Direct answer
Spigot nerf-spawner-mobs removes much of the normal AI from spawner-created mobs. It does not disable spawning or make their entity ticks free.
How to check it
- Compare spawner output and mob behavior with the option on and off in a test copy. Include water channels, fall chambers and any mob mechanics the farm relies on.
- Record the original configuration or test conditions, capture a profile or a repeatable observation, and identify the affected world or player group.
- Make the measurement under the same player count and workload you will later use to verify the change.
What to change
This setting is useful only if the AI saved is worth the behavior change. The Paper world setting spawner-nerfed-mobs-should-jump is a separate option; verify it exists in the exact version before relying on it.
Do not enable globally for public dungeon or adventure encounters without checking mob combat and movement.
Software and version notes
Check the active version and generated configuration before copying paths or values. Different forks and mod loaders may implement this behavior differently.
This article is written for Paper / compatible servers. Configuration keys and defaults can move between versions. The source material checked for this page includes PaperMC spigot.yml reference. If your server is Folia, Leaf, Purpur, Fabric, Forge, NeoForge, or another fork/loader, do not assume a Paper-only setting exists or behaves identically.
Verify the result
Repeat the same test with the same software build, player count and world activity. Compare the targeted symptom and any spark measurements, then check that intended game mechanics still work. If the change does not produce a reproducible improvement, revert to the recorded baseline.