diff --git a/input-keys.c b/input-keys.c
index 765e948d0..fbb7e1528 100644
--- a/input-keys.c
+++ b/input-keys.c
@@ -419,9 +419,8 @@ input_key_client_supports_extended(struct client *c, key_code key)
 		return (1);
 	if (options_get_number(global_options, "extended-keys") == 0)
 		return (0);
-	if (options_get_number(global_options, "extended-keys-format") ==
-	    EXTENDED_KEYS_KITTY)
-		return ((c->tty.flags & TTY_KKBPUSHED) != 0);
+	if (c->tty.flags & TTY_KKBPUSHED)
+		return (1);
 	return (tty_term_has(c->tty.term, TTYC_ENEKS));
 }
 
diff --git a/input.c b/input.c
index 97427c2be..4e3652c9d 100644
--- a/input.c
+++ b/input.c
@@ -162,6 +162,7 @@ static void	input_set_state(struct input_ctx *,
 		    const struct input_transition *);
 static void	input_reset_cell(struct input_ctx *);
 static void	input_report_current_theme(struct input_ctx *);
+static int	input_pane_supports_extended(struct window_pane *);
 static void	input_osc_4(struct input_ctx *, const char *);
 static void	input_osc_8(struct input_ctx *, const char *);
 static void	input_osc_9(struct input_ctx *, const char *);
@@ -1179,6 +1180,29 @@ input_send_reply(struct input_ctx *ictx, const char *reply)
 	}
 }
 
+/* Return whether attached tty clients can provide extended keys to a pane. */
+static int
+input_pane_supports_extended(struct window_pane *wp)
+{
+	struct client	*c;
+
+	if (wp == NULL)
+		return (1);
+	TAILQ_FOREACH(c, &clients, entry) {
+		if ((c->flags & (CLIENT_TERMINAL|CLIENT_ATTACHED)) !=
+		    (CLIENT_TERMINAL|CLIENT_ATTACHED))
+			continue;
+		if (c->flags &
+		    (CLIENT_UNATTACHEDFLAGS|CLIENT_CONTROL|CLIENT_READONLY))
+			continue;
+		if (c->session == NULL || !session_has(c->session, wp->window))
+			continue;
+		if (!input_key_client_supports_extended(c, 0))
+			return (0);
+	}
+	return (1);
+}
+
 /* Reply to terminal query. */
 static void printflike(3, 4)
 input_reply(struct input_ctx *ictx, int add, const char *fmt, ...)
@@ -1576,7 +1600,10 @@ input_csi_dispatch(struct input_ctx *ictx)
 		    options_get_number(global_options, "extended-keys-format") !=
 		    EXTENDED_KEYS_KITTY)
 			break;
-		input_reply(ictx, 1, "\033[?%uu", s->kitty_keys.flags);
+		n = s->kitty_keys.flags;
+		if (!input_pane_supports_extended(ictx->wp))
+			n = 0;
+		input_reply(ictx, 1, "\033[?%uu", n);
 		break;
 	case INPUT_CSI_KITTY_SET:
 		if (options_get_number(global_options, "extended-keys") == 0 ||
diff --git a/regress/kitty-keys-clients.sh b/regress/kitty-keys-clients.sh
new file mode 100755
index 000000000..c36cfc07c
--- /dev/null
+++ b/regress/kitty-keys-clients.sh
@@ -0,0 +1,103 @@
+#!/bin/sh
+
+# Test per-client keyboard protocol negotiation and pane-side fallback.
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+KCONF=$(mktemp)
+UCONF=$(mktemp)
+LCONF=$(mktemp)
+OUT=$(mktemp)
+TMP=$(mktemp)
+SOCKETS="testKmc$$ testKka$$ testKua$$ testKrt$$ testKru$$ testKlq$$ testKlu$$"
+
+printf '%s\n' 'set -g extended-keys on' \
+    'set -g extended-keys-format kitty' >"$KCONF"
+printf '%s\n' 'set -g extended-keys on' \
+    'set -g extended-keys-format csi-u' >"$UCONF"
+printf '%s\n' 'set -g extended-keys off' >"$LCONF"
+
+cleanup()
+{
+	rm -f "$KCONF" "$UCONF" "$LCONF" "$OUT" "$TMP"
+	for socket in $SOCKETS; do
+		$TEST_TMUX -L"$socket" kill-server 2>/dev/null
+	done
+}
+trap cleanup 0 1 15
+
+wait_for_mode()
+{
+	tmux=$1
+	wanted=$2
+	i=0
+	while [ "$($tmux display-message -pt: '#{pane_key_mode}')" != "$wanted" ] &&
+	    [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ "$($tmux display-message -pt: '#{pane_key_mode}')" = "$wanted" ]
+}
+
+wait_for_output()
+{
+	i=0
+	while [ ! -s "$1" ] && [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ -s "$1" ]
+}
+
+# A server preferring Kitty must negotiate each client independently.
+M="$TEST_TMUX -LtestKmc$$ -f$KCONF"
+KA="$TEST_TMUX -LtestKka$$ -f$KCONF"
+UA="$TEST_TMUX -LtestKua$$ -f$UCONF"
+$M new-session -d -x80 -y24 -s kitty || exit 1
+$M new-session -d -x80 -y24 -s csiu || exit 1
+$KA new-session -d -x80 -y24 "$M attach-session -t kitty" || exit 1
+$UA new-session -d -x80 -y24 "$M attach-session -t csiu" || exit 1
+wait_for_mode "$KA" 'Kitty 1' || exit 1
+wait_for_mode "$UA" 'Ext 2' || exit 1
+
+uc=$($M list-clients -F '#{client_name} #{client_session}' |
+    awk '$2 == "csiu" { print $1 }')
+[ -n "$uc" ] || exit 1
+$M command-prompt -t"$uc" -k 'display-message -pl "%%"' >"$TMP" &
+pid=$!
+sleep 0.2
+$UA send-keys 'Escape [97;5u'
+wait "$pid"
+[ "$(tr -d '[:space:]' <"$TMP")" = 'C-a' ] || exit 1
+$KA kill-server 2>/dev/null
+$UA kill-server 2>/dev/null
+$M kill-server 2>/dev/null
+
+# Standard extended input must be translated for a Kitty-requesting pane.
+: >"$OUT"
+R="$TEST_TMUX -LtestKrt$$ -f$KCONF"
+RU="$TEST_TMUX -LtestKru$$ -f$UCONF"
+$R new-session -d -x80 -y24 \
+    "stty raw -echo; printf '\033[>1u'; dd bs=1 count=7 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5" || exit 1
+$RU new-session -d -x80 -y24 "$R attach-session" || exit 1
+wait_for_mode "$RU" 'Ext 2' || exit 1
+$RU send-keys C-a
+wait_for_output "$OUT" || exit 1
+[ "$(tr -d ' \n' <"$OUT")" = '1b5b39373b3575' ] || exit 1
+$RU kill-server 2>/dev/null
+$R kill-server 2>/dev/null
+
+# Do not report Kitty active when an attached client only supports VT10x.
+: >"$OUT"
+printf '%s\n' "set -as terminal-overrides ',*:Eneks@:Dseks@'" >>"$KCONF"
+LQ="$TEST_TMUX -LtestKlq$$ -f$KCONF"
+LU="$TEST_TMUX -LtestKlu$$ -f$LCONF"
+$LQ new-session -d -x80 -y24 \
+    "stty raw -echo; sleep 2; printf '\033[>1u\033[?u'; dd bs=1 count=5 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5" || exit 1
+$LU new-session -d -x80 -y24 "$LQ attach-session" || exit 1
+wait_for_output "$OUT" || exit 1
+[ "$(tr -d ' \n' <"$OUT")" = '1b5b3f3075' ] || exit 1
+
+exit 0
diff --git a/tmux.1 b/tmux.1
index b04c652d4..614d2cebd 100644
--- a/tmux.1
+++ b/tmux.1
@@ -4935,6 +4935,13 @@ this feature is disabled and only standard keys are reported.
 .Pp
 .Nm
 will always request extended keys itself if the terminal supports them.
+When the
+.Ic kitty
+format is selected, it is preferred separately for each client; clients which
+do not support it use standard extended keys if available, or standard VT10x
+keys otherwise.
+Input from standard extended-key clients is translated to Kitty encoding for
+applications which have requested it.
 See also the
 .Ic extkeys
 feature for the
diff --git a/tty-keys.c b/tty-keys.c
index 57a9cf941..6ecbd003c 100644
--- a/tty-keys.c
+++ b/tty-keys.c
@@ -1112,8 +1112,7 @@ tty_keys_extended_key(struct tty *tty, const char *buf, size_t len,
 	utf8_char	 uc;
 
