diff --git a/regress/control-client-new-layouts.sh b/regress/control-client-new-layouts.sh
new file mode 100755
index 000000000..1c5a51ccf
--- /dev/null
+++ b/regress/control-client-new-layouts.sh
@@ -0,0 +1,123 @@
+#!/bin/sh
+
+# Check that control client flags are available in every format expansion path
+# used to produce layouts. The layout strings themselves are tested separately.
+
+PATH=/bin:/usr/bin
+TERM=screen
+LC_ALL=C.UTF-8
+LANG=C.UTF-8
+export PATH TERM LC_ALL LANG
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+
+DIR=$(mktemp -d) || exit 1
+FIFO=$DIR/input
+OUT=$DIR/output
+CFG=$DIR/flags.conf
+PID=
+
+fail()
+{
+	echo "$*" >&2
+	exit 1
+}
+
+cleanup()
+{
+	exec 3>&-
+	[ -n "$PID" ] && kill "$PID" 2>/dev/null
+	$TMUX kill-server 2>/dev/null
+	rm -rf "$DIR"
+}
+trap cleanup EXIT
+
+wait_for()
+{
+	pattern=$1
+	i=0
+
+	while [ "$i" -lt 50 ]; do
+		grep -F -- "$pattern" "$OUT" >/dev/null 2>&1 && return 0
+		if [ -n "$PID" ] && ! kill -0 "$PID" 2>/dev/null; then
+			fail "control client exited waiting for: $pattern"
+		fi
+		sleep 0.1
+		i=$((i + 1))
+	done
+	fail "missing: $pattern"
+}
+
+send()
+{
+	printf '%s\n' "$*" >&3
+}
+
+check_commands()
+{
+	name=$1
+	expected=$2
+	match='#{m:*new-layouts*,#{client_flags}}'
+
+	send "display-message -p 'DISPLAY-$name $match'"
+	wait_for "DISPLAY-$name $expected"
+	send "list-panes -F 'PANES-$name $match'"
+	wait_for "PANES-$name $expected"
+	send "list-windows -F 'WINDOWS-$name $match'"
+	wait_for "WINDOWS-$name $expected"
+	send "list-sessions -F 'SESSIONS-$name $match'"
+	wait_for "SESSIONS-$name $expected"
+	send "list-clients -F 'CLIENTS-$name $match'"
+	wait_for "CLIENTS-$name $expected"
+}
+
+check_config()
+{
+	name=$1
+	expected=$2
+
+	send "source-file '$CFG'"
+	send "display-message -p 'CONFIG-$name #{@config-new-layouts}'"
+	wait_for "CONFIG-$name $expected"
+}
+
+cat >"$CFG" <<'EOF'
+%if #{m:*new-layouts*,#{client_flags}}
+set-option -g @config-new-layouts 1
+%else
+set-option -g @config-new-layouts 0
+%endif
+EOF
+
+$TMUX kill-server 2>/dev/null
+$TMUX new-session -d -s layouts -x 80 -y 24 || exit 1
+$TMUX split-window -h -t layouts: || exit 1
+
+mkfifo "$FIFO" || exit 1
+: >"$OUT"
+$TMUX -C attach-session -t layouts <"$FIFO" >"$OUT" 2>&1 &
+PID=$!
+exec 3>"$FIFO"
+
+send 'display-message -p READY'
+wait_for READY
+
+check_commands OFF 0
+check_config OFF 0
+
+send 'refresh-client -f new-layouts'
+check_commands ON 1
+check_config ON 1
+
+send 'refresh-client -f !new-layouts'
+check_commands OFF-AGAIN 0
+check_config OFF-AGAIN 0
+
+# The list commands also run for unattached command clients. Supplying that
+# client to formats must not make the session loop dereference a NULL session.
+$TMUX list-sessions -F '#{S:all,active}' >/dev/null ||
+	fail "session loop failed for unattached command client"
+$TMUX has-session -t layouts || fail "server exited"
+
+exit 0