diff --git a/services/maintenance/kustomization.yaml b/services/maintenance/kustomization.yaml
index 5ff09a17..f99efd65 100644
--- a/services/maintenance/kustomization.yaml
+++ b/services/maintenance/kustomization.yaml
@@ -3,6 +3,7 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - namespace.yaml
+  - pi-usb-scratch-configmap.yaml
   - image.yaml
   - secretproviderclass.yaml
   - metis-configmap.yaml
@@ -21,7 +22,9 @@ resources:
   - metis-rbac.yaml
   - metis-token-sync-serviceaccount.yaml
   - node-nofile-serviceaccount.yaml
+  - pi-usb-scratch-serviceaccount.yaml
   - pod-cleaner-rbac.yaml
+  - pi-usb-scratch-rbac.yaml
   - ariadne-deployment.yaml
   - metis-deployment.yaml
   - soteria-deployment.yaml
@@ -31,6 +34,7 @@ resources:
   - disable-k3s-traefik-daemonset.yaml
   - oneoffs/k3s-traefik-cleanup-job.yaml
   - node-nofile-daemonset.yaml
+  - pi-usb-scratch-daemonset.yaml
   - metis-sentinel-amd64-daemonset.yaml
   - metis-sentinel-arm64-daemonset.yaml
   - k3s-agent-restart-daemonset.yaml
@@ -72,3 +76,9 @@ configMapGenerator:
       - node_image_sweeper.sh=scripts/node_image_sweeper.sh
     options:
       disableNameSuffixHash: true
+  - name: pi-usb-scratch-script
+    namespace: maintenance
+    files:
+      - pi_usb_scratch.sh=scripts/pi_usb_scratch.sh
+    options:
+      disableNameSuffixHash: true
diff --git a/services/maintenance/pi-usb-scratch-configmap.yaml b/services/maintenance/pi-usb-scratch-configmap.yaml
new file mode 100644
index 00000000..18fc6712
--- /dev/null
+++ b/services/maintenance/pi-usb-scratch-configmap.yaml
@@ -0,0 +1,35 @@
+# services/maintenance/pi-usb-scratch-configmap.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: pi-usb-scratch-config
+  namespace: maintenance
+data:
+  usb_scratch.env: |
+    USB_SCRATCH_DEFAULT_ENABLED=true
+    USB_SCRATCH_DEFAULT_LABEL=atlas-scratch
+    USB_SCRATCH_DEFAULT_FSTYPE=ext4
+    USB_SCRATCH_MOUNTPOINT=/mnt/usb-scratch
+    USB_SCRATCH_REQUIRED_FREE_GIB=20
+    USB_SCRATCH_RECONCILE_INTERVAL_SEC=900
+    USB_SCRATCH_CUTOVER_JITTER_MAX_SEC=900
+  usb_scratch_inventory.tsv: |
+    # node_name enabled match_kind match_value fstype
+    # match_kind: uuid | label | device
+    # Prefer UUID entries for the first rollout. A shared label works too if every Pi USB stick is formatted consistently.
+    # Example:
+    # titan-04 true uuid 11111111-2222-3333-4444-555555555555 ext4
+    # titan-05 true label atlas-scratch ext4
+    # titan-06 true label atlas-scratch ext4
+    # titan-07 true label atlas-scratch ext4
+    # titan-08 true label atlas-scratch ext4
+    # titan-09 true label atlas-scratch ext4
+    # titan-10 true label atlas-scratch ext4
+    # titan-11 true label atlas-scratch ext4
+    # titan-12 true label atlas-scratch ext4
+    # titan-13 true label atlas-scratch ext4
+    # titan-14 true label atlas-scratch ext4
+    # titan-15 true label atlas-scratch ext4
+    # titan-17 true label atlas-scratch ext4
+    # titan-18 true label atlas-scratch ext4
+    # titan-19 true label atlas-scratch ext4
diff --git a/services/maintenance/pi-usb-scratch-daemonset.yaml b/services/maintenance/pi-usb-scratch-daemonset.yaml
new file mode 100644
index 00000000..26fa7cf1
--- /dev/null
+++ b/services/maintenance/pi-usb-scratch-daemonset.yaml
@@ -0,0 +1,68 @@
