Code Layer fails to render on Figma Sites canvas but works in Full Preview

I’m experiencing an issue with Code Layers in Figma Sites.

A Code Layer fails to render on the canvas and shows the error message:

“Code Layer is not working.”

However, the exact same Code Layer renders correctly in Full Preview.

I first noticed this with a custom React Code Layer, so I simplified the code step by step to rule out implementation issues. The problem still occurs even with a newly created Code Layer containing only:

export default function Test() {
  return <div>Code Layer Test</div>;
}

Reproduction steps:

1. Create a new Code Layer in Figma Sites.
2. Replace its code with the minimal example above.
3. Return to the canvas.
4. The Code Layer displays an error instead of its content.
5. Open Full Preview.
6. The same Code Layer renders correctly.

I also tested this with a completely new Code Layer, so the issue does not appear to be related to a specific component implementation.

Expected behavior:
The Code Layer should render on the Figma Sites canvas as well as in Full Preview.

Actual behavior:
The Code Layer fails on the canvas, while Full Preview works normally.

This makes it difficult to work with Code Layers while editing a page because their actual content cannot be seen on the canvas.

Please let me know if there are any known limitations, workarounds, or additional debugging information I can provide.