diff --git a/test/acceptance.d/security-test.sh b/test/acceptance.d/security-test.sh
new file mode 100755
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--- /dev/null
+++ b/test/acceptance.d/security-test.sh
@@ -0,0 +1,105 @@
+#!/bin/bash
+#
+# Verifies the security posture of an installed system: the unprivileged
+# session-to-root paths closed for 4.0.2 (blanket input-group grant, shipped
+# asdcontrol sudoers authorization) and the SSH hardening flow.
+#
+# The sshd section reconfigures the machine (enables sshd, opens the firewall,
+# disables password logins), so it demands explicit opt-in: it only runs when
+# OMARCHY_ACCEPTANCE_SUDO_PASSWORD is set, which omarchy-iso-test does for its
+# throwaway VMs. A cached sudo timestamp alone never triggers it, so running
+# the suite on a machine you care about cannot reconfigure sshd by accident.
+
+set -euo pipefail
+
+source "$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)/base-test.sh"
+
+# Membership of `input` gives raw access to /dev/input/event*: any process
+# running as the user could log keystrokes. Only the opt-in controller and
+# ydotool features may grant it.
+verify_input_group() {
+  if id -nG | grep -qw input; then
+    if pacman -Q xpadneo-dkms &>/dev/null || pacman -Q ydotool &>/dev/null; then
+      pass "input group membership is backed by an opt-in feature"
+    else
+      fail "user is not in the input group" "no controller or ydotool support installed to justify it"
+    fi
+  else
+    pass "user is not in the input group"
+  fi
+}
+
+sudo_available() {
+  if sudo -n true 2>/dev/null; then
+    return 0
+  fi
+
+  if [[ -n ${OMARCHY_ACCEPTANCE_SUDO_PASSWORD:-} ]]; then
+    printf '%s\n' "$OMARCHY_ACCEPTANCE_SUDO_PASSWORD" | sudo -S -v 2>/dev/null
+    return $?
+  fi
+
+  return 1
+}
+
+verify_asdcontrol_sudoers() {
+  # Omarchy used to ship a passwordless sudoers grant for asdcontrol; that
+  # authorization now belongs to the package alone.
+  if sudo -n test -e /etc/sudoers.d/omarchy-asdcontrol; then
+    fail "no omarchy asdcontrol sudoers grant is shipped" "/etc/sudoers.d/omarchy-asdcontrol exists"
+  fi
+  pass "no omarchy asdcontrol sudoers grant is shipped"
+}
+
+verify_sshd_hardening() {
+  local key_file=/tmp/omarchy-acceptance-sshd-key
+  local effective_config
+
+  rm -f "$key_file" "$key_file.pub"
+  ssh-keygen -t ed25519 -N "" -q -C "omarchy-acceptance" -f "$key_file"
+
+  if ! omarchy-setup-security-sshd --key="$(cat "$key_file.pub")" >"$ARTIFACTS/setup-security-sshd.log" 2>&1; then
+    fail "omarchy-setup-security-sshd completes unattended" "$(tail -5 "$ARTIFACTS/setup-security-sshd.log")"
+  fi
+  pass "omarchy-setup-security-sshd completes unattended"
+
+  systemctl is-active sshd.service >/dev/null || fail "sshd is running after setup"
+  pass "sshd is running after setup"
+
+  grep -qxF "$(cat "$key_file.pub")" "$HOME/.ssh/authorized_keys" || fail "the key is authorized"
+  pass "the key is authorized"
+
+  # The command verifies its own hardening before keeping it, but assert the
+  # effective config independently: sshd honors the first value it reads, and
+  # regressions here reopen password logins. Keywords match case-insensitively
+  # because OpenSSH 9.x dumps them lowercase and 10.x in CamelCase.
+  effective_config=$(sudo -n sshd -T) || fail "sshd reports its effective config"
+  grep -qixF "passwordauthentication no" <<<"$effective_config" || fail "password authentication is off"
+  pass "password authentication is off"
+  grep -qixF "kbdinteractiveauthentication no" <<<"$effective_config" || fail "keyboard-interactive authentication is off"
+  pass "keyboard-interactive authentication is off"
+
+  if omarchy-cmd-present ufw; then
+    sudo -n ufw status | grep -qE '^22/tcp\s+LIMIT' || fail "the SSH port is rate limited in the firewall"
+    pass "the SSH port is rate limited in the firewall"
+  fi
+
+  # Leave the machine as found where cheap: the throwaway key stays useless
+  # once removed, while the hardening itself is the state under test.
+  sed -i "\#$(cat "$key_file.pub" | cut -d' ' -f2)#d" "$HOME/.ssh/authorized_keys"
+  rm -f "$key_file" "$key_file.pub"
+}
+
+verify_input_group
+
+if sudo_available; then
+  verify_asdcontrol_sudoers
+else
+  pass "asdcontrol sudoers check skipped: sudo needs a password"
+fi
+
+if [[ -n ${OMARCHY_ACCEPTANCE_SUDO_PASSWORD:-} ]] && sudo_available; then
+  verify_sshd_hardening
+else
+  pass "sshd hardening exercise skipped: set OMARCHY_ACCEPTANCE_SUDO_PASSWORD to run it"
+fi