What does this mod do?
This is a fabric mod which fixes MC-265520 in Minecraft versions <1.20.5.
What is MC-265520 about?
MC-265520 is about a race condition when switching between protocol states. The protocol states get switched while decoding packets and Minecraft expects the old protocol state when handling the switching packet on the main thread.
How does this mod solve the issue?
This mod moves the FlowControlHandler added because of MC-265209 in front of the handler which switches protocol states.
The mod also uses a custom FlowControlHandler (based on the old, MIT-licensed AutoReadHolderHandler of Velocity) instead of changing how the entire networking pipeline works (as Mojang did in 1.20.5).
- Edition: Minecraft Java
- File type: .jar
- Minecraft versions listed: 1.20.3, 1.20.4
- How to install: Install the matching mod loader (Forge, Fabric or NeoForge) for your Minecraft version. → Download the .jar. → Put it in the .minecraft/mods folder and launch that loader profile.
- Where to get it: Opens on Modrinth — not every file is mirrored on our own servers.
Install steps are the general flow for this file type — How to install Minecraft Java mods & modpacks walks through it step by step.
- Ships as MC-265520-Patch-1.0.0.jar — drop this file into the mods folder
- Download size: 62 KB
- Download link checked 1 Sept 2026 — working
These come from our own check of the pack file, not from the source page.