Description of the problem including expected versus actual behavior:
I tried to build a hostile mob farm but the block light level inside the enclosed box I created registered as 13.

Mod and Forge Versions

Mod Version: 4.0.0 beta 2
Forge version: 1.16.5 - 36.1.16
Java Version: 1.8.0_292 64bit

Steps to reproduce:

1. Create Compact Machine (I made 13x13x13)
2. Build dark room inside compact machine
3. Check block light level inside dark room (for me it was 13)

Not sure if this is a byproduct of the biome type being void or not, but that was about the only thing I could think of.

Closed by updating the default biome in commit 98c4b08 to minecraft:plains. Currently available in the nightly builds for testing if one is willing to use unstable builds.

Just to confirm, I've just tested this with a new compact machine using nightly-0b2728d and hostile mobs are spawning successfully for me.

What happened to inheriting the biome of where the box is placed? Or was that a myth? :D

Just in case anybody stumbles upon this same issue like I just did - Beta 3 seems to be 1.18 only. To solve this for my 1.16.5 Oceanblock playthrough I installed MCEdit and simply changed the biome inside my compact machine to deep warm ocean (because that's the biome I placed my compact machine in the overworld) and now mobs are spawning as they should

I am also having this problem with spawner rooms. I created the largest size compact machine, built a room within it and placed a spawner in the middle of the room. Mobs do not spawn even from the spawner.

compactmachines-4.0.0-beta.2
forge 1.16.5 36.1.30
java 1.8.0 291 64 bit

Updated information

Light levels are working. They are zero. However, spawner not working.