diff --git a/README.md b/README.md
index 64f3598..49d5dd0 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,7 @@ Includes:
 * Latest FEX
 * CachyOS Proton 11
 * Desktop mode (KDE)
+* Nested Desktop inside Gaming Mode
 * Bazaar App Store
 * Over-the-air updates
 * Install to internal storage (alongside Android)
@@ -174,6 +175,23 @@ desktop. The **Bazaar** app store and the **Armada Installer**
 ([Install to internal storage](#install-to-internal-storage)) live here. Use the
 **Return to Gaming Mode** shortcut on the desktop to switch back.
 
+To add a desktop application, executable, AppImage, script, or Windows program
+to the Gaming Mode library, right-click its file in Dolphin and choose **Add to
+Steam**.
+
+### Nested Desktop
+
+Armada includes a **Nested Desktop** launcher for running KDE Plasma without
+leaving Gaming Mode. In Desktop Mode, find **Nested Desktop** in the application
+menu, right-click it, and choose **Add to Steam**. Back in Gaming Mode, open its
+properties, select **Armada Native** under **Compatibility**, and set **Game
+Resolution** to **Native**. Then launch it from the **Non-Steam** library.
+
+The nested session uses the same fullscreen KWin path as SteamOS: Gamescope
+controls its surface and input mapping, while the launcher normalizes Armada's
+rotated panel to a 150% landscape Plasma workspace. It also shares the parent
+session's PipeWire audio.
+
 ### Power button and sleep
 
 Pressing the power button does a "fake suspend" (inspired by ROCKNIX) rather than
diff --git a/build_files/10-base-packages.sh b/build_files/10-base-packages.sh
index 466b97d..396a286 100755
--- a/build_files/10-base-packages.sh
+++ b/build_files/10-base-packages.sh
@@ -78,6 +78,7 @@ dnf5 -y install --setopt=install_weak_deps=False \
     plasma-pa \
     plasma-nm \
     bluedevil \
+    upower \
     maliit-keyboard \
     libappindicator-gtk3 \
     libdbusmenu-gtk3 \
diff --git a/build_files/50-create-user.sh b/build_files/50-create-user.sh
index 9f03fc0..45c50cd 100755
--- a/build_files/50-create-user.sh
+++ b/build_files/50-create-user.sh
@@ -16,6 +16,7 @@ done
 install -d -m 0700 -o armada -g armada /var/home/armada
 chown -R armada:armada /var/home/armada
 chmod 0700 /var/home/armada
+install -d -m 0755 -o armada -g armada /var/home/armada/Desktop
 install -Dpm 0755 -o armada -g armada \
     /usr/share/applications/armada-return-to-gamemode.desktop \
     /var/home/armada/Desktop/armada-return-to-gamemode.desktop
diff --git a/system_files/etc/xdg/autostart/armada-desktop-steam.desktop b/system_files/etc/xdg/autostart/armada-desktop-steam.desktop
new file mode 100644
index 0000000..da0a76a
--- /dev/null
+++ b/system_files/etc/xdg/autostart/armada-desktop-steam.desktop
@@ -0,0 +1,9 @@
+[Desktop Entry]
+Type=Application
+Name=Steam Desktop Controls
+Comment=Start Steam to provide gamepad controls in Desktop Mode
+Exec=/usr/libexec/armada/desktop-steam-autostart
+Terminal=false
+OnlyShowIn=KDE;
+X-KDE-autostart-after=panel
+X-KDE-StartupNotify=false
diff --git a/system_files/usr/bin/steamos-add-to-steam b/system_files/usr/bin/steamos-add-to-steam
new file mode 100755
index 0000000..f0fad4b
--- /dev/null
+++ b/system_files/usr/bin/steamos-add-to-steam
@@ -0,0 +1,70 @@
+#!/usr/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Adapted from Valve's steamdeck-kde-presets helper for Armada's ARM client.
+set -euo pipefail
+
+show_dialog=0
+
+usage() {
+    echo "Usage: steamos-add-to-steam [-ui] <file>" >&2
+}
+
+show_error() {
+    if (( show_dialog )) && command -v kdialog >/dev/null 2>&1 &&
+            [[ -n ${DISPLAY:-}${WAYLAND_DISPLAY:-} ]]; then
+        kdialog --title "Add to Steam" --error "$1"
+    else
+        echo "steamos-add-to-steam: $1" >&2
+    fi
+}
+
+if [[ ${1:-} == -ui ]]; then
+    show_dialog=1
+    shift
+fi
+
+if (( EUID == 0 )); then
+    show_error "This command cannot be run as root."
