position_string}"
              ${hide_arrow ? "" : 'show-arrow=""'}
              ${autohide ? "" : 'noautohide="true"'}
@@ -61,7 +61,7 @@ diff --git a/browser/components/customizableui/content/panelUI.inc.xhtml b/brows
         hidden="true"
         flip="slide"
         position="bottomright topright"
-+       hidepopovertail="true"
++       hidepopovertail=""
         noautofocus="true">
    <panelmultiview id="appMenu-multiView" mainViewId="appMenu-mainView"
                    viewCacheId="appMenu-viewCache">
@@ -70,31 +70,33 @@ diff --git a/browser/components/customizableui/content/panelUI.inc.xhtml b/brows
 diff --git a/dom/xul/XULPopupElement.cpp b/dom/xul/XULPopupElement.cpp
 --- a/dom/xul/XULPopupElement.cpp
 +++ b/dom/xul/XULPopupElement.cpp
-@@ -80,10 +80,14 @@
+@@ -80,10 +80,15 @@
  }
  
  void XULPopupElement::OpenPopupAtScreen(int32_t aXPos, int32_t aYPos,
                                          bool aIsContextMenu,
                                          Event* aTriggerEvent) {
-+  // TODO(cheff): At nsCocoaWindow::Show but we check for ShouldShowAsNSPopover
-+  //   to determine whether to use a native popover or not. This should sort of
-+  //   "replicate" that logic here, but it's a bit of a hacky way.
-+  SetAttr(kNameSpaceID_None, nsGkAtoms::nonnativepopover, u"true"_ns, true);
++  if (NodeInfo()->NameAtom() == nsGkAtoms::panel) {
++    // TODO(bug 2038354): Remove this and make the front-end set the attribute
++    // explicitly.
++    SetAttr(kNameSpaceID_None, nsGkAtoms::nonnative, u"true"_ns, true);
++  }
    nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
    if (pm) {
      pm->ShowPopupAtScreen(this, aXPos, aYPos, aIsContextMenu, aTriggerEvent);
    }
  }
-@@ -93,10 +97,14 @@
+@@ -93,10 +98,15 @@
                                              int32_t aWidth, int32_t aHeight,
                                              bool aIsContextMenu,
                                              bool aAttributesOverride,
                                              Event* aTriggerEvent) {
    nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
-+  // TODO: See OpenPopupAtScreen. We should remove this and use the other
-+  // implementation because this is a bit of a hacky way to determine whether to
-+  // use a native popover or not.
-+  SetAttr(kNameSpaceID_None, nsGkAtoms::nonnativepopover, u"true"_ns, true);
++  if (NodeInfo()->NameAtom() == nsGkAtoms::panel) {
++    // TODO(bug 2038354): Remove this and make the front-end set the attribute
++    // explicitly.
++    SetAttr(kNameSpaceID_None, nsGkAtoms::nonnative, u"true"_ns, true);
++  }
    if (pm) {
      pm->ShowPopupAtScreenRect(
          this, aPosition, nsIntRect(aXPos, aYPos, aWidth, aHeight),
@@ -103,7 +105,7 @@ diff --git a/dom/xul/XULPopupElement.cpp b/dom/xul/XULPopupElement.cpp
 diff --git a/layout/xul/nsMenuPopupFrame.h b/layout/xul/nsMenuPopupFrame.h
 --- a/layout/xul/nsMenuPopupFrame.h
 +++ b/layout/xul/nsMenuPopupFrame.h
-@@ -528,18 +528,10 @@
+@@ -516,18 +516,10 @@
  
    // Move the popup to the position specified in its |left| and |top|
    // attributes.
@@ -122,7 +124,7 @@ diff --git a/layout/xul/nsMenuPopupFrame.h b/layout/xul/nsMenuPopupFrame.h
   public:
    /**
     * Return whether the popup direction should be RTL.
-@@ -548,10 +540,18 @@
+@@ -536,10 +528,18 @@
     *
     * Return whether the popup direction should be RTL.
     */
@@ -144,7 +146,7 @@ diff --git a/layout/xul/nsMenuPopupFrame.h b/layout/xul/nsMenuPopupFrame.h
 diff --git a/modules/libpref/init/StaticPrefList.yaml b/modules/libpref/init/StaticPrefList.yaml
 --- a/modules/libpref/init/StaticPrefList.yaml
 +++ b/modules/libpref/init/StaticPrefList.yaml
-@@ -19672,10 +19672,19 @@
+@@ -19840,10 +19840,19 @@
    value: true
    mirror: always
  
@@ -168,20 +170,20 @@ diff --git a/toolkit/themes/shared/global-shared.css b/toolkit/themes/shared/glo
 --- a/toolkit/themes/shared/global-shared.css
 +++ b/toolkit/themes/shared/global-shared.css
 @@ -72,10 +72,22 @@
-   --menuitem-border-radius: var(--panel-menuitem-border-radius);
-   --menuitem-padding: var(--panel-menuitem-padding);
-   --menuitem-margin: var(--panel-menuitem-margin);
+   --menuitem-border-radius: var(--arrowpanel-menuitem-border-radius);
+   --menuitem-padding: var(--arrowpanel-menuitem-padding);
+   --menuitem-margin: var(--arrowpanel-menuitem-margin);
  }
  
