Add a test for Kitty keyboard protocol input parsing

Also note that kitty-keys-terminal.sh cannot run under the regress
Makefile, which uses env -i and so removes DISPLAY and HOME, and make the
Kitty test file modes match the rest of regress.

CHANGES

@@ -111,6 +111,18 @@ CHANGES FROM 3.7c TO 3.8
 
 * Change show-options and show-hooks to use formats and add a -F flag to each.
 
+* Add support for the Kitty keyboard protocol, selected with a new kitty
+  value for the extended-keys-format option. This can report the Super and
+  Hyper modifiers (key name prefixes s- and H-) as well as Control, Meta
+  and Shift. The protocol is negotiated separately with each client, so
+  terminals with different capabilities may be attached at the same time;
+  clients without it use standard extended keys, or VT10x keys if those
+  are also unavailable, and their input is translated for applications
+  which have asked for Kitty encoding.
+
+* Add a client_key_mode format giving the extended key reporting mode in
+  use for a client, alongside the existing pane_key_mode for a pane.
+
 * Allow individual terminal features to be disabled by adding @ to their names
   in terminal-features, and add a utf8 feature for terminals which support
   UTF-8 output.

Makefile.am

@@ -171,6 +171,7 @@ dist_tmux_SOURCES = \
 	grid.c \
 	hooks.c \
 	hyperlinks.c \
+	input-kitty.c \
 	input-keys.c \
 	input.c \
 	job.c \
@@ -212,6 +213,7 @@ dist_tmux_SOURCES = \
 	tty-acs.c \
 	tty-draw.c \
 	tty-features.c \
+	tty-kitty.c \
 	tty-keys.c \
 	tty-term.c \
 	tty.c \

cmd-display-message.c

@@ -115,15 +115,11 @@ cmd_display_message_exec(struct cmd *self, struct cmdq_item *item)
 
 	/*
 	 * -c is intended to be the client where the message should be
-	 * displayed if -p is not given, but it makes sense to use it for the
+	 * displayed if -p is not given. But it makes sense to use it for the
-	 * client formats too. If it was given explicitly, use it even when it
+	 * formats too, assuming it matches the session. If it doesn't, use the
-	 * is not in the target session, since the formats should describe the
+	 * best client for the session.
-	 * client which was asked for; the session, window and pane formats
-	 * still come from the target. Otherwise it is just the current client,
-	 * so only use it if it matches the session and fall back to the best
-	 * client for the session if not.
 	 */
-	if (tc != NULL && (args_has(args, 'c') || tc->session == s))
+	if (tc != NULL && tc->session == s)
 		c = tc;
 	else if (s != NULL)
 		c = cmd_find_best_client(s);

format.c

@@ -1617,6 +1617,43 @@ format_cb_client_height(struct format_tree *ft)
 	return (NULL);
 }
 
+/* Callback for client_key_mode. */
+static void *
+format_cb_client_key_mode(struct format_tree *ft)
+{
+	struct client	*c = ft->c;
+	const char	*mode;
+	char		*s;
+	int		 kitty, eks;
+
+	if (c == NULL || (~c->tty.flags & TTY_STARTED))
+		return (NULL);
+
+	if (c->tty.flags & TTY_KKBPUSHED) {
+		xasprintf(&s, "Kitty %u", c->tty.kitty_keys);
+		return (s);
+	}
+
+	/* This mirrors the choice made in tty_update_features(). */
+	kitty = ((c->tty.flags & (TTY_HAVEKKB|TTY_KKBSUPPORT)) ==
+	    (TTY_HAVEKKB|TTY_KKBSUPPORT));
+	eks = (options_get_number(global_options, "extended-keys") != 0);
+	if (kitty && options_get_number(global_options,
+	    "extended-keys-format") == EXTENDED_KEYS_KITTY)
+		eks = 0;
+	if (eks && tty_term_has(c->tty.term, TTYC_ENEKS))
+		mode = "Ext";
+	else
+		mode = "VT10x";
+
+	/* The terminal supports Kitty keys but they are not in use. */
+	if (kitty) {
+		xasprintf(&s, "%s (Kitty)", mode);
+		return (s);
+	}
+	return (xstrdup(mode));
+}
+
 /* Callback for client_key_table. */
 static void *
 format_cb_client_key_table(struct format_tree *ft)
@@ -2487,7 +2524,17 @@ format_cb_pane_unseen_changes(struct format_tree *ft)
 static void *
 format_cb_pane_key_mode(struct format_tree *ft)
 {
+	char	*s;
+
 	if (ft->wp != NULL && ft->wp->screen != NULL) {
+		if (options_get_number(global_options, "extended-keys-format") ==
+		    EXTENDED_KEYS_KITTY) {
+			if (ft->wp->screen->kitty_keys.flags == 0)
+				return (xstrdup("VT10x"));
+			xasprintf(&s, "Kitty %u",
+			    ft->wp->screen->kitty_keys.flags);
+			return (s);
+		}
 		switch (ft->wp->screen->mode & EXTENDED_KEY_MODES) {
 		case MODE_KEYS_EXTENDED:
 			return (xstrdup("Ext 1"));
@@ -3642,6 +3689,9 @@ static const struct format_table_entry format_table[] = {
 	{ "client_height", FORMAT_TABLE_STRING,
 	  format_cb_client_height
 	},
+	{ "client_key_mode", FORMAT_TABLE_STRING,
+	  format_cb_client_key_mode
+	},
 	{ "client_key_table", FORMAT_TABLE_STRING,
 	  format_cb_client_key_table
 	},

input-keys.c

@@ -395,7 +395,8 @@ input_key_build(void)
 
 /* Translate a key code into an output key sequence for a pane. */
 int
-input_key_pane(struct window_pane *wp, key_code key, struct mouse_event *m)
+input_key_pane(struct window_pane *wp, key_code key, struct mouse_event *m,
+    int extended_encoding)
 {
 	if (log_get_level() != 0) {
 		log_debug("writing key 0x%llx (%s) to %%%u", key,
@@ -407,7 +408,20 @@ input_key_pane(struct window_pane *wp, key_code key, struct mouse_event *m)
 			input_key_mouse(wp, m);
 		return (0);
 	}
-	return (input_key(wp->screen, wp->event, key));
+	return (input_key(wp->screen, wp->event, key, extended_encoding));
+}
+
+/* Return whether a key may use the configured extended encoding. */
+int
+input_key_client_supports_extended(struct client *c, key_code key)
+{
+	if (c == NULL || (key & KEYC_SENT))
+		return (1);
+	if (options_get_number(global_options, "extended-keys") == 0)
+		return (0);
+	if (c->tty.flags & TTY_KKBPUSHED)
+		return (1);
+	return (tty_term_has(c->tty.term, TTYC_ENEKS));
 }
 
 static void
@@ -464,7 +478,8 @@ input_key_extended(struct bufferevent *bev, key_code key)
 	} else
 		key &= KEYC_MASK_KEY;
 
-	if (options_get_number(global_options, "extended-keys-format") == 1)
+	if (options_get_number(global_options, "extended-keys-format") ==
+	    EXTENDED_KEYS_XTERM)
 		xsnprintf(tmp, sizeof tmp, "\033[27;%c;%llu~", modifier, key);
 	else
 		xsnprintf(tmp, sizeof tmp, "\033[%llu;%cu", key, modifier);
@@ -571,7 +586,8 @@ input_key_mode1(struct bufferevent *bev, key_code key)
 
 /* Translate a key code into an output key sequence. */
 int
-input_key(struct screen *s, struct bufferevent *bev, key_code key)
+input_key(struct screen *s, struct bufferevent *bev, key_code key,
+    int extended_encoding)
 {
 	struct input_key_entry	*ike = NULL;
 	key_code		 newkey;
@@ -588,6 +604,11 @@ input_key(struct screen *s, struct bufferevent *bev, key_code key)
 		return (0);
 	}
 
+	if (extended_encoding &&
+	    options_get_number(global_options, "extended-keys-format") ==
+	    EXTENDED_KEYS_KITTY && input_key_kitty(s, bev, key) == 0)
+		return (0);
+
 	/* Is this backspace? */
 	if ((key & KEYC_MASK_KEY) == KEYC_BSPACE) {
 		newkey = options_get_number(global_options, "backspace");
@@ -677,6 +698,11 @@ input_key(struct screen *s, struct bufferevent *bev, key_code key)
 		log_debug("%s: ignoring key 0x%llx", __func__, key);
 		return (0);
 	}
+	if (key & (KEYC_SUPER|KEYC_HYPER))
+		return (input_key_vt10x(bev, key));
+	if (options_get_number(global_options, "extended-keys-format") ==
+	    EXTENDED_KEYS_KITTY)
+		return (input_key_vt10x(bev, key));
 
