diff --git a/configuration.nix b/configuration.nix
index 9f3a031..0e630c6 100644
--- a/configuration.nix
+++ b/configuration.nix
@@ -12,6 +12,7 @@
     ./modules/users.nix            # User accounts and global configurations
     ./modules/apps.nix             # All installed packages: apps, CLI tools, dev toolchains
     ./modules/scripts.nix          # Custom system scripts and helpers
+    ./modules/default-apps.nix     # Default app associations (terminal, image viewer, archives), LibreOffice
   ];
 
   # Do not change this value. Read documentation before updating.
diff --git a/dotfiles/quickshell/Theme.qml b/dotfiles/quickshell/Theme.qml
index 5de1909..f06537a 100644
--- a/dotfiles/quickshell/Theme.qml
+++ b/dotfiles/quickshell/Theme.qml
@@ -104,6 +104,11 @@ Item {
             theme.dark ? "1" : "0"];
         gtkSyncProc.running = true;
 
+        qtSyncProc.command = ["qt-theme-set",
+            theme.accent, theme.bg, theme.bgAlt, theme.fg, theme.fgDim, theme.border,
+            theme.dark ? "1" : "0"];
+        qtSyncProc.running = true;
+
         kittySyncProc.command = ["kitty-theme-set",
             theme.accent, theme.bg, theme.bgAlt, theme.fg, theme.fgDim, theme.border];
         kittySyncProc.running = true;
@@ -117,6 +122,7 @@ Item {
     Process { id: saveProc }
     Process { id: hyprSyncProc }
     Process { id: gtkSyncProc }
+    Process { id: qtSyncProc }
     Process { id: kittySyncProc }
     Process { id: rofiSyncProc }
     Process {
diff --git a/hyprland/hyprland.conf b/hyprland/hyprland.conf
index 0683b41..8d9c604 100644
--- a/hyprland/hyprland.conf
+++ b/hyprland/hyprland.conf
@@ -42,6 +42,13 @@ env = XDG_SESSION_DESKTOP,Hyprland
 env = GDK_BACKEND,wayland,x11
 env = QT_QPA_PLATFORM,wayland;xcb
 env = QT_QPA_PLATFORMTHEME,qt6ct
+# Kirigami-based KDE apps (confirmed live: Gwenview's toolbar/statusbar)
+# draw their chrome in QML, not QWidget — outside a real Plasma session
+# they default to their own hardcoded light "Basic" QQC2 style instead of
+# reading qt6ct or kdeglobals at all. org.kde.desktop is the QQC2 style
+# that actually pulls from KColorScheme/kdeglobals like the rest of the
+# theming pipeline here does.
+env = QT_QUICK_CONTROLS_STYLE,org.kde.desktop
 
 # --- Input ------------------------------------------------------------
 input {
diff --git a/modules/default-apps.nix b/modules/default-apps.nix
new file mode 100644
index 0000000..0ef6b29
--- /dev/null
+++ b/modules/default-apps.nix
@@ -0,0 +1,65 @@
+{ config, pkgs, lib, ... }:
+
+{
+  environment.systemPackages = with pkgs; [
+    libreoffice-qt6 # Qt6-styled build — fits the Qt theming work in theme.nix
+                     # better than the default GTK3 build would.
+  ];
+
+  # System-level fallback defaults (XDG spec: only consulted for a
+  # mimetype the user's own ~/.config/mimeapps.list doesn't already
+  # claim), so a future "Open With" choice always wins over this without
+  # needing to touch it. Mimetype lists taken directly from Gwenview's
+  # and Ark's own .desktop files, not guessed.
+  #
+  # One mimetype=desktopfile pair per line: the semicolon only separates
+  # multiple desktop-file candidates for the SAME key, it doesn't chain
+  # separate mimetype=value pairs on one line — mimeapps.list parsers
+  # (verified against xdg-utils' own xdg-mime script) match by scanning
+  # for a line that STARTS WITH "mimetype=", so cramming several pairs
+  # onto one semicolon-joined line silently hides every key after the
+  # first from ever being found.
