Admin UI blur rendering bug on iOS/iPadOS caused by ::after backdrop layer

Describe the Bug.

On iOS and iPadOS devices, when editing a document that contains a relationship field, opening the relationship drawer/modal causes parts of the Admin UI to appear blurred incorrectly.

The blur effect does not persist after the drawer is closed, but while the drawer is open, the blur layer renders in the wrong visual stacking order, covering UI regions it should not.

This issue does not occur on macOS Safari or desktop browsers.

The currently identified pseudo-elements are:

.doc-controls::after
.fixed-toolbar::after

This issue does not occur on macOS Safari or desktop Chrome/Firefox.

So far, these are the only pseudo-elements we have observed causing this issue, but other pseudo-elements using backdrop-filter may exhibit the same behavior.

iOS 18

iPadOS 26

Reproduction Steps

1. Use an iPad or iPhone
2. Open Payload Admin
3. Open a document that includes a relationship field
4. Open the relationship drawer or popup
5. Observe the blur overlay affecting unintended UI areas

Environment Info

Payload: tested in 3.69.0 and 3.74.0
Next: 15.5.9
Node: v24