diff --git a/lib/common.sh b/lib/common.sh
index 22344c1..ae1a754 100644
--- a/lib/common.sh
+++ b/lib/common.sh
@@ -27,6 +27,8 @@ BOLD='\033[1m'
 RESET='\033[0m'
 
 # Disable colors if output is not a terminal
+# (PURPLE/BLUE/BOLD defined for future use; shellcheck has no way to know that)
+# shellcheck disable=SC2034
 if [ ! -t 1 ]; then
     RED='' GREEN='' YELLOW='' CYAN='' PURPLE='' BLUE='' GRAY='' BOLD='' RESET=''
 fi
diff --git a/setup.sh b/setup.sh
index 64a3276..e56817d 100755
--- a/setup.sh
+++ b/setup.sh
@@ -5,231 +5,231 @@
 #
 set -uo pipefail
 
-#------------------------------------------
-# Color helpers (printf-safe, no tput)
-#------------------------------------------
-RED='\033[0;31m'
-GREEN='\033[0;32m'
-YELLOW='\033[0;33m'
-CYAN='\033[0;36m'
-PURPLE='\033[0;35m'
-BLUE='\033[0;34m'
-GRAY='\033[0;37m'
-BOLD='\033[1m'
-RESET='\033[0m'
-
-# Disable colors if output is not a terminal
-if [ ! -t 1 ]; then
-    RED='' GREEN='' YELLOW='' CYAN='' PURPLE='' BLUE='' GRAY='' BOLD='' RESET=''
-fi
-
-color_yellow() { printf "%b%s%b\n" "$YELLOW" "$*" "$RESET"; }
-color_cyan()   { printf "%b%s%b\n" "$CYAN"   "$*" "$RESET"; }
-color_red()    { printf "%b%s%b\n" "$RED"    "$*" "$RESET"; }
-color_green()  { printf "%b%s%b\n" "$GREEN"  "$*" "$RESET"; }
-color_gray()   { printf "%b%s%b\n" "$GRAY"   "$*" "$RESET"; }
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# shellcheck source=lib/common.sh
+source "$SCRIPT_DIR/lib/common.sh"
+# shellcheck source=lib/session.sh
+source "$SCRIPT_DIR/lib/session.sh"
 
 #------------------------------------------
 # Defaults + argument parsing
 #   DEBUG_MODE must be initialised before anything reads it under set -u.
 #------------------------------------------
-pause_if_debug() {
-    if [[ "${DEBUG_MODE:-false}" == "true" ]]; then
-        echo
-        color_yellow "----------------------------------------------------------------"
-        read -rp "Section complete. Press [Enter] to continue, or [q] to abort: " debug_choice
-        if [[ "${debug_choice,,}" == "q" ]]; then
-            color_red "Script aborted by user."
-            exit 1
-        fi
-        color_yellow "----------------------------------------------------------------"
-        echo
-    fi
+DEBUG_MODE=false
+ASSUME_YES=false
+DE=""
+TWM=""
+
+usage() {
+    cat <<'EOF'
+setup.sh — unified Fedora configuration (Fedora 44+)
+
+Usage:
+  ./setup.sh                              interactive: pick a DE and a TWM
+  ./setup.sh --de=none --twm=niri         non-interactive, explicit choices
+  ./setup.sh --debug                      pause after each section
+
+Options:
+  --de=NAME     gnome | plasma | xfce | none
+  --twm=NAME    chadwm | hyprland | mango | niri | none
+  -y, --yes     never prompt (requires --de and --twm)
+  -d, --debug   pause after each section instead of aborting on error
+  -h, --help    show this help
+
+Valid DE/TWM combinations:
+  any DE + any TWM   DE provides the session, TWM is added alongside it
+  none    + any TWM  TWM-only machine, SDDM is installed as the greeter
+  any DE  + none     plain desktop, no tiling window manager
+  none    + none     refused: that is not a graphical system
+
+Notes:
+  * chadwm is an X11 window manager; the other three are Wayland compositors.
+  * Run as your normal user, not root. sudo is used where needed.
+EOF
 }
 
-install_packages() { sudo dnf install -y "$@"; }
-is_package_installed() { rpm -q "$@" &>/dev/null; }
-
-remove_packages() {
-    local packages_to_remove=()
-    for pkg in "$@"; do
-        if is_package_installed "$pkg"; then
-            packages_to_remove+=("$pkg")
-        fi
-    done
-
-    if [ ${#packages_to_remove[@]} -gt 0 ]; then
-        color_cyan "Removing packages: ${packages_to_remove[*]}"
-        sudo dnf remove -y "${packages_to_remove[@]}"
-    fi
-}
+for arg in "$@"; do
+    case "$arg" in
+        -d|--debug) DEBUG_MODE=true ;;
+        -y|--yes)   ASSUME_YES=true ;;
+        --de=*)     DE="${arg#*=}" ;;
+        --twm=*)    TWM="${arg#*=}" ;;
+        -h|--help)  usage; exit 0 ;;
+        *)
+            err "Unknown argument: $arg"
+            printf "\n"
+            usage
+            exit 2
+            ;;
+    esac
+done
+export DEBUG_MODE ASSUME_YES
 
