Existing AI Sky Masks are deleted when applying another Develop Preset containing an AI Sky Mask

Bug Report: Existing AI Sky Masks are deleted when applying another Develop Preset containing an AI Sky Mask

Product: Adobe Lightroom Classic
Version: 15.6
Operating System: Windows 10

1. Description of the problem

I have discovered a reproducible issue when creating and applying Develop Presets containing AI-based Sky masks.

When I apply a Develop Preset containing an AI Sky mask to an image that already has an AI Sky mask from another preset, the previously existing mask is deleted and replaced by the mask from the newly applied preset.

This happens even when both presets were created independently and contain only one selected mask.

The problem also occurs with newly created presets. Therefore, it does not appear to be limited to older or corrupted preset files.

2. Steps to reproduce

1. Open an image in Lightroom Classic.
2. Create an AI Sky mask and adjust its settings, for example Exposure, Highlights, Shadows or Whites.
3. Save these settings as Develop Preset A, selecting only Masking.
4. Modify the settings of the same mask, for example Highlights and Shadows.
5. Save the modified settings as a separate Develop Preset B, again selecting only Masking.
6. Apply Preset A to an image.
7. Apply Preset B to the same image.

3. Actual result

After applying Preset B, the previously existing AI Sky mask from Preset A disappears from the Masking panel.

Only the mask from Preset B remains.

4. Expected result

Applying a second Develop Preset containing an AI Sky mask should add another independent mask without deleting previously existing masks.

Both masks should remain available in the Masking panel.

5. Additional tests and findings

I performed several tests to identify the cause:

• The issue occurs with both older and newly created presets.
• It also occurs after updating Lightroom Classic to the latest available version at the time of testing.
• Manually created Brush masks are not affected in the same way.
• Applying two presets containing AI Sky masks with different adjustment values can reproduce the problem.
• The issue appears to be related specifically to AI Sky masks stored in Develop Presets.

6. Technical finding – XMP preset files

I compared the XMP files of two different presets and discovered that they contained identical internal values for:

• MaskSyncID
• CorrectionSyncID

After manually changing these identifiers to unique values in the XMP files, both presets could be applied consecutively without deleting the previously existing masks.

This suggests that Lightroom Classic may not be generating or handling unique mask identifiers correctly when creating or applying Develop Presets containing AI masks.

7. Request

Please investigate the handling and generation of internal mask identifiers when creating and applying Develop Presets containing AI-based masks.

In particular, please check whether duplicate MaskSyncID and CorrectionSyncID values can cause existing masks to be overwritten or deleted.

I can provide the original and modified XMP preset files as well as further test results if required.