diff --git a/xml/rng-helper.in b/xml/rng-helper.in
index d3cf0578ef..634abdfcde 100755
--- a/xml/rng-helper.in
+++ b/xml/rng-helper.in
@@ -1,248 +1,251 @@
 #!@BASH_PATH@
 #
 # Copyright 2014-2024 the Pacemaker project contributors
 #
 # The version control history for this file may have further details.
 #
 # This source code is licensed under the GNU General Public License version 2
 # or later (GPLv2+) WITHOUT ANY WARRANTY.
 #
 
+# @COMPAT "next" schemas are deprecated since 2.1.5
 list_candidates() {
     ls -1 "${1}.rng" "${1}"-[0-9]*.rng "${1}"-next.rng 2>/dev/null
 }
 
 version_from_filename() {
     vff_filename="$1"
 
     case "$vff_filename" in
         *-*.rng)
             echo "$vff_filename" | sed -e 's/.*-\(.*\).rng/\1/'
             ;;
         *)
             # special case for bare ${base}.rng, no -0.1's around anyway
             echo 0.1
             ;;
     esac
 }
 
 filename_from_version() {
     ffv_version="$1"
     ffv_base="$2"
 
     if [ "$ffv_version" = "0.1" ]; then
         echo "${ffv_base}.rng"
     else
         echo "${ffv_base}-${ffv_version}.rng"
     fi
 }
 
 # Convert version string (e.g. 2.10) into integer (e.g. 2010) for comparisons
 int_version() {
     echo "$1" | awk -F. '{ printf("%d%03d\n", $1,$2); }';
 }
 
 # Find the (sub-)schema that best matches a desired version.
 #
 # Version numbers are assumed to be in the format X.Y,
 # where X and Y are integers, and Y is no more than 3 digits,
 # or the special value "next".
+#
+# @COMPAT "next" schemas are deprecated since 2.1.5
 best_match() {
     # (Sub-)schema name (e.g. "resources")
     local base="$1"
 
     # Desired version (e.g. "1.0" or "next")
     local target="$2"
 
     # If not empty, append the best match as an XML externalRef to this file
     # (otherwise, just echo the best match).
     local destination="$3"
 
     # Arbitrary text to print before XML (generally spaces to indent)
     local prefix="$4"
 
     best="0.0"
     for rng in $(list_candidates "${base}"); do
         case ${rng} in
             ${base}-${target}.rng)
                 # We found exactly what was requested
                 best=${target}
                 break
                 ;;
             *-next.rng)
                 # "Next" schemas cannot be a best match unless directly requested
                 ;;
             *)
                 v=$(version_from_filename "${rng}")
 	        if [ $(int_version "${v}") -gt $(int_version "${best}") ]; then
                     # This version beats the previous best match
 
                     if [ "${target}" = "next" ]; then
                         best=${v}
                     elif [ $(int_version "${v}") -lt $(int_version "${target}") ]; then
                         # This value is best only if it's still less than the target
                         best=${v}
                     fi
                 fi
                 ;;
         esac
     done
 
     if [ "$best" != "0.0" ]; then
         found=$(filename_from_version "$best" "$base")
         if [ -z "$destination" ]; then
             echo "$(basename $found)"
         else
             echo "${prefix}<externalRef href=\"$(basename $found)\"/>" >> "$destination"
         fi
         return 0
     fi
     return 1
 }
 
 version_diff() {
     # diff fails with ec=2 if no predecessor is found;
     # this uses '=' GNU extension to sed, if that's not available,
     # one can use: hline=`echo "$${p}" | grep -Fn "$${hunk}" | cut -d: -f1`;
     # XXX: use line information from hunk to avoid "not detected" for ambiguity
     for p in $*; do
         set $(echo "$p" | tr '-' ' ')
         echo "### *-$2.rng vs. predecessor"
 
         for v in *-"$2".rng; do
             echo "#### $v vs. predecessor"
 
             b=$(echo "$v" | cut -d- -f1)
             old=$(best_match "$b" "$1")
             p=$(diff -u "$old" "$v" 2>/dev/null)
 
             case $? in
                 1)
                     echo "$p" | sed -n -e '/^@@ /!d;=;p' -e ':l;n;/^\([- ]\|+.*<[^ />]\+\([^/>]\+="ID\|>$$\)\)/bl;s/^[+ ]\(.*\)/\1/p' |
                     while read -r hline; do
                         if read -r h; then
                             read -r i
                         else
                             break
                         fi
 
