I've pressed the "Update" button in the Mac App Store to install a new version of Xcode.
The Mac App Store itself shows no visible download progress or error messages, but the circle is almost complete:
Hovering on Launchpad's dock icon shows the ongoing Mac App Store download progress. Now that the download has completed it is showing "Launchpad Installing".
Launchpad Downloading - 100.0 MB of 12.39 GB
It's been stuck in this state for quite some time.
I'm currently using Xcode, which is open. I have had various Xcode betas installed, in addition to the Mac App Store version. The latest Xcode RC was simply titled "Xcode.app" and overwrote the version from the Mac App Store in my Applications directory.
As I'm typing this, the "Installing" seems to have finally failed. It has begun downloading the entire 12.39 GB update again.
Why is the Mac App Store download stuck at "Installing"? How can I get this update to actually install?