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codex - 💡(How to fix) Fix Shift+Enter is not recognized inside tmux because Codex does not enable modifyOtherKeys / Ext 2

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Fix Action

Fix / Workaround

Workaround / validation

Code Example

tmux list-panes -a -F '#{pane_id} #{pane_current_command} #{pane_key_mode}'

---

%0 codex VT10x

---

%3 nvim Ext 2

---

printf '\e[>4;2m' > /dev/pts/0

---

pub(super) fn enable_keyboard_enhancement() {
    if keyboard_enhancement_disabled() {
        return;
    }

    let _ = execute!(
        stdout(),
        PushKeyboardEnhancementFlags(
            KeyboardEnhancementFlags::DISAMBIGUATE_ESCAPE_CODES
                | KeyboardEnhancementFlags::REPORT_EVENT_TYPES
                | KeyboardEnhancementFlags::REPORT_ALTERNATE_KEYS
        )
    );
}

---

ESC [ > 4 ; 2 m

---

pub(super) fn reset_keyboard_reporting_after_exit() {
    let _ = execute!(
        stdout(),
        PopKeyboardEnhancementFlags,
        ResetKeyboardEnhancementFlags,
        DisableModifyOtherKeys
    );
}

impl Command for DisableModifyOtherKeys {
    fn write_ansi(&self, f: &mut impl fmt::Write) -> fmt::Result {
        f.write_str("\x1b[>4;0m")
    }
}

---

ESC [ > 4 ; 0 m
RAW_BUFFERClick to expand / collapse

What version of Codex CLI is running?

codex-cli 0.129.0

What subscription do you have?

plus

Which model were you using?

No response

What platform is your computer?

No response

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

No response

What issue are you seeing?

Problem

Inside tmux, Shift+Enter is received by Codex as plain Enter, so it submits instead of inserting a newline.

The same terminal/tmux setup works in Neovim.

Environment

  • Terminal: kitty 0.46.2
  • tmux: 3.6a
  • tmux config:
    • extended-keys on
    • extended-keys-format csi-u
    • xterm-keys on
    • terminal-features includes xterm*:extkeys
  • Codex: codex-cli 0.129.0

Reproduction

  1. Start Codex inside tmux.
  2. Run /keymap debug.
  3. Press Shift+Enter.
  4. Codex reports plain Enter / no shift modifier.
  5. tmux reports the Codex pane as VT10x.

Commands used:

tmux list-panes -a -F '#{pane_id} #{pane_current_command} #{pane_key_mode}'

Observed:

%0 codex VT10x

Compare with Neovim in the same tmux server:

%3 nvim Ext 2

Workaround / validation

Manually enabling xterm modifyOtherKeys mode 2 for the Codex pane fixes it:

printf '\e[>4;2m' > /dev/pts/0

After that, the Codex pane changes to Ext 2, and Shift+Enter is reported correctly.

Suspected cause

Codex currently enables crossterm/kitty keyboard enhancement in codex-rs/tui/src/tui/keyboard_modes.rs:

pub(super) fn enable_keyboard_enhancement() {
    if keyboard_enhancement_disabled() {
        return;
    }

    let _ = execute!(
        stdout(),
        PushKeyboardEnhancementFlags(
            KeyboardEnhancementFlags::DISAMBIGUATE_ESCAPE_CODES
                | KeyboardEnhancementFlags::REPORT_EVENT_TYPES
                | KeyboardEnhancementFlags::REPORT_ALTERNATE_KEYS
        )
    );
}

but it does not send xterm/tmux modifyOtherKeys mode 2:

ESC [ > 4 ; 2 m

Codex already sends the corresponding reset on exit in codex-rs/tui/src/tui/keyboard_modes.rs:

pub(super) fn reset_keyboard_reporting_after_exit() {
    let _ = execute!(
        stdout(),
        PopKeyboardEnhancementFlags,
        ResetKeyboardEnhancementFlags,
        DisableModifyOtherKeys
    );
}

impl Command for DisableModifyOtherKeys {
    fn write_ansi(&self, f: &mut impl fmt::Write) -> fmt::Result {
        f.write_str("\x1b[>4;0m")
    }
}
ESC [ > 4 ; 0 m

via DisableModifyOtherKeys, but there is no matching enable path.

Expected behavior

Codex should request an extended key mode compatible with tmux so Shift+Enter is distinguishable from Enter.

Related

What steps can reproduce the bug?

/

What is the expected behavior?

No response

Additional information

No response

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FAQ

Expected behavior

Codex should request an extended key mode compatible with tmux so Shift+Enter is distinguishable from Enter.

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