diff --git a/regress/pane-states.sh b/regress/pane-states.sh
new file mode 100644
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--- /dev/null
+++ b/regress/pane-states.sh
@@ -0,0 +1,404 @@
+#!/bin/sh
+
+# Combinations of tiled, floating, zoomed and hidden panes.
+#
+# Every pane is tiled or floating, zoomed or not, and hidden or not, and these
+# are independent. For each combination of those states for two panes (and for
+# three), each pane command that changes or depends on them is run and the
+# result is compared with what the command should do, using awk to work out the
+# expectation from the state before. This covers:
+# - select-pane, including -Z and moving to the next, last or a directional pane;
+# - resize-pane -Z (toggle a zoom), -H (hide or show), -a -Z (unzoom all) and
+#   -a -H (show desktop), which is run twice to check it restores the panes;
+# - break-pane -W and join-pane to float and tile panes;
+# - split-window, new-pane and kill-pane;
+# - next-layout, select-layout, rotate-window and resize-window.
+#
+# It also checks properties that must hold after every command: the active pane
+# is not hidden if any pane is not, there is one active pane, a window with one
+# pane is not zoomed, window_zoomed_flag matches the panes and visible panes have
+# a size. The status line clicks and the cursor are in other tests.
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+SOCK=testA$$
+RUN=0
+
+tm()
+{
+	$TEST_TMUX -L"$SOCK$RUN" -f/dev/null "$@"
+}
+
+cleanup()
+{
+	tm kill-server >/dev/null 2>&1
+}
+trap cleanup 0
+trap 'exit 1' 1 2 15
+
+FMT='#{pane_id} #{pane_floating_flag} #{pane_zoomed_flag} #{pane_hidden_flag} #{pane_active} #{pane_width} #{pane_height} #{window_zoomed_flag}'
+
+# The oracle. The state before is on lines starting B and the state after on
+# lines starting A: id floating zoomed hidden active width height window_zoomed.
+# op is the operation, tgt the target pane, rc the exit status of the command and
+# mode is "setup" to check that the start state was made as wanted, with want
+# holding floating, zoomed and hidden for each pane in order.
+ORACLE='
+function fail(msg)
+{
+	printf "%s %s (exit %s): %s\n", op, tgt, rc, msg
+	bad = 1
+	exit 1
+}
+function sameF(skip,    i, id)
+{
+	for (i = 1; i <= nb; i++) {
+		id = bid[i]
+		if (id == skip || !(id in ina))
+			continue
+		if (aF[id] != bF[id])
+			fail("pane " id " floating " bF[id] " became " aF[id])
+	}
+}
+function sameZ(skip,    i, id)
+{
+	for (i = 1; i <= nb; i++) {
+		id = bid[i]
+		if (id == skip || !(id in ina))
+			continue
+		if (aZ[id] != bZ[id])
+			fail("pane " id " zoomed " bZ[id] " became " aZ[id])
+	}
+}
+function sameH(skip,    i, id)
+{
+	for (i = 1; i <= nb; i++) {
+		id = bid[i]
+		if (id == skip || !(id in ina))
+			continue
+		if (aH[id] != bH[id])
+			fail("pane " id " hidden " bH[id] " became " aH[id])
+	}
+}
+function noZoom(    i)
+{
+	for (i = 1; i <= na; i++) {
+		if (aZ[aid[i]])
+			fail("pane " aid[i] " is still zoomed")
+	}
+}
+function covered(t,    i, q)
+{
+	if (bF[t] || bZ[t])
+		return 0
+	for (i = 1; i <= nb; i++) {
+		q = bid[i]
+		if (q != t && bZ[q] && !bH[q])
+			return 1
+	}
+	return 0
+}
+function newPane(    i, k, id)
+{
+	k = 0
+	for (i = 1; i <= na; i++) {
+		id = aid[i]
+		if (!(id in inb)) {
+			k++
+			created = id
+		}
+	}
+	if (k != 1)
+		fail(k " new panes, expected 1")
+	if (na != nb + 1)
+		fail("pane count " nb " became " na)
+}
+$1 == "B" {
+	nb++; id = $2; bid[nb] = id; inb[id] = 1
+	bF[id] = $3; bZ[id] = $4; bH[id] = $5; bA[id] = $6
+}
+$1 == "A" {
+	na++; id = $2; aid[na] = id; ina[id] = 1
+	aF[id] = $3; aZ[id] = $4; aH[id] = $5; aA[id] = $6
+	aW[id] = $7; aT[id] = $8; aWZ[id] = $9
+}
+END {
+	if (mode == "setup") {
+		split(want, w, " ")
+		for (i = 1; i <= nb; i++) {
+			id = bid[i]; p = substr(id, 2) + 0
+			if (bF[id] != w[3 * p + 1] || bZ[id] != w[3 * p + 2] ||
+			    bH[id] != w[3 * p + 3])
+				fail("pane " id " is " bF[id] bZ[id] bH[id] ", wanted " \
+				    w[3 * p + 1] w[3 * p + 2] w[3 * p + 3])
+		}
+		exit 0
+	}
+
+	# Properties of any state.
