diff --git a/regress/alerts.sh b/regress/alerts.sh
index 7a39ddefc..cfb84c711 100644
--- a/regress/alerts.sh
+++ b/regress/alerts.sh
@@ -19,7 +19,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/am-terminal.sh b/regress/am-terminal.sh
index bf1cabfe7..fae0e502d 100644
--- a/regress/am-terminal.sh
+++ b/regress/am-terminal.sh
@@ -4,9 +4,9 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 $TMUX2 kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/border-arrows.sh b/regress/border-arrows.sh
index ea571b05a..a67171bf5 100644
--- a/regress/border-arrows.sh
+++ b/regress/border-arrows.sh
@@ -11,9 +11,9 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-TMUX_OUTER="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX_OUTER="$TEST_TMUX -LtestB$$ -f/dev/null"
 $TMUX_OUTER kill-server 2>/dev/null
 
 trap "$TMUX kill-server 2>/dev/null; $TMUX_OUTER kill-server 2>/dev/null" 0 1 15
diff --git a/regress/buffers.sh b/regress/buffers.sh
index 0b3267610..fdacacb5b 100644
--- a/regress/buffers.sh
+++ b/regress/buffers.sh
@@ -23,7 +23,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/capture-pane-hyperlink.sh b/regress/capture-pane-hyperlink.sh
index 80092e7f2..ec89c6c5d 100644
--- a/regress/capture-pane-hyperlink.sh
+++ b/regress/capture-pane-hyperlink.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 TMP=$(mktemp)
 TMP2=$(mktemp)
 trap "rm -f $TMP $TMP2" 0 1 15
diff --git a/regress/capture-pane-sgr0.sh b/regress/capture-pane-sgr0.sh
index 7c9c32315..1e73e7191 100644
--- a/regress/capture-pane-sgr0.sh
+++ b/regress/capture-pane-sgr0.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/check-names.sh b/regress/check-names.sh
index 886299f2d..be8ad617b 100644
--- a/regress/check-names.sh
+++ b/regress/check-names.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 fail()
diff --git a/regress/choose-buffer.sh b/regress/choose-buffer.sh
index 60f15478f..ca9a26758 100644
--- a/regress/choose-buffer.sh
+++ b/regress/choose-buffer.sh
@@ -20,8 +20,8 @@ TERM=screen
 TMP=$(mktemp -d) || exit 1
 TMUX_TMPDIR="$TMP"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
diff --git a/regress/choose-client.sh b/regress/choose-client.sh
index 621cb608f..d325f5335 100644
--- a/regress/choose-client.sh
+++ b/regress/choose-client.sh
@@ -19,8 +19,8 @@ TERM=screen
 TMP=$(mktemp -d) || exit 1
 TMUX_TMPDIR="$TMP"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
diff --git a/regress/choose-tree.sh b/regress/choose-tree.sh
index 8346b4cae..132890730 100644
--- a/regress/choose-tree.sh
+++ b/regress/choose-tree.sh
@@ -27,8 +27,8 @@ TERM=screen
 TMP=$(mktemp -d) || exit 1
 TMUX_TMPDIR="$TMP"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
diff --git a/regress/combine-test.sh b/regress/combine-test.sh
index a4d4f3681..ac9f800b0 100644
--- a/regress/combine-test.sh
+++ b/regress/combine-test.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/command-alias.sh b/regress/command-alias.sh
index 632e959a2..aae434cc0 100644
--- a/regress/command-alias.sh
+++ b/regress/command-alias.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 $TMUX new-session -d -sfoo || exit 1
diff --git a/regress/command-order.sh b/regress/command-order.sh
index 775768a6a..9c957246a 100644
--- a/regress/command-order.sh
+++ b/regress/command-order.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/conf-syntax.sh b/regress/conf-syntax.sh
index 49b9710b3..4dbc384b3 100644
--- a/regress/conf-syntax.sh
+++ b/regress/conf-syntax.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 for i in conf/*.conf; do
diff --git a/regress/control-client-sanity.sh b/regress/control-client-sanity.sh
index f6c36e1bd..32695e7c0 100644
--- a/regress/control-client-sanity.sh
+++ b/regress/control-client-sanity.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/control-client-size.sh b/regress/control-client-size.sh
index 7d5e1dc27..e6742608a 100644
--- a/regress/control-client-size.sh
+++ b/regress/control-client-size.sh
@@ -8,7 +8,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/control-subscriptions.sh b/regress/control-subscriptions.sh
index f720b0650..8aebb2ea0 100644
--- a/regress/control-subscriptions.sh
+++ b/regress/control-subscriptions.sh
@@ -7,7 +7,7 @@ LANG=C.UTF-8
 export TERM LC_ALL LANG
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 TMPDIR=$(mktemp -d)
 IN="$TMPDIR/in"
diff --git a/regress/copy-mode-test-emacs.sh b/regress/copy-mode-test-emacs.sh
index a5b69c675..3e9cbf50b 100644
--- a/regress/copy-mode-test-emacs.sh
+++ b/regress/copy-mode-test-emacs.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 $TMUX new -d -x40 -y10 \
diff --git a/regress/copy-mode-test-vi.sh b/regress/copy-mode-test-vi.sh
index 2d6bfc287..71810b006 100644
--- a/regress/copy-mode-test-vi.sh
+++ b/regress/copy-mode-test-vi.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -f/dev/null -Ltest"
+TMUX="$TEST_TMUX -f/dev/null -LtestA$$"
 $TMUX kill-server 2>/dev/null
 
