diff --git a/bootstrap/standup.sh b/bootstrap/standup.sh
index b7f9e3e..366849a 100755
--- a/bootstrap/standup.sh
+++ b/bootstrap/standup.sh
@@ -26,6 +26,11 @@
 #
 #   --confirm-destructive is required by `unwedge` only. Everything else is additive or reversible.
 #
+#   --s3-endpoint <url> makes `s3check` probe a CANDIDATE backup endpoint instead of the live
+#   cluster-vars value, so a proposed target can be PROVEN before it is authored into cluster-vars.
+#   `s3check` writes and then deletes ONE throwaway object under `<prefix>/.s3check/`; it changes
+#   nothing else and applies nothing. See infra/BACKUP-R2.md.
+#
 set -euo pipefail
 
 # ---------------------------------------------------------------------------- args
@@ -85,10 +90,18 @@ say "target confirmed: ${live_server}"
 
 # Dependency order. Flux enforces the edges itself via dependsOn; resuming in this order simply means
 # each wait is meaningful instead of blocking on a dependency that is still suspended.
-#   flux-system -> cilium -> platform -> platform-config -> {leaf tiers, apps-wave-0} -> wave-1 -> wave-2
-TIER_ORDER=(platform platform-config oauth2-proxy headlamp homepage crafty apps-wave-0 apps-wave-1 apps-wave-2 apps-vms)
-# velero is NOT in that list on purpose — see step `resume`: it consumes S3_BACKUP_ENDPOINT, which on
-# prod is an intentionally-invalid TBD placeholder pending an operator decision.
+#   flux-system -> cilium -> platform -> platform-config -> platform-config-cdi
+#                                     -> {leaf tiers, apps-wave-0} -> wave-1 -> wave-2 -> apps-vms
+#
+# `platform-config-cdi` MUST stay in this list and MUST stay before apps-vms. It carries the CDI
+# StorageProfiles, which were split out of platform-config because StorageProfile's CRD does not exist
+# until cdi-operator has reconciled the CDI CR (clusters/base/platform-config-cdi.yaml). apps-vms
+# dependsOn it: apps/vms/unifi provisions on `longhorn-vm`, and without the profile applied CDI infers
+# ReadWriteOnce instead of the authored ReadWriteMany — permanently non-live-migratable for that disk.
+# Omitting it here would make `resume` return success without ever waiting on the tier that guarantees it.
+TIER_ORDER=(platform platform-config platform-config-cdi oauth2-proxy headlamp homepage crafty apps-wave-0 apps-wave-1 apps-wave-2 apps-vms)
+# velero is NOT in that list on purpose — see step `resume`: it consumes S3_BACKUP_ENDPOINT, which is
+# an intentionally-invalid placeholder until the operator supplies the real R2 endpoint.
 
 cvar() { kubectl -n flux-system get cm cluster-vars -o jsonpath="{.data.$1}" 2>/dev/null || true; }
 
@@ -150,6 +163,354 @@ dns_diff() { # <before> <after>  — returns non-zero if anything changed
   return 1
 }
 
