diff --git a/patches/helium/ui/experiments/compact-action-toolbar.patch b/patches/helium/ui/experiments/compact-action-toolbar.patch
new file mode 100644
index 00000000..bac24559
--- /dev/null
+++ b/patches/helium/ui/experiments/compact-action-toolbar.patch
@@ -0,0 +1,248 @@
+--- a/chrome/browser/helium_flag_choices.h
++++ b/chrome/browser/helium_flag_choices.h
+@@ -30,6 +30,7 @@ namespace helium {
+   constexpr const char kCanvasNoiseCommandLine[] = "fingerprinting-canvas-noise";
+   constexpr const char kAudioContextJitterCommandLine[] = "fingerprinting-audio-context-jitter";
+   constexpr const char kMiddleClickAutoscrollCommandLine[] = "middle-click-autoscroll";
++  constexpr const char kHeliumCatUiCommandLine[] = "helium-cat-ui";
+ 
+ }  // namespace helium
+ 
+--- a/chrome/browser/helium_flag_entries.h
++++ b/chrome/browser/helium_flag_entries.h
+@@ -28,4 +28,8 @@
+      "Middle Click Autoscroll",
+      "Enables autoscroll on middle click. Helium flag, Chromium feature.",
+      kOsDesktop, FEATURE_VALUE_TYPE(blink::features::kHeliumMiddleClickAutoscroll)},
++    {helium::kHeliumCatUiCommandLine,
++     "Helium Compact Action Toolbar UI",
++     "Enables the new experimental UI that merges the tab strip and toolbar into one UI component to save vertical screen estate. Early and buggy, stuff will break and/or look weird. Helium flag.",
++     kOsDesktop, FEATURE_VALUE_TYPE(features::kHeliumCatUi)},
+ #endif  /* CHROME_BROWSER_HELIUM_FLAG_ENTRIES_H_ */
+--- a/chrome/browser/ui/ui_features.cc
++++ b/chrome/browser/ui/ui_features.cc
+@@ -17,6 +17,14 @@
+ 
+ namespace features {
+ 
++// Helium Compact Action Toolbar UI
++BASE_FEATURE(kHeliumCatUi,
++             base::FEATURE_DISABLED_BY_DEFAULT);
++
++bool IsHeliumCatEnabled() {
++  return base::FeatureList::IsEnabled(kHeliumCatUi);
++}
++
+ // Enables the tab dragging fallback when full window dragging is not supported
+ // by the platform (e.g. Wayland). See https://crbug.com/896640
+ BASE_FEATURE(kAllowWindowDragUsingSystemDragDrop,
+--- a/chrome/browser/ui/ui_features.h
++++ b/chrome/browser/ui/ui_features.h
+@@ -20,6 +20,9 @@ namespace features {
+ // All features in alphabetical order. The features should be documented
+ // alongside the definition of their values in the .cc file.
+ 
++BASE_DECLARE_FEATURE(kHeliumCatUi);
++bool IsHeliumCatEnabled();
++
+ // TODO(crbug.com/40598679): Remove this when the tab dragging
+ // interactive_ui_tests pass on Wayland.
+ BASE_DECLARE_FEATURE(kAllowWindowDragUsingSystemDragDrop);
+--- a/chrome/browser/ui/views/frame/browser_view.cc
++++ b/chrome/browser/ui/views/frame/browser_view.cc
+@@ -792,8 +792,12 @@ BrowserView::BrowserView(Browser* browse
+ 
+   top_container_ = AddChildView(std::make_unique<TopContainerView>(this));
+ 
+-  tab_strip_region_view_ =
+-      top_container_->AddChildView(std::make_unique<TabStripRegionView>(this));
++  // When the CAT feature is enabled, tab strip is in the toolbar.
++  // We shouldn't create a duplicate tab strip.
++  if (!features::IsHeliumCatEnabled() || !GetIsNormalType()) {
++    tab_strip_region_view_ =
++        top_container_->AddChildView(std::make_unique<TabStripRegionView>(this));
++  }
+ 
+   if (tabs::IsVerticalTabsFeatureEnabled()) {
+     auto vertical_tab_strip_container =
+@@ -1155,7 +1159,8 @@ bool BrowserView::ShouldDrawTabStrip() c
+   // since callers may otherwise try to access it. Note that we can't just check
+   // this alone, as the tabstrip is created unconditionally even for windows
+   // that won't display it.
+-  return tab_strip_region_view_->tab_strip() != nullptr;
++  return tab_strip_region_view_ != nullptr &&
++         tab_strip_region_view_->tab_strip() != nullptr;
+ }
+ 
+ bool BrowserView::GetIncognito() const {
+@@ -5097,6 +5102,12 @@ void BrowserView::AddedToWidget() {
+ 
+   toolbar_->Init();
+ 
++  // When the CAT feature is enabled, the tab strip is owned by the toolbar.
