OSC Sequences

cmuxterm supports two OSC (Operating System Command) escape sequence standards for sending notifications from terminal programs.

OSC 99 (Kitty Protocol)

The Kitty notification protocol provides rich notification support with multiple parameters.

Format

ESC ] 99 ; <params> ; <payload> ESC \

Or using BEL terminator:

ESC ] 99 ; <params> ; <payload> BEL

Parameters

Parameters are semicolon-separated key=value pairs:

Parameter	Description	Values
`i`	Notification ID	Any string
`e`	Event type	`1` = new notification
`d`	Done flag	`0` = more data coming, `1` = complete
`p`	Payload type	`title`, `body`, `subtitle`

Payload

After the final semicolon, the payload contains the notification content. If p= is specified, the payload is interpreted as that type.

Examples

Simple notification:

printf '\e]99;i=1;e=1;d=0:Hello World\e\\'

Notification with title and body:

# Set title
printf '\e]99;i=1;e=1;d=0;p=title:Build Complete\e\\'
# Set body
printf '\e]99;i=1;e=1;d=1;p=body:All tests passed\e\\'

With subtitle:

printf '\e]99;i=1;e=1;d=0;p=title:Claude Code\e\\'
printf '\e]99;i=1;e=1;d=0;p=subtitle:Session abc123\e\\'
printf '\e]99;i=1;e=1;d=1;p=body:Waiting for input\e\\'

Shell Function

notify_osc99() {
    local title="$1"
    local body="$2"
    local id="${3:-1}"
 
    printf '\e]99;i=%s;e=1;d=0;p=title:%s\e\\' "$id" "$title"
    printf '\e]99;i=%s;e=1;d=1;p=body:%s\e\\' "$id" "$body"
}
 
# Usage
notify_osc99 "Build Done" "Your project compiled successfully"

OSC 777 (RXVT Protocol)

The RXVT/urxvt protocol is simpler, with a fixed format for title and body.

Format

ESC ] 777 ; notify ; <title> ; <body> BEL

Or with ST terminator:

ESC ] 777 ; notify ; <title> ; <body> ESC \

Examples

Basic notification:

printf '\e]777;notify;Hello;World\a'

Build completion:

printf '\e]777;notify;Build Complete;All 42 tests passed\a'

With ST terminator:

printf '\e]777;notify;Task Done;Ready for review\e\\'

Shell Function

notify_osc777() {
    local title="$1"
    local body="$2"
    printf '\e]777;notify;%s;%s\a' "$title" "$body"
}
 
# Usage
notify_osc777 "Download Complete" "File saved to ~/Downloads"

Comparison

Feature	OSC 99	OSC 777
Title	✓	✓
Body	✓	✓
Subtitle	✓	✗
Notification ID	✓	✗
Complexity	Higher	Lower
Compatibility	Kitty, cmuxterm	RXVT, cmuxterm

Recommendations

Use OSC 777 for simple title + body notifications
Use OSC 99 when you need subtitles or notification IDs
Use the CLI (cmuxterm notify) for the easiest integration

Testing

Test notifications in your terminal:

# OSC 777 (simpler)
printf '\e]777;notify;Test;This is a test notification\a'
 
# OSC 99 (with subtitle)
printf '\e]99;i=test;e=1;d=0;p=title:Test Notification\e\\'
printf '\e]99;i=test;e=1;d=0;p=subtitle:Subtitle here\e\\'
printf '\e]99;i=test;e=1;d=1;p=body:This is the body text\e\\'

Integration with Other Tools

tmux

If using tmux inside cmuxterm, enable passthrough:

# In .tmux.conf
set -g allow-passthrough on

Then wrap sequences:

printf '\ePtmux;\e\e]777;notify;Title;Body\a\e\\'

SSH

Notifications work over SSH if your SSH client supports OSC passthrough. Most modern terminals do.

Python

import sys
 
def notify(title: str, body: str):
    """Send OSC 777 notification."""
    sys.stdout.write(f'\x1b]777;notify;{title};{body}\x07')
    sys.stdout.flush()
 
notify("Script Complete", "Processing finished")

Node.js

function notify(title, body) {
  process.stdout.write(`\x1b]777;notify;${title};${body}\x07`);
}
 
notify('Build Done', 'webpack finished');

OSC Sequences

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