+	if (na < 1)
+		fail("no panes left")
+	nact = 0; anyZ = 0; anyvis = 0
+	for (i = 1; i <= na; i++) {
+		id = aid[i]
+		if (aA[id] == 1) { nact++; act = id }
+		if (aZ[id]) anyZ = 1
+		if (!aH[id]) anyvis = 1
+	}
+	if (nact != 1)
+		fail(nact " active panes")
+	for (i = 1; i <= na; i++) {
+		id = aid[i]
+		if (aWZ[id] != anyZ)
+			fail("window_zoomed_flag " aWZ[id] " with zoomed panes " anyZ)
+		if (!aH[id] && (aW[id] < 1 || aT[id] < 1))
+			fail("pane " id " is " aW[id] "x" aT[id])
+	}
+	if (na == 1 && anyZ)
+		fail("the only pane is zoomed")
+	if (anyvis && aH[act])
+		fail("active pane " act " is hidden but others are not")
+
+	# A command that failed changed nothing.
+	if (rc != 0) {
+		if (na != nb)
+			fail("pane count " nb " became " na)
+		sameF(""); sameZ(""); sameH("")
+		exit 0
+	}
+
+	T = tgt
+	if (op == "select") {
+		if (aA[T] != 1) fail("not active")
+		if (aH[T]) fail("still hidden")
+		if (covered(T)) noZoom(); else sameZ("")
+		sameF(""); sameH(T)
+	} else if (op == "zoom") {
+		sameF("")
+		if (bZ[T]) {
+			if (aZ[T]) fail("not unzoomed")
+			sameZ(T); sameH("")
+		} else {
+			if (!aZ[T]) fail("not zoomed")
+			if (aH[T]) fail("zoomed pane is hidden")
+			if (aA[T] != 1) fail("zoomed pane is not active")
+			sameZ(T); sameH(T)
+		}
+	} else if (op == "hide") {
+		sameF("")
+		if (bH[T]) {
+			if (aH[T]) fail("not shown")
+			if (aA[T] != 1) fail("not active when shown")
+			if (covered(T)) noZoom(); else sameZ("")
+		} else {
+			if (!aH[T]) fail("not hidden")
+			sameZ("")
+		}
+		sameH(T)
+	} else if (op == "desktop") {
+		sameF(""); sameZ("")
+		for (i = 1; i <= nb; i++) {
+			id = bid[i]
+			want = (bH[id] + bF[id] + bZ[id] > 0) ? 1 : 0
+			if (aH[id] != want)
+				fail("pane " id " hidden " bH[id] " floating " bF[id] \
+				    " zoomed " bZ[id] " became hidden " aH[id])
+		}
+	} else if (op == "desktop2") {
+		sameF(""); sameZ(""); sameH("")
+	} else if (op == "unzoomall") {
+		sameF(""); sameH(""); noZoom()
+	} else if (op == "break") {
+		if (bF[T] || !aF[T]) fail("not floated")
+		sameF(T); sameZ(""); sameH("")
+	} else if (op == "join") {
+		if (!bF[T] || aF[T]) fail("not tiled")
+		sameF(T); sameZ(""); sameH("")
+	} else if (op == "kill") {
+		if (T in ina) fail("not killed")
+		if (na != nb - 1) fail("pane count " nb " became " na)
+		sameF(T); sameH(T)
+		if (na == 1) noZoom(); else sameZ(T)
+	} else if (op == "split") {
+		newPane()
+		if (aF[created] != bF[T]) fail("new pane floating " aF[created])
+		if (aZ[created] || aH[created]) fail("new pane zoomed or hidden")
+		sameF(""); sameZ("")
+		if (bH[T] && !bF[T]) {
+			if (aH[T]) fail("tiled target not shown")