+# ======================================================================= s3check plumbing
+# WHY THIS IS THIS BIG. The previous version of `s3check` curl'd /minio/health/live and reported
+# REACHABLE. That probe could not pass against Cloudflare R2 (no such path), and reachability is not
+# the property anyone cares about: a reachable endpoint with a wrong key, a missing bucket, or R2's
+# checksum rejection still yields a velero tier that reports Ready while NO backup exists. What must
+# be proven is the write path Velero and CNPG-barman actually use, with the credentials they actually
+# hold, from the network position they actually occupy.
+
+# Pinned. The AWS CLI is a deliberate choice over `minio/mc`:
+#   - it prints the S3 ERROR CODE (NoSuchBucket / AccessDenied / InvalidAccessKeyId / InvalidArgument),
+#     so a failure can be NAMED and turned into a fix instead of guessed at from an HTTP status;
+#   - it exposes the FLEXIBLE-CHECKSUM behaviour that is the R2 trap
+#     (AWS_REQUEST_CHECKSUM_CALCULATION), so the trap can be reproduced on purpose here instead of
+#     discovered by a silently-failing backup at 03:00;
+#   - its image carries bash + coreutils. `minio/mc` ships no sed/awk/diff — that minimalism has
+#     already broken one probe in this repo — and it cannot be made to send the checksum headers, so
+#     it cannot test for the trap at all.
+S3CHECK_IMAGE="amazon/aws-cli:2.36.40"
+S3CHECK_RUN_ID="$(date +%s)"
+
+# Throwaway probe pods, tracked so they are removed on EVERY exit path (including `die`). A probe
+# must never leave a pod behind on a live cluster.
+S3CHECK_PODS=()
+s3_cleanup_pods() {
+  local p
+  for p in ${S3CHECK_PODS[@]+"${S3CHECK_PODS[@]}"}; do
+    kubectl -n "${p%%/*}" delete pod "${p#*/}" --ignore-not-found --wait=false >/dev/null 2>&1 || true
+  done
+  S3CHECK_PODS=()
+}
+trap s3_cleanup_pods EXIT
+
+# TRUE when the endpoint is not a usable target. `TBD-*` alone was WRONG once the placeholder became
+# `https://TBD-R2-ACCOUNT-ID.r2.cloudflarestorage.com`: that does not START with TBD-, so the old
+# prefix pattern matched nothing and `resume` would have resumed velero straight onto a placeholder
+# hostname — the exact silent-no-backups failure the guard exists to prevent. Match anywhere.
+s3_is_placeholder() { # <endpoint>
+  case "$1" in
+    ""|*TBD*|*tbd-*|*REPLACE-ME*|*replace-me*|*CHANGE-ME*|*change-me*) return 0 ;;
+  esac
+  return 1
+}
+
+# Refuse any value that is not a plain URL/name fragment. This is BOTH a safety guard — these values
+# are interpolated into the probe pod's JSON overrides AND into a shell script that runs inside it, so
+# a quote, a backslash or a newline could rewrite either — and a correctness guard: a cluster-vars
+# value with a trailing space or a stray quote is a defect, not something to paper over.
+s3_safe_token() { # <label> <value>
+  case "$2" in
+    *[!A-Za-z0-9:/._-]*) die "refusing to probe: $1 contains a character outside [A-Za-z0-9:/._-].
+       That is either a corrupt cluster-vars value or an injection attempt. Value (quoted): $(printf '%q' "$2")" ;;
+  esac
+}
+
+# ---------------------------------------------------------------- the in-pod probe
+# Emitted to the pod base64-encoded, so nothing in it has to survive JSON or shell quoting.
+# CONTRACT WITH THE CALLER (this is what makes a silent no-op impossible):
+#   - every proven property prints exactly one `S3CHECK-OK[n] ...` line and increments n;
+#   - every failure prints `S3CHECK-FAIL ...` and is counted;
+#   - the LAST line is `S3CHECK-RESULT PASS|FAIL assertions=<n> failures=<n>`.
+# The caller independently knows how many assertions this environment must produce and re-counts the
+# OK lines itself, so neither a truncated log, a skipped bucket, an empty log, nor a lying result line
+# can be read as success. (A CRD guard in this repo once counted a blank line as "1 CRD" and sailed
+# past; that class of bug is designed out here rather than commented about.)
+s3_probe_script() {
+  cat <<'PROBE'
+set -u
+umask 077
+A=0; F=0
+ok()   { A=$((A+1)); printf 'S3CHECK-OK[%d] %s\n' "$A" "$*"; }
+bad()  { F=$((F+1)); printf 'S3CHECK-FAIL %s\n' "$*"; }
+note() { printf 'S3CHECK-NOTE %s\n' "$*"; }
+verdict() {
+  if [ "${F}" -eq 0 ] && [ "${A}" -gt 0 ]; then
+    printf 'S3CHECK-RESULT PASS assertions=%d failures=0\n' "${A}"; exit 0
+  fi
+  printf 'S3CHECK-RESULT FAIL assertions=%d failures=%d\n' "${A}" "${F}"; exit 1
+}
+
+for v in S3EP S3REGION S3TARGETS S3KEY CRED_MODE; do
+  eval "x=\${${v}-}"
+  [ -n "${x}" ] || { bad "required env ${v} is empty — the probe was launched wrong"; verdict; }
+done
+
+export AWS_EC2_METADATA_DISABLED=true
+export AWS_PAGER=""
+export AWS_DEFAULT_REGION="${S3REGION}"
+export AWS_REGION="${S3REGION}"
+export AWS_MAX_ATTEMPTS=2
+export AWS_RETRY_MODE=standard
+export AWS_CONFIG_FILE=/tmp/s3check-aws-config
+# Path-style addressing, because both targets need it: MinIO on a bare IP has no virtual-host names,
+# and R2's S3 API is documented path-style. Checksums OFF, mirroring `checksumAlgorithm: ""` on the
+# Velero BSL — this run must exercise the same wire shape the real backup will use. Written to the
+# CONFIG FILE as well as the environment so the setting holds even if one channel is ignored by a
+# future CLI version.
+{
+  echo '[default]'
+  echo 'request_checksum_calculation = when_required'
+  echo 'response_checksum_validation = when_required'
+  echo 's3 ='
+  echo '    addressing_style = path'
+} > "${AWS_CONFIG_FILE}"
+
+# ---- (1) the credential loads at all -------------------------------------------------
+# NEVER print a credential value, in either `key: value` or `key=value` shape. Only booleans,
+# byte counts and lengths leave this pod.
+case "${CRED_MODE}" in
+  file)
+    cf="${AWS_SHARED_CREDENTIALS_FILE-}"
+    if [ -z "${cf}" ] || [ ! -s "${cf}" ]; then
+      bad "credential file '${cf:-<unset>}' is missing or empty — the Secret key did not mount"
+    elif ! grep -Eq '^[[:space:]]*\[default\][[:space:]]*$' "${cf}"; then
+      bad "credential file has no [default] profile. velero-plugin-for-aws reads an AWS INI file from
+        the 'cloud' key of velero-cloud-credentials; without [default] every backup fails at RUNTIME"
+    elif ! grep -Eq '^[[:space:]]*aws_access_key_id[[:space:]]*=[[:space:]]*[^[:space:]]' "${cf}" \
+      || ! grep -Eq '^[[:space:]]*aws_secret_access_key[[:space:]]*=[[:space:]]*[^[:space:]]' "${cf}"; then
+      bad "credential file [default] lacks a non-empty aws_access_key_id / aws_secret_access_key"
+    else
+      ok "credential LOADS: AWS INI with [default] + both keys ($(wc -c < "${cf}") bytes; values never printed)"
+    fi
+    ;;
+  env)
+    if [ -z "${AWS_ACCESS_KEY_ID-}" ] || [ -z "${AWS_SECRET_ACCESS_KEY-}" ]; then
+      bad "AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY did not arrive from the Secret (missing ACCESS_KEY_ID / ACCESS_SECRET_KEY key?)"
+    else
+      ok "credential LOADS: access key id present (${#AWS_ACCESS_KEY_ID} chars; values never printed)"
+    fi
+    ;;
+  *) bad "unknown CRED_MODE '${CRED_MODE}'" ;;
+esac
+[ "${F}" -eq 0 ] || verdict     # no point talking to S3 with no credential
+
+OUT=""; RC=0
+awsx() { OUT="$(aws --endpoint-url "${S3EP}" "$@" 2>&1)"; RC=$?; return 0; }
+
+detail() { printf '%s\n' "${OUT}" | head -n 12 | while IFS= read -r l; do printf 'S3CHECK-DETAIL %s\n' "${l}"; done; }
+
+# Every failure is NAMED and given the fix. An unclassified failure is still a failure.
+diagnose() { # <operation label>
+  local op="$1"
+  case "${OUT}" in
+    *InvalidArgument*|*checksum*|*Checksum*)
+      bad "${op}: 400 InvalidArgument — THE R2 CHECKSUM TRAP. velero-plugin-for-aws v1.14+ bundles an
+        AWS SDK that sends x-amz-sdk-checksum-algorithm / x-amz-checksum-crc32 on every PUT, and
+        Cloudflare R2 REJECTS those headers with HTTP 400 InvalidArgument, so every Velero backup and
+        every kopia blob upload fails. FIX: checksumAlgorithm: \"\" must be present in the
+        backupStorageLocation config in platform/velero/helmrelease.yaml. This probe already disables
+        checksums, so seeing this here means the client sent one anyway — treat it as a hard blocker." ;;
+    *"Could not connect"*|*EndpointConnectionError*|*ConnectTimeoutError*|*"Failed to establish"*|\
+    *"Name or service not known"*|*"nodename nor servname"*|*"Temporary failure in name resolution"*|\
+    *"Connection reset"*|*"Read timeout"*)
+      bad "${op}: this POD cannot reach ${S3EP} (connect / DNS / timeout). Velero and CNPG would
+        install perfectly clean and then fail every backup at RUNTIME — a tier that looks healthy
+        while no backup exists. This is the reading that matters: the workstation's own reachability
+        is irrelevant (prod sits on the SOHO net, pfSense's WAN; the dev LAN's MinIO sits INSIDE
+        pfSense) and a host-side probe has already misled this project once. Fix pod egress/routing,
+        or give this environment its own endpoint." ;;
+    *NoSuchBucket*|*"(404)"*|*"Not Found"*)
+      bad "${op}: the bucket does not exist at this endpoint. Create it before enabling velero/CNPG
+        (R2: dashboard -> R2 -> Create bucket; see infra/BACKUP-R2.md)." ;;
+    *InvalidAccessKeyId*|*SignatureDoesNotMatch*|*"(401)"*|*Unauthorized*)
+      bad "${op}: the endpoint REJECTED these credentials. Wrong key, or a key belonging to a
+        different R2 account / MinIO. Re-encrypt the credential Secrets — infra/BACKUP-R2.md." ;;
+    *AccessDenied*|*"(403)"*|*Forbidden*)
+      bad "${op}: authenticated but FORBIDDEN. The token is not scoped to this bucket. An R2 API token
+        needs Object Read & Write on BOTH the velero and cnpg buckets." ;;
+    *) bad "${op}: unclassified failure (rc=${RC}). Treated as a FAILURE, never as unknown-so-fine." ;;
+  esac
+  detail
+}
+
+PAY=/tmp/s3check.payload
+GOT=/tmp/s3check.got
+head -c 4096 /dev/urandom | base64 > "${PAY}"
+[ -s "${PAY}" ] || { bad "could not generate a probe payload inside the pod"; verdict; }
+
+TRAP_DONE=0
+for t in ${S3TARGETS}; do
+  B="${t%%:*}"; P="${t#*:}"
+  [ "${P}" = "${B}" ] && P=""
+  if [ -n "${P}" ]; then K="${P}/.s3check/${S3KEY}"; else K=".s3check/${S3KEY}"; fi
+
+  # ---- (2) the bucket exists and is LISTABLE. This is the operation Velero's BSL sync and Barman's
+  #          WAL scan both perform; ListBuckets deliberately is NOT used, because neither consumer
+  #          needs it and a correctly bucket-scoped R2 token may not grant it.
+  args=(s3api list-objects-v2 --bucket "${B}" --max-keys 1)
+  [ -n "${P}" ] && args+=(--prefix "${P}/")
+  awsx "${args[@]}"
+  if [ "${RC}" -eq 0 ]; then
+    ok "${B}: bucket EXISTS, AUTHENTICATES and is LISTABLE (prefix '${P:-<bucket root>}')"
+  else
+    diagnose "LIST ${B}"
+    continue      # a short assertion count is how the caller learns this target was abandoned
+  fi
+
+  # ---- (3) PUT -> GET -> byte-compare -> DELETE. A real write, not a HEAD: HEAD on a bucket proves
+  #          nothing about whether an object can be STORED (wrong scope, checksum rejection and
+  #          read-only tokens all pass a HEAD and fail a backup).
+  awsx s3api put-object --bucket "${B}" --key "${K}" --body "${PAY}"
+  if [ "${RC}" -eq 0 ]; then ok "${B}: PUT ${K} accepted (genuine write path)"
+  else diagnose "PUT ${B}/${K}"; continue; fi
+
+  rm -f "${GOT}"
+  awsx s3api get-object --bucket "${B}" --key "${K}" "${GOT}"
+  if [ "${RC}" -eq 0 ]; then ok "${B}: GET ${K} returned an object"
+  else diagnose "GET ${B}/${K}"
+       aws --endpoint-url "${S3EP}" s3api delete-object --bucket "${B}" --key "${K}" >/dev/null 2>&1 || true
+       continue; fi
+
+  sp="$(wc -c < "${PAY}")"; sg="$(wc -c < "${GOT}" 2>/dev/null || echo 0)"
+  hp="$(sha256sum < "${PAY}")"; hp="${hp%% *}"
+  hg="$(sha256sum < "${GOT}")"; hg="${hg%% *}"
+  if [ "${sp}" = "${sg}" ] && [ -n "${hp}" ] && [ "${hp}" = "${hg}" ]; then
+    ok "${B}: round trip is BYTE-IDENTICAL (${sp} bytes, sha256 matches)"
+  else
+    bad "${B}: round trip CORRUPTED — wrote ${sp} bytes (sha256 ${hp}), read back ${sg} bytes (sha256 ${hg})"
+  fi
+
+  awsx s3api delete-object --bucket "${B}" --key "${K}"
+  if [ "${RC}" -eq 0 ]; then ok "${B}: DELETE ${K} accepted"
+  else diagnose "DELETE ${B}/${K}"; fi
+
+  awsx s3api head-object --bucket "${B}" --key "${K}"
+  if [ "${RC}" -ne 0 ]; then ok "${B}: scratch object is GONE — the probe left nothing behind"
+  else bad "${B}: scratch object ${K} STILL EXISTS after DELETE. Remove it by hand; the probe leaked."; fi
+
+  # ---- (4) the R2 checksum trap, probed ON PURPOSE. Informational by design: the authored BSL sets
+  #          checksumAlgorithm: "", so a rejection here does NOT mean backups are broken — it means
+  #          that line is LOAD-BEARING. Reported either way so the operator learns which world this
+  #          endpoint lives in before, not after, enabling velero.
+  if [ "${TRAP_DONE}" -eq 0 ]; then
+    TRAP_DONE=1
+    TK="${K}.checksum-trap-probe"
+    OUT="$(AWS_REQUEST_CHECKSUM_CALCULATION=when_supported \
+           aws --endpoint-url "${S3EP}" s3api put-object --bucket "${B}" --key "${TK}" --body "${PAY}" 2>&1)"; RC=$?
+    if [ "${RC}" -eq 0 ]; then
+      note "checksum probe: this endpoint ACCEPTS a checksum-bearing PUT — the R2 checksum trap is NOT
+        present here (expected for MinIO). checksumAlgorithm: \"\" stays harmless."
+      aws --endpoint-url "${S3EP}" s3api delete-object --bucket "${B}" --key "${TK}" >/dev/null 2>&1 \
+        || note "checksum probe: could NOT delete ${TK} — remove it by hand"
+    else
+      case "${OUT}" in
+        *InvalidArgument*)
+          note "checksum probe: R2 CHECKSUM TRAP CONFIRMED at this endpoint — a PUT carrying
+        x-amz-sdk-checksum-algorithm / x-amz-checksum-crc32 is rejected with 400 InvalidArgument.
+        checksumAlgorithm: \"\" in platform/velero/helmrelease.yaml is LOAD-BEARING: delete it, or bump
+        velero-plugin-for-aws without re-checking it, and EVERY backup breaks." ;;
+        *) note "checksum probe: inconclusive (rc=${RC}) — neither confirms nor rules out the trap." ;;
+      esac
+    fi
+  fi
+done
+
+verdict
+PROBE
+}
+
+# ---------------------------------------------------------------- run one probe pod
+# <ns> <file|env> <secret> <space-separated bucket:prefix targets>  <endpoint> <region>
+s3_probe() {
+  local ns="$1" mode="$2" sec="$3" targets="$4" ep="$5" region="$6"
+  # $$ alone is NOT unique here: inside the dev container this script is frequently PID 1, so two runs
+  # would reuse the same pod name AND the same scratch object key. Mix in the epoch second.
+  local pod="s3check-$$-${S3CHECK_RUN_ID}-${mode}"
+
+  # What this environment MUST produce: 1 credential assertion + 6 per bucket (list, put, get,
+  # byte-compare, delete, delete-verified). Computed HERE, by the caller, from the target list — the
+  # pod's own claim is never the only source of the expected count.
+  local t n=0
+  for t in ${targets}; do n=$((n+1)); done
+  local min=$((1 + 6 * n))
+
+  local volsjson="" mountsjson="" creds=""
+  case "${mode}" in
+    file)  # exactly how velero consumes it: the `cloud` key as an AWS INI credentials FILE
+      volsjson='"volumes":[{"name":"s3creds","secret":{"secretName":"'"${sec}"'","items":[{"key":"cloud","path":"credentials"}],"defaultMode":256}}],'
+      mountsjson='"volumeMounts":[{"name":"s3creds","mountPath":"/s3creds","readOnly":true}],'
+      creds='{"name":"AWS_SHARED_CREDENTIALS_FILE","value":"/s3creds/credentials"},{"name":"CRED_MODE","value":"file"}' ;;
+    env)   # exactly how CNPG/barman consumes it: discrete ACCESS_KEY_ID / ACCESS_SECRET_KEY keys
+      creds='{"name":"AWS_ACCESS_KEY_ID","valueFrom":{"secretKeyRef":{"name":"'"${sec}"'","key":"ACCESS_KEY_ID"}}},{"name":"AWS_SECRET_ACCESS_KEY","valueFrom":{"secretKeyRef":{"name":"'"${sec}"'","key":"ACCESS_SECRET_KEY"}}},{"name":"CRED_MODE","value":"env"}' ;;
+    *) die "internal: unknown probe mode '${mode}'" ;;
+  esac
+
+  local b64; b64="$(s3_probe_script | base64 | tr -d '\n')"
+  [ -n "${b64}" ] || die "internal: probe script encoded to nothing"
+
+  # egress-class label: harmless here (the velero namespace is not an app namespace) but required by
+  # the require-egress-class-label ClusterPolicy in any namespace labelled app-namespace=true, which
+  # the CNPG credential namespaces are. Without it the probe pod would be REJECTED by admission and
+  # the check would report "unknown" instead of a result.
+  local overrides
+  overrides='{"apiVersion":"v1","metadata":{"labels":{"app.kubernetes.io/name":"s3check","homelab.keithjackson.dev/egress-class":"internet"}},"spec":{"restartPolicy":"Never","automountServiceAccountToken":false,'"${volsjson}"'"containers":[{"name":"s3check","image":"'"${S3CHECK_IMAGE}"'","imagePullPolicy":"IfNotPresent","command":["/bin/bash","-c","printf %s \"$PROBE_B64\" | base64 -d > /tmp/probe.sh && exec bash /tmp/probe.sh"],'"${mountsjson}"'"env":['"${creds}"',{"name":"PROBE_B64","value":"'"${b64}"'"},{"name":"S3EP","value":"'"${ep}"'"},{"name":"S3REGION","value":"'"${region}"'"},{"name":"S3TARGETS","value":"'"${targets}"'"},{"name":"S3KEY","value":"'"${pod}"'.probe"},{"name":"AWS_REQUEST_CHECKSUM_CALCULATION","value":"when_required"},{"name":"AWS_RESPONSE_CHECKSUM_VALIDATION","value":"when_required"}],"resources":{"requests":{"cpu":"50m","memory":"64Mi"},"limits":{"memory":"256Mi"}}}]}}'
+
+  say "probe: ns=${ns} secret=${sec} (${mode}) targets='${targets}'  → ${min} assertions required"
+  kubectl -n "${ns}" delete pod "${pod}" --ignore-not-found >/dev/null 2>&1 || true
+  S3CHECK_PODS+=("${ns}/${pod}")
+  kubectl -n "${ns}" run "${pod}" --restart=Never --image="${S3CHECK_IMAGE}" \
+      --overrides="${overrides}" >/dev/null 2>&1 \
+    || die "could NOT create the probe pod ${ns}/${pod} (admission policy? RBAC? quota?).
+       That is a FAILURE, not an unknown: nothing about ${ep} has been proven."
+
+  local i=0 phase=""
+  while [ "${i}" -lt 300 ]; do
+    phase="$(kubectl -n "${ns}" get pod "${pod}" -o jsonpath='{.status.phase}' 2>/dev/null || true)"
+    case "${phase}" in Succeeded|Failed) break ;; esac
+    sleep 5; i=$((i+5))
+  done
+  case "${phase}" in
+    Succeeded|Failed) ;;
+    *) local reason
+       reason="$(kubectl -n "${ns}" get pod "${pod}" \
+                 -o jsonpath='{.status.containerStatuses[0].state.waiting.reason}' 2>/dev/null || true)"
+       die "probe pod ${ns}/${pod} did not finish in ${i}s (phase=${phase:-<none>}, waiting=${reason:-none}).
+       NOT a pass. If waiting=ErrImagePull/ImagePullBackOff this cluster cannot pull ${S3CHECK_IMAGE}." ;;
+  esac
+
+  local log; log="$(kubectl -n "${ns}" logs "${pod}" 2>/dev/null || true)"
+  [ -n "${log}" ] || die "probe pod ${ns}/${pod} produced NO output (phase=${phase}). Failing closed —
+       an empty log is the shape of a probe that never ran, not of a healthy backup target."
+  printf '%s\n' "${log}" | while IFS= read -r l; do printf '    %s\n' "${l}"; done
+
+  # ---- the four independent accounting checks that make a silent no-op impossible ----
+  local okcount failcount resline nres verd a f
+  okcount="$(printf '%s\n' "${log}" | grep -c '^S3CHECK-OK\[' || true)"
+  failcount="$(printf '%s\n' "${log}" | grep -c '^S3CHECK-FAIL' || true)"
+  nres="$(printf '%s\n' "${log}" | grep -c '^S3CHECK-RESULT ' || true)"
+  [ "${nres}" = "1" ] || die "expected exactly ONE S3CHECK-RESULT line from ${ns}/${pod}, found ${nres}.
+       A missing verdict line means the probe died mid-way; it is never a pass."
+  resline="$(printf '%s\n' "${log}" | grep '^S3CHECK-RESULT ')"
+  read -r _ verd a f <<<"${resline}"
+  a="${a#assertions=}"; f="${f#failures=}"
+  case "${a}" in ''|*[!0-9]*) die "malformed verdict from ${ns}/${pod}: '${resline}'" ;; esac
+  case "${f}" in ''|*[!0-9]*) die "malformed verdict from ${ns}/${pod}: '${resline}'" ;; esac
+  [ "${verd}" = "PASS" ] || die "S3 ROUND TRIP FAILED against ${ep} (${ns}/${pod}: ${f} failure(s)).
+       Read the S3CHECK-FAIL lines above — each one names the cause and the fix. Do NOT enable velero
+       or CNPG backups against this endpoint until they are all gone."
+  [ "${f}" = "0" ]          || die "${ns}/${pod} claimed PASS while reporting ${f} failures — refusing to believe it."
+  [ "${failcount}" = "0" ]  || die "${ns}/${pod} claimed PASS but the log carries ${failcount} S3CHECK-FAIL line(s)."
+  [ "${a}" -ge "${min}" ]   || die "${ns}/${pod} claimed PASS with only ${a} assertions; ${min} are required
+       (1 credential + 6 per bucket). A short count means steps were SKIPPED — exactly the
+       degrade-to-a-successful-no-op this check exists to prevent."
+  [ "${okcount}" = "${a}" ] || die "assertion accounting mismatch for ${ns}/${pod}: ${okcount} S3CHECK-OK
+       lines in the log vs a claimed ${a}. Refusing to pass on a self-report that does not add up."
+  [ "${phase}" = "Succeeded" ] || die "${ns}/${pod} printed PASS but the pod ended ${phase}."
+  info "PROVEN: ${a} assertions, 0 failures, pod ${phase}, no object left behind."
+}
+
 # ============================================================================ steps
 step_preflight() {
   say "PREFLIGHT (read-only)"
@@ -200,13 +561,14 @@ step_preflight() {
     info "owner id is distinct and non-default: OK"
   fi
 
