`useBackgroundColor` on `tmux` on `alacritty`: Can't See Prompt Text

[soisyourface]

What happened?

Hi all,

After updating to gemini-cli 0.27.0 this morning, I found that I was unable to read the text in the prompt. Here is an example of what I was seeing:

After a moment of panic I decided to go through all of the changenotes and PRs and luckily stumbled upon #16563. Then, I was able to change the ui.useBackgroundColor to false and voila, usable again.

Some additional notes. I use tmux in alacritty. This only happens when I'm in tmux. So yes, this likely only impact a very few individuals but figured it was worth noting. Even if it only helps me and a few others now and in the future.

What did you expect to happen?

I did not expect to have my workflow break and only luckily find the problem and fix.

Client information

Client Information

Run gemini to enter the interactive CLI, then run the /about command.

> /about
│ About Gemini CLI                                                                                                                                                                                                  │
│                                                                                                                                                                                                                   │
│ CLI Version                                                              0.27.0                                                                                                                                   │
│ Git Commit                                                               ec10a7692                                                                                                                                │
│ Model                                                                    auto-gemini-3                                                                                                                            │
│ Sandbox                                                                  no sandbox                                                                                                                               │
│ OS                                                                       linux                                                                                                                                    │
│ Auth Method                                                              gemini-api-key

Login information

No response

Anything else we need to know?

tmux 3.5a on alacritty 0.16.1

[gemini-cli]

Found possible duplicate issues:

• Text is hard to read when using a light theme (white background) in a Terminal #12616

If you believe this is not a duplicate, please remove the status/possible-duplicate label.

[minev-dev]

Have the same issue, but with a bit different color:

[soisyourface]

@gemini-cli this is not a duplicate

[VasilisManol]

I have the same issue inside the zellij multiplexer. Gemini-cli recognizes the terminal as dark no matter what. It started together with the issue #18291 , they look related to me.

[soisyourface]

@VasilisManol, and both are ignored because they have been flagged as possible duplicates?

[VasilisManol]

@soisyourface I hope not. I think as explained here #18291 (comment) these issues are not duplicates. This one is related with #18291 in my view (might be the exact same issue of discovering the proper background color).

[VasilisManol]

This is fixed for running in a zellij session after the latest update.

[chinux23]

Same issue with latest 0.34.0 nightly, setup tmux with ssh.

[devr0306]

@soisyourface have you setup a custom theme for tmux or alacritty?

[soisyourface]

@devr0306 i use a "custom" solarized-dark theme for alacritty and tmux but I'm using the baked-in Solarized Dark theme for gemini-cli.

here is my ~/.config/alacritty/alacritty.toml color definitions:

[colors]
draw_bold_text_with_bright_colors = false
# Colors (Solarized Dark)

# Default colors
[colors.primary]
background = '#002b36'
foreground = '#839496'

# Normal colors
[colors.normal]
black   = '#073642'
red     = '#dc322f'
green   = '#859900'
yellow  = '#b58900'
blue    = '#268bd2'
magenta = '#d33682'
cyan    = '#2aa198'
white   = '#eee8d5'

# Bright colors
[colors.bright]
black   = '#002b36'
red     = '#cb4b16'
green   = '#586e75'
yellow  = '#657b83'
blue    = '#839496'
magenta = '#6c71c4'
cyan    = '#93a1a1'
white   = '#fdf6e3'

[colors.cursor]
cursor = "0x839496"
text = "0x002b36"

and for tmux i use the colors-solorized plugin with the set -g @colors-solarized 'dark' config.

this might be way too unique of a situation for gemini-cli support, which is fine. but mostly it was interesting that it was fine until it wasn't and i had to flip the useBackgroundColor flag.