prompt color bleeding when ghostty(with zsh) window is resized

[recluse-be-responsible]

Issue Description

I am using zsh shell with starship for designing my prompt. When the terminal(ghostty) window is resized in a way that makes the prompt longer than the window width, i.e., the prompt takes two lines to appear, some color bleeds as shown in the attached image. This doesn't necessarily happen on resizing but it also happens inside an already resized window when a new prompt is summoned. This doesn't happen with: zsh+kitty(or any shell in kitty), nushell+ghostty. It also happens with zsh+wezterm, it doesn't happen with any terminal emulator(ghostty, kitty or wezterm) when the shell is nushell.

Expected Behavior

The color should not bleed on the remaining space on the second prompt line like with kitty:

Actual Behavior

The color bleeds on the empty space on the second line of the prompt

Reproduction Steps

1. Use my Starship.toml prompt, here is a link to it: https://gitlab.com/recluse0/dotfiles/-/blob/master/modules/home-manager/starship/starship.toml
2. Initialize your zsh shell with the starship prompt by adding eval "$(starship init zsh)" at the end of you .zshrc file
3. Open a ghostty window with zsh shell and resize your window so that the prompt length is longer than the window width hence making the prompt take two lines to render
4. Run STARSHIP_LOG=trace starship prompt command

Ghostty Logs

info: ghostty version=1.2.0
info: ghostty build optimize=ReleaseFast
info: runtime=apprt.Runtime.gtk
info: font_backend=font.main.Backend.fontconfig_freetype
info: dependency harfbuzz=11.2.1
info: dependency fontconfig=21602
info: renderer=renderer.generic.Renderer(renderer.OpenGL)
info: libxev default backend=io_uring
info(os_locale): setlocale from env result=en_IN
info(gtk): GTK version build=4.18.6 runtime=4.18.6
info(gtk): libadwaita version build=1.7.6 runtime=1.7.6
info: reading configuration file path=/home/recluse/.config/ghostty/config
info(config): shell src=config value=config.command.Command{ .shell = { 47, 110, 105, 120, 47, 115, 116, 111, 114, 101, 47, 100, 107, 56, 52, 99, 57, 51, 97, 110, 110, 98, 98, 121, 114, 99, 108, 104, 121, 54, 57, 49, 97, 106, 99, 121, 121, 100, 121, 99, 119, 51, 53, 45, 122, 115, 104, 45, 53, 46, 57, 47, 98, 105, 110, 47, 122, 115, 104 } }
info(config): default working directory src=passwd value=/home/recluse
warning(gtk_ghostty_application): setting GDK_DEBUG=
warning(gtk_ghostty_application): setting GDK_DISABLE=gles-api,vulkan
info(gtk_systemd_cgroup): transient scope created cgroup=/user.slice/user-1000.slice/[email protected]/app.slice/app-ghostty-transient-44713.scope
info(gtk_ghostty_application): cgroup isolation enabled base=/user.slice/user-1000.slice/[email protected]/app.slice/app-ghostty-transient-44713.scope
info(opengl): loaded OpenGL 4.6
info(font_shared_grid_set): font regular: JetBrainsMono NF Regular
info(font_shared_grid_set): font bold: JetBrainsMono NF Bold
info(font_shared_grid_set): font italic: JetBrainsMono NF Italic
info(font_shared_grid_set): font bold_italic: JetBrainsMono NF Bold Italic
info(io_exec): found Ghostty resources dir: /nix/store/sq2miwkzr12xns1ik72h6c16s6wkivh9-ghostty-1.2.0/share/ghostty
info(io_exec): shell integration automatically injected shell=termio.shell_integration.Shell.zsh
warning(gtk_ghostty_application): unimplemented action=apprt.action.Action.Key.cell_size
info(io_exec): started subcommand path=/bin/sh pid=44755
info(io_exec): subcommand cgroup=/user.slice/user-1000.slice/[email protected]/app.slice/app-ghostty-transient-44713.scope/surfaces/556DB1117510.scope
info(osc): unknown semantic prompts option: cl
warning(io_handler): OSC 7 uri must contain a hostname: error.NoHostnameInUri
warning(osc): invalid OSC command: 133;P;k=i
info(osc): unknown semantic prompts option: cmdline
info(io_exec): pty fd closed, read thread exiting
info(surface): surface closed addr=556db17cfcd0

