Photoshop to Lightroom workflow brightens image

Issue summary: Round-tripping a photo through Edit in Photoshop and saving it back with zero edits made results in a visibly brighter image in Lightroom.

Product and version: Lightroom desktop (cloud), version 9.4.1 MAS arm64

Operating system: macOS 26.6.2

Steps to reproduce:

1. Select a photo in Lightroom and choose Edit In > Edit in Photoshop.
2. In Photoshop, make no changes of any kind.
3. Save as, keeping the file as TIFF.
4. Return to Lightroom and compare the reimported version to the original.

Expected result: The image should be visually identical to the original, since no edits were made in Photoshop.

Actual result: The reimported image is noticeably brighter than the original.

Additional testing performed:

• Confirmed Edit in Photoshop settings match on both apps: TIFF, ProPhoto RGB, 16 bits/component. Photoshop Color Management Policy set to Preserve Embedded Profiles, and the file stays 16-bit throughout.
• Tested with resizing (various amounts and resample methods, including Preserve Details 2.0), brightening still occurs.
• Tested with a border-adding Photoshop action, brightening still occurs.
• Isolated to a true null edit (nothing changed at all), brightening still occurs, confirming the issue happens on Lightroom's reimport of the returned file, not from anything done in Photoshop.

EDIT: Exported PNGs seem to match but visually in LR the two images are much different in brightness.