diff --git a/secrets b/secrets
index 52b6129..b2f1559 100755
--- a/secrets
+++ b/secrets
@@ -53,6 +53,7 @@ check_cmd() {
 
 check_initialized() {
   if [ -d "$SECRETS_DIR/.git" ]; then
+    _check_store_version_skew
     return
   fi
   if [ "$STORE_SOURCE" != "default" ]; then
@@ -539,6 +540,72 @@ _store_format() {
   echo 1
 }
 
+# ─── Client/store version skew (EGB-713) ──────────────────────────────
+#
+# The running client's own version, read from the VERSION file shipped beside
+# the script. Empty/"0.0.0.0" if absent — treated as "unknown/oldest" so a
+# missing VERSION never triggers a spurious nudge.
+_client_version() {
+  local v=""
+  [ -f "$SCRIPT_DIR/VERSION" ] && v=$(head -1 "$SCRIPT_DIR/VERSION" 2>/dev/null | tr -d '\r\n[:space:]')
+  printf '%s' "${v:-0.0.0.0}"
+}
+
+# Numeric four-field (MAJOR.MINOR.PATCH.MICRO) compare. Returns 0 iff $1 > $2.
+# Per-field numeric (so 0.10.0.0 > 0.7.0.0); missing/garbage fields → 0.
+_version_gt() {
+  local a="$1" b="$2" i ai bi; local -a af bf
+  IFS=. read -r -a af <<< "$a"; IFS=. read -r -a bf <<< "$b"
+  for i in 0 1 2 3; do
+    ai=${af[$i]:-0}; ai=${ai//[!0-9]/}; [ -n "$ai" ] || ai=0
+    bi=${bf[$i]:-0}; bi=${bi//[!0-9]/}; [ -n "$bi" ] || bi=0
+    if [ "$((10#$ai))" -gt "$((10#$bi))" ]; then return 0; fi
+    if [ "$((10#$ai))" -lt "$((10#$bi))" ]; then return 1; fi
+  done
+  return 1
+}
+
+WRITER_VERSION_FILE_NAME=".secrets-writer-version"
+# Highest client version recorded as having written to the store (empty if the
+# store predates this feature — "minus the initial builds", silent by design).
+_store_writer_version() {
+  local f="$SECRETS_DIR/$WRITER_VERSION_FILE_NAME"
+  if [ -f "$f" ]; then
+    head -1 "$f" 2>/dev/null | tr -d '\r\n[:space:]'
+  fi
+  return 0
+}
+
+# Raise the store's recorded writer-version to the client's version (monotonic;
+# never lowers it). Called right before each store-committing `git add -A` so
+# the stamp rides the same commit. Read paths (pull) never call this.
+_stamp_writer_version() {
+  local cur cli
+  cur=$(_store_writer_version)
+  cli=$(_client_version)
+  if [ -z "$cur" ] || _version_gt "$cli" "$cur"; then
+    printf '%s\n' "$cli" > "$SECRETS_DIR/$WRITER_VERSION_FILE_NAME"
+  fi
+}
+
+# Warn ONCE per invocation if the store was last written by a newer client than
+# us. Non-fatal (read/write paths keep their exit codes). Silent when the store
+# carries no writer-version (legacy) or is same/older than us.
+_VERSION_SKEW_WARNED=0
+_check_store_version_skew() {
+  [ "$_VERSION_SKEW_WARNED" = 1 ] && return 0
+  local sv cv
+  sv=$(_store_writer_version)
+  [ -n "$sv" ] || return 0
+  cv=$(_client_version)
+  if _version_gt "$sv" "$cv"; then
+    _VERSION_SKEW_WARNED=1
+    echo "NOTE: this store was last written by secrets v$sv; you're on v$cv." >&2
+    echo "      Update your secrets tool: git -C \"$SCRIPT_DIR\" pull" >&2
+  fi
+  return 0
+}
+
 # Resolve the on-disk path of an external blob for READING. Tries the v2 suffix
 # (.properties.age) first, then falls back to the v1 (.gradle-properties.age) for
 # `properties` externals, so an upgraded client finds the blob whichever format
@@ -1262,6 +1329,7 @@ commit_and_push_secrets() {
   # store missing the key.txt line would stage and push the private key.
   ensure_store_protections
 