Ghostty Version

Ghostty 1.2.0

Version
  - version: 1.2.0
  - channel: stable
Build Config
  - Zig version   : 0.14.1
  - build mode    : builtin.OptimizeMode.ReleaseFast
  - app runtime   : apprt.Runtime.gtk
  - font engine   : font.main.Backend.fontconfig_freetype
  - renderer      : renderer.generic.Renderer(renderer.OpenGL)
  - libxev        : io_uring
  - kernel version: 6.12.48
  - desktop env   : other
  - GTK version   :
    build         : 4.18.6
    runtime       : 4.18.6
  - libadwaita    : enabled
    build         : 1.7.6
    runtime       : 1.7.6
  - libX11        : enabled
  - libwayland    : enabled

OS Version Information

NixOS 25.11 (Xantusia) x86_64

(Linux only) Display Server

Wayland

(Linux only) Desktop Environment/Window Manager

niri 25.08 (Nixpkgs)

Minimal Ghostty Configuration

// no setting is needed, just having ghostty is enough, this is my config tho except keybindings:

gtk-single-instance = true;
font-family = "JetBrainsMono Nerd Font";
font-size = 18;
freetype-load-flags = ["hinting"];
background-opacity = 1;
window-decoration = "auto";
shell-integration = "detect";
bold-color = "bright";
command = lib.getExe pkgs.zsh;
theme = "Catppuccin Mocha";

Additional Relevant Configuration

Link to my zsh shell configuration via home manager module on NixOS: https://gitlab.com/recluse0/dotfiles/-/blob/master/modules/home-manager/shells/zsh.nix

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.

[rhodes-b]

looking at the discord thread I didn't see anyone suggest that you try shell-integration = none
have you tried that?

[00-kat]

Someone else could reproduce it with their own CLI program that isn't a shell so I doubt that would change anything.

[recluse-be-responsible]

yes I have tried with every shell-integration option posssible, it still happens

[ldemailly]

to repeat from the thread you can see that effect by wrapping a line of text with bg color

https://discord.com/channels/1005603569187160125/1420973267476414526/1421188963921690795

[mitchellh]

This is working as intended, since this is how xterm also behaves given your reproduction.

Please report the compatibility issue to other terminals. Or, if xterm confirms its a bug with them, we'll follow suit.

[ldemailly]

what’s the explanation on the benefit of the behavior? kitty’s seems more useful

How/where to report the xterm bug?

[mitchellh]

Terminal behavior is partially a de jure standard (i.e. ECMA-48) but mostly a de facto standard as defined by popular terminal emulators worldwide. Ghostty takes the approach that our behavior is defined by (1) standards, if available, (2) xterm, if the feature exists, (3) other popular terminals, in that order. This defines what the Ghostty project views as a "standard."

No benefit, its just how we define standard.

[mitchellh]

We don't reproduce xterm bugs unless they're widespread. If you can get Thomas Dickey to confirm this is an xterm bug, we'll change behavior.

[recluse-be-responsible]

Sorry, I didn't quite understand, it is intended to bleed colors like this? And what benefit does it provide with this behavior cuz it doesn't happen with kitty?

[ldemailly]

Emailed thomas about - here is a simpler repro

Put that in /tmp/bug:

#! /bin/bash
for ((i=0; i<14; i++)); do
  printf "%72snormal\033[42m g \033[45m m \033[m\n" " "
done
sleep 60

xterm -geometry 80x24 -e /tmp/bug