Memory leak after closing windows in single instance mode

[Kacper-Kondracki]

Issue Description

Ghostty seems to never free used memory after spinning up multiple windows. Closing them can even cause additional memory usage consumption. This is apparent when using single instance mode.

Investigation with heaptrack shows the memory is indeed leaking. This is concerning but I'm not sure what it means
(Replicated via running heaptrack ghostty and then spawning new windows via +new-window)

heaptrack.ghostty.7071.zip
Issue happens on
cachyos-extra-v3/ghostty 1.3.1-2.2
extra/ghostty 1.3.1-2
aur/ghostty-nightly-bin 20260526.r16233.ga746d0f-1
Ghostty-1.3.2-main-+a746d0f-x86_64.appimage
Sadly, I'm unable to try ghostty-git with debug information enabled, it won't compile on my system.

Additional information about my system:
Operating System: CachyOS Linux
KDE Plasma Version: 6.6.5
KDE Frameworks Version: 6.26.0
Qt Version: 6.11.1
Kernel Version: 7.0.10-1-cachyos (64-bit)
Graphics Platform: Wayland
Processors: 20 × 13th Gen Intel® Core™ i5-13600KF
Memory: 32 GiB of RAM (31.2 GiB usable)
Graphics Processor: NVIDIA GeForce RTX 4080, Driver Version: 595.71.05
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: Z690 GAMING X DDR4

Expected Behavior

The memory is not leaked when closing windows

Actual Behavior

The memory is leaked until the last window closes fully terminating the ghostty process

Reproduction Steps

1. Open ghostty with gtk single instance on
2. Observe memory usage of the process
3. Spawn new windows and close them

Ghostty Logs

ghostty
info: ghostty version=0.0.0-20260526.r16233.ga746d0f.aur-ghostty-nightly-bin
info: ghostty build optimize=ReleaseFast
info: runtime=.gtk
info: font_backend=.fontconfig_freetype
info: dependency harfbuzz=14.2.0
info: dependency fontconfig=21701
info: renderer=renderer.generic.Renderer(renderer.OpenGL)
info: libxev default backend=io_uring
info(os_locale): setlocale from env result=LC_CTYPE=en_US.UTF-8;LC_NUMERIC=en_IE.UTF-8;LC_TIME=en_DK.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=en_IE.UTF-8;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_IE.UTF-8;LC_NAME=en_US.UTF-8;LC_ADDRESS=en_IE.UTF-8;LC_TELEPHONE=C;LC_MEASUREMENT=en_IE.UTF-8;LC_IDENTIFICATION=en_US.UTF-8
info(gtk): GTK version build=4.22.4 runtime=4.22.4
info(gtk): libadwaita version build=1.9.1 runtime=1.9.1
warning: error reading optional config file, not loading err=error.FileIsEmpty path=/home/nemko/.config/ghostty/config.ghostty
info(config): default shell src=passwd value=/usr/bin/fish
info(config): default working directory src=passwd value=/home/nemko
warning(gtk_ghostty_application): setting GDK_DEBUG=
warning(gtk_ghostty_application): setting GDK_DISABLE=gles-api,vulkan
warning(glib): WARNING: Adwaita: Using GtkSettings:gtk-application-prefer-dark-theme with libadwaita is unsupported. Please use AdwStyleManager:color-scheme instead.
warning(glib): WARNING: Adwaita: The resource style-dark.css is deprecated and shouldn't be used anymore. Use style.css with media queries instead.
warning(glib): WARNING: Adwaita: The resource style-hc.css is deprecated and shouldn't be used anymore. Use style.css with media queries instead.
warning(glib): WARNING: Adwaita: The resource style-hc-dark.css is deprecated and shouldn't be used anymore. Use style.css with media queries instead.
info(opengl): loaded OpenGL 4.6
warning(gtk_ghostty_surface): gtk-xft-dpi has invalid value (0), using default
info(io_exec): found Ghostty resources dir: /usr/share/ghostty
info(io_exec): shell integration automatically injected shell=.fish
warning(gtk_ghostty_application): unimplemented action=.cell_size
info(io_exec): started subcommand path=/bin/sh pid=11487
warning(io_handler): OSC 7 uri must contain a hostname: error.UriMissingHost
warning(gtk_ghostty_surface): gtk-xft-dpi has invalid value (0), using default
info(opengl): loaded OpenGL 4.6
warning(gtk_ghostty_surface): gtk-xft-dpi has invalid value (0), using default
info(io_exec): found Ghostty resources dir: /usr/share/ghostty
info(io_exec): shell integration automatically injected shell=.fish
warning(gtk_ghostty_application): unimplemented action=.cell_size
info(io_exec): started subcommand path=/bin/sh pid=11537
warning(gtk_ghostty_surface): gtk-xft-dpi has invalid value (0), using default
warning(io_handler): OSC 7 uri must contain a hostname: error.UriMissingHost
info(opengl): loaded OpenGL 4.6
warning(gtk_ghostty_surface): gtk-xft-dpi has invalid value (0), using default
info(io_exec): found Ghostty resources dir: /usr/share/ghostty
info(io_exec): shell integration automatically injected shell=.fish
warning(gtk_ghostty_application): unimplemented action=.cell_size
warning(gtk_ghostty_surface): gtk-xft-dpi has invalid value (0), using default
info(io_exec): started subcommand path=/bin/sh pid=11559
warning(io_handler): OSC 7 uri must contain a hostname: error.UriMissingHost
info(opengl): loaded OpenGL 4.6
warning(gtk_ghostty_surface): gtk-xft-dpi has invalid value (0), using default
info(io_exec): found Ghostty resources dir: /usr/share/ghostty
info(io_exec): shell integration automatically injected shell=.fish
warning(gtk_ghostty_application): unimplemented action=.cell_size
warning(gtk_ghostty_surface): gtk-xft-dpi has invalid value (0), using default
info(io_exec): started subcommand path=/bin/sh pid=11582
warning(io_handler): OSC 7 uri must contain a hostname: error.UriMissingHost
info(io_exec): pty fd closed, read thread exiting
info(surface): surface closed addr=55d4ba8f8130
info(io_exec): pty fd closed, read thread exiting
info(surface): surface closed addr=55d4ba0a1fb0
info(io_exec): pty fd closed, read thread exiting
info(surface): surface closed addr=55d4b9843ea0
info(io_exec): pty fd closed, read thread exiting
info(surface): surface closed addr=55d4b8b25190