 	/*
 	 * No builtin key sequence; construct an extended key sequence

input-kitty.c

@@ -0,0 +1,327 @@
+/* $OpenBSD$ */
+
+/*
+ * Copyright (c) 2026 Michael Grant <mgrant@grant.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+
+#include <string.h>
+#include <wchar.h>
+
+#include "tmux.h"
+
+/* Track pane keyboard state and encode keys for applications. */
+
+struct input_kitty_key {
+	key_code	 key;
+	u_int		 number;
+	char		 final;
+};
+
+static const struct input_kitty_key input_kitty_keys[] = {
+	{ C0_ESC, 27, 'u' },
+	{ C0_CR, 13, 'u' },
+	{ C0_HT, 9, 'u' },
+	{ KEYC_BSPACE, 127, 'u' },
+	{ KEYC_IC, 2, '~' },
+	{ KEYC_DC, 3, '~' },
+	{ KEYC_LEFT, 1, 'D' },
+	{ KEYC_RIGHT, 1, 'C' },
+	{ KEYC_UP, 1, 'A' },
+	{ KEYC_DOWN, 1, 'B' },
+	{ KEYC_PPAGE, 5, '~' },
+	{ KEYC_NPAGE, 6, '~' },
+	{ KEYC_HOME, 1, 'H' },
+	{ KEYC_END, 1, 'F' },
+	{ KEYC_F1, 1, 'P' },
+	{ KEYC_F2, 1, 'Q' },
+	{ KEYC_F3, 13, '~' },
+	{ KEYC_F4, 1, 'S' },
+	{ KEYC_F5, 15, '~' },
+	{ KEYC_F6, 17, '~' },
+	{ KEYC_F7, 18, '~' },
+	{ KEYC_F8, 19, '~' },
+	{ KEYC_F9, 20, '~' },
+	{ KEYC_F10, 21, '~' },
+	{ KEYC_F11, 23, '~' },
+	{ KEYC_F12, 24, '~' },
+	{ KEYC_CAPSLOCK, 57358, 'u' },
+	{ KEYC_SCROLLLOCK, 57359, 'u' },
+	{ KEYC_NUMLOCK, 57360, 'u' },
+	{ KEYC_PRINTSCREEN, 57361, 'u' },
+	{ KEYC_PAUSE, 57362, 'u' },
+	{ KEYC_MENU, 57363, 'u' },
+	{ KEYC_F13, 57376, 'u' },
+	{ KEYC_F14, 57377, 'u' },
+	{ KEYC_F15, 57378, 'u' },
+	{ KEYC_F16, 57379, 'u' },
+	{ KEYC_F17, 57380, 'u' },
+	{ KEYC_F18, 57381, 'u' },
+	{ KEYC_F19, 57382, 'u' },
+	{ KEYC_F20, 57383, 'u' },
+	{ KEYC_F21, 57384, 'u' },
+	{ KEYC_F22, 57385, 'u' },
+	{ KEYC_F23, 57386, 'u' },
+	{ KEYC_F24, 57387, 'u' },
+	{ KEYC_F25, 57388, 'u' },
+	{ KEYC_F26, 57389, 'u' },
+	{ KEYC_F27, 57390, 'u' },
+	{ KEYC_F28, 57391, 'u' },
+	{ KEYC_F29, 57392, 'u' },
+	{ KEYC_F30, 57393, 'u' },
+	{ KEYC_F31, 57394, 'u' },
+	{ KEYC_F32, 57395, 'u' },
+	{ KEYC_F33, 57396, 'u' },
+	{ KEYC_F34, 57397, 'u' },
+	{ KEYC_F35, 57398, 'u' },
+	{ KEYC_KP_ZERO|KEYC_KEYPAD, 57399, 'u' },
+	{ KEYC_KP_ONE|KEYC_KEYPAD, 57400, 'u' },
+	{ KEYC_KP_TWO|KEYC_KEYPAD, 57401, 'u' },
+	{ KEYC_KP_THREE|KEYC_KEYPAD, 57402, 'u' },
+	{ KEYC_KP_FOUR|KEYC_KEYPAD, 57403, 'u' },
+	{ KEYC_KP_FIVE|KEYC_KEYPAD, 57404, 'u' },
+	{ KEYC_KP_SIX|KEYC_KEYPAD, 57405, 'u' },
+	{ KEYC_KP_SEVEN|KEYC_KEYPAD, 57406, 'u' },
+	{ KEYC_KP_EIGHT|KEYC_KEYPAD, 57407, 'u' },
+	{ KEYC_KP_NINE|KEYC_KEYPAD, 57408, 'u' },
+	{ KEYC_KP_PERIOD|KEYC_KEYPAD, 57409, 'u' },
+	{ KEYC_KP_SLASH|KEYC_KEYPAD, 57410, 'u' },
+	{ KEYC_KP_STAR|KEYC_KEYPAD, 57411, 'u' },
+	{ KEYC_KP_MINUS|KEYC_KEYPAD, 57412, 'u' },
+	{ KEYC_KP_PLUS|KEYC_KEYPAD, 57413, 'u' },
+	{ KEYC_KP_ENTER|KEYC_KEYPAD, 57414, 'u' },
+	{ KEYC_KP_EQUAL|KEYC_KEYPAD, 57415, 'u' },
+	{ KEYC_KP_SEPARATOR|KEYC_KEYPAD, 57416, 'u' },
+	{ KEYC_KP_LEFT|KEYC_KEYPAD, 57417, 'u' },
+	{ KEYC_KP_RIGHT|KEYC_KEYPAD, 57418, 'u' },
+	{ KEYC_KP_UP|KEYC_KEYPAD, 57419, 'u' },
+	{ KEYC_KP_DOWN|KEYC_KEYPAD, 57420, 'u' },
+	{ KEYC_KP_PPAGE|KEYC_KEYPAD, 57421, 'u' },
+	{ KEYC_KP_NPAGE|KEYC_KEYPAD, 57422, 'u' },
+	{ KEYC_KP_HOME|KEYC_KEYPAD, 57423, 'u' },
+	{ KEYC_KP_END|KEYC_KEYPAD, 57424, 'u' },
+	{ KEYC_KP_IC|KEYC_KEYPAD, 57425, 'u' },
+	{ KEYC_KP_DC|KEYC_KEYPAD, 57426, 'u' },
+	{ KEYC_KP_BEGIN|KEYC_KEYPAD, 57427, '~' },
+	{ KEYC_MEDIA_PLAY, 57428, 'u' },
+	{ KEYC_MEDIA_PAUSE, 57429, 'u' },
+	{ KEYC_MEDIA_PLAYPAUSE, 57430, 'u' },
+	{ KEYC_MEDIA_REVERSE, 57431, 'u' },
+	{ KEYC_MEDIA_STOP, 57432, 'u' },
+	{ KEYC_MEDIA_FASTFORWARD, 57433, 'u' },
+	{ KEYC_MEDIA_REWIND, 57434, 'u' },
+	{ KEYC_MEDIA_NEXT, 57435, 'u' },
+	{ KEYC_MEDIA_PREVIOUS, 57436, 'u' },
+	{ KEYC_MEDIA_RECORD, 57437, 'u' },
+	{ KEYC_VOLUME_DOWN, 57438, 'u' },
+	{ KEYC_VOLUME_UP, 57439, 'u' },
+	{ KEYC_VOLUME_MUTE, 57440, 'u' },
+	{ KEYC_LEFT_SHIFT, 57441, 'u' },
+	{ KEYC_LEFT_CTRL, 57442, 'u' },
+	{ KEYC_LEFT_ALT, 57443, 'u' },
+	{ KEYC_LEFT_SUPER, 57444, 'u' },
+	{ KEYC_LEFT_HYPER, 57445, 'u' },
+	{ KEYC_LEFT_META, 57446, 'u' },
+	{ KEYC_RIGHT_SHIFT, 57447, 'u' },
+	{ KEYC_RIGHT_CTRL, 57448, 'u' },
+	{ KEYC_RIGHT_ALT, 57449, 'u' },
+	{ KEYC_RIGHT_SUPER, 57450, 'u' },
+	{ KEYC_RIGHT_HYPER, 57451, 'u' },
+	{ KEYC_RIGHT_META, 57452, 'u' },
+	{ KEYC_ISO_LEVEL3_SHIFT, 57453, 'u' },
+	{ KEYC_ISO_LEVEL5_SHIFT, 57454, 'u' }
+};
+
+static u_int
+input_kitty_default_flags(void)
+{
+	if (options_get_number(global_options, "extended-keys") == 2 &&
+	    options_get_number(global_options, "extended-keys-format") ==
+	    EXTENDED_KEYS_KITTY)
+		return (KITTY_KEY_DISAMBIGUATE);
+	return (0);
+}
+
+void
+input_kitty_reset(struct screen *s)
+{
+	memset(&s->kitty_keys, 0, sizeof s->kitty_keys);
+	s->kitty_keys.flags = input_kitty_default_flags();
+}
+
+void
+input_kitty_alternate_on(struct screen *s)
+{
+	s->saved_kitty_keys = s->kitty_keys;
+	input_kitty_reset(s);
+}
+
+void
+input_kitty_alternate_off(struct screen *s)
+{
+	s->kitty_keys = s->saved_kitty_keys;
+	memset(&s->saved_kitty_keys, 0, sizeof s->saved_kitty_keys);
+}
+
+void
+input_kitty_set(struct screen *s, u_int flags, int mode)
+{
+	flags &= KITTY_KEY_SUPPORTED;
+	if (mode == 2)
+		s->kitty_keys.flags |= flags;
+	else if (mode == 3)
+		s->kitty_keys.flags &= ~flags;
+	else
+		s->kitty_keys.flags = flags;
+	s->kitty_keys.flags |= input_kitty_default_flags();
+}
+
+void
+input_kitty_push(struct screen *s, u_int flags)
+{
+	s->kitty_keys.saved_flags = s->kitty_keys.flags;
+	s->kitty_keys.have_saved = 1;
+	s->kitty_keys.flags = (flags & KITTY_KEY_SUPPORTED)|
+	    input_kitty_default_flags();
+}
+
+void
+input_kitty_pop(struct screen *s, u_int count)
+{
+	if (count == 0)
+		return;
+	if (s->kitty_keys.have_saved && count == 1)
+		s->kitty_keys.flags = s->kitty_keys.saved_flags;
+	else
+		s->kitty_keys.flags = input_kitty_default_flags();
+	s->kitty_keys.have_saved = 0;
+	s->kitty_keys.flags |= input_kitty_default_flags();
+}
+
+static u_int
+input_kitty_modifiers(key_code key)
+{
+	u_int	modifiers = 1;
+
+	if (key & KEYC_SHIFT)
+		modifiers += 1;
+	if (key & KEYC_META)
+		modifiers += 2;
+	if (key & KEYC_CTRL)
+		modifiers += 4;
+	if (key & KEYC_SUPER)
+		modifiers += 8;
+	if (key & KEYC_HYPER)
+		modifiers += 16;
+	return (modifiers);
+}
+
+static const struct input_kitty_key *
+input_kitty_lookup(key_code key)
+{
+	key_code	lookup;
+	u_int		i;
+
+	lookup = key & (KEYC_MASK_KEY|KEYC_KEYPAD);
+	for (i = 0; i < nitems(input_kitty_keys); i++) {
+		if (input_kitty_keys[i].key == lookup)
+			return (&input_kitty_keys[i]);
+	}
+	return (NULL);
+}
+
+int
+input_key_kitty(struct screen *s, struct bufferevent *bev, key_code key)
+{
+	const struct input_kitty_key	*ikk;
+	struct utf8_data			 ud;
+	wchar_t				 wc;
+	key_code			 modifiers, onlykey;
+	u_int				 flags, number, modifier;
+	char				 tmp[64];
+	size_t				 size;
+
+	flags = s->kitty_keys.flags & KITTY_KEY_SUPPORTED;
+	if (flags == 0)
+		return (-1);
+	if ((key & KEYC_MASK_KEY) == KEYC_BTAB)
+		key = C0_HT|(key & ~KEYC_MASK_KEY)|KEYC_SHIFT;
+
+	modifiers = key & (KEYC_SHIFT|KEYC_META|KEYC_CTRL|KEYC_SUPER|KEYC_HYPER);
+	ikk = input_kitty_lookup(key);
+	if (ikk != NULL) {
+		if ((flags & KITTY_KEY_REPORT_ALL) == 0) {
+			if (ikk->key == C0_CR || ikk->key == C0_HT ||
+			    ikk->key == KEYC_BSPACE)
+				return (-1);
+			if (ikk->final != 'u' &&
+			    (modifiers & (KEYC_SUPER|KEYC_HYPER)) == 0)
+				return (-1);
+		}
+		number = ikk->number;
+		modifier = input_kitty_modifiers(key);
+		if (ikk->final == 'u') {
+			if (modifier == 1)
+				size = xsnprintf(tmp, sizeof tmp, "\033[%uu", number);
+			else
+				size = xsnprintf(tmp, sizeof tmp, "\033[%u;%uu",
+				    number, modifier);
+		} else if (ikk->final == '~') {
+			if (modifier == 1)
+				size = xsnprintf(tmp, sizeof tmp, "\033[%u~", number);
+			else
+				size = xsnprintf(tmp, sizeof tmp, "\033[%u;%u~",
+				    number, modifier);
+		} else {
+			if (modifier == 1)
+				size = xsnprintf(tmp, sizeof tmp, "\033[%c",
+				    ikk->final);
+			else
+				size = xsnprintf(tmp, sizeof tmp, "\033[1;%u%c",
+				    modifier, ikk->final);
+		}
+		goto write;
+	}
+
+	if ((flags & KITTY_KEY_REPORT_ALL) == 0 &&
+	    (modifiers & (KEYC_META|KEYC_CTRL|KEYC_SUPER|KEYC_HYPER)) == 0)
+		return (-1);
+
+	onlykey = key & KEYC_MASK_KEY;
+	if (KEYC_IS_UNICODE(key)) {
+		utf8_to_data(onlykey, &ud);
+		if (utf8_towc(&ud, &wc) != UTF8_DONE)
+			return (-1);
+		number = wc;
+	} else if (onlykey <= 0x7f)
+		number = onlykey;
+	else
+		return (-1);
+	if ((key & KEYC_SHIFT) && number >= 'A' && number <= 'Z')
+		number += 'a' - 'A';
+
+	modifier = input_kitty_modifiers(key);
+	if (modifier == 1)
+		size = xsnprintf(tmp, sizeof tmp, "\033[%uu", number);
+	else
+		size = xsnprintf(tmp, sizeof tmp, "\033[%u;%uu", number,
+		    modifier);
+
+write:
+	log_debug("%s: %.*s", __func__, (int)size, tmp);
+	bufferevent_write(bev, tmp, size);
+	return (0);
+}

