Circumnavigate

Normally a world ends at a hard border, which is a visible wall that breaks immersion. Circumnavigate replaces that edge with wrapping: the world is finite but tiles across the seam, so the terrain, blocks and entities continue on the other side. Chunks are sent to clients with wrapped coordinates, and block destruction, block placement and player positioning follow the same rules, so interaction distance and block collision still work near a boundary.

The wrapping reaches into the systems that usually break at an edge. Entities keep their hitboxes, teleportation, spawning and riding across the wrap, and redstone, block updates, light updates, fluids and pistons are handled on the wrapped grid. Structure and feature generation also respects the wrapped layout, and chunk generation and storage stop at the world's bounds. The settings for wrapping are exposed through a GUI, and the mod works with a vanilla client, so only the server needs it.

Circumnavigate is server-side only and is open source under the GNU Affero General Public License v3.0 only. It is published for Fabric alone, with files for 1.20.4 and 1.21.1, and the latest Fabric file is 0.7 for 1.21.1, released as an alpha. The author notes that stable behavior and future support are not promised yet, so the mod suits servers that accept alpha software.