I'd like to share my HTN planner written in C#, and based around the builder pattern. For now it's code-only, but I plan on building a toolset for it with serialization.

https://github.com/ptrefall/fluid-hierarchical-task-network

It's based primarily on Troy Humphrey's work, but I also used HTN planning professionally when working on Rust's tactical combative AI in the past. Fluid HTN is a newly written library based on everything I learned using HTN in practice.

My implementation supports partial plans and domain splicing, and is very easy to extend with new decomposition rules, like Random Select or Utility Select.

Hopefully someone can find it useful. Any criticism or input for improvement is appreciated.

- Pål