+			sameH(T)
+		} else
+			sameH("")
+	} else if (op == "newpane") {
+		newPane()
+		if (!aF[created]) fail("new pane is not floating")
+		if (aZ[created] || aH[created]) fail("new pane zoomed or hidden")
+		sameF(""); sameZ(""); sameH("")
+	} else if (op == "nextlayout" || op == "tiled") {
+		sameF(""); sameH(""); noZoom()
+	} else {
+		# Moving around or changing layout: floating panes stay floating
+		# and nothing is hidden.
+		sameF("")
+		for (i = 1; i <= nb; i++) {
+			id = bid[i]
+			if (id in ina && aH[id] > bH[id])
+				fail("pane " id " was hidden by this")
+		}
+	}
+	exit 0
+}
+'
+
+# describe N STATE: print the start state in words.
+describe()
+{
+	n=$1
+	s=$2
+	i=0
+	out=
+	while [ $i -lt "$n" ]; do
+		bits=$(( (s >> (3 * i)) & 7 ))
+		k=T
+		[ $((bits & 1)) -ne 0 ] && k=F
+		z=
+		[ $((bits & 2)) -ne 0 ] && z=z
+		h=
+		[ $((bits & 4)) -ne 0 ] && h=h
+		out="$out %$i=$k$z$h"
+		i=$((i + 1))
+	done
+	echo "$out"
+}
+
+# run_one N STATE OP TARGET: set up the state, run the operation, check it.
+run_one()
+{
+	n=$1
+	s=$2
+	op=$3
+	tgt=$4
+	RUN=$((RUN + 1))
+
+	set -- new-session -d -x 80 -y 24 cat
+	i=1
+	while [ $i -lt "$n" ]; do
+		set -- "$@" ';' split-window -d ''
+		i=$((i + 1))
+	done
+	want=
+	for stage in 1 2 4; do
+		i=0
+		while [ $i -lt "$n" ]; do
+			bits=$(( (s >> (3 * i)) & 7 ))
+			if [ $((bits & stage)) -ne 0 ]; then
+				case $stage in
+				1) set -- "$@" ';' break-pane -d -W -s "%$i" ;;
+				2) set -- "$@" ';' resize-pane -Z -t "%$i" ;;
+				4) set -- "$@" ';' resize-pane -H -t "%$i" ;;
+				esac
+			fi
+			i=$((i + 1))
+		done
+	done
+	i=0
+	while [ $i -lt "$n" ]; do
+		bits=$(( (s >> (3 * i)) & 7 ))
+		want="$want $((bits & 1)) $(((bits >> 1) & 1)) $(((bits >> 2) & 1))"
+		i=$((i + 1))
+	done
+	set -- "$@" ';' list-panes -F "B $FMT"
+	before=$(tm "$@" 2>&1)
+	if ! msg=$(echo "$before" | awk -v mode=setup -v want="$want" \
+	    -v op=setup -v tgt=- -v rc=0 "$ORACLE" 2>&1); then
+		echo "setup of $(describe "$n" "$s") failed: $msg"
+		echo "$before"
+		cleanup
+		exit 1
+	fi
+
+	p="-t $tgt"
+	rc=0
+	case $op in
+	select) tm select-pane -t "$tgt" || rc=$? ;;
+	selectZ) tm select-pane -Z -t "$tgt" || rc=$? ;;
+	zoom) tm resize-pane -Z -t "$tgt" || rc=$? ;;
+	hide) tm resize-pane -H -t "$tgt" || rc=$? ;;
+	break) tm break-pane -d -W -s "$tgt" || rc=$? ;;
+	join) tm join-pane -d -s "$tgt" -t "$tgt" || rc=$? ;;
+	kill) tm kill-pane -t "$tgt" || rc=$? ;;
+	split) tm split-window -d -t "$tgt" '' || rc=$? ;;
+	newpane) tm new-pane -d -t "$tgt" -x 20 -y 6 '' || rc=$? ;;
+	desktop) tm resize-pane -a -H -t %0 || rc=$? ;;
+	desktop2)
+		tm resize-pane -a -H -t %0 || rc=$?