-  case "${s3}" in
-    ""|TBD-*) warn "S3_BACKUP_ENDPOINT is unset/placeholder ('${s3}'). velero AND apps-wave-0 consume it.
+  if s3_is_placeholder "${s3}"; then
+    warn "S3_BACKUP_ENDPOINT is unset/placeholder ('${s3}'). velero AND apps-wave-0 consume it.
        velero will be SKIPPED by the resume step. apps-wave-0 will still apply (the token IS defined,
        so strict substitution succeeds) but anything writing to that endpoint fails at RUNTIME, not at
-       apply time — so a green apps-wave-0 does NOT mean backups work. Operator decision required." ;;
-    *) info "S3 backup endpoint set: OK" ;;
-  esac
+       apply time — so a green apps-wave-0 does NOT mean backups work. Operator decision required."
+  else
+    info "S3 backup endpoint set: OK"
+  fi
 
   # COLD-START CRD ORDERING. Flux server-side dry-runs EVERY object in a Kustomization before applying
   # any of them, so a single unknown `kind` aborts the whole tier. platform-config applies the CDI CR
@@ -394,51 +756,139 @@ step_externaldns() {
 }
 
 step_s3check() {
-  say "S3 BACKUP ENDPOINT — reachability FROM INSIDE THE CLUSTER"
-  # Velero runs in-cluster, so the only reachability that counts is the pods' own. Probing from the
-  # workstation proves nothing either way: prod sits on the SOHO network (pfSense's WAN) while the
-  # dev LAN's MinIO sits inside pfSense, so host and pod egress differ; a healthy reading there
-  # network, and a healthy result there has already misled this project once.
-  local ep live; live="$(cvar S3_BACKUP_ENDPOINT)"
+  say "S3 BACKUP TARGET — PROVE A REAL ROUND TRIP FROM INSIDE THE CLUSTER"
+  # Velero and CNPG run in-cluster, so pod egress is the only reachability that counts: prod sits on
+  # the SOHO network (pfSense's WAN) while the dev LAN's MinIO sits INSIDE pfSense, so host and pod
+  # egress differ — and a healthy host-side reading has already misled this project once.
+  #
+  # WHAT THIS PROVES (and it fails closed on every one of them):
+  #   1. the committed credential loads and AUTHENTICATES, in the exact shape each consumer reads it
+  #      (velero: an AWS INI file from the `cloud` key; CNPG: discrete ACCESS_KEY_ID/ACCESS_SECRET_KEY);
+  #   2. each required bucket EXISTS and is LISTABLE under this environment's own prefix;
+  #   3. PUT -> GET -> byte-compare -> DELETE of a throwaway object under that prefix — the genuine
+  #      write path, not a HEAD (a HEAD passes with a read-only token and with R2 rejecting writes);
+  #   4. whether the R2 CHECKSUM TRAP is present at this endpoint, named explicitly either way.
+  #
+  # WHAT IT STILL DOES NOT PROVE: that Velero's kopia uploader and CNPG's barman-cloud themselves work
+  # against this target. Both are UNPROVEN against R2 in this repo. See infra/BACKUP-R2.md.
+  local ep live region
+  live="$(cvar S3_BACKUP_ENDPOINT)"
   info "live S3_BACKUP_ENDPOINT = ${live:-<unset>}"
   if [ -n "${S3_ENDPOINT_OVERRIDE}" ]; then
     # Probe a CANDIDATE endpoint before adopting it. The whole point is to find out whether a proposed
-    # backup target is reachable from this cluster's pods BEFORE authoring it into cluster-vars —
-    # otherwise the first evidence is silently-missing backups.
+    # backup target works from this cluster's pods BEFORE authoring it into cluster-vars — otherwise
+    # the first evidence is silently-missing backups.
     ep="${S3_ENDPOINT_OVERRIDE}"
     info "probing CANDIDATE endpoint from --s3-endpoint: ${ep}"
   else
     ep="${live}"
   fi
+  if s3_is_placeholder "${ep}"; then
+    die "no usable endpoint to probe (endpoint='${ep:-<unset>}').
+       cluster-vars still carries the loud placeholder. Pass --s3-endpoint https://<account-id>.r2.cloudflarestorage.com
+       to test a CANDIDATE before authoring it. See infra/BACKUP-R2.md."
+  fi
+  s3_safe_token S3_BACKUP_ENDPOINT "${ep}"
   case "${ep}" in
-    ""|TBD-*) die "no usable endpoint to probe (live='${live}'). Pass --s3-endpoint <url> to test a candidate." ;;
+    http://*|https://*) ;;
+    *) die "endpoint '${ep}' carries no http:// or https:// scheme — the AWS SDK needs one." ;;
   esac
 