+# services/maintenance/pi-usb-scratch-daemonset.yaml
+apiVersion: apps/v1
+kind: DaemonSet
+metadata:
+  name: pi-usb-scratch
+  namespace: maintenance
+spec:
+  selector:
+    matchLabels:
+      app: pi-usb-scratch
+  updateStrategy:
+    type: RollingUpdate
+    rollingUpdate:
+      maxUnavailable: 1
+  template:
+    metadata:
+      labels:
+        app: pi-usb-scratch
+    spec:
+      serviceAccountName: pi-usb-scratch
+      hostPID: true
+      nodeSelector:
+        kubernetes.io/arch: arm64
+        node-role.kubernetes.io/worker: "true"
+      affinity:
+        nodeAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+            nodeSelectorTerms:
+              - matchExpressions:
+                  - key: hardware
+                    operator: In
+                    values:
+                      - rpi4
+                      - rpi5
+      containers:
+        - name: pi-usb-scratch
+          image: bitnami/kubectl@sha256:554ab88b1858e8424c55de37ad417b16f2a0e65d1607aa0f3fe3ce9b9f10b131
+          command: ["/usr/bin/env", "bash"]
+          args: ["/scripts/pi_usb_scratch.sh"]
+          env:
+            - name: NODE_NAME
+              valueFrom:
+                fieldRef:
+                  fieldPath: spec.nodeName
+          securityContext:
+            privileged: true
+            runAsUser: 0
+          volumeMounts:
+            - name: host-root
+              mountPath: /host
+            - name: script
+              mountPath: /scripts
+              readOnly: true
+            - name: config
+              mountPath: /config
+              readOnly: true
+      volumes:
+        - name: host-root
+          hostPath:
+            path: /
+        - name: script
+          configMap:
+            name: pi-usb-scratch-script
+            defaultMode: 0555
+        - name: config
+          configMap:
+            name: pi-usb-scratch-config
+            defaultMode: 0444
diff --git a/services/maintenance/pi-usb-scratch-rbac.yaml b/services/maintenance/pi-usb-scratch-rbac.yaml
new file mode 100644
index 00000000..97b9cd9a
--- /dev/null
+++ b/services/maintenance/pi-usb-scratch-rbac.yaml
@@ -0,0 +1,26 @@
+# services/maintenance/pi-usb-scratch-rbac.yaml
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: pi-usb-scratch
+rules:
+  - apiGroups: [""]
+    resources:
+      - nodes
+    verbs:
+      - get
+      - list
+      - patch
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: pi-usb-scratch
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: pi-usb-scratch
+subjects:
+  - kind: ServiceAccount
+    name: pi-usb-scratch
+    namespace: maintenance
diff --git a/services/maintenance/pi-usb-scratch-serviceaccount.yaml b/services/maintenance/pi-usb-scratch-serviceaccount.yaml
new file mode 100644
index 00000000..7ac84fb4
--- /dev/null
+++ b/services/maintenance/pi-usb-scratch-serviceaccount.yaml
@@ -0,0 +1,6 @@
+# services/maintenance/pi-usb-scratch-serviceaccount.yaml
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: pi-usb-scratch
+  namespace: maintenance
diff --git a/services/maintenance/scripts/pi_usb_scratch.sh b/services/maintenance/scripts/pi_usb_scratch.sh
new file mode 100755
index 00000000..fad30339
--- /dev/null
+++ b/services/maintenance/scripts/pi_usb_scratch.sh
