MicroMachine

At under 50 lines, it eliminates bloat and dependencies, making it easy to audit and understand, as highlighted in the README's emphasis on providing only essential FSM functionality.

It uses plain Ruby hashes and methods like `when` for transitions, allowing flexible instantiation within models without mixins, as demonstrated in the ActiveRecord integration examples.

Supports callbacks on specific states or any transition with payload passing, enabling custom actions like persisting state changes, as shown in the `on(:any)` example.

Provides methods like `trigger?` for safe state checking and `events` for listing all possible transitions, aiding in debugging and dynamic workflows.