-  local ns=velero pod=s3check-$$
-  kubectl get ns "${ns}" >/dev/null 2>&1 || ns=default
-  info "probing from a throwaway pod in namespace '${ns}'"
-  # --restart=Never + explicit delete in a trap: a probe must never leave a pod behind on a cluster.
-  trap 'kubectl -n "${ns}" delete pod "${pod}" --ignore-not-found --wait=false >/dev/null 2>&1 || true' RETURN
-  if kubectl -n "${ns}" run "${pod}" --restart=Never --image=curlimages/curl:8.11.1 --command --quiet \
-       -- curl -sS -o /dev/null -w '%{http_code}' --max-time 15 "${ep}/minio/health/live" >/dev/null 2>&1; then
-    local i=0 phase=""
-    while [ "$i" -lt 90 ]; do
-      phase="$(kubectl -n "${ns}" get pod "${pod}" -o jsonpath='{.status.phase}' 2>/dev/null || true)"
-      case "${phase}" in Succeeded|Failed) break ;; esac
-      sleep 5; i=$((i+5))
-    done
-    local out; out="$(kubectl -n "${ns}" logs "${pod}" 2>/dev/null || true)"
-    info "pod phase=${phase:-unknown} response=${out:-<none>}"
-    case "${out}" in
-      200|2??) info "REACHABLE: ${ep} answered from inside the cluster." ;;
-      *) warn "NOT REACHABLE from inside the cluster (phase=${phase}, body='${out}').
-       Velero would install cleanly and then fail every backup at RUNTIME — a tier that looks healthy
-       while no backup exists. Fix routing, or give this environment its own endpoint, before
-       resuming velero." ;;
-    esac
-  else
-    warn "could not create the probe pod (admission policy? image pull?). Reachability UNKNOWN."
+  # Region is a knob, not a constant: MinIO ignores it, R2 requires exactly `auto`, and an EMPTY value
+  # in cluster-vars silently builds a BSL with no region.
+  region="$(cvar S3_BACKUP_REGION)"
+  case "${ep}" in
+    *.r2.cloudflarestorage.com*)
+      if [ "${region}" != "auto" ]; then
+        warn "endpoint is Cloudflare R2 but cluster-vars S3_BACKUP_REGION='${region:-<unset>}'. R2 requires
+       exactly 'auto'. Probing with 'auto' anyway; FIX clusters/base/cluster-vars.yaml before enabling
+       velero, or the BackupStorageLocation is built with the wrong region."
+      fi
+      region=auto ;;
+    *)
+      if [ -z "${region}" ]; then
+        region="us-east-1"
+        warn "cluster-vars S3_BACKUP_REGION is EMPTY on this cluster. Probing with 'us-east-1' (MinIO
+       ignores it) — but the BSL would be rendered with region: \"\". Set it explicitly."
+      fi ;;
+  esac
+  s3_safe_token S3_BACKUP_REGION "${region}"
+
+  # Buckets come from the AUTHORED manifests + cluster-vars, never from a hardcoded name here: the
+  # whole point is to probe what this environment will really write to (R-ENV-02, no dev/prod fork).
+  local vbucket vprefix cpath cbucket cprefix rest
+  vbucket="$(yq -r '.spec.values.configuration.backupStorageLocation[0].bucket' \
+             platform/velero/helmrelease.yaml 2>/dev/null | tr -d '"')"
+  [ -n "${vbucket}" ] && [ "${vbucket}" != "null" ] \
+    || die "could not read the Velero bucket name from platform/velero/helmrelease.yaml"
+  vprefix="$(cvar VELERO_BACKUP_PREFIX)"
+
+  cpath="$(cvar CNPG_BACKUP_PATH)"
+  if [ -z "${cpath}" ]; then
+    warn "cluster-vars CNPG_BACKUP_PATH is EMPTY on this cluster. barmanObjectStore.destinationPath would
+       substitute to the empty string and EVERY WAL archive would fail at runtime. Probing the historical
+       default s3://cnpg so the round trip is still proven — but SET THIS VALUE."
+    cpath="s3://cnpg"
   fi
+  case "${cpath}" in s3://*) ;; *) die "CNPG_BACKUP_PATH='${cpath}' is not an s3:// URL." ;; esac
+  rest="${cpath#s3://}"; cbucket="${rest%%/*}"
+  if [ "${rest}" = "${cbucket}" ]; then cprefix=""; else cprefix="${rest#*/}"; fi
+  cprefix="${cprefix%/}"
+  [ -n "${cbucket}" ] || die "CNPG_BACKUP_PATH='${cpath}' names no bucket."
+
+  s3_safe_token velero-bucket "${vbucket}"; s3_safe_token VELERO_BACKUP_PREFIX "${vprefix}"
+  s3_safe_token cnpg-bucket   "${cbucket}"; s3_safe_token CNPG_BACKUP_PATH-prefix "${cprefix}"
+
+  say "what is about to be proven"
+  info "endpoint    ${ep}"
+  info "region      ${region}"
+  info "velero      bucket '${vbucket}'  prefix '${vprefix:-<bucket root>}'   (authored bucket + VELERO_BACKUP_PREFIX)"
+  info "cnpg        bucket '${cbucket}'  prefix '${cprefix:-<bucket root>}'   (from CNPG_BACKUP_PATH)"
+  info "scratch key <prefix>/.s3check/<pod>.probe — written, read back, byte-compared, DELETED"
+
+  local ran=0 keys
+  # (a) Velero's own credential, from its own namespace, mounted the way the aws plugin reads it.
+  if kubectl get ns velero >/dev/null 2>&1 \
+     && kubectl -n velero get secret velero-cloud-credentials >/dev/null 2>&1; then
+    # List KEY NAMES only. Never pipe or print a value (a careless redaction has leaked a password
+    # into a transcript on this project already). go-template, not jsonpath: kubectl's jsonpath
+    # cannot range over a map's keys (`range $k,$v :=` is rejected, U+002C) and returns EMPTY, which
+    # silently looked like "the key is missing".
+    keys="$(kubectl -n velero get secret velero-cloud-credentials \
+            -o go-template='{{range $k,$v := .data}}{{$k}}{{"\n"}}{{end}}' 2>/dev/null || true)"
+    printf '%s\n' "${keys}" | grep -qx 'cloud' \
+      || die "Secret velero/velero-cloud-credentials carries no 'cloud' key (keys: $(printf '%s' "${keys}" | tr '\n' ' ')).
+       velero-plugin-for-aws reads exactly that key as an AWS INI file; without it every backup fails
+       at RUNTIME while the HelmRelease reports Ready."
+    s3_probe velero file velero-cloud-credentials "${vbucket}:${vprefix}" "${ep}" "${region}"
+    ran=$((ran+1))
+  else
+    warn "no Secret velero/velero-cloud-credentials on this cluster — Velero's own credential could NOT
+       be proven. That is expected before the velero tier has ever reconciled here; it is not a pass."
+  fi
+
+  # (b) A CNPG/barman credential, discovered rather than hardcoded (R-ENV-02: no per-environment list
+  #     of app names in this script). Any one of them proves the key + the cnpg bucket + the discrete
+  #     ACCESS_KEY_ID/ACCESS_SECRET_KEY shape; they are all kept in sync by design.
+  local pick cns csec
+  pick="$(kubectl get secret -A -o jsonpath='{range .items[*]}{.metadata.namespace}{"/"}{.metadata.name}{"\n"}{end}' 2>/dev/null \
+          | grep -- '-db-backup-credentials$' | head -n 1 || true)"
+  if [ -n "${pick}" ]; then
+    cns="${pick%%/*}"; csec="${pick#*/}"
+    s3_probe "${cns}" env "${csec}" "${cbucket}:${cprefix}" "${ep}" "${region}"
+    ran=$((ran+1))
+  else
+    warn "no *-db-backup-credentials Secret found in any namespace — the CNPG/barman credential could
+       NOT be proven."
+  fi
+
+  [ "${ran}" -gt 0 ] || die "NO backup credential Secret exists on this cluster, so NOTHING could be
+       proven about ${ep}. That is a FAILURE, not a skip: a green s3check must never mean 'I found
+       nothing to check'."
+
+  say "S3 ROUND TRIP PROVEN from inside the cluster: ${ep} (${ran} credential path(s))"
+  info "STILL UNPROVEN by this step: Velero's kopia uploader and CNPG barman-cloud against this target,"
+  info "and a RESTORE. A backup that has never been restored is not a backup — see infra/BACKUP-R2.md."
 }
 
 step_resume() {
@@ -453,13 +903,20 @@ step_resume() {
     wait_ready "$n" 900 || { warn "stopping at $n — a partial, understood bring-up beats a forced green."; return 1; }
   done
 
