[BUG] Invisible scroll list

Preflight Checklist

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

What's Wrong?

Title: Scrollbar thumb becomes nearly invisible near the bottom of the chat panel (VS Code extension)

Environment:

• OS: Windows 11
• Editor: VS Code
• Claude Code extension (VS Code integration)

Description:
The scrollbar thumb in the Claude Code chat panel is clearly visible (a solid, appropriately-sized bar) when scrolled to the middle/top of the conversation. When scrolled near the bottom of the panel, the same thumb shrinks to a tiny, barely-visible sliver — a size change, not just a color/contrast issue.

Steps to reproduce:

1. Open the Claude Code panel in VS Code with a long conversation (enough content to scroll).
2. Scroll to the middle of the conversation — note the scrollbar thumb's size/visibility.
3. Scroll to the very bottom of the panel.
4. Compare — the thumb becomes much smaller/fainter near the bottom.

Expected: the scrollbar thumb should stay a consistent, visible size regardless of scroll position (matching standard VS Code scrollbar behavior).

Actual: thumb shrinks dramatically near the bottom, making it very hard to see or grab.

Additional notes:

• Tried customizing workbench.colorCustomizations (scrollbarSlider.background/hoverBackground/activeBackground, scrollbar.shadow) in user settings.json — no effect on this specific panel, suggesting the chat panel renders its own scrollbar (e.g. inside a webview) independent of the standard VS Code theme tokens.
• Screenshots attached showing the size difference between mid-scroll and bottom-of-scroll positions.

What Should Happen?

Should be visible all the way up and down

Error Messages/Logs

Steps to Reproduce

Scroll from top to bottom

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

No response

Claude Code Version

2.1.278 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Start by reproducing the issue in the Claude Code panel in VS Code with a long conversation, comparing the scrollbar thumb in the middle and at the bottom. Inspect the VS Code panel or webview scrollbar implementation; done means the thumb remains consistently visible and usable throughout scrolling, including at the bottom.