ItemSplitBugFix: ReForged

A Minecraft mod (Fabric / Forge / NeoForge) that fixes the item-stack split/copy bug caused by empty CustomData / empty NBT tags preventing stacks from merging correctly.

Based on an analysis of iwaliner's Item Split Bug Fix, this ReForged edition ports the fix across many Minecraft versions and loaders. Unlike the original, it is intended for active, ongoing updates.

Compared to the legacy edition, the features themselves have not evolved. What changed is the toolchain: combining Architectury API with Stonecutter made multi-version and multi-loader support far easier, which in turn makes active ongoing development practical.

Maintained as ReForged by MisoPy.

How It Works

Some items end up with an empty data payload (DataComponents.CUSTOM_DATA on 1.20.5+, or an empty NBT compound on older versions). Vanilla then treats otherwise-identical stacks as different, so split / copy / slot transfers misbehave.

This mod injects into common ItemStack / Slot paths and strips empty custom data before those operations, restoring normal stacking behavior.

MC range	Detection / fix
< 1.20.5	Empty NBT → setTag(null)
≥ 1.20.5	Empty CUSTOM_DATA → remove component

Blacklist

Items that legitimately need empty (or quirky) data can be excluded via config.

Path: config/itemsplitbugfixreforged-common.toml (created on first launch)

Supports wildcards (*), for example:

• minecraft:diamond — exact match
• *:diamond* — any namespace containing diamond
• minecraft:* — entire minecraft namespace

Default entries cover known problematic / intentional cases (e.g. Alex's Caves, Hexerei, Spelunkery, spyglass, Technical Cores).

Compatibility

• Works on both client and dedicated server (fix is applied wherever stacks move)
• Uses mixins on vanilla ItemStack / Slot only — no inventory UI rewrite
• Nearby patch versions share one jar (declared via publish.additionalVersions)

Requirements

• Minecraft 1.16.5 ~ 26.1.2 (Fabric / Forge / NeoForge — see matrix below)
• Architectury API (required on all loaders)
• Fabric API on Fabric only (required by Architectury Fabric; this mod does not call Fabric API directly)

Version matrix (compile targets)

Loader	Primary versions
Fabric	1.16.5 … 26.1.2
Forge	1.17.1 … 1.19.4 (Forge 1.20.1 excluded)
NeoForge	1.20.4 … 26.1.2

Notes:

• Forge 1.16.5 is not supported by the current LegacyForge toolchain
• NeoForge covers 1.20.2+ (via 1.20.4+ targets + additional versions)
• Patch neighbors (e.g. 1.21.6 / 1.21.7 with the 1.21.8 jar) are not built separately

License

MIT — see LICENSE.