-  case "${s3}" in
-    ""|TBD-*) warn "velero left SUSPENDED: S3_BACKUP_ENDPOINT='${s3}' is not a usable endpoint.
+  # The placeholder test MUST be substring-based. It was `TBD-*` (a PREFIX match) while the placeholder
+  # was `TBD-PROD-…`; the R2 move changed it to `https://TBD-R2-ACCOUNT-ID.r2.cloudflarestorage.com`,
+  # which does not START with TBD- — so this case arm silently stopped matching and `resume` would have
+  # RESUMED velero onto a placeholder hostname on prod. That is the precise failure this guard exists
+  # to prevent, reintroduced by a value change in another file. s3_is_placeholder matches anywhere.
+  if s3_is_placeholder "${s3}"; then
+    warn "velero left SUSPENDED: S3_BACKUP_ENDPOINT='${s3}' is not a usable endpoint.
        Resuming it would create a BackupStorageLocation that can never reach a bucket, i.e. a tier
-       that reports Ready-ish while backups silently do not exist. Set the real prod endpoint first." ;;
-    *) info "resuming velero"; flux resume kustomization velero --timeout=1s >/dev/null 2>&1 || true
-       wait_ready velero 900 || warn "velero did not converge" ;;
-  esac
+       that reports Ready-ish while backups silently do not exist. Set the real endpoint first, prove
+       it with \`s3check\`, and only then resume (infra/BACKUP-R2.md)."
+  else
+    info "resuming velero"; flux resume kustomization velero --timeout=1s >/dev/null 2>&1 || true
+    wait_ready velero 900 || warn "velero did not converge"
+  fi
 }
 
