diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 203cd097..2ce26955 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     
     container:
       image: elementary/docker:next-unstable
@@ -19,11 +19,10 @@ jobs:
     - name: Install Dependencies
       run: |
         apt update
-        apt install -y libgranite-dev libgtk-3-dev meson valac
+        apt install -y libgranite-7-dev libgtk-4-dev meson valac
     - name: Build
       run: |
         meson build
-        ninja -C build
         ninja -C build install
 
   lint:
diff --git a/.github/workflows/merge.yml b/.github/workflows/merge.yml
index be67f744..35373d09 100644
--- a/.github/workflows/merge.yml
+++ b/.github/workflows/merge.yml
@@ -8,14 +8,14 @@ on:
 jobs:
   gettext:
     name: Gettext
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
 
     steps:
       - name: Checkout
         uses: actions/checkout@v1
 
       - name: Gettext
-        uses: elementary/actions/gettext-template@master
+        uses: elementary/actions/gettext-template@horus
         env:
           GIT_USER_TOKEN: "${{ secrets.GIT_USER_TOKEN }}"
           GIT_USER_NAME: "elementaryBot"
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 1f899f53..3cd8e824 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -10,7 +10,7 @@ on:
 jobs:
   release_deb:
     name: Release (Deb)
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
 
     if: github.event.pull_request.merged == true && true == contains(join(github.event.pull_request.labels.*.name), 'Release')
 
@@ -25,4 +25,4 @@ jobs:
          GIT_USER_NAME: "elementaryBot"
          GIT_USER_EMAIL: "builds@elementary.io"
        with:
-         release_branch: 'odin'
+         release_branch: 'horus'
diff --git a/README.md b/README.md
index 59ce44d8..570520c0 100644
--- a/README.md
+++ b/README.md
@@ -4,9 +4,8 @@
 ## Building, Testing, and Installation
 
 You'll need the following dependencies:
-* libgranite-dev >= 6.0.0
-* libhandy-1
-* libgtk-3.0-dev
+* libgranite-7-dev
+* gtk4
 * libvte-2.91-dev
 * meson
 * valac
diff --git a/meson.build b/meson.build
index 59b7291a..3396cd05 100644
--- a/meson.build
+++ b/meson.build
@@ -12,11 +12,11 @@ systemd_dep = dependency('systemd')
 glib_dep = dependency('glib-2.0')
 gobject_dep = dependency('gobject-2.0')
 gio_dep = dependency('gio-2.0')
-gtk_dep = dependency('gtk+-3.0')
-gdk_dep = [ dependency('gdk-x11-3.0'), dependency('gdk-wayland-3.0') ]
+granite_dep = dependency('granite-7')
+gtk_dep = dependency('gtk4')
+gtk_x11_dep = dependency('gtk4-x11')
+wayland_dep = dependency('gtk4-wayland')
 x11_dep = dependency('x11')
-granite_dep = dependency('granite')
-handy_dep = dependency('libhandy-1')
 
 add_project_arguments(
     '--vapidir', meson.current_source_dir() / 'vapi',
diff --git a/src/Access/Choice.vala b/src/Access/Choice.vala
index e4b9448d..35e7b7e6 100644
--- a/src/Access/Choice.vala
+++ b/src/Access/Choice.vala
@@ -26,7 +26,7 @@ public class Access.Choice : Gtk.Box {
 
         var label = new Gtk.Label (label);
         bind_property ("label", label, "label", BindingFlags.DEFAULT);
-        add (label);
+        append (label);
 
         if (options.n_children () == 0) {
             var check = new Gtk.CheckButton ();
@@ -42,7 +42,7 @@ public class Access.Choice : Gtk.Box {
                 }
             );
 
