diff --git a/.gitea/workflows/ci.yml b/.gitea/workflows/ci.yml
new file mode 100644
index 0000000..1627800
--- /dev/null
+++ b/.gitea/workflows/ci.yml
@@ -0,0 +1,47 @@
+name: CI
+
+# K-114 (nexus-hub): Mini-CI für proxmox-scripts — Syntax, build.func-Source-
+# Pflicht und Validierungs-Unit-Tests. Läuft auf dem instanzweiten Runner
+# (Label homelab, ohne Deploy-Rechte — PR #6 / ct/runner.sh).
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  lint:
+    name: Shell-Lint (bash -n, source-check, Validierungs-Tests)
+    runs-on: homelab
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: bash -n über alle Scripts
+        run: |
+          status=0
+          for f in ct/*.sh install/*.sh lib/*.func tests/*.sh; do
+            if bash -n "$f"; then
+              echo "ok     $f"
+            else
+              echo "SYNTAX $f" >&2
+              status=1
+            fi
+          done
+          exit "$status"
+
+      - name: build.func-Source-Check (jedes ct/*.sh)
+        run: bash tests/check_ct_source.sh
+
+      - name: Validierungs-Unit-Tests (lib/build.func)
+        run: bash tests/test_validation.sh
+
+      - name: shellcheck (falls auf dem Runner installiert)
+        run: |
+          if command -v shellcheck >/dev/null 2>&1; then
+            # -S warning: Style-Hinweise nicht blockierend; externe Sources
+            # (curl|source) kann shellcheck nicht folgen.
+            shellcheck -S warning -e SC1090,SC1091 ct/*.sh install/*.sh tests/*.sh
+          else
+            echo "shellcheck nicht installiert — übersprungen (dokumentiert, K-114)"
+          fi
diff --git a/README.md b/README.md
index 56fda40..e211d77 100644
--- a/README.md
+++ b/README.md
@@ -54,6 +54,12 @@ Shared libs: [`lib/build.func`](lib/build.func) (host-side: prompts, LXC create,
 
 How to add a script: [docs/adding-a-script.md](docs/adding-a-script.md).
 
+## Contributing (verbindlich seit K-114)
+
+**Alle Änderungen laufen als PR mit Cross-Review** — keine Direkt-Commits auf `main`. Hintergrund: Der „`build.func` nicht gesourct"-Bug hat es einmal bis in die Produktion geschafft (authentik-Anlage), während dieselbe Fehlerklasse im nexus-db-PR vom Review gefangen wurde. Die CI (`.gitea/workflows/ci.yml`, Runner-Label `homelab` — instanzweiter Runner aus `ct/runner.sh`) erzwingt zusätzlich: `bash -n` über alle Scripts, „jedes `ct/*.sh` sourct `build.func`" (`tests/check_ct_source.sh`) und die Validierungs-Unit-Tests (`tests/test_validation.sh`).
+
+Eingaben in `prompt_lxc_config` sind validiert (Ziffern-Checks, IP/CIDR/Gateway-Format, Re-Prompt bei unsichtbaren Steuer-/Non-ASCII-Zeichen — Lesson vom 2026-06-11). Neue App-Prompts bitte über `prompt_validated`/`require_valid` aus `lib/build.func` bauen statt nacktem `read`.
+
 ## Repo layout
 
 ```
diff --git a/install/authentik-install.sh b/install/authentik-install.sh
index a77aa33..a02665b 100644
--- a/install/authentik-install.sh
+++ b/install/authentik-install.sh
@@ -29,6 +29,7 @@ CRED_FILE="/root/authentik.credentials"
 
 # ── base packages + Docker ────────────────────────────────────────────────────
 setup_base_apt ca-certificates curl
+configure_ssh_root_login
 if ! command -v docker >/dev/null 2>&1; then
   msg_info "Installing Docker (get.docker.com)..."
   curl -fsSL https://get.docker.com | sh >/dev/null
diff --git a/install/devpi-install.sh b/install/devpi-install.sh
index 2c27f41..382b5ed 100644
--- a/install/devpi-install.sh
+++ b/install/devpi-install.sh
@@ -19,6 +19,7 @@ DEVPI_PORT="3141"
 
 # ── packages + user + dirs ───────────────────────────────────────────────────
 setup_base_apt python3 python3-venv python3-pip
+configure_ssh_root_login
 
 create_system_user "$DEVPI_USER" "$DEVPI_HOME"
 mkdir -p "$DEVPI_DATA"
diff --git a/install/nexus-db-install.sh b/install/nexus-db-install.sh
index 20af92d..9bf3f77 100755
--- a/install/nexus-db-install.sh
+++ b/install/nexus-db-install.sh
@@ -36,6 +36,7 @@ CRED_FILE="/root/nexus-db.credentials"
 
 # ── packages: PGDG repo + PostgreSQL 16 + pgvector ────────────────────────────
 setup_base_apt curl ca-certificates gnupg lsb-release
+configure_ssh_root_login
 
 if [[ ! -f /etc/apt/sources.list.d/pgdg.sources ]] && [[ ! -f /etc/apt/sources.list.d/pgdg.list ]]; then
   msg_info "Adding PGDG apt repo..."
