diff --git a/builddebs.pl b/builddebs.pl
index 7f9ce1062..eb6576b80 100755
--- a/builddebs.pl
+++ b/builddebs.pl
@@ -293,6 +293,11 @@ sub collect_debs {
 # (<codename>-<arch>-sbuild). They hand out disposable overlay sessions, so what the build
 # installs is discarded and the next codename starts from the pristine base.
 
+# Where the build runs inside the chroot. A directory of its own at the chroot root, because
+# every other candidate is shared: /build and /opt/xcat-ci-shared are bind mounts the sbuild
+# chroots give to every session.
+my $GENESIS_STAGE = '/xcat-genesis-build';
+
 sub host_deb_arch {
     my $arch = `dpkg --print-architecture 2>/dev/null` // '';
     chomp $arch;
@@ -350,24 +355,28 @@ sub build_one_genesis_deb {
         # The builder needs its own directory, and Version and Release beside it. Copy them
         # in rather than bind-mount the checkout: the build rewrites debian/control and
         # debian/changelog, and it must not rewrite them in the tree the pipeline builds from.
-        sh_or_die("mkdir -p " . sh_quote("$root/build/xCAT-genesis-builder"),
+        #
+        # NOT under /build: the sbuild chroots bind-mount /var/lib/sbuild/build there, so every
+        # session of every chroot shares one directory. Two builds running at once overwrite each
+        # other's copy of the builder, and the output of an earlier run is still in it. A
+        # directory of its own at the chroot root lives in the session overlay and goes with it.
+        my $stage = "$root$GENESIS_STAGE";
+        sh_or_die("rm -rf " . sh_quote($stage) . " && mkdir -p "
+                . sh_quote("$stage/xCAT-genesis-builder"),
             "FATAL: cannot make the build directory in session:$id\n");
         sh_or_die("cp -a " . sh_quote("$ROOT/xCAT-genesis-builder") . "/. "
-                . sh_quote("$root/build/xCAT-genesis-builder") . "/",
+                . sh_quote("$stage/xCAT-genesis-builder") . "/",
             "FATAL: cannot copy xCAT-genesis-builder into session:$id\n");
-        for my $f (qw(Version Release)) {
-            next unless -f "$ROOT/$f";
-            copy("$ROOT/$f", "$root/build/$f")
-                or die "FATAL: cannot copy $f into session:$id: $!\n";
-        }
-        write_text("$root/build/Release", "$RELEASE\n");
+        copy("$ROOT/Version", "$stage/Version")
+            or die "FATAL: cannot copy Version into session:$id: $!\n";
+        write_text("$stage/Release", "$RELEASE\n");
 
         # --expect-codename is the guard that keeps the image and the root together: the
         # builder stops when the root it woke up in is not the release it was asked for.
         my $cmd = join ' ',
             'schroot', '--run-session', '-c', sh_quote("session:$id"), '-u', 'root', '-d', '/',
-            '--', '/bin/bash', '/build/xCAT-genesis-builder/builddeb-genesis-base',
-            '--expect-codename', sh_quote($codename), '--outdir', '/build/out';
+            '--', '/bin/bash', "$GENESIS_STAGE/xCAT-genesis-builder/builddeb-genesis-base",
+            '--expect-codename', sh_quote($codename), '--outdir', "$GENESIS_STAGE/out";
         my $rc = sh("$cmd > " . sh_quote($logfile) . " 2>&1");
 
         # The log is read whether or not the command failed: a build that exits 0 with
@@ -379,7 +388,7 @@ sub build_one_genesis_deb {
         }
         die $problems if $problems;
 
-        my @debs = glob("$root/build/out/*.deb");
+        my @debs = glob("$root$GENESIS_STAGE/out/*.deb");
         die "FATAL: the Genesis build for $codename produced no .deb; log: $logfile\n"
             unless @debs;
         for my $deb (@debs) {
diff --git a/docs/source/developers/guides/code/builds.rst b/docs/source/developers/guides/code/builds.rst
index 1146e4225..b1c8fe9d5 100644
--- a/docs/source/developers/guides/code/builds.rst
+++ b/docs/source/developers/guides/code/builds.rst
@@ -65,6 +65,20 @@ ppc64el, and every release the repository serves declares the architecture;
 ``xCAT-genesis-scripts`` keeps the two architectures it has control files for,
 because riscv64 Genesis ships as an OpenEmbedded package instead.
 
+The Genesis image is the exception, and it is off unless it is asked for::
+
+    ./builddebs.pl --genesis-only --genesis-dist jammy --genesis-dist noble
+
+``dracut`` copies the kernel, the kernel modules and every command out of the root
+it runs in, so the image belongs to the release that built it. ``--genesis`` builds
+one image per ``--genesis-dist`` codename inside that codename's
+``<codename>-<arch>-sbuild`` schroot -- the chroots xcat-dep's ``sbuild-all.pl``
+creates on the Ubuntu build host -- for the architecture of the build host. It
+refuses to run in a root of another release, it fails the build on an error in the
+log even when the exit status is 0, and it checks the extracted payload against the
+commands the dracut module installs. ``--genesis-only`` builds the images and
+nothing else, which is what xcat-dep consumes with ``--genesis-deb``.
+
 Helpers shared by both builders live in ``build-utils/lib/XCAT/BuildUtils.pm``.
 
 ``buildcore.sh`` builds the architecture specific packages (``xCAT``, ``xCATsn``,
diff --git a/xCAT-genesis-builder/builddeb-genesis-base b/xCAT-genesis-builder/builddeb-genesis-base
index 6396754cc..64dab3b3a 100755
--- a/xCAT-genesis-builder/builddeb-genesis-base
+++ b/xCAT-genesis-builder/builddeb-genesis-base
@@ -105,14 +105,35 @@ add_first_available() {
     echo "ERROR: $CODENAME carries none of these packages: $*" >&2
     exit 1
 }
+# A package that exists only on some releases. 26.04 moved the backward-compatibility zone
+# names (Chile/Continental and the rest of the list the dracut module installs) out of tzdata
+# into tzdata-legacy.
+add_if_available() {
+    local p
+    for p in "$@"; do
+        apt-cache show "$p" >/dev/null 2>&1 && REQUIRED_PACKAGES="$REQUIRED_PACKAGES $p"
+    done
+    return 0
+}
+
 add_first_available bind9-dnsutils dnsutils
 add_first_available util-linux-extra util-linux
+add_if_available tzdata-legacy
 
 apt-get install -y --no-install-recommends $REQUIRED_PACKAGES
 
 # dpkg-architecture comes from dpkg-dev, which the line above installs.
 TRIPLET=$(dpkg-architecture -qDEB_HOST_MULTIARCH)
 
+# ncurses-base put its terminfo entries under /lib/terminfo before 24.04, and both dracut's own
+# terminfo module and the 97xcat module ask for /usr/share/terminfo. On jammy the build stopped
+# on /usr/share/terminfo/l/linux. Give this build root the path they ask for; the chroot is
+# thrown away when the build ends.
+if [ -d /lib/terminfo ]; then
+    mkdir -p /usr/share/terminfo
+    cp -an /lib/terminfo/. /usr/share/terminfo/ 2>/dev/null || true
+fi
+
 # Set up dracut module
 if [ -d /usr/lib/dracut/modules.d ]; then
     DRACUT_PARENT=/usr/lib/dracut/modules.d