@@ -0,0 +1,409 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+NODE_NAME=${NODE_NAME:?NODE_NAME is required}
+HOST_ROOT=${HOST_ROOT:-/host}
+CONFIG_ENV=${CONFIG_ENV:-/config/usb_scratch.env}
+INVENTORY_FILE=${INVENTORY_FILE:-/config/usb_scratch_inventory.tsv}
+FSTAB_PATH="${HOST_ROOT}/etc/fstab"
+STATE_DIR="${HOST_ROOT}/var/lib/maintenance/pi-usb-scratch"
+MANAGED_BEGIN="# BEGIN maintenance.bstein.dev usb-scratch"
+MANAGED_END="# END maintenance.bstein.dev usb-scratch"
+ONE_SHOT=${ONE_SHOT:-false}
+DEFAULT_PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
+
+USB_SCRATCH_DEFAULT_ENABLED=${USB_SCRATCH_DEFAULT_ENABLED:-true}
+USB_SCRATCH_DEFAULT_LABEL=${USB_SCRATCH_DEFAULT_LABEL:-atlas-scratch}
+USB_SCRATCH_DEFAULT_FSTYPE=${USB_SCRATCH_DEFAULT_FSTYPE:-ext4}
+USB_SCRATCH_MOUNTPOINT=${USB_SCRATCH_MOUNTPOINT:-/mnt/usb-scratch}
+USB_SCRATCH_REQUIRED_FREE_GIB=${USB_SCRATCH_REQUIRED_FREE_GIB:-20}
+USB_SCRATCH_RECONCILE_INTERVAL_SEC=${USB_SCRATCH_RECONCILE_INTERVAL_SEC:-900}
+USB_SCRATCH_CUTOVER_JITTER_MAX_SEC=${USB_SCRATCH_CUTOVER_JITTER_MAX_SEC:-900}
+
+TARGET_PATHS=(
+  "/var/log/pods"
+  "/var/log/containers"
+  "/var/lib/rancher/k3s/agent/containerd"
+  "/var/lib/rancher/k3s/agent/images"
+)
+
+agent_stopped=0
+
+log() {
+  printf '[%s] %s\n' "$(date -u +%FT%TZ)" "$*"
+}
+
+sanitize_annotation_value() {
+  printf '%s' "$1" | tr ' ' '_' | tr -cd '[:alnum:]._:/=-'
+}
+
+annotate_node() {
+  local status="$1"
+  local detail="$2"
+  local selector="$3"
+  local timestamp
+  timestamp="$(date -u +%FT%TZ)"
+  kubectl annotate --overwrite node "${NODE_NAME}" \
+    maintenance.bstein.dev/usb-scratch-status="$(sanitize_annotation_value "${status}")" \
+    maintenance.bstein.dev/usb-scratch-detail="$(sanitize_annotation_value "${detail}")" \
+    maintenance.bstein.dev/usb-scratch-selector="$(sanitize_annotation_value "${selector}")" \
+    maintenance.bstein.dev/usb-scratch-mountpoint="$(sanitize_annotation_value "${USB_SCRATCH_MOUNTPOINT}")" \
+    maintenance.bstein.dev/usb-scratch-managed-paths="$(sanitize_annotation_value "${TARGET_PATHS[*]}")" \
+    maintenance.bstein.dev/usb-scratch-last-apply="${timestamp}" \
+    >/dev/null 2>&1 || true
+}
+
+host_sh() {
+  local command="$1"
+  if command -v nsenter >/dev/null 2>&1; then
+    nsenter -t 1 -m -u -i -n -p -- /bin/sh -ceu "PATH=${DEFAULT_PATH}; ${command}"
+  elif [ -x "${HOST_ROOT}/usr/bin/nsenter" ]; then
+    "${HOST_ROOT}/usr/bin/nsenter" -t 1 -m -u -i -n -p -- /bin/sh -ceu "PATH=${DEFAULT_PATH}; ${command}"
+  elif [ -x "${HOST_ROOT}/bin/nsenter" ]; then
+    "${HOST_ROOT}/bin/nsenter" -t 1 -m -u -i -n -p -- /bin/sh -ceu "PATH=${DEFAULT_PATH}; ${command}"
+  else
+    chroot "${HOST_ROOT}" /bin/sh -ceu "PATH=${DEFAULT_PATH}; ${command}"
+  fi
+}
+
+cleanup() {
+  if [ "${agent_stopped}" -eq 1 ]; then
+    log "starting k3s-agent after interrupted cutover"
+    host_sh "systemctl start k3s-agent || true"
+    agent_stopped=0
+  fi
+}
+trap cleanup EXIT
+
+load_config() {
+  if [ -f "${CONFIG_ENV}" ]; then
+    # shellcheck disable=SC1090
+    . "${CONFIG_ENV}"
+  fi
+
+  USB_SCRATCH_DEFAULT_ENABLED=${USB_SCRATCH_DEFAULT_ENABLED:-true}
+  USB_SCRATCH_DEFAULT_LABEL=${USB_SCRATCH_DEFAULT_LABEL:-atlas-scratch}
+  USB_SCRATCH_DEFAULT_FSTYPE=${USB_SCRATCH_DEFAULT_FSTYPE:-ext4}
