Direct answer
The option enable-async-mob-spawning moves some expensive mob-count/spawn-state work to a worker thread. Normal spawning decisions still depend on mob caps, world rules and loaded chunks; this setting is not a remedy for farms that produce no mobs.
How to check it
- Check the option exists in your Pufferfish-generated pufferfish.yml and is enabled.
- Before changing it, compare mob counts, world difficulty, gamerules and per-player spawning behavior.
- Use comparable player positions and world loads to measure CPU and mob-spawn results; check worker exceptions in the log.
What to change
The Pufferfish configuration guide uses the following top-level setting:
enable-async-mob-spawning: trueIf a specific plugin or build produces errors, disable the feature for a controlled comparison and report the matching Pufferfish/MC versions. Do not simultaneously modify spawn caps or simulation distance.
Pufferfish’s published source patch for the 1.21 branch shows off-thread spawn-count preparation and flags potential small spawn-count variation. Do not present performance claims for that old patch as guaranteed on future releases.
Software and version notes
The Pufferfish Host knowledgebase is historical configuration documentation. Check current pufferfish.yml and the changelog of your exact Pufferfish build before applying example values.
Verify the result
Compare mobs spawned per minute, worker exceptions, and server tick cost under the same conditions. Restore the original setting if correctness degrades.