Prompt box and highlighted menu items render invisible (dark-on-dark) inside tmux

Describe the bug

Copilot CLI's prompt input box and highlighted/selected menu list items are unreadable (dark text on dark/matching background) when run inside tmux. The same session works correctly in a plain iTerm2 tab with no tmux.

During troubleshooting, ruled out the following:

• Stale  COLORFGBG  env var — unset it, no change.
• iTerm2 automatic light/dark profile switching — disabled it, no change.
• tmux truecolor passthrough — confirmed via  tmux info  that  Tc / RGB  report  true  after adding  set -ga terminal-overrides ",xterm-256color:Tc" , and  tmux capture-pane -e  shows correct 24-bit RGB SGR codes are being preserved (not quantized), so this isn't a color-depth/passthrough issue.
•  tmux allow-passthrough on  is enabled; OSC 11 background-color queries do get a reply (confirmed manually with  printf '\033]11;?\033\' ), though the reply appears to arrive after Copilot's internal detection timeout in some tests.
• Restarting tmux server fully, restarting iTerm2 fully — no change.
• Switching Copilot's  theme  setting between  default ,  dim ,  github  — same problem persists in all of them, only inside tmux.

Affected version

GitHub Copilot CLI 1.0.73. Run 'copilot update' to check for updates.

Steps to reproduce the behavior

1. Launch iTerm2, start a tmux session, run  copilot .
2. Type in the prompt input box, or open a menu with selectable items (e.g.  /theme ).
3. Text in the prompt box / highlighted menu rows is invisible — same foreground/background color.

Expected behavior

The colors should be legible regardless of being run inside tmux or not

Additional context

No response

Le rapport n’identifie aucun fichier source ni aucun test. Reproduisez le problème avec GitHub Copilot CLI 1.0.73 dans iTerm2 et tmux, comparez-le avec un onglet iTerm2 standard et examinez le comportement signalé de truecolor et OSC 11. Le travail est terminé lorsque le texte de l’invite et les éléments de menu mis en surbrillance restent lisibles dans tmux avec les thèmes indiqués.