+  environment.etc."xdg/mimeapps.list".text =
+    let
+      gwenviewMimes = [
+        "inode/directory" "image/avif" "image/gif" "image/heif" "image/jpeg"
+        "image/jxl" "image/png" "image/bmp" "image/x-eps" "image/x-icns"
+        "image/x-ico" "image/x-portable-bitmap" "image/x-portable-graymap"
+        "image/x-portable-pixmap" "image/x-xbitmap" "image/x-xpixmap"
+        "image/tiff" "image/x-psd" "image/x-webp" "image/webp" "image/x-tga"
+        "image/x-xcf" "image/openraster" "image/svg+xml" "image/svg+xml-compressed"
+      ];
+      arkMimes = [
+        "application/x-cd-image" "application/x-bcpio" "application/x-cpio"
+        "application/x-cpio-compressed" "application/x-rpm" "application/x-compress"
+        "application/gzip" "application/x-bzip" "application/x-bzip2"
+        "application/x-lzma" "application/x-xz" "application/zstd" "application/x-lz4"
+        "application/x-source-rpm" "application/vnd.debian.binary-package"
+        "application/vnd.ms-cab-compressed" "application/x-archive" "application/x-tar"
+        "application/x-compressed-tar" "application/x-bzip-compressed-tar"
+        "application/x-bzip2-compressed-tar" "application/x-tarz"
+        "application/x-xz-compressed-tar" "application/x-lzma-compressed-tar"
+        "application/x-7z-compressed" "application/vnd.rar" "application/zip"
+        "application/x-java-archive" "application/x-arj"
+      ];
+      line = desktop: mime: "${mime}=${desktop}";
+    in
+    ''
+      [Default Applications]
+      ${lib.concatMapStringsSep "\n" (line "org.kde.gwenview.desktop") gwenviewMimes}
+      ${lib.concatMapStringsSep "\n" (line "org.kde.ark.desktop") arkMimes}
+    '';
+
+  # Thunar's own "Open Terminal Here" custom action (Edit > Configure
+  # Custom Actions) shipped pointing at `exo-open --launch
+  # TerminalEmulator` — exo isn't installed on this system at all (no
+  # XFCE session, so its helpers.rc mechanism has nothing to resolve
+  # against), so the action silently did nothing. `f`, not `w`: only
+  # creates this baseline for a fresh account — once it exists, further
+  # edits made through Thunar's own UI (adding more custom actions) are
+  # never overwritten by a rebuild.
+  systemd.tmpfiles.rules = [
+    "d /home/nexoniarz/.config/Thunar 0755 nexoniarz users -"
+    ''f /home/nexoniarz/.config/Thunar/uca.xml 0644 nexoniarz users - <?xml version="1.0" encoding="UTF-8"?><actions><action><icon>utilities-terminal</icon><name>Open Terminal Here</name><submenu></submenu><unique-id>1788014825097143-1</unique-id><command>kitty --working-directory %f</command><description>Open a terminal in this folder</description><range></range><patterns>*</patterns><startup-notify/><directories/></action></actions>''
+  ];
+}
diff --git a/modules/scripts.nix b/modules/scripts.nix
index fa6d770..ffa3cd7 100644
--- a/modules/scripts.nix
+++ b/modules/scripts.nix
@@ -12,6 +12,7 @@ let
   displaySet = pkgs.writeShellScriptBin "display-set" (builtins.readFile ./scripts/display-set.sh);
   hyprThemeSet = pkgs.writeShellScriptBin "hypr-theme-set" (builtins.readFile ./scripts/hypr-theme-set.sh);
   gtkThemeSet = pkgs.writeShellScriptBin "gtk-theme-set" (builtins.readFile ./scripts/gtk-theme-set.sh);
+  qtThemeSet = pkgs.writeShellScriptBin "qt-theme-set" (builtins.readFile ./scripts/qt-theme-set.sh);
   kittyThemeSet = pkgs.writeShellScriptBin "kitty-theme-set" (builtins.readFile ./scripts/kitty-theme-set.sh);