+if is_debug; then
+    set +e   # walk through failures instead of dying on the first one
+else
+    set -e
+fi
 
 #------------------------------------------
 # Preconditions
 #------------------------------------------
+# clear can fail without TERM (cron, piped install, ssh without a tty) and would
+# abort the whole run under set -e.
+clear 2>/dev/null || true
 
-#------------------------------------------
-# Script Version 1.0
-#------------------------------------------
-clear # Wipe the terminal history view cleanly for the main menu execution
+printf "\n"
+color_yellow "----------------------------------------------------------------"
+color_yellow "Fedora unified configuration"
+color_yellow "----------------------------------------------------------------"
 
-if [[ "$DEBUG_MODE" == "true" ]]; then
-    color_red "!!! DEBUG MODE ENABLED !!!"
-    color_red "The script will pause after each major section."
-    echo
+if [[ ${EUID} -eq 0 ]]; then
+    err "Do not run this as root. Run it as your user; it calls sudo itself."
+    exit 1
 fi
 
-echo
-color_yellow "----------------------------------------------------------------"
-color_yellow "Script version 1.0"
-color_yellow "----------------------------------------------------------------"
-echo
+if [[ "$ASSUME_YES" == "true" && ( -z "$DE" || -z "$TWM" ) ]]; then
+    err "--yes requires explicit --de and --twm, so nothing is guessed on an"
+    err "unattended run. Example:"
+    err "    ./setup.sh --yes --de=none --twm=niri"
+    exit 2
+fi
+
+if is_debug; then
+    color_red "!!! DEBUG MODE ENABLED !!!"
+    color_red "The script will pause after each section."
+fi
 
 #------------------------------------------
 # OS gate — Fedora only, 44+
 #------------------------------------------
-echo
-color_yellow "----------------------------------------------------------------"
-color_yellow "Start OS Detection"
-color_yellow "----------------------------------------------------------------"
-echo
+step "OS detection"
+rule
 
-source /etc/os-release
+# Overridable so the script can be tested on a non-Fedora host.
+OS_RELEASE_FILE="${OS_RELEASE_FILE:-/etc/os-release}"
+# shellcheck source=/dev/null
+source "$OS_RELEASE_FILE"
 
-OS_ID="${ID,,}"
-OS_LIKE="${ID_LIKE:-}"
-OS_LIKE="${OS_LIKE,,}"
-OS_VERSION="${VERSION_ID:-unknown}"
-OS_PRETTY="$PRETTY_NAME"
-OS=""
-SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+OS_ID="${ID:-unknown}"; OS_ID="${OS_ID,,}"
+OS_PRETTY="${PRETTY_NAME:-unknown}"
 
-case "$OS_ID" in
-    fedora) OS="fedora" ;;
-    *)
-        if [[ "$OS_LIKE" == *"fedora"* || "$OS_LIKE" == *"rhel"* ]]; then
-            OS="fedora"
-        fi
-        ;;
-esac
-
-if [[ -n "$OS" ]]; then
-    color_cyan "----------------------------------------------------------------"
-    color_cyan "Detected OS: $OS_PRETTY"
-    color_cyan "Version: $OS_VERSION"
-    color_cyan "----------------------------------------------------------------"
-else
-    color_red "----------------------------------------------------------------"
-    color_red "ERROR: Unsupported or unknown Linux distribution."
-    color_red "Detected: ID=$OS_ID ID_LIKE=${OS_LIKE:-empty}"
-    color_red "----------------------------------------------------------------"
+if [[ "$OS_ID" != "fedora" ]]; then
+    err "Unsupported distribution: $OS_PRETTY (ID=${OS_ID})"
+    err "This repo targets Fedora only. RHEL clones are refused on purpose:"
+    err "they ship no dnf5 config-manager and no RPM Fusion, so both the base"
+    err "setup and every module would fail half-way."
     exit 1
 fi
 
+FEDORA_REL=$(rpm -E %fedora)
+if [[ "$FEDORA_REL" =~ ^[0-9]+$ ]] && (( FEDORA_REL < 44 )); then
+    err "$OS_PRETTY reports release ${FEDORA_REL}, but this setup targets Fedora 44+."
+    exit 1
+fi
+
+ok "Detected: $OS_PRETTY (release ${FEDORA_REL})"
 pause_if_debug
+
 #------------------------------------------
 # 1 Base settings
 #------------------------------------------
-echo
-color_yellow "----------------------------------------------------------------"
-color_yellow "1 Basic Settings"
-color_yellow "----------------------------------------------------------------"
-echo
+step "1 Base settings"
+rule
 