 +/* stylelint-disable-next-line media-query-no-invalid */
 +@media -moz-pref("widget.macos.native-popovers") and (-moz-platform: macos) {
-+  panel:not(:where([nonnativepopover="true"])) {
++  panel:not([nonnative]) {
 +    background-color: transparent;
 +    --panel-background: transparent;
-+    --panel-shadow: none;
++    --panel-box-shadow: none;
 +    --panel-border-color: transparent;
-+    --panel-shadow-margin: 0px;
-+ 
++    --panel-box-shadow-margin: 0px;
++    --panel-padding: 0px;
 +  }
 +}
 +
@@ -241,7 +243,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.h b/widget/cocoa/nsCocoaWindow.h
  
 +  // Check if this window should use NSPopover for popup/menu display
 +  bool ShouldUseNSPopover() const;
-+  bool ShouldShowAsNSPopover() const override;
++  bool ShouldShowAsNSPopover() const;
 +
    [[nodiscard]] nsresult Create(nsIWidget* aParent, const DesktopIntRect& aRect,
                                  const InitData&) override;
@@ -265,7 +267,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
  #include "nsIDOMWindowUtils.h"
  #include "nsILocalFileMac.h"
  #include "CocoaCompositorWidget.h"
-@@ -5031,10 +5034,15 @@
+@@ -5088,10 +5091,15 @@
    if (mWindowType == WindowType::Popup) {
      SetPopupWindowLevel();
      mWindow.backgroundColor = NSColor.clearColor;
@@ -281,7 +283,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
      // the active space. Does not work with multiple displays. See
      // NeedsRecreateToReshow() for multi-display with multi-space workaround.
      mWindow.collectionBehavior = mWindow.collectionBehavior |
-@@ -5236,10 +5244,57 @@
+@@ -5293,10 +5301,57 @@
    NS_OBJC_END_TRY_IGNORE_BLOCK;
  }
  
@@ -339,7 +341,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
    NS_OBJC_BEGIN_TRY_IGNORE_BLOCK;
  
    if (!mWindow) {
-@@ -5300,10 +5355,58 @@
+@@ -5357,10 +5412,53 @@
        mWindow.contentView.needsDisplay = YES;
        if (!nativeParentWindow || mPopupLevel != PopupLevel::Parent) {
          [mWindow orderFront:nil];
@@ -375,22 +377,17 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
 +        // specific parent view
 +        NSRect positioningRect = [parentView convertRect:windowRect
 +                                                fromView:nil];
-+        BOOL shouldHideAnchor = NO;
-+        auto& element = popupFrame->PopupElement();
-+        if (element.GetBoolAttr(nsGkAtoms::hidepopovertail)) {
-+          shouldHideAnchor = YES;
-+        }
++        bool shouldHideAnchor =
++            popupFrame->PopupElement().GetBoolAttr(nsGkAtoms::hidepopovertail);
 +        [(PopupWindow*)mWindow showPopoverRelativeToRect:positioningRect
 +                                                  ofView:parentView
 +                                           preferredEdge:preferredEdge
 +                                            hiddenAnchor:shouldHideAnchor];
++#pragma clang diagnostic push
++#pragma clang diagnostic ignored "-Wobjc-method-access"
 +        SyncPopoverBounds([(PopupWindow*)mWindow popover], popupFrame);
-+
-+
-+
-+
++#pragma clang diagnostic pop
 +        // Exit early here since the popover is now shown.
-+
 +        return;
 +      }
        // If our popup window is a non-native context menu, tell the OS (and
@@ -398,7 +395,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
        // close other programs' context menus when ours open.
        if ([mWindow isKindOfClass:[PopupWindow class]] &&
            [(PopupWindow*)mWindow isContextMenu]) {
-@@ -5373,11 +5476,15 @@
+@@ -5430,11 +5528,15 @@
      // unhook it here before ordering it out. When you order out the child
      // of a window it hides the parent window.
      if (mWindowType == WindowType::Popup && nativeParentWindow) {
@@ -415,7 +412,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
      // other programs) that a menu has closed.
      if ([mWindow isKindOfClass:[PopupWindow class]] &&
          [(PopupWindow*)mWindow isContextMenu]) {
-@@ -5424,10 +5531,28 @@
+@@ -5481,10 +5583,28 @@
      return false;
    }
    return nsIWidget::ShouldUseOffMainThreadCompositing();
@@ -424,8 +421,8 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
 +bool nsCocoaWindow::ShouldUseNSPopover() const {
 +  // Use NSPopover for panel popups when the preference is enabled
 +  // But not for detached popups - they should use traditional window logic
-+  return (mWindowType == WindowType::Popup && mPopupType == PopupType::Panel &&
-+          mozilla::StaticPrefs::widget_macos_native_popovers());
++  return mWindowType == WindowType::Popup && mPopupType == PopupType::Panel &&
++         mozilla::StaticPrefs::widget_macos_native_popovers();
 +}
 +
 +bool nsCocoaWindow::ShouldShowAsNSPopover() const {
@@ -444,7 +441,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
  
    return mWindow.isOpaque ? TransparencyMode::Opaque
                            : TransparencyMode::Transparent;
-@@ -6378,10 +6503,19 @@
+@@ -6442,10 +6562,22 @@
  
    // We ignore aRepaint -- we have to call display:YES, otherwise the
    // title bar doesn't immediately get repainted and is displayed in
@@ -454,17 +451,20 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
 +    [(PopupWindow*)mWindow updatePopoverContent];
 +    // A popover won't resize by setting the frame
 +    // as it's size is calculated based on the content size
-+    // Therefor the content size has to be changed as well
++    // Therefore the content size has to be changed as well
 +    NSSize contentSize = NSMakeSize(aWidth, aHeight);
++#pragma clang diagnostic push
++#pragma clang diagnostic ignored "-Wobjc-method-access"
 +    [[(PopupWindow*)mWindow popover] setContentSize:contentSize];
 +    SyncPopoverBounds([(PopupWindow*)mWindow popover], GetPopupFrame());
++#pragma clang diagnostic pop
 +  }
  
