OSC 133

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Experimental

OSC 133 marks semantic zones in the terminal output, enabling the terminal to distinguish between prompts, user input, and command output. Originally designed for the FinalTerm terminal emulator, this protocol has been adopted by VS Code's integrated terminal, kitty, WezTerm, and iTerm2.

Syntax

OSC 133 ; A ST              Prompt start
OSC 133 ; B ST              Command start (end of prompt / input begins)
OSC 133 ; C ST              Output start (command is executing)
OSC 133 ; D ; exitcode ST   Command finished with exit code
OSC 133 ; D ST              Command finished (no exit code)

Formal syntax

OSC133-A  = 0x1b, "]", "133", ";", "A", ( 0x07 | 0x1b, "\\" ) ;
OSC133-B  = 0x1b, "]", "133", ";", "B", ( 0x07 | 0x1b, "\\" ) ;
OSC133-C  = 0x1b, "]", "133", ";", "C", ( 0x07 | 0x1b, "\\" ) ;
OSC133-D  = 0x1b, "]", "133", ";", "D", [ ";", exitcode ], ( 0x07 | 0x1b, "\\" ) ;
exitcode  = [ "-" ], digit, { digit } ;
digit     = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;

Parameters

The four zone markers define the boundaries of a command lifecycle:

Marker	Name	Description
`A`	Prompt start	Marks the beginning of the shell prompt.
`B`	Command start	Marks the end of the prompt and beginning of user input. Also sent when the user presses Enter (the command line is finalized).
`C`	Output start	Marks the end of user input and beginning of command output.
`D`	Command end	Marks the end of command output. Optionally followed by `;exitcode` to report the command's exit status.

Description

Shell integration via OSC 133 allows the terminal to understand the structure of an interactive shell session. A typical command cycle looks like:

A -- Shell prints the prompt
(prompt text appears)
B -- User has typed a command and pressed Enter
C -- Command begins executing, output follows
(command output appears)
D;0 -- Command finished with exit code 0

With this information, the terminal can provide features such as:

Command navigation -- Jump between prompts using keyboard shortcuts
Output selection -- Select the output of a specific command
Exit code decoration -- Show success/failure indicators on the prompt
Scrollback marks -- Mark each command in the scrollback for quick access
Command-aware copy -- Copy only a command's output, excluding the prompt

Shell configuration

Shell integration requires the shell to emit these markers. Most implementations inject the markers through shell hooks:

Bash: Uses PS0, PS1, and PROMPT_COMMAND to emit markers at the appropriate points
Zsh: Uses precmd and preexec hooks
Fish: Uses fish_prompt and fish_preexec/fish_postexec events

VS Code, kitty, WezTerm, and iTerm2 each provide their own shell integration scripts that set up these hooks automatically.

Additional parameters

Some implementations extend the A marker with key-value parameters. For example, VS Code uses OSC 133 ; A ; cl=m ST to indicate a multi-line prompt. These extensions are terminal-specific and not part of the original FinalTerm specification.

Examples

# Minimal bash integration using PROMPT_COMMAND and PS0
__prompt_command() {
    local exit_code=$?
    # Mark end of previous command
    PS1='\[\e]133;D;'$exit_code'\a\]'
    # Mark prompt start
    PS1+='\[\e]133;A\a\]'
    # Actual prompt content
    PS1+='\u@\h:\w\$ '
    # Mark command start (after prompt)
    PS1+='\[\e]133;B\a\]'
}
PROMPT_COMMAND=__prompt_command
# PS0 marks output start when a command is executed
PS0='\e]133;C\a'

Specifications

Specification	Section
VS Code Shell Integration	—

Terminal support

Terminal	Support	Version	Notes
Terminal Emulators
Alacritty	✗	No
Bobcat	?	?	Would be handled by underlying TerminalCtrl library, not directly in Bobcat code
contour	✓	v0.1.0	OSC 133 shell integration (SEMA) is implemented in Functions.h line 648, handled via processShellIntegration() in Screen.cpp line 4057, supporting prompt markers (A, B, C, D)
foot	✓	Yes	FinalTerm semantic zones (FTCS_PROMPT, FTCS_COMMAND_START, FTCS_COMMAND_EXECUTED, FTCS_COMMAND_FINISHED)
Ghostty	✓	v1.0.0	Shell integration semantic prompts
iTerm2	✓	Yes	FinalTerm shell integration via XTERMCC_FINAL_TERM token
Kitty	✓	0.24.0	Part of shell integration feature
Konsole	✓	Yes	Fully supports FinalTerm semantic prompts with REPL mode tracking for prompt (A/N/P), input (B), output (C), and completion (D)
mintty	✗	No	No implementation found for OSC 133 shell integration
mlterm	✗	No
PuTTY	✗	No
Rio	✗	No	Shell integration markers are documented as not implemented (commented out in docs)
rxvt-unicode	✗	No
st	✗	No
terminology	✗	No
VT100	✗	No
VTE	✓	Yes	Full iTerm2 shell integration support (A/B/C/D/L modes)
WezTerm	✓	20210203-095643-70a364eb	FinalTerm semantic zones for shell integration
Windows Terminal	✓	Yes	Supports FinalTerm sequences A, B, C, D for shell integration
xterm	✗	No	Shell integration (FinalTerm semantic zones) not implemented
xterm.js	✗	No
Multiplexers
cy	✓	v1.10.0
GNU Screen	✗	No
tmux	✓	3.4
tuios	✗	No
Zellij	✗	No	No OSC 133 shell integration support found

Syntax​

Parameters​

Description​

Shell configuration​

Additional parameters​

Examples​

Specifications​

Terminal support​

See also​