+  _stamp_writer_version
   git -C "$SECRETS_DIR" add -A
   if git -C "$SECRETS_DIR" diff --cached --quiet 2>/dev/null; then
     info "No changes to push (secrets unchanged)"
@@ -1819,6 +1887,7 @@ cmd_rekey() {
 
   # Commit and push (heal .gitignore first so add -A can't stage key.txt)
   ensure_store_protections
+  _stamp_writer_version
   git -C "$SECRETS_DIR" add -A
   git -C "$SECRETS_DIR" commit -m "rekey all secrets" >/dev/null
   if git -C "$SECRETS_DIR" remote get-url origin >/dev/null 2>&1; then
@@ -1949,6 +2018,15 @@ cmd_which() {
   # EGB-700 (folded into EGB-703): surface the store format so users can tell
   # v1 from v2 during the migration window. v1 = legacy store, no format marker.
   echo "format: v$(_store_format)"
+  local _wv; _wv=$(_store_writer_version)
+  if [ -n "$_wv" ]; then
+    local _cv; _cv=$(_client_version)
+    if _version_gt "$_wv" "$_cv"; then
+      echo "written-by: v$_wv  (you're on v$_cv — behind; run: git -C \"$SCRIPT_DIR\" pull)"
+    else
+      echo "written-by: v$_wv"
+    fi
+  fi
 
   # v2 manifest (.secrets.json): validate and summarize. Validation here
   # is deliberately fatal (symlink / malformed / unsupported version) so
@@ -2212,6 +2290,7 @@ _migrate_project() {
     return 0
   fi
   ensure_store_protections
+  _stamp_writer_version
   git -C "$SECRETS_DIR" add -A
   git -C "$SECRETS_DIR" commit -m "migrate: copy-forward v2 twins for $project" >/dev/null 2>&1 || true
   # Push the twins so a --finalize on another machine sees them (finalize
@@ -2302,6 +2381,7 @@ $untwinned  cd into each project and run 'secrets migrate', then re-run 'secrets
     # No v1 blobs at all — just stamp the marker (dotenv/file-only store).
     printf '2\n' > "$SECRETS_DIR/$STORE_FORMAT_FILE_NAME"
     ensure_store_protections
+    _stamp_writer_version
     git -C "$SECRETS_DIR" add -A
     git -C "$SECRETS_DIR" commit -m "migrate: finalize store format v2" >/dev/null 2>&1 || true
     git -C "$SECRETS_DIR" remote get-url origin >/dev/null 2>&1 && git -C "$SECRETS_DIR" push >/dev/null 2>&1 || true
@@ -2337,6 +2417,7 @@ $untwinned  cd into each project and run 'secrets migrate', then re-run 'secrets
   done < <(find "$SECRETS_DIR" -type f -name '*.gradle-properties.age')
 
