CatalystFX

Startup on modded clients can wait on optional tasks before the game responds. CatalystFX defers non-essential client-side DataFixerUpper optimization onto a controlled background thread, so the initial client boot does not stall on those tasks. It does not disable systems that gameplay depends on, and rendering, world loading, the resource system and gameplay behavior are left intact.

The mod keeps its changes deliberately small: a handful of startup optimizations scoped to the client launch path, with no broad switching off of subsystems. Its background-thread reservation policy is configurable. Default settings favor high background throughput on capable hardware, while a reduced setting leaves one processor free for the render thread, audio and other services, which suits phones and ARM64 devices running PojavLauncher-style environments. Advanced users can adjust behavior through JVM system properties, and the defaults are usable without any setup.

CatalystFX is published for Fabric only, across 9 release versions 1.20 – 26.2, under the MIT License, which is not open source. It is installed on the player's side alone, so servers need nothing. The latest Fabric file, 0.2.0, targets 26.2 and was published on 2026-08-27.