diff --git a/regress/floating-pane-geometry.sh b/regress/floating-pane-geometry.sh
new file mode 100644
index 000000000..7bd033ff6
--- /dev/null
+++ b/regress/floating-pane-geometry.sh
@@ -0,0 +1,203 @@
+#!/bin/sh
+
+# Test new-pane, resize-pane, and move-pane -x/-y/-X/-Y with floating panes.
+# Verifies that size and position are correctly applied with the default border,
+# with -B none, and with the pane-border-lines window option set to none. Also
+# verifies that zero sizes are rejected.
+#
+# With a border, -x/-y/-X/-Y specify the onscreen footprint including the
+# border: new-pane subtracts 2 from width/height and adds 1 to x/y-position
+# so that the border lands on the specified screen coordinates. resize-pane
+# -x/-y similarly subtracts 2 from the requested size. move-pane -X/-Y adds 1
+# to the position. Without a border all values are used directly.
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -Ltest -f/dev/null"
+$TMUX kill-server 2>/dev/null
+
+fail()
+{
+	echo "$*" >&2
+	$TMUX kill-server 2>/dev/null
+	exit 1
+}
+
+must_fail()
+{
+	"$@" >/dev/null 2>&1 && fail "unexpected success: $*"
+	return 0
+}
+
+must_equal()
+{
+	got=$1
+	want=$2
+	[ "$got" = "$want" ] || fail "got '$got', expected '$want'"
+}
+
+$TMUX new-session -d -x 80 -y 24 || exit 1
+
+# --- Default border (single-line) ---
+
+# Explicit values: border subtracts 2 from size and adds 1 to position.
+# -x 20 -> pane_width 18; -y 6 -> pane_height 4;
+# -X 8  -> pane_left  9;  -Y 3 -> pane_top    4.
+id=$($TMUX new-pane -dPF '#{pane_id}' -x 20 -y 6 -X 8 -Y 3 'sleep 100') \
+	|| fail "new-pane with explicit geometry failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')"  18
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 4
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')"   9
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"    4
+
+# resize-pane with border: requested size decremented by 2.
+$TMUX resize-pane -t "$id" -x 30 || fail "resize-pane -x 30 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')" 28
+$TMUX resize-pane -t "$id" -y 10 || fail "resize-pane -y 10 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 8
+
+# resize-pane with percentage and border.
+# 75% of 80 = 60, 60 - 2 = 58; 75% of 24 = 18, 18 - 2 = 16.
+$TMUX resize-pane -t "$id" -x 75% || fail "resize-pane -x 75% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')" 58
+$TMUX resize-pane -t "$id" -y 75% || fail "resize-pane -y 75% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 16
+$TMUX kill-pane -t "$id" || exit 1
+
+# Percentage width, height and position with border.
+# 50% of 80 = 40, 40-2 = 38; 50% of 24 = 12, 12-2 = 10.
+# 10% of 80 =  8,  8+1 =  9; 10% of 24 =  2,  2+1 =  3.
+id=$($TMUX new-pane -dPF '#{pane_id}' -x 50% -y 50% -X 10% -Y 10% 'sleep 100') \
+	|| fail "new-pane with percentage geometry failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')"  38
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 10
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')"   9
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"    3
+
+# move-pane -X/-Y with border: border lands at the given column/row, content
+# is one cell inside. -X 5 -> pane_left 6; -Y 1 -> pane_top 2.
+$TMUX move-pane -t "$id" -X 5 || fail "move-pane -X 5 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')" 6
+$TMUX move-pane -t "$id" -Y 1 || fail "move-pane -Y 1 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"  2
+# 25% of 80 = 20, 20+1 = 21; 25% of 24 = 6, 6+1 = 7.
+$TMUX move-pane -t "$id" -X 25% || fail "move-pane -X 25% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')" 21
+$TMUX move-pane -t "$id" -Y 25% || fail "move-pane -Y 25% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"  7
+$TMUX kill-pane -t "$id" || exit 1
+
+# --- -B none ---
+
+# Without a border all values are used directly.
+id=$($TMUX new-pane -dPF '#{pane_id}' -B none -x 20 -y 6 -X 8 -Y 3 'sleep 100') \
+	|| fail "new-pane -B none with explicit geometry failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')"  20
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 6
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')"   8
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"    3
+
+# resize-pane without border: size used directly.
+$TMUX resize-pane -t "$id" -x 30 || fail "resize-pane -x 30 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')" 30
+$TMUX resize-pane -t "$id" -y 10 || fail "resize-pane -y 10 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 10
+
+# resize-pane with percentage, no border: 75% of 80 = 60; 75% of 24 = 18.
