ModsFinder

MC-265520 Patch

by FroglightNET

MC-265520 Patch is a Fabric client mod that fixes the MC-265520 race condition in Minecraft networking.

FabricClient-side onlyMIT LicenseOpen source1.20.3 – 1.20.4

What it does

The bug concerns protocol states switching while packets are decoded, where the game still expects the old state handling. Packet processing is moved off the main thread at the point where that switch happens, so the two no longer race. The fix targets the networking pipeline that Mojang changed in the later release.

To control packet flow, the mod uses a custom FlowControlHandler. It is based on the AutoReadHolderHandler from Velocity, which is released under the MIT License, and it is added because of MC-265209, a front handler that also switches protocol states. The handler is used in place of changing the existing pipeline logic.

The mod runs on the client only and is published for 1.20.3 and 1.20.4, with 1.0.0 for 1.20.4 as the latest file. The code is open source under the MIT License, and the source and issue tracker are public.

Key features

  1. Race condition fix

    Protocol state switches during packet decoding no longer race with the main thread, which is the behavior tracked as MC-265520.

  2. Custom flow control

    A custom FlowControlHandler replaces the built-in path that changes how packets are read, leaving the rest of the pipeline in place.

  3. Velocity-derived handler

    The handler adapts the AutoReadHolderHandler from Velocity, so the flow control logic traces back to a known MIT-licensed design.

Compatibility

Latest build for each game version and loader.

1.20.41.0.0
1.20.31.0.0
ReleaseBetaAlphaNot available

Only full game releases are shown. This mod publishes no snapshot builds.

How it compares

Full comparison

KeepResourcePackOnProxiedServerSwitch is a Fabric client mod for 1.20.2, released under the MIT License, and it is not open source. Minor client fixes is a Fabric client mod for 1.20.1 under All rights reserved, so its code is not open source. ViaVanillaPlus is open source under the MIT License, a client-side only mod for Fabric and Quilt covering 1.20.2 – 1.20.4, which makes it the closest match in version range.

ModLoadersGame versionsEnvironmentUpdated
MC-265520 PatchFabric1.20.3 – 1.20.4Client-side only2024-04-11
KeepResourcePackOnProxiedServerSwitchFabric1.20.2Client-side only2023-09-19
Minor client fixesFabric1.20.1Client-side only2023-08-26
ViaVanillaPlusFabric and Quilt1.20.2 – 1.20.4Client-side only2024-03-23

Questions

Does MC-265520 Patch need to be installed on the server?

No. It is installed on the player's side alone, so servers need nothing.

Which loader does MC-265520 Patch support?

Only Fabric. Files are published for Fabric alone, for 1.20.3 and 1.20.4.

Does the patch depend on other mods?

No required dependencies are listed for the mod.

In the catalog

MC-265520 Patch is one of 7,555 Cursed mods on ModsFinder, and one of 4,235 Cursed mods for Fabric. 13,907 mods support Minecraft 1.20.4.

Cursed mods7,555Fabric modsMods for 1.20.413,907

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What the author says

This is a fabric mod which fixes MC-265520 in Minecraft versions <1.20.5. 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.
FroglightNET, on the Modrinth page

Official listing

Owner
FroglightNET
Published
2024-04-11
Updated on Modrinth
2024-04-11
Facts verified
2026-10-15

Tags

CursedUtilityOptimization
Open on ModrinthCompare