Direct answer

Leaf can move or remove tuning options between releases. Copying a historic leaf-global.yml over a newer generated one may silently preserve irrelevant keys or omit new safety defaults.

Recommended procedure

  1. Back up the stopped world, player data, plugins and all configuration files. Record old Leaf build and JVM release.
  2. Check the official download channel, release notes and Java requirement for the intended build.
  3. Start the new JAR in a cloned test directory using a fresh generated config; compare settings before moving over only necessary customizations.

What to change

  1. Test gameplay, NPCs, navigation, farms, player saving and any async features that you previously changed.
  2. Do not migrate an old tuning block blindly; read matching documentation and keep the original JAR plus backup available.

How to verify the result

Restart twice on staging, verify inventories and persistence, inspect logs and return to old build using the original backup if behavior changes.

Version and compatibility notes

Leaf’s online global-config reference currently describes 1.21.1; a newer 26.x config must be read from that branch’s generated files or release documentation. Avoid experimental updates for production unless knowingly testing them.

Official references

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