 step_verify() {
diff --git a/infra/BACKUP-R2.md b/infra/BACKUP-R2.md
new file mode 100644
index 0000000..acb58cc
--- /dev/null
+++ b/infra/BACKUP-R2.md
@@ -0,0 +1,315 @@
+# Off-cluster backup on Cloudflare R2 — operator procedure
+
+**Owner:** WS-BACKUP · **Serves:** R-STATE-03 (DR restore), R-IDP-05 (Keycloak DB), R-ENV-02 (one
+environment-agnostic path) · **Status:** authored and staged, **NOT switched on**.
+
+> **Read this first.** Velero-against-R2 and CNPG/barman-against-R2 are **UNPROVEN in this repo**.
+> Nothing here claims they work. What *is* proven is in [§7](#7-what-is-proven-and-what-is-not).
+> R-STATE-03 is currently PROVEN **against MinIO only** and must be re-proven against R2 before this
+> migration can be called done.
+
+## Why R2 at all
+
+The off-cluster target used to be a MinIO on the Proxmox host (`http://192.168.1.9:9000`). Two things
+killed it, both recorded on 2026-09-05:
+
+1. **Prod physically cannot reach it.** Prod is on the SOHO network `192.168.2.0/24`, which is
+   pfSense's **WAN**; the MinIO sits inside pfSense's LAN `192.168.1.0/24`. Measured *from a pod inside
+   prod* — the workstation's own reachability proves nothing about pod egress and has misled this
+   project once already — `curl http://192.168.1.9:9000/minio/health/live` timed out after 15 s.
+   Reaching it would need a WAN→LAN rule that does not exist.
+2. **Dev's "off-cluster" backup was not off-cluster.** That MinIO runs on the *same Proxmox host* as
+   dev's VMs, so it shared a failure domain with the thing it was backing up.
+
+R2 needs no firewall change, is genuinely off-site, and is already trusted with the OpenTofu remote
+state (`infra/tofu/REMOTE-STATE.md`) — the same account, the same kind of token. It is explicitly an
+interim decision: *"that's where backups will go for the time being until a better on-prem backup
+solution is created."*
+
+---
+
+## 1. Cloudflare: buckets, token, account id
+
+All of this is in the Cloudflare dashboard; none of it touches the cluster.
+
+1. **R2 → Create bucket** → `velero`. Location hint: whatever is nearest; jurisdiction default.
+2. **R2 → Create bucket** → `cnpg`.
+   Both names are fixed by the manifests: `bucket: velero` in `platform/velero/helmrelease.yaml`, and
+   `cnpg` via `CNPG_BACKUP_PATH` (`s3://cnpg/dev`, `s3://cnpg/prod`). Use exactly those names or change
+   the manifests — do not improvise.
+3. **R2 → Manage API Tokens → Create API Token**
+   - Permission: **Object Read & Write** (not "Admin Read & Write" — the cluster never needs to create
+     or delete buckets, and a token that can is a token that can delete your backups).
+   - **Specify bucket(s):** `velero` **and** `cnpg`. One token scoped to both — the manifests already
+     assume one shared key, and `s3check` proves both buckets with it.
+   - Copy the **Access Key ID** and **Secret Access Key**. They are shown **once**. Put them in the
+     password manager before you do anything else.
+4. **Account id** — 32 hex characters, visible in the dashboard URL and in the R2 S3 endpoint the
+   token page shows you.
+
+   **This repo already knows it.** `infra/tofu/backend.r2.hcl` commits
+   `https://7ce452a1b3d6c86daf2c020edcb82d37.r2.cloudflarestorage.com` for the OpenTofu state bucket,
+   with the (correct) note that an account id is not a credential. **If the backup buckets live in the
+   same Cloudflare account as the tofu state — they should; there is no reason for a second account —
+   then the endpoint is already known and you do not need to look anything up:**
+
+   ```
+   https://7ce452a1b3d6c86daf2c020edcb82d37.r2.cloudflarestorage.com
+   ```
+
+   Confirm it matches the endpoint on the token page. If it does not, you have two accounts and the
+   `velero`/`cnpg` buckets are in the other one — use that one's id, and say so in the DECISIONS-LOG.
+
+The endpoint form is always `https://<account-id>.r2.cloudflarestorage.com` — **no bucket in the
+hostname** (path-style; see [§6](#6-r2-specific-gotchas)).
+
+---
+
+## 2. Repo values to set
+
+Only **one** non-secret value is missing, and it is not in a secret file:
+
+| File | Key | From | To |
+|---|---|---|---|
+| `clusters/base/cluster-vars.yaml` | `S3_BACKUP_ENDPOINT` | `https://TBD-R2-ACCOUNT-ID.r2.cloudflarestorage.com` | `https://<account-id>.r2.cloudflarestorage.com` |
+
+Already authored, **do not change**: `S3_BACKUP_REGION: "auto"`, `VELERO_BACKUP_PREFIX` (dev `dev` /
+prod `prod`), `CNPG_BACKUP_PATH` (`s3://cnpg/dev` / `s3://cnpg/prod`), and `checksumAlgorithm: ""` on
+the Velero BackupStorageLocation.
+
+The placeholder is deliberately loud, and the guards match it as a **substring** — `bootstrap/standup.sh`
+refuses to probe it and refuses to resume `velero` while it is there.
+
+---
+
+## 3. Credentials: four Secrets, one command
+
+The R2 key is read by **four** committed SOPS Secrets, in **two** different shapes. No manifest changes
+are needed — only the encrypted values change:
+
+| File | Consumer | Shape |
+|---|---|---|
+| `platform/velero/velero-cloud.sops.yaml` | Velero (`velero-cloud-credentials`, ns `velero`) | `stringData.cloud` — an **AWS INI file**: `[default]` + `aws_access_key_id=` / `aws_secret_access_key=` |
+| `platform/keycloak/keycloak-db-backup-credentials.sops.yaml` | CNPG `keycloak-db` (ns `keycloak`) | `ACCESS_KEY_ID` / `ACCESS_SECRET_KEY` |
+| `apps/wave-0/nextcloud-db-backup-credentials.sops.yaml` | CNPG `nextcloud-db` | `ACCESS_KEY_ID` / `ACCESS_SECRET_KEY` |
+| `apps/wave-0/semaphore-db-backup-credentials.sops.yaml` | CNPG `semaphore-db` | `ACCESS_KEY_ID` / `ACCESS_SECRET_KEY` |
+
+A Secret is namespace-scoped and a Pod reads only its own namespace's, which is why there are four
+copies of one key rather than one.
+
+### The one command
+
+```bash
+./infra/devcontainer/dev.sh run platform/backup/set-r2-credentials.sh
+```
+
+It prompts for the two values (never echoed, never in shell history, never written to a file), writes
+them into all four Secrets with `sops set` — which encrypts in place, so **no decrypted copy of any
+Secret is ever created** — then decrypts each file back and proves all four now hold the same key by
+comparing 32-bit fingerprints. It never prints a credential.
+
+There is deliberately **no plaintext template to fill in and encrypt**. The
+`cp x.example x.yaml && $EDITOR && sops -e -i` pattern leaves a plaintext Kubernetes Secret sitting in
+the working tree, one `git add -A` away from being in git forever; `sops set` removes that window
+entirely. If you would rather edit by hand, `sops platform/velero/velero-cloud.sops.yaml` decrypts to
+`$EDITOR` and re-encrypts on save — also with no plaintext on disk — but then you must repeat it four
+times and keep them identical yourself.
+
+To check the four files agree without changing anything:
+
+```bash
+./infra/devcontainer/dev.sh run platform/backup/set-r2-credentials.sh --check
+```
+
+### What is NOT changed
+
+`platform/backup/minio-credentials.sops.yaml` keeps the **MinIO** key. That is not an oversight — it
+is what you need to read the pre-migration backups ([§8](#8-going-back-to-minio)). Its
+`.yaml.example` sibling documents the MinIO shape and stays accurate for the MinIO target.
+
+Review the diff before committing: you should see **only** `ENC[...]` blobs and `lastmodified`/`mac`
+change in four files. If a key name or a `metadata.name` moved, stop.
+
+---
+
+## 4. Prove the target BEFORE merging
+
+```bash
+K=infra/ansible/.cache/dev.kubeconfig        # or prod.kubeconfig
+./infra/devcontainer/dev.sh run bootstrap/standup.sh \
+  --kubeconfig $K --expect-server https://192.168.2.50:6443 \
+  --s3-endpoint https://<account-id>.r2.cloudflarestorage.com s3check
+```
+
+`--s3-endpoint` probes a **candidate** endpoint instead of the live `cluster-vars` value, so the target
+is proven before it is authored. Run it against **both** clusters — prod's egress is the whole reason
+this migration exists, and it is a different network position from dev's.
+
+`s3check` runs a throwaway pod per credential and, for each, proves:
+
+1. the committed credential **loads and authenticates**, in the exact shape its consumer reads it
+   (Velero's INI file mounted from the `cloud` key; CNPG's discrete `ACCESS_KEY_ID`/`ACCESS_SECRET_KEY`);
+2. the bucket **exists and is listable** under this environment's own prefix (`ListObjectsV2`, the
+   operation Velero's BSL sync and Barman's WAL scan both perform);
+3. **PUT → GET → byte-compare (sha256 + length) → DELETE → confirm-gone** of one throwaway object at
+   `<prefix>/.s3check/<pod>.probe` — a genuine write, not a HEAD. A HEAD passes with a read-only token
+   and with R2 rejecting every write;
+4. whether the **R2 checksum trap** ([§6](#6-r2-specific-gotchas)) is present, probed on purpose by
+   repeating the PUT with checksums *enabled*, and named explicitly either way.
+
+It **fails closed**: a pod that cannot be created, an empty log, a missing verdict line, a short
+assertion count, an OK-line count that disagrees with the claimed count, or any single failed
+assertion all exit non-zero. There is no "reachability unknown, carrying on". Each failure names its
+own cause and fix — wrong key, unscoped token, missing bucket, no pod egress, checksum rejection.
+
+It writes and deletes exactly one object per bucket and leaves no pod behind. It applies nothing and
+does not enable `velero`.
+
+---
+
+## 5. The verification sequence — and it ends in a RESTORE
+
+**A backup that has never been restored is not a backup.** R-STATE-03 is PROVEN against MinIO; that
+proof does not transfer to a different object store with a different S3 implementation.
+
+1. **`s3check` on dev, then on prod.** Both must pass. (§4)
+2. Merge the endpoint + the four re-encrypted Secrets. Let Flux reconcile.
+3. **Resume `velero`** — `bootstrap/standup.sh … resume` does it once the endpoint is no longer a
+   placeholder, or `flux resume kustomization velero`.
+4. `velero backup-location get` → `default` **Available**. *Available only means the BSL could be
+   read;* it is not a backup.
+5. `velero backup create --from-schedule daily` → wait for **Completed**, then
+   `velero backup logs <name>`. Watch specifically for `PodVolumeBackup` failures: the PVC-data path
+   is kopia, a **different S3 client** from the one the BSL uses (see §7), so metadata can succeed
+   while volume data fails.
+6. **Restore.** `velero restore create --from-backup <name> --include-namespaces <scratch-ns>` into a
+   *scratch* namespace, and verify the PVC contents actually arrived — not just that the Restore says
+   Completed. This is the R-STATE-03 re-proof.
+7. **CNPG PITR.** Confirm WAL is arriving:
+   `kubectl -n keycloak get cluster keycloak-db -o jsonpath='{.status.conditions}'` (look for
+   `ContinuousArchiving`), and that objects exist under `s3://cnpg/<env>/keycloak-db/`. Then do the
+   restore that matters: a `Cluster` with `bootstrap.recovery` from the barman object store into a
+   scratch namespace, and check the recovered database actually contains data. The existing
+   `conformance/tests/l2-behavioral/keycloak-db-dr` and `l3-fault-injection/dr-restore` tests are the
+   harness for this; they must be re-run **against R2**, and their previous PROVEN state records MinIO,
+   not R2.
+8. Only after 6 and 7 pass may this migration be described as done, and the ledger updated. Until
+   then the honest status is "R2 accepts objects; recovery from R2 is untested".
+
+---
+
+## 6. R2-specific gotchas
+
+**`region: auto`.** R2 accepts nothing else, and S3 clients require *some* region. Authored as
+`S3_BACKUP_REGION: "auto"`. This repo already learned it — `infra/tofu/backend.tf` carries
+`region = "auto"  # R2 ignores region, but the S3 backend requires a value.`
+
+**`checksumAlgorithm: ""` — do not delete this line.** `velero-plugin-for-aws`'s own
+`backupstoragelocation.md` for **v1.14.2** (the pinned version) documents:
+
+> `checksumAlgorithm` — The checksum algorithm to use for uploading objects to S3. Supported values
+> "CRC32", "CRC32C", "SHA1", "SHA256". If the value is set as empty string "", no checksum will be
+> calculated and attached to the request headers. **Optional (defaults to "CRC32")**
+
+So *omitting* the key means CRC32 **is** sent: `x-amz-sdk-checksum-algorithm` +
+`x-amz-checksum-crc32`. This repo has already measured that R2 rejects AWS checksums — that is exactly
+why `infra/tofu/backend.tf` needs `skip_s3_checksum = true  # R2 rejects AWS trailing (streaming)
+checksums.` for the state bucket. The plugin's own compatibility table lists `checksumAlgorithm=""` as
+the remedy for the same failure on Ceph S3, Backblaze B2 and IBM COS. If backups start failing with
+**HTTP 400 `InvalidArgument`** after a plugin bump, look here first. `s3check` probes for this on
+purpose and names it.
+
+**Path-style.** `s3ForcePathStyle: "true"` is authored and correct for R2 as well as MinIO. Never put
+the bucket in the hostname.
+
+**No bucket auto-creation.** Velero does not create buckets and the token deliberately cannot. A
+missing bucket is a `NoSuchBucket` at runtime; `s3check` catches it first.
+
+**Token scope is per-bucket.** A token scoped only to `velero` authenticates fine and then 403s on
+`cnpg` — the two consumers fail independently and quietly. `s3check` proves both.
+
+**Both clusters share one endpoint.** Isolation is by path only (`VELERO_BACKUP_PREFIX`,
+`CNPG_BACKUP_PATH`), because R2 is one environment-independent URL. Those two knobs are load-bearing:
+without them prod would adopt and TTL-delete dev's Velero backups, and both clusters' identically-named
+CNPG Clusters would interleave their WAL into one Barman stream, destroying PITR for both.
+
+---
+
+## 7. What is proven, and what is not
+
+**Proven (2026-09-05, WS-BACKUP, against the live dev cluster and its MinIO at
+`http://192.168.1.9:9000`):**
+
+- the rewritten `s3check` itself: 7 assertions per credential path, both credential shapes, from
+  in-cluster pods — credential load, bucket list, PUT/GET/byte-compare/DELETE/confirm-gone, no object
+  and no pod left behind;
+- its failure paths: the `TBD` placeholder is refused; an unreachable endpoint (`:9099`) produces a
+  named no-egress failure and exit 1, not a pass;
+- MinIO accepts a checksum-bearing PUT, i.e. the trap is a *non-*MinIO problem, and
+  `checksumAlgorithm: ""` is harmless there.
+
+**Established from the pinned versions (documentation and image inspection, not measured against R2):**
+
+- `velero-plugin-for-aws` **v1.14.2** pairs with Velero **v1.18.x** (upstream compatibility table) and
+  defaults `checksumAlgorithm` to `CRC32` — so the authored `""` is load-bearing, not decoration.
+- That plugin's "Non-AWS S3 compatible provider known issues with plugin v1.14.x" table **does not
+  mention Cloudflare R2 at all** — neither as working nor as broken. There is no upstream statement to
+  lean on in either direction.
+- **The PVC-data path is a different S3 client.** `checksumAlgorithm` is a BackupStorageLocation
+  *object-store plugin* setting. Velero's File System Backup uploads through the unified repository's
+  kopia S3 backend (`pkg/repository/udmrepo/kopialib/backend/s3.go` in Velero v1.18.0), which
+  references only endpoint/region-style options and has **no checksum knob at all**. So R2
+  compatibility for backup *metadata* and for *volume data* are two separate questions, and only step
+  5 of §5 answers the second.
+- **CNPG/barman is likely clear of the checksum trap, by version.** Inspected inside the live
+  `ghcr.io/cloudnative-pg/postgresql:16.4` image on dev: `barman-cloud-wal-archive 3.11.1`,
