At heart, an AI girlfriend app is a chat screen over a large language model, plus a persistent character and a content filter. That's the whole category. The gap between a $10 app and a $20 one is seldom the model. It's how well the other two pieces are made.
Three pieces
The model writes the text. Shown everything it can see right now, it guesses a believable next message. It doesn't recall your last chat and has no wants of its own. Every hint of intention comes from the next two pieces.
The character sheet is a passage of text the app attaches before your message on every turn: who the character is, how they speak, what they know of you, and what's happened recently. You never see it. When someone says an app "has personality," this file is usually just well written.
The filter rules on what the character is allowed to say. It runs before the model, after it, or both. It explains why a scene can end in a polite refusal halfway through, and why "uncensored" is the loudest word in this market. Apps like Joi and Secret Desires compete mainly on how they tune that filter.
The context window and the complaints it causes
A model can only take in so much text at once. That budget is the context window, and your character sheet, the stored facts about you and the recent chat all compete for room in it.
As a conversation grows, the oldest turns drop out. The app hasn't lost interest, and it hasn't been downgraded. It just can't see that stretch anymore. Nearly every complaint that an app was better before comes down to this, which is why how memory is implemented matters more than how big the model is.
Inside the character sheet
Most apps assemble it from four ingredients.
- A persona covering name, age, backstory and speech style.
- Lasting facts about you that the app decided to keep.
- A running recap of your shared history, rewritten as it gets longer.
- The most recent messages, verbatim.
Apps that still feel present a week later, which is why Nomi scores as it does, handle the middle two well. None of that shows on a pricing page, so judging it takes weeks, not an afternoon.
What the label covers in practice
"AI girlfriend" stretches over products that hardly resemble one another.
- Companion apps aimed at an ongoing relationship, with journaling and mood tracking. Replika is the oldest example.
- Roleplay apps built around scenes and stories instead of continuity.
- Media-first apps where chat mostly exists to produce images and voice. Candy AI lands nearest the middle by packing all three into one subscription.
Pick which of the three you're after and roughly half the apps on any list drop out, ours included, before price even comes up.
What none of them are
Between sessions they know nothing about you unless they were built to store facts and fetch them later. They have no continuous self, because the character is reassembled from text on every single turn. And they aren't private by default. Your conversation gets processed on someone else's servers, a topic covered in what these apps know about you.
