Migration Notes

Loader and Java changes

Area	1.20.1	1.21.1
Loader stack	Forge	NeoForge
Java target	17	21
Mod metadata	mods.toml	generated neoforge.mods.toml from templates

Public API changes

New in 1.21.1

• MyotusAPI.isInitialized()
• static convenience accessors like MyotusAPI.modRegistrar()
• fluent aliases on registrar interfaces
• ITerminalUpgradeCard

Still conceptually shared

• config-tab registration
• optional integration registration
• runtime integration queries

User-facing differences

Removed or changed

• activeTabSorting only exists in the inspected 1.20.1 config spec

Added

• 1.21.1 adds a toggle key for the sub side panel
• 1.21.1 adds upgrade-card slot and storage infrastructure

Build and publishing differences

1.20.1

• ForgeGradle mod build
• geared toward direct mod development

1.21.1

• NeoForge moddev toolchain
• Maven publishing support
• API jar generation
• local repository publishing path

Migration strategy

1. Move loader and Java assumptions first.
2. Keep shared API usage in the registrar/runtime-manager layer where possible.
3. Treat upgrade-card functionality as 1.21.1-only unless you backport it yourself.
4. Re-check config and keybind docs instead of assuming parity between lines.