No, I'd say it's a _fairly_ valid claim. You have to interact with Immutable.js objects using its API, and every update API call returns a new instance. So, i

No, I'd say it's a _fairly_ valid claim. You have to interact with Immutable.js objects using its API, and every update API call returns a new instance. So, it _does_ generally enforce immutability. As far as I know, the only way to accidentally mutate stuff with Immutable.js is if you insert plain JS objects inside an Immutable.js object, and possibly also use one of its "update this using a callback function" methods and misuse things inside the callback.