-            add (check);
+            append (check);
         } else {
             var combo = new Gtk.ComboBoxText ();
             var iter = options.iterator ();
@@ -53,7 +53,7 @@ public class Access.Choice : Gtk.Box {
             }
 
             bind_property ("selected", combo, "active-id", BindingFlags.BIDIRECTIONAL);
-            add (combo);
+            append (combo);
         }
     }
 }
diff --git a/src/Access/Dialog.vala b/src/Access/Dialog.vala
index 13385f3b..af3296c5 100644
--- a/src/Access/Dialog.vala
+++ b/src/Access/Dialog.vala
@@ -41,7 +41,6 @@ public class Access.Dialog : Granite.MessageDialog {
     private Gtk.Button grant_button;
     private Gtk.Button deny_button;
     private List<Choice> choices;
-    private Gtk.Box box;
 
     public Dialog (ButtonAction action, string app_id, string parent_window, string icon) {
         Object (
@@ -54,13 +53,10 @@ public class Access.Dialog : Granite.MessageDialog {
     }
 
     construct {
-        skip_taskbar_hint = true;
         resizable = false;
         modal = true;
 
         choices = new List<Choice> ();
-        set_role ("AccessDialog"); // used in Gala.CloseDialog
-        set_keep_above (true);
 
         if (app_id != "") {
             badge_icon = new DesktopAppInfo (app_id + ".desktop").get_icon ();
@@ -68,24 +64,29 @@ public class Access.Dialog : Granite.MessageDialog {
 
         deny_button = add_button (_("Deny Access"), Gtk.ResponseType.CANCEL) as Gtk.Button;
         grant_button = add_button (_("Grant Access"), Gtk.ResponseType.OK) as Gtk.Button;
-        unowned var grant_context = grant_button.get_style_context ();
 
         if (action == ButtonAction.SUGGESTED) {
-            grant_context.add_class (Gtk.STYLE_CLASS_SUGGESTED_ACTION);
-            set_default (grant_button);
+            grant_button.add_css_class (Granite.STYLE_CLASS_SUGGESTED_ACTION);
+            default_widget = grant_button;
         } else {
-            grant_context.add_class (Gtk.STYLE_CLASS_DESTRUCTIVE_ACTION);
-            set_default (deny_button);
+            grant_button.add_css_class (Granite.STYLE_CLASS_DESTRUCTIVE_ACTION);
+            default_widget = deny_button;
         }
 
-        box = new Gtk.Box (Gtk.Orientation.VERTICAL, 6);
-        custom_bin.child = box;
-        box.show ();
+        custom_bin.orientation = Gtk.Orientation.VERTICAL;
+        custom_bin.spacing = 6;
 
         if (parent_window != "") {
-            realize.connect (() => {
+            ((Gtk.Widget) this).realize.connect (() => {
+                unowned var surface = get_surface ();
+
+                if (surface is Gdk.X11.Surface) {
+                    unowned var x11_surface = (Gdk.X11.Surface) surface;
+                    x11_surface.set_skip_taskbar_hint (true);
+                }
+
                 try {
-                    ExternalWindow.from_handle (parent_window).set_parent_of (get_window ());
+                    ExternalWindow.from_handle (parent_window).set_parent_of (surface);
                 } catch (Error e) {
                     warning ("Failed to associate portal window with parent %s: %s", parent_window, e.message);
                 }
@@ -93,21 +94,14 @@ public class Access.Dialog : Granite.MessageDialog {
         }
 
         show.connect (() => {
-            var window = get_window ();
-            if (window == null) {
-                return;
-            }
-
-            window.focus (Gdk.CURRENT_TIME);
+            present_with_time (Gdk.CURRENT_TIME);
         });
-
-        response.connect_after (destroy);
     }
 
     [DBus (visible = false)]
     public void add_choice (Choice choice) {
         choices.append (choice);
-        box.add (choice);
+        custom_bin.append (choice);
     }
 
     [DBus (visible = false)]
diff --git a/src/Access/Portal.vala b/src/Access/Portal.vala
index 9f4117d4..0dd465b8 100644
--- a/src/Access/Portal.vala
+++ b/src/Access/Portal.vala
@@ -70,13 +70,6 @@ public class Access.Portal : Object {
         var _results = new HashTable<string, Variant> (str_hash, str_equal);
         uint _response = 2;
 