 $TMUX new -d -x40 -y10 \
diff --git a/regress/cursor-test1.sh b/regress/cursor-test1.sh
index 73a336be7..b098cdc15 100644
--- a/regress/cursor-test1.sh
+++ b/regress/cursor-test1.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/cursor-test2.sh b/regress/cursor-test2.sh
index 3de80fdac..8e9e7ec80 100644
--- a/regress/cursor-test2.sh
+++ b/regress/cursor-test2.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/cursor-test3.sh b/regress/cursor-test3.sh
index e4881c79a..213ed83ba 100644
--- a/regress/cursor-test3.sh
+++ b/regress/cursor-test3.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/cursor-test4.sh b/regress/cursor-test4.sh
index 8f4dfa5c3..0eb5f0c9a 100644
--- a/regress/cursor-test4.sh
+++ b/regress/cursor-test4.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/decrqm-sync.sh b/regress/decrqm-sync.sh
index 7f8c3f61d..f4daf36a9 100644
--- a/regress/decrqm-sync.sh
+++ b/regress/decrqm-sync.sh
@@ -9,7 +9,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 sleep 1
 
diff --git a/regress/environ-update.sh b/regress/environ-update.sh
index 59f7d74c5..44e4e72c4 100644
--- a/regress/environ-update.sh
+++ b/regress/environ-update.sh
@@ -17,9 +17,9 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 # A second server on its own socket hosts the pane that runs the inner client.
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
diff --git a/regress/environ.sh b/regress/environ.sh
index 244ec367d..2d5c0c031 100644
--- a/regress/environ.sh
+++ b/regress/environ.sh
@@ -19,7 +19,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_value $args $expected
@@ -151,7 +151,7 @@ cat > "$CONF" <<EOF
 CFGVAR=fromconfig
 %hidden CFGHID=hiddencfg
 EOF
-CTMUX="$TEST_TMUX -Ltest2 -f$CONF"
+CTMUX="$TEST_TMUX -LtestB$$ -f$CONF"
 $CTMUX kill-server 2>/dev/null
 $CTMUX new-session -d -s c -x 80 -y 24 || { rm -f "$CONF"; exit 1; }
 out=$($CTMUX show-environment -g CFGVAR 2>&1)
diff --git a/regress/floating-pane-geometry.sh b/regress/floating-pane-geometry.sh
index 7bd033ff6..7e80e8942 100644
--- a/regress/floating-pane-geometry.sh
+++ b/regress/floating-pane-geometry.sh
@@ -15,7 +15,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 fail()
diff --git a/regress/format-fuzzy.sh b/regress/format-fuzzy.sh
index 31a5b60cb..00bc28bd4 100644
--- a/regress/format-fuzzy.sh
+++ b/regress/format-fuzzy.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 # test_format $format $expected_result
 test_format()
diff --git a/regress/format-modifiers.sh b/regress/format-modifiers.sh
index 21203b6a9..b6340b622 100644
--- a/regress/format-modifiers.sh
+++ b/regress/format-modifiers.sh
@@ -17,7 +17,7 @@ LC_ALL=C.UTF-8
 export TZ LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 ESC=$(printf '\033')
 
diff --git a/regress/format-mouse.sh b/regress/format-mouse.sh
index 8032f8a57..9a443d19c 100644
--- a/regress/format-mouse.sh
+++ b/regress/format-mouse.sh
@@ -18,8 +18,8 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
diff --git a/regress/format-render-contexts.sh b/regress/format-render-contexts.sh
index de68176e0..2cceff2e3 100644
--- a/regress/format-render-contexts.sh
+++ b/regress/format-render-contexts.sh
@@ -9,8 +9,8 @@ export PATH TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
 