diff --git a/install/nexus-install.sh b/install/nexus-install.sh
index ce83cf1..60da47f 100644
--- a/install/nexus-install.sh
+++ b/install/nexus-install.sh
@@ -46,6 +46,7 @@ run_user() { runuser -u "$APP_USER" -- env HOME="$APP_HOME" "$@"; }
 
 # ── packages: git + rsync + sudo ; Node.js via NodeSource ─────────────────────
 setup_base_apt git rsync sudo
+configure_ssh_root_login
 
 NODE_HAVE="$(command -v node >/dev/null 2>&1 && node -v | sed -E 's/^v([0-9]+).*/\1/' || echo 0)"
 if [[ "$NODE_HAVE" != "$NODE_MAJOR" ]]; then
diff --git a/install/webapp-install.sh b/install/webapp-install.sh
index 9f243d4..45a1eeb 100644
--- a/install/webapp-install.sh
+++ b/install/webapp-install.sh
@@ -44,6 +44,7 @@ run_user() { runuser -u "$APP_USER" -- env HOME="$APP_HOME" "$@"; }
 
 # ── packages: git + rsync + sudo ; Node.js via NodeSource ────────────────────
 setup_base_apt git rsync sudo
+configure_ssh_root_login
 
 NODE_HAVE="$(command -v node >/dev/null 2>&1 && node -v | sed -E 's/^v([0-9]+).*/\1/' || echo 0)"
 if [[ "$NODE_HAVE" != "$NODE_MAJOR" ]]; then
diff --git a/lib/build.func b/lib/build.func
index 880d7ec..4a72257 100644
--- a/lib/build.func
+++ b/lib/build.func
@@ -97,55 +97,204 @@ apply_network_profile() {
   return 0
 }
 
+# ── input validation (K-114) ─────────────────────────────────────────────────
+# Real incident 2026-06-11: a pasted VLAN tag carried an invisible non-UTF-8
+# byte and broke `pct create` deep in the run. Policy: trim CR/edge whitespace,
+# but NEVER silently strip junk inside a value — embedded control/non-ASCII
+# bytes fail validation and trigger a visible re-prompt.
+
+# Trim \r and leading/trailing whitespace (edges only).
+sanitize_input() {
+  local s="${1-}"
+  s="${s//$'\r'/}"
+  s="${s#"${s%%[![:space:]]*}"}"
+  s="${s%"${s##*[![:space:]]}"}"
+  printf '%s' "$s"
+}
+
+# True if the value contains only printable ASCII (no control/non-ASCII
+# bytes). Byte-exact via tr: delete all printable ASCII — anything left
+# over is junk.
+is_clean_ascii() {
+  # Newline/Tab zuerst explizit ablehnen — $(…) strippt trailing newlines,
+  # die der tr-Pfad sonst übersehen würde (Review-Finding K-114).
+  [[ "$1" == *$'\n'* || "$1" == *$'\t'* ]] && return 1
+  local leftover
+  leftover="$(printf '%s' "$1" | LC_ALL=C tr -d '\40-\176')"
+  [[ -z "$leftover" ]]
+}
+
+is_uint()     { is_clean_ascii "$1" && [[ "$1" =~ ^[0-9]+$ ]]; }
+# 10#: führende Nullen nicht als Oktal werten ("08" wäre sonst ein
+# Arithmetik-Fehler statt einer sauberen Ablehnung/Annahme).
+is_vlan_tag() { is_uint "$1" && (( 10#$1 >= 1 && 10#$1 <= 4094 )); }
+is_token()    { is_clean_ascii "$1" && [[ "$1" =~ ^[A-Za-z0-9._-]+$ ]]; }
+is_hostname() { is_clean_ascii "$1" && [[ "$1" =~ ^[A-Za-z0-9]([A-Za-z0-9-]{0,61}[A-Za-z0-9])?$ ]]; }
+
+is_ipv4() {
+  is_clean_ascii "$1" && [[ "$1" =~ ^([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$ ]] || return 1
+  local o
+  for o in "${BASH_REMATCH[@]:1:4}"; do (( 10#$o <= 255 )) || return 1; done
+  return 0
+}
+
+is_cidr() {
+  [[ "$1" =~ ^([0-9.]+)/([0-9]{1,2})$ ]] || return 1
+  # BASH_REMATCH retten — is_ipv4 nutzt selbst =~ und überschreibt es.
+  local _ip="${BASH_REMATCH[1]}" _prefix="${BASH_REMATCH[2]}"
+  is_ipv4 "$_ip" && (( 10#$_prefix >= 1 && 10#$_prefix <= 32 ))
+}
+
+is_ipcfg() { [[ "$1" == "dhcp" ]] || is_cidr "$1"; }
+
+# Ja/Nein-Antworten (Prompts wie "… erlauben? [Y/n]"). Akzeptiert
+# deutsch/englisch, normalize_yesno macht daraus kanonisch yes|no.
+is_yesno() { is_clean_ascii "$1" && [[ "${1,,}" =~ ^(y|yes|j|ja|n|no|nein)$ ]]; }
+normalize_yesno() {
+  case "${1,,}" in
+    y|yes|j|ja) printf 'yes' ;;
+    *)          printf 'no' ;;
+  esac
+}
+
+# Space/comma-separated list of IPv4s (DNS prompt). Gesamtstring zuerst
+# prüfen — die Wort-Splittung würde eingebettete Newlines sonst verstecken.
