Genshin : Thousand Stars logo. ( By Fireflyleaks) read description too for context plus clarification before commenting.

It is actually true.

The launcher code actually has some localization text mentioning the UGC mode (seehttps://webstatic .hoyoverse.com/admin/mi18n /plat_os/m20231225hy87cnfo5c /m20231225hy87cnfo5c-en-us.json):

"launch_menu_wpf": "Miliastra Sandbox"

"wpf_settting_tip": "{wpf} must be used in-game"

"wpf_settting_auto_update": "{wpf} will be automatically updated when there is a new version available"

The client does seem to have a "wpf_icon_en-us.png" not present until now.

Testing has begun.