kitty frozen after frequent resizing

Describe the bug
If kitty is filled with content, especially a subshell with prompt like virsh or aichat, it will freeze after resizing frequently. Then kitty uses a lot of CPU and rejects SIGTERM, so I can only send SIGKILL to shut it down.

To Reproduce
Steps to reproduce the behavior:

1. Start kitty
2. Fill somthing, sometimes even don't need
3. Resize window quickly, including toggle float or split
4. See error

Screenshots
screen capture video

Environment details

kitty 0.40.0 created by Kovid Goyal
Linux laptop 6.13.7-arch1-1 #1 SMP PREEMPT_DYNAMIC Thu, 13 Mar 2025 18:12:00 +0000 x86_64
S{PRETTY_NAME} 6.13.7-arch1-1 (/dev/tty)

DISTRIB_ID="Arch"
DISTRIB_RELEASE="rolling"
DISTRIB_DESCRIPTION="Arch Linux"
Running under: Wayland (hyprland v0.47.2,) missing: blur
OpenGL: '4.6 (Core Profile) Mesa 25.0.1-arch1.2' Detected version: 4.6
Frozen: False
Fonts:
  medium: JetBrainsMono-Regular: /usr/share/fonts/TTF/JetBrainsMono-Regular.ttf:0
          Features: ()
    bold: JetBrainsMono-SemiBold: /usr/share/fonts/TTF/JetBrainsMono-SemiBold.ttf:0
          Features: ()
  italic: JetBrainsMono-Italic: /usr/share/fonts/TTF/JetBrainsMono-Italic.ttf:0
          Features: ()
      bi: JetBrainsMono-SemiBoldItalic: /usr/share/fonts/TTF/JetBrainsMono-SemiBoldItalic.ttf:0
          Features: ()
Paths:
  kitty: /usr/bin/kitty
  base dir: /usr/lib/kitty
  extensions dir: /usr/lib/kitty/kitty
  system shell: /usr/bin/bash
System color scheme: no_preference. Applied color theme type: none
Loaded config files:
  /home/mop/.config/kitty/kitty.conf

Config options different from defaults:
cursor_trail            1
enable_audio_bell       False
font_size               14.0
window_padding_width    FloatEdges(left=14.0, top=14.0, right=14.0, bottom=14.0)
Added shortcuts:
	ctrl+insert →  copy_to_clipboard
	ctrl+shift+insert →  paste_from_selection
Changed shortcuts:
	shift+insert →  paste_from_clipboard
Colors:
	active_border_color     #b4befe   
	active_tab_background   #cba6f7   
	active_tab_foreground   #11111b   
	background              #1e1e2e   
	bell_border_color       #f9e2af   
	color0                  #45475a   
	color1                  #f38ba8   
	color10                 #a6e3a1   
	color11                 #f9e2af   
	color12                 #89b4fa   
	color13                 #f5c2e7   
	color14                 #94e2d5   
	color15                 #a6adc8   
	color2                  #a6e3a1   
	color3                  #f9e2af   
	color4                  #89b4fa   
	color5                  #f5c2e7   
	color6                  #94e2d5   
	color7                  #bac2de   
	color8                  #585b70   
	color9                  #f38ba8   
	cursor                  #f5e0dc   
	cursor_text_color       #1e1e2e   
	foreground              #cdd6f4   
	inactive_border_color   #6c7086   
	inactive_tab_background #181825   
	inactive_tab_foreground #cdd6f4   
	mark1_background        #b4befe   
	mark1_foreground        #1e1e2e   
	mark2_background        #cba6f7   
	mark2_foreground        #1e1e2e   
	mark3_background        #74c7ec   
	mark3_foreground        #1e1e2e   
	selection_background    #f5e0dc   
	selection_foreground    #1e1e2e   
	tab_bar_background      #11111b   
	url_color               #f5e0dc   

Important environment variables seen by the kitty process:
	PATH                                /home/mop/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/lib/jvm/default/bin:/opt/nessus/bin:/opt/nessus/sbin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl
	LANG                                zh_CN.UTF-8
	EDITOR                              nvim
	SHELL                               /usr/bin/bash
	GLFW_IM_MODULE                      ibus
	DISPLAY                             :0
	WAYLAND_DISPLAY                     wayland-1
	USER                                mop
	XDG_BACKEND                         wayland
	XDG_SEAT                            seat0
	XDG_SESSION_TYPE                    wayland
	XDG_CURRENT_DESKTOP                 Hyprland
	XDG_SESSION_CLASS                   user
	XDG_VTNR                            1
	XDG_SESSION_ID                      1
	XDG_RUNTIME_DIR                     /run/user/1000

Additional context
I tried kitty --config NONE with setting hyprland.conf to be default, still freeze.

[kovidgoyal]

Is this specific to hyprland? I cant get it to freeze in either hyprland or sway with those steps.
It might help if you wrote a small script that used hyprctl to toggle layouts or window sizes or similar to reproduce it.

Try running kitty with --debug-rendering and see if it is generates output when frozen. Also, attach gdb to it and get a stack dump so we can see where it is looping.

I may have made some progress, see this video. And I will try --debug-rendering or gdb tomorrow if needed.

The bug can't be reproduced today using kitty --config NONE, quite strange. I checked kitty.conf and got the conclusion that the freeze will occur if set font_size 14 or window_padding_width 14. Here are script, output of kitty --debug-rendering --hold ./foo.sh and gdb dump. The script works fine under both dwindle and master layout.

[kovidgoyal]

It's already fixed in master. Use a nightly build.

Oh, I didn't notice that, luv u.