   rofiThemeSet = pkgs.writeShellScriptBin "rofi-theme-set" (builtins.readFile ./scripts/rofi-theme-set.sh);
   listCursorThemes = pkgs.writeShellScriptBin "list-cursor-themes" (builtins.readFile ./scripts/list-cursor-themes.sh);
@@ -36,6 +37,7 @@ in
     displaySet
     hyprThemeSet
     gtkThemeSet
+    qtThemeSet
     kittyThemeSet
     rofiThemeSet
     listCursorThemes
diff --git a/modules/scripts/display-set.sh b/modules/scripts/display-set.sh
index 5471e6c..b7c74f5 100644
--- a/modules/scripts/display-set.sh
+++ b/modules/scripts/display-set.sh
@@ -25,7 +25,15 @@ touch "$conf"
 
 line="monitor = $descriptor"
 if grep -q "^monitor = $mon," "$conf" 2>/dev/null; then
-    tmp=$(mktemp)
+    # mktemp in the same directory as $conf, not the default /tmp: /tmp is
+    # a different filesystem here, which makes `mv` below a non-atomic
+    # copy+unlink instead of a rename — Hyprland's file watcher (it
+    # watches every `source=`d file, including this one) could catch the
+    # destination mid-replace and its `source=` glob would find nothing,
+    # throwing "globbing error: found no match" (observed live after an
+    # orientation change, which always hits this branch since DP-1
+    # already has an existing line by then).
+    tmp=$(mktemp "$conf.XXXXXX")
     awk -v prefix="monitor = $mon," -v newline="$line" '
         index($0, prefix) == 1 { print newline; next } { print }
     ' "$conf" > "$tmp"
diff --git a/modules/scripts/gtk-theme-set.sh b/modules/scripts/gtk-theme-set.sh
index d656beb..efa4034 100644
--- a/modules/scripts/gtk-theme-set.sh
+++ b/modules/scripts/gtk-theme-set.sh
@@ -117,3 +117,16 @@ if command -v dconf >/dev/null 2>&1; then
     dconf write /org/gnome/desktop/interface/icon-theme "'$icon_theme'"
     dconf write /org/gnome/desktop/interface/color-scheme "'$color_scheme'"
 fi
+
+# GTK2 compat: separate config format (~/.gtkrc-2.0, not settings.ini),
+# and no live theme-switching mechanism at all — GTK2 apps only read this
+# at their own startup. Only icon theme and font actually follow the
+# current theme; gnome-themes-extra's bundled GTK2 Adwaita engine has no
+# dark variant to switch to (GTK2 predates that concept), so gtk-theme-
+# name here is always the one real option, not a broken attempt at dark
+# mode.
+cat > "$HOME/.gtkrc-2.0" <<EOF
+gtk-theme-name="Adwaita"
+gtk-icon-theme-name="$icon_theme"
+gtk-font-name="Noto Sans 10"
+EOF
diff --git a/modules/scripts/qt-theme-set.sh b/modules/scripts/qt-theme-set.sh
new file mode 100644
index 0000000..a10af4b
--- /dev/null
+++ b/modules/scripts/qt-theme-set.sh
@@ -0,0 +1,105 @@
+#!/usr/bin/env bash
+# Regenerates qt6ct's config + color scheme to match the current Quickshell
+# theme, the Qt-side equivalent of gtk-theme-set. Qt apps (Gwenview, Ark,
+# Kate, ...) had no working platform theme plugin at all before this — the
+# QT_QPA_PLATFORMTHEME=qt6ct env var (hyprland.conf) was pointing at a
+# plugin that wasn't even installed, so every Qt app fell back to
+# whatever default style/palette it shipped with, ignoring the rest of
+# the desktop entirely. style=Fusion (not a KDE/Breeze style) matters
+# specifically: Fusion paints straight from QPalette, so a custom color
+# scheme here is guaranteed to actually show — Breeze-family styles
+# prefer reading colors from kdeglobals instead, which is a separate,
+# static, unrelated leftover file on this machine.