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 *);
@@ -279,6 +280,10 @@ enum input_csi_type {
 	INPUT_CSI_HPA,
 	INPUT_CSI_ICH,
 	INPUT_CSI_IL,
+	INPUT_CSI_KITTY_POP,
+	INPUT_CSI_KITTY_PUSH,
+	INPUT_CSI_KITTY_QUERY,
+	INPUT_CSI_KITTY_SET,
 	INPUT_CSI_MODOFF,
 	INPUT_CSI_MODSET,
 	INPUT_CSI_QUERY,
@@ -344,7 +349,11 @@ static const struct input_table_entry input_csi_table[] = {
 	{ 'r', "",  INPUT_CSI_DECSTBM },
 	{ 's', "",  INPUT_CSI_SCP },
 	{ 't', "",  INPUT_CSI_WINOPS },
-	{ 'u', "",  INPUT_CSI_RCP }
+	{ 'u', "",  INPUT_CSI_RCP },
+	{ 'u', "<", INPUT_CSI_KITTY_POP },
+	{ 'u', "=", INPUT_CSI_KITTY_SET },
+	{ 'u', ">", INPUT_CSI_KITTY_PUSH },
+	{ 'u', "?", INPUT_CSI_KITTY_QUERY }
 };
 
 /* Input transition. */
@@ -1171,6 +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, ...)
@@ -1525,6 +1557,9 @@ input_csi_dispatch(struct input_ctx *ictx)
 			screen_write_cursormove(sctx, m - 1, n - 1, 1);
 		break;
 	case INPUT_CSI_MODSET:
+		if (options_get_number(global_options, "extended-keys-format") ==
+		    EXTENDED_KEYS_KITTY)
+			break;
 		n = input_get(ictx, 0, 0, 0);
 		if (n != 4)
 			break;
@@ -1544,6 +1579,9 @@ input_csi_dispatch(struct input_ctx *ictx)
 			screen_write_mode_set(sctx, MODE_KEYS_EXTENDED);
 		break;
 	case INPUT_CSI_MODOFF:
+		if (options_get_number(global_options, "extended-keys-format") ==
+		    EXTENDED_KEYS_KITTY)
+			break;
 		n = input_get(ictx, 0, 0, 0);
 		if (n != 4)
 			break;
@@ -1557,6 +1595,44 @@ input_csi_dispatch(struct input_ctx *ictx)
 		if (options_get_number(global_options, "extended-keys") == 2)
 			screen_write_mode_set(sctx, MODE_KEYS_EXTENDED);
 		break;
+	case INPUT_CSI_KITTY_QUERY:
+		if (options_get_number(global_options, "extended-keys") == 0 ||
+		    options_get_number(global_options, "extended-keys-format") !=
+		    EXTENDED_KEYS_KITTY)
+			break;
+		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 ||
+		    options_get_number(global_options, "extended-keys-format") !=
+		    EXTENDED_KEYS_KITTY)
+			break;
+		n = input_get(ictx, 0, 0, 0);
+		m = input_get(ictx, 1, 1, 1);
+		if (n >= 0 && m >= 1 && m <= 3)
+			input_kitty_set(s, n, m);
+		break;
+	case INPUT_CSI_KITTY_PUSH:
+		if (options_get_number(global_options, "extended-keys") == 0 ||
+		    options_get_number(global_options, "extended-keys-format") !=
+		    EXTENDED_KEYS_KITTY)
+			break;
+		n = input_get(ictx, 0, 0, 0);
+		if (n >= 0)
+			input_kitty_push(s, n);
+		break;
+	case INPUT_CSI_KITTY_POP:
+		if (options_get_number(global_options, "extended-keys") == 0 ||
+		    options_get_number(global_options, "extended-keys-format") !=
+		    EXTENDED_KEYS_KITTY)
+			break;
+		n = input_get(ictx, 0, 1, 1);
+		if (n >= 0)
+			input_kitty_pop(s, n);
+		break;
 	case INPUT_CSI_WINOPS:
 		input_csi_dispatch_winops(ictx);
 		break;

key-string.c

@@ -45,6 +45,29 @@ static const struct {
 	{ "F10",	KEYC_F10|KEYC_IMPLIED_META },
 	{ "F11",	KEYC_F11|KEYC_IMPLIED_META },
 	{ "F12",	KEYC_F12|KEYC_IMPLIED_META },
+	{ "F13",	KEYC_F13|KEYC_IMPLIED_META },
+	{ "F14",	KEYC_F14|KEYC_IMPLIED_META },
+	{ "F15",	KEYC_F15|KEYC_IMPLIED_META },
+	{ "F16",	KEYC_F16|KEYC_IMPLIED_META },
+	{ "F17",	KEYC_F17|KEYC_IMPLIED_META },
+	{ "F18",	KEYC_F18|KEYC_IMPLIED_META },
+	{ "F19",	KEYC_F19|KEYC_IMPLIED_META },
+	{ "F20",	KEYC_F20|KEYC_IMPLIED_META },
+	{ "F21",	KEYC_F21|KEYC_IMPLIED_META },
+	{ "F22",	KEYC_F22|KEYC_IMPLIED_META },
+	{ "F23",	KEYC_F23|KEYC_IMPLIED_META },
+	{ "F24",	KEYC_F24|KEYC_IMPLIED_META },
+	{ "F25",	KEYC_F25|KEYC_IMPLIED_META },
+	{ "F26",	KEYC_F26|KEYC_IMPLIED_META },
+	{ "F27",	KEYC_F27|KEYC_IMPLIED_META },
+	{ "F28",	KEYC_F28|KEYC_IMPLIED_META },
+	{ "F29",	KEYC_F29|KEYC_IMPLIED_META },
+	{ "F30",	KEYC_F30|KEYC_IMPLIED_META },
+	{ "F31",	KEYC_F31|KEYC_IMPLIED_META },
+	{ "F32",	KEYC_F32|KEYC_IMPLIED_META },
+	{ "F33",	KEYC_F33|KEYC_IMPLIED_META },
+	{ "F34",	KEYC_F34|KEYC_IMPLIED_META },
+	{ "F35",	KEYC_F35|KEYC_IMPLIED_META },
 	{ "IC",		KEYC_IC|KEYC_IMPLIED_META },
 	{ "Insert",	KEYC_IC|KEYC_IMPLIED_META },
 	{ "DC",		KEYC_DC|KEYC_IMPLIED_META },
@@ -122,6 +145,54 @@ static const struct {
 	{ "KPEnter",	KEYC_KP_ENTER|KEYC_KEYPAD },
 	{ "KP0",	KEYC_KP_ZERO|KEYC_KEYPAD },
 	{ "KP.",	KEYC_KP_PERIOD|KEYC_KEYPAD },
+	{ "KP=",	KEYC_KP_EQUAL|KEYC_KEYPAD },
+	{ "KP,",	KEYC_KP_SEPARATOR|KEYC_KEYPAD },
+	{ "KPLeft",	KEYC_KP_LEFT|KEYC_KEYPAD },
+	{ "KPRight",	KEYC_KP_RIGHT|KEYC_KEYPAD },
+	{ "KPUp",	KEYC_KP_UP|KEYC_KEYPAD },
+	{ "KPDown",	KEYC_KP_DOWN|KEYC_KEYPAD },
+	{ "KPPageUp",	KEYC_KP_PPAGE|KEYC_KEYPAD },
+	{ "KPPageDown",	KEYC_KP_NPAGE|KEYC_KEYPAD },
+	{ "KPHome",	KEYC_KP_HOME|KEYC_KEYPAD },
+	{ "KPEnd",	KEYC_KP_END|KEYC_KEYPAD },
+	{ "KPInsert",	KEYC_KP_IC|KEYC_KEYPAD },
+	{ "KPDelete",	KEYC_KP_DC|KEYC_KEYPAD },
+	{ "KPBegin",	KEYC_KP_BEGIN|KEYC_KEYPAD },
+
+	/* Other function keys. */
+	{ "CapsLock",	KEYC_CAPSLOCK },
+	{ "ScrollLock",	KEYC_SCROLLLOCK },
+	{ "NumLock",	KEYC_NUMLOCK },
+	{ "PrintScreen", KEYC_PRINTSCREEN },
+	{ "Pause",	KEYC_PAUSE },
+	{ "Menu",	KEYC_MENU },
+	{ "MediaPlay",	KEYC_MEDIA_PLAY },
+	{ "MediaPause", KEYC_MEDIA_PAUSE },
+	{ "MediaPlayPause", KEYC_MEDIA_PLAYPAUSE },
+	{ "MediaReverse", KEYC_MEDIA_REVERSE },
+	{ "MediaStop",	KEYC_MEDIA_STOP },
+	{ "MediaFastForward", KEYC_MEDIA_FASTFORWARD },
+	{ "MediaRewind", KEYC_MEDIA_REWIND },
+	{ "MediaNext",	KEYC_MEDIA_NEXT },
+	{ "MediaPrevious", KEYC_MEDIA_PREVIOUS },
+	{ "MediaRecord", KEYC_MEDIA_RECORD },
+	{ "VolumeDown", KEYC_VOLUME_DOWN },
+	{ "VolumeUp",	KEYC_VOLUME_UP },
+	{ "VolumeMute", KEYC_VOLUME_MUTE },
+	{ "LeftShift",	KEYC_LEFT_SHIFT },
+	{ "LeftControl", KEYC_LEFT_CTRL },
+	{ "LeftAlt",	KEYC_LEFT_ALT },
+	{ "LeftSuper",	KEYC_LEFT_SUPER },
+	{ "LeftHyper",	KEYC_LEFT_HYPER },
+	{ "LeftMeta",	KEYC_LEFT_META },
+	{ "RightShift", KEYC_RIGHT_SHIFT },
+	{ "RightControl", KEYC_RIGHT_CTRL },
+	{ "RightAlt",	KEYC_RIGHT_ALT },
+	{ "RightSuper", KEYC_RIGHT_SUPER },
+	{ "RightHyper", KEYC_RIGHT_HYPER },
+	{ "RightMeta",	KEYC_RIGHT_META },
+	{ "ISOLevel3Shift", KEYC_ISO_LEVEL3_SHIFT },
+	{ "ISOLevel5Shift", KEYC_ISO_LEVEL5_SHIFT },
 
