The kitty remote control protocol#

The kitty remote control protocol is a simple protocol that involves sending data to kitty in the form of JSON. Any individual command of kitty has the form:

<ESC>P@kitty-cmd<JSON object><ESC>\

Where <ESC> is the byte 0x1b. The JSON object has the form:

{
    "cmd": "command name",
    "version": "<kitty version>",
    "no_response": "<Optional Boolean>",
    "payload": "<Optional JSON object>"
}

The version above is an array of the form [0, 14, 2]. If you are developing a standalone client, use the kitty version that you are developing against. Using a version greater than the version of the kitty instance you are talking to, will cause a failure.

Set no_response to true if you don’t want a response from kitty.

The optional payload is a JSON object that is specific to the actual command being sent. The fields in the object for every command are documented below.

As a quick example showing how easy to use this protocol is, we will implement the @ ls command from the shell using only shell tools.

First, run kitty as:

kitty -o allow_remote_control=socket-only --listen-on unix:/tmp/test

Now, in a different terminal, you can get the pretty printed @ ls output with the following command line:

echo -en '\eP@kitty-cmd{"cmd":"ls","version":[0,14,2]}\e\\' | socat - unix:/tmp/test | awk '{ print substr($0, 13, length($0) - 14) }' | jq -c '.data | fromjson' | jq .

Encrypted communication#

New in version 0.26.0.

When using the remote_control_password option communication to the terminal is encrypted to keep the password secure. A public key is used from the KITTY_PUBLIC_KEY environment variable. Currently, only one encryption protocol is supported. The protocol number is present in KITTY_PUBLIC_KEY as 1. The key data in this environment variable is Base-85 encoded. The algorithm used is Elliptic Curve Diffie Helman with the X25519 curve. A time based nonce is used to minimise replay attacks. The original JSON command has the fields: password and timestamp added. The timestamp is the number of nanoseconds since the epoch, excluding leap seconds. Commands with a timestamp more than 5 minutes from the current time are rejected. The command is then encrypted using AES-256-GCM in authenticated encryption mode, with a symmetric key that is derived from the ECDH key-pair by running the shared secret through SHA-256 hashing, once. An IV of at least 96 bits of CSPRNG data is used. The tag for authenticated encryption must be at least 128 bits long. The tag must authenticate only the value of the encrypted field. A new command is created and transmitted that contains the fields:

{
    "version": "<kitty version>",
    "iv": "base85 encoded IV",
    "tag": "base85 encoded AEAD tag",
    "pubkey": "base85 encoded ECDH public key of sender",
    "encrypted": "The original command encrypted and base85 encoded"
}

close-tab#

Fields are:

match (default: None): Which tab to close
no_response (default: False): Boolean indicating whether to wait for a response
self (default: False): Boolean indicating whether to close the tab of the window the command is run in
ignore_no_match (default: False): Boolean indicating whether no matches should be ignored or return an error

close-window#

Fields are:

match (default: None): Which window to close
no_response (default: False): Boolean indicating whether to wait for a response
self (default: False): Boolean indicating whether to close the window the command is run in
ignore_no_match (default: False): Boolean indicating whether no matches should be ignored or return an error

create-marker#

Fields are:

match (default: None): Which window to create the marker in
self (default: False): Boolean indicating whether to create marker in the window the command is run in
marker_spec (optional): A list or arguments that define the marker specification, for example: [‘text’, ‘1’, ‘ERROR’]

detach-tab#

Fields are:

match (default: None): Which tab to detach
target_tab (default: None): Which tab to move the detached tab to the OS window it is run in
self (default: False): Boolean indicating whether to detach the tab the command is run in

detach-window#

Fields are:

match (default: None): Which window to detach
target_tab (default: None): Which tab to move the detached window to
self (default: False): Boolean indicating whether to detach the window the command is run in

disable-ligatures#

Fields are:

strategy (required): One of never, always or cursor
match_window (optional): Window to change opacity in
match_tab (default: None): Tab to change opacity in
all (default: False): Boolean indicating operate on all windows

env#

Fields are:

env (required): Dictionary of environment variables to values. Empty values cause the variable to be removed.