+  USB_SCRATCH_MOUNTPOINT=${USB_SCRATCH_MOUNTPOINT:-/mnt/usb-scratch}
+  USB_SCRATCH_REQUIRED_FREE_GIB=${USB_SCRATCH_REQUIRED_FREE_GIB:-20}
+  USB_SCRATCH_RECONCILE_INTERVAL_SEC=${USB_SCRATCH_RECONCILE_INTERVAL_SEC:-900}
+  USB_SCRATCH_CUTOVER_JITTER_MAX_SEC=${USB_SCRATCH_CUTOVER_JITTER_MAX_SEC:-900}
+}
+
+lookup_inventory() {
+  local line=""
+  if [ -f "${INVENTORY_FILE}" ]; then
+    line="$(awk -v node="${NODE_NAME}" 'NF >= 4 && $1 !~ /^#/ && $1 == node { print; exit }' "${INVENTORY_FILE}" || true)"
+  fi
+  printf '%s' "${line}"
+}
+
+strip_managed_block() {
+  local source_file="$1"
+  awk -v begin="${MANAGED_BEGIN}" -v end="${MANAGED_END}" '
+    $0 == begin { skip=1; next }
+    $0 == end { skip=0; next }
+    skip != 1 { print }
+  ' "${source_file}"
+}
+
+ensure_fstab_block() {
+  local selector="$1"
+  local fstype="$2"
+  local tmp_base tmp_candidate bind_source target
+
+  mkdir -p "${STATE_DIR}"
+  tmp_base="${STATE_DIR}/fstab.base"
+  tmp_candidate="${STATE_DIR}/fstab.candidate"
+
+  strip_managed_block "${FSTAB_PATH}" > "${tmp_base}"
+  cp "${tmp_base}" "${tmp_candidate}"
+
+  {
+    printf '%s\n' "${MANAGED_BEGIN}"
+    printf '%s %s %s defaults,nofail,noatime,lazytime,commit=60,x-systemd.device-timeout=15s,x-systemd.mount-timeout=30s 0 2\n' \
+      "${selector}" "${USB_SCRATCH_MOUNTPOINT}" "${fstype}"
+    for target in "${TARGET_PATHS[@]}"; do
+      bind_source="${USB_SCRATCH_MOUNTPOINT}${target}"
+      printf '%s %s none bind,nofail,x-systemd.requires-mounts-for=%s 0 0\n' \
+        "${bind_source}" "${target}" "${USB_SCRATCH_MOUNTPOINT}"
+    done
+    printf '%s\n' "${MANAGED_END}"
+  } >> "${tmp_candidate}"
+
+  if ! cmp -s "${FSTAB_PATH}" "${tmp_candidate}"; then
+    cp "${tmp_candidate}" "${FSTAB_PATH}"
+    log "updated ${FSTAB_PATH} managed block"
+    return 0
+  fi
+
+  return 1
+}
+
+find_existing_mount_source() {
+  local target="$1"
+  host_sh "findmnt -T '${target}' -n -o SOURCE 2>/dev/null || true"
+}
+
+resolve_selector() {
+  local inventory_line enabled kind value fstype actual_device actual_fstype actual_uuid actual_label selector expected_fstype
+  inventory_line="$(lookup_inventory)"
+  enabled="${USB_SCRATCH_DEFAULT_ENABLED}"
+  kind=""
+  value=""
+  fstype="${USB_SCRATCH_DEFAULT_FSTYPE}"
+
+  if [ -n "${inventory_line}" ]; then
+    read -r _ enabled kind value fstype _ <<<"${inventory_line}"
+  elif [ -n "${USB_SCRATCH_DEFAULT_LABEL}" ]; then
+    kind="label"
+    value="${USB_SCRATCH_DEFAULT_LABEL}"
+  fi
+
+  if [ "${enabled}" != "true" ]; then
+    SELECTOR_KIND="disabled"
+    SELECTOR_VALUE=""
+    SELECTOR_SPEC=""
+    DEVICE_PATH=""
+    DEVICE_FSTYPE="${fstype}"
+    return 0
+  fi
+
+  if [ -z "${kind}" ] || [ -z "${value}" ]; then
+    SELECTOR_KIND="missing"
+    SELECTOR_VALUE=""
+    SELECTOR_SPEC=""
+    DEVICE_PATH=""
+    DEVICE_FSTYPE="${fstype}"
+    return 0
+  fi
+
+  case "${kind}" in
+    uuid)
+      selector="UUID=${value}"
+      actual_device="$(host_sh "blkid -U '${value}' 2>/dev/null || true")"
+      ;;
+    label)
+      selector="LABEL=${value}"
+      actual_device="$(host_sh "blkid -L '${value}' 2>/dev/null || true")"
+      ;;
+    device)
+      selector="${value}"
+      actual_device="$(host_sh "if [ -b '${value}' ]; then printf '%s' '${value}'; fi")"