+    exit 1
+fi
+if (( $# != 1 )); then
+    usage
+    exit 2
+fi
+
+if ! file=$(realpath -e -- "$1") || [[ ! -f ${file} ]]; then
+    show_error "File not found: $1"
+    exit 1
+fi
+
+mime=$(kmimetypefinder "${file}")
+case ${mime} in
+    application/x-desktop|application/x-ms-dos-executable|application/x-msdownload|application/vnd.microsoft.portable-executable)
+        ;;
+    application/x-executable|application/vnd.appimage|application/x-shellscript|application/x-sh|text/x-shellscript)
+        if [[ ! -x ${file} ]]; then
+            show_error "The selected file is not executable."
+            exit 1
+        fi
+        ;;
+    *)
+        show_error "Unsupported file type: ${mime}"
+        exit 1
+        ;;
+esac
+
+if [[ ${XDG_SESSION_TYPE:-tty} == tty ]] &&
+        ! pgrep -u "$(id -u)" -f '/steamrtarm64/steam([[:space:]]|$)' >/dev/null 2>&1; then
+    show_error "Steam must be running when this command is used from a terminal session."
+    exit 1
+fi
+
+encoded_url=$(python3 -c \
+    'import sys, urllib.parse; print("steam://addnonsteamgame/" + urllib.parse.quote(sys.argv[1], safe=""))' \
+    "${file}")
+
+# Steam watches this marker while processing the addnonsteamgame URI. The
+# launcher forwards the URI to an existing client or starts the ARM client.
+touch /tmp/addnonsteamgamefile
+nohup /usr/libexec/armada/launch-steam --desktop "${encoded_url}" \
+    </dev/null >/dev/null 2>&1 &
diff --git a/system_files/usr/bin/steamos-nested-desktop b/system_files/usr/bin/steamos-nested-desktop
new file mode 100755
index 0000000..e1763fc
--- /dev/null
+++ b/system_files/usr/bin/steamos-nested-desktop
@@ -0,0 +1,119 @@
+#!/usr/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later
+set -euo pipefail
+
+if [[ ${XDG_SESSION_DESKTOP:-} == KDE || ${KDE_FULL_SESSION:-} == true ]]; then
+    echo "steamos-nested-desktop: refusing to launch inside KDE" >&2
+    if [[ ! -t 1 ]] && command -v kdialog >/dev/null 2>&1; then
+        kdialog --title "Nested Desktop" --sorry \
+            "Nested Desktop should be launched from Gaming Mode."
+    fi
+    exit 0
+fi
+
+state_dir="${XDG_STATE_HOME:-${HOME}/.local/state}/armada"
+install -d -m 0700 "${state_dir}"
+exec >>"${state_dir}/nested-desktop.log" 2>&1
+echo "=== Nested Desktop $(date --iso-8601=seconds) ==="
+
+# Gamescope's overlay and session-specific portals must not leak into Plasma.
+unset LD_PRELOAD XDG_DESKTOP_PORTAL_DIR XDG_SEAT_PATH XDG_SESSION_PATH
+cd "${HOME}"
+
+parent_runtime=${XDG_RUNTIME_DIR:?XDG_RUNTIME_DIR is not set}
+nested_runtime=$(mktemp -d "${parent_runtime}/nested-desktop.XXXXXXXX")
+
+cleanup() {
+    umount --recursive "${nested_runtime}" >/dev/null 2>&1 || true
+    rm -rf --one-file-system -- "${nested_runtime}" || true
+}
+trap cleanup EXIT
+
+# Keep audio connected to the parent Gaming Mode PipeWire session.
+if [[ -S "${parent_runtime}/pulse/native" ]]; then
+    install -d -m 0700 "${nested_runtime}/pulse"
+    ln -s "${parent_runtime}/pulse/native" "${nested_runtime}/pulse/native"
+fi
+shopt -s nullglob
+for socket in "${parent_runtime}"/pipewire-*; do
+    ln -s "${socket}" "${nested_runtime}/${socket##*/}"
+done
+shopt -u nullglob
+
+# Match SteamOS: let Gamescope define the surface, input region, orientation,
+# and pixel geometry instead of imposing a second resolution on nested KWin.
