[BUG] Claude Code v2.1.109 duplicates previously rendered content in the terminal UI

Bug description

Claude Code v2.1.109 appears to re-render old screen content repeatedly in the terminal UI.

The issue is not the model text itself — the problem is that previously rendered blocks are duplicated and appended again, causing the same welcome screen, previous conversation content, and slash-command output to appear multiple times.

From the screenshot, the duplicated content includes:

• the welcome screen rendered multiple times
• earlier conversation messages shown again
• slash-command interactions like /effort, /doctor, and /clear appearing to trigger extra redraws that append old content

Expected behavior

The terminal UI should redraw cleanly and only show the current screen state, without duplicating previously rendered content.

Steps to reproduce

1. Update Claude Code to v2.1.109
2. Launch claude
3. Enter hello
4. Ask 你是什么模型？
5. Type / to open the slash-command menu
6. Run /effort
7. Run /doctor
8. Run /clear
9. Observe that previously rendered UI blocks are shown again instead of the screen being redrawn cleanly

Claude Code version

2.1.109 (Claude Code)

Environment

• OS: Linux (CentOS-based)
• User: root
• Working directory shown in UI: /root

Additional notes

This looks like a terminal UI redraw / screen buffer / rendering issue rather than a content-generation issue.

I have a screenshot showing the duplicated rendering pattern, but did not attach it through the CLI issue creation flow.