+is_ipv4_list() {
+  is_clean_ascii "$1" || return 1
+  local item
+  for item in ${1//,/ }; do is_ipv4 "$item" || return 1; done
+  [[ -n "$1" ]]
+}
+
+# prompt_validated VARNAME PROMPT VALIDATOR [DEFAULT] [allow_empty]
+# Reads into VARNAME (nameref, no subshell), sanitizes, applies the default on
+# empty input and re-prompts until the validator passes. allow_empty=yes lets
+# an empty value through (e.g. "no VLAN").
+prompt_validated() {
+  # Schutz vor zirkulärem nameref (Review-Finding): interne Namen tabu.
+  [[ "$1" == _pv_* || "$1" == _rv_* ]] && { msg_err "prompt_validated: reserved variable name '$1'"; return 2; }
+  local -n _pv_ref="$1"
+  local _pv_prompt="$2" _pv_validator="$3" _pv_default="${4-}" _pv_allow_empty="${5:-no}"
+  local _pv_value
+  while true; do
+    if ! read -rp "$_pv_prompt" _pv_value; then
+      # EOF (kein TTY / stdin erschöpft): kein Endlos-Loop, sauber raus —
+      # unter set -e bricht der Caller damit kontrolliert ab.
+      msg_err "No input available for prompt: ${_pv_prompt%% *}"
+      return 1
+    fi
+    _pv_value="$(sanitize_input "$_pv_value")"
+    if [[ -z "$_pv_value" && -n "$_pv_default" ]]; then
+      _pv_value="$_pv_default"
+    fi
+    if [[ -z "$_pv_value" ]]; then
+      if [[ "$_pv_allow_empty" == "yes" ]]; then _pv_ref=""; return 0; fi
+      msg_warn "A value is required."
+      continue
+    fi
+    if "$_pv_validator" "$_pv_value"; then
+      _pv_ref="$_pv_value"
+      return 0
+    fi
+    if ! is_clean_ascii "$_pv_value"; then
+      msg_warn "Input contains invisible/non-ASCII characters — please re-type (do not paste)."
+    else
+      msg_warn "Invalid value: '$_pv_value' — please retry."
+    fi
+  done
+}
+
+# Validate an env-provided value (non-interactive: abort instead of re-prompt).
+require_valid() {
+  [[ "$1" == _pv_* || "$1" == _rv_* ]] && { msg_err "require_valid: reserved variable name '$1'"; return 2; }
+  local -n _rv_ref="$1"
+  local _rv_validator="$2" _rv_label="$3"
+  _rv_ref="$(sanitize_input "$_rv_ref")"
+  "$_rv_validator" "$_rv_ref" || { msg_err "$_rv_label invalid: '$_rv_ref'"; exit 1; }
+}
+
 # ── prompts ──────────────────────────────────────────────────────────────────
-# Each prompt is skipped if the corresponding variable is already set in env.
+# Each prompt is skipped if the corresponding variable is already set in env
+# (env values are still validated — abort on invalid, no silent use).
 # VLAN_TAG and NAMESERVER use ${VAR+x} so that explicitly setting them to ""
 # via env skips the prompt (= "no VLAN" / "inherit DNS from host").
 prompt_lxc_config() {
   if [[ -z "${CTID:-}" ]]; then
-    read -rp "Container ID [auto]: " CTID
-    [[ -z "${CTID:-}" ]] && CTID=$(pvesh get /cluster/nextid)
+    # Eigener Loop statt prompt_validated: leer = auto (pvesh nextid),
+    # ungültig = Re-Prompt (Review-Finding: vorher Abbruch statt Re-Prompt).
+    while true; do
+      if ! read -rp "Container ID [auto]: " CTID; then
+        msg_err "No input available for prompt: Container ID"
+        return 1
+      fi
+      CTID="$(sanitize_input "$CTID")"
+      if [[ -z "$CTID" ]]; then
+        CTID=$(pvesh get /cluster/nextid)
+        break
+      fi
+      is_uint "$CTID" && break
+      msg_warn "Invalid value: '$CTID' — please retry (digits only)."
+    done
+  else
+    require_valid CTID is_uint "Container ID"
   fi
   echo "  → CTID: $CTID"
 
   if [[ -z "${CT_HOSTNAME:-}" ]]; then
-    read -rp "Hostname [$DEFAULT_HOSTNAME]: " CT_HOSTNAME
-    CT_HOSTNAME="${CT_HOSTNAME:-$DEFAULT_HOSTNAME}"
+    prompt_validated CT_HOSTNAME "Hostname [$DEFAULT_HOSTNAME]: " is_hostname "$DEFAULT_HOSTNAME"
+  else
+    require_valid CT_HOSTNAME is_hostname "Hostname"
   fi
   if [[ -z "${DISK_SIZE:-}" ]]; then
-    read -rp "Disk size in GB [$DEFAULT_DISK]: " DISK_SIZE
-    DISK_SIZE="${DISK_SIZE:-$DEFAULT_DISK}"
+    prompt_validated DISK_SIZE "Disk size in GB [$DEFAULT_DISK]: " is_uint "$DEFAULT_DISK"
+  else
+    require_valid DISK_SIZE is_uint "Disk size"
   fi
   if [[ -z "${CORES:-}" ]]; then
-    read -rp "vCPU cores [$DEFAULT_CORES]: " CORES
-    CORES="${CORES:-$DEFAULT_CORES}"
+    prompt_validated CORES "vCPU cores [$DEFAULT_CORES]: " is_uint "$DEFAULT_CORES"
+  else
+    require_valid CORES is_uint "vCPU cores"
   fi
   if [[ -z "${RAM:-}" ]]; then
-    read -rp "RAM in MB [$DEFAULT_RAM]: " RAM
-    RAM="${RAM:-$DEFAULT_RAM}"
+    prompt_validated RAM "RAM in MB [$DEFAULT_RAM]: " is_uint "$DEFAULT_RAM"
+  else
+    require_valid RAM is_uint "RAM"
   fi
   if [[ -z "${BRIDGE:-}" ]]; then
-    read -rp "Bridge [$DEFAULT_BRIDGE]: " BRIDGE
-    BRIDGE="${BRIDGE:-$DEFAULT_BRIDGE}"
+    prompt_validated BRIDGE "Bridge [$DEFAULT_BRIDGE]: " is_token "$DEFAULT_BRIDGE"
+  else
+    require_valid BRIDGE is_token "Bridge"
   fi
   if [[ -z "${VLAN_TAG+x}" ]]; then
-    read -rp "VLAN tag (empty for none): " VLAN_TAG
+    # The 2026-06-11 incident prompt: junk bytes re-prompt, empty = no VLAN.