-        dialog.destroy.connect (() => {
-            if (dialog.register_id != 0) {
-                connection.unregister_object (dialog.register_id);
-                dialog.register_id = 0;
-            }
-        });
-
         dialog.response.connect ((id) => {
             switch (id) {
                 case Gtk.ResponseType.OK:
@@ -100,9 +93,12 @@ public class Access.Portal : Object {
             access_dialog.callback ();
         });
 
-        dialog.show_all ();
+        dialog.present ();
         yield;
 
+        connection.unregister_object (dialog.register_id);
+        dialog.destroy ();
+
         results = _results;
         response = _response;
     }
diff --git a/src/AppChooser/AppButton.vala b/src/AppChooser/AppButton.vala
index ea31a721..cf9bcf48 100644
--- a/src/AppChooser/AppButton.vala
+++ b/src/AppChooser/AppButton.vala
@@ -15,22 +15,17 @@ public class AppChooser.AppButton : Gtk.ListBoxRow {
 
         var icon = new Gtk.Image () {
             gicon = app_info.get_icon () ?? new ThemedIcon ("application-default-icon"),
-            icon_size = Gtk.IconSize.DND
+            icon_size = Gtk.IconSize.LARGE
         };
 
         var name = new Gtk.Label (app_info.get_display_name ()) {
             ellipsize = Pango.EllipsizeMode.END
         };
 
-        var grid = new Gtk.Grid () {
-            column_spacing = 6,
-            margin = 3,
-            margin_start = 6,
-            margin_end = 6
-        };
-        grid.add (icon);
-        grid.add (name);
+        var box = new Gtk.Box (Gtk.Orientation.HORIZONTAL, 6);
+        box.append (icon);
+        box.append (name);
 
-        add (grid);
+        child = box;
     }
 }
diff --git a/src/AppChooser/Dialog.vala b/src/AppChooser/Dialog.vala
index fb1c6b60..4c417211 100644
--- a/src/AppChooser/Dialog.vala
+++ b/src/AppChooser/Dialog.vala
@@ -4,7 +4,7 @@
  */
 
 [DBus (name = "org.freedesktop.impl.portal.Request")]
-public class AppChooser.Dialog : Hdy.Window {
+public class AppChooser.Dialog : Gtk.Window {
     public signal void choiced (string app_id);
 
     // The ID used to register this dialog on the DBusConnection
@@ -47,7 +47,6 @@ public class AppChooser.Dialog : Hdy.Window {
     construct {
         buttons = new HashTable<string, AppButton> (str_hash, str_equal);
         AppInfo? info = app_id == "" ? null : new DesktopAppInfo (app_id + ".desktop");
-        Hdy.init ();
 
         var primary_text = _("Open file with…");
         if (filename != "") {
@@ -68,7 +67,7 @@ public class AppChooser.Dialog : Hdy.Window {
              wrap = true,
              xalign = 0
         };
-        primary_label.get_style_context ().add_class (Granite.STYLE_CLASS_PRIMARY_LABEL);
+        primary_label.add_css_class (Granite.STYLE_CLASS_TITLE_LABEL);
 
         var secondary_text = _("An application requested to open a %s.").printf (content_description);
         if (info != null) {
@@ -83,89 +82,101 @@ public class AppChooser.Dialog : Hdy.Window {
             xalign = 0
         };
 
-        var mime_icon = new Gtk.Image () {
-            gicon = content_icon ,
-            icon_size = Gtk.IconSize.DIALOG
+        var mime_icon = new Gtk.Image.from_gicon (content_icon) {
+            pixel_size = 48
         };
 
         var overlay = new Gtk.Overlay () {
+            child = mime_icon,
             valign = Gtk.Align.START
         };
-        overlay.add (mime_icon);
 
         if (info != null) {
-            var badge = new Gtk.Image.from_gicon (info.get_icon (), Gtk.IconSize.LARGE_TOOLBAR) {
+            var badge = new Gtk.Image.from_gicon (info.get_icon ()) {
                 halign = Gtk.Align.END,
-                valign = Gtk.Align.END
+                valign = Gtk.Align.END,
+                pixel_size = 24
             };
 
