neptune is an experimental client mod for TIDAL that provides a simple plugin and theme system.
you can download the neptune installer here.
neptune exfiltrates every single action one can do in TIDAL into an easily accessible API found on window.neptune.actions.
TIDAL is built on Redux and neptune's actions are simply exfiltrated Redux actions, which are explained in this document on Redux's website.
neptune includes full type definitions for all of TIDAL's actions.
To get the global Redux store's state, you can use window.neptune.store.getState(). The return value of getState() will change as a direct result of actions.
To intercept and subscribe to actions, you can use window.neptune.intercept("category/ACTION_NAME", ([payload]) => {}), with the first argument being the name (or an array of names) of the action(s) to subscribe to, and the second argument being a function that gets called upon that action being ran. If you return true the action will automatically be cancelled.
A template for making neptune plugins is available here.