diff --git a/regress/server-access.sh b/regress/server-access.sh
new file mode 100644
index 000000000..a6e44efca
--- /dev/null
+++ b/regress/server-access.sh
@@ -0,0 +1,112 @@
+#!/bin/sh
+
+# Exercise the unprivileged server-access surface: user and group ACL entries,
+# read-only/writable transitions, listing, removal, implied addition, and
+# command errors. Actual connections from another UID require privileges and
+# deliberately do not form part of this test.
+
+PATH=/bin:/usr/bin
+TERM=screen
+export PATH TERM
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+OUT=$(mktemp) || exit 1
+
+fail()
+{
+	echo "$*" >&2
+	exit 1
+}
+
+cleanup()
+{
+	$TMUX kill-server 2>/dev/null
+	rm -f "$OUT"
+}
+trap cleanup 0 1 15
+
+expect_fail()
+{
+	message=$1
+	shift
+	if $TMUX "$@" >"$OUT" 2>&1; then
+		fail "$message: command unexpectedly succeeded"
+	fi
+}
+
+assert_entry()
+{
+	entry=$1
+	$TMUX server-access -l >"$OUT" || exit 1
+	grep -Fxq "$entry" "$OUT" ||
+		fail "missing ACL entry '$entry'"
+}
+
+assert_no_entry()
+{
+	entry=$1
+	$TMUX server-access -l >"$OUT" || exit 1
+	if grep -Fxq "$entry" "$OUT"; then
+		fail "unexpected ACL entry '$entry'"
+	fi
+}
+
+owner_uid=$(id -u)
+owner_name=$(id -un)
+
+# nobody is the non-owner test identity. Derive its primary group rather than
+# assuming whether the system calls it nobody, nogroup, or something else.
+acl_user=nobody
+acl_group=$(id -gn "$acl_user" 2>/dev/null) ||
+	fail "the nobody account is unavailable"
+[ "$owner_name" != "$acl_user" ] || fail "test cannot run as nobody"
+
+$TMUX new-session -d -s access 'exec sleep 100' || exit 1
+
+# The owner is installed as writable at server startup (root is intentionally
+# omitted from display output).
+if [ "$owner_uid" != 0 ]; then
+	assert_entry "$owner_name (U,W)"
+fi
+
+# User ACL lifecycle, including duplicate and missing-entry errors.
+$TMUX server-access -a "$acl_user" || exit 1
+assert_entry "$acl_user (U,W)"
+expect_fail "duplicate user addition" server-access -a "$acl_user"
+$TMUX server-access -r "$acl_user" || exit 1
+assert_entry "$acl_user (U,R)"
+$TMUX server-access -w "$acl_user" || exit 1
+assert_entry "$acl_user (U,W)"
+$TMUX server-access -d "$acl_user" || exit 1
+assert_no_entry "$acl_user (U,W)"
+expect_fail "removing absent user" server-access -d "$acl_user"
+
+# -r and -w imply -a when an entry is absent.
+$TMUX server-access -r "$acl_user" || exit 1
+assert_entry "$acl_user (U,R)"
+$TMUX server-access -d "$acl_user" || exit 1
+
+# The same lifecycle for a group exercises the separate ACL key space.
+$TMUX server-access -g -a -r "$acl_group" || exit 1
+assert_entry "$acl_group (G,R)"
+$TMUX server-access -g -w "$acl_group" || exit 1
+assert_entry "$acl_group (G,W)"
+expect_fail "duplicate group addition" server-access -g -a "$acl_group"
+$TMUX server-access -g -d "$acl_group" || exit 1
+assert_no_entry "$acl_group (G,W)"
+expect_fail "removing absent group" server-access -g -d "$acl_group"
+
+# Parser and lookup errors, plus the immutable owner/root entries.
+expect_fail "missing ACL subject" server-access -a
+expect_fail "unknown user" server-access -a "tmux-no-user-$$"
+expect_fail "unknown group" server-access -g -a "tmux-no-group-$$"
+expect_fail "conflicting add/delete" server-access -a -d "$acl_user"
+expect_fail "conflicting read/write" server-access -r -w "$acl_user"
+expect_fail "changing server owner" server-access -r "$owner_name"
+if [ "$owner_name" != root ]; then
+	expect_fail "changing root access" server-access -a root
+fi
+
+$TMUX has-session -t access || fail "server exited during ACL updates"
+exit 0
diff --git a/regress/switch-mode.sh b/regress/switch-mode.sh
new file mode 100644
index 000000000..5f3fe8c12
--- /dev/null
+++ b/regress/switch-mode.sh
@@ -0,0 +1,203 @@
+#!/bin/sh
+
+# Exercise switch-mode's session and window lists with a real attached client:
+# fuzzy filtering, movement and selection, the default and custom commands,
+# no-match cancellation, resize, zoom restoration, and -k mode teardown.
