codex - 💡(How to fix) Fix Codex 0.130.0 still loses background/pill colors inside tmux 3.6a

What version of Codex CLI is running?

0.130.0

What subscription do you have?

Unknown / not relevant to rendering issue.

Which model were you using?

gpt-5.3-codex medium

What platform is your computer?

Ubuntu 24.04.3 LTS (Noble Numbat), Linux 6.8.0-110-generic, x86_64.

This is a remote SSH environment accessed from VS Code integrated terminal.

What terminal emulator and version are you using (if applicable)?

VS Code integrated terminal over SSH, running tmux 3.6a.

Inside tmux:

TERM=tmux-256color
COLORTERM=truecolor
TERM_PROGRAM=tmux
tmux 3.6a
mouse off
history-limit 100000
mode-keys vi
terminal-overrides[1] *:smcup@:rmcup@

What issue are you seeing?

Codex loses the filled background/pill styling for parts of the TUI when run inside tmux 3.6a. The same Codex session outside tmux in the same VS Code terminal renders the expected colored backgrounds/pills.

This appears similar to the closed issue #19741, but I can still reproduce it with Codex CLI 0.130.0 on Ubuntu + VS Code Remote SSH + tmux 3.6a.

Important detail: tmux itself still renders ANSI/truecolor correctly. For example, this works inside tmux 3.6a:

printf '\033[31mRED\033[0m \033[36mCYAN\033[0m \033[38;2;255;80;80mTRUECOLOR\033[0m\n'

So this does not look like a general tmux truecolor failure. It seems specific to Codex TUI color/background detection under tmux 3.6a.

What steps can reproduce the bug?

1. Start from VS Code integrated terminal connected to a remote Ubuntu host over SSH.
2. Confirm tmux 3.6a is active:

tmux -V
# tmux 3.6a

1. Create or attach a tmux session:

tmux new -s codex_tmux

1. Confirm ANSI/truecolor output works inside tmux:

printf '\033[31mRED\033[0m \033[36mCYAN\033[0m \033[38;2;255;80;80mTRUECOLOR\033[0m\n'

1. Run Codex inside tmux:

codex

1. Compare with running codex outside tmux in the same VS Code terminal.

What is the expected behavior?

Codex should render the same TUI background/pill colors inside tmux 3.6a as it does outside tmux, assuming ANSI/truecolor output is working.

What is the actual behavior?

Inside tmux 3.6a, Codex renders without the expected background/pill fill for some TUI elements. Outside tmux, the same UI renders with the expected color/background styling.

Additional information

This was tested after upgrading from tmux 3.4 to tmux 3.6a. The environment was restarted with no old tmux server left running.

The active tmux binary is:

tmux is /usr/local/bin/tmux
tmux is /usr/bin/tmux
tmux is /bin/tmux
tmux 3.6a

The existing closed issue #19741 describes what looks like the same root cause involving OSC 11 / terminal background detection through tmux. If that issue was expected to be fixed, this may be a remaining reproduction on Codex 0.130.0 and Linux/VS Code Remote SSH.