Ghostty 1.3.1 aborts when running Claude Code in GTK single-instance mode

[granitehq]

Issue Description

On Ubuntu 24.04.5, Ghostty repeatedly exits while I use Claude Code. The crashing process is Ghostty, not claude. Moving my user Fontconfig cache did not resolve it.

Launching a separate Ghostty process with ghostty --gtk-single-instance=false lets Claude start and function in my initial test. I have not yet confirmed long-term stability with that option.

This may relate to closed issue #10432 or discussion #13083, but my observed abort and stack trace differ, so I cannot confirm the same cause.

Expected Behavior

Ghostty remains open and Claude Code runs when Ghostty is launched in GTK single-instance mode.

Actual Behavior

Ghostty exits with SIGABRT and free(): invalid pointer. An earlier crash stack includes FcLangSetHasLang. Claude Code starts and appears to function when Ghostty is launched with --gtk-single-instance=false.

Reproduction Steps

1. Launch Ghostty normally from the desktop. Its process command line is /usr/bin/ghostty --gtk-single-instance=true --initial-window=false.
2. Run claude in a Ghostty window.
3. Ghostty exits. This happened repeatedly, including after I moved ~/.cache/fontconfig aside.
4. From another terminal, run ghostty --gtk-single-instance=false, then run claude in the new window. Claude starts and appears to function in this initial test.

Ghostty Logs

2026-10-04 11:42:56 ghostty[78976]: free(): invalid pointer
2026-10-04 11:42:56 app-com.mitchellh.ghostty.service:
  Main process exited, code=dumped, status=6/ABRT
2026-10-04 11:42:57 systemd-coredump:
  Process 78976 (ghostty) dumped core.

Earlier crash, 2026-10-04 11:23:04, also SIGABRT:
  #7 FcLangSetHasLang (libfontconfig.so.1 + 0x1e1b9)
  #8 ghostty + 0x138fe34

The later crash also ends at ghostty + 0x138fe34, though its
packaged-build stack did not resolve the Fontconfig symbol.

I have not reproduced this with a Ghostty debug build.

### Ghostty Version

```text
Ghostty 1.3.1

Version
  - version: 1.3.1
  - channel: stable
Build Config
  - Zig version   : 0.15.2
  - build mode    : .ReleaseFast
  - app runtime   : .gtk
  - font engine   : .fontconfig_freetype
  - renderer      : renderer.generic.Renderer(renderer.OpenGL)
  - libxev        : epoll
  - kernel version: 6.8.0-146-generic
  - desktop env   : other
  - GTK version   :
    build         : 4.14.5
    runtime       : 4.14.5
  - libadwaita    : enabled
    build         : 1.5.0
    runtime       : 1.5.0
  - libX11        : enabled
  - libwayland    : enabled

Installed Ubuntu package: ghostty 1.3.1-0~ppa2.

### OS Version Information

Ubuntu 24.04.5 LTS; kernel `6.8.0-146-generic`

### (Linux only) Display Server

X11

### (Linux only) Desktop Environment/Window Manager

MATE 1.26.1

### Minimal Ghostty Configuration

```ini
No custom Ghostty settings. The local `config.ghostty` file is empty. The launch-mode option above is the observed difference.

Additional Relevant Configuration

Claude Code 2.1.289. Its --version and --help commands run successfully. No Claude process core dump was recorded during the observed crashes.

AI usage disclosure: OpenAI Codex helped inspect local logs and draft this report. I reviewed and edited the final submission and verified that it accurately describes my observations.

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty documentation and confirm there doesn't exist a configuration option that solves my issue.
• 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.

[jcollie]

This is a duplicate. The Ubuntu Ghostty package needs to link against the system libraries rather than letting Ghostty compile them and link them statically. There's nothing we can do but to urge the maintainers of the Ubuntu package to fix it.