A second brain that’s already thinking before you are.

Most thinking tools ask too much. They want you to organize, tag, link, file, and remember to come back. They turn what should be a tool into a second job.

tentus started from a quieter belief: the work of organizing your own thinking shouldn’t fall back on you. The software should do it. Not by guessing wildly, and not by burying you in suggestions — but by paying close attention to what you’ve already captured and surfacing it at the right moment.

We call that moment a briefing. Lumi reads across your sources — docs, meetings, calendar, messages — and prepares context before you ask. When you sit down to write a reply, prep for a call, or revisit a decision, the relevant pieces are already there.

Lumi only knows what you’ve told it. That’s a feature, not a limit. A thinking tool that hallucinates is worse than no thinking tool at all. tentus stays inside your workspace, cites its sources, and admits when it doesn’t know.

What we’re not building.

We’re not building a chatbot. We’re not building a replacement for thinking. We’re not building another note app with a sidebar of AI buttons.

We’re building a quiet, fast notebook with a serious respect for the reader’s attention. The chrome disappears; the content is the work. The keyboard is the interface. The accent is terracotta and the page is warm.

Made alongside autn.io.

tentus is made by elmt studio, alongside autn.io. The two are siblings: tentus holds the thinking; autn moves it forward. Together they form a small, opinionated stack for people who don’t want their tools to be louder than their work.

Capture without friction. Retrieve without searching. Your ideas find each other. Nothing falls through.