+set -euo pipefail
+
+accent="${1:?usage: qt-theme-set <accent> <bg> <bgAlt> <fg> <fgDim> <border> <dark:1|0>}"
+bg="${2:?bg required}"
+bg_alt="${3:?bgAlt required}"
+fg="${4:?fg required}"
+fg_dim="${5:?fgDim required}"
+border="${6:?border required}"
+dark="${7:?dark required}"
+
+dir="$HOME/.config/qt6ct"
+mkdir -p "$dir/colors"
+
+# qt6ct color scheme files store QPalette::ColorRole values as a fixed-
+# order, comma-separated #aarrggbb list — order and format verified
+# against the example schemes qt6ct itself ships
+# (share/qt6ct/colors/darker.conf etc.), not guessed: WindowText, Button,
+# Light, Midlight, Dark, Mid, Text, BrightText, ButtonText, Base, Window,
+# Shadow, Highlight, HighlightedText, Link, LinkVisited, AlternateBase,
+# NoRole, ToolTipBase, ToolTipText, PlaceholderText.
+a() { printf '#ff%s' "${1#\#}"; }  # opaque
+t() { printf '#80%s' "${1#\#}"; }  # translucent, for PlaceholderText
+
+active="$(a "$fg"), $(a "$bg_alt"), $(a "$border"), $(a "$bg_alt"), $(a "$bg"), $(a "$border"), $(a "$fg"), $(a "$fg"), $(a "$fg"), $(a "$bg"), $(a "$bg"), $(a "$border"), $(a "$accent"), $(a "$bg"), $(a "$accent"), $(a "$accent"), $(a "$bg_alt"), $(a "$bg"), $(a "$bg_alt"), $(a "$fg"), $(t "$fg_dim")"
+disabled="$(a "$fg_dim"), $(a "$bg_alt"), $(a "$border"), $(a "$bg_alt"), $(a "$bg"), $(a "$border"), $(a "$fg_dim"), $(a "$fg_dim"), $(a "$fg_dim"), $(a "$bg"), $(a "$bg"), $(a "$border"), $(a "$accent"), $(a "$fg_dim"), $(a "$accent"), $(a "$accent"), $(a "$bg_alt"), $(a "$bg"), $(a "$bg_alt"), $(a "$fg_dim"), $(t "$fg_dim")"
+
+color_file="$dir/colors/quickshell-theme.conf"
+cat > "$color_file" <<EOF
+[ColorScheme]
+active_colors=$active
+disabled_colors=$disabled
+inactive_colors=$active
+EOF
+
+icon_theme="Gruvbox-Plus-Light"
+[ "$dark" = "1" ] && icon_theme="Gruvbox-Plus-Dark"
+
+cat > "$dir/qt6ct.conf" <<EOF
+[Appearance]
+style=Fusion
+icon_theme=$icon_theme
+custom_palette=true
+color_scheme_path=$color_file
+standard_dialogs=default
+EOF
+
+# qt6ct's palette only reaches classic QWidget UI. Modern KDE apps
+# (confirmed live: Gwenview) draw their toolbar/chrome with Kirigami/QML
+# instead, which ignores QPalette entirely and reads kdeglobals' color
+# groups directly via KColorScheme — so without this, qt6ct alone left
+# exactly that chrome stuck on whatever this machine's stale leftover
+# kdeglobals had (unrelated purple KDE colors from some earlier install),
+# while everything else (dialogs, the actual image viewport, ...)
