Created a Custom Container (FuelChest) that when I'm exiting the world and coming back, cannot be opened, but if I brake the block, it's content dropped.

1. Not an api thing
2. Make sure you save the contents to the tag in the read/write nbt methods to save the inventory

I thought it's API because nobody could help me. See? I got the read / write! the problem is I can't open!

Oh it can't be opened :concern: use break points to see it trying to open

The onOpen() method not even being called

You should register your screen handler in your mod main entrypoint. Call this to register your screen handler

Marking this as closed, please ask on the #mod-dev channels on our official Discord server if you have further questions.