 	/* Mouse keys. */
 	KEYC_MOUSE_STRING(MOUSEDOWN1, MouseDown1),
@@ -226,9 +297,14 @@ key_string_get_modifiers(const char **string)
 			modifiers |= KEYC_META;
 			break;
 		case 'S':
-		case 's':
 			modifiers |= KEYC_SHIFT;
 			break;
+		case 's':
+			modifiers |= KEYC_SUPER;
+			break;
+		case 'H':
+			modifiers |= KEYC_HYPER;
+			break;
 		default:
 			*string = NULL;
 			return (0);
@@ -349,6 +425,10 @@ key_string_lookup_key(key_code key, int with_flags)
 		strlcat(out, "M-", sizeof out);
 	if (key & KEYC_SHIFT)
 		strlcat(out, "S-", sizeof out);
+	if (key & KEYC_SUPER)
+		strlcat(out, "s-", sizeof out);
+	if (key & KEYC_HYPER)
+		strlcat(out, "H-", sizeof out);
 	key &= KEYC_MASK_KEY;
 
 	/* Handle no key. */

options-table.c

@@ -104,7 +104,7 @@ static const char *options_table_extended_keys_list[] = {
 	"off", "on", "always", NULL
 };
 static const char *options_table_extended_keys_format_list[] = {
-	"csi-u", "xterm", NULL
+	"csi-u", "xterm", "kitty", NULL
 };
 static const char *options_table_allow_passthrough_list[] = {
 	"off", "on", "all", NULL

popup.c

@@ -449,7 +449,8 @@ popup_key_cb(struct client *c, void *data, struct key_event *event)
 			bufferevent_write(job_get_event(pd->job), buf, len);
 			return (0);
 		}
-		input_key(&pd->s, job_get_event(pd->job), event->key);
+		input_key(&pd->s, job_get_event(pd->job), event->key,
+		    input_key_client_supports_extended(pd->c, event->key));
 	}
 	return (0);
 

regress/kitty-keys-clients.sh

@@ -0,0 +1,144 @@
+#!/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$$"
+
+printf '%s\n' 'set -g extended-keys on' \
+    'set -g extended-keys-format kitty' >"$KCONF"
+printf '%s\n' 'set -g extended-keys on' \
+    'set -g extended-keys-format csi-u' >"$UCONF"
+printf '%s\n' 'set -g extended-keys off' >"$LCONF"
+
+cleanup()
+{
+	rm -f "$KCONF" "$UCONF" "$LCONF" "$OUT" "$TMP"
+	for socket in $SOCKETS; do
+		$TEST_TMUX -L"$socket" kill-server 2>/dev/null
+	done
+}
+trap cleanup 0 1 15
+
+wait_for_mode()
+{
+	tmux=$1
+	wanted=$2
+	i=0
+	while [ "$($tmux display-message -pt: '#{pane_key_mode}')" != "$wanted" ] &&
+	    [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ "$($tmux display-message -pt: '#{pane_key_mode}')" = "$wanted" ]
+}
+
+wait_for_output()
+{
+	i=0
+	while [ ! -s "$1" ] && [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ -s "$1" ]
+}
+
+client_mode()
+{
+	tmux=$1
+	session=$2
+
+	if [ -z "$session" ]; then
+		$tmux list-clients -F '#{client_key_mode}'
+	else
+		$tmux list-clients -F '#{client_session}:#{client_key_mode}' |
+		    sed -n "s/^$session://p"
+	fi
+}
+
+wait_for_client_mode()
+{
+	tmux=$1
+	session=$2
+	wanted=$3
+	i=0
+	while [ "$(client_mode "$tmux" "$session")" != "$wanted" ] &&
+	    [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ "$(client_mode "$tmux" "$session")" = "$wanted" ]
+}
+
+# A server preferring Kitty must negotiate each client independently.
+M="$TEST_TMUX -LtestKmc$$ -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 "$UA" 'Ext 2' || exit 1
+
+# Each client must report the protocol its own terminal negotiated.
+wait_for_client_mode "$M" kitty 'Kitty 1' || exit 1
+wait_for_client_mode "$M" csiu 'Ext' || exit 1
+
+uc=$($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
+
+# A Kitty-capable terminal must still be reported when it is not in use.
+$M set-option -g extended-keys off
+wait_for_client_mode "$M" kitty 'VT10x (Kitty)' || exit 1
+wait_for_client_mode "$M" csiu 'VT10x' || exit 1
+$M set-option -g extended-keys on
+wait_for_client_mode "$M" kitty 'Kitty 1' || exit 1
+
+$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
+wait_for_client_mode "$R" '' 'Ext' || exit 1
+$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
+wait_for_client_mode "$LQ" '' 'VT10x' || exit 1
+
+exit 0

regress/kitty-keys-input.sh

@@ -0,0 +1,119 @@
+#!/bin/sh
+
+# Test client-side Kitty keyboard protocol support: an outer tmux acts as a
+# Kitty-capable terminal for the inner tmux which is the one under test. The
+# inner tmux queries the outer one, the outer one replies, and the inner one
+# then parses the key sequences sent to it.
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+CONF=$(mktemp)
+TMP=$(mktemp)
+
+printf '%s\n' 'set -g extended-keys on' \
+    'set -g extended-keys-format kitty' >"$CONF"
+
+TMUX="$TEST_TMUX -LtestKIA$$ -f$CONF"
+TMUX2="$TEST_TMUX -LtestKIB$$ -f$CONF"
+
+trap 'rm -f "$CONF" "$TMP"; $TMUX kill-server 2>/dev/null; \
+    $TMUX2 kill-server 2>/dev/null' 0 1 15
+
+$TMUX2 new-session -d -x80 -y24 || exit 1
+$TMUX new-session -d -x80 -y24 "$TMUX2 attach" || exit 1
+
+exit_status=0
+
+wait_for_mode()
+{
+	i=0
+	while [ "$($TMUX display-message -pt: '#{pane_key_mode}')" != "$1" ] &&
+	    [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ "$($TMUX display-message -pt: '#{pane_key_mode}')" = "$1" ]
+}
+
+assert_key()
+{
+	keys=$1
+	expected=$2
+
+	$TMUX2 command-prompt -k 'display-message -pl "%%"' >"$TMP" &
+	sleep 0.15
+	$TMUX send-keys $keys
+	wait
+
+	actual=$(tr -d '[:space:]' <"$TMP")
+	if [ "$actual" = "$expected" ]; then
+		[ -n "$VERBOSE" ] && echo "[PASS] $keys -> $actual"
+	else
+		echo "[FAIL] $keys -> $expected (got '$actual')"
+		exit_status=1
+	fi
+}
+
+# The inner tmux must detect the outer one and push its flags.
+if ! wait_for_mode 'Kitty 1'; then
+	echo "[FAIL] inner tmux did not enable the Kitty protocol"
+	exit 1
+fi
+
+# The handshake is done, so stop the outer tmux encoding the raw sequences
+# below as Kitty keys itself.
+$TMUX set-option -g extended-keys-format csi-u
+
+# Modifiers, including the Kitty-only Super and Hyper.
+assert_key 'Escape [97;2u' 'S-a'
+assert_key 'Escape [97;3u' 'M-a'
+assert_key 'Escape [97;5u' 'C-a'
+assert_key 'Escape [97;6u' 'C-S-a'
+assert_key 'Escape [97;7u' 'C-M-a'
+assert_key 'Escape [97;9u' 's-a'
+assert_key 'Escape [97;17u' 'H-a'
+assert_key 'Escape [65;2u' 'S-A'
+
+# Keys with a dedicated tmux key code.
+assert_key 'Escape [9;5u' 'C-Tab'
+assert_key 'Escape [9;2u' 'BTab'
+assert_key 'Escape [13;5u' 'C-Enter'
+assert_key 'Escape [27u' 'Escape'
+assert_key 'Escape [32;5u' 'C-Space'
+assert_key 'Escape [127;5u' 'C-BSpace'
+
+# Keys with a CSI final byte other than u.
+assert_key 'Escape [1;5A' 'C-Up'
+assert_key 'Escape [1;3D' 'M-Left'
+assert_key 'Escape [1;5H' 'C-Home'
+assert_key 'Escape [1;5P' 'C-F1'
+
+# Functional and non-ASCII keys.
+assert_key 'Escape [57399;5u' 'C-KP0'
+assert_key 'Escape [233;5u' 'C-é'
+
+# The alternate key and associated text fields are not requested but must be
+# ignored if a terminal sends them anyway.
+assert_key 'Escape [97:65;2u' 'S-a'
+assert_key 'Escape [97:65:97;5u' 'C-a'
+assert_key 'Escape [97;5;97u' 'C-a'
+
+# A repeat event is a key press, a release event is dropped. The C-b that
+# follows shows that the sequence was consumed and not passed through.
+assert_key 'Escape [97;5:1u' 'C-a'
+assert_key 'Escape [97;5:2u' 'C-a'
+assert_key 'Escape [97;5:3u Escape [98;5u' 'C-b'
+
+# The Meta modifier bit is not representable and is dropped.
+assert_key 'Escape [97;33u Escape [98;5u' 'C-b'
+
+# Lock modifiers are ignored rather than dropping the key.
+assert_key 'Escape [97;65u' 'a'
+assert_key 'Escape [97;129u' 'a'
+
+$TMUX kill-server 2>/dev/null
+$TMUX2 kill-server 2>/dev/null
+
+exit $exit_status