++  if (features::IsHeliumCatEnabled() && GetIsNormalType()) {
++    tab_strip_region_view_ =
++        static_cast<TabStripRegionView*>(toolbar_->GetTabStripRegionView());
++  }
++
+   if (!base::CommandLine::ForCurrentProcess()->HasSwitch("remove-tabsearch-button"))
+   if (GetIsNormalType()) {
+     if (features::HasTabSearchToolbarButton()) {
+--- a/chrome/browser/ui/views/frame/browser_view_layout.cc
++++ b/chrome/browser/ui/views/frame/browser_view_layout.cc
+@@ -540,6 +540,13 @@ void BrowserViewLayout::LayoutTabStripRe
+     tab_strip_region_view_->SetBounds(0, 0, 0, 0);
+     return;
+   }
++
++  // If the CAT feature is enabled, then the tab strip is in the toolbar.
++  // We shouldn't layout it here.
++  if (features::IsHeliumCatEnabled()) {
++    return;
++  }
++
+   // This retrieves the bounds for the tab strip based on whether or not we show
+   // anything to the left of it, like the incognito avatar.
+   gfx::Rect tab_strip_region_bounds(
+@@ -587,6 +594,12 @@ void BrowserViewLayout::LayoutToolbar(gf
+     toolbar_bounds.set_width(toolbar_bounds.width() -
+                              BrowserView::kVerticalTabStripWidth);
+     toolbar_->SetBoundsRect(toolbar_bounds);
++  } else if (features::IsHeliumCatEnabled()) {
++    gfx::Rect tab_strip_region_bounds(
++        delegate_->GetBoundsForToolbarInVerticalTabBrowserView());
++    int height = toolbar_visible ? toolbar_->GetPreferredSize().height() : 0;
++    toolbar_->SetBounds(tab_strip_region_bounds.x(), available_bounds.y(),
++                        tab_strip_region_bounds.width(), height);
+   } else {
+     int height = toolbar_visible ? toolbar_->GetPreferredSize().height() : 0;
+     int width = available_bounds.width();
+--- a/chrome/browser/ui/views/toolbar/toolbar_view.cc
++++ b/chrome/browser/ui/views/toolbar/toolbar_view.cc
+@@ -57,6 +57,7 @@
+ #include "chrome/browser/ui/views/extensions/extensions_toolbar_coordinator.h"
+ #include "chrome/browser/ui/views/frame/browser_frame_view.h"
+ #include "chrome/browser/ui/views/frame/browser_view.h"
++#include "chrome/browser/ui/views/frame/tab_strip_region_view.h"
+ #include "chrome/browser/ui/views/frame/top_container_background.h"
+ #include "chrome/browser/ui/views/global_media_controls/media_toolbar_button_contextual_menu.h"
+ #include "chrome/browser/ui/views/global_media_controls/media_toolbar_button_view.h"
+@@ -144,6 +145,8 @@ DEFINE_UI_CLASS_PROPERTY_KEY(bool, kActi
+ 
+ namespace {
+ 
++constexpr int kPreferredCompactWidth = 350;
++
+ // Gets the display mode for a given browser.
+ ToolbarView::DisplayMode GetDisplayMode(Browser* browser) {
+ #if BUILDFLAG(IS_CHROMEOS)
+@@ -534,6 +537,26 @@ void ToolbarView::Init() {
+ 
+   reload_->SetVisible(show_reload_button_.GetValue());
+ 
++  // Tab strip should be in the toolbar only when the CAT feature is enabled.
++  if (features::IsHeliumCatEnabled()) {
++    auto tab_strip_region_view =
++        std::make_unique<TabStripRegionView>(browser_view_);
++    tab_strip_region_view_ = tab_strip_region_view.get();
++
++    // Add the tab strip region view to the container view right after
++    // the location bar if it's present.
++    auto location_bar_index = location_bar_ ?
++        container_view_->GetIndexOf(location_bar_) :
++        std::nullopt;
++
++    if (location_bar_index) {
++      container_view_->AddChildViewAt(std::move(tab_strip_region_view),
++                                      *location_bar_index + 1);
++    } else {
++      container_view_->AddChildView(std::move(tab_strip_region_view));
++    }
++  }
++
+   show_avatar_button_.Init(
+       prefs::kShowAvatarButton, prefs,
+       base::BindRepeating(&ToolbarView::OnShowAvatarButtonChanged,
+@@ -700,6 +723,24 @@ bool ToolbarView::IsRectInWindowCaption(
+     return gfx::ToEnclosingRect(rect_in_target_coords_f);
+   };
+ 
++  // Check the tab strip region first if CAT is enabled.