+install -d -m 0700 "${nested_runtime}/bin"
+cat > "${nested_runtime}/bin/kwin_wayland_wrapper" <<'EOF'
+#!/usr/bin/bash
+exec /usr/bin/kwin_wayland_wrapper --fullscreen true --no-lockscreen "$@"
+EOF
+chmod 0755 "${nested_runtime}/bin/kwin_wayland_wrapper"
+
+# Armada changes between a rotated handheld panel and Gamescope's landscape
+# surface. Once KScreen has attached the nested output, use 150% logical scaling
+# on Gamescope's native surface, then remap Plasma Shell so the panel is created
+# on the final screen geometry.
+cat > "${nested_runtime}/bin/start-nested-plasma" <<EOF
+#!/usr/bin/bash
+set -u
+
+/usr/libexec/armada/start-plasma &
+session_pid=\$!
+
+(
+    for _ in {1..60}; do
+        if gdbus call --session --dest org.kde.plasmashell \
+                --object-path /PlasmaShell \
+                --method org.freedesktop.DBus.Peer.Ping \
+                >/dev/null 2>&1; then
+            shell_pid=\$(pgrep -n -x plasmashell)
+            for _ in {1..40}; do
+                if env -u DISPLAY QT_QPA_PLATFORM=wayland \
+                        kscreen-doctor \
+                        output.X11-0.rotation.normal \
+                        output.X11-0.position.0,0 \
+                        output.X11-0.scale.1.5 \
+                        >>"${state_dir}/nested-desktop.log" 2>&1; then
+                    break
+                fi
+                sleep 0.25
+            done
+            gdbus call --session --dest org.kde.plasmashell \
+                --object-path /PlasmaShell \
+                --method org.kde.PlasmaShell.evaluateScript \
+                'panels().forEach(function (panel) { var geometry = screenGeometry(panel.screen); panel.lengthMode = "fill"; panel.minimumLength = geometry.width; panel.maximumLength = geometry.width; });' \
+                >>"${state_dir}/nested-desktop.log" 2>&1 || true
+            sleep 0.5
+            (
+                while IFS= read -r -d '' entry; do
+                    [[ \${entry} == BASH_FUNC_* ]] && continue
+                    export "\${entry}"
+                done < "/proc/\${shell_pid}/environ"
+                unset DISPLAY
+                export QT_QPA_PLATFORM=wayland
+                exec /usr/bin/plasmashell --replace
+            ) >>"${state_dir}/nested-desktop.log" 2>&1 &
+            exit 0
+        fi
+        sleep 0.25
+    done
+) &
+bootstrap_pid=\$!
+
+wait "\${session_pid}"
+status=\$?
+kill "\${bootstrap_pid}" >/dev/null 2>&1 || true
+wait "\${bootstrap_pid}" 2>/dev/null || true
+exit "\${status}"
+EOF
+chmod 0755 "${nested_runtime}/bin/start-nested-plasma"
+
+export PATH="${nested_runtime}/bin:${PATH}"
+export XDG_RUNTIME_DIR="${nested_runtime}"
+export DESKTOP_SESSION=plasma
+export XDG_CURRENT_DESKTOP=KDE
+export XDG_SESSION_DESKTOP=KDE
+export XDG_SESSION_TYPE=wayland
+export ARMADA_NESTED_DESKTOP=1
+
+dbus-run-session "${nested_runtime}/bin/start-nested-plasma"
diff --git a/system_files/usr/libexec/armada/desktop-bootstrap b/system_files/usr/libexec/armada/desktop-bootstrap
index 1bd9420..ff947b2 100755
--- a/system_files/usr/libexec/armada/desktop-bootstrap
+++ b/system_files/usr/libexec/armada/desktop-bootstrap
@@ -2,6 +2,7 @@
 set -euo pipefail
 
 [[ ${XDG_SESSION_TYPE:-} == wayland ]] || exit 0
+[[ ${ARMADA_NESTED_DESKTOP:-0} != 1 ]] || exit 0
 
 activation_env=(
     DESKTOP_SESSION
@@ -24,7 +25,6 @@ config_dir="${XDG_CONFIG_HOME:-${HOME}/.config}/armada"
 rotation_done="${config_dir}/desktop-rotation.done"
 scale_done="${config_dir}/desktop-scale.done"
 
-[[ ! -e "${rotation_done}" || ! -e "${scale_done}" ]] || exit 0
 mkdir -p "${config_dir}"
 
 if command -v /usr/libexec/armada/device-env >/dev/null 2>&1; then
@@ -41,18 +41,20 @@ for _ in {1..5}; do
     sleep 2
 done
 
-if [[ ! -e "${rotation_done}" ]]; then
-    case "${panel_orientation}" in
-        left|right|inverted)
-            if kscreen-doctor "output.${display_connector}.rotation.${panel_orientation}" >/dev/null 2>&1; then
-                touch "${rotation_done}"
-            fi
-            ;;
-        *)
+# KScreen profiles can be rewritten by Gamescope or a nested session. Reapply
+# the physical panel's orientation on every full desktop login.