-TMUX="$TEST_TMUX -Lformat-render-contexts-$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Lformat-render-contexts-outer-$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 LIMIT=20000
 
 cleanup()
diff --git a/regress/format-strings.sh b/regress/format-strings.sh
index bae66ab00..877e18fec 100644
--- a/regress/format-strings.sh
+++ b/regress/format-strings.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 # test_format $format $expected_result
 test_format()
diff --git a/regress/format-variables.sh b/regress/format-variables.sh
index fa51e0216..9131c2cf4 100644
--- a/regress/format-variables.sh
+++ b/regress/format-variables.sh
@@ -15,10 +15,10 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 # A second server on its own socket provides a real terminal (an inner client
 # attached inside one of its panes) so client terminal variables are populated.
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 # Every variable name in format_table[].  Kept as a plain word list so it can be
 # iterated with normal shell word splitting.
diff --git a/regress/has-session-return.sh b/regress/has-session-return.sh
index a7d76ad85..8b259ac76 100644
--- a/regress/has-session-return.sh
+++ b/regress/has-session-return.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 $TMUX -f/dev/null has -tfoo </dev/null 2>/dev/null && exit 1
diff --git a/regress/hooks-after.sh b/regress/hooks-after.sh
index ee7fbfe0e..37934db8d 100644
--- a/regress/hooks-after.sh
+++ b/regress/hooks-after.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/hooks-lifecycle.sh b/regress/hooks-lifecycle.sh
index 6fb271131..e90f7ba3a 100644
--- a/regress/hooks-lifecycle.sh
+++ b/regress/hooks-lifecycle.sh
@@ -15,7 +15,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/hooks-notify.sh b/regress/hooks-notify.sh
index 947dd6c68..41916248c 100644
--- a/regress/hooks-notify.sh
+++ b/regress/hooks-notify.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/hooks.sh b/regress/hooks.sh
index 537582295..e1d75bf67 100644
--- a/regress/hooks.sh
+++ b/regress/hooks.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/if-shell-TERM.sh b/regress/if-shell-TERM.sh
index 21846fd10..d1db52f45 100644
--- a/regress/if-shell-TERM.sh
+++ b/regress/if-shell-TERM.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/if-shell-error.sh b/regress/if-shell-error.sh
index 2eab8f7ca..3b2dac753 100644
--- a/regress/if-shell-error.sh
+++ b/regress/if-shell-error.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/if-shell-nested.sh b/regress/if-shell-nested.sh
index 434775c43..e10be41c6 100644
--- a/regress/if-shell-nested.sh
+++ b/regress/if-shell-nested.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/input-common.inc b/regress/input-common.inc
index 96eec1f09..100a7be0f 100644
--- a/regress/input-common.inc
+++ b/regress/input-common.inc
@@ -2,7 +2,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 TMP=$(mktemp)
 EXP=$(mktemp)
diff --git a/regress/input-keys.sh b/regress/input-keys.sh
index e2fc41f54..cb771d19a 100644
--- a/regress/input-keys.sh
+++ b/regress/input-keys.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 sleep 1
 $TMUX -f/dev/null new -x20 -y2 -d \; set -g escape-time 0 || exit 1
diff --git a/regress/input-reflow-stress.sh b/regress/input-reflow-stress.sh
index aa1bbd717..926e8cdd0 100644
--- a/regress/input-reflow-stress.sh
+++ b/regress/input-reflow-stress.sh
@@ -8,8 +8,8 @@ export PATH TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
 
