Controls of components inside R3F `Canvas` not rendering in `StrictMode`

[dammafra]

Description
When in StrictMode, controls added from components inside a @react-three/fiber Canvas do not display as expected.
This behavior disappears when StrictMode is removed.

Reproduce
StackBlitz Example

Expected behavior
Controls should display correctly even when StrictMode is enabled.

Environment

• react: 19.1.1
• @react-three/fiber: 9.3.0
• leva: 0.10.0
• Browser: Chrome 139.0.7258.67
• OS: macOS 15.6

[DennisSmolek]

Seems like something with the css calculation in the ui. If you collapse/expand the ui corrects it. The parent to the inputs shows a height value, changing at all resolves.