diff --git a/tmux.h b/tmux.h
index 26422b2e3..1241069ef 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tmux.h,v 1.1426 2026/08/18 07:43:44 nicm Exp $ */
+/* $OpenBSD: tmux.h,v 1.1427 2026/08/18 09:01:20 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -1811,8 +1811,9 @@ struct tty {
 #define TTY_WAITFG 0x2000
 #define TTY_WAITBG 0x4000
 #define TTY_BRACKETPASTE 0x8000
+#define TTY_HAVESYNC 0x10000
 #define TTY_ALL_REQUEST_FLAGS \
-	(TTY_HAVEDA|TTY_HAVEDA2|TTY_HAVEXDA)
+	(TTY_HAVEDA|TTY_HAVEDA2|TTY_HAVEXDA|TTY_HAVESYNC)
 	int		 flags;
 
 	struct tty_term	*term;
diff --git a/tty-keys.c b/tty-keys.c
index 6c2289495..8462e0d9b 100644
--- a/tty-keys.c
+++ b/tty-keys.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tty-keys.c,v 1.213 2026/08/17 14:47:41 nicm Exp $ */
+/* $OpenBSD: tty-keys.c,v 1.214 2026/08/18 09:01:20 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -59,6 +59,7 @@ static int	tty_keys_device_attributes2(struct tty *, const char *, size_t,
 		    size_t *);
 static int	tty_keys_extended_device_attributes(struct tty *, const char *,
 		    size_t, size_t *);
+static int	tty_keys_sync(struct tty *, const char *, size_t, size_t *);
 static int	tty_keys_palette(struct tty *, const char *, size_t, size_t *);
 
 /* A key tree entry. */
@@ -771,6 +772,17 @@ tty_keys_next(struct tty *tty)
 		goto partial_key;
 	}
 
+	/* Is this a synchronized update mode response? */
+	switch (tty_keys_sync(tty, buf, len, &size)) {
+	case 0:		/* yes */
+		key = KEYC_UNKNOWN;
+		goto complete_key;
+	case -1:	/* no, or not valid */
+		break;
+	case 1:		/* partial */
+		goto partial_key;
+	}
+
 	/* Is this a primary device attributes response? */
 	switch (tty_keys_device_attributes(tty, buf, len, &size)) {
 	case 0:		/* yes */
@@ -1521,6 +1533,54 @@ tty_keys_device_attributes(struct tty *tty, const char *buf, size_t len,
 	return (0);
 }
 
+/*
+ * Handle a synchronized update mode response. Returns 0 for success, -1 for
+ * failure, 1 for partial.
+ */
+static int
+tty_keys_sync(struct tty *tty, const char *buf, size_t len, size_t *size)
+{
+	struct client		*c = tty->client;
+	static const char	 prefix[] = "\033[?2026;";
+	size_t			 i;
+	int			 status;
+
+	*size = 0;
+	if (tty->flags & TTY_HAVESYNC)
+		return (-1);
+
+	/* The response is always \033[?2026;Ps$y. */
+	for (i = 0; i < (sizeof prefix) - 1; i++) {
+		if (i == len)
+			return (1);
+		if (buf[i] != prefix[i])
+			return (-1);
+	}
+	if (i == len)
+		return (1);
+	if (buf[i] < '0' || buf[i] > '4')
+		return (-1);
+	status = buf[i++] - '0';
+	if (i == len)
+		return (1);
+	if (buf[i++] != '$')
+		return (-1);
+	if (i == len)
+		return (1);
+	if (buf[i++] != 'y')
+		return (-1);
+	*size = i;
+
+	if (status == 1 || status == 2 || status == 3) {
+		tty_parse_client_features(c, "sync", ",");
+		tty_update_features(tty);
+	}
+	log_debug("%s: received DECRPM %.*s", c->name, (int)*size, buf);
+	tty->flags |= TTY_HAVESYNC;
+
+	return (0);
+}
+
 /*
  * Handle secondary device attributes input. Returns 0 for success, -1 for
  * failure, 1 for partial.
diff --git a/tty.c b/tty.c
index e20796a23..e8a60c68d 100644
--- a/tty.c
+++ b/tty.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tty.c,v 1.478 2026/08/17 14:47:41 nicm Exp $ */
+/* $OpenBSD: tty.c,v 1.479 2026/08/18 09:01:20 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -403,6 +403,8 @@ tty_send_requests(struct tty *tty)
 			tty_puts(tty, "\033[>c");
 		if (~tty->flags & TTY_HAVEXDA)
 			tty_puts(tty, "\033[>q");
+		if (~tty->flags & TTY_HAVESYNC)
+			tty_puts(tty, "\033[?2026$p");
 		tty_puts(tty, "\033]10;?\033\\\033]11;?\033\\");
 		tty->flags |= (TTY_WAITBG|TTY_WAITFG);
 	} else