+$TMUX resize-pane -t "$id" -x 75% || fail "resize-pane -x 75% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')" 60
+$TMUX resize-pane -t "$id" -y 75% || fail "resize-pane -y 75% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 18
+$TMUX kill-pane -t "$id" || exit 1
+
+# Percentage geometry without border: 50% of 80 = 40; 10% of 80 = 8 etc.
+id=$($TMUX new-pane -dPF '#{pane_id}' -B none -x 50% -y 50% -X 10% -Y 10% 'sleep 100') \
+	|| fail "new-pane -B none with percentage geometry failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')"  40
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 12
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')"   8
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"    2
+
+# move-pane without border: -X/-Y set the content position directly.
+# -X 5 -> pane_left 5; -Y 1 -> pane_top 1.
+$TMUX move-pane -t "$id" -X 5 || fail "move-pane -X 5 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')" 5
+$TMUX move-pane -t "$id" -Y 1 || fail "move-pane -Y 1 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"  1
+# 25% of 80 = 20; 25% of 24 = 6.
+$TMUX move-pane -t "$id" -X 25% || fail "move-pane -X 25% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')" 20
+$TMUX move-pane -t "$id" -Y 25% || fail "move-pane -Y 25% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"  6
+$TMUX kill-pane -t "$id" || exit 1
+
+# --- Window option pane-border-lines none ---
+
+$TMUX set-option -w pane-border-lines none || exit 1
+
+# Inherits none from window option: same behaviour as -B none.
+id=$($TMUX new-pane -dPF '#{pane_id}' -x 20 -y 6 -X 8 -Y 3 'sleep 100') \
+	|| fail "new-pane with window pane-border-lines none failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')"  20
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 6
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')"   8
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"    3
+
+$TMUX resize-pane -t "$id" -x 30 || fail "resize-pane -x 30 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')" 30
+$TMUX resize-pane -t "$id" -y 10 || fail "resize-pane -y 10 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 10
+
+$TMUX resize-pane -t "$id" -x 75% || fail "resize-pane -x 75% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')" 60
+$TMUX resize-pane -t "$id" -y 75% || fail "resize-pane -y 75% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 18
+$TMUX kill-pane -t "$id" || exit 1
+
+id=$($TMUX new-pane -dPF '#{pane_id}' -x 50% -y 50% -X 10% -Y 10% 'sleep 100') \
+	|| fail "new-pane with window pane-border-lines none and percentages failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_width}')"  40
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_height}')" 12
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')"   8
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"    2
+
+# move-pane with window pane-border-lines none: same behaviour as -B none.
+$TMUX move-pane -t "$id" -X 5 || fail "move-pane -X 5 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')" 5
+$TMUX move-pane -t "$id" -Y 1 || fail "move-pane -Y 1 failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"  1
+$TMUX move-pane -t "$id" -X 25% || fail "move-pane -X 25% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_left}')" 20
+$TMUX move-pane -t "$id" -Y 25% || fail "move-pane -Y 25% failed"
+must_equal "$($TMUX display-message -p -t "$id" '#{pane_top}')"  6
+$TMUX kill-pane -t "$id" || exit 1
+
+# --- Invalid sizes ---
+
+# Zero width and height must be rejected by new-pane with the default border.
+$TMUX set-option -w -u pane-border-lines || exit 1
+must_fail $TMUX new-pane -d -x 0 -y 6 -X 8 -Y 3 'sleep 100'
+must_fail $TMUX new-pane -d -x 20 -y 0 -X 8 -Y 3 'sleep 100'
+
+# Zero width and height must be rejected by resize-pane.
+id=$($TMUX new-pane -dPF '#{pane_id}' -x 20 -y 6 -X 8 -Y 3 'sleep 100') \
+	|| fail "new-pane for resize-pane invalid size tests failed"
+must_fail $TMUX resize-pane -t "$id" -x 0
+must_fail $TMUX resize-pane -t "$id" -y 0
+$TMUX kill-pane -t "$id" || exit 1
+
+# Same rejections apply with no border.
+$TMUX set-option -w pane-border-lines none || exit 1
+must_fail $TMUX new-pane -d -x 0 -y 6 -X 8 -Y 3 'sleep 100'
+must_fail $TMUX new-pane -d -x 20 -y 0 -X 8 -Y 3 'sleep 100'
+
+id=$($TMUX new-pane -dPF '#{pane_id}' -x 20 -y 6 -X 8 -Y 3 'sleep 100') \
+	|| fail "new-pane for resize-pane invalid size tests (no border) failed"
+must_fail $TMUX resize-pane -t "$id" -x 0
+must_fail $TMUX resize-pane -t "$id" -y 0
+$TMUX kill-pane -t "$id" || exit 1
+
+$TMUX kill-server 2>/dev/null
+exit 0