    NS_OBJC_END_TRY_IGNORE_BLOCK;
  }
  
  void nsCocoaWindow::Resize(const DesktopRect& aRect, bool aRepaint) {
-@@ -8393,18 +8527,31 @@
+@@ -8517,18 +8649,31 @@
                              backing:bufferingType
                                defer:deferCreation];
    if (!self) {
@@ -497,7 +497,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
  // Return 0 in order to match what the system does for sheet windows and
  // _NSPopoverWindows.
  - (CGFloat)_backdropBleedAmount {
-@@ -8460,10 +8607,122 @@
+@@ -8584,10 +8729,125 @@
  
  - (void)setIsContextMenu:(BOOL)flag {
    mIsContextMenu = flag;
@@ -537,7 +537,7 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
 +}
 +
 +- (BOOL)usePopover {
-+  return mUsePopover && !mIsContextMenu;
++  return mUsePopover;
 +}
 +
 +- (void)showPopoverRelativeToRect:(NSRect)positioningRect
@@ -562,7 +562,10 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
 +
 +    // This is a hidden API that prevents the popover from showing its arrow
 +    // pointing to the anchor.
++#pragma clang diagnostic push
++#pragma clang diagnostic ignored "-Wobjc-method-access"
 +    [mPopover setShouldHideAnchor:hiddenAnchor];
++#pragma clang diagnostic pop
 +
 +    [mPopover showRelativeToRect:positioningRect
 +                          ofView:positioningView
@@ -620,25 +623,6 @@ diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
    return NO;
  }
  
-diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
---- a/widget/nsIWidget.h
-+++ b/widget/nsIWidget.h
-@@ -829,10 +829,15 @@
-   virtual void SuppressAnimation(bool aSuppress) {}
- 
-   /** Sets windows-specific mica backdrop on this widget. */
-   virtual void SetMicaBackdrop(bool) {}
- 
-+  /**
-+   * Determine whether this widget should be shown as an NSPopover.
-+   */
-+  virtual bool ShouldShowAsNSPopover() const { return false; }
-+
-   /**
-    * Return size mode (minimized, maximized, normalized).
-    * Returns a value from nsSizeMode (see nsIWidgetListener.h)
-    */
-   virtual nsSizeMode SizeMode() = 0;
 diff --git a/xpcom/ds/StaticAtoms.py b/xpcom/ds/StaticAtoms.py
 --- a/xpcom/ds/StaticAtoms.py
 +++ b/xpcom/ds/StaticAtoms.py
@@ -654,16 +638,4 @@ diff --git a/xpcom/ds/StaticAtoms.py b/xpcom/ds/StaticAtoms.py
      Atom("highest", "highest"),
      Atom("horizontal", "horizontal"),
      Atom("hover", "hover"),
-@@ -759,10 +760,11 @@
-     Atom("nohref", "nohref"),
-     Atom("noinitialselection", "noinitialselection"),
-     Atom("nomodule", "nomodule"),
-     Atom("nonce", "nonce"),
-     Atom("none", "none"),
-+    Atom("nonnativepopover", "nonnativepopover"),
-     Atom("noresize", "noresize"),
-     Atom("normal", "normal"),
-     Atom("normalizeSpace", "normalize-space"),
-     Atom("noscript", "noscript"),
-     Atom("noshade", "noshade"),
 
diff --git a/src/external-patches/firefox/native_macos_popovers/D299584.patch b/src/external-patches/firefox/native_macos_popovers/D299584.patch
index a729c092c..11c4006be 100644
--- a/src/external-patches/firefox/native_macos_popovers/D299584.patch
+++ b/src/external-patches/firefox/native_macos_popovers/D299584.patch
@@ -1,3 +1,18 @@
+diff --git a/toolkit/themes/shared/global-shared.css b/toolkit/themes/shared/global-shared.css
+--- a/toolkit/themes/shared/global-shared.css
++++ b/toolkit/themes/shared/global-shared.css
+@@ -80,11 +80,10 @@
+     background-color: transparent;
+     --panel-background: transparent;
+     --panel-box-shadow: none;
+     --panel-border-color: transparent;
+     --panel-box-shadow-margin: 0px;
+-    --panel-padding: 0px;
+   }
+ }
+ 
+ /* Lightweight theme roots */
+ 
 diff --git a/widget/cocoa/nsCocoaWindow.h b/widget/cocoa/nsCocoaWindow.h
 --- a/widget/cocoa/nsCocoaWindow.h
 +++ b/widget/cocoa/nsCocoaWindow.h
diff --git a/src/zen/tests/mochitests/safebrowsing/browser_whitelisted.js b/src/zen/tests/mochitests/safebrowsing/browser_whitelisted.js
index c62d41a4f..5848a32ff 100644
--- a/src/zen/tests/mochitests/safebrowsing/browser_whitelisted.js
+++ b/src/zen/tests/mochitests/safebrowsing/browser_whitelisted.js
@@ -40,7 +40,7 @@ add_task(async function testNormalBrowsing() {
     browser: tab.linkedBrowser,
     uriString: TEST_PAGE,
   });
-  testWhitelistedPage(tab.ownerGlobal);
+  testWhitelistedPage(tab.documentGlobal);
 
   info("Load a test page that's no longer whitelisted");
   Services.prefs.setCharPref(PREF_WHITELISTED_HOSTNAMES, "");
@@ -54,5 +54,5 @@ add_task(async function testNormalBrowsing() {
   );
   BrowserTestUtils.startLoadingURIString(tab.linkedBrowser, TEST_PAGE);
   await blockedLoaded;
-  testBlockedPage(tab.ownerGlobal);
+  testBlockedPage(tab.documentGlobal);
 });
diff --git a/src/zen/tests/mochitests/shell/browser.toml b/src/zen/tests/mochitests/shell/browser.toml
index 8f6af8802..79e0e5b60 100644
--- a/src/zen/tests/mochitests/shell/browser.toml
+++ b/src/zen/tests/mochitests/shell/browser.toml
@@ -2,7 +2,10 @@
 
