diff --git chrome/browser/extensions/api/chrome_extensions_api_client.cc chrome/browser/extensions/api/chrome_extensions_api_client.cc
index f61ec524109fe..92ca490728855 100644
--- chrome/browser/extensions/api/chrome_extensions_api_client.cc
+++ chrome/browser/extensions/api/chrome_extensions_api_client.cc
@@ -15,6 +15,7 @@
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
 #include "build/chromeos_buildflags.h"
+#include "cef/libcef/features/features.h"
 #include "chrome/browser/extensions/api/automation_internal/chrome_automation_internal_api_delegate.h"
 #include "chrome/browser/extensions/api/chrome_device_permissions_prompt.h"
 #include "chrome/browser/extensions/api/declarative_content/chrome_content_rules_registry.h"
@@ -86,6 +87,10 @@
 #include "chrome/browser/extensions/clipboard_extension_helper_chromeos.h"
 #endif
 
+#if BUILDFLAG(ENABLE_CEF)
+#include "cef/libcef/browser/chrome/extensions/chrome_mime_handler_view_guest_delegate_cef.h"
+#endif
+
 #if BUILDFLAG(ENABLE_PRINTING)
 #include "chrome/browser/printing/printing_init.h"
 #endif
@@ -309,7 +314,11 @@ ChromeExtensionsAPIClient::CreateGuestViewManagerDelegate() const {
 std::unique_ptr<MimeHandlerViewGuestDelegate>
 ChromeExtensionsAPIClient::CreateMimeHandlerViewGuestDelegate(
     MimeHandlerViewGuest* guest) const {
+#if BUILDFLAG(ENABLE_CEF)
+  return std::make_unique<ChromeMimeHandlerViewGuestDelegateCef>(guest);
+#else
   return std::make_unique<ChromeMimeHandlerViewGuestDelegate>();
+#endif
 }
 
 WebViewGuestDelegate* ChromeExtensionsAPIClient::CreateWebViewGuestDelegate(
diff --git chrome/browser/extensions/api/tabs/tabs_api.cc chrome/browser/extensions/api/tabs/tabs_api.cc
index d19671bad0e0d..639a1737a0ef5 100644
--- chrome/browser/extensions/api/tabs/tabs_api.cc
+++ chrome/browser/extensions/api/tabs/tabs_api.cc
@@ -1674,7 +1674,7 @@ ExtensionFunction::ResponseAction TabsUpdateFunction::Run() {
       return RespondNow(Error(ExtensionTabUtil::kTabStripNotEditableError));
     }
 
-    if (tab_strip->active_index() != tab_index) {
+    if (tab_strip && tab_strip->active_index() != tab_index) {
       tab_strip->ActivateTabAt(tab_index);
       DCHECK_EQ(contents, tab_strip->GetActiveWebContents());
     }
@@ -1688,7 +1688,7 @@ ExtensionFunction::ResponseAction TabsUpdateFunction::Run() {
     }
 
     bool highlighted = *params->update_properties.highlighted;
-    if (highlighted != tab_strip->IsTabSelected(tab_index)) {
+    if (tab_strip && highlighted != tab_strip->IsTabSelected(tab_index)) {
       tab_strip->ToggleSelectionAt(tab_index);
     }
   }
@@ -1700,7 +1700,7 @@ ExtensionFunction::ResponseAction TabsUpdateFunction::Run() {
         kCannotUpdateMuteCaptured, base::NumberToString(tab_id))));
   }
 
-  if (params->update_properties.opener_tab_id) {
+  if (tab_strip && params->update_properties.opener_tab_id) {
     int opener_id = *params->update_properties.opener_tab_id;
     WebContents* opener_contents = nullptr;
     if (opener_id == tab_id) {
@@ -1735,7 +1735,7 @@ ExtensionFunction::ResponseAction TabsUpdateFunction::Run() {
         ->SetAutoDiscardable(state);
   }
 
-  if (params->update_properties.pinned) {
+  if (tab_strip && params->update_properties.pinned) {
     // Bug fix for crbug.com/1197888. Don't let the extension update the tab if
     // the user is dragging tabs.
     if (!ExtensionTabUtil::IsTabStripEditable()) {
@@ -1756,7 +1756,8 @@ ExtensionFunction::ResponseAction TabsUpdateFunction::Run() {
   // Navigate the tab to a new location if the url is different.
   if (params->update_properties.url) {
     std::string updated_url = *params->update_properties.url;
-    if (browser->profile()->IsIncognitoProfile() &&
+    auto* profile = Profile::FromBrowserContext(browser_context());
+    if (profile->IsIncognitoProfile() &&
         !IsURLAllowedInIncognito(GURL(updated_url))) {
       return RespondNow(Error(ErrorUtils::FormatErrorMessage(
           tabs_constants::kURLsNotAllowedInIncognitoError, updated_url)));
@@ -1771,7 +1772,7 @@ ExtensionFunction::ResponseAction TabsUpdateFunction::Run() {
       return RespondNow(Error(std::move(error)));
     }
 