regress/kitty-keys-terminal.sh

@@ -0,0 +1,85 @@
+#!/bin/sh
+
+# Test the Kitty keyboard protocol against a real terminal rather than against
+# another copy of tmux. This drives kitty through its remote control interface
+# so that kitty itself encodes the key presses.
+#
+# This has to be run by hand from this directory. The Makefile runs tests with
+# env -i, which removes DISPLAY and HOME, so kitty cannot start and this exits
+# immediately without testing anything. It is also skipped unless kitty is
+# installed and is new enough to have send-key.
+
+PATH=/bin:/usr/bin
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+
+command -v kitty >/dev/null 2>&1 || exit 0
+[ -n "$DISPLAY" ] || [ -n "$WAYLAND_DISPLAY" ] || exit 0
+kitty @ --help 2>/dev/null | grep -q 'send-key' || exit 0
+
+DIR=$(mktemp -d)
+CONF=$DIR/conf
+SOCKET=$DIR/kitty
+OUT=$DIR/out
+TMUX="$TEST_TMUX -LtestKrt$$ -f$CONF"
+
+printf '%s\n' 'set -g extended-keys on' \
+    'set -g extended-keys-format kitty' >"$CONF"
+
+cleanup()
+{
+	$TMUX kill-server 2>/dev/null
+	rm -rf "$DIR"
+}
+trap cleanup 0 1 15
+
+kitty -o allow_remote_control=yes --listen-on "unix:$SOCKET" \
+    -o confirm_os_window_close=0 -e \
+    $TMUX new-session -s r "sleep 120" >"$DIR/err" 2>&1 &
+
+# The terminfo entry for kitty may be missing, so treat a server which never
+# appears as a reason to skip rather than as a failure.
+i=0
+while ! $TMUX has-session -t r 2>/dev/null && [ "$i" -lt 150 ]; do
+	sleep 0.1
+	i=$((i + 1))
+done
+$TMUX has-session -t r 2>/dev/null || exit 0
+
+# The client must negotiate the protocol with the real terminal.
+i=0
+while [ "$($TMUX list-clients -F '#{client_key_mode}')" != 'Kitty 1' ] &&
+    [ "$i" -lt 100 ]; do
+	sleep 0.1
+	i=$((i + 1))
+done
+[ "$($TMUX list-clients -F '#{client_key_mode}')" = 'Kitty 1' ] || exit 1
+
+# kitty encodes the key, tmux parses it and encodes it again for the pane.
+try_key()
+{
+	key=$1
+	expected=$2
+
+	: >"$OUT"
+	$TMUX respawn-pane -k -t r: \
+	    "stty raw -echo; printf '\033[>1u'; dd bs=1 count=7 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 20" || return 1
+	sleep 1
+	kitty @ --to "unix:$SOCKET" send-key "$key" 2>/dev/null || return 1
+	i=0
+	while [ ! -s "$OUT" ] && [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ "$(tr -d ' \n' <"$OUT")" = "$expected" ]
+}
+
+try_key ctrl+a '1b5b39373b3575' || exit 1
+try_key alt+a '1b5b39373b3375' || exit 1
+try_key ctrl+shift+a '1b5b39373b3675' || exit 1
+
+# Super cannot be represented by the standard extended keys at all, so this
+# only succeeds if the whole chain used the Kitty protocol.
+try_key super+a '1b5b39373b3975' || exit 1
+
+exit 0

regress/kitty-keys.sh

@@ -0,0 +1,107 @@
+#!/bin/sh
+
+# Test pane-side Kitty keyboard protocol state and key encoding. This uses
+# synthetic protocol sequences and does not require a particular terminal.
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+CONF=$(mktemp)
+OUT=$(mktemp)
+TMUX="$TEST_TMUX -LtestK$$ -f$CONF"
+
+trap 'rm -f "$CONF" "$OUT"; $TMUX kill-server 2>/dev/null' 0 1 15
+
+printf '%s\n' 'set -g extended-keys on' \
+    'set -g extended-keys-format kitty' >"$CONF"
+
+wait_for_output()
+{
+	i=0
+	while [ ! -s "$OUT" ] && [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ -s "$OUT" ]
+}
+
+wait_for_mode()
+{
+	wanted=$1
+	i=0
+	while [ "$($TMUX display-message -pt: '#{pane_key_mode}')" != "$wanted" ] &&
+	    [ "$i" -lt 50 ]; do
+		sleep 0.1
+		i=$((i + 1))
+	done
+	[ "$($TMUX display-message -pt: '#{pane_key_mode}')" = "$wanted" ]
+}
+
+check_output()
+{
+	expected=$1
+	actual=$(tr -d ' \n' <"$OUT")
+	if [ "$actual" != "$expected" ]; then
+		echo "expected $expected, got $actual"
+		exit 1
+	fi
+}
+
+$TMUX new-session -d -x80 -y24 \
+    "stty raw -echo; printf '\033[>1u'; dd bs=1 count=7 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5" || exit 1
+wait_for_mode 'Kitty 1'
+$TMUX send-keys -t: C-S-a
+wait_for_output
+check_output 1b5b39373b3675
+
+: >"$OUT"
+$TMUX respawn-pane -k -t: \
+    "stty raw -echo; printf '\033[>1u'; dd bs=1 count=7 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5"
+wait_for_mode 'Kitty 1'
+$TMUX send-keys -t: s-a
+wait_for_output
+check_output 1b5b39373b3975
+
+: >"$OUT"
+$TMUX respawn-pane -k -t: \
+    "stty raw -echo; printf '\033[>8u'; dd bs=1 count=5 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5"
+wait_for_mode 'Kitty 8'
+$TMUX send-keys -t: a
+wait_for_output
+check_output 1b5b393775
+
+: >"$OUT"
+$TMUX respawn-pane -k -t: \
+    "stty raw -echo; printf '\033[>1u\033[?u'; dd bs=1 count=5 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5"
+wait_for_output
+check_output 1b5b3f3175
+
+: >"$OUT"
+$TMUX respawn-pane -k -t: \
+    "stty raw -echo; printf '\033[>4;2m\033[?u'; dd bs=1 count=5 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5"
+wait_for_output
+check_output 1b5b3f3075
+
+: >"$OUT"
+$TMUX respawn-pane -k -t: \
+    "stty raw -echo; printf '\033[>1u\033[>8u\033[<u\033[?u\033[>8u\033[<2u\033[?u'; dd bs=1 count=10 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5"
+wait_for_output
+check_output 1b5b3f31751b5b3f3075
+
+: >"$OUT"
+$TMUX set-option -g extended-keys always
+$TMUX respawn-pane -k -t: \
+    "stty raw -echo; printf '\033[>0u\033[?u'; dd bs=1 count=5 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5"
+wait_for_output
+check_output 1b5b3f3175
+$TMUX set-option -g extended-keys on
+
+: >"$OUT"
+$TMUX respawn-pane -k -t: \
+    "stty raw -echo; printf '\033[>1u\033[?u\033[?1049h\033[?u\033[>8u\033[?u\033[?1049l\033[?u'; dd bs=1 count=20 2>/dev/null | od -An -v -t x1 >'$OUT'; sleep 5"
+wait_for_output
+check_output 1b5b3f31751b5b3f30751b5b3f38751b5b3f3175
+
+$TMUX kill-server 2>/dev/null
+exit 0

screen-write.c

@@ -437,8 +437,11 @@ screen_write_reset(struct screen_write_ctx *ctx)
 
 	s->mode = MODE_CURSOR|MODE_WRAP;
 
-	if (options_get_number(global_options, "extended-keys") == 2)
+	if (options_get_number(global_options, "extended-keys") == 2 &&
+	    options_get_number(global_options, "extended-keys-format") !=
+	    EXTENDED_KEYS_KITTY)
 		s->mode = (s->mode & ~EXTENDED_KEY_MODES)|MODE_KEYS_EXTENDED;
+	input_kitty_reset(s);
 
 	screen_write_clearscreen(ctx, 8);
 	screen_write_set_cursor(ctx, 0, 0);

screen.c

@@ -88,6 +88,8 @@ screen_init(struct screen *s, u_int sx, u_int sy, u_int hlimit)
 	s->default_cstyle = SCREEN_CURSOR_DEFAULT;
 	s->mode = MODE_CURSOR;
 	s->default_mode = 0;
+	memset(&s->kitty_keys, 0, sizeof s->kitty_keys);
+	memset(&s->saved_kitty_keys, 0, sizeof s->saved_kitty_keys);
 	s->ccolour = -1;
 	s->default_ccolour = -1;
 	s->tabs = NULL;
@@ -116,11 +118,13 @@ screen_reinit(struct screen *s, int check)
 
 	s->mode = MODE_CURSOR|MODE_WRAP|(s->mode & MODE_CRLF);
 
-	if (options_get_number(global_options, "extended-keys") == 2)
+	if (options_get_number(global_options, "extended-keys") == 2 &&
+	    options_get_number(global_options, "extended-keys-format") !=
+	    EXTENDED_KEYS_KITTY)
 		s->mode = (s->mode & ~EXTENDED_KEY_MODES)|MODE_KEYS_EXTENDED;
-
 	if (SCREEN_IS_ALTERNATE(s))
 		screen_alternate_off(s, NULL, 0);
+	input_kitty_reset(s);
 	s->saved_cx = UINT_MAX;
 	s->saved_cy = UINT_MAX;
 
@@ -698,6 +702,7 @@ screen_alternate_on(struct screen *s, struct grid_cell *gc, int cursor)
 
 	if (SCREEN_IS_ALTERNATE(s))
 		return 0;
+	input_kitty_alternate_on(s);
 	sx = screen_size_x(s);
 	sy = screen_size_y(s);
 
@@ -758,6 +763,7 @@ screen_alternate_off(struct screen *s, struct grid_cell *gc, int cursor)
 			s->cy = screen_size_y(s) - 1;
 		return 0;
 	}
+	input_kitty_alternate_off(s);
 
 	/* Restore the saved grid. */
 	grid_duplicate_lines(s->grid, screen_hsize(s), s->saved_grid, 0,

server-client.c

@@ -2194,6 +2194,7 @@ server_client_reset_state(struct client *c)
 		log_debug("%s: client %s mode %s", __func__, c->name,
 		    screen_mode_to_string(mode));
 	}
+	tty_update_kitty(tty, s);
 
