Output from background proccesses disappears when adjusting windows about kitty HOT 3 CLOSED

Does not replicate for me with those steps, using kitty and bash with default configurations.

Screensshot generated by running:

kitty --config=NONE -o shell=bash -o enabled_layouts=tall

waiting for a few foobars and splitting.

Indeed, terminals in general and kitty in particular do not know or care whether processes writing to their tty devices are background or foreground, there is no way for them to know if any particular write comes from the foregound or background process. This will be something in your shell rc files most likely related to how it redraws the prompt on a resize.

from kitty.

You didn't run the script in the background with &. Your test should be "sh /t/bg.sh &"

from kitty.

Ah, right sorry. Yes in that case this will happen, because on resize
kitty shell integration clears everything after the prompt on resize to allow
the shell to redraw its prompt correctly. See
https://sw.kovidgoyal.net/kitty/shell-integration

In particular:

Glitch free window resizing even with complex prompts. Achieved by erasing the prompt on resize and allowing the shell to redraw it cleanly.

Turn off shell integration if you dont want this behavior in kitty.conf

Although I will note that having multiple processes writing to the same
tty device is broken in so many ways its not even funny.

from kitty.