 ["browser_1119088.js"]
 disabled="Disabled by import_external_tests.py"
-support-files = ["mac_desktop_image.py"]
+support-files = [
+  "large.png",
+  "mac_desktop_image.py"
+]
 run-if = [
   "os == 'mac'",
 ]
@@ -12,6 +15,7 @@ skip-if = [
 ]
 
 ["browser_420786.js"]
+support-files = ["large.png"]
 run-if = [
   "os == 'linux' && os_version == '22.04' && arch == 'x86_64' && display == 'wayland'",
   "os == 'linux' && os_version == '24.04' && arch == 'x86_64' && display == 'x11'",
@@ -116,4 +120,5 @@ tags = "os_integration"
 
 ["browser_setDesktopBackgroundPreview.js"]
 disabled="Disabled by import_external_tests.py"
+support-files = ["large.png"]
 tags = "os_integration"
diff --git a/src/zen/tests/mochitests/shell/browser_1119088.js b/src/zen/tests/mochitests/shell/browser_1119088.js
index 6702769a3..2f466c92d 100644
--- a/src/zen/tests/mochitests/shell/browser_1119088.js
+++ b/src/zen/tests/mochitests/shell/browser_1119088.js
@@ -92,20 +92,19 @@ add_setup(async function () {
 /**
  * Tests "Set As Desktop Background" platform implementation on macOS.
  *
- * Sets the desktop background image to the browser logo from the about:logo
- * page and verifies it was set successfully. Setting the desktop background
- * (which uses the nsIShellService::setDesktopBackground() interface method)
- * downloads the image to ~/Pictures using a unique file name and sets the
- * desktop background to the downloaded file leaving the download in place.
- * After setDesktopBackground() is called, the test uses a python script to
- * validate that the current desktop background is in fact set to the
- * downloaded logo.
+ * Sets the desktop background image to the large.png image and verifies it was
+ * set successfully. Setting the desktop background (which uses the
+ * nsIShellService::setDesktopBackground() interface method) downloads the
+ * image to ~/Pictures using a unique file name and sets the desktop background
+ * to the downloaded file leaving the download in place. After
+ * setDesktopBackground() is called, the test uses a python script to validate
+ * that the current desktop background is in fact set to the downloaded image.
  */
 add_task(async function () {
   await BrowserTestUtils.withNewTab(
     {
       gBrowser,
-      url: "about:logo",
+      url: getRootDirectory(gTestPath) + "large.png",
     },
     async () => {
       let dirSvc = Cc["@mozilla.org/file/directory_service;1"].getService(
@@ -140,7 +139,7 @@ add_task(async function () {
 
       // For simplicity, we're going to reach in and access the image on the
       // page directly, which means the page shouldn't be running in a remote
-      // browser. Thankfully, about:logo runs in the parent process for now.
+      // browser. Thankfully, chrome:// runs in the parent process for now.
       Assert.ok(
         !gBrowser.selectedBrowser.isRemoteBrowser,
         "image can be accessed synchronously from the parent process"
diff --git a/src/zen/tests/mochitests/shell/browser_420786.js b/src/zen/tests/mochitests/shell/browser_420786.js
index b9becb49c..1f7beb45c 100644
--- a/src/zen/tests/mochitests/shell/browser_420786.js
+++ b/src/zen/tests/mochitests/shell/browser_420786.js
@@ -12,7 +12,7 @@ add_task(async function () {
   await BrowserTestUtils.withNewTab(
     {
       gBrowser,
-      url: "about:logo",
+      url: getRootDirectory(gTestPath) + "large.png",
     },
     () => {
       var brandName = Services.strings
@@ -46,7 +46,7 @@ add_task(async function () {
 
       // For simplicity, we're going to reach in and access the image on the
       // page directly, which means the page shouldn't be running in a remote
-      // browser. Thankfully, about:logo runs in the parent process for now.
+      // browser. Thankfully, chrome:// runs in the parent process for now.
       Assert.ok(
         !gBrowser.selectedBrowser.isRemoteBrowser,
         "image can be accessed synchronously from the parent process"
diff --git a/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler.js b/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler.js
index 332a7c6f7..04cc1f069 100644
--- a/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler.js
+++ b/src/zen/tests/mochitests/shell/browser_setDefaultPDFHandler.js
@@ -323,14 +323,39 @@ add_task(async function test_setAsDefaultPDFHandler_knownBrowser() {
   }
 });
 