+case "${panel_orientation}" in
+    left|right|inverted)
+        if kscreen-doctor "output.${display_connector}.rotation.${panel_orientation}" >/dev/null 2>&1; then
             touch "${rotation_done}"
-            ;;
-    esac
-fi
+        fi
+        ;;
+    *)
+        if kscreen-doctor "output.${display_connector}.rotation.normal" >/dev/null 2>&1; then
+            touch "${rotation_done}"
+        fi
+        ;;
+esac
 
 if [[ ! -e "${scale_done}" ]] && kscreen-doctor "output.${display_connector}.scale.1.5" >/dev/null 2>&1; then
     touch "${scale_done}"
diff --git a/system_files/usr/libexec/armada/desktop-steam-autostart b/system_files/usr/libexec/armada/desktop-steam-autostart
new file mode 100755
index 0000000..2dd3e8a
--- /dev/null
+++ b/system_files/usr/libexec/armada/desktop-steam-autostart
@@ -0,0 +1,47 @@
+#!/usr/bin/bash
+set -euo pipefail
+
+# Gaming Mode already owns its Steam process while Nested Desktop is running.
+[[ ${ARMADA_NESTED_DESKTOP:-0} != 1 ]] || exit 0
+
+# Plasma's systemd autostart generator can run applications before plasmashell
+# and Xwayland have attached to the display. Steam's ARM client crashes if it
+# reaches its legacy UI initialization during that window.
+shell_pid=""
+for _ in {1..60}; do
+    shell_pid=$(pgrep -n -u "$(id -u)" -x plasmashell 2>/dev/null || true)
+    [[ -n "${shell_pid}" ]] && break
+    sleep 0.25
+done
+
+# Use the exact display credentials from Plasma rather than the user manager's
+# possibly incomplete early-login environment.
+if [[ -n "${shell_pid}" && -r "/proc/${shell_pid}/environ" ]]; then
+    while IFS= read -r -d '' entry; do
+        [[ ${entry} == BASH_FUNC_* ]] && continue
+        export "${entry}"
+    done < "/proc/${shell_pid}/environ"
+fi
+
+if command -v xprop >/dev/null 2>&1; then
+    for _ in {1..240}; do
+        xprop -root >/dev/null 2>&1 && break
+        sleep 0.25
+    done
+else
+    sleep 10
+fi
+sleep 2
+
+# Avoid opening a second client if Steam was started manually during login.
+# Confirm it survives startup before yielding; a competing early autostart may
+# briefly create the process and then crash.
