diff --git a/regress/copy-mode-source-blank.sh b/regress/copy-mode-source-blank.sh
new file mode 100644
index 000000000..3df09a359
--- /dev/null
+++ b/regress/copy-mode-source-blank.sh
@@ -0,0 +1,63 @@
+#!/bin/sh
+
+# Trimming a blank source must leave a visible line for cursor reflow.
+
+PATH=/bin:/usr/bin
+TERM=screen
+export PATH TERM
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+
+fail()
+{
+	echo "$*" >&2
+	exit 1
+}
+
+cleanup()
+{
+	$TMUX kill-server 2>/dev/null
+}
+trap cleanup 0
+trap 'exit 1' 1 2 3 15
+
+$TMUX new-session -d -x80 -y24 -s test 'sleep 100' || exit 1
+$TMUX set-option -g window-size manual || exit 1
+$TMUX new-window -t test:1 'sleep 100' || exit 1
+$TMUX resize-window -t test:0 -x20 -y24 || exit 1
+
+# Exercise widening, narrowing, and equal widths with no source history.
+for pair in '0 1' '1 0' '1 2'; do
+	set -- $pair
+	if [ "$2" = 2 ]; then
+		$TMUX new-window -t test:2 'sleep 100' || exit 1
+		$TMUX resize-window -t test:2 -x80 -y24 || exit 1
+	fi
+	source=test:$1.0
+	target=test:$2.0
+	[ "$($TMUX display-message -p -t "$source" '#{history_size}')" = 0 ] ||
+		fail "source has unexpected history"
+	$TMUX copy-mode -s "$source" -t "$target" || exit 1
+	$TMUX has-session -t test || fail "server died copying blank source"
+	[ "$($TMUX display-message -p -t "$target" \
+	    '#{pane_in_mode} #{copy_cursor_x} #{copy_cursor_y}')" = '1 0 0' ] ||
+		fail "blank source did not enter copy mode at the first cell"
+	$TMUX send-keys -t "$target" -X cancel || exit 1
+done
+
+# Real content still trims trailing empty lines, clamping the cursor to beta.
+$TMUX respawn-pane -k -t test:0.0 \
+	"printf 'alpha\r\nbeta\r\n\r\n\r\n'; exec sleep 100" || exit 1
+i=0
+while [ "$($TMUX display-message -p -t test:0.0 '#{cursor_y}')" != 4 ]; do
+	i=$((i + 1))
+	[ "$i" -lt 10 ] || fail "source output did not arrive"
+	sleep 1
+done
+$TMUX copy-mode -s test:0.0 -t test:1.0 || exit 1
+[ "$($TMUX display-message -p -t test:1.0 \
+    '#{pane_in_mode} #{copy_cursor_y} #{copy_cursor_line}')" = '1 1 beta' ] ||
+	fail "nonblank source content or trailing-line trimming changed"
+
+exit 0
diff --git a/regress/mode-tree-menu-position.sh b/regress/mode-tree-menu-position.sh
new file mode 100644
index 000000000..f90dbb9fe
--- /dev/null
+++ b/regress/mode-tree-menu-position.sh
@@ -0,0 +1,71 @@
+#!/bin/sh
+
+# Chooser menus are centred on the mouse using their displayed width. A
+# hidden title must not move a borderless menu away from the mouse.
+
+PATH=/bin:/usr/bin
+TERM=screen
+LC_ALL=C.UTF-8
+export TERM LC_ALL
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
+
+cleanup()
+{
+	$TMUX kill-server >/dev/null 2>&1
+	$TMUX2 kill-server >/dev/null 2>&1
+}
+trap cleanup 0 1 15
+
+fail()
+{
+	echo "$*" >&2
+	exit 1
+}
+
+$TMUX new-session -d -s short -x 100 -y 30 'sleep 100' || exit 1
+$TMUX set -g mouse on || exit 1
+$TMUX set -g status off || exit 1
+$TMUX2 new-session -d -x 100 -y 30 "$TMUX attach" || exit 1
+sleep 1
+
+for name in short aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa; do
+	$TMUX rename-session "$name" || exit 1
+	for lines in none single padded; do
+		$TMUX set -g menu-border-lines "$lines" || exit 1
+		$TMUX choose-tree -s || exit 1
+		sleep 1
+
+		# Right-button press at window (60, 0), away from either edge.
