diff --git a/src/test/recovery/meson.build b/src/test/recovery/meson.build
index 7982bb6b0ba..20299e25f7d 100644
--- a/src/test/recovery/meson.build
+++ b/src/test/recovery/meson.build
@@ -67,6 +67,7 @@ tests += {
       't/056_standby_snapshot_export.pl',
       't/057_snapshot_commit_race.pl',
       't/059_remote_apply_status_interval.pl',
+      't/060_repack_postmaster_exit.pl',
     ],
   },
 }
diff --git a/src/test/recovery/t/060_repack_postmaster_exit.pl b/src/test/recovery/t/060_repack_postmaster_exit.pl
new file mode 100644
index 00000000000..22ef3bd5f33
--- /dev/null
+++ b/src/test/recovery/t/060_repack_postmaster_exit.pl
@@ -0,0 +1,140 @@
+# Copyright (c) 2026 PostgreSQL Global Development Group
+#
+# Test that a backend running REPACK (CONCURRENTLY) exits cleanly if the
+# postmaster is killed while the command is in progress.  Killing the
+# postmaster during the "rebuilding index" phase used to make the REPACK
+# steering backend fail the !IsTransactionOrTransactionBlock() assertion
+# in pgstat_report_stat() (or, in a non-cassert build, flush statistics
+# from an inconsistent transaction state), because FATAL errors raised on
+# the process-exit path re-enter proc_exit()/shmem_exit() while the
+# AbortOutOfAnyTransaction() started by the ShutdownPostgres exit callback
+# has not completed yet.  Cover the same exit path for a plain parallel
+# index build, which on postmaster death raises a FATAL error while
+# waiting for its workers.
+
+use strict;
+use warnings FATAL => 'all';
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init();
+$node->append_conf('postgresql.conf', 'wal_level = logical');
+$node->start();
+
+# Build a table big enough that the interesting progress phases last a
+# while.
+$node->safe_psql(
+	'postgres', q(
+	CREATE TABLE repacked (id serial PRIMARY KEY, val text, num int);));
+$node->safe_psql(
+	'postgres', q(
+	INSERT INTO repacked(val, num)
+	SELECT repeat('v', 200)||g::text, g FROM generate_series(1, 800000) g;));
+$node->safe_psql('postgres', q(CREATE INDEX repacked_num ON repacked(num);));
+
+run_kill_test(
+	'REPACK', 'pg_stat_progress_repack', 'rebuilding index',
+	q(REPACK (CONCURRENTLY) repacked;));
+
+run_kill_test(
+	'parallel CREATE INDEX', 'pg_stat_progress_create_index',
+	'building index: scanning table',
+	q(SET max_parallel_maintenance_workers = 4;
+	  CREATE INDEX repacked_num2 ON repacked(num);));
+
+done_testing();
+
+sub run_kill_test
+{
+	my ($name, $progress_view, $target_phase, $command) = @_;
+	my $marker = "COMMAND_FINISHED";
+
+	# Only look at log lines written from now on.
+	my $log_offset = -s $node->logfile;
+
+	# Run the command in the background.
+	my $session = $node->background_psql('postgres');
+	$session->query_until(qr/started/,
+		"\\echo started\n$command\n\\echo $marker\n");
+
+	# Wait until the command reaches the wanted progress phase.
+	ok( $node->poll_query_until(
+			'postgres',
+		 qq[SELECT phase = '$target_phase' FROM $progress_view;]),
+		"$name: command reached phase '$target_phase'");
+
+	# Kill the postmaster, orphaning all its children.  Remember the
+	# children, so that any orphan that does not exit on its own can be
+	# killed below; the node has to recover from all of them dying anyway.
+	my $pm_pid;
+	{
+		my $pidfile = $node->data_dir . "/postmaster.pid";
+		open(my $fh, '<', $pidfile) or die "could not open $pidfile: $!";
+		chomp($pm_pid = <$fh>);
+		close($fh);
+	}
+	my @child_pids = map { $_ + 0 } split /\n/,
+	  $node->safe_psql('postgres', "SELECT pid FROM pg_stat_activity");
+
+	kill(9, $pm_pid);
+	for my $pid (@child_pids)
+	{
+		next if $pid == $pm_pid;
+		my $tries = 0;
+		while (kill(0, $pid) == 1 && $tries++ < 100)
+		{
+			select undef, undef, undef, 0.1;
+		}
+		kill(9, $pid) if kill(0, $pid) == 1;
+	}
+
+	# Wait until the orphaned psql session is gone.  There is no clean way
+	# to shut down psql after the postmaster is gone; if it did not exit on
+	# its own with the dead connection, sending \q might throw a "broken
+	# pipe", which can be ignored.
+	eval {
+		$session->quit();
+		1;
+	} or note("psql session exited: $@");
+
+	# Cluster.pm has no interface for killing a postmaster directly, so
+	# update its idea of the currently running postmaster ourselves, and
+	# remove the stale pid file.
+	$node->{_pid} = undef;
+
+	# The orphaned children may keep the shared memory block in use for a
+	# short while after the postmaster is gone, so keep retrying the start
+	# until they are gone.
+	my $started = 0;
+	for (my $i = 0; $i < 30 and not $started; $i++)
+	{
+		unlink($node->data_dir . "/postmaster.pid");
+		$started = $node->start(fail_ok => 1);
+		sleep(1) unless $started;
+	}
+	ok($started, "$name: node restarted after crash recovery");
+
+	# The exit path of the killed statement must have run cleanly: no
+	# assertion failure in the log (this catches the broken nested
+	# proc_exit()/shmem_exit() unwinding).
+	ok( !$node->log_contains(qr/TRAP: failed Assert/, $log_offset),
+		"$name: no assertion failure in the server log");
+
+	# The cluster must be consistent and the same kind of command must
+	# still be retryable.
+	ok($node->psql('postgres', q(SELECT count(*) FROM repacked;)) == 0,
+		"$name: table readable after crash recovery");
+	is( $node->safe_psql('postgres',
+			q[SELECT count(*) FROM pg_replication_slots;]),
+		0, "$name: no leftover replication slot after restart");
+	is( $node->safe_psql('postgres',
+			q[SELECT count(*) FROM pg_index WHERE NOT (indisvalid AND indisready);]),
+		0, "$name: no leftover invalid index after restart");
+
+	$node->safe_psql('postgres', q(DROP INDEX IF EXISTS repacked_num2;));
+	$node->safe_psql('postgres', q(REPACK (CONCURRENTLY) repacked;));
+
+	return;
+}