Chunk Keep

You travel on a server (walk, fly, ride) just past its view distance, then head back. The server has already told your game to forget the chunks behind you, so the place you are returning to is empty sky until the server sends it all again.

Where: in the world, behind you. Type /chunkkeep in chat to see what it is doing.

What it does: when the server tells your game to forget a chunk, Chunk Keep keeps it on your side instead, as long as it is within 3 chunks beyond your view distance (the smaller of the server's view distance and your own render distance). extra_chunks is capped at 3, matched to the spare room in the game's own client chunk cache.

• Head back and the kept ground is already there; when the server sends the chunk again, the fresh copy replaces it.
• Kept chunks are let go when you move further away, after a time limit (max_seconds, default 600), when the game's memory use is high (memory_limit_percent, default 85; farthest first, and nothing new is kept until it drops), when you switch it off, when you change dimension, or when the server changes its view distance. The time and memory limits never let go of a kept chunk that is back inside your view (it is about to be sent again). Letting go runs the game's own "forget chunk" handling, unchanged.
• /chunkkeep shows how many chunks are kept, how many were still there when you came back, and why chunks were let go. /chunkkeep on / /chunkkeep off switches it and saves the setting.
• Client-side only: install it on your own game; nothing is needed on the server, and it sends nothing to the server.

Result: in the automated test against a real test server (view distance 4), 6 chunks away from home the server had stopped tracking the home chunk and the game still had it (it never disappeared on the way out), and 24 kept chunks were still there when the server sent them again. With the test server stopped from sending any chunk data (to imitate a busy server), jumping 6 chunks back home (teleport) showed the ground and the gold tower with the mod, and only sky without it (picture 1). With your render distance at 2 on that server, nothing was kept farther than 5 chunks.