The game crashes on startup, and this is the only code I have in the startup_scripts folder

onEvent('fluid.registry', event => {
    event.create('hyper_gro').textureThin(0xd086f0).bucketColor(0xd086f0).displayName('Hyper-Gro')
})

crash-2021-12-09_13.23.11-client.txt

I tried the same code on forge 1.18 and everything works fine

Custom fluids are not supported on Fabric as, last time I checked, they lack an API for fluid attributes.

This has been implemented now!