 	/* Reset region and margin. */
 	tty_region_off(tty);

tmux.1

@@ -4907,12 +4907,18 @@ If enabled, the server will exit when there are no attached clients.
 .It Xo Ic extended\-keys
 .Op Ic on | off | always
 .Xc
-Controls how modified keys (keys pressed together with Control, Meta, or Shift)
+Controls how modified keys are reported.
-are reported.
+For the
-This is the equivalent of the
+.Ic csi\-u
+and
+.Ic xterm
+formats, this controls the
 .Ic modifyOtherKeys
 .Xr xterm 1
 resource.
+For the
+.Ic kitty
+format, this controls the progressive keyboard protocol enhancements.
 .Pp
 When set to
 .Ic on ,
@@ -4923,12 +4929,25 @@ When set to
 .Ic always ,
 modes 1 and 2 can still be requested by applications, but mode 1 will be forced
 instead of the standard mode.
+This applies only to applications inside panes and does not change what
+.Nm
+requests from the terminal.
 When set to
 .Ic off ,
 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.
+A Kitty keyboard state query reflects the clients attached to the window at
+the time of the query; if none are attached, the requested state is reported.
+Applications are not notified if client support changes after the reply.
 See also the
 .Ic extkeys
 feature for the
@@ -4937,13 +4956,28 @@ option, the
 .Ic extended\-keys\-format
 option and the
 .Ic pane_key_mode
-variable.
+and
+.Ic client_key_mode
+variables.
 .It Xo Ic extended\-keys\-format
-.Op Ic csi\-u | xterm
+.Op Ic csi\-u | xterm | kitty
 .Xc
-Selects one of the two possible formats for reporting modified keys to
+Selects the format for reporting modified keys to applications.
-applications.
+The
-This is the equivalent of the
+.Ic kitty
+format uses the Kitty keyboard protocol and supports the Super and Hyper
+modifiers.
+Their key name prefixes are
+.Ql s-
+and
+.Ql H- .
+The disambiguate and report-all enhancements are supported; event types,
+alternate keys and associated text are not requested.
+For the
+.Ic csi\-u
+and
+.Ic xterm
+formats, this is the equivalent of the
 .Ic formatOtherKeys
 .Xr xterm 1
 resource.
@@ -4955,6 +4989,10 @@ and as
 .Ql \[ha][[65;6u
 when set to
 .Ic csi\-u .
+With
+.Ic kitty ,
+it will be reported as
+.Ql \[ha][[97;6u .
 .It Xo Ic focus\-events
 .Op Ic on | off
 .Xc
@@ -7309,6 +7347,7 @@ The following variables are available, where appropriate:
 .It Li "client_discarded" Ta "" Ta "Bytes discarded when client behind"
 .It Li "client_flags" Ta "" Ta "List of client flags"
 .It Li "client_height" Ta "" Ta "Height of client"
+.It Li "client_key_mode" Ta "" Ta "Extended key reporting mode for this client"
 .It Li "client_key_table" Ta "" Ta "Current key table"
 .It Li "client_last_session" Ta "" Ta "Name of the client's last session"
 .It Li "client_name" Ta "" Ta "Name of client"
@@ -8328,17 +8367,11 @@ Otherwise, the format of
 .Ar message
 is described in the
 .Sx FORMATS
-section; session, window and pane information is taken from
+section; information is taken from
 .Ar target\-pane
 if
 .Fl t
 is given, otherwise the active pane.
-If
-.Fl c
-is given, the
-.Ql #{client_*}
-variables are taken from
-.Ar target\-client .
 .Pp
 If
 .Fl j

tmux.h

@@ -142,6 +142,8 @@ struct winlink;
 #define VISUAL_BOTH 2
 
 /* Key modifier bits. */
+#define KEYC_SUPER           0x00010000000000ULL
+#define KEYC_HYPER           0x00020000000000ULL
 #define KEYC_META            0x00100000000000ULL
 #define KEYC_CTRL            0x00200000000000ULL
 #define KEYC_SHIFT           0x00400000000000ULL
@@ -374,6 +376,29 @@ enum {
 	KEYC_F10,
 	KEYC_F11,
 	KEYC_F12,
+	KEYC_F13,
+	KEYC_F14,
+	KEYC_F15,
+	KEYC_F16,
+	KEYC_F17,
+	KEYC_F18,
+	KEYC_F19,
+	KEYC_F20,
+	KEYC_F21,
+	KEYC_F22,
+	KEYC_F23,
+	KEYC_F24,
+	KEYC_F25,
+	KEYC_F26,
+	KEYC_F27,
+	KEYC_F28,
+	KEYC_F29,
+	KEYC_F30,
+	KEYC_F31,
+	KEYC_F32,
+	KEYC_F33,
+	KEYC_F34,
+	KEYC_F35,
 	KEYC_IC,
 	KEYC_DC,
 	KEYC_HOME,
@@ -405,6 +430,54 @@ enum {
 	KEYC_KP_ENTER,
 	KEYC_KP_ZERO,
 	KEYC_KP_PERIOD,
+	KEYC_KP_EQUAL,
+	KEYC_KP_SEPARATOR,
+	KEYC_KP_LEFT,
+	KEYC_KP_RIGHT,
+	KEYC_KP_UP,
+	KEYC_KP_DOWN,
+	KEYC_KP_PPAGE,
+	KEYC_KP_NPAGE,
+	KEYC_KP_HOME,
+	KEYC_KP_END,
+	KEYC_KP_IC,
+	KEYC_KP_DC,
+	KEYC_KP_BEGIN,
+
+	/* Other function keys. */
+	KEYC_CAPSLOCK,
+	KEYC_SCROLLLOCK,
+	KEYC_NUMLOCK,
+	KEYC_PRINTSCREEN,
+	KEYC_PAUSE,
+	KEYC_MENU,
+	KEYC_MEDIA_PLAY,
+	KEYC_MEDIA_PAUSE,
+	KEYC_MEDIA_PLAYPAUSE,
+	KEYC_MEDIA_REVERSE,
+	KEYC_MEDIA_STOP,
+	KEYC_MEDIA_FASTFORWARD,
+	KEYC_MEDIA_REWIND,
+	KEYC_MEDIA_NEXT,
+	KEYC_MEDIA_PREVIOUS,
+	KEYC_MEDIA_RECORD,
+	KEYC_VOLUME_DOWN,
+	KEYC_VOLUME_UP,
+	KEYC_VOLUME_MUTE,
+	KEYC_LEFT_SHIFT,
+	KEYC_LEFT_CTRL,
+	KEYC_LEFT_ALT,
+	KEYC_LEFT_SUPER,
+	KEYC_LEFT_HYPER,
+	KEYC_LEFT_META,
+	KEYC_RIGHT_SHIFT,
+	KEYC_RIGHT_CTRL,
+	KEYC_RIGHT_ALT,
+	KEYC_RIGHT_SUPER,
+	KEYC_RIGHT_HYPER,
+	KEYC_RIGHT_META,
+	KEYC_ISO_LEVEL3_SHIFT,
+	KEYC_ISO_LEVEL5_SHIFT,
 
 	/* Theme reporting. */
 	KEYC_REPORT_DARK_THEME,
@@ -702,6 +775,16 @@ enum tty_code_code {
 #define CURSOR_MODES (MODE_CURSOR|MODE_CURSOR_BLINKING|MODE_CURSOR_VERY_VISIBLE)
 #define EXTENDED_KEY_MODES (MODE_KEYS_EXTENDED|MODE_KEYS_EXTENDED_2)
 
+/* Extended key output formats. */
+#define EXTENDED_KEYS_CSI_U 0
+#define EXTENDED_KEYS_XTERM 1
+#define EXTENDED_KEYS_KITTY 2
+
+/* Supported Kitty keyboard protocol flags. */
+#define KITTY_KEY_DISAMBIGUATE 0x1
+#define KITTY_KEY_REPORT_ALL 0x8
+#define KITTY_KEY_SUPPORTED (KITTY_KEY_DISAMBIGUATE|KITTY_KEY_REPORT_ALL)
+
 /* Mouse protocol constants. */
 #define MOUSE_PARAM_MAX 0xff
 #define MOUSE_PARAM_UTF8_MAX 0x7ff
@@ -1068,6 +1151,11 @@ struct progress_bar {
 /* Virtual screen. */
 struct screen_sel;
 struct screen_titles;
+struct kitty_key_state {
+	u_int	flags;
+	u_int	saved_flags;
+	int	have_saved;
+};
 struct screen {
 	char				*title;
 	char				*path;
@@ -1089,6 +1177,8 @@ struct screen {
 
 	int				 mode;
 	int				 default_mode;
+	struct kitty_key_state		 kitty_keys;
+	struct kitty_key_state		 saved_kitty_keys;
 
 	u_int				 saved_cx;
 	u_int				 saved_cy;
@@ -1819,9 +1909,13 @@ struct tty {
 #define TTY_WAITBG 0x4000
 #define TTY_BRACKETPASTE 0x8000
 #define TTY_HAVESYNC 0x10000
+#define TTY_HAVEKKB 0x20000
+#define TTY_KKBPUSHED 0x40000
+#define TTY_KKBSUPPORT 0x80000
 #define TTY_ALL_REQUEST_FLAGS \
-	(TTY_HAVEDA|TTY_HAVEDA2|TTY_HAVEXDA|TTY_HAVESYNC)
+	(TTY_HAVEDA|TTY_HAVEDA2|TTY_HAVEXDA|TTY_HAVESYNC|TTY_HAVEKKB)
 	int		 flags;
+	u_int		 kitty_keys;
 
 	struct tty_term	*term;
 
@@ -2974,6 +3068,7 @@ int	tty_open(struct tty *, char **);
 void	tty_close(struct tty *);
 void	tty_free(struct tty *);
 void	tty_update_features(struct tty *);
+void	tty_update_kitty(struct tty *, struct screen *);
 void	tty_set_selection(struct tty *, const char *, const char *, size_t);
 void	tty_write(void (*)(struct tty *, const struct tty_ctx *),
 	    struct tty_ctx *);
@@ -3450,10 +3545,26 @@ void	 input_cancel_requests(struct client *);
 
 /* input-key.c */
 void	 input_key_build(void);
-int	 input_key_pane(struct window_pane *, key_code, struct mouse_event *);
+int	 input_key_pane(struct window_pane *, key_code, struct mouse_event *,
-int	 input_key(struct screen *, struct bufferevent *, key_code);
+	     int);
+int	 input_key(struct screen *, struct bufferevent *, key_code, int);
 int	 input_key_get_mouse(struct screen *, struct mouse_event *, u_int,
 	     u_int, const char **, size_t *);
+int	 input_key_client_supports_extended(struct client *, key_code);
+
+/* input-kitty.c */
+void	 input_kitty_reset(struct screen *);
+void	 input_kitty_alternate_on(struct screen *);
+void	 input_kitty_alternate_off(struct screen *);
+void	 input_kitty_set(struct screen *, u_int, int);
+void	 input_kitty_push(struct screen *, u_int);
+void	 input_kitty_pop(struct screen *, u_int);
+int	 input_key_kitty(struct screen *, struct bufferevent *, key_code);
+
+/* tty-kitty.c */
+int	 tty_keys_kitty(struct tty *, const char *, size_t, size_t *,
+	     key_code *);
+int	 tty_keys_kitty_query(struct tty *, const char *, size_t, size_t *);
 
 /* colour.c */
 int	 colour_find_rgb(u_char, u_char, u_char);

tty-keys.c

@@ -772,6 +772,17 @@ tty_keys_next(struct tty *tty)
 		goto partial_key;
 	}
 
+	/* Is this a Kitty keyboard protocol response? */
+	switch (tty_keys_kitty_query(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 synchronized update mode response? */
 	switch (tty_keys_sync(tty, buf, len, &size)) {
 	case 0:		/* yes */
@@ -858,6 +869,18 @@ tty_keys_next(struct tty *tty)
 		goto partial_key;
 	}
 
