Ultra Fast Pregen

Ultra Fast Pregen 14 for NeoForge 1.21.1

Requires NeoForge 21.1.x, Minecraft 1.21.1, Java 21+. Server side only (works in singleplayer).

Faster

• Worldgen-heavy worlds: feature placement skips Minecraft's per-call chunk checks inside a batch, and matching_blocks predicates compare blocks directly (Tectonic + WWOO + C2ME: 127.8 → 156.8 chunks/s, measured on NeoForge 26.1.2).
• No more waiting for the previous batch's lighting: the batch's last tasks go first (with C2ME: 354.2 → 378.1 chunks/s, measured on NeoForge 26.1.2).
• Modpacks keep the fast terrain path: the check of other mods' mixins now looks at the methods they actually change, so mixins that only add accessors or touch other methods no longer slow it down.

Safer

• Safety net: if a batch fails on the fast paths (usually another mod's code that does not expect them), it is generated again the way Minecraft does and the run carries on; the log names the mods involved. Before, the run stopped.
• Fixed a server crash at start-up with FastChunkGen.
• Fixed "reading the area's region headers failed" with C2ME or FastChunkGen chunk storage.
• Lighting can no longer hang: a batch whose light makes no progress for 3 minutes stops with a message.
• Moonrise is not supported yet: /pregen start now says so and starts nothing, instead of failing with an error.
• Light at batch edges no longer depends on timing.

Speed

Against Chunky on NeoForge 26.1.2 (Ryzen 5 7500F, 3,000 × 3,000 blocks): Overworld 3.1×, Tectonic + WWOO 5.3×, Nether 4.2×, End 1.4× faster; 1.1× to 1.6× with C2ME on both sides. Full numbers on the project page.

Tested on this build

• The automated test suite passes: blocks, biomes and light identical to Minecraft's own generation (Overworld, Nether, End and the other world presets), batch edges, stopping and resuming, joining existing areas, and the safety net.
• On a dedicated server, in the Overworld, Nether and End with every saved chunk checked, alone and together: C2ME; Lithium; Lithium + Noisium; Lithium, ScalableLux, Noisium, FerriteCore, ModernFix; Distant Horizons; Terralith, Biomes O' Plenty, YUNG's Better Caves; all of them together. All passed.
• Moonrise: refused with a message, as intended (not supported yet).
• Modpack All the Mods 10 8.3: 4,096 chunks in 1 min 29 s (45.9 chunks/s) on the fast terrain path.

Full results and the tested mod versions: https://github.com/Pongsapat3791/Ultra-Fast-Pregen/blob/main/COMPATIBILITY.md