+// Wait for the deferred set_default_pdf_handler_attempt event to be recorded,
+// then return the single event that was emitted by the most recent call.
+async function awaitAttemptEvent() {
+  await TestUtils.waitForCondition(() => {
+    const events = Glean.browser.setDefaultPdfHandlerAttempt.testGetValue();
+    return events && events.length;
+  }, "Recorded set_default_pdf_handler_attempt event");
+  const events = Glean.browser.setDefaultPdfHandlerAttempt.testGetValue();
+  Assert.equal(events.length, 1, "Recorded exactly one attempt event");
+  return events[0];
+}
+
 add_task(async function test_setAsDefaultPDFHandler_fallback() {
   const sandbox = sinon.createSandbox();
+  // Enable the IOpenWithLauncher branch explicitly so the test does not
+  // depend on the build-channel default of
+  // browser.shell.setDefaultPDFHandler.useOpenWith, and use a 0ms wait so
+  // the deferred attempt event fires promptly.
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.shell.setDefaultPDFHandler.useOpenWith", true],
+      ["browser.shell.setDefaultPDFHandler.attemptWaitTimeMs", 0],
+    ],
+  });
 
   try {
     const userChoiceStub = sandbox
       .stub(ShellService, "setAsDefaultPDFHandlerUserChoice")
       .rejects(new Error("mock userChoice failure"));
     sandbox.stub(ShellService, "_isWindows11").returns(true);
+    const isDefaultHandlerForStub = sandbox
+      .stub(ShellService, "isDefaultHandlerFor")
+      .returns(true);
 
     info(
       "When userChoice fails and open-with picker succeeds, should not fall back to settings dialog"
@@ -352,27 +377,42 @@ add_task(async function test_setAsDefaultPDFHandler_fallback() {
       1,
       "Recorded user-choice failure"
     );
+
+    let event = await awaitAttemptEvent();
+    Assert.equal(event.extra.method, "open_with", "Event method is open_with");
+    Assert.equal(event.extra.success, "true", "Event success is true");
     Assert.equal(
-      Glean.browser.setDefaultPdfHandlerUserChoiceResult.Success.testGetValue(),
-      undefined,
-      "Did not record user-choice success"
+      event.extra.result_is_default,
+      "true",
+      "Event result_is_default reflects isDefaultHandlerFor"
     );
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerOpenWithResult.Success.testGetValue(),
-      1,
-      "Recorded open-with success"
-    );
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerOpenWithResult.Failure.testGetValue(),
-      undefined,
-      "Did not record open-with failure"
-    );
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerModernSettingsResult.Success.testGetValue(),
-      undefined,
-      "Did not record modern settings result"
+    Assert.ok(
+      isDefaultHandlerForStub.calledWith(".pdf"),
+      "Sampled isDefaultHandlerFor after the delay"
     );
     userChoiceStub.resetHistory();
+    isDefaultHandlerForStub.resetHistory();
+    launchOpenWithDefaultPickerForFileTypeStub.resetHistory();
+    launchModernSettingsDialogDefaultAppsStub.resetHistory();
+
+    info(
+      "When the picker succeeds but Firefox is not default after the delay, event records result_is_default=false"
+    );
+    Services.fog.testResetFOG();
+    isDefaultHandlerForStub.returns(false);
+    await ShellService.setAsDefaultPDFHandler(false);
+
+    event = await awaitAttemptEvent();
+    Assert.equal(event.extra.method, "open_with", "Event method is open_with");
+    Assert.equal(event.extra.success, "true", "Event success is true");
+    Assert.equal(
+      event.extra.result_is_default,
+      "false",
+      "Event result_is_default is false when Firefox did not become default"
+    );
+    isDefaultHandlerForStub.returns(true);
+    userChoiceStub.resetHistory();
+    isDefaultHandlerForStub.resetHistory();
     launchOpenWithDefaultPickerForFileTypeStub.resetHistory();
     launchModernSettingsDialogDefaultAppsStub.resetHistory();
 
@@ -399,72 +439,120 @@ add_task(async function test_setAsDefaultPDFHandler_fallback() {
       1,
       "Recorded user-choice failure"
     );
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerUserChoiceResult.Success.testGetValue(),
-      undefined,
-      "Did not record user-choice success"
-    );
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerOpenWithResult.Failure.testGetValue(),
-      1,
-      "Recorded open-with failure"
-    );
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerOpenWithResult.Success.testGetValue(),
-      undefined,
-      "Did not record open-with success"
-    );
     Assert.equal(
       Glean.browser.setDefaultPdfHandlerModernSettingsResult.Success.testGetValue(),
       1,
       "Recorded modern settings success"
     );
+
+    event = await awaitAttemptEvent();
     Assert.equal(
-      Glean.browser.setDefaultPdfHandlerModernSettingsResult.Failure.testGetValue(),
-      undefined,
-      "Did not record modern settings failure"
+      event.extra.method,
+      "settings",
+      "Event method is settings (last attempted)"
+    );
+    Assert.equal(
+      event.extra.success,
+      "true",
+      "Event success reflects modern settings launch"
+    );
+    Assert.equal(
+      event.extra.result_is_default,
+      "true",
+      "Event result_is_default reflects isDefaultHandlerFor"
     );
     userChoiceStub.resetHistory();
+    isDefaultHandlerForStub.resetHistory();
     launchOpenWithDefaultPickerForFileTypeStub.resetHistory();
     launchModernSettingsDialogDefaultAppsStub.resetHistory();
 
     info(
-      "When userChoice fails, open-with fails, and modern settings fails, should record all failures"
+      "When userChoice fails, open-with fails, and modern settings fails, event records success=false"
     );
     Services.fog.testResetFOG();
+    isDefaultHandlerForStub.returns(false);
     launchModernSettingsDialogDefaultAppsStub.throws(
       new Error("mock modern settings failure")
     );
     await ShellService.setAsDefaultPDFHandler(false);
 