Ghostty Version

Ghostty 0.0.0-20260526.r16233.ga746d0f.aur-ghostty-nightly-bin

Version
- version: 0.0.0-20260526.r16233.ga746d0f.aur-ghostty-nightly-bin
- channel: tip
Build Config
- Zig version   : 0.15.2
- build mode    : .ReleaseFast
- app runtime   : .gtk
- font engine   : .fontconfig_freetype
- renderer      : renderer.generic.Renderer(renderer.OpenGL)
- libxev        : io_uring
- kernel version: 7.0.10-1-cachyos
- desktop env   : other
- GTK version   :
build         : 4.22.4
runtime       : 4.22.4
- libadwaita    : enabled
build         : 1.9.1
runtime       : 1.9.1
- libX11        : enabled
- libwayland    : enabled

OS Version Information

CachyOS x86_64, Linux 7.0.10-1-cachyos

(Linux only) Display Server

Wayland

(Linux only) Desktop Environment/Window Manager

KDE Plasma 6.6.5

Minimal Ghostty Configuration

gtk-single-instance = true

Additional Relevant Configuration

No response

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]

This was determined along time ago to be a GTK problem that needs fixed upstream since it happens from all internal GTK apis.

#5491

[Kacper-Kondracki]

I don't see any bug report that was forwarded to GTK issue tracker regarding this, and as reducing my role to a merely user I know no implementations details on how GTK is used in Ghostty, although it is in my special interest to have it fixed, it is not something I can properly report to GTK. This is something that maintainers of the ghostty gtk/libadwaita part would need to consult with GTK people directly. This is not good that it is broken for such long time

[rhodes-b]

I don't see any bug report that was forwarded to GTK issue tracker regarding this

Because its not acceptable to go to them without a somewhat minimal reproduction, instead of saying build this pretty large application and figure it out.

and as reducing my role to a merely user I know no implementations details on how GTK is used in Ghostty

The code is open source, you are free to study all the details.

although it is in my special interest to have it fixed

This is also a benefit of open source anyone can look into this problems and try to fix them.

This is not good that it is broken for such long time.

Beyond the initial bug report by me there has been essentially zero reports of this being a problem for people, its trivial to solve you just restart ghostty every once in awhile if its becoming a problem.
Its not significant unless you are closing hundreds of tabs / splits / windows over a instance of ghostty being open.
I think its very reasonable if you are doing that you see terminals more as a scratchpad instead of a very long running application so a restart every now and then is fine.

To be more clear on the Ghostty is free open source software, the MIT license has a specific no warranty provided as is clause, and the maintainers work on what they want to work on. The issue above was not closed for no reason, multiple people who are pretty familiar with ghostty came to the conclusion that the problem is most likely somewhere in the GTK stack / there is some undocumented reason on what ghostty is doing to have GTK leak this memory if its not just on purpose. With the conclusion someone could provide more proof that it really is a ghostty issue and not GTK.

This is something that maintainers of the ghostty gtk/libadwaita part would need to consult with GTK people directly

This is likely to be the best way to getting the problem fixed, as one of the people who looked into the problem on the ghostty side I can speak for myself and say I'm not interested in this method as I noted above just going to their bug tracker is not the correct approach, and I failed to get a minimal reproduction after some effort. Thats not speaking for any other people who work on GTK side though.

If these viewpoints push you away from using ghostty there are many other great terminals out there