+
+PATH=/bin:/usr/bin
+TERM=screen
+LC_ALL=C.UTF-8
+export PATH TERM LC_ALL
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+DIR=$(mktemp -d) || exit 1
+TMUX_TMPDIR=$DIR
+export TMUX_TMPDIR
+INNER="$TEST_TMUX -LtestI$$ -f/dev/null"
+OUTER="$TEST_TMUX -LtestO$$ -f/dev/null"
+
+fail()
+{
+	echo "$*" >&2
+	exit 1
+}
+
+cleanup()
+{
+	$OUTER kill-server 2>/dev/null
+	$INNER kill-server 2>/dev/null
+	rm -rf "$DIR"
+}
+trap cleanup 0 1 15
+
+capture()
+{
+	$OUTER capture-pane -p -t outer:0.0 2>/dev/null
+}
+
+wait_capture()
+{
+	marker=$1
+	i=0
+	while [ "$i" -lt 50 ]; do
+		captured=$(capture)
+		printf '%s\n' "$captured" | grep -Fq "$marker" && return 0
+		sleep 0.1
+		i=$((i + 1))
+	done
+	fail "timed out waiting for '$marker'"
+}
+
+wait_count()
+{
+	marker=$1
+	want=$2
+	i=0
+	while [ "$i" -lt 50 ]; do
+		captured=$(capture)
+		count=$(printf '%s\n' "$captured" | grep -Fc "$marker")
+		[ "$count" -eq "$want" ] && return 0
+		sleep 0.1
+		i=$((i + 1))
+	done
+	fail "found $count '$marker' rows, expected $want"
+}
+
+wait_format()
+{
+	target=$1
+	format=$2
+	want=$3
+	i=0
+	while [ "$i" -lt 50 ]; do
+		got=$($INNER display-message -p -t "$target" "$format" \
+		    2>/dev/null)
+		[ "$got" = "$want" ] && return 0
+		sleep 0.1
+		i=$((i + 1))
+	done
+	fail "$target format $format is '$got', expected '$want'"
+}
+
+wait_client_session()
+{
+	want=$1
+	i=0
+	while [ "$i" -lt 50 ]; do
+		got=$($INNER list-clients -F '#{client_session}' 2>/dev/null)
+		[ "$got" = "$want" ] && return 0
+		sleep 0.1
+		i=$((i + 1))
+	done
+	fail "client session is '$got', expected '$want'"
+}
+
+# Three alphabetically ordered sessions. alpha:main has two panes so -Z can be
+# observed; the two pick-* windows make a deterministic two-row window filter.
+$INNER new-session -d -s alpha -n main -x60 -y15 'exec sleep 100' || exit 1
+$INNER split-window -d -h -t alpha:main 'exec sleep 100' || exit 1
+$INNER new-window -d -t alpha: -n pick-one 'exec sleep 100' || exit 1
+$INNER new-session -d -s bravo -n pick-two -x60 -y15 \
+	'exec sleep 100' || exit 1
+$INNER new-session -d -s charlie -n last -x60 -y15 \
+	'exec sleep 100' || exit 1
+$INNER set-option -g status off || exit 1
+$INNER set-option -g window-size manual || exit 1
+$INNER select-window -t alpha:main || exit 1
+
+$OUTER new-session -d -s outer -x60 -y15 "$INNER attach -t alpha" || exit 1
+$OUTER set-option -g status off || exit 1
+$OUTER set-option -g window-size manual || exit 1
+wait_client_session alpha
+
+# Session rows are sorted alpha, bravo, charlie. Up from the first row wraps to
+# charlie; Enter runs a custom command with the selected session target.
+$INNER set-option -g @picked '' || exit 1
+$INNER switch-mode -s -t alpha:main.0 -F 'SESSION #{session_name}' \
+	"set-option -g @picked '%%'" || exit 1
+wait_count 'SESSION ' 3
+$INNER send-keys -t alpha:main.0 Up Enter || exit 1
+wait_format alpha:main.0 '#{@picked}' '=charlie:'
+wait_format alpha:main.0 '#{pane_in_mode}' 0
+
+# Fuzzy filtering keeps only bravo for "brv". The default command switches the
+# real client to that session and closes the mode.
