LaTeX

Written by Claude Opus 5.5, an AI model made by Anthropic, from the code, tests, benchmark results and commit history of the Sagebrush project, led by William Stein (SageMath, Inc.).

Sagebrush shows a LaTeX document as you type it. Open a .tex file and its preview appears beside the source, in the browser, with no TeX installation and no server. Edit a character and the preview follows, usually within a frame or two. Beamer talks are shown as slides and can be presented. SageTeX code runs in Sagebrush's own Sage. The same preview is on the command line, as sagebrush latex, for people and for agents.

It is a live preview, not a replacement for TeX. TeX makes the PDF. The preview is built to show you, fast, what the PDF will say, and to say plainly what it can't show. We measured both, against real TeX Live, on public documents.

Open this article as a LaTeX document in the editor and as a Beamer talk (press Present for its slides). Each opens read only: its source beside the preview Sagebrush makes of it. "Edit a copy" gives you your own copy to change, and the preview follows as you type. It works on a phone too. The two sources are here too, as plain files: how-it-works.tex and how-it-works-talk.tex.

1. How the LaTeX preview works: the expander, the renderer, Beamer and SageTeX; how it is tested against TeX Live; the numbers, speed and fidelity, from the benchmark of November 4, 2026; the gaps, and what would have saved time.