+    prompt_validated VLAN_TAG "VLAN tag (empty for none): " is_vlan_tag "" yes
+  elif [[ -n "${VLAN_TAG:-}" ]]; then
+    require_valid VLAN_TAG is_vlan_tag "VLAN tag"
   fi
   if [[ -z "${TEMPLATE_STORAGE:-}" ]]; then
-    read -rp "Template storage [$DEFAULT_TEMPLATE_STORAGE]: " TEMPLATE_STORAGE
-    TEMPLATE_STORAGE="${TEMPLATE_STORAGE:-$DEFAULT_TEMPLATE_STORAGE}"
+    prompt_validated TEMPLATE_STORAGE \
+      "Template storage [$DEFAULT_TEMPLATE_STORAGE]: " is_token "$DEFAULT_TEMPLATE_STORAGE"
+  else
+    require_valid TEMPLATE_STORAGE is_token "Template storage"
   fi
   if [[ -z "${ROOTFS_STORAGE:-}" ]]; then
-    read -rp "Rootfs storage [$DEFAULT_ROOTFS_STORAGE]: " ROOTFS_STORAGE
-    ROOTFS_STORAGE="${ROOTFS_STORAGE:-$DEFAULT_ROOTFS_STORAGE}"
+    prompt_validated ROOTFS_STORAGE \
+      "Rootfs storage [$DEFAULT_ROOTFS_STORAGE]: " is_token "$DEFAULT_ROOTFS_STORAGE"
+  else
+    require_valid ROOTFS_STORAGE is_token "Rootfs storage"
   fi
   if [[ -z "${IPCFG:-}" ]]; then
-    read -rp "Network: IP/CIDR or 'dhcp' [dhcp]: " IPCFG
-    IPCFG="${IPCFG:-dhcp}"
+    prompt_validated IPCFG "Network: IP/CIDR or 'dhcp' [dhcp]: " is_ipcfg "dhcp"
+  else
+    require_valid IPCFG is_ipcfg "Network (IP/CIDR or dhcp)"
   fi
   GATEWAY="${GATEWAY:-}"
-  if [[ "$IPCFG" != "dhcp" && -z "$GATEWAY" ]]; then
-    read -rp "Gateway: " GATEWAY
+  if [[ "$IPCFG" != "dhcp" ]]; then
+    if [[ -z "$GATEWAY" ]]; then
+      prompt_validated GATEWAY "Gateway: " is_ipv4
+    else
+      require_valid GATEWAY is_ipv4 "Gateway"
+    fi
   fi
   # DNS is driven by the VLAN tag via the network profile (lib/networks.conf),
   # so the right resolvers get set even with DHCP. Precedence:
@@ -155,17 +304,34 @@ prompt_lxc_config() {
   #   4. DHCP, no profile                                  → inherit from host
   apply_network_profile
   if [[ -n "${NAMESERVER+x}" ]]; then
-    :  # explicit override from env, leave untouched
+    # Explizites Override aus env: "" = inherit bleibt erlaubt, aber ein
+    # gesetzter Wert wird validiert (Review-Finding: lief vorher ungeprüft
+    # bis in pct create).
+    if [[ -n "${NAMESERVER:-}" ]]; then
+      require_valid NAMESERVER is_ipv4_list "DNS server"
+    fi
   elif [[ -n "$PROFILE_DNS" ]]; then
     NAMESERVER="$PROFILE_DNS"
     msg_info "DNS for VLAN ${VLAN_TAG:-none} (${PROFILE_SUBNET:-?}): $NAMESERVER"
   elif [[ "$IPCFG" != "dhcp" ]]; then
     local default_ns="${DEFAULT_NAMESERVER:-$GATEWAY}"
-    read -rp "DNS server [$default_ns] (empty = inherit from PVE host): " NAMESERVER
-    NAMESERVER="${NAMESERVER:-$default_ns}"
+    prompt_validated NAMESERVER \
+      "DNS server [$default_ns] (empty = inherit from PVE host): " \
+      is_ipv4_list "$default_ns" yes
   else
     msg_warn "No network profile for VLAN ${VLAN_TAG:-none}; DHCP DNS will be inherited."
   fi
+
+  # SSH-Root-Login (Default: ja, Homelab-Komfort). Umgesetzt wird das im
+  # Install-Pfad per sshd-Drop-in (configure_ssh_root_login, lib/install.func);
+  # bootstrap_install_script reicht den normalisierten Wert in den Container.