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerUserChoiceResult.ErrOther.testGetValue(),
-      1,
-      "Recorded user-choice failure"
-    );
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerUserChoiceResult.Success.testGetValue(),
-      undefined,
-      "Did not record user-choice success"
-    );
-    Assert.equal(
-      Glean.browser.setDefaultPdfHandlerOpenWithResult.Failure.testGetValue(),
-      1,
-      "Recorded open-with failure"
-    );
     Assert.equal(
       Glean.browser.setDefaultPdfHandlerModernSettingsResult.Failure.testGetValue(),
       1,
       "Recorded modern settings failure"
     );
+
+    event = await awaitAttemptEvent();
     Assert.equal(
-      Glean.browser.setDefaultPdfHandlerModernSettingsResult.Success.testGetValue(),
-      undefined,
-      "Did not record modern settings success"
+      event.extra.method,
+      "settings",
+      "Event method is settings (last attempted)"
+    );
+    Assert.equal(
+      event.extra.success,
+      "false",
+      "Event success is false when every method failed"
+    );
+    Assert.equal(
+      event.extra.result_is_default,
+      "false",
+      "Event result_is_default is false when no method set the default"
     );
   } finally {
     launchOpenWithDefaultPickerForFileTypeStub.reset();
     launchModernSettingsDialogDefaultAppsStub.reset();
     sandbox.restore();
+    await SpecialPowers.popPrefEnv();
+  }
+});
+
+add_task(async function test_setAsDefaultPDFHandler_useOpenWithDisabled() {
+  const sandbox = sinon.createSandbox();
+  // With useOpenWith disabled, a userChoice failure should skip the
+  // IOpenWithLauncher branch entirely and fall straight through to the
+  // modern settings dialog.
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.shell.setDefaultPDFHandler.useOpenWith", false],
+      ["browser.shell.setDefaultPDFHandler.attemptWaitTimeMs", 0],
+    ],
+  });
+
+  try {
+    sandbox
+      .stub(ShellService, "setAsDefaultPDFHandlerUserChoice")
+      .rejects(new Error("mock userChoice failure"));
+    sandbox.stub(ShellService, "_isWindows11").returns(true);
+    sandbox.stub(ShellService, "isDefaultHandlerFor").returns(true);
+
+    Services.fog.testResetFOG();
+    await ShellService.setAsDefaultPDFHandler(false);
+
+    Assert.ok(
+      launchOpenWithDefaultPickerForFileTypeStub.notCalled,
+      "Did not invoke open-with picker when pref is disabled"
+    );
+    Assert.ok(
+      launchModernSettingsDialogDefaultAppsStub.called,
+      "Fell through to modern settings dialog"
+    );
+
+    const event = await awaitAttemptEvent();
+    Assert.equal(
+      event.extra.method,
+      "settings",
+      "Event method skipped open_with and recorded settings"
+    );
+    Assert.equal(event.extra.success, "true", "Event success is true");
+    Assert.equal(
+      event.extra.result_is_default,
+      "true",
+      "Event result_is_default reflects isDefaultHandlerFor"
+    );
+  } finally {
+    launchOpenWithDefaultPickerForFileTypeStub.reset();
+    launchModernSettingsDialogDefaultAppsStub.reset();
+    sandbox.restore();
+    await SpecialPowers.popPrefEnv();
   }
 });
diff --git a/src/zen/tests/mochitests/shell/browser_setDesktopBackgroundPreview.js b/src/zen/tests/mochitests/shell/browser_setDesktopBackgroundPreview.js
index b847d0998..733123e04 100644
--- a/src/zen/tests/mochitests/shell/browser_setDesktopBackgroundPreview.js
+++ b/src/zen/tests/mochitests/shell/browser_setDesktopBackgroundPreview.js
@@ -16,7 +16,7 @@ add_task(async function () {
   await BrowserTestUtils.withNewTab(
     {
       gBrowser,
-      url: "about:logo",
+      url: getRootDirectory(gTestPath) + "large.png",
     },
     async () => {
       const dialogLoad = BrowserTestUtils.domWindowOpened(null, async win => {
diff --git a/src/zen/tests/mochitests/shell/gtest/SetDefaultBrowserButtonTests.cpp b/src/zen/tests/mochitests/shell/gtest/SetDefaultBrowserButtonTests.cpp
index 18f901df8..d28d077b9 100644
--- a/src/zen/tests/mochitests/shell/gtest/SetDefaultBrowserButtonTests.cpp
+++ b/src/zen/tests/mochitests/shell/gtest/SetDefaultBrowserButtonTests.cpp
@@ -1,4 +1,3 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
diff --git a/src/zen/tests/mochitests/shell/large.png b/src/zen/tests/mochitests/shell/large.png
new file mode 100644
index 000000000..37012cf96
Binary files /dev/null and b/src/zen/tests/mochitests/shell/large.png differ
diff --git a/src/zen/tests/mochitests/shell/unit/test_desktopEntryStatus.js b/src/zen/tests/mochitests/shell/unit/test_desktopEntryStatus.js
new file mode 100644
index 000000000..de9b047e9
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/unit/test_desktopEntryStatus.js
@@ -0,0 +1,131 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ShellService: "moz-src:///browser/components/shell/ShellService.sys.mjs",
+});
+
+const BAREBONES_DESKTOP_ENTRY = `[Desktop Entry]
+Version=1.5
+Type=Application
+Name=test_desktopEntryStatus.js test case
+`;
+
+let gHomeDir;
+let gSystemDir;
+
+const filename = what => `test_desktopEntryStatus_file_${what}.desktop`;
+
+// GLib caches results for efficiency. Unfortunately, it doesn't really provide
+// a way to invalidate that cache, aside from hoping that the file monitor
+// picks up on it. Resolve this by setting up all of the desktop entries at the
+// start, then doing checks, then exiting.
+//
+// (Some others are special-cased, namely absent and Hidden= checks.)
+const kDesktopEntries = [
+  {
+    label: "visible",
+    content: BAREBONES_DESKTOP_ENTRY,
+    expected: Ci.nsIGNOMEShellService.DESKTOP_ENTRY_VISIBLE,
+  },
+  {
+    label: "nodisplay",
+    content: BAREBONES_DESKTOP_ENTRY + "NoDisplay=true\n",
+    expected: Ci.nsIGNOMEShellService.DESKTOP_ENTRY_INVISIBLE,
+  },
+  {
+    label: "onlyshowin-matching",
+    content: BAREBONES_DESKTOP_ENTRY + "OnlyShowIn=FirefoxOS\n",
+    expected: Ci.nsIGNOMEShellService.DESKTOP_ENTRY_VISIBLE,
+  },
+  {
+    label: "onlyshowin-notmatching",
+    content: BAREBONES_DESKTOP_ENTRY + "OnlyShowIn=another\n",
+    expected: Ci.nsIGNOMEShellService.DESKTOP_ENTRY_INVISIBLE,
+  },
+  {
+    label: "notshowin-matching",
+    content: BAREBONES_DESKTOP_ENTRY + "NotShowIn=FirefoxOS\n",
+    expected: Ci.nsIGNOMEShellService.DESKTOP_ENTRY_INVISIBLE,
+  },
+  {
+    label: "notshowin-notmatching",
