Compatibility contract

FeatherMC keeps these the same as Paper on purpose, so tools and plugins built for Paper keep working:

Surface	On FeatherMC
Java packages	io.papermc.paper, org.bukkit, com.destroystokyo.paper
Brand ID	papermc:paper
Brand name	FeatherMC
Persistent data / NBT keys	Paper’s keys, unchanged
Config files	config/paper-global.yml, config/paper-world-defaults.yml, per-world paper-world.yml
Commands and CLI flags	/paper and Paper’s startup flags

What players can observe is also held constant. Redstone timing, mob behaviour, drops, physics and world generation must match Paper. The only exceptions are the opt-in guards documented in the config reference, and they are off unless an admin turns them on.