+if pgrep -u "$(id -u)" -x steam >/dev/null 2>&1; then
+    sleep 5
+    pgrep -u "$(id -u)" -x steam >/dev/null 2>&1 && exit 0
+fi
+
+state_dir="${XDG_STATE_HOME:-${HOME}/.local/state}/armada"
+install -d -m 0700 "${state_dir}"
+exec /usr/libexec/armada/launch-steam --desktop \
+    >>"${state_dir}/desktop-steam.log" 2>&1
diff --git a/system_files/usr/share/applications/steam/steamos-nested-desktop/steamos-nested-desktop.desktop b/system_files/usr/share/applications/steam/steamos-nested-desktop/steamos-nested-desktop.desktop
new file mode 100644
index 0000000..93fd6d6
--- /dev/null
+++ b/system_files/usr/share/applications/steam/steamos-nested-desktop/steamos-nested-desktop.desktop
@@ -0,0 +1,9 @@
+[Desktop Entry]
+Type=Application
+Name=Nested Desktop
+Comment=Run the KDE Plasma desktop inside Gaming Mode
+Exec=/usr/bin/bash /usr/bin/steamos-nested-desktop
+Icon=preferences-desktop-display
+Terminal=false
+Categories=System;
+X-Steam-Controller-Template=Desktop
diff --git a/system_files/usr/share/kio/servicemenus/steam.desktop b/system_files/usr/share/kio/servicemenus/steam.desktop
new file mode 100644
index 0000000..834bc5f
--- /dev/null
+++ b/system_files/usr/share/kio/servicemenus/steam.desktop
@@ -0,0 +1,11 @@
+[Desktop Entry]
+Type=Service
+X-KDE-ServiceTypes=KonqPopupMenu/Plugin
+MimeType=application/x-desktop;application/x-executable;application/vnd.appimage;application/x-shellscript;application/x-sh;application/x-ms-dos-executable;application/x-msdownload;application/vnd.microsoft.portable-executable;text/x-shellscript;
+Actions=addToSteam;
+
+[Desktop Action addToSteam]
+Name=Add to Steam
+Icon=steam
+TryExec=steamos-add-to-steam
+Exec=steamos-add-to-steam -ui %f
diff --git a/system_files/usr/share/plasma/kickeractions/steam.desktop b/system_files/usr/share/plasma/kickeractions/steam.desktop
new file mode 100644
index 0000000..6f60c57
--- /dev/null
+++ b/system_files/usr/share/plasma/kickeractions/steam.desktop
@@ -0,0 +1,9 @@
+[Desktop Entry]
+Type=Service
+Actions=addToSteam;
+
+[Desktop Action addToSteam]
+Name=Add to Steam
+Icon=steam
+TryExec=steamos-add-to-steam
+Exec=steamos-add-to-steam -ui %u
diff --git a/system_files/usr/share/steam/compatibilitytools.d/armada-native/armada-native b/system_files/usr/share/steam/compatibilitytools.d/armada-native/armada-native
new file mode 100755
index 0000000..c5d4626
--- /dev/null
+++ b/system_files/usr/share/steam/compatibilitytools.d/armada-native/armada-native
@@ -0,0 +1,19 @@
+#!/bin/bash
+set -euo pipefail
+
+verb=${1:-}
+[[ -n "$verb" ]] || exit 2
+shift
+
+case "$verb" in
+    run|waitforexitandrun)
+        exec "$@"
+        ;;
+    destroyprefix)
+        exit 0
+        ;;
+    *)
+        echo "Unsupported Armada Native verb: $verb" >&2
+        exit 2
+        ;;
+esac
diff --git a/system_files/usr/share/steam/compatibilitytools.d/armada-native/compatibilitytool.vdf b/system_files/usr/share/steam/compatibilitytools.d/armada-native/compatibilitytool.vdf
new file mode 100644
index 0000000..6bf3224
--- /dev/null
+++ b/system_files/usr/share/steam/compatibilitytools.d/armada-native/compatibilitytool.vdf
@@ -0,0 +1,13 @@
+"compatibilitytools"
+{
+  "compat_tools"
+  {
+    "armada-native"
+    {
+      "install_path" "."
+      "display_name" "Armada Native"
+      "from_oslist" "windows"
+      "to_oslist" "linux"
+    }
+  }
+}
diff --git a/system_files/usr/share/steam/compatibilitytools.d/armada-native/toolmanifest.vdf b/system_files/usr/share/steam/compatibilitytools.d/armada-native/toolmanifest.vdf
new file mode 100644
index 0000000..cc143a9
--- /dev/null
+++ b/system_files/usr/share/steam/compatibilitytools.d/armada-native/toolmanifest.vdf
@@ -0,0 +1,7 @@
+"manifest"
+{
+  "version" "2"
+  "commandline" "/armada-native %verb%"
+  "use_sessions" "0"
+  "compatmanager_layer_name" "native"
+}