In tmux 3.4, ZSH does not work correctly either locally or by SSH

[marovira]

Windows Terminal version

1.22.2912.0

Windows build number

10.0.22631.4391

Other Software

• Git for Windows 2.47.0.windows.2
• zsh 5.9
• tmux 3.4
• OpenSSH_9.9p1, OpenSSL 3.2.3 3 Sep 2024

Steps to reproduce

There are two issues that appear related as they are rendering problems that only occur when using ZSH. In order to reproduce the issues, either of the following is required:

• A Git bash installation with ZSH
• Connecting to a remote Linux server through SSH (via Git Bash) that is running ZSH.

Issue 1 Steps

1. Start a terminal with ZSH using either of the aforementioned setups.
2. Start typing any command. Longer commands will display the issue more clearly.
3. Delete the command.

Issue 2 Steps

This specific issue only occurs on Linux servers with tmux and ZSH:

1. Connect to a server using SSH. The terminal must be ZSH.
2. Open tmux
3. Open a new vertical split.
4. Switch to the right-side split and enter any command.
5. Now switch back to the original split and enter a different command.

Note

The flickering issue is not present in version 1.18.10301. The tmux issue however is present on any version since.

Expected Behavior

For both issues, the terminal should render the text correctly and the cursor should not flicker.

Actual Behavior

Issue 1

When entering or deleting text, the cursor jumps to the beginning of the current line and then back to the end rapidly. This is easier to see when deleting a command. Unfortunately it appears that screen recording doesn't showcase the issue properly so I can't show it.

Issue 2

See that the ~/Documents > should've appeared on the right pane, and there's a gap on the right side before the cursor where ~/Documents should've appeared.

[marovira]

Extra info: the tmux issue just started happening recently. I'm not entirely sure what triggered it, but it wasn't happening earlier this year.

[carlos-zamora]

Thanks for filing! Issue 1 is actually being tracked over in #6217. We'll still use this issue to track the second one you mentioned.

Extra info: the tmux issue just started happening recently. I'm not entirely sure what triggered it, but it wasn't happening earlier this year.

Have you updated tmux in the past year?

[marovira]

Thanks for filing! Issue 1 is actually being tracked over in #6217. We'll still use this issue to track the second one you mentioned.

Extra info: the tmux issue just started happening recently. I'm not entirely sure what triggered it, but it wasn't happening earlier this year.

Have you updated tmux in the past year?

Good to know the first issue has been reported, thanks!

As for updating tmux, yes I have updated it a few months ago when I did a system update on my linux servers. I believe the issue only started occurring recently, but it may be that I just noticed it recently.

[marovira]

This may or may not be related, but it appears that Terminal isn't rendering correctly whenever a program opens up multiple splits. Here's another case that looks similar:

1. Connect to a server using SSH. Choice of terminal doesn't matter (issue occurs with both bash and zsh)
2. Open a file in Vim.
3. Now type :vert sb to open that same file in a new vertical split.
4. Switch to the right-hand split and close it using :q

See that the terminal isn't rendered correctly. Here's an example
Before closing the split:

After closing the split:

Note that this issue can seemingly only be reproduced when the Terminal is maximised. It doesn't seem to happen on a smaller window.
The text can be recovered if you move the cursor through the missing lines, forcing it to re-render.