             overlay.add_overlay (badge);
         }
 
-        var placeholder = new Granite.Widgets.AlertView (
-            _("No installed apps can open %s").printf (content_description),
-            _("New apps can be installed from AppCenter"),
-            "application-default-icon"
-        );
-        placeholder.show_all ();
+        var placeholder = new Granite.Placeholder (_("No installed apps can open %s").printf (content_description)) {
+            description = _("New apps can be installed from AppCenter"),
+            icon = new ThemedIcon ("application-default-icon")
+        };
 
         listbox = new Gtk.ListBox () {
-            expand = true
+            hexpand = true,
+            vexpand = true
         };
+        listbox.add_css_class (Granite.STYLE_CLASS_RICH_LIST);
         listbox.set_placeholder (placeholder);
 
-        var scrolled_window = new Gtk.ScrolledWindow (null, null);
-        scrolled_window.add (listbox);
+        var scrolled_window = new Gtk.ScrolledWindow () {
+            child = listbox
+        };
 
-        var frame = new Gtk.Frame (null);
-        frame.add (scrolled_window);
+        var frame = new Gtk.Frame (null) {
+            child = scrolled_window
+        };
 
-        var cancel = new Gtk.Button.with_label (_("Cancel"));
+        var cancel_button = new Gtk.Button.with_label (_("Cancel"));
 
         open_button = new Gtk.Button.with_label (_("Open")) {
-            can_default = true
+            receives_default = true
         };
-        open_button.get_style_context ().add_class (Gtk.STYLE_CLASS_SUGGESTED_ACTION);
+        open_button.add_css_class (Granite.STYLE_CLASS_SUGGESTED_ACTION);
 
-        var button_box = new Gtk.ButtonBox (Gtk.Orientation.HORIZONTAL) {
-            layout_style = Gtk.ButtonBoxStyle.END,
-            margin_top = 12,
-            spacing = 6
+        var button_box = new Gtk.Box (Gtk.Orientation.HORIZONTAL, 0) {
+            halign = Gtk.Align.END
         };
-
-        button_box.add (cancel);
-        button_box.add (open_button);
+        button_box.append (cancel_button);
+        button_box.append (open_button);
+        button_box.add_css_class ("dialog-action-area");
 
         var grid = new Gtk.Grid () {
             orientation = Gtk.Orientation.VERTICAL,
             column_spacing = 12,
-            row_spacing = 6,
-            margin = 12
+            row_spacing = 6
         };
 
         grid.attach (overlay, 0, 0, 1, 2);
         grid.attach (primary_label, 1, 0);
         grid.attach (secondary_label, 1, 1);
         grid.attach (frame, 0, 3, 2);
-        grid.attach (button_box, 1, 4);
+        grid.add_css_class (Granite.STYLE_CLASS_DIALOG_CONTENT_AREA);
+
+        var box = new Gtk.Box (Gtk.Orientation.VERTICAL, 0);
+        box.append (grid);
+        box.append (button_box);
+        box.add_css_class ("dialog-vbox");
 
-        var window_handle = new Hdy.WindowHandle ();
-        window_handle.add (grid);
+        var window_handle = new Gtk.WindowHandle () {
+            child = box
+        };
 
-        add (window_handle);
-        type_hint = Gdk.WindowTypeHint.DIALOG;
+        child = window_handle;
+
+        // We need to hide the title area
+        titlebar = new Gtk.Grid () {
+            visible = false
+        };
+
+        modal = true;
         default_height = 400;
         default_width = 350;
-        modal = true;
+        default_widget = open_button;
 
-        open_button.grab_default ();
+        add_css_class ("dialog");
+        add_css_class (Granite.STYLE_CLASS_MESSAGE_DIALOG);
 
         if (parent_window != "") {
-            realize.connect (() => {
+            ((Gtk.Widget) this).realize.connect (() => {
                 try {
-                    ExternalWindow.from_handle (parent_window).set_parent_of (get_window ());
+                    ExternalWindow.from_handle (parent_window).set_parent_of (get_surface ());
                 } catch (Error e) {
-                    warning ("Failed to associate portal window with parent window %s: %s", parent_window, e.message);
+                    warning ("Failed to associate portal window with parent %s: %s", parent_window, e.message);
                 }
             });
         }
@@ -175,15 +186,12 @@ public class AppChooser.Dialog : Hdy.Window {
         });
 
