PSB issue in Lightroom and Photoshop

I'm here to report the exact same issues.

I view my photos through a Lightroom catalog. Then from there, decide to work on them in Photoshop.

Because of large resolution and complex product images, I've had to start working with PSB files now (previously used only TIFF or PSDs). The nature of PSB files is that they are large, I usually work with 8-15 GB files. I've come to the frustrating realization that Lightroom cannot handle these files without corrupting them. I don't even use any develop settings on these files, merely rating them will corrupt them. Lightroom will give a warning of an issue, then trying to open the files in Photoshop will give a corrupted error. This is absolutely absurd, ridiculous and unacceptable. If Lightroom cannot handle these files, or if writing metadata to them will corrupt them, then they should either not be able to be imported into Lightroom, or be seen as "View Only".

Thanks for the insight - appreciated.  I'll take on your thoughts about the workflow and precautions.  None of the below is aimed at you - just stating this for any Adobe devs reading.

Without detailed technical knowledge of how Adobe handles these flattend composites, there's no way of the end user knowing that it won't work unless they try it.  I don't have that knowledge, but I have worked in this way without issue for many years with TIFF and PSD files, and more recently PSBs.  

If LR can't work in Develop with Adobe's own proprietery file format without the risk of bricking the file, this functionality should either be disabled (no Develop module adjustments available) and / or it should be mentioned in the Adobe documentation.  Since neither of these is true, it's a bug.  And if this were a financial service it'd be one that comes with a bug bounty since the risk is bricking the file beyond any obvious revovery, which in my case could have been a threat to revenue but for a very understanding client. If there was a substantial media buy deadline (as is often the case), I would have been in serious trouble.

The fact that Adobe gives no warning and places no limitation on you doing this (the PSD compatibility notes suggest "working with" files in LR, which to me would suggest all modules without exclusion), means that this bug is only found by users after the file is bricked. With compositing, smart object use and 50MP+ source files nows commonplace, this will become a bigger issue in the future.

There may well be a bug here - but repeated roundtrip editing as described here is generally asking for trouble.

Lightroom does not support layers. It cannot read them and cannot do anything with them. What Lightroom works with is a flattened composite inserted in the file by Photoshop.

In other words, edits in one application are not readable in the other. If you follow the implications of this, you can see that going back and forth is a recipe for confusion and messy files. There's no way to retrace edits in either.

You can do this as long as you're fully aware of what happens and take your precautions. But generally, I'd recommend keeping this a one-way workflow.

For anyone reading this post describes the same problem and has a fix that on initial testing has worked for me:

https://community.adobe.com/t5/lightroom-classic-discussions/lightroom-messing-up-psb-files-after-importing/m-p/11961583#M228811

If anyone from Adobe is reading there's a bug there for sure.

Seems like I've been able to reproduce this with a copy I've made.

1. Open PSB in PS, do some work, save

2. Back in LR, make some adjustments in Develop module

3. Export to JPEG is fine

4. Spot an issue with image (e.g. a mask), go back to LR, Edit in->PS, edit original

5. Make edits in PS, save

6. Back in LR, the "Saving XMP for 1 photo" text is in the top left (see attached), and image has an exclamation mark in the top corner of it's thumbnail

7. Clicking the exclamation mark gives the attached error.

So it seems the issue is with XMP being saved (or not) to a PSB, the file is then unreadable by PS or LR.