Input color becomes black in tmux control mode (tmux -CC) when SSH

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

• #4744
• #4960

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are all the relevant tmux installs >= 3.4? this looks like possibly related to https://github.com/openai/codex/issues/4744#issuecomment-3386362145

not super familiar with tmux, but i'm not sure at first brush why control mode would prevent background color querying from working.

I have exactly the same situation with zellij. This wasn't the case in earlier versions of Codex

@nornagon-openai I use tmux 3.4 and 3.5a, more specific environment version has been updated in the original issue

different 0.46.0 alpha behave quite differently, specifically, alpha 4, 5, 6 has a lot of change I think.

By the way, on the version before alpha-4, even I use tmux >= 3.4, I still experienced the issue mentioned in https://github.com/openai/codex/issues/4744

Two related commit are: https://github.com/openai/codex/pull/4957 (in alpha 5) and https://github.com/openai/codex/commit/f4bc03d7c049aaec020d431498949dfb6523f32e (in alpha 6)

0.46.0-alpha.4

• ssh with tmux control mode

<img width="797" height="323" alt="Image" src="https://github.com/user-attachments/assets/beff9d2a-e396-4936-acbc-20ca29a0a176" />

• ssh with normal tmux

<img width="616" height="303" alt="Image" src="https://github.com/user-attachments/assets/d78a8590-2870-47d3-893b-4eed0595333b" />

• ssh without tmux

<img width="562" height="327" alt="Image" src="https://github.com/user-attachments/assets/54e36756-7e01-4822-be5a-0b13238fb18f" />

0.46.0-alpha.5

• ssh with tmux control mode

<img width="863" height="310" alt="Image" src="https://github.com/user-attachments/assets/c4b90cb4-c027-4686-ba12-03cebf67b751" />

• ssh with normal tmux

<img width="852" height="315" alt="Image" src="https://github.com/user-attachments/assets/ca343454-f730-4827-9c8c-7b511dc14132" />

• ssh without tmux

<img width="856" height="312" alt="Image" src="https://github.com/user-attachments/assets/cacc7871-c0ec-4877-ab4c-0b2ea12b84eb" />

0.46.0-alpha.6

• ssh with tmux control mode

<img width="847" height="305" alt="Image" src="https://github.com/user-attachments/assets/725e93a1-d6fe-42f8-b30b-cba4d4b35023" />

• ssh with normal tmux

<img width="857" height="332" alt="Image" src="https://github.com/user-attachments/assets/a071649d-71dc-4053-9073-5ed78eaabd75" />

• ssh without tmux

<img width="803" height="332" alt="Image" src="https://github.com/user-attachments/assets/616065e6-1b56-42c2-9bb9-89146db36f5c" />

I found that, it is due to the wrong bg readout

https://github.com/openai/codex/blob/26f7c46856060f440615645bdf2faf9e62c74e72/codex-rs/tui/src/terminal_palette.rs#L143-L152

• normal tmux

query_default_colors called
read 48 bytes, buffer len: 48, fg: Some((0, 0, 0)), bg: Some((255, 255, 255))
returning Some((0, 0, 0), (255, 255, 255))

• tmux control mode

query_default_colors called
read 48 bytes, buffer len: 48, fg: Some((0, 0, 0)), bg: Some((0, 0, 0))
returning Some((0, 0, 0), (0, 0, 0))

So it failed to give a correct input for

https://github.com/openai/codex/blob/26f7c46856060f440615645bdf2faf9e62c74e72/codex-rs/tui/src/style.rs#L21-L28

• normal tmux

user_message_bg called with terminal_bg: (255, 255, 255)
top: (0, 0, 0)
blended: (229, 229, 229)
best_color result: Indexed(254)

• tmux control mode

user_message_bg called with terminal_bg: (0, 0, 0)
top: (255, 255, 255)
blended: (25, 25, 25)
best_color result: Indexed(234)

In the parent commit of https://github.com/openai/codex/commit/e896db1180cc1e893f6d3d878bafe909c518c24e (that is https://github.com/openai/codex/commit/96acb8a74e14897faa36d66cd50768c0b0978e59)

the query_default_colors function is also broken, but the user_message_bg is also broken either

• normal tmux

Starting user_message_bg with terminal_bg: (255, 255, 255)
top: (0, 0, 0), bottom: (255, 255, 255)
color_level: ColorLevel { level: 2, has_basic: true, has_256: true, has_16m: false }
target: (229, 229, 229)
Using default color
Returning color: Reset

• tmux control mode

Starting user_message_bg with terminal_bg: (0, 0, 0)
top: (255, 255, 255), bottom: (0, 0, 0)
color_level: ColorLevel { level: 2, has_basic: true, has_256: true, has_16m: false }
target: (25, 25, 25)
Using default color
Returning color: Reset

• without tmux

Starting user_message_bg with terminal_bg: (255, 255, 255)
top: (0, 0, 0), bottom: (255, 255, 255)
color_level: ColorLevel { level: 2, has_basic: true, has_256: true, has_16m: false }
target: (229, 229, 229)
Using 256 colors, index: 254
Returning color: Indexed(254)

Only the last one works fine, it is due to in the old version of codex, terminal_palette() returns None when using under tmux, but now, terminal_palette() no longer exists, so just let it go.

Now the problem becomes that query_default_colors is broken all the time

A minimal repro

import sys

sys.stdout.buffer.write(b"\x1b]10;?\x07\x1b]11;?\x07")
sys.stdout.flush()

In normal tmux, it will print

]10;rgb:0000/0000/0000\]11;rgb:fffe/ffff/ffff\

we will get 0,0,0 as fg and 255,255,255 as bg

But in tmux control mode, it will print

^[]10;rgb:0000/0000/0000^G^[]11;rgb:0000/0000/0000^G

that is, we get 0,0,0 as fg and bg both

Edit: well, it seems that it is fixed in a later tmux verison, but it is too new for a lts ubuntu, tmux 3.5a works, so maybe that why my local tmux works but the ssh's tmux doesn't.

Thanks for the detailed investigation. It seems like this is a tmux bug which is fixed in 3.5a (or possibly earlier?), so I'm going to close this out.

@Artawower I would suggest to try the previous minimal repo in zellij to determine whether it is the same issue