+  `botocore 1.35.60`, `boto3 1.35.60`. That botocore predates the 1.36 line in which botocore began
+  attaching CRC32 request checksums by default (the change that introduced
+  `AWS_REQUEST_CHECKSUM_CALCULATION`), so this image should not send them.
+  **Forward risk:** barman-cloud exposes **no** `checksumAlgorithm` equivalent. If the CNPG image is
+  ever bumped to one carrying botocore ≥ 1.36, WAL archiving to R2 could start failing with 400
+  `InvalidArgument` and there is no config knob to turn it off — only `AWS_REQUEST_CHECKSUM_CALCULATION=when_required`
+  in the Pod environment, which CNPG does not currently set. Treat a CNPG image bump as a change that
+  must be re-verified against R2.
+
+**Not proven, at all:**
+
+- that Velero can write a usable backup to R2 (metadata or kopia volume data);
+- that CNPG/barman can archive WAL to R2 and that a `bootstrap.recovery` from R2 succeeds;
+- that a restore from R2 yields correct data. R-STATE-03's PROVEN state is **MinIO-only**.
+
+---
+
+## 8. Going back to MinIO
+
+The MinIO copy is **not deleted** and stays restorable. To read pre-migration backups:
+
+1. `clusters/base/cluster-vars.yaml` → `S3_BACKUP_ENDPOINT: "http://192.168.1.9:9000"`
+2. `VELERO_BACKUP_PREFIX` → `""` (the MinIO backups are at the **bucket root**, not under `dev/`) and
+   `CNPG_BACKUP_PATH` → `s3://cnpg` (Barman objects are at `s3://cnpg/<clusterName>/`).
+3. Restore the MinIO credential into the four Secrets. `platform/backup/minio-credentials.sops.yaml`
+   still holds it: `sops -d --extract '["stringData"]["ACCESS_KEY_ID"]'` it and feed the two values to
+   `platform/backup/set-r2-credentials.sh` (the script cares about the *shape*, not the provider).
+4. `S3_BACKUP_REGION` may stay `auto` — MinIO ignores the region.
+5. **Dev only.** Prod cannot reach that MinIO at all (§Why R2); pointing prod back is not an option.
+
+Reverting for a restore and then returning to R2 costs another PITR reset. Prefer restoring from MinIO
+into a *scratch* namespace on dev with a second, temporary BackupStorageLocation over flipping the
+whole cluster's endpoint back and forth.
+
+---
+
+## 9. Merging this resets dev's PITR window
+
+Say it out loud before merging, because it is not recoverable by retrying:
+
+- Dev's R2 prefix starts **empty**. Velero writes a **fresh kopia repository** — the first backup is a
+  full upload of every included PVC, and no earlier restore point exists in R2.
+- Every CNPG Cluster takes **new base backups** (`ScheduledBackup … immediate: true`), and the 30-day
+  Barman retention window (`retentionPolicy: "30d"`) rebuilds **from zero**. For roughly a month, dev's
+  point-in-time recovery reaches back only as far as the merge.
+- The MinIO copy still holds the old window (§8), but reaching it means reverting the endpoint — so it
+  is a deliberate excursion, not a fallback that happens automatically.
+
+**Do not merge this while dev's proven MinIO restore is the only recovery path you are relying on.**
+The same applies to prod the day it first backs up anywhere.
diff --git a/platform/backup/minio-credentials.sops.yaml.example b/platform/backup/minio-credentials.sops.yaml.example
index b883a20..a7f950d 100644
--- a/platform/backup/minio-credentials.sops.yaml.example
+++ b/platform/backup/minio-credentials.sops.yaml.example
@@ -2,6 +2,20 @@
 # TEMPLATE — NOT APPLIED, NOT ENCRYPTED (.yaml.example is ignored by kustomize and never
 # auto-encrypted by SOPS). Reference scaffold + OPERATOR HAND-OFF.
 #
+# *** SUPERSEDED AS THE LIVE TARGET (2026-09-05), RETAINED ON PURPOSE. ***
+# Off-cluster DR moved to Cloudflare R2: prod physically cannot reach this MinIO (prod is on the SOHO
+# net 192.168.2.0/24, pfSense's WAN; the MinIO is inside pfSense's LAN — measured from a pod inside
+# prod: timed out), and this MinIO runs on the SAME Proxmox host as dev's VMs, so dev's "off-cluster"
+# backup shared a failure domain with dev. The R2 procedure is infra/BACKUP-R2.md.
+#
+# This file and its encrypted sibling minio-credentials.sops.yaml are KEPT because the MinIO copy of
+# the backups is NOT deleted and stays restorable: this is the key that reads the pre-migration
+# backups. Do NOT overwrite it with the R2 key — infra/BACKUP-R2.md §8 is how you point back here.
+#
+# DO NOT hand-fill this for R2. Four Secrets in three namespaces hold that one key, and
+# platform/backup/set-r2-credentials.sh writes all four with `sops set` — encrypted in place, so no
+# plaintext Secret ever exists in the working tree to be committed by accident.
+#
 # WHAT THIS IS: the scoped (non-root) MinIO S3 access key for the off-cluster backup target that
 # roles/minio_backup_target stands up on the Proxmox host (playbooks/backup-minio.yml). It is the
 # credential Velero (R-STATE-03) and CloudNativePG / Barman (R-IDP-05) use to write backups. The
diff --git a/platform/backup/set-r2-credentials.sh b/platform/backup/set-r2-credentials.sh
new file mode 100755
index 0000000..339e464
--- /dev/null
+++ b/platform/backup/set-r2-credentials.sh
@@ -0,0 +1,195 @@
+#!/usr/bin/env bash
+#
+# set-r2-credentials.sh — put ONE Cloudflare R2 API token into every credential Secret that consumes
+# the off-cluster backup target, without plaintext ever touching the disk.
+#
+# WHY THIS EXISTS
+#   The same S3 key is read by four different Secrets in three namespaces, in TWO different shapes
+#   (Velero wants an AWS INI file; CNPG/barman wants discrete ACCESS_KEY_ID / ACCESS_SECRET_KEY keys).
+#   Hand-editing four SOPS files is four chances to typo one of them — and a typo'd backup credential
+#   does not fail at apply time, it fails at 03:00 with no backup and a green HelmRelease.
+#
+#   It uses `sops set`, which edits an ALREADY-ENCRYPTED file in place: the new value is encrypted as
+#   it is written and NO decrypted copy of the file is ever created. That is the whole point — the
+#   `cp template plaintext.yaml && edit && sops -e -i` dance leaves a plaintext Secret sitting in the
+#   working tree, one `git add -A` away from being committed forever.
+#
+# USAGE (inside the dev container — it has sops and mounts the age key)
+#   ./infra/devcontainer/dev.sh run platform/backup/set-r2-credentials.sh
+#     → prompts for the two values (never echoed, never in shell history, never in a file)
+#
+#   ./infra/devcontainer/dev.sh run platform/backup/set-r2-credentials.sh --check
+#     → touches nothing; just reports whether the four Secrets already agree with each other
+#
+#   R2_ACCESS_KEY_ID=… R2_SECRET_ACCESS_KEY=… …/set-r2-credentials.sh --no-prompt
+#     → non-interactive. Prefer the prompts: an env var is visible in /proc and in `history`.
+#
+# WHAT IT DOES NOT DO
+#   - It does not touch clusters/base/cluster-vars.yaml. The endpoint is not a secret and belongs in
+#     a reviewable plain manifest; the script prints the exact edit to make.
+#   - It does not commit. Review `git diff` (you will see only ENC[...] blobs change) and commit.
+#   - It does not delete or rewrite platform/backup/minio-credentials.sops.yaml. That is the RETAINED
+#     pre-migration MinIO key and it is what you need to read the pre-migration backups.
+#
+# SEE  infra/BACKUP-R2.md for the whole procedure, including the restore that actually proves it.
+set -euo pipefail
+
+# Belt and braces: never let a stray `set -x` in a parent shell echo a credential out of this script.
+set +x
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+root="$(git -C "${here}" rev-parse --show-toplevel 2>/dev/null || (cd "${here}/.." && pwd))"
+cd "${root}"
+
+MODE=set
+PROMPT=1
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --check)     MODE=check; shift ;;
+    --no-prompt) PROMPT=0; shift ;;
+    -h|--help)   sed -n '2,40p' "${BASH_SOURCE[0]}"; exit 0 ;;
+    *)           echo "ERROR: unknown argument '$1'" >&2; exit 2 ;;
+  esac
+done
+
+die()  { printf '\033[31mERROR: %s\033[0m\n' "$*" >&2; exit 1; }
+say()  { printf '\n\033[1m==> %s\033[0m\n' "$*"; }
+info() { printf '    %s\n' "$*"; }
+warn() { printf '\033[33mWARN: %s\033[0m\n' "$*" >&2; }
+
+command -v sops >/dev/null 2>&1 || die "'sops' not found — run this inside ./infra/devcontainer/dev.sh."
+
+# ---------------------------------------------------------------- the consumers
+# file|shape.  shape=ini   -> stringData.cloud, an AWS INI credentials file (velero-plugin-for-aws)
+#              shape=discrete -> stringData.ACCESS_KEY_ID + ACCESS_SECRET_KEY (CNPG barmanObjectStore)
+CONSUMERS=(
+  "platform/velero/velero-cloud.sops.yaml|ini"
+  "platform/keycloak/keycloak-db-backup-credentials.sops.yaml|discrete"
+  "apps/wave-0/nextcloud-db-backup-credentials.sops.yaml|discrete"
+  "apps/wave-0/semaphore-db-backup-credentials.sops.yaml|discrete"
+)
+
+for entry in "${CONSUMERS[@]}"; do
+  f="${entry%%|*}"
+  [ -f "${f}" ] || die "missing consumer file ${f} — has the layout changed? Fix this script, do not skip the file."
+  grep -q '^sops:' "${f}" || die "${f} has no top-level sops: block — refusing to touch a file that is not SOPS-encrypted."
+done
+
+# A 32-bit fingerprint of a high-entropy secret: enough to prove two files hold the SAME value,
+# nowhere near enough to recover it. Values themselves are NEVER printed.
+fp() { local h; h="$(printf '%s' "$1" | sha256sum)"; printf '%s' "${h:0:8}"; }
+
+# Read one value out of an encrypted file without ever writing plaintext anywhere.
+xtract() { sops -d --extract "$2" "$1"; }
+
+# Pull the two values out of an AWS INI blob using shell only.
+ini_field() { # <ini-text> <aws_access_key_id|aws_secret_access_key>
+  local line v=""
+  while IFS= read -r line; do
+    case "${line}" in
+      "$2"=*|"$2 "*|*[![:alnum:]_]"$2"=*) v="${line#*=}"; v="${v#"${v%%[![:space:]]*}"}" ;;
+    esac
+  done <<<"$1"
+  printf '%s' "${v}"
+}
+
+report() { # print the fingerprint table; returns non-zero when the four files disagree
+  local entry f shape id sec akid_fp sec_fp first_id="" first_sec="" agree=0
+  printf '    %-58s %-10s %-10s\n' FILE ID-FP SECRET-FP
+  for entry in "${CONSUMERS[@]}"; do
+    f="${entry%%|*}"; shape="${entry##*|}"
+    if [ "${shape}" = ini ]; then
+      local blob; blob="$(xtract "${f}" '["stringData"]["cloud"]' 2>/dev/null || true)"
+      id="$(ini_field "${blob}" aws_access_key_id)"
+      sec="$(ini_field "${blob}" aws_secret_access_key)"
+      blob=""
+    else
+      id="$(xtract "${f}" '["stringData"]["ACCESS_KEY_ID"]' 2>/dev/null || true)"
+      sec="$(xtract "${f}" '["stringData"]["ACCESS_SECRET_KEY"]' 2>/dev/null || true)"
+    fi
+    [ -n "${id}" ]  || { warn "${f}: could not read the access key id (age key available?)"; agree=1; }
+    [ -n "${sec}" ] || { warn "${f}: could not read the secret access key"; agree=1; }
+    akid_fp="$(fp "${id}")"; sec_fp="$(fp "${sec}")"
+    printf '    %-58s %-10s %-10s\n' "${f}" "${akid_fp}" "${sec_fp}"
+    if [ -z "${first_id}" ]; then first_id="${akid_fp}"; first_sec="${sec_fp}"
+    elif [ "${akid_fp}" != "${first_id}" ] || [ "${sec_fp}" != "${first_sec}" ]; then agree=1; fi
+    id=""; sec=""
+  done
+  return "${agree}"
+}
+
+if [ "${MODE}" = check ]; then
+  say "current state of the four backup credential Secrets (values never printed)"
+  if report; then
+    info "ALL FOUR AGREE. (Agreeing is not the same as being right — prove it with bootstrap/standup.sh s3check.)"
+    exit 0
+  fi
+  die "the four Secrets do NOT all hold the same key. Velero and CNPG would be writing to the same
+       target with different credentials — one of them is stale. Re-run this script without --check."
+fi
+
+# ---------------------------------------------------------------- the two values
+AKID="${R2_ACCESS_KEY_ID-}"
+SAK="${R2_SECRET_ACCESS_KEY-}"
+if [ "${PROMPT}" = 1 ]; then
+  say "paste the R2 API token (Cloudflare dashboard -> R2 -> Manage API Tokens)"
+  info "Object Read & Write, scoped to the velero + cnpg buckets. Neither value is echoed or stored."
+  [ -n "${AKID}" ] || { printf '    Access Key ID: ';     IFS= read -rs AKID; printf '\n'; }
+  [ -n "${SAK}" ]  || { printf '    Secret Access Key: '; IFS= read -rs SAK;  printf '\n'; }
+fi
+[ -n "${AKID}" ] || die "no access key id given (prompt, or R2_ACCESS_KEY_ID with --no-prompt)."
+[ -n "${SAK}" ]  || die "no secret access key given (prompt, or R2_SECRET_ACCESS_KEY with --no-prompt)."
+
+# FAIL CLOSED on anything that is not a plain S3 credential. These values are passed to `sops set` as
+# JSON, so a quote, a backslash or a newline would corrupt the Secret rather than error — and the
+# usual cause is a copy-paste that swallowed a newline or a trailing space, which would produce a
+# credential that authenticates nowhere and a backup that silently never runs.
+for pair in "access key id:${AKID}" "secret access key:${SAK}"; do
+  case "${pair#*:}" in
+    *[!A-Za-z0-9._~+/=-]*) die "the ${pair%%:*} contains a character outside [A-Za-z0-9._~+/=-].
+       Almost certainly a stray space, quote or newline from the paste. Nothing was changed." ;;
+  esac
+done
+# R2 issues 32-hex ids and 64-hex secrets today. A mismatch is a warning, not a refusal: the format is
+# Cloudflare's to change, and refusing outright would make this script the thing that blocks a rotation.
+case "${AKID}" in *[!0-9a-f]*|"") warn "the access key id is not 32 lowercase hex chars — unusual for R2. Continuing." ;;
+  *) [ "${#AKID}" = 32 ] || warn "the access key id is ${#AKID} chars, not the usual 32. Continuing." ;;
+esac
+[ "${#SAK}" -ge 40 ] || warn "the secret access key is only ${#SAK} chars — unusual for R2 (64). Continuing."
+
+# ---------------------------------------------------------------- write
+say "writing the credential into ${#CONSUMERS[@]} SOPS Secrets (encrypted in place; no plaintext file)"
+for entry in "${CONSUMERS[@]}"; do
+  f="${entry%%|*}"; shape="${entry##*|}"
+  case "${shape}" in
+    ini)
+      # velero-plugin-for-aws reads this key VERBATIM as an AWS credentials file. The [default]
+      # profile name and the two underscore_names are the plugin's contract, not a style choice.
+      sops set "${f}" '["stringData"]["cloud"]' \
+        "\"[default]\\naws_access_key_id=${AKID}\\naws_secret_access_key=${SAK}\\n\"" ;;
+    discrete)
+      sops set "${f}" '["stringData"]["ACCESS_KEY_ID"]'     "\"${AKID}\""
+      sops set "${f}" '["stringData"]["ACCESS_SECRET_KEY"]' "\"${SAK}\"" ;;
+  esac
+  info "updated ${f}"
+done
+AKID_FP="$(fp "${AKID}")"; SAK_FP="$(fp "${SAK}")"
+AKID=""; SAK=""
+
+say "verifying by decrypting each file back (values never printed)"
+report || die "the files still disagree after writing — do NOT commit. Inspect with 'sops <file>'."
+info "every file now reads id-fp=${AKID_FP} secret-fp=${SAK_FP} — matching what was pasted."
+
+say "NEXT — in this order, and do not skip the restore"
+cat <<'NEXT'
+    1. Set the endpoint (NOT a secret, so it lives in a plain reviewable manifest):
+         clusters/base/cluster-vars.yaml
+           S3_BACKUP_ENDPOINT: "https://<account-id>.r2.cloudflarestorage.com"
+           S3_BACKUP_REGION:   "auto"          # R2 accepts nothing else
+    2. Prove the target BEFORE merging anything (writes and deletes one throwaway object):
+         bootstrap/standup.sh --kubeconfig <kc> --expect-server <url> \
+           --s3-endpoint https://<account-id>.r2.cloudflarestorage.com s3check
+    3. Only then commit + merge, and follow infra/BACKUP-R2.md through the RESTORE.
+       A backup that has never been restored is not a backup, and R-STATE-03 is currently PROVEN
+       against MinIO only.
+NEXT
diff --git a/platform/velero/README.md b/platform/velero/README.md
index 431d347..2222684 100644
--- a/platform/velero/README.md
+++ b/platform/velero/README.md
@@ -9,17 +9,43 @@
 
