iTerm2 input corruption and dropped characters in Codex TUI with CSI-u/key reporting

What happened?

When running Codex TUI in iTerm2, input becomes corrupted or unreliable.

Observed symptoms:

• The composer sometimes receives raw CSI-u / key-reporting fragments such as [105;1:3u, [122;1:3u, [32;1:3u.
• After trying CODEX_TUI_DISABLE_KEYBOARD_ENHANCEMENT=1, the raw escape fragments stop appearing, but typed text is still unreliable: English and Chinese input intermittently drop the first character or drop chunks of text.
• The issue reproduces in a newly created clean iTerm2 profile.
• The same Codex install works normally in macOS Terminal.app.

This looks related to the keyboard enhancement / CSI-u / key reporting path. It is similar to previously reported issues such as #19553, #23820, #28869, and #31420, but in this case the failure happens inside the Codex TUI input box, not only after exiting back to the shell.

Environment

• macOS: 26.3.1
• iTerm2: 3.6.11
• Terminal.app: works normally
• Codex versions tested:
• 0.144.1: reproduces
• 0.143.0: reproduces
• 0.142.5 via npm exec -y --package @openai/codex@0.142.5 -- codex ...: reproduces
• iTerm2 clean profile: reproduces
• Existing long-running Codex session from 2026-07-08 did not show the issue, but newly started sessions do.

Commands / workarounds tried

Plain iTerm2 launch reproduces:

codex --dangerously-bypass-approvals-and-sandbox

Tried forcing Terminal-like environment and removing iTerm variables:

env -u LC_TERMINAL -u LC_TERMINAL_VERSION -u TERM_FEATURES -u TERMINFO_DIRS \
  -u ITERM_SESSION_ID -u ITERM_PROFILE \
  TERM_PROGRAM=Apple_Terminal TERM=xterm-256color \
  LANG=zh_CN.UTF-8 LC_ALL=zh_CN.UTF-8 LC_CTYPE=zh_CN.UTF-8 \
  codex --dangerously-bypass-approvals-and-sandbox

Tried disabling keyboard enhancement:

CODEX_TUI_DISABLE_KEYBOARD_ENHANCEMENT=1 codex --dangerously-bypass-approvals-and-sandbox

Result: escape fragments are reduced/removed, but text input still intermittently drops characters.

Expected behavior

Codex TUI should accept typed input reliably in iTerm2, without raw CSI-u fragments and without dropping characters.

Actual behavior

In iTerm2, newly started Codex sessions intermittently corrupt input or drop characters. Terminal.app works correctly with the same Codex installation.