-TMUX="$TEST_TMUX -Linput-reflow-stress-$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Linput-reflow-stress-outer-$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 TMP=$(mktemp "${TMPDIR:-/tmp}/input-reflow-stress.XXXXXX") || exit 1
 EXP=$(mktemp "${TMPDIR:-/tmp}/input-reflow-stress.XXXXXX") || exit 1
diff --git a/regress/input-replies.sh b/regress/input-replies.sh
index 3435cd943..5fc77f843 100644
--- a/regress/input-replies.sh
+++ b/regress/input-replies.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 $TMUX kill-server 2>/dev/null
 sleep 0.5
diff --git a/regress/input-requests.sh b/regress/input-requests.sh
index 5e7b3781a..094ce2a8a 100644
--- a/regress/input-requests.sh
+++ b/regress/input-requests.sh
@@ -15,7 +15,8 @@ import tempfile
 import time
 
 tmux = sys.argv[1]
-server = [tmux, "-Ltest", "-f/dev/null"]
+label = "testA%d" % os.getpid()
+server = [tmux, "-L" + label, "-f/dev/null"]
 
 def run(*args, check=True):
     return subprocess.run(server + list(args), check=check,
@@ -25,7 +26,7 @@ def attach():
     pid, fd = os.forkpty()
     if pid == 0:
         os.environ["TERM"] = "xterm-256color"
-        os.execl(tmux, tmux, "-Ltest", "-f/dev/null", "attach-session",
+        os.execl(tmux, tmux, "-L" + label, "-f/dev/null", "attach-session",
             "-t", "requests")
     os.set_blocking(fd, False)
     return pid, fd
diff --git a/regress/kill-session-process-exit.sh b/regress/kill-session-process-exit.sh
index 04617ca2c..405449be2 100644
--- a/regress/kill-session-process-exit.sh
+++ b/regress/kill-session-process-exit.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 sleep 1
 
diff --git a/regress/lifecycle-deferred.sh b/regress/lifecycle-deferred.sh
index 2650f1827..d2669ff46 100644
--- a/regress/lifecycle-deferred.sh
+++ b/regress/lifecycle-deferred.sh
@@ -8,8 +8,8 @@ export TERM LC_ALL LANG
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
 
-TMUX="$TEST_TMUX -Llifecycle-deferred -f/dev/null"
-TMUX2="$TEST_TMUX -Llifecycle-deferred-outer -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 TMPDIR=$(mktemp -d)
 IN="$TMPDIR/in"
diff --git a/regress/mode-mutation.sh b/regress/mode-mutation.sh
index cc73d426d..96927e995 100644
--- a/regress/mode-mutation.sh
+++ b/regress/mode-mutation.sh
@@ -12,8 +12,8 @@ TMP=$(mktemp -d) || exit 1
 TMUX_TMPDIR="$TMP"
 export TMUX_TMPDIR
 