         open_button.clicked.connect (() => choiced (((AppChooser.AppButton) listbox.get_selected_row ()).app_id));
-        cancel.clicked.connect (() => choiced (""));
-
-        // close the dialog after a selection;
-        choiced.connect_after (() => destroy ());
+        cancel_button.clicked.connect (() => choiced (""));
     }
 
     private void add_choice (string choice) {
         buttons[choice] = new AppButton (choice);
-        listbox.add (buttons[choice]);
+        listbox.append (buttons[choice]);
     }
 
 
@@ -194,18 +202,17 @@ public class AppChooser.Dialog : Hdy.Window {
                 add_choice (choice);
             }
         }
-        listbox.show_all ();
 
         if (last_choice != "" && !(last_choice in buttons) && last_choice != app_id) {
             add_choice (last_choice);
             buttons[last_choice].grab_focus ();
         }
 
-        open_button.sensitive = listbox.get_children ().length () > 0;
+        open_button.sensitive = listbox.get_row_at_index (0) != null;
     }
 
     [DBus (name = "Close")]
     public void on_close () throws DBusError, IOError {
-        destroy ();
+        choiced ("");
     }
 }
diff --git a/src/AppChooser/Portal.vala b/src/AppChooser/Portal.vala
index 72538609..6988201a 100644
--- a/src/AppChooser/Portal.vala
+++ b/src/AppChooser/Portal.vala
@@ -58,24 +58,10 @@ public class AppChooser.Portal : Object {
             critical (e.message);
         }
 
-
         var _results = new HashTable<string, Variant> (str_hash, str_equal);
         uint _response = 2;
 
-        dialog.destroy.connect (() => {
-            if (dialog.register_id != 0) {
-                connection.unregister_object (dialog.register_id);
-            }
-        });
-
-        var destroy_id = dialog.destroy.connect_after (() => {
-            _results["choice"] = "";
-            choose_application.callback ();
-        });
-
         dialog.choiced.connect ((app_id) => {
-            dialog.disconnect (destroy_id);
-
             _results["choice"] = app_id.replace (".desktop", "");
             _response = app_id == "" ? 1 : 0;
 
@@ -83,9 +69,12 @@ public class AppChooser.Portal : Object {
         });
 
         handles[handle] = dialog;
-        dialog.show_all ();
+        dialog.present ();
         yield;
 
+        connection.unregister_object (dialog.register_id);
+        dialog.destroy ();
+
         results = _results;
         response = _response;
     }
diff --git a/src/ExternalWindow.vala b/src/ExternalWindow.vala
index ab28219b..9341f7bc 100644
--- a/src/ExternalWindow.vala
+++ b/src/ExternalWindow.vala
@@ -20,7 +20,7 @@
  */
 
 public interface ExternalWindow : GLib.Object {
-    public abstract void set_parent_of (Gdk.Window child_window);
+    public abstract void set_parent_of (Gdk.Surface child_surface);
 
     public static ExternalWindow? from_handle (string handle) throws GLib.IOError {
         const string X11_PREFIX = "x11:";
@@ -64,8 +64,8 @@ public class ExternalWindowX11 : ExternalWindow, GLib.Object {
         }
 
         Gdk.set_allowed_backends ("x11");
-        x11_display = Gdk.Display.open (null);
-        Gdk.set_allowed_backends (null);
+        x11_display = Gdk.Display.open ("");
+        Gdk.set_allowed_backends ("*");
 
         if (x11_display == null) {
             warning ("Failed to open X11 display");
@@ -74,21 +74,21 @@ public class ExternalWindowX11 : ExternalWindow, GLib.Object {
         return x11_display;
     }
 
