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Cursor blinking within tmux stops after upgrade kitty to 0.22 #3906

laggardkernel opened this issue Aug 7, 2021 · 2 comments

Cursor blinking within tmux stops after upgrade kitty to 0.22 #3906

laggardkernel opened this issue Aug 7, 2021 · 2 comments


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Describe the bug

Formerly, the cursor blinks normally within tmux. After upgrading kitty to 0.22.x. It doesn't blink within tmux anymore.


To Reproduce


  • kitty with default config
  • tmux 3.2a with following minimal config
  • OS: macOS 10.14.6
# minimal tmux conf: test.conf
set-option -gs default-terminal "tmux-256color"
set-option -ga terminal-overrides ',*:Ss=\E[%p1%d q:Se=\E[5 q'

Steps to reproduce the behavior:

  1. Open kitty with default config.
  2. Start tmux with tmux -f ./test.conf -S ./test.socket

Then the cursor stops blinking. Downgrading kitty back to 0.21. The problem disappears.

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This is a bug in tmux that was masked by a bug in kitty. The bug in
kitty was fixed in 0.22.0 (see #3808)


kitty --dump-commands tmux

In the list of commands tmux sends kitty you will see
screen_reset_mode 12 1

This is the escape code

CSI ? 12 l

which is supposed to stop the cursor blinking, as described
(search the page for Ps = 1 2)

I dont use tmux so I cant comment on why it is doing this or how to get
it to stop doing it.

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@kovidgoyal Thanks for your reply. The clue you gave me did help.

To be frank, I know nothing about the source code of tmux. But searching 12l gives no result in the source code. One of the possible reason is that tmux is firing cnorm.

❯ infocmp xterm-kitty | grep '12l'
        clear=\E[H\E[2J, cnorm=\E[?12l\E[?25h, cr=^M,

I tried to override cnorm within tmux and my cursor blinks now.

# tmux.conf
# change \E[?12l to \E[?12h
set-option -ga terminal-overrides ',xterm-kitty:cnorm=\E[?12h\E[?25h'


Clues lead me to the current solution

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