diff --git a/root/init.go b/root/init.go
index 2dfb847..edbb30a 100644
--- a/root/init.go
+++ b/root/init.go
@@ -25,10 +25,10 @@ For example, add this to your ~/.zshrc:
 		case "zsh":
 			fmt.Printf(`
 # Iris Autostart Hook
-if [ -n "$TMUX" ] && [ -n "$IRIS_PID" ]; then
-    if ps -o comm= -p $PPID 2>/dev/null | grep -q "tmux"; then
-        unset IRIS_PID IRIS_IS_CHILD IRIS_FD
-    fi
+# a multiplexer pane inherits IRIS_* but runs on its own tty, so those vars
+# point at an iris that is not driving this terminal
+if [ -n "$IRIS_PID" ] && [ "$IRIS_PID" != "$PPID" ] && [ "${TTY:-$(tty 2>/dev/null)}" != "$IRIS_TTY" ]; then
+    unset IRIS_PID IRIS_IS_CHILD IRIS_FD IRIS_TTY
 fi
 
 if [ -z "$IRIS_PID" ] && [ -z "$IRIS_RESCUE" ]; then
@@ -68,10 +68,10 @@ fi
 		case "bash":
 			fmt.Printf(`
 # Iris Autostart Hook
-if [ -n "$TMUX" ] && [ -n "$IRIS_PID" ]; then
-    if ps -o comm= -p $PPID 2>/dev/null | grep -q "tmux"; then
-        unset IRIS_PID IRIS_IS_CHILD IRIS_FD
-    fi
+# a multiplexer pane inherits IRIS_* but runs on its own tty, so those vars
+# point at an iris that is not driving this terminal
+if [ -n "$IRIS_PID" ] && [ "$IRIS_PID" != "$PPID" ] && [ "$(tty 2>/dev/null)" != "$IRIS_TTY" ]; then
+    unset IRIS_PID IRIS_IS_CHILD IRIS_FD IRIS_TTY
 fi
 
 if [ -z "$IRIS_PID" ] && [ -z "$IRIS_RESCUE" ]; then
@@ -96,11 +96,16 @@ fi
 		case "fish":
 			fmt.Printf(`
 # Iris Autostart Hook
-if set -q TMUX; and set -q IRIS_PID
-    if ps -o comm= -p $PPID 2>/dev/null | grep -q "tmux"
+# a multiplexer pane inherits IRIS_* but runs on its own tty, so those vars
+# point at an iris that is not driving this terminal
+if set -q IRIS_PID
+    set -l iris_ppid (ps -o ppid= -p $fish_pid 2>/dev/null | string trim)
+    set -l iris_cur_tty (tty 2>/dev/null)
+    if test "$IRIS_PID" != "$iris_ppid"; and test "$iris_cur_tty" != "$IRIS_TTY"
         set -e IRIS_PID
         set -e IRIS_IS_CHILD
         set -e IRIS_FD
+        set -e IRIS_TTY
     end
 end
 
diff --git a/root/wrapper.go b/root/wrapper.go
index 94bae49..e8ad519 100644
--- a/root/wrapper.go
+++ b/root/wrapper.go
@@ -153,15 +153,27 @@ func runWrapper() {
 	c.ExtraFiles = make([]*os.File, 11)
 	// pass write end of pipe to shell as fd 13 (since index 10 maps to 13)
 	c.ExtraFiles[10] = w
-	c.Env = adapter.GetEnv(13, os.Getpid())
 
-	ptmx, err := pty.Start(c)
+	ptmx, tts, err := pty.Open()
 	if err != nil {
-		_, _ = fmt.Fprintf(os.Stderr, "[IRIS] failed to start PTY: %v\n", err)
+		_, _ = fmt.Fprintf(os.Stderr, "[IRIS] failed to open PTY: %v\n", err)
 		return
 	}
 	defer func() { _ = ptmx.Close() }()
 
+	c.Stdin, c.Stdout, c.Stderr = tts, tts, tts
+	c.SysProcAttr = &syscall.SysProcAttr{Setsid: true, Setctty: true}
+	// the shell compares its own tty against this to tell whether the inherited
+	// IRIS_* vars belong to it or leaked in from an outer terminal
+	c.Env = append(adapter.GetEnv(13, os.Getpid()), "IRIS_TTY="+tts.Name())
+
+	if err = c.Start(); err != nil {
+		_ = tts.Close()
+		_, _ = fmt.Fprintf(os.Stderr, "[IRIS] failed to start shell: %v\n", err)
+		return
+	}
+	_ = tts.Close()
+
 	stdinFile := os.Stdin
 	if !term.IsTerminal(int(stdinFile.Fd())) {
 		if tty, ttyErr := os.OpenFile("/dev/tty", os.O_RDWR, 0); ttyErr == nil {