-TMUX="$TEST_TMUX -Lmode-mutation-$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Lmode-mutation-outer-$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup_servers()
 {
diff --git a/regress/new-session-base-index.sh b/regress/new-session-base-index.sh
index bb6dd5945..89fdb4de5 100644
--- a/regress/new-session-base-index.sh
+++ b/regress/new-session-base-index.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/new-session-command.sh b/regress/new-session-command.sh
index b2fc91db7..520c91e4f 100644
--- a/regress/new-session-command.sh
+++ b/regress/new-session-command.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/new-session-environment.sh b/regress/new-session-environment.sh
index e5404e67d..fc935687f 100644
--- a/regress/new-session-environment.sh
+++ b/regress/new-session-environment.sh
@@ -5,7 +5,7 @@
 PATH=/bin:/usr/bin
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TERM=$($TMUX start \; show -gv default-terminal)
diff --git a/regress/new-session-no-client.sh b/regress/new-session-no-client.sh
index 84fddaecb..2f3da5abe 100644
--- a/regress/new-session-no-client.sh
+++ b/regress/new-session-no-client.sh
@@ -8,7 +8,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/new-session-size.sh b/regress/new-session-size.sh
index 029bd6eed..6a35abbbd 100644
--- a/regress/new-session-size.sh
+++ b/regress/new-session-size.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/new-window-command.sh b/regress/new-window-command.sh
index 183491159..21a2661e8 100644
--- a/regress/new-window-command.sh
+++ b/regress/new-window-command.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/options-array.sh b/regress/options-array.sh
index 3b18ce977..c372e3461 100644
--- a/regress/options-array.sh
+++ b/regress/options-array.sh
@@ -20,7 +20,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 check_value()
diff --git a/regress/options-scope.sh b/regress/options-scope.sh
index bbc7168aa..ac6d62f77 100644
--- a/regress/options-scope.sh
+++ b/regress/options-scope.sh
@@ -17,7 +17,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_value $args $expected
diff --git a/regress/options-values.sh b/regress/options-values.sh
index 28acd2b47..75da52e01 100644
--- a/regress/options-values.sh
+++ b/regress/options-values.sh
@@ -17,7 +17,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 check_value()
diff --git a/regress/osc-11colours.sh b/regress/osc-11colours.sh
index 2fba76d82..5cdc1be41 100644
--- a/regress/osc-11colours.sh
+++ b/regress/osc-11colours.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 $TMUX new -d
diff --git a/regress/pane-ops.sh b/regress/pane-ops.sh
index 46984bc27..762bea200 100644
--- a/regress/pane-ops.sh
+++ b/regress/pane-ops.sh
@@ -30,7 +30,7 @@ LC_ALL=C.UTF-8
 export TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_ok $cmd...
diff --git a/regress/prompt-keys.sh b/regress/prompt-keys.sh
index 8c17581b1..6fde51b7b 100644
--- a/regress/prompt-keys.sh
+++ b/regress/prompt-keys.sh
@@ -7,8 +7,8 @@ LANG=C.UTF-8
 export TERM LC_ALL LANG
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-OUT="$TEST_TMUX -Ltest -f/dev/null"		# outer (host for the client)
-IN="$TEST_TMUX -Ltest2 -f/dev/null"		# inner (under test)
+OUT="$TEST_TMUX -LtestA$$ -f/dev/null"		# outer (host for the client)
+IN="$TEST_TMUX -LtestB$$ -f/dev/null"		# inner (under test)
 
 $OUT kill-server 2>/dev/null
 $IN kill-server 2>/dev/null
diff --git a/regress/prompt-mechanics.sh b/regress/prompt-mechanics.sh
index 6f3e5294e..55bd17a69 100644
--- a/regress/prompt-mechanics.sh
+++ b/regress/prompt-mechanics.sh
@@ -20,8 +20,8 @@ LANG=C.UTF-8
 export TERM LC_ALL LANG
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-OUT="$TEST_TMUX -Ltest -f/dev/null"		# outer (host for the client)
-IN="$TEST_TMUX -Ltest2 -f/dev/null"		# inner (under test)
+OUT="$TEST_TMUX -LtestA$$ -f/dev/null"		# outer (host for the client)
+IN="$TEST_TMUX -LtestB$$ -f/dev/null"		# inner (under test)
 