+$INNER switch-mode -s -t alpha:main.0 -F 'SESSION #{session_name}' || exit 1
+wait_count 'SESSION ' 3
+$INNER send-keys -t alpha:main.0 -l brv || exit 1
+wait_count 'SESSION ' 1
+printf '%s\n' "$captured" | grep -Fq 'SESSION bravo' ||
+	fail "fuzzy session filter did not select bravo"
+$INNER send-keys -t alpha:main.0 Enter || exit 1
+wait_client_session bravo
+client=$($INNER list-clients -F '#{client_name}')
+$INNER switch-client -c "$client" -t alpha || exit 1
+wait_client_session alpha
+
+# Window mode sees pick-one then pick-two for the "pick" filter. Down selects
+# the second row, and the custom command receives its window target.
+$INNER set-option -g @picked '' || exit 1
+$INNER switch-mode -w -t alpha:main.0 -F \
+	'WINDOW #{session_name}:#{window_name}' \
+	"set-option -g @picked '%%'" || exit 1
+wait_capture 'WINDOW '
+$INNER send-keys -t alpha:main.0 -l pick || exit 1
+wait_count 'WINDOW ' 2
+$INNER send-keys -t alpha:main.0 Down Enter || exit 1
+picked=$($INNER show-option -gv @picked)
+case "$picked" in
+=bravo:0.) ;;
+*) fail "window selection produced '$picked', expected '=bravo:0.'" ;;
+esac
+
+# Navigation with an empty result set must be harmless, and Escape cancels
+# without running the custom command.
+$INNER set-option -g @picked unchanged || exit 1
+$INNER switch-mode -s -t alpha:main.0 -F 'NONE #{session_name}' \
+	"set-option -g @picked '%%'" || exit 1
+wait_capture 'NONE '
+$INNER send-keys -t alpha:main.0 -l no-such-session || exit 1
+wait_count 'NONE ' 0
+$INNER send-keys -t alpha:main.0 Up Down PPage NPage Home End || exit 1
+wait_format alpha:main.0 '#{pane_mode}' switch-mode
+$INNER send-keys -t alpha:main.0 Escape || exit 1
+wait_format alpha:main.0 '#{pane_in_mode}' 0
+[ "$($INNER show-option -gv @picked)" = unchanged ] ||
+	fail "cancelled switch-mode ran its command"
+
+# -Z temporarily zooms an unzoomed window. Resizing while the mode is open
+# rebuilds and redraws it; exiting restores the original unzoomed state.
+$INNER switch-mode -Zs -t alpha:main.0 -F 'RESIZE #{session_name}' || exit 1
+wait_capture 'RESIZE alpha'
+wait_format alpha:main.0 '#{window_zoomed_flag}' 1
+$INNER resize-window -t alpha:main -x50 -y12 || exit 1
+wait_format alpha:main.0 '#{window_width}x#{window_height}' 50x12
+wait_format alpha:main.0 '#{pane_mode}' switch-mode
+$INNER send-keys -t alpha:main.0 Escape || exit 1
+wait_format alpha:main.0 '#{window_zoomed_flag}' 0
+
+# If the window was already zoomed, leaving -Z mode must keep it zoomed.
+$INNER resize-pane -Z -t alpha:main.0 || exit 1
+$INNER switch-mode -Zs -t alpha:main.0 -F 'ZOOMED #{session_name}' || exit 1
+wait_capture 'ZOOMED alpha'
+$INNER send-keys -t alpha:main.0 Escape || exit 1
+wait_format alpha:main.0 '#{window_zoomed_flag}' 1
+$INNER resize-pane -Z -t alpha:main.0 || exit 1
+
+# -k uses the shared mode teardown flag. Put it on a disposable pane and make
+# sure exiting the mode removes that pane.
+kill_pane=$($INNER split-window -d -P -F '#{pane_id}' -t alpha:main \
+	'exec sleep 100') || exit 1
+$INNER switch-mode -ks -t "$kill_pane" -F 'KILL #{session_name}' || exit 1
+wait_format "$kill_pane" '#{pane_mode}' switch-mode
+$INNER send-keys -t "$kill_pane" Escape || exit 1
+i=0
+while [ "$i" -lt 50 ]; do
+	$INNER list-panes -s -t alpha -F '#{pane_id}' 2>/dev/null | \
+	    grep -q -x "$kill_pane" || break
+	sleep 0.1
+	i=$((i + 1))
+done
+[ "$i" -lt 50 ] || fail "switch-mode -k did not kill its pane"
+
+exit 0