+# correctly followed the theme.
+rgb() {
+    local hex="${1#\#}"
+    printf '%d,%d,%d' "0x${hex:0:2}" "0x${hex:2:2}" "0x${hex:4:2}"
+}
+
+cat > "$HOME/.config/kdeglobals" <<EOF
+[General]
+ColorScheme=QuickshellTheme
+widgetStyle=Fusion
+
+[KDE]
+widgetStyle=Fusion
+
+[Colors:Window]
+BackgroundNormal=$(rgb "$bg_alt")
+ForegroundNormal=$(rgb "$fg")
+
+[Colors:View]
+BackgroundNormal=$(rgb "$bg")
+ForegroundNormal=$(rgb "$fg")
+
+[Colors:Button]
+BackgroundNormal=$(rgb "$bg_alt")
+ForegroundNormal=$(rgb "$fg")
+
+[Colors:Selection]
+BackgroundNormal=$(rgb "$accent")
+ForegroundNormal=$(rgb "$bg")
+DecorationFocus=$(rgb "$accent")
+DecorationHover=$(rgb "$accent")
+
+[Colors:Tooltip]
+BackgroundNormal=$(rgb "$bg_alt")
+ForegroundNormal=$(rgb "$fg")
+
+[Colors:Header]
+BackgroundNormal=$(rgb "$bg_alt")
+ForegroundNormal=$(rgb "$fg")
+EOF
diff --git a/modules/theme.nix b/modules/theme.nix
index 2daebb3..2219b37 100644
--- a/modules/theme.nix
+++ b/modules/theme.nix
@@ -13,6 +13,16 @@
     adwaita-icon-theme
     gruvbox-plus-icons
     dconf
+    # Qt's side of the same live-theming pipeline as GTK above — see
+    # qt-theme-set (modules/scripts/qt-theme-set.sh). Without this
+    # installed, QT_QPA_PLATFORMTHEME=qt6ct (hyprland.conf) pointed at a
+    # platform theme plugin that didn't exist, so every Qt app (Gwenview,
+    # Ark, Kate, ...) silently fell back to its own default style/palette
+    # instead of anything resembling the rest of the desktop.
+    qt6Packages.qt6ct
+    kdePackages.qqc2-desktop-style # QQC2 style needed for QT_QUICK_CONTROLS_STYLE=
+                                     # org.kde.desktop (hyprland.conf) to actually
+                                     # theme Kirigami-based apps' chrome
   ];
 
   # No environment.sessionVariables.GTK_THEME here on purpose: GTK_THEME
@@ -25,11 +35,16 @@
   systemd.tmpfiles.rules = [
     "d /home/nexoniarz/.config/gtk-3.0 0755 nexoniarz users -"
     "d /home/nexoniarz/.config/gtk-4.0 0755 nexoniarz users -"
+    "d /home/nexoniarz/.config/qt6ct 0755 nexoniarz users -"
+    "d /home/nexoniarz/.config/qt6ct/colors 0755 nexoniarz users -"
     # `f`, not `L+`: created empty only if missing, never overwritten on
-    # rebuild — gtk-theme-set owns the actual content from here on.
+    # rebuild — gtk-theme-set/qt-theme-set own the actual content from
+    # here on.
     "f /home/nexoniarz/.config/gtk-3.0/gtk.css 0644 nexoniarz users - -"
     "f /home/nexoniarz/.config/gtk-4.0/gtk.css 0644 nexoniarz users - -"
     "f /home/nexoniarz/.config/gtk-3.0/settings.ini 0644 nexoniarz users - -"
     "f /home/nexoniarz/.config/gtk-4.0/settings.ini 0644 nexoniarz users - -"
+    "f /home/nexoniarz/.gtkrc-2.0 0644 nexoniarz users - -"
+    "f /home/nexoniarz/.config/qt6ct/qt6ct.conf 0644 nexoniarz users - -"
   ];
 }