 $OUT kill-server 2>/dev/null
 $IN kill-server 2>/dev/null
diff --git a/regress/run-shell-output.sh b/regress/run-shell-output.sh
index 3b44504c2..926a520c9 100644
--- a/regress/run-shell-output.sh
+++ b/regress/run-shell-output.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-bidi.sh b/regress/screen-redraw-bidi.sh
index e4e962950..ee9c2fa16 100644
--- a/regress/screen-redraw-bidi.sh
+++ b/regress/screen-redraw-bidi.sh
@@ -17,8 +17,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-cache.sh b/regress/screen-redraw-cache.sh
index 27c98e3b4..0e0abf9db 100644
--- a/regress/screen-redraw-cache.sh
+++ b/regress/screen-redraw-cache.sh
@@ -18,8 +18,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-floating.sh b/regress/screen-redraw-floating.sh
index 82c36d364..67d213699 100644
--- a/regress/screen-redraw-floating.sh
+++ b/regress/screen-redraw-floating.sh
@@ -16,8 +16,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-indicators.sh b/regress/screen-redraw-indicators.sh
index 60bf652b2..28a1dee6c 100644
--- a/regress/screen-redraw-indicators.sh
+++ b/regress/screen-redraw-indicators.sh
@@ -18,8 +18,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-outside.sh b/regress/screen-redraw-outside.sh
index 53a2a72b1..3eeb94938 100644
--- a/regress/screen-redraw-outside.sh
+++ b/regress/screen-redraw-outside.sh
@@ -18,8 +18,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-popups.sh b/regress/screen-redraw-popups.sh
index 1eb7e5897..8ad3ba2eb 100644
--- a/regress/screen-redraw-popups.sh
+++ b/regress/screen-redraw-popups.sh
@@ -17,8 +17,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-scrollbars.sh b/regress/screen-redraw-scrollbars.sh
index f8298b5e1..914fe542c 100644
--- a/regress/screen-redraw-scrollbars.sh
+++ b/regress/screen-redraw-scrollbars.sh
@@ -16,8 +16,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-status.sh b/regress/screen-redraw-status.sh
index 12ca20bb1..46cb5fcad 100644
--- a/regress/screen-redraw-status.sh
+++ b/regress/screen-redraw-status.sh
@@ -20,8 +20,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-tiled.sh b/regress/screen-redraw-tiled.sh
index 94353f5f8..3b32478f0 100644
--- a/regress/screen-redraw-tiled.sh
+++ b/regress/screen-redraw-tiled.sh
@@ -24,8 +24,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-window-style.sh b/regress/screen-redraw-window-style.sh
index 1d2b2b281..69ac824f2 100644
--- a/regress/screen-redraw-window-style.sh
+++ b/regress/screen-redraw-window-style.sh
@@ -13,8 +13,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/session-group-resize.sh b/regress/session-group-resize.sh
index 28e7a85ed..f2b634a43 100644
--- a/regress/session-group-resize.sh
+++ b/regress/session-group-resize.sh
@@ -10,7 +10,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP1=$(mktemp)
diff --git a/regress/session-ops.sh b/regress/session-ops.sh
index 4938ee22c..08c5dfbae 100644
--- a/regress/session-ops.sh
+++ b/regress/session-ops.sh
@@ -27,7 +27,7 @@ LC_ALL=C.UTF-8
 export TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_ok $cmd...
diff --git a/regress/set-hook-B.sh b/regress/set-hook-B.sh
index 188bfdd24..4947af70c 100755
--- a/regress/set-hook-B.sh
+++ b/regress/set-hook-B.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/set-hook-R.sh b/regress/set-hook-R.sh
index b36edc323..49af68efc 100644
--- a/regress/set-hook-R.sh
+++ b/regress/set-hook-R.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/style-trim.sh b/regress/style-trim.sh
index 5b03482d9..f42e0ffff 100644
--- a/regress/style-trim.sh
+++ b/regress/style-trim.sh
@@ -17,9 +17,9 @@ if command -v bash >/dev/null 2>&1; then
 fi
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 $TMUX2 kill-server 2>/dev/null
 
 $TMUX2 -f/dev/null new -d "$TMUX -f/dev/null new -- $shell"
diff --git a/regress/targets-panes.sh b/regress/targets-panes.sh
index db353403b..9ea936173 100644
--- a/regress/targets-panes.sh
+++ b/regress/targets-panes.sh
@@ -27,7 +27,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check $target $expected [format]
diff --git a/regress/targets.sh b/regress/targets.sh
index 346a86736..75ee3dbb8 100644
--- a/regress/targets.sh
+++ b/regress/targets.sh
@@ -29,7 +29,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check $target $expected [format]
diff --git a/regress/tty-draw-line.sh b/regress/tty-draw-line.sh
index b57de08cc..59331aa0d 100644
--- a/regress/tty-draw-line.sh
+++ b/regress/tty-draw-line.sh
@@ -10,8 +10,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 fail() {
 	echo "$*" >&2
diff --git a/regress/tty-keys.sh b/regress/tty-keys.sh
index 849f6f336..1b300b995 100644
--- a/regress/tty-keys.sh
+++ b/regress/tty-keys.sh
@@ -4,9 +4,9 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 $TMUX2 kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/utf8-test.sh b/regress/utf8-test.sh
index b3cf41bd0..1836cc459 100644
--- a/regress/utf8-test.sh
+++ b/regress/utf8-test.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 TMP=$(mktemp)
 trap "rm -f $TMP" 0 1 15
 $TMUX kill-server 2>/dev/null
diff --git a/regress/window-ops.sh b/regress/window-ops.sh
index dde7fc957..bdb1b5fb9 100644
--- a/regress/window-ops.sh
+++ b/regress/window-ops.sh
@@ -30,7 +30,7 @@ LC_ALL=C.UTF-8
 export TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_ok $cmd...