TUI: Initial lines of streamed output disappear during rendering (scrollback inaccessible)

What version of Codex CLI is running?

codex-cli 0.98.0

What subscription do you have?

Pro

Which model were you using?

gpt-5.3-codex

What platform is your computer?

Darwin 25.2.0 arm64 arm

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

VSCode

What issue are you seeing?

During response streaming, the first portion of the output vanishes as subsequent lines are rendered. The missing lines are not pushed out of view—they're completely absent from the scrollback buffer and cannot be recovered by scrolling up. The number of lost lines varies depending on response length and viewport size.

Observable behavior: You can watch the first few lines vanish as streaming progresses—they get pushed upward and disappear as if being written to a buffer that's not being rendered.

What steps can reproduce the bug?

1. Start Codex CLI in VSCode terminal
2. Ask any question that produces a multi-line response
3. As the response streams in, the beginning lines disappear above the viewport
4. The lost content is not recoverable with scrolling

What is the expected behavior?

_No response_

Additional information

_No response_