focus-tab#

Fields are:

match (default: None): The tab to focus
no_response (default: False): Boolean indicating whether to wait for a response

focus-window#

Fields are:

match (default: None): The window to focus
no_response (default: False): Boolean indicating whether to wait for a response

get-colors#

Fields are:

match (default: None): The window to get the colors for
configured (default: False): Boolean indicating whether to get configured or current colors

get-text#

Fields are:

match (default: None): The window to get text from
extent (default: screen): One of screen, first_cmd_output_on_screen, last_cmd_output, last_visited_cmd_output, all, or selection
ansi (default: False): Boolean, if True send ANSI formatting codes
cursor (optional): Boolean, if True send cursor position/style as ANSI codes
wrap_markers (optional): Boolean, if True add wrap markers to output
clear_selection (default: None): Boolean, if True clear the selection in the matched window
self (default: False): Boolean, if True use window the command was run in

goto-layout#

Fields are:

layout (required): The new layout name
match (default: None): Which tab to change the layout of

kitten#

Fields are:

kitten (required): The name of the kitten to run
args (optional): Arguments to pass to the kitten as a list
match (default: None): The window to run the kitten over

last-used-layout#

Fields are:

match (default: None): Which tab to change the layout of
all (default: False): Boolean to match all tabs
no_response (default: False): Boolean indicating whether to wait for a response

launch#

Fields are:

args (required): The command line to run in the new window, as a list, use an empty list to run the default shell
match (default: None): The tab to open the new window in
window_title (default: None): Title for the new window
cwd (default: None): Working directory for the new window
env (default: []): List of environment variables of the form NAME=VALUE
tab_title (default: None): Title for the new tab
type (default: window): The type of window to open
keep_focus (default: False): Boolean indicating whether the current window should retain focus or not
copy_colors (default: False): Boolean indicating whether to copy the colors from the current window
copy_cmdline (default: False): Boolean indicating whether to copy the cmdline from the current window
copy_env (default: False): Boolean indicating whether to copy the environ from the current window
hold (default: False): Boolean indicating whether to keep window open after cmd exits
location (default: default): Where in the tab to open the new window
allow_remote_control (default: False): Boolean indicating whether to allow remote control from the new window
remote_control_password (default: []): A list of remote control passwords
stdin_source (default: none): Where to get stdin for the process from
stdin_add_formatting (default: False): Boolean indicating whether to add formatting codes to stdin
stdin_add_line_wrap_markers (default: False): Boolean indicating whether to add line wrap markers to stdin
spacing (default: []): A list of spacing specifications, see the docs for the set-spacing command
no_response (default: False): Boolean indicating whether to send back the window id
marker (default: None): Specification for marker for new window, for example: “text 1 ERROR”
logo (default: None): Path to window logo
logo_position (default: None): Window logo position as string or empty string to use default
logo_alpha (default: -1.0): Window logo alpha or -1 to use default
self (default: False): Boolean, if True use tab the command was run in

ls#

Fields are:

all_env_vars (default: False): Whether to send all environment variables for every window rather than just differing ones

new-window#

Fields are:

args (required): The command line to run in the new window, as a list, use an empty list to run the default shell
match (default: None): The tab to open the new window in
title (default: None): Title for the new window
cwd (default: None): Working directory for the new window
keep_focus (default: False): Boolean indicating whether the current window should retain focus or not
window_type (default: kitty): One of kitty or os
new_tab (default: False): Boolean indicating whether to open a new tab
tab_title (default: None): Title for the new tab
no_response (default: False): Boolean indicating whether to send back the window id

remove-marker#

Fields are:

match (default: None): Which window to remove the marker from
self (default: False): Boolean indicating whether to detach the window the command is run in

resize-os-window#

Fields are:

match (default: None): Which window to resize
self (default: False): Boolean indicating whether to close the window the command is run in
incremental (default: False): Boolean indicating whether to adjust the size incrementally
action (default: resize): One of resize, toggle-fullscreen or toggle-maximized
unit (default: cells): One of cells or pixels
width (default: 0): Integer indicating desired window width
height (default: 0): Integer indicating desired window height

resize-window#

Fields are:

match (default: None): Which window to resize
self (default: False): Boolean indicating whether to resize the window the command is run in
increment (default: 2): Integer specifying the resize increment
axis (default: horizontal): One of horizontal, vertical or reset

scroll-window#

for unscrolling by lines.