-    NotifyExtensionTelemetry(Profile::FromBrowserContext(browser_context()),
+    NotifyExtensionTelemetry(profile,
                              extension(), safe_browsing::TabsApiInfo::UPDATE,
                              current_url, updated_url, js_callstack());
   }
diff --git chrome/browser/extensions/extension_tab_util.cc chrome/browser/extensions/extension_tab_util.cc
index 704ad20866c37..081ef3bbf73cc 100644
--- chrome/browser/extensions/extension_tab_util.cc
+++ chrome/browser/extensions/extension_tab_util.cc
@@ -35,6 +35,7 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/types/expected_macros.h"
+#include "cef/libcef/features/features.h"
 #include "chrome/browser/browser_process.h"  // nogncheck
 #include "chrome/browser/extensions/browser_extension_window_controller.h"
 #include "chrome/browser/extensions/chrome_extension_function_details.h"
@@ -81,6 +82,10 @@
 #include "url/url_constants.h"
 #endif
 
+#if BUILDFLAG(ENABLE_CEF)
+#include "cef/libcef/browser/chrome/extensions/chrome_extension_util.h"
+#endif
+
 using content::NavigationEntry;
 using content::WebContents;
 using extensions::mojom::APIPermissionID;
@@ -732,6 +737,14 @@ bool ExtensionTabUtil::GetTabById(int tab_id,
     }
   }
 
+#if BUILDFLAG(ENABLE_CEF)
+  if (cef::GetAlloyTabById(tab_id, profile, include_incognito, out_contents)) {
+    // |out_window| and |out_tab_index| are tied to a specific Browser window,
+    // which doesn't exist for an Alloy style browser.
+    return true;
+  }
+#endif  // BUILDFLAG(ENABLE_CEF)
+
   if (base::FeatureList::IsEnabled(blink::features::kPrerender2InNewTab)) {
     // Prerendering tab is not visible and it cannot be in `TabStripModel`, if
     // the tab id exists as a prerendering tab, and the API will returns
diff --git chrome/browser/ui/tab_helpers.h chrome/browser/ui/tab_helpers.h
index 63848c93738ce..0358e098c7339 100644
--- chrome/browser/ui/tab_helpers.h
+++ chrome/browser/ui/tab_helpers.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_TAB_HELPERS_H_
 
 #include "build/build_config.h"
+#include "cef/libcef/features/features.h"
 
 #if BUILDFLAG(IS_ANDROID)
 
@@ -41,6 +42,10 @@ namespace tabs {
 class TabModel;
 }  // namespace tabs
 
+#if BUILDFLAG(ENABLE_CEF)
+class CefBrowserPlatformDelegateAlloy;
+#endif
+
 // A "tab contents" is a WebContents that is used as a tab in a browser window
 // (or the equivalent on Android). The TabHelpers class allows specific classes
 // to attach the set of tab helpers that is used for tab contents.
@@ -79,6 +84,10 @@ class TabHelpers {
   // Link Preview shows a preview of a page, then promote it as a new tab.
   friend class PreviewTab;
 
+#if BUILDFLAG(ENABLE_CEF)
+  friend class CefBrowserPlatformDelegateAlloy;
+#endif
+
   // FYI: Do NOT add any more friends here. The functions above are the ONLY
   // ones that need to call AttachTabHelpers; if you think you do, re-read the
   // design document linked above, especially the section "Reusing tab helpers".
diff --git chrome/browser/ui/views/download/bubble/download_toolbar_button_view.cc chrome/browser/ui/views/download/bubble/download_toolbar_button_view.cc
index 2df9dfff43c9b..897738dfc8ddf 100644
--- chrome/browser/ui/views/download/bubble/download_toolbar_button_view.cc
+++ chrome/browser/ui/views/download/bubble/download_toolbar_button_view.cc
@@ -812,6 +812,10 @@ void DownloadToolbarButtonView::ShowPendingDownloadStartedAnimation() {
   if (!gfx::Animation::ShouldRenderRichAnimation()) {
     return;
   }
+  if (!IsDrawn()) {
+    // Don't animate with a hidden download button.
+    return;
+  }
   content::WebContents* const web_contents =
       browser_->tab_strip_model()->GetActiveWebContents();
   if (!web_contents ||