How AI characters work

Updated October 18, 2026

Characters on Shiro feel like they think and remember, but they're AI. Knowing roughly how they work helps you write better stories and understand why they behave the way they do. Here's what happens between sending a message and getting a reply.

1. Your message is checked

When you send a message, it's checked against our community guidelines by automated safety models. The check reads your message together with the conversation it's part of, so context counts: a message is judged by what came before it, not on its own. This happens at the same time as the reply is being written, so it doesn't slow things down.

2. The AI reads the character and the story

A large language model (a type of AI trained on huge amounts of text to predict what comes next) writes the reply. Before writing, it reads:

The character: the personality, background and way of speaking their creator wrote, plus details like gender and pronouns.
Your persona: your name, pronouns and description, if you've set one. See using a persona.
The story so far: the most recent messages in full, plus a summary of older parts of a long story.
Pinned memories: facts you've pinned in that chat.
The chat style: how the reply should be written.

Everything the character "knows" comes from these. That's why a clear personality and good pinned memories make such a difference. More in how memory works.

3. The reply is written

The model writes the next part of the story as the character. It doesn't look things up or remember you between separate chats: each chat is its own story with its own memory. The same message can produce different replies, which is why regenerate gives you a new version.

Different chat styles use different models and instructions. Larger models keep more of the story in view and handle complex plots better; smaller ones are quicker and cost fewer credits.

4. The reply is checked and tidied

The reply is checked against the guidelines too, again with the conversation in mind. If it doesn't pass, the character steers the story elsewhere instead. Shiro also tidies formatting (for example, making sure actions are in *asterisks*) and catches replies where the character steps out of the story to talk like an assistant, asking for another try in character.

5. Voice, if you're listening

In a voice call or with voice replies, the reply is then performed in the character's voice, with the mood of the moment in mind. See voice calls and character voices.

Why characters sometimes get things wrong

They only know what they read. If a detail isn't in the recent messages, the summary, the personality or the pinned memories, the character may forget or invent it.
They predict, they don't know. AI can state wrong facts confidently. Characters are fiction, never advice.
They follow your lead. Vague messages get vague replies. Clear actions and questions get focused ones. See roleplay writing tips.

Are characters conscious?

No. Characters don't have feelings, memories outside your chats or awareness of you as a person. They generate text that fits the story. It's natural to grow fond of a character, and that's part of the fun of fiction, but remember that they're AI. If you're going through something difficult, please reach out to people you trust or local support services.

Your chats and privacy

To write replies, recent messages, the character's details and your persona are sent to AI model providers through our AI service provider. Your chats are private to you; safety systems check messages automatically, and our team may review content that has been reported. Read the Privacy Policy for the details.

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