Direct answer

On the documented Leaf 1.21.1 config, async.async-pathfinding.max-threads specifies a maximum worker count; 0 requests automatic sizing. Allocating more threads can help if pathfinding is the measured bottleneck and idle CPU is available, but it is not a universal optimization.

How to check it

  1. Read available logical CPUs and CPU limits from your host panel/container rather than assuming the full host machine is dedicated to Minecraft.
  2. Measure the same pathfinding-heavy workload with the current max-threads setting, and note CPU contention plus tick latency.
  3. Check that the feature itself is enabled; thread parameters alone do not turn it on.

What to change

Start with the generated automatic value rather than a high hard-coded number:

async:
  async-pathfinding:
    max-threads: 0  # auto on the documented 1.21.1 branch

Increase the maximum cautiously only when workers are saturated and adequate CPU headroom remains; avoid making one setting compensate for unrelated entity or chunk bottlenecks.

Compatibility and safety

Leaf 1.21.1 documents automatic max-threads=0 as using about a quarter of the CPU cores, minimum one. This is historical branch behavior, not a guarantee for later releases.

Software and version notes

The cited Leaf global config page explicitly describes the 1.21.1 branch; newer Leaf builds may have different keys, defaults or feature support. Verify config/leaf-global.yml generated by your actual server.

Verify the result

Compare CPU saturation, pathfinding cost and mob navigation before/after one change. Keep a copy of the original YAML and restart as required by the target build.

References