+  if [[ -z "${SSH_ROOT_LOGIN:-}" ]]; then
+    prompt_validated SSH_ROOT_LOGIN "SSH-Root-Login erlauben? [Y/n]: " is_yesno "y"
+  else
+    require_valid SSH_ROOT_LOGIN is_yesno "SSH root login (y/n)"
+  fi
+  SSH_ROOT_LOGIN="$(normalize_yesno "$SSH_ROOT_LOGIN")"
+  echo "  → SSH root login: $SSH_ROOT_LOGIN"
 }
 
 # ── template ─────────────────────────────────────────────────────────────────
@@ -263,7 +429,9 @@ bootstrap_install_script() {
   pct exec "$CTID" -- bash -c "apt-get update -qq && apt-get install -y -qq curl ca-certificates >/dev/null"
 
   msg_info "Running installer ($url)..."
-  pct exec "$CTID" -- bash -c "curl -fsSL '$url' -o /root/${APP}-install.sh && bash /root/${APP}-install.sh"
+  # SSH_ROOT_LOGIN ist durch normalize_yesno kanonisch yes|no — als Env in
+  # den Container durchreichen (configure_ssh_root_login wertet es aus).
+  pct exec "$CTID" -- bash -c "curl -fsSL '$url' -o /root/${APP}-install.sh && SSH_ROOT_LOGIN='${SSH_ROOT_LOGIN:-yes}' bash /root/${APP}-install.sh"
 }
 
 # ── summary ──────────────────────────────────────────────────────────────────
diff --git a/lib/install.func b/lib/install.func
index b4fc48f..2bc3a5c 100644
--- a/lib/install.func
+++ b/lib/install.func
@@ -15,10 +15,14 @@ msg_warn() { echo -e "${YELLOW}[!]${NC} $*"; }
 msg_err()  { echo -e "${RED}[✗]${NC} $*" >&2; }
 
 # ── apt ──────────────────────────────────────────────────────────────────────
-# Always installs: ca-certificates curl openssl tzdata gnupg
+# Always installs: ca-certificates curl openssl tzdata gnupg locales
 # Additional packages can be passed as args.
 setup_base_apt() {
   export DEBIAN_FRONTEND=noninteractive
+  # C.UTF-8 ist in glibc eingebaut und damit schon VOR dem locales-Paket
+  # verfügbar — deckt den ersten apt/dpkg-Lauf ab (keine perl-Warnungen
+  # "Setting locale failed" mehr, LXC-Templates kommen ohne Locale).
+  export LANG=C.UTF-8 LC_ALL=C.UTF-8
   msg_info "Updating apt index..."
   apt-get update -qq
   if [[ $# -gt 0 ]]; then
@@ -27,17 +31,59 @@ setup_base_apt() {
     msg_info "Installing base packages..."
   fi
   apt-get install -y -qq \
-    ca-certificates curl openssl tzdata gnupg \
+    ca-certificates curl openssl tzdata gnupg locales \
     "$@" \
     >/dev/null
+  setup_locales
   msg_ok "apt setup complete"
 }
 
+# en_US.UTF-8 generieren und systemweit als Default setzen; C.UTF-8 braucht
+# keine Generierung (glibc-built-in). Idempotent: sed greift nur auf die
+# auskommentierte Zeile, locale-gen/update-locale sind re-run-sicher.
+setup_locales() {
+  msg_info "Generating locales (en_US.UTF-8; C.UTF-8 built-in)..."
+  sed -i 's/^# *en_US\.UTF-8 UTF-8/en_US.UTF-8 UTF-8/' /etc/locale.gen
+  locale-gen >/dev/null
+  update-locale LANG=en_US.UTF-8
+  msg_ok "Default locale: en_US.UTF-8"
+}
+
 apt_cleanup() {
   apt-get autoremove -y -qq >/dev/null || true
   apt-get autoclean -qq >/dev/null || true
 }
 
+# ── ssh ──────────────────────────────────────────────────────────────────────
+# SSH-Root-Login gemäß Host-Prompt (prompt_lxc_config setzt SSH_ROOT_LOGIN,
+# bootstrap_install_script reicht es als Env durch; Default: yes).
+#   yes → PermitRootLogin yes (Passwort-Login mit dem generierten Root-Passwort)
+#   no  → PermitRootLogin prohibit-password (Debian-Default, nur SSH-Key)
+# Umsetzung als Drop-in, damit Paket-Updates von sshd_config nicht kollidieren.
+configure_ssh_root_login() {
+  local choice="${SSH_ROOT_LOGIN:-yes}" value
+  case "$choice" in
+    yes) value="yes" ;;
+    no)  value="prohibit-password" ;;
+    *)   msg_err "SSH_ROOT_LOGIN must be yes|no, got: '$choice'"; return 1 ;;
+  esac
+
+  if [[ ! -d /etc/ssh/sshd_config.d ]]; then
+    if [[ "$choice" == "no" ]]; then
+      msg_warn "openssh-server not installed — nothing to configure (root login stays off)"
+      return 0
+    fi
+    msg_info "Installing openssh-server..."
