Social norms have not caught up here. Because the technology arrived well ahead of any common understanding, the topic carries more weight than the habit itself deserves.
Treat what follows as a few useful ways of thinking, not as rules.
A single question that covers most cases
Leave aside the arguments over whether this is "cheating" or "weird". They go nowhere, and most people use them to defend a conclusion they reached long ago.
Ask yourself this: if someone discovered it rather than hearing it from me, would I mind?
If you would not mind, you are simply using software, and there is nothing that needs announcing. If you would, pay attention to that feeling. It does not prove you are doing anything wrong. It shows that, for you, the habit carries a meaning you have not said aloud.
For anyone with a partner, this question settles more than any debate over definitions.
With a partner
The best argument for telling them is a mundane one: they will find out sooner or later, and that goes worse than volunteering it. Think of a phone left unlocked, a notification on the lock screen, a strange charge on a shared account. Practical safeguards are discussed in payment privacy and using a shared device, but no precaution is foolproof.
When you raise it, two approaches work well.
Describe it plainly and skip the defensive speech. Saying "I've started using an AI chat app, kind of like a game" invites a chat. Launching into reasons why it is meaningless invites cross-examination.
Hear the worry behind the words. Rarely is it really about the app. The real question tends to be "are you missing something in this relationship?", and it calls for an honest reply, not comfort about technology.
Occasionally the truthful reply is yes. Better to know, and the app is not to blame for it.
With friends
Expect less drama than you fear. Most friends respond with curiosity and ask what it is actually like, since plenty of them have read about these apps but never tried one.
A short, candid summary is enough: it is entertaining, it resembles a novel that talks back, and the price is about that of a streaming plan.
Anyone who reacts harshly is usually reacting to a stereotype of the lonely user, not to you. The stereotype merits a closer look, but it does not justify lying.
On the job
Avoid it.
The concern is what your employer can see, not social judgment. Work laptops are managed equipment and company networks are monitored, and that is not yours to contest. Keep the whole thing off employer devices, for the reasons set out in using a shared device.
Finding the right phrasing
Speak about what you do and leave out the relationship label. "I use an AI chat app" and "I have an AI girlfriend" are equally accurate, but the former draws a question and the latter a verdict.
Follow up with what the app does for you in plain terms: it helps you relax, it is enjoyable for creative writing, it makes a quiet night less empty. These are everyday motives, and describing them that way is honest as well as persuasive.
The case where discomfort is justified
One scenario should be named directly, since candour serves you better than reassurance.
Imagine you would hesitate to mention the app because it is standing in for something you should be doing, such as calling back a friend, going out or facing a chore. Your hesitation then concerns the substitution, not the app. Setting boundaries with an AI partner discusses that warning sign, and it is far better spotted early.
That is not the situation for most people. They open the app a few evenings each week, and the only friction is a brief, awkward conversation that passes quickly.
A line to borrow
"It's a chat app where you talk to a character. It helps me switch off, and I wanted you to hear about it from me and not stumble on the charge."
It is open and unapologetic, and it shows you were thinking about the other person, which is usually everything they wanted to know.