-    public void set_parent_of (Gdk.Window child_window) {
+    public void set_parent_of (Gdk.Surface child_surface) {
         unowned var display = (Gdk.X11.Display) get_x11_display ();
         unowned var x_display = display.get_xdisplay ();
-        var child_xid = ((Gdk.X11.Window) child_window).get_xid ();
+        var child_xid = ((Gdk.X11.Surface) child_surface).get_xid ();
 
         x_display.set_transient_for_hint (child_xid, foreign_window);
 
-        var atom = Gdk.X11.get_xatom_by_name_for_display (display, "_NET_WM_WINDOW_TYPE_DIALOG");
+        var dialog_atom = display.get_xatom_by_name ("_NET_WM_WINDOW_TYPE_DIALOG");
         x_display.change_property (
             child_xid,
-            Gdk.X11.get_xatom_by_name_for_display (display, "_NET_WM_WINDOW_TYPE"),
+            display.get_xatom_by_name ("_NET_WM_WINDOW_TYPE"),
             X.XA_ATOM,
             32,
             X.PropMode.Replace,
-            (uchar[]) atom,
+            (uchar[]) dialog_atom,
             1
         );
     }
@@ -114,8 +114,8 @@ public class ExternalWindowWayland : ExternalWindow, GLib.Object {
         }
 
         Gdk.set_allowed_backends ("wayland");
-        wayland_display = Gdk.Display.open (null);
-        Gdk.set_allowed_backends (null);
+        wayland_display = Gdk.Display.open ("");
+        Gdk.set_allowed_backends ("*");
 
         if (wayland_display == null) {
             warning ("Failed to open Wayland display");
@@ -124,8 +124,8 @@ public class ExternalWindowWayland : ExternalWindow, GLib.Object {
         return wayland_display;
     }
 
-    public void set_parent_of (Gdk.Window child_window) {
-        if (!((Gdk.Wayland.Window) child_window).set_transient_for_exported (handle)) {
+    public void set_parent_of (Gdk.Surface child_surface) {
+        if (!((Gdk.Wayland.Toplevel) child_surface).set_transient_for_exported (handle)) {
             warning ("Failed to set portal window transient for external parent");
         }
     }
diff --git a/src/XdgDesktopPortalPantheon.vala b/src/XdgDesktopPortalPantheon.vala
index f1c282ad..e0af6142 100644
--- a/src/XdgDesktopPortalPantheon.vala
+++ b/src/XdgDesktopPortalPantheon.vala
@@ -33,17 +33,17 @@ private const GLib.OptionEntry[] OPTIONS_ENTRIES = {
 private void on_bus_acquired (DBusConnection connection, string name) {
     try {
         connection.register_object ("/org/freedesktop/portal/desktop", new Access.Portal (connection));
-        debug ("Access Portal registed!");
+        debug ("Access Portal registered!");
 
         connection.register_object ("/org/freedesktop/portal/desktop", new AppChooser.Portal (connection));
-        debug ("AppChooser Portal registred!");
+        debug ("AppChooser Portal registered!");
     } catch (Error e) {
         critical ("Unable to register the object: %s", e.message);
     }
 }
 
 private void on_name_acquired () {
-    debug ("org.freedesktop.impl.portal.desktop.panthon acquired");
+    debug ("org.freedesktop.impl.portal.desktop.pantheon acquired");
 
     // We're probably being started by xdg-desktop-portal, which won't be fully initialised until all the backends have loaded.
     // Granite depends on the settings portal to get the style preference, but can't DBus activate it because it's already starting.
@@ -75,7 +75,7 @@ int main (string[] args) {
     /* Avoid pointless and confusing recursion */
     GLib.Environment.unset_variable ("GTK_USE_PORTAL");
 
-    Gtk.init (ref args);
+    Gtk.init ();
 
     try {
         var opt_context = new OptionContext ("- portal backends");
diff --git a/src/meson.build b/src/meson.build
index 47be37af..1155dfd6 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -13,11 +13,11 @@ executable(
         glib_dep,
         gobject_dep,
         gio_dep,
-        gtk_dep,
-        gdk_dep,
-        x11_dep,
         granite_dep,
-        handy_dep
+        gtk_dep,
+        gtk_x11_dep,
+        wayland_dep,
+        x11_dep
     ],
     install: true,
     install_dir: libexecdir