Concurrent Chunk Management Engine - Forge

C2ME-Forge 0.2.0-forge.9.5 (Minecraft 1.20.1) - build 2026-09-19

On top of forge.9.4: the second server-freeze variant, the remaining Meulti's Backrooms crash, and chunk-save compatibility with other mods. No worldgen changes, existing worlds unaffected.

Fixed
• Permanent server freeze, second variant: a mod asking for a DIFFERENT chunk from inside a chunk load (entity-join and chunk-load handlers do this). Vanilla hands the server thread one chunk's promotion at a time and only hands over the next after the current one returns, so the other chunk's promotion could never start; and C2ME's scheduler held a worker slot and a neighbour lock on the chunk for as long as its promotion took, so the other chunk's generation could not start either. Promotion now runs as an ordinary main-thread task, and the final step no longer takes a slot or a lock. Same-seed worlds are unchanged
• Crash in Meulti's Backrooms level one and level zero (ArrayIndexOutOfBoundsException in Long2ObjectOpenHashMap.rehash from LevelOneBigRoomRegistry.register). The mod keeps its big-room map in a plain hash map and writes it from its surface step, which runs on several worker threads at once. New config key threadedWorldGen.serializedChunkGenerators lists chunk-generator class-name prefixes whose parallel generation steps run one chunk at a time within their own dimension; it defaults to fr.meulti.mbackrooms. Every other generator, vanilla included, stays fully parallel, so the overworld and every other dimension are untouched. Set it to "none" to switch it off

Compatibility
• Other mods can now hook chunk saving next to C2ME. C2ME's chunk serializer replaces the save routine outright, and the way it did so meant any other mod hooking the same routine either failed to apply at startup (a hard crash for mods whose mixins are marked required) or was silently wiped, depending only on which mod happened to load first. Smooth Chunk Save and Shadowed's No More Lazy Chunk Loader both landed on this. The replacement is now applied as a high-priority hook instead: other mods' hooks apply cleanly, and C2ME's serializer still runs first and performs the save, so behaviour with C2ME alone is unchanged
• Shadowed's No More Lazy Chunk Loader 1.0.1 boots and generates alongside C2ME with no mixin errors; a 4,225-chunk pre-generation with both installed wrote every chunk to disk and matched a vanilla world of the same seed block for block. Its off-thread chunk reader is bypassed by C2ME's own storage, so the two never touch region files at the same time

Configuration
• A config override given on the command line (-Dc2me.base.config.override.<key>=<value>) now applies to that launch only. It used to be written into c2me.toml, so a one-off test flag silently became permanent
• New key threadedWorldGen.serializedChunkGenerators (see Fixed)

Diagnostics
• One line at server start names the hardware the run is on (CPU, threads, RAM, max heap, worldgen workers, Java, OS), so a latest.log with a Chunky pre-generation in it is a complete benchmark record. A script that turns such a log into a card for the Discord benchmark list ships with the mod's sources

Drop-in update - recommended for everyone on forge.9.x, and required if you use Meulti's Backrooms, Smooth Chunk Save or No More Lazy Chunk Loader. No config changes needed.
Support: https://discord.gg/s7BYs6Njj5