Pull Request

Description

The "+" (Add Assistant) button at the end of the assistant label row flickers rapidly when the mouse hovers over it, making it completely unclickable.

Root cause: The button expands from 28px to up to 320px on hover via max-width transition. When the button sits near the end of a flex-wrap row, the expansion causes it to wrap to the next line → mouse leaves → button shrinks back → re-enters the row → hover triggers again → infinite loop.

Fix: Remove the hover expand animation entirely. The button is now a static circular "+" icon (28×28) with only a background color change on hover. This eliminates the reflow issue at its source and keeps the UI simple.

Related Issues

• Closes [Bug]: "+" button at the end of Label row flickers and is unclickable #1358

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Testing

• Tested on macOS
• Tested on Windows
• Tested on Linux
• My code follows the project's code style guidelines
• I have performed a self-review of my own code
• My changes generate no new warnings or errors

Screenshots

Before (Bug)

Default state (inline)	Hover state (wrapped to next line)

After (Fixed)

Static "+" button, no expand animation on hover.

Additional Context

The bug is triggered when the "+" button is positioned near the end of a flex-wrap row with just enough space for the collapsed state (28px) but not for the expanded state. Resizing the window to make the button sit at the row boundary reliably reproduces the issue.