+      ;;
+    *)
+      SELECTOR_KIND="invalid"
+      SELECTOR_VALUE="${value}"
+      SELECTOR_SPEC=""
+      DEVICE_PATH=""
+      DEVICE_FSTYPE="${fstype}"
+      return 0
+      ;;
+  esac
+
+  actual_fstype=""
+  actual_uuid=""
+  actual_label=""
+  if [ -n "${actual_device}" ]; then
+    actual_fstype="$(host_sh "blkid -o value -s TYPE '${actual_device}' 2>/dev/null || true")"
+    actual_uuid="$(host_sh "blkid -o value -s UUID '${actual_device}' 2>/dev/null || true")"
+    actual_label="$(host_sh "blkid -o value -s LABEL '${actual_device}' 2>/dev/null || true")"
+  fi
+
+  expected_fstype="${fstype:-${USB_SCRATCH_DEFAULT_FSTYPE}}"
+  if [ -n "${actual_fstype}" ] && [ -n "${expected_fstype}" ] && [ "${actual_fstype}" != "${expected_fstype}" ]; then
+    SELECTOR_KIND="fs-mismatch"
+    SELECTOR_VALUE="${selector}"
+    SELECTOR_SPEC="${selector}"
+    DEVICE_PATH="${actual_device}"
+    DEVICE_FSTYPE="${actual_fstype}"
+    return 0
+  fi
+
+  SELECTOR_KIND="${kind}"
+  SELECTOR_VALUE="${value}"
+  SELECTOR_SPEC="${selector}"
+  DEVICE_PATH="${actual_device}"
+  DEVICE_FSTYPE="${expected_fstype}"
+  DEVICE_UUID="${actual_uuid}"
+  DEVICE_LABEL="${actual_label}"
+}
+
+ensure_directories() {
+  local target source_dir
+  mkdir -p "${STATE_DIR}" "${HOST_ROOT}${USB_SCRATCH_MOUNTPOINT}"
+  for target in "${TARGET_PATHS[@]}"; do
+    mkdir -p "${HOST_ROOT}${target}" "${HOST_ROOT}${USB_SCRATCH_MOUNTPOINT}${target}"
+  done
+}
+
+ensure_usb_mount_live() {
+  local existing_source
+  existing_source="$(find_existing_mount_source "${USB_SCRATCH_MOUNTPOINT}")"
+  if [ -n "${existing_source}" ] && [ -n "${DEVICE_PATH}" ] && [ "${existing_source}" != "${DEVICE_PATH}" ] && [ "${existing_source}" != "${SELECTOR_SPEC}" ]; then
+    log "usb scratch already mounted from unexpected source ${existing_source}"
+    return 1
+  fi
+
+  host_sh "mkdir -p '${USB_SCRATCH_MOUNTPOINT}'; mountpoint -q '${USB_SCRATCH_MOUNTPOINT}' || mount '${USB_SCRATCH_MOUNTPOINT}'"
+  return 0
+}
+
+free_space_gib() {
+  host_sh "df -Pk '${USB_SCRATCH_MOUNTPOINT}' | awk 'NR==2 { printf \"%.0f\", \$4 / 1024 / 1024 }'"
+}
+
+target_bound_to_scratch() {
+  local target="$1"
+  local current_source
+  current_source="$(find_existing_mount_source "${target}")"
+  [ "${current_source}" = "${USB_SCRATCH_MOUNTPOINT}${target}" ]
+}
+
+seed_target_data() {
+  local target="$1"
+  local source_dir
+  source_dir="${USB_SCRATCH_MOUNTPOINT}${target}"
+  host_sh "mkdir -p '${source_dir}' '${target}'; if command -v rsync >/dev/null 2>&1; then rsync -aHAX --numeric-ids '${target}/' '${source_dir}/'; else tar -C '${target}' -cf - . | tar -C '${source_dir}' -xf -; fi"
+}
+
+mount_target_live() {
+  local target="$1"
+  host_sh "mountpoint -q '${target}' || mount '${target}'"
+}
+
+cutover_needed() {
+  local target
+  for target in "${TARGET_PATHS[@]}"; do
+    if ! target_bound_to_scratch "${target}"; then
+      return 0
+    fi
+  done
+  return 1
+}
+
+perform_cutover() {
+  local jitter target
+
+  if ! cutover_needed; then
+    return 0
+  fi
+
+  jitter=0
+  if [ "${USB_SCRATCH_CUTOVER_JITTER_MAX_SEC}" -gt 0 ]; then
+    jitter=$(( RANDOM % (USB_SCRATCH_CUTOVER_JITTER_MAX_SEC + 1) ))
+  fi
+  if [ "${jitter}" -gt 0 ]; then
+    log "sleeping ${jitter}s before first live cutover"