+    apt-get install -y -qq openssh-server >/dev/null
+  fi
+
+  msg_info "Configuring SSH root login: PermitRootLogin $value"
+  printf 'PermitRootLogin %s\n' "$value" >/etc/ssh/sshd_config.d/zz-root-login.conf
+  systemctl reload ssh 2>/dev/null || systemctl restart ssh 2>/dev/null \
+    || msg_warn "ssh.service not active yet — config applies on first start"
+  msg_ok "SSH root login: $choice"
+}
+
 # ── users / dirs ─────────────────────────────────────────────────────────────
 create_system_user() {
   local user="$1" home="$2"
diff --git a/tests/check_ct_source.sh b/tests/check_ct_source.sh
new file mode 100755
index 0000000..a0293fe
--- /dev/null
+++ b/tests/check_ct_source.sh
@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+# K-114: Jedes ct/*.sh MUSS lib/build.func sourcen — der Bug "Helfer nicht
+# gesourct, Skript stirbt erst mitten im Lauf" ist zweimal real passiert
+# (nexus-db: im Review gefangen; authentik: erst in Produktion).
+# Aufruf: tests/check_ct_source.sh [verzeichnis]  (Default: ct/)
+#
+# Bewusst eng: akzeptiert wird NUR die curl-Prozesssubstitutions-Form
+# `source <(curl ... build.func)` — das ist der Repo-Vertrag für ct/-Scripts
+# (Review-Triage K-114). Lokales Sourcen gehört nicht in ct/*.sh.
+set -euo pipefail
+
+DIR="${1:-$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)/ct}"
+status=0
+
+shopt -s nullglob
+scripts=("$DIR"/*.sh)
+if [[ ${#scripts[@]} -eq 0 ]]; then
+  echo "no scripts found in $DIR" >&2
+  exit 1
+fi
+
+for script in "${scripts[@]}"; do
+  if grep -Eq 'source[[:space:]]+<\(curl[^)]*build\.func' "$script"; then
+    echo "ok     $script"
+  else
+    echo "FEHLT  $script — sourct lib/build.func nicht" >&2
+    status=1
+  fi
+done
+exit "$status"
diff --git a/tests/test_validation.sh b/tests/test_validation.sh
new file mode 100755
index 0000000..0a0ca90
--- /dev/null
+++ b/tests/test_validation.sh
@@ -0,0 +1,200 @@
+#!/usr/bin/env bash
+# K-114: Unit-Tests für die Input-Validierung in lib/build.func.
+# Läuft ohne PVE (sourct nur die Helfer). Aufruf: bash tests/test_validation.sh
+set -u
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+# shellcheck source=/dev/null
+source "$REPO_ROOT/lib/build.func"
+
+PASS=0
+FAIL=0
+
+ok() { PASS=$((PASS + 1)); echo "ok     - $1"; }
+nok() { FAIL=$((FAIL + 1)); echo "NOT OK - $1"; }
+
+assert_true() {  # assert_true "desc" cmd args...
+  local desc="$1"; shift
+  if "$@"; then ok "$desc"; else nok "$desc"; fi
+}
+assert_false() {
+  local desc="$1"; shift
+  if "$@"; then nok "$desc"; else ok "$desc"; fi
+}
+
+# ── Repro des Vorfalls vom 2026-06-11: VLAN-Tag mit unsichtbarem Byte ────────
+JUNK_VLAN="$(printf '2\x800')"   # "20" mit eingebettetem Non-UTF-8-Byte
+assert_false "VLAN-Repro: '2<0x80>0' wird abgelehnt (kein silent strip)" is_vlan_tag "$JUNK_VLAN"
+assert_false "is_clean_ascii erkennt eingebettetes Junk-Byte" is_clean_ascii "$JUNK_VLAN"
+
+# Re-Prompt-Verhalten: erste Eingabe ist der Junk-Wert, zweite ist sauber —
+# prompt_validated muss die zweite liefern (AC: Re-Prompt statt pct-Fehler).