++  if (features::IsHeliumCatEnabled() && tab_strip_region_view_) {
++    const gfx::Rect tab_strip_rect = get_target_rect(tab_strip_region_view_);
++    if (tab_strip_region_view_->GetLocalBounds().Intersects(tab_strip_rect)) {
++      // Check if the rect is actually on the tab strip region view.
++      if (tab_strip_region_view_->HitTestRect(tab_strip_rect)) {
++        auto* tab_strip_region =
++            static_cast<TabStripRegionView*>(tab_strip_region_view_);
++
++        if (tab_strip_region->IsPositionInWindowCaption(tab_strip_rect.origin())) {
++          return true;
++        }
++
++        return false;
++      }
++    }
++  }
++
+   // Check each child view in container_view_ to see if the rect intersects with
+   // any clickable elements. If it does, check if the click is actually on that
+   // element. False if on a clickable element, true if not on a clickable element.
+@@ -998,6 +1039,12 @@ void ToolbarView::InitLayout() {
+   location_bar_->SetProperty(views::kMarginsKey,
+                              gfx::Insets::VH(0, location_bar_margin));
+ 
++  if (features::IsHeliumCatEnabled()) {
++    location_bar_->SetPreferredSize(gfx::Size(kPreferredCompactWidth, 0));
++    location_bar_->SetProperty(views::kMarginsKey,
++                               gfx::Insets::TLBR(0, location_bar_margin, 0, 0));
++  }
++
+   if (extensions_container_) {
+     const views::FlexSpecification extensions_flex_rule =
+         views::FlexSpecification(
+--- a/chrome/browser/ui/views/toolbar/toolbar_view.h
++++ b/chrome/browser/ui/views/toolbar/toolbar_view.h
+@@ -146,6 +146,9 @@ class ToolbarView : public views::Access
+   // Shows a bookmark bubble and anchors it appropriately.
+   void ShowBookmarkBubble(const GURL& url, bool already_bookmarked);
+ 
++  // Returns the tab strip region view if CAT feature is enabled, nullptr otherwise.
++  views::View* GetTabStripRegionView() const { return tab_strip_region_view_.get(); }
++
+   // Accessors.
+   Browser* browser() const { return browser_; }
+   views::Button* GetChromeLabsButton() const;
+@@ -322,6 +325,7 @@ class ToolbarView : public views::Access
+   raw_ptr<BrowserAppMenuButton> app_menu_button_ = nullptr;
+   raw_ptr<views::View> new_tab_button_ = nullptr;
+   raw_ptr<PinnedActionToolbarButton> tab_search_button_ = nullptr;
++  raw_ptr<views::View> tab_strip_region_view_ = nullptr;
+ 
+   const raw_ptr<Browser> browser_;
+   const raw_ptr<BrowserView> browser_view_;
+--- a/chrome/browser/ui/layout_constants.cc
++++ b/chrome/browser/ui/layout_constants.cc
+@@ -187,6 +187,11 @@ gfx::Insets GetLayoutInsets(LayoutInset
+     case TOOLBAR_INTERIOR_MARGIN: {
+       const int vert = GetLayoutConstant(TOP_BAR_VERTICAL_PADDING);
+       const int horiz = vert * 2;
++
++      if (features::IsHeliumCatEnabled()) {
++        return gfx::Insets::VH(vert, horiz + vert);
++      }
++
+       return touch_ui ? gfx::Insets() :
+           gfx::Insets::TLBR(0, horiz, vert, horiz);
+     }
+--- a/chrome/browser/ui/views/omnibox/omnibox_view_views.cc
++++ b/chrome/browser/ui/views/omnibox/omnibox_view_views.cc
+@@ -616,7 +616,7 @@ int OmniboxViewViews::GetUnelidedTextWid
+ }
+ 
+ gfx::Size OmniboxViewViews::GetMinimumSize() const {
+-  constexpr int kMinCharacters = 20;
++  constexpr int kMinCharacters = 32;
+   return gfx::Size(
+       GetFontList().GetExpectedTextWidth(kMinCharacters) + GetInsets().width(),
+       GetPreferredSize().height());
diff --git a/patches/series b/patches/series
index a6f68697..f79bf968 100644
--- a/patches/series
+++ b/patches/series
@@ -255,3 +255,4 @@ helium/ui/improve-flags-webui.patch
 helium/ui/ublock-show-in-settings.patch
 helium/ui/licenses-in-credits.patch
 helium/ui/remove-autofill-link-to-password-manager.patch
+helium/ui/experiments/compact-action-toolbar.patch