What is an OSB ISO? What’s the difference of an OSB and a “normal ISO image"

 Actually, what happens right now during deploying KVM Guest via Fedora-Workstation-Live-osb-40-20240301.n.0.x86_64.iso .

At the time of writing I clearly saw Anaconda Web UI behavior during installation via ISO image pointed above. However, it appears impossible to customize virtual disk layout. Every time EFI (/boot/efi, fat32) partition, BOOT partition (/boot, ext4), ROOT partition (btrfs,“/”) are supposed to be created, installer just configures BTRFS ROOT (“/”) partition in accordance with space proposed during virt-manager configuration phase.
If I select ordinary ISO image ( Fedora-Workstation-Live-x86_64-40-20240301.n.0.iso ) everything works fine in traditional manner , say utilizing pretty nice “Blivet GUI”.

See original thread at https://discussion.fedoraproject.org/t/what-is-an-osb-iso-whats-the-difference-of-an-osb-and-a-normal-iso/105617/3

Link been used

https://opencolo.mm.fcix.net/fedora/linux/development/40/Workstation/x86_64/iso/Fedora-Workstation-Live-osb-40-20240301.n.0.x86_64.iso

See also the list of current nightly builds

https://opencolo.mm.fcix.net/fedora/linux/development/40/Workstation/x86_64/iso/

I am also aware of article Fedora Workstation's Anaconda Web UI Installer Delayed To Fedora 41   which explains the reason for mentioned delay and provides some light on why OSB image behaves the way described earlier .