Describe the Bug

When using blocks that contain an array field, copying and pasting block content in the admin editor temporarily duplicates the array items in the UI.

Additional Notes

• This issue appears only in the admin UI immediately after pasting.
• After saving the document, the duplicated items disappear and the stored data is correct.
• Therefore the issue seems to be a UI/state issue rather than a data persistence problem.

Link to the code that reproduces this issue

https://github.com/LeonGatt/payload/tree/issue/copy-and-paste-of-block

Reproduction Steps

Steps to Reproduce

• Create a block that contains an array field
• Add several items to the array inside the block
• Copy the block content
• Create a new block of the same type
• Paste the copied content into the new block

Expected Behavior
The pasted block should contain the same number of array items as the original block.

Actual Behavior
Immediately after pasting, the array items appear duplicated (twice the original count) in the editor UI.

Example:
Original array items: 3
After paste in new block: 6

Thanks to @TimothyBucka and @marek-fiala for reporting 🙏🏻

Which area(s) are affected?

area: ui

Environment Info

Binaries:
  Node: 22.14.0
  npm: 10.9.2
  Yarn: N/A
  pnpm: 10.28.1
Relevant Packages:

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.2.0: Tue Nov 18 21:09:45 PST 2025; root:xnu-12377.61.12~1/RELEASE_ARM64_T6030
  Available memory (MB): 18432
  Available CPU cores: 11