-#------------------------------------------
-# 1.1 Ensure base is ready for installation
-#------------------------------------------
 if ! command -v curl >/dev/null 2>&1; then
     info "curl missing. Installing..."
     install_packages curl
 fi
 
-pause_if_debug
+# config-manager lives in dnf5-plugins; every repo step below depends on it.
+if ! dnf config-manager --help >/dev/null 2>&1; then
+    info "dnf config-manager missing. Installing dnf5-plugins..."
+    install_packages dnf5-plugins
+fi
 
-#------------------------------------------
-# 1.2 Update and Enable Repos + Flatpak
-#------------------------------------------
-color_cyan "Optimizing DNF for speed..."
-
-# 1. Increase parallel downloads (allows downloading multiple packages at once)
-# 2. Set dnf to set YES as default instead of NO
+info "Tuning DNF..."
 sudo dnf config-manager setopt max_parallel_downloads=20
 sudo dnf config-manager setopt defaultyes=True
 
-color_green "DNF optimized. Refreshing metadata..."
+info "Refreshing metadata..."
 sudo dnf makecache --refresh
 
-color_cyan "Enabling RPM Fusion repositories for Fedora $(rpm -E %fedora)..."
+add_rpmfusion_repo
+pause_if_debug
 
-# Define the version variable for readability
-FEDORA_VER=$(rpm -E %fedora)
-
-color_yellow "Checking for updates and sources..."
-sudo dnf check-update || true
-
-# Check if flatpak is installed, if not, install it
-if ! command -v flatpak &> /dev/null; then
-    color_yellow "Flatpak not found. Installing..."
-    sudo dnf install -y flatpak
+if ! command -v flatpak >/dev/null 2>&1; then
+    info "Flatpak missing. Installing..."
+    install_packages flatpak
 fi
+info "Ensuring Flathub is available (system-wide)..."
+sudo flatpak remote-add --if-not-exists --system flathub https://dl.flathub.org/repo/flathub.flatpakrepo
 
-color_cyan "Enabling Flathub..."
-# Using --if-not-exists is good practice to prevent errors on re-runs
-sudo flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
-
-sudo dnf install -y \
-    "https://mirrors.rpmfusion.org/free/fedora/rpmfusion-free-release-${FEDORA_VER}.noarch.rpm" \
-    "https://mirrors.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-${FEDORA_VER}.noarch.rpm"
-
-color_cyan "Enabling full Flathub support..."
-flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
-
-# Update the system
-color_gray "Updating the system"
-echohttps://git.ku-it.org/terrabeam/starburst.git
+info "Updating the system..."
 sudo dnf update -y
 pause_if_debug
-#------------------------------------------
-# Tiling Window Manager Selection
-#------------------------------------------
-echo
-color_yellow "----------------------------------------------------------------"
-color_yellow "Tiling WM Selection"
-color_yellow "----------------------------------------------------------------"
-echo
 
-while true; do
-    echo
-    color_gray "Select a tiling window manager:"
-    echo
-    echo "  1) CHADWM"
-    echo "  2) Hyprland"
-    echo "  3) MangoWC"
-    echo "  4) Niri"
-    echo "  x) None (default)"
-    if ! read -t 15 -rp "Enter choice [1/2/3/4/x] (default: x): " choice; then
-        choice="x"
+#------------------------------------------
+# 2 Menu helpers
+#------------------------------------------
+# $1 = prompt, $2 = default answer, rest = valid answers
+ask_choice() {
+    local prompt="$1" default="$2"; shift 2
+    local answer
+    if [[ "$ASSUME_YES" == "true" ]]; then
+        echo "$default"
+        return 0
     fi
+    while true; do
+        if ! read -t 60 -rp "$prompt (default: $default): " answer; then
+            printf "\n"
+            answer=""
+        fi
+        answer="${answer:-$default}"
+        answer="${answer,,}"
+        local v
+        for v in "$@"; do
+            if [[ "$answer" == "$v" ]]; then
+                echo "$answer"
+                return 0
+            fi
+        done
+        err "Invalid option: '$answer'. Choose from: $*"
+    done
+}
 