+    content: BAREBONES_DESKTOP_ENTRY + "NotShowIn=another\n",
+    expected: Ci.nsIGNOMEShellService.DESKTOP_ENTRY_VISIBLE,
+  },
+];
+
+add_setup(async function setup() {
+  let unique = await IOUtils.createUniqueDirectory(
+    Services.dirsvc.get("TmpD", Ci.nsIFile).path,
+    "desktopEntryStatusTest"
+  );
+
+  let homeDir = PathUtils.join(unique, "data-home");
+  Services.env.set("XDG_DATA_HOME", homeDir);
+  gHomeDir = PathUtils.join(homeDir, "applications");
+  await IOUtils.makeDirectory(gHomeDir, { createAncestors: true });
+
+  let systemDir = PathUtils.join(unique, "data-system");
+  Services.env.set("XDG_DATA_DIRS", systemDir);
+  gSystemDir = PathUtils.join(systemDir, "applications");
+  await IOUtils.makeDirectory(gSystemDir, { createAncestors: true });
+
+  Services.env.set("XDG_CURRENT_DESKTOP", "FirefoxOS");
+
+  await IOUtils.writeUTF8(
+    PathUtils.join(gHomeDir, filename("deleted")),
+    BAREBONES_DESKTOP_ENTRY + "Hidden=true\n"
+  );
+  await IOUtils.writeUTF8(
+    PathUtils.join(gSystemDir, filename("deleted")),
+    BAREBONES_DESKTOP_ENTRY
+  );
+
+  for (const desktopEntry of kDesktopEntries) {
+    await IOUtils.writeUTF8(
+      PathUtils.join(gHomeDir, filename(desktopEntry.label + "-home")),
+      desktopEntry.content
+    );
+    await IOUtils.writeUTF8(
+      PathUtils.join(gSystemDir, filename(desktopEntry.label + "-system")),
+      desktopEntry.content
+    );
+  }
+
+  registerCleanupFunction(async () => {
+    return IOUtils.remove(unique, { recursive: true });
+  });
+});
+
+add_task(function test_desktopEntryStatus() {
+  Assert.equal(
+    ShellService.getDesktopEntryStatus(filename("absent")),
+    Ci.nsIGNOMEShellService.DESKTOP_ENTRY_ABSENT,
+    "A desktop entry that doesn't exist should be absent."
+  );
+  Assert.equal(
+    ShellService.getDesktopEntryStatus(filename("hidden")),
+    Ci.nsIGNOMEShellService.DESKTOP_ENTRY_ABSENT,
+    "A desktop entry shadowed by one with the Hidden= attribute should be absent."
+  );
+
+  for (const desktopEntry of kDesktopEntries) {
+    Assert.equal(
+      ShellService.getDesktopEntryStatus(
+        filename(desktopEntry.label + "-home")
+      ),
+      desktopEntry.expected,
+      "Desktop entry matches when at the local level: " + desktopEntry.label
+    );
+    Assert.equal(
+      ShellService.getDesktopEntryStatus(
+        filename(desktopEntry.label + "-system")
+      ),
+      desktopEntry.expected,
+      "Desktop entry matches when at the system level: " + desktopEntry.label
+    );
+  }
+});
diff --git a/src/zen/tests/mochitests/shell/unit/test_maybeCreateLaunchOnLoginOnFirstRun.js b/src/zen/tests/mochitests/shell/unit/test_maybeCreateLaunchOnLoginOnFirstRun.js
new file mode 100644
index 000000000..16106de4d
--- /dev/null
+++ b/src/zen/tests/mochitests/shell/unit/test_maybeCreateLaunchOnLoginOnFirstRun.js
@@ -0,0 +1,109 @@
+/* Any copyright is dedicated to the Public Domain.
+ * https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  StartupOSIntegration:
+    "moz-src:///browser/components/shell/StartupOSIntegration.sys.mjs",
+  WindowsLaunchOnLogin: "resource://gre/modules/WindowsLaunchOnLogin.sys.mjs",
+  sinon: "resource://testing-common/Sinon.sys.mjs",
+});
+
+const PREF = "browser.startup.windowsLaunchOnLogin.defaultEnabled";
+
+async function runWith({ isFirstRun, prefValue, approved }) {
+  let sandbox = sinon.createSandbox();
+  let approvedStub = sandbox
+    .stub(WindowsLaunchOnLogin, "getLaunchOnLoginApproved")
+    .resolves(approved);
+  let createStub = sandbox
+    .stub(WindowsLaunchOnLogin, "createLaunchOnLogin")
+    .resolves();
+
+  if (prefValue === null) {
+    Services.prefs.clearUserPref(PREF);
+  } else {
+    Services.prefs.setBoolPref(PREF, prefValue);
+  }
+
+  try {
+    await StartupOSIntegration.maybeCreateLaunchOnLoginOnFirstRun(isFirstRun);
+    return { approvedStub, createStub };
+  } finally {
+    sandbox.restore();
+    Services.prefs.clearUserPref(PREF);
+  }
+}
+
+add_task(async function test_creates_when_all_conditions_true() {
+  let { createStub } = await runWith({
+    isFirstRun: true,
+    prefValue: true,
+    approved: true,
+  });
+  Assert.ok(
+    createStub.calledOnce,
+    "createLaunchOnLogin should be called when isFirstRun, pref, and approval are all true"
+  );
+});
+
+add_task(async function test_skips_when_not_first_run() {
+  let { createStub, approvedStub } = await runWith({
+    isFirstRun: false,
+    prefValue: true,
+    approved: true,
+  });
+  Assert.ok(
+    !createStub.called,
+    "createLaunchOnLogin should not be called when isFirstRun is false"
+  );
+  Assert.ok(
+    !approvedStub.called,
+    "getLaunchOnLoginApproved should be short-circuited when isFirstRun is false"
+  );
+});
+
+add_task(async function test_skips_when_pref_disabled() {
+  let { createStub, approvedStub } = await runWith({
+    isFirstRun: true,
+    prefValue: false,
+    approved: true,
+  });
+  Assert.ok(
+    !createStub.called,
+    "createLaunchOnLogin should not be called when pref is false"
+  );
+  Assert.ok(
+    !approvedStub.called,
+    "getLaunchOnLoginApproved should be short-circuited when pref is false"
+  );
+});
+
+add_task(async function test_skips_when_windows_policy_denies() {
+  let { createStub, approvedStub } = await runWith({
+    isFirstRun: true,
+    prefValue: true,
+    approved: false,
+  });
+  Assert.ok(
+    approvedStub.calledOnce,
+    "getLaunchOnLoginApproved should be consulted when pref and isFirstRun are true"
+  );
+  Assert.ok(
+    !createStub.called,
+    "createLaunchOnLogin should not be called when Windows policy denies"
+  );
+});
+
+add_task(async function test_uses_pref_default_when_unset() {
+  let { createStub } = await runWith({
+    isFirstRun: true,
+    prefValue: null,
+    approved: true,
+  });
+  Assert.ok(
+    createStub.calledOnce,
+    "createLaunchOnLogin should be called when pref is at its built-in default of true"
+  );
+});
diff --git a/src/zen/tests/mochitests/shell/unit/xpcshell.toml b/src/zen/tests/mochitests/shell/unit/xpcshell.toml
index 4b4a87edc..bfd6f01ea 100644
--- a/src/zen/tests/mochitests/shell/unit/xpcshell.toml
+++ b/src/zen/tests/mochitests/shell/unit/xpcshell.toml
@@ -5,6 +5,11 @@ run-if = [
 firefox-appdir = "browser"
 tags = "os_integration"
 
