diff --git chrome/app/chrome_main_delegate.cc chrome/app/chrome_main_delegate.cc
index 313975f42c0d..ee7f27dab6b7 100644
--- chrome/app/chrome_main_delegate.cc
+++ chrome/app/chrome_main_delegate.cc
@@ -27,6 +27,7 @@
 #include "base/time/time.h"
 #include "base/trace_event/trace_event_impl.h"
 #include "build/build_config.h"
+#include "cef/libcef/features/runtime.h"
 #include "chrome/browser/chrome_content_browser_client.h"
 #include "chrome/browser/chrome_resource_bundle_helper.h"
 #include "chrome/browser/defaults.h"
@@ -379,6 +380,8 @@ struct MainFunction {
 
 // Initializes the user data dir. Must be called before InitializeLocalState().
 void InitializeUserDataDir(base::CommandLine* command_line) {
+  if (cef::IsChromeRuntimeEnabled())
+    return;
 #if defined(OS_WIN)
   // Reach out to chrome_elf for the truth on the user data directory.
   // Note that in tests, this links to chrome_elf_test_stubs.
@@ -624,7 +627,9 @@ void ChromeMainDelegate::PostFieldTrialInitialization() {
   }
 
 #if defined(OS_WIN)
+  if (!cef::IsChromeRuntimeEnabled()) {
   SetUpExtendedCrashReporting(is_browser_process);
+  }
   base::sequence_manager::internal::ThreadControllerPowerMonitor::
       InitializeOnMainThread();
 #endif
@@ -906,6 +911,7 @@ void ChromeMainDelegate::PreSandboxStartup() {
   std::string process_type =
       command_line.GetSwitchValueASCII(switches::kProcessType);
 
+  if (!cef::IsChromeRuntimeEnabled()) {
   crash_reporter::InitializeCrashKeys();
 
 #if defined(OS_POSIX)
@@ -916,6 +922,7 @@ void ChromeMainDelegate::PreSandboxStartup() {
   InitMacCrashReporter(command_line, process_type);
   SetUpInstallerPreferences(command_line);
 #endif
+  }  // !cef::IsChromeRuntimeEnabled()
 
 #if defined(OS_WIN)
   child_process_logging::Init();
@@ -1040,6 +1047,7 @@ void ChromeMainDelegate::PreSandboxStartup() {
         locale;
   }
 
+  if (!cef::IsChromeRuntimeEnabled()) {
 #if defined(OS_POSIX) && !defined(OS_MAC)
   // Zygote needs to call InitCrashReporter() in RunZygote().
   if (process_type != service_manager::switches::kZygoteProcess) {
@@ -1072,6 +1080,7 @@ void ChromeMainDelegate::PreSandboxStartup() {
   // After all the platform Breakpads have been initialized, store the command
   // line for crash reporting.
   crash_keys::SetCrashKeysFromCommandLine(command_line);
+  }  // !cef::IsChromeRuntimeEnabled()
 
 #if BUILDFLAG(ENABLE_PDF)
   MaybeInitializeGDI();
@@ -1170,6 +1179,7 @@ void ChromeMainDelegate::ZygoteForked() {
     SetUpProfilingShutdownHandler();
   }
 
+  if (!cef::IsChromeRuntimeEnabled()) {
   // Needs to be called after we have chrome::DIR_USER_DATA.  BrowserMain sets
   // this up for the browser process in a different manner.
   const base::CommandLine* command_line =
@@ -1186,6 +1196,7 @@ void ChromeMainDelegate::ZygoteForked() {
 
   // Reset the command line for the newly spawned process.
   crash_keys::SetCrashKeysFromCommandLine(*command_line);
+  }  // !cef::IsChromeRuntimeEnabled()
 }
 
