Blank lines render above input when typing after Ctrl+Enter newline

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?

When creating a multiline input using Ctrl+Enter (or backslash + Enter), typing the first few characters on the new line causes blank lines to appear above the input area.

The blank lines appear progressively as you type the first 3-5 characters, then disappear/stabilise. This is a cosmetic rendering issue with the Ink TUI framework.

What Should Happen?

Typing on a new line after Ctrl+Enter should not cause any visual artefacts. The input area should remain stable without blank lines appearing above it.

Error Messages/Logs

Steps to Reproduce

1. Start Claude Code in any terminal
2. Begin typing a message in the input area
3. Press Ctrl+Enter (or type \ then Enter) to create a new line
4. Start typing on the new line
5. Observe: blank lines appear above the input area as you type the first few characters
6. Continue typing - the blank lines disappear after ~5 characters

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.11

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

This appears to be a rendering quirk in the Ink TUI framework used by Claude Code. The issue is purely cosmetic and self-corrects after typing a few characters — it doesn't affect functionality.

Tested with PowerShell 7.5.4 and Windows Terminal with shell integration enabled.