+["test_desktopEntryStatus.js"]
+run-if = [
+  "os == 'linux'",
+]
+
 ["test_linuxDesktopEntry.js"]
 run-if = [
   "os == 'linux'",
@@ -15,6 +20,11 @@ run-if = [
   "os == 'mac'",
 ]
 
+["test_maybeCreateLaunchOnLoginOnFirstRun.js"]
+run-if = [
+  "os == 'win'"
+]
+
 ["test_secondaryTileJs.js"]
 run-if = [
   "os == 'win'"
diff --git a/src/zen/tests/mochitests/tooltiptext/browser_input_file_tooltips.js b/src/zen/tests/mochitests/tooltiptext/browser_input_file_tooltips.js
index 2f1385f37..7e4cfb9a0 100644
--- a/src/zen/tests/mochitests/tooltiptext/browser_input_file_tooltips.js
+++ b/src/zen/tests/mochitests/tooltiptext/browser_input_file_tooltips.js
@@ -63,7 +63,7 @@ async function do_test(test) {
   if (test.value) {
     info("Creating mock filepicker to select files");
     let MockFilePicker = SpecialPowers.MockFilePicker;
-    MockFilePicker.init(window.browsingContext);
+    MockFilePicker.init();
     MockFilePicker.returnValue = MockFilePicker.returnOK;
     MockFilePicker.displayDirectory = FileUtils.getDir("TmpD", []);
     MockFilePicker.setFiles([tempFile]);
diff --git a/surfer.json b/surfer.json
index bcc52e5b1..74a1fb7b8 100644
--- a/surfer.json
+++ b/surfer.json
@@ -6,7 +6,7 @@
   "version": {
     "product": "firefox",
     "version": "151.0.4",
-    "candidate": "151.0.4",
+    "candidate": "152.0",
     "candidateBuild": 1
   },
   "buildOptions": {