According to Gemini:

A modder named iamcxv7 developed a proof-of-concept mod that allows Hytale and Minecraft players to interact in the same world.

How it Works: The mod uses "Packet Trickery" to translate data between the two games.

Server Host: A Minecraft server runs within the Hytale Java Virtual Machine (JVM).

Translation: The mod takes snapshots of the Hytale world, reconstructs them using Minecraft's coordinate system, and sends this data to the Minecraft client via packets.

Synchronization: Player movements, block placements, animations, time of day, and text chat are synchronized across both games.