Interesting, mine never reaches past the label "Preparing to upload". FWIW, this is the first build I have tried to upload with Xcode 26.4. This is a new app but the previous few builds were all uploaded with 26.3. If it's not working by EOD tomorrow, Monday, Ill file a FB request.

It's happening after selecting "App Store Connect" and clicking the "Distribute" button in "Select a method for distribution". It's an app that has not yet been released to the App Store, but has already had a handful of builds uploaded to App Store Connect and distributed with TestFlight w/o issue. The build number is correct. Recreating the archive does not appear to help.

Sadly doesn't change anything. I don't know if there's any remaining docs online from Apple about animating constraints, but this Stack Overflow answer at least references the WWDC Session where the process was discussed.