Threadcore

Threadcore

Vanilla Minecraft ticks your entire server on a single thread. One busy farm, one mob swarm, one player exploring — and everything else waits behind it.

Threadcore divides each world into regions and ticks them in parallel, on a pool of worker threads. Entities, block entities and scheduled ticks in different regions run at the same time. Everything that has to be single-threaded still is: region threads never write a block directly, never spawn or remove an entity directly, and never touch another region's chunks. Those operations are deferred to the main thread and replayed in order.

Install it on the server only. Your players install nothing and need no client mod.

How it keeps your world intact

Parallelising a game loop that was never designed for it is the easy part. Not corrupting anything is the hard part, and it is where nearly all of the work went:

• Thread domains. Every operation is tagged MAIN, REGION or ASYNC, and a guard asserts that whatever is running is allowed to be where it is. In strict mode a violation is loud, not silent.
• Deferral queues for every cross-region mutation: block changes, entity spawn/removal/damage, scheduled ticks, lighting, neighbour updates, path recalculation.
• Snapshot reads. Off-thread readers get a frozen view per tick rather than a racing one.
• Probation. An entity type that misbehaves is demoted and stops being offloaded.
• An audit layer that ledgers items and XP and reports any that do not balance.
• Mod compatibility refusal. Where another mod's internals make offloading unsafe, Threadcore refuses to arm rather than hoping. Lithium is detected and specific hazards are declined.

Honest status — read this before installing

This is an alpha, and the version string says so.

• 1.20.1 has been running a real production server since 2026-09-16. That is where the confidence comes from.
• It is not a drop-in speedup for every server. The gain depends on how much of your tick is entities and block entities spread across regions. A server bottlenecked on chunk generation, on one enormous farm in one chunk, or on a single mod's main-thread work will see little.
• Back up your world first. Not a formality — this moves the tick loop.
• Offload is off for modded entity types until they pass probation, deliberately. A heavy modpack will start conservative.
• Every risky behaviour has an off switch, and the defaults are the safe ones.

Reporting problems

Please include: your Minecraft and Fabric Loader versions, the full mod list, and the server log. If you can reproduce it, say whether it still happens with -Dthreadcore.offload=false — that single flag turns the parallel tick off and makes Threadcore a no-op, which immediately tells us whether Threadcore is involved at all.