 #endif  // defined(OS_LINUX) || defined(OS_CHROMEOS)
diff --git chrome/browser/chrome_browser_main.cc chrome/browser/chrome_browser_main.cc
index 68a92d3924f0..280ef9019551 100644
--- chrome/browser/chrome_browser_main.cc
+++ chrome/browser/chrome_browser_main.cc
@@ -49,6 +49,7 @@
 #include "build/build_config.h"
 #include "build/lacros_buildflags.h"
 #include "cc/base/switches.h"
+#include "cef/libcef/features/runtime.h"
 #include "chrome/browser/about_flags.h"
 #include "chrome/browser/active_use_util.h"
 #include "chrome/browser/after_startup_task_utils.h"
@@ -892,8 +893,10 @@ int ChromeBrowserMainParts::PreCreateThreadsImpl() {
 #if !defined(OS_ANDROID)
   // Create the RunLoop for MainMessageLoopRun() to use, and pass a copy of
   // its QuitClosure to the BrowserProcessImpl to call when it is time to exit.
+  // CEF with the Chrome runtime will create and manage its own RunLoop.
   DCHECK(!g_run_loop);
-  g_run_loop = new base::RunLoop;
+  if (!cef::IsChromeRuntimeEnabled())
+    g_run_loop = new base::RunLoop;
 
   // These members must be initialized before returning from this function.
   // Android doesn't use StartupBrowserCreator.
@@ -1608,11 +1611,13 @@ int ChromeBrowserMainParts::PreMainMessageLoopRunImpl() {
   // This step is costly and is already measured in
   // Startup.StartupBrowserCreator_Start.
   // See the comment above for an explanation of |process_command_line|.
+  // Bypass StartupBrowserCreator with CEF where |g_run_loop| is nullptr.
   const bool started =
+      !g_run_loop ||
       !process_command_line ||
       browser_creator_->Start(parsed_command_line(), base::FilePath(), profile_,
                               last_opened_profiles);
-  if (started) {
+  if (started && g_run_loop) {
 #if defined(OS_WIN) || (defined(OS_LINUX) && !defined(OS_CHROMEOS))
     // Initialize autoupdate timer. Timer callback costs basically nothing
     // when browser is not in persistent mode, so it's OK to let it ride on
diff --git chrome/browser/notifications/notification_platform_bridge_mac.mm chrome/browser/notifications/notification_platform_bridge_mac.mm
index ad52e63ed83a..6b16ee3ccc96 100644
--- chrome/browser/notifications/notification_platform_bridge_mac.mm
+++ chrome/browser/notifications/notification_platform_bridge_mac.mm
@@ -24,6 +24,7 @@
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/system/sys_info.h"
+#include "cef/libcef/features/runtime.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/notifications/notification_common.h"
 #include "chrome/browser/notifications/notification_display_service_impl.h"
@@ -651,6 +652,12 @@ getDisplayedAlertsForProfileId:(NSString*)profileId
 - (id<NotificationDelivery>)serviceProxy {
   id<NotificationDelivery> proxy = [_xpcConnection remoteObjectProxy];
 
+  // Skip exception port configuration when running CEF with crash reporting disabled.
+  if (!_setExceptionPort && cef::IsChromeRuntimeEnabled() &&
+      !cef::IsCrashReportingEnabled()) {
+    _setExceptionPort = YES;
+  }
+
   if (!_setExceptionPort) {
     base::mac::ScopedMachSendRight exceptionPort(
         crash_reporter::GetCrashpadClient().GetHandlerMachPort());
diff --git ui/gtk/select_file_dialog_impl_kde.cc ui/gtk/select_file_dialog_impl_kde.cc
index 464aa72e1d47..30a621dea6fc 100644
--- ui/gtk/select_file_dialog_impl_kde.cc
+++ ui/gtk/select_file_dialog_impl_kde.cc
@@ -6,6 +6,8 @@
 #include <gtk/gtk.h>
 #include <stddef.h>
 
+#undef Success
+
 #include <memory>
 #include <set>