Fields are:

amount (required): The amount to scroll, a two item list with the first item being either a number or the keywords, start and end. And the second item being either ‘p’ for pages or ‘l’ for lines or ‘u’
match (default: None): The window to scroll
no_response (default: False): Boolean indicating whether to wait for a response

select-window#

Fields are:

match (default: None): The tab to open the new window in
self (default: False): Boolean, if True use tab the command was run in
title (default: None): A title for this selection
exclude_active (default: False): Exclude the currently active window from the list to pick
reactivate_prev_tab (default: False): Reactivate the previously activated tab when finished

send-text#

Fields are:

data (required): The data being sent. Can be either: text: followed by text or base64: followed by standard base64 encoded bytes
match (default: None): A string indicating the window to send text to
match_tab (default: None): A string indicating the tab to send text to
all (default: False): A boolean indicating all windows should be matched.
exclude_active (default: False): A boolean that prevents sending text to the active window
session_id (optional): A string that identifies a “broadcast session”

set-background-opacity#

Fields are:

opacity (required): A number between 0.1 and 1
match_window (optional): Window to change opacity in
match_tab (default: None): Tab to change opacity in
all (default: False): Boolean indicating operate on all windows

set-colors#

Fields are:

colors (required): An object mapping names to colors as 24-bit RGB integers or null for nullable colors
match_window (optional): Window to change colors in
match_tab (default: None): Tab to change colors in
all (default: False): Boolean indicating change colors everywhere or not
configured (default: False): Boolean indicating whether to change the configured colors. Must be True if reset is True
reset (default: False): Boolean indicating colors should be reset to startup values

set-enabled-layouts#

Fields are:

layouts (required): The list of layout names
match (default: None): Which tab to change the layout of
configured (default: False): Boolean indicating whether to change the configured value

set-font-size#

Fields are:

size (required): The new font size in pts (a positive number)
all (default: False): Boolean whether to change font size in the current window or all windows
increment_op (optional): The string + or - to interpret size as an increment

set-spacing#

Fields are:

settings (required): An object mapping margins/paddings using canonical form {‘margin-top’: 50, ‘padding-left’: null} etc
match_window (optional): Window to change paddings and margins in
match_tab (default: None): Tab to change paddings and margins in
all (default: False): Boolean indicating change paddings and margins everywhere or not
configured (default: False): Boolean indicating whether to change the configured paddings and margins. Must be True if reset is True

set-tab-color#

Fields are:

colors (required): An object mapping names to colors as 24-bit RGB integers. A color value of null indicates it should be unset.
match (default: None): Which tab to change the color of
self (default: False): Boolean indicating whether to use the tab of the window the command is run in

set-tab-title#

Fields are:

title (required): The new title
match (default: None): Which tab to change the title of

set-window-logo#

Fields are:

data (required): Chunk of at most 512 bytes of PNG data, base64 encoded. Must send an empty chunk to indicate end of image. Or the special value - to indicate image must be removed.
position (default: None): The logo position as a string, empty string means default
alpha (default: -1.0): The logo alpha between 0 and 1. -1 means use default
match (default: None): Which window to change the logo in
self (default: False): Boolean indicating whether to act on the window the command is run in

set-window-title#

Fields are:

title (optional): The new title
match (default: None): Which windows to change the title in
temporary (default: False): Boolean indicating if the change is temporary or permanent

signal-child#

Fields are:

signals (optional): The signals, a list of names, such as SIGTERM, SIGKILL, SIGUSR1, etc.
match (default: None): Which windows to send the signals to
no_response (default: False): Boolean indicating whether to wait for a response