CoreSwap — a C++ rewrite of Minecraft's worldgen

by unknowbug · 2026-09-03 · Mods

What it is: CoreSwap rewrites Minecraft Java Edition's performance-critical cores — world generation and entity AI/pathfinding — in C++, while keeping the full Java mod ecosystem intact. Same seed. Same world. Same mods. The C++ goes underneath. Why: Java Edition's performance has been a meme for two decades. Every existing fix has a fatal flaw:[td][table background=null] [tbody] [tr] [td width=]Approach[/td] [td width=]Flaw[/td] [/tr] [tr] [td]Paper & optimization plugins[/td] [td]Still Java — treats symptoms, not causes[/td] [/tr] [tr] [td]Cuberite (full C++ rewrite)[/td] [td]Fast, but the mod ecosystem dies[/td] [/tr] [tr] [td]Switch to Bedrock[/td] [td]Ecosystem gone, version drift forever[/td] [/tr] [/tbody] [/table]CoreSwap walks the path nobody has walked: [b]C++ performance core + Java mod layer (JNI bridge)[/b] — the mod API stays Java and untouched; everything below it is free to become C++.[b]v1.0.0 (MC 1.20.1, Fabric):[/b][list] [*]✅ [b]NOISE+SURFACE (density / aquifer / ore veins / surface rules) 100% bit-identical to vanilla[/b] — same seed, same terrain, block-for-block (exact IEEE double)[/*] [*]✅ [b]10-20× faster worldgen[/b]: batched parallel generation (~3 ms/chu