diff --git a/MockBuildUtils.pm b/MockBuildUtils.pm
index aa9065b..a03c2f7 100644
--- a/MockBuildUtils.pm
+++ b/MockBuildUtils.pm
@@ -20,7 +20,7 @@ our @EXPORT_OK = qw(
     parse_evr evr_cmp evr_constraint_ok parse_pin rpmkeys_checksig_problem
     rpm_version rpm_release rpm_sigmd5 rpm_is_signed restamp_release_line
     cross_copy_genesis finalize_xcat_dep bump_dep_release_suffix
-    build_mock_uniqueext
+    build_mock_uniqueext rpm_arch rpm_in_cell
 );
 
 # install_deps_packages($os_id): the host packages mockbuild-all.pl needs to run at all, for the
@@ -568,6 +568,32 @@ sub bump_dep_release_suffix {
 # their roots apart, so three concurrent el8/el9/el10 ppc64le goconserver builds race in one root.
 # When the id is too long, keep a readable leading token AND append a short digest of the FULL id, so
 # distinct ids always yield distinct uniqueext regardless of where in the string they differ.
+# rpm_arch($rpm): the architecture of an rpm. The header decides when the file can be read, so a
+# renamed file does not pass for another architecture; a bare file name falls back to its suffix.
+sub rpm_arch {
+    my ($rpm) = @_;
+    return unless defined $rpm;
+    if (-f $rpm) {
+        my $arch = `rpm -qp --qf '%{ARCH}' ${\ sh_quote($rpm)} 2>/dev/null`;
+        chomp $arch;
+        return $arch if $arch ne '';
+    }
+    my ($arch) = $rpm =~ /\.([A-Za-z0-9_]+)\.rpm$/;
+    return $arch;
+}
+
+# rpm_in_cell($rpm, $target_arch): whether an rpm belongs in the repository cell of $target_arch.
+# A noarch builder run in another architecture's chroot (the x86 boot loaders for riscv64) can
+# emit that chroot's native rpms beside the noarch one; only noarch and the cell's own
+# architecture are kept.
+sub rpm_in_cell {
+    my ($rpm, $target_arch) = @_;
+    my $arch = rpm_arch($rpm);
+    return 0 unless defined $arch && defined $target_arch;
+    return 1 if $arch eq 'noarch';
+    return $arch eq $target_arch ? 1 : 0;
+}
+
 sub build_mock_uniqueext {
     my ($run, $seq, $label) = @_;
 
diff --git a/mockbuild-all.pl b/mockbuild-all.pl
index cfd532c..6f97fd0 100755
--- a/mockbuild-all.pl
+++ b/mockbuild-all.pl
@@ -15,7 +15,7 @@ use Parallel::ForkManager;
 use POSIX qw(strftime);
 use FindBin qw($RealBin);
 use lib $RealBin, "$RealBin/lib";
-use MockBuildUtils qw(sh_quote print_step version_matches required_pkgs
+use MockBuildUtils qw(sh_quote print_step version_matches required_pkgs rpm_in_cell
                       install_deps_packages install_deps_command missing_perl_modules
                       read_manifest verify_repo_packages verify_repo_signature verify_rpm_signatures
                       rpm_version rpm_release rpm_sigmd5 restamp_release_line
@@ -848,11 +848,13 @@ print_step('Collect RPM artifacts');
 print "collection roots:\n";
 print "  $_\n" for @collect_roots;
 
-my ($copied, $skipped_src, $missing_roots) = collect_rpms(
+my ($copied, $skipped_src, $missing_roots, $skipped_foreign) = collect_rpms(
     roots    => \@collect_roots,
     dest_dir => $repo_dir,
+    arch     => $arch,
     dry_run  => $dry_run,
 );
+print "skipped $skipped_foreign rpm(s) of another architecture\n" if $skipped_foreign;
 
 # Assert on what this run BUILT, before the Genesis release is added: the release is
 # installed from a verified directory rather than built here, so counting it first would
@@ -1970,11 +1972,13 @@ sub collect_rpms {
     my (%args) = @_;
     my $roots = $args{roots} // [];
     my $dest  = $args{dest_dir} // die "collect_rpms missing dest_dir\n";
+    my $cell_arch = $args{arch} // die "collect_rpms missing arch\n";
     my $is_dry = $args{dry_run} ? 1 : 0;
 
     my %seen;
     my $copied = 0;
     my $skipped_src = 0;
+    my $skipped_foreign = 0;
     my $missing_roots = 0;
 
     for my $root (@{$roots}) {
@@ -2002,6 +2006,10 @@ sub collect_rpms {
             my $base = basename($rpm);
             next if $genesis_release
               && $base =~ /^xCAT-genesis-openembedded-/;
+            if (!rpm_in_cell($rpm, $cell_arch)) {
+                $skipped_foreign++;
+                next;
+            }
             next if $seen{$base}++;
             if ($is_dry) {
                 print "DRY-RUN copy: $rpm -> $dest/$base\n";
@@ -2014,7 +2022,7 @@ sub collect_rpms {
         }
     }
 
-    return ($copied, $skipped_src, $missing_roots);
+    return ($copied, $skipped_src, $missing_roots, $skipped_foreign);
 }
 
 sub collect_srpms {