 	*size = 0;
-	if (options_get_number(global_options, "extended-keys-format") ==
-	    EXTENDED_KEYS_KITTY)
+	if (tty->flags & TTY_KKBPUSHED)
 		return (-1);
 
 	/* First two bytes are always \033[. */
diff --git a/tty.c b/tty.c
index 635582524..85303b8c9 100644
--- a/tty.c
+++ b/tty.c
@@ -562,16 +562,21 @@ void
 tty_update_features(struct tty *tty)
 {
 	struct client	*c = tty->client;
+	int		 extended_keys, format;
 
 	if (tty_apply_features(tty->term))
 		tty_term_apply_overrides(tty->term);
 
 	if (tty_use_margin(tty))
 		tty_putcode(tty, TTYC_ENMG);
-	if (options_get_number(global_options, "extended-keys-format") ==
-	    EXTENDED_KEYS_KITTY)
+	extended_keys = options_get_number(global_options, "extended-keys");
+	format = options_get_number(global_options, "extended-keys-format");
+	if (extended_keys == 0 ||
+	    (format == EXTENDED_KEYS_KITTY &&
+	    (tty->flags & (TTY_HAVEKKB|TTY_KKBSUPPORT)) ==
+	    (TTY_HAVEKKB|TTY_KKBSUPPORT)))
 		tty_puts(tty, tty_term_string(tty->term, TTYC_DSEKS));
-	else if (options_get_number(global_options, "extended-keys"))
+	else
 		tty_puts(tty, tty_term_string(tty->term, TTYC_ENEKS));
 	tty_update_kitty(tty, NULL);
 	if (options_get_number(global_options, "focus-events"))