-    case "${choice,,}" in
-        1) TWM="chadwm"; break ;;
-        2) TWM="hyprland"; break ;;
-        3) TWM="mango"; break ;;
-        4) TWM="niri"; break ;;
-        x|"") TWM="none"; break ;;
-        *) echo "Invalid option. Please enter 1, 2, 3, 4 or x." ;;
-    esac
-done
-
-echo
-color_cyan "----------------------------------------------------------------"
-color_cyan "Selected Tiling WM: $TWM"
-color_cyan "----------------------------------------------------------------"
-
-pause_if_debug
 #------------------------------------------
-# 5. Tiling Window Manager installation
+# 3 Desktop environment selection
+#------------------------------------------
+if [[ -z "$DE" ]]; then
+    step "3 Desktop environment"
+    rule
+    printf "\n"
+    color_gray "  This system is treated as a bare Fedora install — picking a DE"
+    color_gray "  here is what gives you a graphical login."
+    printf "\n"
+    echo "  1) GNOME     (gdm)"
+    echo "  2) Plasma    (sddm)"
+    echo "  3) XFCE      (lightdm)"
+    echo "  4) None      (TWM only — SDDM will be installed by the TWM module)"
+    printf "\n"
+    choice=$(ask_choice "Select desktop environment [1/2/3/4]" "1" 1 2 3 4)
+    case "$choice" in
+        1) DE="gnome" ;;
+        2) DE="plasma" ;;
+        3) DE="xfce" ;;
+        4) DE="none" ;;
+    esac
+fi
+
+case "$DE" in
+    gnome|plasma|xfce|none) ;;
+    *) err "Unknown --de value: '$DE' (gnome|plasma|xfce|none)"; exit 2 ;;
+esac
+pause_if_debug
+
+#------------------------------------------
+# 4 Tiling window manager selection
 #------------------------------------------
 if [[ -z "$TWM" ]]; then
     step "4 Tiling window manager"
@@ -252,33 +252,74 @@ if [[ -z "$TWM" ]]; then
 fi
 
 case "$TWM" in
-    chadwm|hyprland|mango|niri)
-        color_yellow "Installing $TWM"
-        SCRIPT_NAME="$SCRIPT_DIR/${TWM}.sh"
-        if [[ -f "$SCRIPT_NAME" ]]; then
-            color_cyan "Running $SCRIPT_NAME"
-            source "$SCRIPT_NAME"
-        else
-            color_red "Error: $SCRIPT_NAME not found!"
-            exit 1
-        fi
-        ;;
-    none)
-        color_gray "No tiling window manager selected, skipping TWM installation."
-        ;;
+    niri|hyprland|mango|chadwm|none) ;;
+    *) err "Unknown --twm value: '$TWM' (niri|hyprland|mango|chadwm|none)"; exit 2 ;;
 esac
 
+ok "Selection: DE=${DE} TWM=${TWM}"
+
+# A bare install with neither is not a graphical system. Refuse rather than
+# leave the user with a machine that boots to a black screen.
+if [[ "$DE" == "none" && "$TWM" == "none" ]]; then
+    err "DE=none with TWM=none would leave no graphical session at all."
+    err "Pick a desktop environment, a tiling window manager, or both."
+    exit 2
+fi
 pause_if_debug
 
-echo
-color_yellow "----------------------------------------------------------------"
-color_yellow "End Detection"
-color_yellow "----------------------------------------------------------------"
+#------------------------------------------
+# 5 Dispatch
+#------------------------------------------
+export DE TWM
 
-color_green "Fedora setup complete."
-color_red "The installation has finished. A reboot is recommended."
-# Reboots are dangerous to automate; we use a shorter timeout and default to No
-if read -t 10 -rp "Reboot now? [y/N]: " reboot_choice; then
+run_module() {
+    local path="$1"
+    if [[ ! -f "$path" ]]; then
+        err "Module not found: $path"
+        return 1
+    fi
+    info "Running $(basename "$path")"
+    printf "\n"
+    # Separate process: a module's own shell options and exit codes stay its own.
+    bash "$path"
+}
+
+step "5 Installation"
+rule
+
+if [[ "$DE" != "none" ]]; then
+    run_module "$SCRIPT_DIR/modules/de/${DE}.sh"
+    pause_if_debug
+fi
+
+if [[ "$TWM" != "none" ]]; then
+    run_module "$SCRIPT_DIR/modules/twm/${TWM}.sh"
+    pause_if_debug
+fi
+
+#------------------------------------------
+# 6 Done
+#------------------------------------------
+step "6 Summary"
+rule
+ok "DE:  $DE"
+ok "TWM: $TWM"
+DM=$(detect_display_manager)
+ok "Display manager: ${DM:-none}"
+
+if [[ -z "$DM" ]]; then
+    warn "No display manager is active. You will boot to a text console."
+    warn "Install one, or run a TWM module which sets up SDDM."
+fi
+
+printf "\n"
+color_green "Fedora setup complete. A reboot is recommended."
+if [[ "$ASSUME_YES" == "true" ]]; then
+    info "Unattended run: not rebooting."
+    exit 0
+fi
+
+if read -t 15 -rp "Reboot now? [y/N]: " reboot_choice; then
     case "${reboot_choice,,}" in
         y|yes)
             color_red "Rebooting now."