   ensure_store_protections
+  _stamp_writer_version
   git -C "$SECRETS_DIR" add -A
   git -C "$SECRETS_DIR" commit -m "migrate: finalize store format v2 (drop $v1count v1 blob(s))" >/dev/null 2>&1 || true
   git -C "$SECRETS_DIR" remote get-url origin >/dev/null 2>&1 && git -C "$SECRETS_DIR" push >/dev/null 2>&1 || true
diff --git a/test/version.bats b/test/version.bats
new file mode 100644
index 0000000..fa12630
--- /dev/null
+++ b/test/version.bats
@@ -0,0 +1,106 @@
+#!/usr/bin/env bats
+# EGB-713 version-skew nudge: writer-version stamp, numeric comparator, skew
+# warning, `which` surface. bash 3.2: every standalone [[ ]] ends with || false.
+
+load test_helper
+
+VERSION_FILE() { echo "$(cd "$(dirname "$SECRETS_BIN")" && pwd)/VERSION"; }
+
+# ─── comparator contract ──────────────────────────────────────────────
+
+@test "version comparator orders 0.7.0.0 < 0.10.0.0 numerically (not lexically)" {
+  run bash -c '
+    _version_gt() {
+      local a="$1" b="$2" i ai bi; local -a af bf
+      IFS=. read -r -a af <<< "$a"; IFS=. read -r -a bf <<< "$b"
+      for i in 0 1 2 3; do
+        ai=${af[$i]:-0}; ai=${ai//[!0-9]/}; [ -n "$ai" ] || ai=0
+        bi=${bf[$i]:-0}; bi=${bi//[!0-9]/}; [ -n "$bi" ] || bi=0
+        if [ "$((10#$ai))" -gt "$((10#$bi))" ]; then return 0; fi
+        if [ "$((10#$ai))" -lt "$((10#$bi))" ]; then return 1; fi
+      done; return 1
+    }
+    _version_gt 0.10.0.0 0.7.0.0 && echo "10gt7"
+    _version_gt 0.7.0.0 0.10.0.0 || echo "7not_gt_10"
+    _version_gt 0.7.0.0 0.7.0.0 || echo "equal_not_gt"
+    _version_gt 1.0.0.0 0.9.9.9 && echo "major_wins"
+  '
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"10gt7"* ]] || false
+  [[ "$output" == *"7not_gt_10"* ]] || false
+  [[ "$output" == *"equal_not_gt"* ]] || false
+  [[ "$output" == *"major_wins"* ]] || false
+}
+
+# ─── stamp on write ───────────────────────────────────────────────────
+
+@test "push stamps the store writer-version with the client version" {
+  init_with_remote
+  create_project_dir wvstamp
+  "$SECRETS_BIN" push wvstamp >/dev/null 2>&1
+  [ -f "$SECRETS_DIR/.secrets-writer-version" ]
+  run cat "$SECRETS_DIR/.secrets-writer-version"
+  [ "$output" = "$(cat "$(VERSION_FILE)")" ]
+}
+
+@test "writer-version stamp is monotonic (a push never lowers a higher stamp)" {
+  init_with_remote
+  create_project_dir wvmono
+  printf '9.9.9.9\n' > "$SECRETS_DIR/.secrets-writer-version"
+  "$SECRETS_BIN" push wvmono >/dev/null 2>&1
+  run cat "$SECRETS_DIR/.secrets-writer-version"
+  [ "$output" = "9.9.9.9" ]
+}
+
+@test "writer-version stamp is committed, not gitignored" {
+  init_with_remote
+  create_project_dir wvcommit
+  "$SECRETS_BIN" push wvcommit >/dev/null 2>&1
+  run bash -c "git -C $SECRETS_DIR ls-files | grep -qx .secrets-writer-version"
+  [ "$status" -eq 0 ]
+}
+
+# ─── skew warning on command ──────────────────────────────────────────
+
+@test "a store written by a newer version warns on a command (non-fatal)" {
+  init_with_remote
+  create_project_dir skewwarn
+  "$SECRETS_BIN" push skewwarn >/dev/null 2>&1
+  printf '99.0.0.0\n' > "$SECRETS_DIR/.secrets-writer-version"
+  run "$SECRETS_BIN" list
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"last written by secrets v99.0.0.0"* ]] || false
+  [[ "$output" == *"Update your secrets tool"* ]] || false
+}
+
+@test "a store at the same/older version is silent" {
+  init_with_remote
+  create_project_dir noskew
+  "$SECRETS_BIN" push noskew >/dev/null 2>&1
+  run "$SECRETS_BIN" list
+  [ "$status" -eq 0 ]
+  [[ "$output" != *"Update your secrets tool"* ]] || false
+}
+
+@test "a store with no writer-version marker is silent (legacy store)" {
+  init_with_remote
+  create_project_dir legacynostamp
+  "$SECRETS_BIN" push legacynostamp >/dev/null 2>&1
+  rm -f "$SECRETS_DIR/.secrets-writer-version"
+  run "$SECRETS_BIN" list
+  [ "$status" -eq 0 ]
+  [[ "$output" != *"Update your secrets tool"* ]] || false
+}
+
+# ─── which surface ────────────────────────────────────────────────────
+
+@test "which prints the store writer-version and a behind note" {
+  init_with_remote
+  create_project_dir whichwv
+  "$SECRETS_BIN" push whichwv >/dev/null 2>&1
+  printf '99.0.0.0\n' > "$SECRETS_DIR/.secrets-writer-version"
+  run "$SECRETS_BIN" which
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"written-by: v99.0.0.0"* ]] || false
+  [[ "$output" == *"behind"* ]] || false
+}