diff --git a/indra/llwindow/llwindowwin32.cpp b/indra/llwindow/llwindowwin32.cpp
index 3cb2911f9a..7e956983d0 100644
--- a/indra/llwindow/llwindowwin32.cpp
+++ b/indra/llwindow/llwindowwin32.cpp
@@ -2587,6 +2587,7 @@ LRESULT CALLBACK LLWindowWin32::mainWindowProc(HWND h_wnd, UINT u_msg, WPARAM w_
             {
                 window_imp->post([=]()
                 {
+                    LL_INFOS("Window") << "Shutting down due to session terminating" << LL_ENDL;
                     // Check if app needs cleanup or can be closed immediately.
                     if (window_imp->mCallbacks->handleSessionExit(window_imp))
                     {
@@ -2605,6 +2606,47 @@ LRESULT CALLBACK LLWindowWin32::mainWindowProc(HWND h_wnd, UINT u_msg, WPARAM w_
             // if session is ending OS is going to take care of it.
             return 0;
         }
+        case WM_POWERBROADCAST:
+        {
+            LL_PROFILE_ZONE_NAMED_CATEGORY_WIN32("mwp - WM_POWERBROADCAST");
+            switch (w_param)
+            {
+            case PBT_APMSUSPEND:
+                LL_INFOS("Window") << "System is suspending (sleep/hibernate)" << LL_ENDL;
+                // System is about to enter sleep or hibernation
+                // Viewer can't function in hibernation, try to shut down.
+                // The system allows approximately two seconds for an
+                // application to handle this notification.
+                window_imp->post([=]()
+                {
+                    LL_INFOS("Window") << "Shutting down due to system suspending (sleep/hibernate)" << LL_ENDL;
+                    if (window_imp->mCallbacks->handleSessionExit(window_imp))
+                    {
+                        // Get the app to initiate cleanup.
+                        window_imp->mCallbacks->handleQuit(window_imp);
+                    }
+                });
+                ms_sleep(1000);
+                return TRUE;
+
+            case PBT_APMRESUMESUSPEND:
+                LL_INFOS("Window") << "System is resuming from suspend" << LL_ENDL;
+                // Shouldn't be up, but log just in case.
+                return TRUE;
+
+            case PBT_APMPOWERSTATUSCHANGE:
+                LL_INFOS("Window") << "Power status has changed" << LL_ENDL;
+                // Power status change (AC/battery)
+                // Viewer requires high performance, not much we can do.
+                // about it, but log for diagnostic purposes (example:
+                // OS trying to throw viewer at an iGPU after this message)
+                return TRUE;
+
+            default:
+                break;
+            }
+            break;
+        }
         case WM_POST_UNINSTALL_:
         {
             LL_PROFILE_ZONE_NAMED_CATEGORY_WIN32("mwp - WM_POST_UNINSTALL_");
diff --git a/indra/newview/llappviewermacosx-objc.h b/indra/newview/llappviewermacosx-objc.h
index 3fbf4202f1..bfbb48dadb 100644
--- a/indra/newview/llappviewermacosx-objc.h
+++ b/indra/newview/llappviewermacosx-objc.h
@@ -31,5 +31,6 @@
 #include <vector>
 
 void force_ns_sxeption();
+void register_url_schemes();
 
 #endif // LL_LLAPPVIEWERMACOSX_OBJC_H
diff --git a/indra/newview/llappviewermacosx-objc.mm b/indra/newview/llappviewermacosx-objc.mm
index 96a6bc6edc..75d6b56e3e 100644
--- a/indra/newview/llappviewermacosx-objc.mm
+++ b/indra/newview/llappviewermacosx-objc.mm
@@ -38,3 +38,28 @@ void force_ns_sxeption()
     NSException *exception = [NSException exceptionWithName:@"Forced NSException" reason:nullptr userInfo:nullptr];
     @throw exception;
 }
+
+void register_url_schemes()
+{
+    @autoreleasepool // Objective-C automatic memory tracking and release.
+    {
+        NSString *bundlePath = [[NSBundle mainBundle] bundlePath];
+        NSURL *bundleURL = [NSURL fileURLWithPath:bundlePath];
+
+        // Force Launch Services to re-register this app bundle
+        OSStatus status = LSRegisterURL((__bridge CFURLRef)bundleURL, true);
+
+        if (status == noErr)
+        {
+            // Explicitly set this app as the default handler for our URL schemes
+            NSArray *schemes = @[@"secondlife", @"x-grid-location-info"];
+            NSString *bundleID = [[NSBundle mainBundle] bundleIdentifier];
+
+            for (NSString *scheme in schemes)
+            {
+                LSSetDefaultHandlerForURLScheme((__bridge CFStringRef)scheme,
+                                               (__bridge CFStringRef)bundleID);
+            }
+        }
+    }
+}
diff --git a/indra/newview/llappviewermacosx.cpp b/indra/newview/llappviewermacosx.cpp
index 2bd9c8661a..830e2d4473 100644
--- a/indra/newview/llappviewermacosx.cpp
+++ b/indra/newview/llappviewermacosx.cpp
@@ -412,6 +412,21 @@ bool LLAppViewerMacOSX::restoreErrorTrap()
     return reset_count == 0;
 }
 
+bool LLAppViewerMacOSX::initSLURLHandler()
+{
+    if (isSecondInstance())
+    {
+        return false;
+    }
+    // Main secondlife:// registration is in info.plist, but macOS
+    // Launch Services caches URL scheme handlers, and a different
+    // viewer might still be registered.
+    // Register URL schemes with Launch Services on every launch
+    register_url_schemes();
+
+    return true;
+}
+
 std::string LLAppViewerMacOSX::generateSerialNumber()
 {
     char serial_md5[MD5HEX_STR_SIZE];       // Flawfinder: ignore
diff --git a/indra/newview/llappviewermacosx.h b/indra/newview/llappviewermacosx.h
index d50812a35e..35fc99dbd9 100644
--- a/indra/newview/llappviewermacosx.h
+++ b/indra/newview/llappviewermacosx.h
@@ -46,6 +46,7 @@ class LLAppViewerMacOSX : public LLAppViewer
 
 protected:
     virtual bool restoreErrorTrap();
+    virtual bool initSLURLHandler();
 
     std::string generateSerialNumber();
     virtual bool initParseCommandLine(LLCommandLineParser& clp);