a Rust library for creating hierarchical state machines

In plain words

Moku is a Rust library for building hierarchical state machines with nested states. It reduces boilerplate code that typically obscures state machine logic when implemented manually. The library provides features designed to address gaps in existing Rust state machine tools, making it easier for developers to create complex state machine implementations without error-prone repetitive code.

written from the facts on this page · September 2026

From the sources

moku

Moku is a Rust library for creating hierarchical state machines. While it’s also useful for creating flat state machines, nested states are a first-class feature. Though it may be impure to store data inside of states, in practice it is often useful for states to hold some data (e.g. file handles, perf counters, etc) and to allow substates and external code to access that data. This is also a core feature of moku. Because moku generates a tree of sum types to represent the state machine, states must be Sized and do not support generic parameters (though generics can be used behind type aliases). A hierarchical state machine (HSM) is a type of finite state machine where states can be nested…from docs.rs

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