Regression: Shift+Enter / Alt+Enter no longer insert newline in TUI prompt

What version of Codex CLI is running?

codex-cli 0.128.0

Which model were you using?

Not model-specific; this is a TUI input handling issue.

What platform is your computer?

macOS / Darwin 25.4.0 arm64

Terminal environment:

• TERM_PROGRAM=vscode
• TERM=xterm-256color

What steps can reproduce the bug?

1. Open Codex CLI in the VS Code integrated terminal.
2. Type a multi-line prompt draft.
3. Press Shift+Enter or Alt+Enter to insert a newline.

What is the expected behavior?

Shift+Enter and/or Alt+Enter should insert a newline in the prompt, matching common chat/editor behavior.

At minimum, modified Enter key sequences should not submit the prompt accidentally.

What do you see instead?

The prompt is submitted instead of inserting a newline.

The current visible workaround is Ctrl+J, but this is easy to miss and differs from the expected behavior in most chat/editor UIs.

Additional information

This looks related to existing TUI input regressions / requests:

• #4218 reported Shift+Enter submitting instead of inserting a line break on macOS.
• #4401 reported modified Enter escape sequence handling issues on Windows.
• #12129 tracks a broader request to make multiline input behavior configurable.

This report is for the current CLI version 0.128.0 and specifically includes both Shift+Enter and Alt+Enter in the VS Code integrated terminal on macOS.