Input field background renders black with near-invisible text (low contrast) mid-session

[Piotr779]

Describe the bug

Mid-session, only the command input field's background turned black, making typed text nearly invisible against it. The rest of the terminal/session output rendered normally and was unaffected. A standard terminal  reset  did not fix it, indicating the issue is in the CLI's own TUI rendering rather than a terminal-level escape sequence leak.

Affected version

Copilot CLI version: 1.0.81

Steps to reproduce the behavior

1. Run  copilot  inside a tmux session (TERM=tmux-256color).
2. Use the CLI normally for a while (no manual  /theme  change).
3. Observe the input field's background suddenly turns black with low-contrast/invisible text, while surrounding output text stays normal.
4. Run  reset  in the terminal — input field remains black.

Expected behavior

Input field should maintain consistent theme-appropriate contrast for the whole session.

Additional context

Suspected cause: Theme/color-mode detection or caching bug specific to tmux ( TERM=tmux-256color ), possibly triggered by a state change during the session (resize, mode switch, subagent/tool output, etc.).

[ccapon]

Same problem here.

Affected environment

• OS: Ubuntu 22.04.5 LTS (jammy)
• Terminal emulator: GNOME Terminal (profile: light background rgb(255,255,255),
  dark foreground rgb(23,20,33), use-theme-colors=false)
• Terminal multiplexer: tmux (originally 3.2a, default-terminal "screen-256color",
  TERM=screen-256color, COLORTERM=truecolor) — issue persisted even after
  upgrading to tmux 3.5a with allow-passthrough on
• Shell: zsh (oh-my-zsh, theme robbyrussell)
• GTK theme: Yaru, color-scheme default (light), night-light off
• Copilot CLI version affected: 1.0.80 / 1.0.81 (regression started exactly at
  auto-update, confirmed via ~/.copilot/logs/ timestamps: "Successfully updated
  binary" at 06:32 UTC matched the exact moment the prompt became unreadable)
• Last known-good version: 1.0.79

Attempted workarounds (none resolved it)

• /theme cycled through all modes
• Forced "theme": "light" and "colorMode": "light" directly in
  ~/.copilot/settings.json
• Set "pinnedPrompts": false in ~/.copilot/settings.json
• Restarted the CLI after each change
• Upgraded tmux 3.2a -> 3.5a from source and enabled set -g allow-passthrough on
  (rules out stale OSC background-color queries being blocked by old tmux)

Working workaround

Pin the CLI to version 1.0.79:

npm install --prefix ~/.local/copilot-1.0.79 @github/copilot@1.0.79
ln -sf ~/.local/copilot-1.0.79/node_modules/.bin/copilot ~/.local/bin/copilot
export COPILOT_AUTO_UPDATE=false   # persisted in ~/.zshrc

This restores a readable prompt box. The replaced binary was previously
~/.local/bin/copilot (self-updating single executable, v1.0.81), kept as backup.