[BUG] Desktop app on Mac. UI Layout Jitter / Ghosting on Sidebar Interaction

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 interacting with the sidebar resize handle or hovering near the sidebar toggle in the Claude Desktop app (Mac), the main content area and the sidebar itself undergo rapid, erratic width changes ("jumping"). This happens even without a mouse click, triggered simply by hover states or slight movements near the boundary.

The UI enters a "jitter" loop where elements flash and jump horizontally. The "Click to collapse / Drag to resize" tooltip may appear and disappear rapidly, and the main chat window fails to maintain a stable width.

The video was added as an attachment to this report: https://youtu.be/w7rBMT3fi5E

What Should Happen?

The sidebar should resize smoothly without flickering, and the main content should fluidly adapt to the new container size.

Steps to Reproduce

• Open Claude Desktop on macOS.
• Hover the cursor over the divider between the sidebar and the main chat area.
• Attempt to resize the sidebar or simply move the cursor vertically along the resize handle.
• Observe the sidebar and main window content snapping between different widths.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.84

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)