An AI smut writer that writes the whole book, not the scene
Most tools sold as an AI smut writer produce a scene. You type a few lines, you get a few hundred words back, and if you want what happens next you type again and hope it remembers who these people were. That is a generator. This writes a story: it plans a beginning, a middle and an ending, writes it a section at a time, and you steer after every one.
What actually happens
You give it a starting idea. One line is enough. "A reunion between two people who never stopped wanting each other" is a complete starting point, and everything after that is optional: who they are and what should matter about them, what is between them, the tone, whose eyes you want to be behind, how much should happen per section, and a box for the things that must be in it and the things that must never be.
Then you set how explicit it is, on five steps, per story. Intimacy present but not on the page. On the page through sensation rather than anatomy. Direct and unhedged. Fully explicit, first contact to finish, with nothing cut away. Rendered at length, beat by beat, in the words the two of them would actually use.
That level changes what is shown. It does not change who the people are, which is the single most common failure of everything else in this category.
Why section by section
Because that is the only way a long story stays coherent. The engine holds what has happened, who wants what, what has been promised and what has been refused, and it plans the next section against that rather than against the last paragraph.
It also puts you in the right place. After each section you can push it, redirect it, slow it down or say plainly that something was wrong. Most people who have tried to get a long explicit story out of a chat assistant have had the experience of watching it drift for four thousand words. This is the fix for that, and it is a structural fix rather than a better prompt.
Where "smut" comes into it
The word is doing real work here. Erotica is the publishing industry's word. Smut is the readers' word, and it usually means one specific thing: the sex is on the page and it is part of the story rather than the place the story stops.
That is what this writes. Not scene generation with a plot bolted on, and not a romance that fades out at the bedroom door. The guide to what smut means sets out the difference properly, including the four questions that actually decide whether you will like a book.
What it will not write
Everyone in a sexual context is an adult. That is not a setting, a level or a preference, and it is not negotiable by rephrasing.
Beyond that, the boundary is narrow and it is written down rather than guessed at. The guide to why AI keeps refusing explains what a content boundary is and why most refusals you have run into elsewhere were not about the thing you asked for. No shame. Not no limits.
What happens to what you write
Your stories are encrypted at rest. We can read them to write them. Nobody else can read them.
That sentence is on every page of this site in the same words because it is the one privacy claim we can prove, and because the alternative claims in this industry are mostly unprovable. The privacy guide sets out exactly what it covers, what it does not, and what an attacker would actually get.
How long a story gets
As long as you keep going. Sections run several hundred words each and a story can run to dozens of them, which puts a finished one in the range of a short novel rather than a scene.
The guide to prompting a long erotic novel is the practical version of that: what to put in the first box so the book holds together at section thirty.
What to ask for
Be specific about what the sex is doing, not about how much of it there should be. "Praise given only after something difficult", "an argument that turns", "a first time between people who have known each other for years" all produce different books from the same two characters.
Then set the explicitness separately. How much is shown and what it means are two different dials, and most disappointment comes from setting one and expecting the other to follow.
Every character in a sexual context is an adult. That one is not a setting.