+		tm resize-pane -a -H -t %0 || rc=$?
+		;;
+	unzoomall) tm resize-pane -a -Z -t %0 || rc=$? ;;
+	nextlayout) tm next-layout -t %0 || rc=$? ;;
+	tiled) tm select-layout -t %0 tiled || rc=$? ;;
+	rotate) tm rotate-window -t %0 || rc=$? ;;
+	nextpane) tm select-pane -t :.+ || rc=$? ;;
+	lastpane) tm last-pane -t %0 || rc=$? ;;
+	left) tm select-pane -L || rc=$? ;;
+	right) tm select-pane -R || rc=$? ;;
+	up) tm select-pane -U || rc=$? ;;
+	down) tm select-pane -D || rc=$? ;;
+	resize) tm resize-window -t %0 -x 50 -y 14 || rc=$? ;;
+	*) echo "unknown operation $op"; exit 1 ;;
+	esac >/dev/null 2>&1
+
+	after=$(tm list-panes -F "A $FMT" 2>&1)
+	result=$( (echo "$before"; echo "$after") |
+	    awk -v mode=check -v op="$op" -v tgt="$tgt" -v rc="$rc" "$ORACLE")
+	if [ $? -ne 0 ] || [ -n "$result" ]; then
+		echo "FAILED with $n panes, start $(describe "$n" "$s"):"
+		echo "  $result"
+		echo "before:"; echo "$before" | sed 's/^/  /'
+		echo "after:"; echo "$after" | sed 's/^/  /'
+		cleanup
+		exit 1
+	fi
+	cleanup
+}
+
+PER_PANE="select selectZ zoom hide break join kill split newpane"
+GLOBAL="desktop desktop2 unzoomall nextlayout tiled rotate nextpane lastpane \
+    left right up down resize"
+
+# Two panes: every state, every operation.
+s=0
+while [ $s -lt 64 ]; do
+	for op in $GLOBAL; do
+		run_one 2 $s "$op" %0
+	done
+	for op in $PER_PANE; do
+		run_one 2 $s "$op" %0
+		run_one 2 $s "$op" %1
+	done
+	s=$((s + 1))
+done
+
+# Three panes: every state, and one operation on each, rotating so that every
+# operation and target is used with many different states.
+ALL="$GLOBAL"
+for op in $PER_PANE; do
+	ALL="$ALL $op:0 $op:1 $op:2"
+done
+set -- $ALL
+M=$#
+s=0
+while [ $s -lt 512 ]; do
+	set -- $ALL
+	shift $(( (s * 7 + s / M) % M ))
+	item=$1
+	case $item in
+	*:*) run_one 3 $s "${item%:*}" "%${item#*:}" ;;
+	*) run_one 3 $s "$item" %0 ;;
+	esac
+	s=$((s + 1))
+done
+
+exit 0