+    sleep "${jitter}"
+  fi
+
+  log "stopping k3s-agent for USB scratch cutover"
+  host_sh "systemctl stop k3s-agent"
+  agent_stopped=1
+
+  for target in "${TARGET_PATHS[@]}"; do
+    if ! target_bound_to_scratch "${target}"; then
+      log "seeding ${target} into ${USB_SCRATCH_MOUNTPOINT}${target}"
+      seed_target_data "${target}"
+      log "mounting bind target ${target}"
+      mount_target_live "${target}"
+    fi
+  done
+
+  log "starting k3s-agent after USB scratch cutover"
+  host_sh "systemctl start k3s-agent"
+  agent_stopped=0
+}
+
+reconcile_once() {
+  local fstab_changed=false free_gib selector_detail
+
+  load_config
+  resolve_selector
+  ensure_directories
+
+  case "${SELECTOR_KIND}" in
+    disabled)
+      annotate_node "disabled" "inventory-disabled" "none"
+      log "inventory disables USB scratch on ${NODE_NAME}"
+      return 0
+      ;;
+    missing)
+      annotate_node "pending" "missing-inventory" "none"
+      log "no inventory entry or default selector for ${NODE_NAME}"
+      return 0
+      ;;
+    invalid)
+      annotate_node "error" "invalid-selector" "${SELECTOR_VALUE}"
+      log "invalid selector configured for ${NODE_NAME}"
+      return 0
+      ;;
+    fs-mismatch)
+      annotate_node "error" "filesystem-mismatch" "${SELECTOR_SPEC}"
+      log "filesystem mismatch on ${DEVICE_PATH}: expected ${USB_SCRATCH_DEFAULT_FSTYPE}, got ${DEVICE_FSTYPE}"
+      return 0
+      ;;
+  esac
+
+  selector_detail="${SELECTOR_SPEC}"
+
+  if ensure_fstab_block "${SELECTOR_SPEC}" "${DEVICE_FSTYPE}"; then
+    fstab_changed=true
+    host_sh "systemctl daemon-reload || true"
+  fi
+
+  if [ -z "${DEVICE_PATH}" ]; then
+    annotate_node "pending" "device-not-found" "${selector_detail}"
+    log "scratch device not present yet for selector ${selector_detail}"
+    return 0
+  fi
+
+  if ! ensure_usb_mount_live; then
+    annotate_node "error" "mount-conflict" "${selector_detail}"
+    return 0
+  fi
+
+  free_gib="$(free_space_gib || true)"
+  if [ -z "${free_gib}" ]; then
+    annotate_node "error" "free-space-check-failed" "${selector_detail}"
+    return 0
+  fi
+
+  if [ "${free_gib}" -lt "${USB_SCRATCH_REQUIRED_FREE_GIB}" ]; then
+    annotate_node "error" "insufficient-free-space-${free_gib}Gi" "${selector_detail}"
+    log "usb scratch free space ${free_gib}Gi below required ${USB_SCRATCH_REQUIRED_FREE_GIB}Gi"
+    return 0
+  fi
+
+  if host_sh "systemctl list-unit-files | grep -q '^k3s-agent.service'"; then
+    perform_cutover
+  else
+    annotate_node "error" "missing-k3s-agent-service" "${selector_detail}"
+    log "k3s-agent.service missing on ${NODE_NAME}"
+    return 0
+  fi
+
+  if cutover_needed; then
+    annotate_node "error" "bind-mount-incomplete" "${selector_detail}"
+    return 0
+  fi
+
+  if [ "${fstab_changed}" = true ]; then
+    log "usb scratch fstab refreshed for ${NODE_NAME}"
+  fi
+  annotate_node "ready" "scratch-online-${free_gib}Gi" "${selector_detail}"
+  log "usb scratch ready on ${NODE_NAME} via ${selector_detail} mounted at ${USB_SCRATCH_MOUNTPOINT}"
+}
+
+main() {
+  while true; do
+    reconcile_once || true
+    if [ "${ONE_SHOT}" = "true" ]; then
+      exit 0
+    fi
+    sleep "${USB_SCRATCH_RECONCILE_INTERVAL_SEC}"
+  done
+}
+
+main