Colors are completely off in tmux

Describe the bug

When having a light theme, Copilot CLI light theme's colors are completely wrong when running in tmux. Outside tmux, everything's fine.

tmux vs regular shell:

The problem isn't just the aesthetics, some text is genuinely unreadable (like bright yellow on light background in the screenshot above).

Affected version

GitHub Copilot CLI 1.0.61

Steps to reproduce the behavior

• Set a light terminal theme
• Set the theme to "light" or "auto" in Copilot CLI
• Spawn the command menu with "/"

Expected behavior

Exactly the same color in and outside tmux.

Additional context

Env:

• WSL2, NixOS
• Terminal emulator: Windows Terminal
• Fish shell

In tmux:

❯ echo TERM=$TERM; tput colors
TERM=tmux-direct
16777216

❯ echo $COLORTERM
truecolor

Relevant tmux config:

# Enable true color support
set-option -as terminal-features ',*:RGB'
set -ga update-environment "COLORTERM"
set -ga update-environment "COLORFGBG"
set-environment -g COLORTERM "truecolor"

Issue #4212 seems related but I'm not sure if it's exactly the same. There is also issue #135 but it hasn't received any attention in months.

記載されている WSL2、NixOS、Windows Terminal、Fish の設定に従い、tmux 内外で Copilot CLI 1.0.61 を使用してライトテーマの色の不一致を再現します。まず、tmux の環境値と設定を issue #4212 および issue #135 と比較します。tmux 内外で "/" を入力してコマンドメニューを開いたときに、ライトテーマまたは自動テーマで同じ読みやすい色が表示されれば完了です。