[BUG] VSCode Claude UI: Multi-line Input Lost When Pressing Up Arrow (Triggers Prompt History)

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?

Hello,

My name is Donghee Kim from Korea, and I am a MAX X20 user.

When using the Claude extension UI in VSCode, I often input long prompts with multiple lines.
However, when I try to scroll up within the input field to review earlier parts of the text,
the input unexpectedly switches to a previous prompt.

Although I can return to the latest prompt using the down arrow key,
the text I was just writing is completely lost, which is quite frustrating.

It seems that the input field is treating the up/down arrow keys as prompt history navigation,
even when the user is simply trying to move the cursor within a multi-line input.

I would greatly appreciate it if this behavior could be improved,
so that cursor movement within the input field does not trigger prompt history navigation.

Thank you for your time.

What Should Happen?

When typing a multi-line prompt in the VSCode Claude extension input field, the user should be able to move the cursor freely with the arrow keys without triggering prompt history navigation.

Pressing the up or down arrow keys should only move the cursor within the current input while editing. The text being written should remain intact and should not be replaced or lost.

Error Messages/Logs

No explicit error message is shown.

This is a UI issue where pressing the arrow keys during multi-line editing can trigger prompt history navigation and cause the current unsent input to be lost.

Steps to Reproduce

1. Open VSCode with the Claude extension installed
2. Go to the Claude input panel (extension UI)
3. Start typing a long prompt with multiple lines (use line breaks)
4. Move the cursor upward using the up arrow key to review earlier text
5. Observe that the input switches to a previous prompt from history
6. Press the down arrow key to return
7. The text that was being written is lost

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

opus 4.6

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_