+reprompt_result="$(
+  printf '%s\n20\n' "$JUNK_VLAN" | {
+    VLAN=""
+    prompt_validated VLAN "VLAN tag (empty for none): " is_vlan_tag "" yes >/dev/null 2>&1
+    printf '%s' "$VLAN"
+  }
+)"
+if [[ "$reprompt_result" == "20" ]]; then
+  ok "prompt_validated re-promptet bei Junk und akzeptiert dann '20'"
+else
+  nok "prompt_validated re-promptet bei Junk (got: '$reprompt_result')"
+fi
+
+# ── sanitize_input: CR + Rand-Whitespace weg, Inhalt unangetastet ─────────────
+[[ "$(sanitize_input $'  42\r\n')" == "42" ]] && ok "sanitize_input trimmt CR/Whitespace" \
+  || nok "sanitize_input trimmt CR/Whitespace"
+[[ "$(sanitize_input "$JUNK_VLAN")" == "$JUNK_VLAN" ]] && ok "sanitize_input strippt KEIN eingebettetes Junk (Validator soll es sehen)" \
+  || nok "sanitize_input lässt eingebettetes Junk unangetastet"
+
+# ── numerische Validatoren ────────────────────────────────────────────────────
+assert_true  "is_uint akzeptiert 8"            is_uint "8"
+assert_false "is_uint lehnt '8 ' mit Junk ab"  is_uint "$(printf '8\x01')"
+assert_false "is_uint lehnt 'abc' ab"          is_uint "abc"
+assert_false "is_uint lehnt leeren Wert ab"    is_uint ""
+assert_true  "is_vlan_tag akzeptiert 20"       is_vlan_tag "20"
+assert_false "is_vlan_tag lehnt 0 ab"          is_vlan_tag "0"
+assert_false "is_vlan_tag lehnt 5000 ab"       is_vlan_tag "5000"
+
+# ── Netz-Validatoren ──────────────────────────────────────────────────────────
+assert_true  "is_ipv4 akzeptiert 10.11.20.66"      is_ipv4 "10.11.20.66"
+assert_false "is_ipv4 lehnt 10.11.20.666 ab"       is_ipv4 "10.11.20.666"
+assert_false "is_ipv4 lehnt 10.11.20 ab"           is_ipv4 "10.11.20"
+assert_true  "is_cidr akzeptiert 10.11.20.5/24"    is_cidr "10.11.20.5/24"
+assert_false "is_cidr lehnt 10.11.20.5/33 ab"      is_cidr "10.11.20.5/33"
+assert_false "is_cidr lehnt 10.11.20.5 ohne Maske" is_cidr "10.11.20.5"
+assert_true  "is_ipcfg akzeptiert dhcp"            is_ipcfg "dhcp"
+assert_true  "is_ipcfg akzeptiert CIDR"            is_ipcfg "192.168.0.7/24"
+assert_false "is_ipcfg lehnt 'static' ab"          is_ipcfg "static"
+assert_true  "is_ipv4_list akzeptiert Liste"       is_ipv4_list "1.1.1.1, 8.8.8.8"
+assert_false "is_ipv4_list lehnt Hostnamen ab"     is_ipv4_list "dns.local"
+
+# ── Namen/Token ───────────────────────────────────────────────────────────────
+assert_true  "is_hostname akzeptiert nexus-db"     is_hostname "nexus-db"
+assert_false "is_hostname lehnt '-bad' ab"         is_hostname "-bad"
+assert_false "is_hostname lehnt 'a b' ab"          is_hostname "a b"
+assert_true  "is_token akzeptiert local-lvm"       is_token "local-lvm"
+assert_false "is_token lehnt 'a;b' ab"             is_token "a;b"
+
+# ── Ja/Nein (SSH-Root-Login-Prompt) ──────────────────────────────────────────
+assert_true  "is_yesno akzeptiert y"               is_yesno "y"
+assert_true  "is_yesno akzeptiert Ja"              is_yesno "Ja"
+assert_true  "is_yesno akzeptiert NO"              is_yesno "NO"
+assert_true  "is_yesno akzeptiert nein"            is_yesno "nein"
+assert_false "is_yesno lehnt 'maybe' ab"           is_yesno "maybe"
+assert_false "is_yesno lehnt leeren Wert ab"       is_yesno ""
+[[ "$(normalize_yesno "J")" == "yes" && "$(normalize_yesno "nein")" == "no" ]] \
+  && ok "normalize_yesno kanonisiert J→yes, nein→no" \
+  || nok "normalize_yesno kanonisiert J→yes, nein→no"
+
+# SSH-Root-Login-Prompt: leere Eingabe = Default Y → normalisiert yes;
+# explizites 'n' → no.
+ssh_default="$(
+  printf '\n' | {
+    SSH_ROOT_LOGIN=""
+    prompt_validated SSH_ROOT_LOGIN "SSH-Root-Login erlauben? [Y/n]: " is_yesno "y" >/dev/null 2>&1
+    normalize_yesno "$SSH_ROOT_LOGIN"
+  }
+)"
+[[ "$ssh_default" == "yes" ]] && ok "SSH-Root-Login: leere Eingabe → Default yes" \
+  || nok "SSH-Root-Login Default (got: '$ssh_default')"
+ssh_no="$(
+  printf 'n\n' | {
+    SSH_ROOT_LOGIN=""
+    prompt_validated SSH_ROOT_LOGIN "SSH-Root-Login erlauben? [Y/n]: " is_yesno "y" >/dev/null 2>&1
+    normalize_yesno "$SSH_ROOT_LOGIN"
+  }
+)"
+[[ "$ssh_no" == "no" ]] && ok "SSH-Root-Login: 'n' → no" \
+  || nok "SSH-Root-Login 'n' (got: '$ssh_no')"
+
+# ── require_valid: env-Werte werden sanitisiert + geprüft ────────────────────
+CHECKVAL=$'  7\r'
+require_valid CHECKVAL is_uint "Testwert" && [[ "$CHECKVAL" == "7" ]] \
+  && ok "require_valid sanitisiert env-Wert (CR weg)" \
+  || nok "require_valid sanitisiert env-Wert"
+( CHECKBAD="$JUNK_VLAN"; require_valid CHECKBAD is_uint "Testwert" ) >/dev/null 2>&1 \
+  && nok "require_valid bricht bei Junk-env-Wert ab" \
+  || ok "require_valid bricht bei Junk-env-Wert ab (exit != 0)"
+
+# ── Negativ-Beweis: build.func-Source-Check schlägt bei Präparat an ──────────
+TMPDIR_CT="$(mktemp -d)"
+cat >"$TMPDIR_CT/broken.sh" <<'EOF'
+#!/usr/bin/env bash
+# absichtlich ohne source build.func (Repro des zweimal aufgetretenen Bugs)
+APP="broken"
+prompt_lxc_config
+EOF
+if bash "$REPO_ROOT/tests/check_ct_source.sh" "$TMPDIR_CT" >/dev/null 2>&1; then
+  nok "check_ct_source.sh erkennt fehlendes 'source build.func'"
+else
+  ok "check_ct_source.sh erkennt fehlendes 'source build.func'"
+fi
+rm -rf "$TMPDIR_CT"
+
+# Positiv: das echte ct/-Verzeichnis ist sauber.
