Old characters not cleared from screen when scrolling

What version of Codex is running?

codex-cli 0.30.0

Which model were you using?

gpt-5

What platform is your computer?

Darwin 24.6.0 arm64 arm

What steps can reproduce the bug?

Give codex a task, let it think, then use ctrl-T to bring up the transcript. Then use up-arrow to scroll back through the transcript.

What is the expected behavior?

Nothing abnormal.

What do you see instead?

When you scroll, a character is only erased when it's overwritten, which means old characters pile up during scrollback, ending up in a garbled-looking text display.

<img width="460" height="344" alt="Image" src="https://github.com/user-attachments/assets/314564d3-6ff1-4dea-8b2a-66143252bbf3" />

<img width="367" height="294" alt="Image" src="https://github.com/user-attachments/assets/78ce06e0-182a-4b2b-952e-c654f04c7385" />

Additional information

Terminal is macOS Terminal.app