+	/* Is this an extended key press? */
+	switch (tty_keys_kitty(tty, buf, len, &size, &key)) {
+	case 0:		/* yes */
+		goto complete_key;
+	case -1:	/* no, or not valid */
+		break;
+	case -2:	/* yes, but not representable by tmux */
+		goto discard_key;
+	case 1:		/* partial */
+		goto partial_key;
+	}
+
 	/* Is this an extended key press? */
 	switch (tty_keys_extended_key(tty, buf, len, &size, &key)) {
 	case 0:		/* yes */
@@ -1089,6 +1112,8 @@ tty_keys_extended_key(struct tty *tty, const char *buf, size_t len,
 	utf8_char	 uc;
 
 	*size = 0;
+	if (tty->flags & TTY_KKBPUSHED)
+		return (-1);
 
 	/* First two bytes are always \033[. */
 	if (buf[0] != '\033')
@@ -1527,6 +1552,8 @@ tty_keys_device_attributes(struct tty *tty, const char *buf, size_t len,
 	}
 	log_debug("%s: received primary DA %.*s", c->name, (int)*size, buf);
 
+	/* A DA response without a preceding keyboard response means no support. */
+	tty->flags |= TTY_HAVEKKB;
 	tty_update_features(tty);
 	tty->flags |= TTY_HAVEDA;
 

tty-kitty.c

@@ -0,0 +1,440 @@
+/* $OpenBSD$ */
+
+/*
+ * Copyright (c) 2026 Michael Grant <mgrant@grant.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+
+#include <ctype.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "tmux.h"
+
+/* Detect support in the outside terminal and decode its key sequences. */
+
+struct tty_kitty_key {
+	u_int		 number;
+	key_code	 key;
+};
+
+static const struct tty_kitty_key tty_kitty_keys[] = {
+	{ 57358, KEYC_CAPSLOCK },
+	{ 57359, KEYC_SCROLLLOCK },
+	{ 57360, KEYC_NUMLOCK },
+	{ 57361, KEYC_PRINTSCREEN },
+	{ 57362, KEYC_PAUSE },
+	{ 57363, KEYC_MENU },
+	{ 57376, KEYC_F13 },
+	{ 57377, KEYC_F14 },
+	{ 57378, KEYC_F15 },
+	{ 57379, KEYC_F16 },
+	{ 57380, KEYC_F17 },
+	{ 57381, KEYC_F18 },
+	{ 57382, KEYC_F19 },
+	{ 57383, KEYC_F20 },
+	{ 57384, KEYC_F21 },
+	{ 57385, KEYC_F22 },
+	{ 57386, KEYC_F23 },
+	{ 57387, KEYC_F24 },
+	{ 57388, KEYC_F25 },
+	{ 57389, KEYC_F26 },
+	{ 57390, KEYC_F27 },
+	{ 57391, KEYC_F28 },
+	{ 57392, KEYC_F29 },
+	{ 57393, KEYC_F30 },
+	{ 57394, KEYC_F31 },
+	{ 57395, KEYC_F32 },
+	{ 57396, KEYC_F33 },
+	{ 57397, KEYC_F34 },
+	{ 57398, KEYC_F35 },
+	{ 57399, KEYC_KP_ZERO|KEYC_KEYPAD },
+	{ 57400, KEYC_KP_ONE|KEYC_KEYPAD },
+	{ 57401, KEYC_KP_TWO|KEYC_KEYPAD },
+	{ 57402, KEYC_KP_THREE|KEYC_KEYPAD },
+	{ 57403, KEYC_KP_FOUR|KEYC_KEYPAD },
+	{ 57404, KEYC_KP_FIVE|KEYC_KEYPAD },
+	{ 57405, KEYC_KP_SIX|KEYC_KEYPAD },
+	{ 57406, KEYC_KP_SEVEN|KEYC_KEYPAD },
+	{ 57407, KEYC_KP_EIGHT|KEYC_KEYPAD },
+	{ 57408, KEYC_KP_NINE|KEYC_KEYPAD },
+	{ 57409, KEYC_KP_PERIOD|KEYC_KEYPAD },
+	{ 57410, KEYC_KP_SLASH|KEYC_KEYPAD },
+	{ 57411, KEYC_KP_STAR|KEYC_KEYPAD },
+	{ 57412, KEYC_KP_MINUS|KEYC_KEYPAD },
+	{ 57413, KEYC_KP_PLUS|KEYC_KEYPAD },
+	{ 57414, KEYC_KP_ENTER|KEYC_KEYPAD },
+	{ 57415, KEYC_KP_EQUAL|KEYC_KEYPAD },
+	{ 57416, KEYC_KP_SEPARATOR|KEYC_KEYPAD },
+	{ 57417, KEYC_KP_LEFT|KEYC_KEYPAD },
+	{ 57418, KEYC_KP_RIGHT|KEYC_KEYPAD },
+	{ 57419, KEYC_KP_UP|KEYC_KEYPAD },
+	{ 57420, KEYC_KP_DOWN|KEYC_KEYPAD },
+	{ 57421, KEYC_KP_PPAGE|KEYC_KEYPAD },
+	{ 57422, KEYC_KP_NPAGE|KEYC_KEYPAD },
+	{ 57423, KEYC_KP_HOME|KEYC_KEYPAD },
+	{ 57424, KEYC_KP_END|KEYC_KEYPAD },
+	{ 57425, KEYC_KP_IC|KEYC_KEYPAD },
+	{ 57426, KEYC_KP_DC|KEYC_KEYPAD },
+	{ 57427, KEYC_KP_BEGIN|KEYC_KEYPAD },
+	{ 57428, KEYC_MEDIA_PLAY },
+	{ 57429, KEYC_MEDIA_PAUSE },
+	{ 57430, KEYC_MEDIA_PLAYPAUSE },
+	{ 57431, KEYC_MEDIA_REVERSE },
+	{ 57432, KEYC_MEDIA_STOP },
+	{ 57433, KEYC_MEDIA_FASTFORWARD },
+	{ 57434, KEYC_MEDIA_REWIND },
+	{ 57435, KEYC_MEDIA_NEXT },
+	{ 57436, KEYC_MEDIA_PREVIOUS },
+	{ 57437, KEYC_MEDIA_RECORD },
+	{ 57438, KEYC_VOLUME_DOWN },
+	{ 57439, KEYC_VOLUME_UP },
+	{ 57440, KEYC_VOLUME_MUTE },
+	{ 57441, KEYC_LEFT_SHIFT },
+	{ 57442, KEYC_LEFT_CTRL },
+	{ 57443, KEYC_LEFT_ALT },
+	{ 57444, KEYC_LEFT_SUPER },
+	{ 57445, KEYC_LEFT_HYPER },
+	{ 57446, KEYC_LEFT_META },
+	{ 57447, KEYC_RIGHT_SHIFT },
+	{ 57448, KEYC_RIGHT_CTRL },
+	{ 57449, KEYC_RIGHT_ALT },
+	{ 57450, KEYC_RIGHT_SUPER },
+	{ 57451, KEYC_RIGHT_HYPER },
+	{ 57452, KEYC_RIGHT_META },
+	{ 57453, KEYC_ISO_LEVEL3_SHIFT },
+	{ 57454, KEYC_ISO_LEVEL5_SHIFT }
+};
+
+static int
+tty_kitty_parse_number(const char *s, u_int *value, int empty)
+{
+	char		*end;
+	unsigned long	 number;
+
+	if (*s == '\0') {
+		if (!empty)
+			return (-1);
+		return (0);
+	}
+	if (!isdigit((u_char)*s))
+		return (-1);
+	number = strtoul(s, &end, 10);
+	if (*end != '\0' || number > UINT_MAX)
+		return (-1);
+	*value = number;
+	return (0);
+}
+
+static int
+tty_kitty_parse_list(char *s, u_int *first, u_int *second, int empty,
+    u_int maximum)
+{
+	char	*copy, *item;
+	u_int	 n = 0, value;
+	int	 result = 0;
+
+	copy = s;
+	while ((item = strsep(&copy, ":")) != NULL) {
+		if (maximum != 0 && n == maximum)
+			return (-1);
+		value = 0;
+		if (tty_kitty_parse_number(item, &value, empty) != 0) {
+			result = -1;
+			break;
+		}
+		if (n == 0 && *item != '\0')
+			*first = value;
+		else if (n == 1 && *item != '\0')
+			*second = value;
+		n++;
+	}
+	return (result);
+}
+
+static int
+tty_kitty_find_end(const char *buf, size_t len, size_t *end)
+{
+	size_t	i;
+
+	for (i = 2; i < len; i++) {
+		if (buf[i] == 'u' || buf[i] == '~' || buf[i] == 'A' ||
+		    buf[i] == 'B' || buf[i] == 'C' || buf[i] == 'D' ||
+		    buf[i] == 'E' || buf[i] == 'F' || buf[i] == 'H' ||
+		    buf[i] == 'P' || buf[i] == 'Q' || buf[i] == 'S') {
+			*end = i;
+			return (0);
+		}
+		if (!isdigit((u_char)buf[i]) && buf[i] != ';' && buf[i] != ':')
+			return (-1);
+	}
+	return (1);
+}
+
+static key_code
+tty_kitty_function(u_int number, char final)
+{
+	u_int	i;
+
+	if (final == 'u') {
+		switch (number) {
+		case 9:
+			return (C0_HT);
+		case 13:
+			return (C0_CR);
+		case 27:
+			return (C0_ESC);
+		case 127:
+			return (KEYC_BSPACE);
+		}
+		for (i = 0; i < nitems(tty_kitty_keys); i++) {
+			if (tty_kitty_keys[i].number == number)
+				return (tty_kitty_keys[i].key);
+		}
+		return (KEYC_NONE);
+	}
+
+	if (final == '~') {
+		switch (number) {
+		case 2: return (KEYC_IC);
+		case 3: return (KEYC_DC);
+		case 5: return (KEYC_PPAGE);
+		case 6: return (KEYC_NPAGE);
+		case 7: return (KEYC_HOME);
+		case 8: return (KEYC_END);
+		case 11: return (KEYC_F1);
+		case 12: return (KEYC_F2);
+		case 13: return (KEYC_F3);
+		case 14: return (KEYC_F4);
+		case 15: return (KEYC_F5);
+		case 17: return (KEYC_F6);
+		case 18: return (KEYC_F7);
+		case 19: return (KEYC_F8);
+		case 20: return (KEYC_F9);
+		case 21: return (KEYC_F10);
+		case 23: return (KEYC_F11);
+		case 24: return (KEYC_F12);
+		case 29: return (KEYC_MENU);
+		case 57427: return (KEYC_KP_BEGIN|KEYC_KEYPAD);
+		}
+		return (KEYC_UNKNOWN);
+	}
+	if (number != 1)
+		return (KEYC_UNKNOWN);
+	switch (final) {
+	case 'A': return (KEYC_UP|KEYC_CURSOR);
+	case 'B': return (KEYC_DOWN|KEYC_CURSOR);
+	case 'C': return (KEYC_RIGHT|KEYC_CURSOR);
+	case 'D': return (KEYC_LEFT|KEYC_CURSOR);
+	case 'E': return (KEYC_KP_BEGIN|KEYC_KEYPAD);
+	case 'F': return (KEYC_END);
+	case 'H': return (KEYC_HOME);
+	case 'P': return (KEYC_F1);
+	case 'Q': return (KEYC_F2);
+	case 'S': return (KEYC_F4);
+	}
+	return (KEYC_UNKNOWN);
+}
+
+int
+tty_keys_kitty_query(struct tty *tty, const char *buf, size_t len,
+    size_t *size)
+{
+	struct client	*c = tty->client;
+	size_t		 i;
+	u_int		 flags = 0;
+
+	*size = 0;
+	if (tty->flags & TTY_HAVEKKB)
+		return (-1);
+	if (options_get_number(global_options, "extended-keys") == 0 ||
+	    options_get_number(global_options, "extended-keys-format") !=
+	    EXTENDED_KEYS_KITTY)
+		return (-1);
+
+	if (buf[0] != '\033')
+		return (-1);
+	if (len == 1)
+		return (1);
+	if (buf[1] != '[')
+		return (-1);
+	if (len == 2)
+		return (1);
+	if (buf[2] != '?')
+		return (-1);
+	if (len == 3)
+		return (1);
+
+	for (i = 3; i < len && isdigit((u_char)buf[i]); i++) {
+		if (flags > (UINT_MAX - (buf[i] - '0')) / 10)
+			return (-1);
+		flags = (flags * 10) + (buf[i] - '0');
+	}
+	if (i == len)
+		return (1);
+	if (i == 3 || buf[i] != 'u')
+		return (-1);
+
+	*size = i + 1;
+	tty->kitty_keys = flags;
+	tty->flags |= (TTY_HAVEKKB|TTY_KKBSUPPORT);
+	log_debug("%s: received Kitty keyboard flags %u", c->name, flags);
+	tty_update_features(tty);
+	return (0);
+}
+
+void
+tty_update_kitty(struct tty *tty, struct screen *s)
+{
+	u_int	flags;
+	char	buf[32];
+
+	if (options_get_number(global_options, "extended-keys") == 0 ||
+	    options_get_number(global_options, "extended-keys-format") !=
+	    EXTENDED_KEYS_KITTY) {
+		if (tty->flags & TTY_KKBPUSHED) {
+			tty_puts(tty, "\033[<u");
+			tty->flags &= ~TTY_KKBPUSHED;
+		}
+		return;
+	}
+	if ((tty->flags & (TTY_HAVEKKB|TTY_KKBSUPPORT)) !=
+	    (TTY_HAVEKKB|TTY_KKBSUPPORT))
+		return;
+
+	flags = KITTY_KEY_DISAMBIGUATE;
+	if (s != NULL && (s->kitty_keys.flags & KITTY_KEY_SUPPORTED) != 0)
+		flags = s->kitty_keys.flags & KITTY_KEY_SUPPORTED;
+	if ((tty->flags & TTY_KKBPUSHED) == 0) {
+		xsnprintf(buf, sizeof buf, "\033[>%uu", flags);
+		tty_puts(tty, buf);
+		tty->flags |= TTY_KKBPUSHED;
+	} else if (tty->kitty_keys != flags) {
+		xsnprintf(buf, sizeof buf, "\033[=%uu", flags);
+		tty_puts(tty, buf);
+	}
+	tty->kitty_keys = flags;
+}
+
+int
+tty_keys_kitty(struct tty *tty, const char *buf, size_t len, size_t *size,
+    key_code *key)
+{
+	struct client	*c = tty->client;
+	struct utf8_data ud;
+	utf8_char	 uc;
+	size_t		 end;
+	char		 tmp[128], *copy, *field, final;
+	u_int		 number = 0, modifiers = 1, event = 1, value;
+	u_int		 fields = 0;
+	key_code	 nkey, onlykey;
+	int		 result;
+
+	*size = 0;
+	if ((tty->flags & TTY_KKBPUSHED) == 0 ||
+	    options_get_number(global_options, "extended-keys-format") !=
+	    EXTENDED_KEYS_KITTY)
+		return (-1);
+	if (len == 0 || buf[0] != '\033')
+		return (-1);
+	if (len == 1)
+		return (1);
+	if (buf[1] != '[')
+		return (-1);
+	if (len == 2)
+		return (1);
+	if (buf[2] == '?')
+		return (-1);
+
+	result = tty_kitty_find_end(buf, len, &end);
+	if (result != 0)
+		return (result);
+	if (end - 2 >= sizeof tmp)
+		return (-1);
+	memcpy(tmp, buf + 2, end - 2);
+	tmp[end - 2] = '\0';
+	final = buf[end];
+	*size = end + 1;
+
+	copy = tmp;
+	while ((field = strsep(&copy, ";")) != NULL) {
+		if (fields == 3)
+			return (-1);
+		value = 0;
+		if (fields == 0) {
+			if (*field == '\0') {
+				if (final == 'u')
+					return (-1);
+				number = 1;
+			} else if (tty_kitty_parse_list(field, &number, &value,
+			    1, 3) != 0)
+				return (-1);
+		} else if (fields == 1) {
+			if (tty_kitty_parse_list(field, &modifiers, &event, 1,
+			    2) != 0)
+				return (-1);
+		} else if (tty_kitty_parse_list(field, &value, &value, 1, 0) != 0)
+			return (-1);
+		fields++;
+	}
+	if (fields == 0 || number == 0 || modifiers == 0)
+		return (-1);
+	if (event == 0 || event == 3 || event > 3)
+		return (-2);
+
+	modifiers--;
+	if (modifiers & 32)
+		return (-2);
+	nkey = tty_kitty_function(number, final);
+	if (nkey == KEYC_NONE) {
+		if (final != 'u')
+			return (-1);
+		if (number >= 57344 && number <= 63743)
+			return (-2);
+		if (number <= 0x7f)
+			nkey = number;
+		else if (utf8_fromwc(number, &ud) != UTF8_DONE ||
+		    utf8_from_data(&ud, &uc) != UTF8_DONE)
+			return (-2);
+		else
+			nkey = uc;
+	} else if (nkey == KEYC_UNKNOWN)
+		return (-1);
+
+	if (modifiers & 1)
+		nkey |= KEYC_SHIFT;
+	if (modifiers & 2)
+		nkey |= KEYC_META|KEYC_IMPLIED_META;
+	if (modifiers & 4)
+		nkey |= KEYC_CTRL;
+	if (modifiers & 8)
+		nkey |= KEYC_SUPER;
+	if (modifiers & 16)
+		nkey |= KEYC_HYPER;
+
+	/* Shift-Tab has a dedicated tmux key code. */
+	onlykey = nkey & KEYC_MASK_KEY;
+	if (onlykey == C0_HT && (nkey & KEYC_SHIFT))
+		nkey = KEYC_BTAB|(nkey & ~KEYC_MASK_KEY & ~KEYC_SHIFT);
+
+	if (log_get_level() != 0) {
+		log_debug("%s: Kitty key %.*s is %llx (%s)", c->name,
+		    (int)*size, buf, nkey, key_string_lookup_key(nkey, 1));
+	}
+	*key = nkey;
+	return (0);
+}