+		seq=$(printf '\033[<2;61;1M')
+		$TMUX2 send-keys -l "$seq" || exit 1
+		sleep 1
+
+		row=2
+		column=54
+		if [ "$lines" = none ]; then
+			row=1
+		elif [ "$name" != short ]; then
+			column=31
+		fi
+		text=$($TMUX2 capture-pane -p | awk -v row="$row" \
+		    -v column="$column" 'NR == row {
+			# Keep byte offsets equal to columns with non-Unicode awk.
+			gsub(/│/, "|")
+			print substr($0, column, 7)
+		    }')
+		[ "$text" = 'Select ' ] || \
+		    fail "$lines menu for $name: expected Select at ($column, $row), got '$text'"
+
+		# Close the menu, release the button, then leave the chooser.
+		$TMUX2 send-keys Escape || exit 1
+		seq=$(printf '\033[<2;61;1m')
+		$TMUX2 send-keys -l "$seq" || exit 1
+		$TMUX2 send-keys q || exit 1
+		sleep 1
+	done
+done
+
+exit 0
diff --git a/regress/screen-redraw-menus.sh b/regress/screen-redraw-menus.sh
index 1bd3bc99b..823b03c88 100644
--- a/regress/screen-redraw-menus.sh
+++ b/regress/screen-redraw-menus.sh
@@ -106,9 +106,28 @@ compare menu-over-split
 
 # Menu with no border lines.
 setup 40 14
-menu -b none -x6 -y8
+$TMUX2 display-menu -T "This title must not reserve width" -C 1 \
+    -b none -x6 -y8 \
+    "Alpha item" a "" \
+    "Beta item" b "" \
+    "" "" "" \
+    "Gamma item" g "" || exit 1
+sleep 1
 compare menu-noborder
 
+# Menu border style follows the explicitly targeted window, not the current
+# window when a different pane is selected.
+setup 40 14
+$TMUX2 set menu-border-lines none || exit 1
+$TMUX2 neww || exit 1
+$TMUX2 display-menu -t%0 -T "Menu" -C 1 \
+    "Alpha item" a "" \
+    "Beta item" b "" \
+    "" "" "" \
+    "Gamma item" g "" || exit 1
+$TMUX2 selectw -t%0 || exit 1
+compare menu-target-window-noborder
+
 # Menu with double border lines.
 setup 40 14
 menu -b double -x6 -y8
diff --git a/regress/screen-redraw-results/menu-noborder.result b/regress/screen-redraw-results/menu-noborder.result
index d6479edba..d0f0dc58a 100644
--- a/regress/screen-redraw-results/menu-noborder.result
+++ b/regress/screen-redraw-results/menu-noborder.result
@@ -1,11 +1,11 @@
 MENU00 abcdefghij
 MENU01 abcdefghij
-MENU02  Menu            
-MENU03  Alpha item (a)  
-MENU04  Beta item  (b)  
-MENU05                  
-MENU06  Gamma item (g)  
-MENU07                  
+MENU02 abcdefghij
+MENU03 abcdefghij
+MENU04 Alpha item (a) 
+MENU05 Beta item  (b) 
+MENU06                
+MENU07 Gamma item (g) 
 MENU08 abcdefghij
 MENU09 abcdefghij
 MENU10 abcdefghij
diff --git a/regress/screen-redraw-results/menu-target-window-noborder.result b/regress/screen-redraw-results/menu-target-window-noborder.result
new file mode 100644
index 000000000..a7ac507a1
--- /dev/null
+++ b/regress/screen-redraw-results/menu-target-window-noborder.result
@@ -0,0 +1,13 @@
+MENU00 abcdefghij
+MENU01 abcdefghij
+MENU02 abcdefghij
+MENU03 abcdefghij
+MENU04 abcd Alpha item (a) 
+MENU05 abcd Beta item  (b) 
+MENU06 abcd                
+MENU07 abcd Gamma item (g) 
+MENU08 abcdefghij
+MENU09 abcdefghij
+MENU10 abcdefghij
+MENU11 abcdefghij
+MENU12 abcdefghij