What version of Codex CLI is running?

codex-cli 0.120.0

What subscription do you have?

Pro

Which model were you using?

gpt-5.4

What platform is your computer?

Linux 6.8.0-107-generic x86_64 x86_64

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

Kitty

What issue are you seeing?

Title: Codex TUI over-deletes on Backspace in Kitty on Ubuntu/X11 despite correct raw keyboard events

Environment:

• Codex CLI: 0.120.0
• OS: Ubuntu Linux
• Session: X11
• Terminal: Kitty 0.32.2
• TERM seen by Codex: xterm-256color
• Locale: en_US.UTF-8 / LC_ALL=en_US.UTF-8

Problem:

While typing in the interactive Codex TUI prompt, Backspace sometimes over-deletes. Example:

1. Type hhhh
2. Press Backspace twice
3. Instead of deleting 2 characters, Codex often deletes all 4

I also see variants where delete does not stop immediately on key release.

Expected:

• Two Backspace taps delete exactly two characters

Actual:

• Two Backspace taps can delete more than two characters, sometimes the whole input

Important diagnosis:

I ruled out the keyboard, OS repeat, and Kitty input layers.

What I tested:

• Raw keyboard events from the device were correct
• XI2 raw X input events were correct
• For the failing pattern, the system saw exactly:
  • 4 h key press/release pairs
  • 2 Backspace key press/release pairs
• Backspace key release arrived promptly
• Kitty config had no unusual input settings
• Issue persisted after stopping Synergy
• Issue persisted after reducing keyboard repeat from:
  • delay 500 ms / rate 33/sec
  • to delay 660 ms / rate 22/sec
• Issue persisted when running Codex with:
  • --no-alt-screen
  • Kitty-specific env stripped (KITTY_*, TERMINFO)
  • TERM=xterm-256color

Why I believe this is a Codex TUI/input bug:

The lower layers report correct input, but Codex’s prompt editor still over-deletes. That suggests the bug is in Codex’s TUI/editor state handling or redraw/input processing, not in the keyboard, GNOME/X11, or Kitty.

Extra context:

• synergy.service was running initially and was stopped for testing; stopping it did not fix the issue
• Kitty version: kitty 0.32.2 created by Kovid Goyal
• Codex version: codex-cli 0.120.0

If useful, I can provide:

• xinput test-xi2 capture showing the exact key press/release sequence
• system keyboard repeat settings
• Kitty environment details

What steps can reproduce the bug?

Uploaded thread: 019d8c60-0d82-7b43-a538-cffd2fe3c96d

What is the expected behavior?

Type "hhhh" at the prompt, then press Bksp twice. Observe that all four "h" characters are deleted despite only pressing Bksp twice.

Additional information

No response