[BUG] Scrollback completely broken on 1.0.119

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

I can't scrollback to previous pages:

<img width="1699" height="708" alt="Image" src="https://github.com/user-attachments/assets/cbe46a61-209e-4b3c-96b8-d30a3b5d2523" />

This image shows tmux scrollback buffer as [0/0] and I can't scroll back to read previous parts of the message

What Should Happen?

Terminal should scroll to the previous parts of the message

Error Messages/Logs

Steps to Reproduce

1. Run any command that spans more than one page
2. Try to scrollback

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

I reverted to 1.0.88 and it works again

Claude Code Version

1.0.119

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

Also tested on WezTerm and Ghostty, Ghostty lets you scroll back if you use the command palette and use Page Up (Cmd+Up), but scroll wheel on the mouse doesn't work.