                         iline=$(grep -Fn "$i" "$v" | cut -d: -f1)
 
                         if [ "$(echo "$iline" | wc -l)" = "1" ]; then
                             ctxt=$({ sed -n -e "1,$((iline - 1))p" "$v"
                                      echo "<inject id=\"GOAL\"/>$i"
                                      sed -n -e "$((iline + 1)),$ p" "$v"
                                    } | xsltproc --param skip 1 context-of.xsl -)
                         else
                             ctxt="(not detected)"
                         fi
 
                         echo "$p" | sed -n -e "$((hline - 2)),$hline!d" -e '/^\(+++\|---\)/p'
                         echo "$h context: $ctxt"
                         echo "$p" | sed -n -e "1,${hline}d" -e '/^\(---\|@@ \)/be;p;d;:e;n;be'
                     done
 
                     ;;
 
                 2)
                     echo "##### $v has no predecessor"
                     ;;
 
             esac
         done
     done
 }
 
 build_api_rng() {
     local FILENAME="$1"
     local VERSION="$2"
 
     shift 2
 
     cat <<EOF >"$FILENAME"
 <?xml version="1.0" encoding="UTF-8"?>
 <grammar xmlns="http://relaxng.org/ns/structure/1.0" datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
   <start>
     <element name="pacemaker-result">
       <attribute name="api-version"> <text /> </attribute>
       <attribute name="request"> <text /> </attribute>
       <optional>
         <choice>
 EOF
     for RNG in "$@"; do
         best_match "api/$RNG" "$VERSION" "$FILENAME" "          "
     done
     cat <<EOF >>"$FILENAME"
         </choice>
       </optional>
 EOF
     best_match api/status "$VERSION" "$FILENAME" "      "
     cat <<EOF >>"$FILENAME"
     </element>
   </start>
 </grammar>
 EOF
 }
 
 build_cib_rng() {
     local FILENAME="$1"
     local VERSION="$2"
 
     shift 2
     cat <<EOF >"$FILENAME"
 <?xml version="1.0" encoding="UTF-8"?>
 <grammar xmlns="http://relaxng.org/ns/structure/1.0" datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
   <start>
     <element name="cib">
 EOF
     best_match cib "$VERSION" "$FILENAME" "      "
     cat <<EOF >>"$FILENAME"
       <element name="configuration">
         <interleave>
 EOF
     for RNG in "$@"; do
         best_match "$RNG" "$VERSION" "$FILENAME" "          "
     done
     cat <<EOF >>"$FILENAME"
         </interleave>
       </element>
       <optional>
         <element name="status">
 EOF
     best_match status "$VERSION" "$FILENAME" "          "
     cat <<EOF >>"$FILENAME"
         </element>
       </optional>
     </element>
   </start>
 </grammar>
 EOF
 }
 
 # Allow building RNGs from a different directory
 cd "$(dirname $0)"
 
 case "$1" in
     match)
         # Using readlink allows building from a different directory
         best_match "$2" "$3" "$(readlink -f "$4")" "$5"
         ;;
 
     diff)
         shift
         version_diff "$@"
         ;;
 
     build_api_rng)
         build_api_rng "$2" "$3" "${@:4}"
         ;;
 
     build_cib_rng)
         build_cib_rng "$2" "$3" "${@:4}"
         ;;
 
     *)
         echo "Invalid command: $1"
         exit 1
         ;;
 esac