tty.c

@@ -409,6 +409,11 @@ tty_send_requests(struct tty *tty)
 		return;
 
 	if (tty->term->flags & TERM_VT100LIKE) {
+		if (~tty->flags & TTY_HAVEKKB &&
+		    options_get_number(global_options, "extended-keys") != 0 &&
+		    options_get_number(global_options, "extended-keys-format") ==
+		    EXTENDED_KEYS_KITTY)
+			tty_puts(tty, "\033[?u");
 		if (~tty->flags & TTY_HAVEDA)
 			tty_puts(tty, "\033[c");
 		if (~tty->flags & TTY_HAVEDA2)
@@ -507,6 +512,10 @@ tty_stop_tty(struct tty *tty)
 		tty_raw(tty, "\033[?7727l");
 	tty_raw(tty, tty_term_string(tty->term, TTYC_DSFCS));
 	tty_raw(tty, tty_term_string(tty->term, TTYC_DSEKS));
+	if (tty->flags & TTY_KKBPUSHED) {
+		tty_raw(tty, "\033[<u");
+		tty->flags &= ~TTY_KKBPUSHED;
+	}
 
 	if (tty_use_margin(tty))
 		tty_raw(tty, tty_term_string(tty->term, TTYC_DSMG));
@@ -553,14 +562,23 @@ 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"))
+	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
 		tty_puts(tty, tty_term_string(tty->term, TTYC_ENEKS));
+	tty_update_kitty(tty, NULL);
 	if (options_get_number(global_options, "focus-events"))
 		tty_puts(tty, tty_term_string(tty->term, TTYC_ENFCS));
 	if (tty->term->flags & TERM_VT100LIKE)

window.c

@@ -1980,7 +1980,8 @@ window_pane_copy_paste(struct window_pane *wp, char *buf, size_t len)
 }
 
 static void
-window_pane_copy_key(struct window_pane *wp, key_code key)
+window_pane_copy_key(struct window_pane *wp, key_code key,
+    int extended_encoding)
 {
 	struct window_pane	*loop;
 
@@ -1991,7 +1992,7 @@ window_pane_copy_key(struct window_pane *wp, key_code key)
 		    (~loop->flags & PANE_INPUTOFF) &&
 		    window_pane_is_visible(loop) &&
 		    options_get_number(loop->options, "synchronize-panes"))
-			input_key_pane(loop, key, NULL);
+			input_key_pane(loop, key, NULL, extended_encoding);
 	}
 }
 
@@ -2019,6 +2020,7 @@ window_pane_key(struct window_pane *wp, struct client *c, struct session *s,
     struct winlink *wl, key_code key, struct mouse_event *m)
 {
 	struct window_mode_entry	*wme;
+	int				 extended_encoding;
 
 	if (KEYC_IS_MOUSE(key) && m == NULL)
 		return (-1);
@@ -2041,13 +2043,14 @@ window_pane_key(struct window_pane *wp, struct client *c, struct session *s,
 	if (wp->fd == -1 || wp->flags & PANE_INPUTOFF)
 		return (0);
 
-	if (input_key_pane(wp, key, m) != 0)
+	extended_encoding = input_key_client_supports_extended(c, key);
+	if (input_key_pane(wp, key, m, extended_encoding) != 0)
 		return (-1);
 
 	if (KEYC_IS_MOUSE(key))
 		return (0);
 	if (options_get_number(wp->options, "synchronize-panes"))
-		window_pane_copy_key(wp, key);
+		window_pane_copy_key(wp, key, extended_encoding);
 	return (0);
 }