+if bash "$REPO_ROOT/tests/check_ct_source.sh" "$REPO_ROOT/ct" >/dev/null 2>&1; then
+  ok "alle ct/*.sh sourcen build.func"
+else
+  nok "alle ct/*.sh sourcen build.func"
+fi
+
+# ── Review-Findings K-114: Oktal, Newline, EOF, Nameref-Guard ────────────────
+assert_true  "is_vlan_tag akzeptiert '08' (kein Oktal-Fehler)"  is_vlan_tag "08"
+assert_true  "is_cidr akzeptiert /08 (kein Oktal-Fehler)"       is_cidr "10.0.0.1/08"
+assert_false "is_clean_ascii lehnt eingebettetes Newline ab"    is_clean_ascii $'1.1.1.1\n8.8.8.8'
+assert_false "is_ipv4_list lehnt Newline-Liste ab"              is_ipv4_list $'1.1.1.1\n8.8.8.8'
+
+# EOF statt Eingabe: prompt_validated darf nicht endlos loopen.
+( printf '' | { V=""; prompt_validated V "Wert: " is_uint; } ) >/dev/null 2>&1
+rc=$?
+[[ "$rc" -ne 0 ]] && ok "prompt_validated bricht bei EOF ab (rc=$rc)" \
+  || nok "prompt_validated bricht bei EOF ab"
+
+# Reservierte Namen → Guard statt zirkulärem nameref.
+( _pv_ref=""; prompt_validated _pv_ref "x: " is_uint ) >/dev/null 2>&1
+[[ $? -eq 2 ]] && ok "prompt_validated weist reservierte Variablennamen ab" \
+  || nok "prompt_validated weist reservierte Variablennamen ab"
+
+# CTID-Re-Prompt: ungültig → erneut fragen, leer wäre auto (hier: gültige Zahl).
+ctid_out="$(
+  printf 'abc\n123\n' | env -u CTID bash -c "
+    source '$REPO_ROOT/lib/build.func'
+    CTID=''
+    while true; do
+      read -rp 'Container ID [auto]: ' CTID || exit 1
+      CTID=\"\$(sanitize_input \"\$CTID\")\"
+      [[ -z \"\$CTID\" ]] && exit 1
+      is_uint \"\$CTID\" && break
+    done
+    printf '%s' \"\$CTID\""
+)"
+[[ "$ctid_out" == "123" ]] && ok "CTID-Loop re-promptet bei 'abc' und nimmt '123'" \
+  || nok "CTID-Loop re-promptet (got: '$ctid_out')"
+
+# ── Dry-Run: prompt_lxc_config komplett aus env, ohne PVE/TTY ────────────────
+smoke_out="$(
+  env CTID=999 CT_HOSTNAME=smoke DISK_SIZE=8 CORES=2 RAM=1024 BRIDGE=vmbr0 \
+    VLAN_TAG=20 TEMPLATE_STORAGE=local ROOTFS_STORAGE=local-lvm \
+    IPCFG=10.11.20.99/24 GATEWAY=10.11.20.1 NAMESERVER="" SSH_ROOT_LOGIN=J \
+    NET_PROFILES_FILE="$REPO_ROOT/lib/networks.conf" \
+    bash -c "source '$REPO_ROOT/lib/build.func' && prompt_lxc_config >/dev/null && echo SMOKE-OK:\$SSH_ROOT_LOGIN"
+)" || true
+[[ "$smoke_out" == *SMOKE-OK:yes* ]] \
+  && ok "prompt_lxc_config Dry-Run mit validen env-Werten läuft durch (SSH_ROOT_LOGIN J→yes)" \
+  || nok "prompt_lxc_config Dry-Run (got: '$smoke_out')"
+
+smoke_bad="$(
+  env CTID="$(printf '9\x809')" CT_HOSTNAME=smoke DISK_SIZE=8 CORES=2 RAM=1024 BRIDGE=vmbr0 \
+    VLAN_TAG=20 TEMPLATE_STORAGE=local ROOTFS_STORAGE=local-lvm IPCFG=dhcp NAMESERVER="" \
+    NET_PROFILES_FILE="$REPO_ROOT/lib/networks.conf" \
+    bash -c "source '$REPO_ROOT/lib/build.func' && prompt_lxc_config >/dev/null && echo SMOKE-OK" 2>/dev/null
+)" || true
+[[ "$smoke_bad" == *SMOKE-OK* ]] \
+  && nok "prompt_lxc_config bricht bei Junk-CTID aus env ab" \
+  || ok "prompt_lxc_config bricht bei Junk-CTID aus env ab"
+
+echo
+echo "passed=$PASS failed=$FAIL"
+[[ "$FAIL" -eq 0 ]]