[BUG] CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN turns off

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?

CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN correctly disables alternate screen on startup but the alternate screen turns back on when switching to the agents view and back to the started session.

This problem also occurs sometimes when running claude code in a tmux instance and you detach and reattach to it.

What Should Happen?

When switching to the agents view and back into the original session, the TUI should be rendered using the CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN approach the sessions started as.

Error Messages/Logs

Steps to Reproduce

1. Start claude with CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=1 claude
2. Press your left arrow key to switch to agents view.
3. Press enter to switch back to the session you started.
4. The TUI then renders as though CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=0. Have claude print some text and you can see the difference when you scroll up.

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.207 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Terminal: kitty