Word for having no impact on state

Solution 1:

Is there a single word for the similar concept of "having no side effects"?

nullipotent

In computing, contrast with idempotent:

both refer to the potential result of performing an action on an object multiple times, the difference being that an idempotent action's result would be the same as performing it one time, while the nullipotent action's result would be the same as performing it zero times.

In other words, a nullipotent action has no side effects – performing it multiple times is the same as performing it zero times. An idempotent action has no further side effects after the first time performing it – performing it multiple times is the same as performing it one time.

By the way, I discovered nullipotent while researching idempotent recently. I'm not sure if we have the same understanding of idempotent, but I think nullipotent may be the word you're searching for.