 ## What this is (LIVE)
 
-Flux `HelmRelease` (Velero chart 12.x / Velero 1.18.x) wired to the on-Proxmox **MinIO** S3 target:
+Flux `HelmRelease` (Velero chart 12.x / Velero 1.18.x) wired to whatever `${S3_BACKUP_ENDPOINT}` names.
+The target is a **cluster-vars knob, not a constant**:
 
-- **Endpoint:** `http://192.168.1.9:9000` (plain HTTP, **path-style**, region `us-east-1` placeholder)
-- **BucketStorageLocation `default`:** provider `aws`, bucket `velero`, `s3ForcePathStyle=true`.
-- **AWS plugin** (`velero/velero-plugin-for-aws`) loaded as an init container.
+- **Endpoint:** `${S3_BACKUP_ENDPOINT}` — dev has been running against the on-Proxmox **MinIO**
+  `http://192.168.1.9:9000`; as of **2026-09-05** the authored target is **Cloudflare R2**
+  (`https://<account-id>.r2.cloudflarestorage.com`). The switch-on procedure, the R2 gotchas and the
+  honest proven/unproven split all live in **[`infra/BACKUP-R2.md`](../../infra/BACKUP-R2.md)**.
+  Always **path-style**; region `${S3_BACKUP_REGION}` (MinIO ignores it, R2 requires exactly `auto`).
+- **BucketStorageLocation `default`:** provider `aws`, bucket `velero`, prefix
+  `${VELERO_BACKUP_PREFIX}` (dev/prod — both clusters share one R2 endpoint and are isolated by path
+  only), `s3ForcePathStyle=true`, **`checksumAlgorithm: ""`**.
+  That last one is load-bearing: `velero-plugin-for-aws` v1.14.2 defaults it to `CRC32` and R2 rejects
+  AWS checksums with HTTP 400 `InvalidArgument`. Do not remove it, and re-check it on every plugin bump.
+- **AWS plugin** (`velero/velero-plugin-for-aws:v1.14.2`) loaded as an init container.
 - **File System Backup (kopia):** `deployNodeAgent=true`, `uploaderType=kopia`, `snapshotsEnabled=false`
-  — storage-agnostic PVC backup, **no** CSI snapshot / data-mover.
+  — storage-agnostic PVC backup, **no** CSI snapshot / data-mover. This path uploads through kopia's
+  **own** S3 client, which does not read `checksumAlgorithm`: metadata compatibility and volume-data
+  compatibility with a given object store are two separate questions.
 - **Credentials:** `velero-cloud-credentials` — a SOPS Secret (`velero-cloud.sops.yaml`) holding the
-  `cloud` INI key, the **scoped** MinIO key limited to the `velero`+`cnpg` buckets. Kept in sync with
-  the staging source of truth `platform/backup/minio-credentials.sops.yaml` and the Proxmox host
-  ansible-vault.
+  `cloud` INI key, the **scoped** key limited to the `velero`+`cnpg` buckets. Four Secrets across three
+  namespaces hold this one key; `platform/backup/set-r2-credentials.sh` writes all four at once with
+  `sops set` (no plaintext ever on disk) and proves they agree.
+  `platform/backup/minio-credentials.sops.yaml` retains the **pre-migration MinIO** key — that is
+  deliberate, it is how the pre-migration backups stay readable.
+
+## Proving the target before trusting it
+
+```bash
+bootstrap/standup.sh --kubeconfig <kc> --expect-server <url> \
+  [--s3-endpoint <candidate>] s3check
+```
+
+`s3check` runs a throwaway in-cluster pod per credential and proves credential load + authentication,
+bucket existence and listability under this environment's prefix, and a real
+**PUT → GET → byte-compare → DELETE → confirm-gone** round trip — plus whether the R2 checksum trap is
+present. It fails closed and loud; it never reports "unknown, carrying on". Pod egress is the only
+reading that counts (prod sits on pfSense's WAN, the MinIO inside its LAN).
 
 Reconciled by its **own non-gating** Flux Kustomization `clusters/base/backup.yaml`
 (`dependsOn: platform-config`, `wait:false`) — a backup controller must never gate the platform graph.
@@ -46,7 +72,13 @@ PITR to the `cnpg` bucket — see the DB manifests.)
 
 ## Post-deploy (PM)
 
-- `velero backup-location get` → `default` Available.
-- `velero backup create --from-schedule daily` → objects land under `s3://velero/`.
+- `velero backup-location get` → `default` Available. **Available only means the BSL could be read.**
+- `velero backup create --from-schedule daily` → Completed, then read `velero backup logs <name>` and
+  look for `PodVolumeBackup` failures specifically (see the kopia note above). Objects land under
+  `s3://velero/${VELERO_BACKUP_PREFIX}/`.
 - DR drill (R-STATE-03, Phase-4 gate): `velero restore create --from-backup <name>` into a scratch
   namespace and verify PVC data restores via the node-agent.
+
+**R-STATE-03 is PROVEN against MinIO only.** A restore from R2 has never been executed in this repo,
+and Velero-against-R2 is unproven here — `infra/BACKUP-R2.md` §5 is the re-proof sequence and §7 is the
+honest list of what is and is not established.
diff --git a/platform/velero/kustomization.yaml b/platform/velero/kustomization.yaml
index bfd99ae..c4ae3cd 100644
--- a/platform/velero/kustomization.yaml
+++ b/platform/velero/kustomization.yaml
@@ -5,7 +5,10 @@ resources:
   - namespace.yaml
   - helmrepository.yaml
   - helmrelease.yaml
-  # Scoped MinIO S3 credential (the `cloud` INI key the AWS plugin reads) — SOPS-encrypted, decrypted
-  # per-env by the `velero` Flux Kustomization (clusters/dev). Kept in sync with the staging source of
-  # truth platform/backup/minio-credentials.sops.yaml + the Proxmox host ansible-vault.
+  # Scoped S3 credential for ${S3_BACKUP_ENDPOINT} (the `cloud` INI key the AWS plugin reads) —
+  # SOPS-encrypted, decrypted per-env by the `velero` Flux Kustomization (clusters/dev).
+  # ONE key lives in FOUR Secrets across three namespaces (this one + the three CNPG
+  # *-db-backup-credentials). platform/backup/set-r2-credentials.sh writes all four with `sops set`
+  # and proves they agree; do not hand-edit one of them. platform/backup/minio-credentials.sops.yaml
+  # retains the PRE-MIGRATION MinIO key on purpose. See infra/BACKUP-R2.md.
   - velero-cloud.sops.yaml
diff --git a/platform/velero/values.yaml b/platform/velero/values.yaml
index 5a3ae5a..f43e4ab 100644
--- a/platform/velero/values.yaml
+++ b/platform/velero/values.yaml
@@ -2,11 +2,20 @@
 # doc pointer, kept for parity with the other components' layout).
 #
 # LIVE wiring (see helmrelease.yaml):
-#   - provider aws + velero-plugin-for-aws (init container) → MinIO S3 ${S3_BACKUP_ENDPOINT} (dev: http://192.168.1.9:9000)
-#     (path-style, bucket `velero`, region us-east-1 placeholder).
+#   - provider aws + velero-plugin-for-aws v1.14.2 (init container) → the S3 endpoint
+#     ${S3_BACKUP_ENDPOINT} from cluster-vars. That is a KNOB, not MinIO: dev has been running against
+#     the on-Proxmox MinIO http://192.168.1.9:9000, and as of 2026-09-05 the authored target is
+#     Cloudflare R2 (https://<account-id>.r2.cloudflarestorage.com) — see infra/BACKUP-R2.md.
+#     Always path-style; bucket `velero`; region ${S3_BACKUP_REGION} (MinIO ignores it, R2 demands
+#     exactly `auto`); per-environment prefix ${VELERO_BACKUP_PREFIX}.
+#   - checksumAlgorithm: "" — REQUIRED for R2 and harmless for MinIO. The plugin defaults it to CRC32,
+#     which R2 rejects with HTTP 400 InvalidArgument. Do not drop it; see helmrelease.yaml.
 #   - deployNodeAgent:true + uploaderType:kopia → File System Backup of PVC data (no CSI data-mover).
+#     NOTE this path uses kopia's OWN S3 client, which does not read checksumAlgorithm — backup
+#     metadata and volume data are two separate S3-compatibility questions (infra/BACKUP-R2.md §7).
 #   - snapshotsEnabled:false → no VolumeSnapshotLocation.
 #   - credentials.existingSecret: velero-cloud-credentials (SOPS `cloud` INI key, ns velero).
 #   - two daily Schedules (${VELERO_BACKUP_SCHEDULE} / ttl ${VELERO_RETENTION}): the whole cluster
 #     via FSB, with monitoring+unifi backed up RESOURCES-ONLY (their volume data is reconstructable).
 # DR drill (tested restore) remains a Phase-4 acceptance gate (R-STATE-03) — the PM runs it post-deploy.
+# It is PROVEN against MinIO only; a restore from R2 has never been executed (infra/BACKUP-R2.md §5).