# About the assistant

What the sits lens assistant is for, where its answers come from, and what it keeps.

## What it is for

The assistant answers questions about the page you are on and about sits. It answers from the sits book, the sits reference and the pages of sits lens, and numbers the sources it uses under its answer. Its answers are written by Claude, a model made by Anthropic.

## It can be wrong

The assistant can be wrong, even when it cites a source. Open its sources and check what it says against them, and against what the page shows.

## Where your questions go

The sits lens server passes what you send to four services. Each keeps what it receives under its own terms; this page says what sits lens sends each, and what it asks Langfuse to keep:

- Anthropic, so that Claude can write the answer: each question with its page context and the earlier messages, on the project's key or on yours;
- sitsmcp, the sits search service: the searches the assistant makes in the sits book and the sits reference;
- Upstash: the counts behind the limits (see “Your address” below);
- Langfuse: the record of each question and answer described next.

## What is kept

Each question is kept to improve sits lens, in Langfuse Cloud, in its EU region, for 12 months. It is kept under a random id that your browser makes and keeps. The id is not tied to a person: not to your name, and not to your address.

With each question are kept:

- your question, and what the assistant was given to answer it: the page and step you were on, any text you selected, any part of a figure you asked about, and the earlier messages of the conversation;
- the searches the assistant made and the sources they found;
- the answer, the model that wrote it and how many tokens it used;
- whether you found the answer helpful, when you say so.

## Your address

Your address is used only to count questions and votes in the hour, for the limits. The server keeps a short keyed hash of it, made with a secret only the server holds, with the random id, in Upstash. Each count is deleted after about two hours.

The project pays for 10 questions a day from one connection, the day running from midnight to midnight, UTC. That count is kept under the same hash, and deleted a day after its first question. Votes and questions asked with your own key do not count toward it.

Your address is not sent to Langfuse, and the assistant's own logs do not record it.

## Keys

Before a question goes to the model or to Langfuse, the server removes each word that starts with sk-ant-, sk-lf-, pk-lf-, sk-proj- or sk- and goes on for at least 16 letters, digits, hyphens or underscores, in the question and in the selected text. It reads “\[key removed]” instead.

Before Langfuse keeps anything, the server also removes your own key, and any text that starts with sk-ant-, sk-lf- or pk-lf-, whatever its length.

Other secrets, and shorter ones, are not caught: do not paste them.

## Your own Anthropic key

You can ask with your own Anthropic key at any time: press "Use my own key" under the question's box. The panel offers it too when your questions for the hour, your connection's questions for the day or the project's budget for the day run out. A key with its own spend limit is best.

Your key goes from your browser to the sits lens server with each question, and from there to Anthropic, for that question only. The server does not store it or log it, and it is removed from what Langfuse keeps.

In your browser the key stays for the page you are on. If you tick “Remember for this tab”, which is off at first, it is kept in this tab's session storage until you close the tab or remove the key. It is never kept in your browser's local storage.

Questions asked with your key do not count toward your questions for the hour, your connection's questions for the day or the project's budget, so they are still there once you remove it. The limit per address for the hour still applies.

## What your browser keeps

Your browser keeps the conversation for this tab, as you typed it, so it follows you from page to page, until you close the tab. Only the server removes keys, so a key pasted into a question stays in that copy.

It keeps the random id and the panel's width until you clear the site's data.