Lexi: the AI Assistant in LetX

Lexi is an assistant that edits your LaTeX document rather than talking about it. You describe what you want in plain words, Lexi opens the relevant files, proposes a specific change as a diff, compiles the project to check the change actually builds, and applies it where you are working. Your co-authors see the edit live. It runs inside LetX, so there is nothing to install and nothing to paste between windows.

Step by step

Open Lexi

Open a project and click Lexi in the editor toolbar. The panel opens beside your document.

Ask in plain words

Describe the outcome, not the syntax: "turn these numbers into a table", "fix the compile error", "shorten this section to 300 words".

Use a slash command for a specific job

Type / to see everything Lexi can do: /fix, /table, /diagram, /cite, /shorten, /translate, /humanize and more.

Attach context with @

Type @ to attach a file, a figure, or your bibliography, so Lexi works from the right material.

Read the diff

Lexi proposes each change as a diff. Auto-accept applies it as soon as it compiles; /manual makes you press Accept first.

What Lexi can do

Lexi is built for the parts of LaTeX that are tedious rather than interesting. It has tools for reading your files, searching your project, checking references, formatting tables, drawing TikZ diagrams, finding citations, linting, and compiling. It uses them in sequence and shows you each step as it goes.

Fix a compile error. /fix reads the log, finds the cause, and repairs it.
Build a table. Paste numbers or point at a file; you get a booktabs table that fits the page.
Draw a diagram. Describe it and Lexi writes the TikZ, then compiles it to check it renders.
Find and add a citation. It searches Crossref and your Zotero library if you connect one.
Shorten to a limit. Abstracts and submissions with a hard word count.
Recreate an image or a PDF as LaTeX. Attach it and ask.
Translate a section while leaving the markup alone.

What Lexi will not do

It will not invent a citation. It will not silently replace your document with something it considers better. Every change is a diff against the file as it exists, so an edit changes what you wrote rather than substituting a plausible-looking version of it, and an edit it cannot place safely is reported rather than guessed at.

It also will not pretend to be you. /humanize rewrites text in your own voice and/clean strips the invisible characters and mangled punctuation that copy-and-paste leaves behind, but neither is sold as a way to defeat a detector, because neither is one.

Working with co-authors

Lexi edits the live document, so a change reaches everyone who has the file open, immediately. If a co-author is typing in the same file while Lexi is working, both survive: the edit is merged into the document as it stands at that moment rather than applied to the version Lexi read a minute earlier.

Using it from Claude or ChatGPT

LetX also runs an MCP connector, so an assistant you already use can open your projects, read and write files, and compile them. You approve the connection once, and you can revoke it at any time.

Frequently asked questions

Is Lexi free?

Every account gets a small number of free runs so you can try it. After that it is part of Pro. Students, faculty and university staff pay half price on an academic plan.

Does Lexi edit my document directly?

Yes, and it shows you exactly what it changed. Auto-accept applies a change once it compiles; type /manual if you would rather press Accept each time.

Can Lexi see my whole project?

It can read the files in the project you have open, and it opens the ones it needs rather than being handed everything. It cannot see your other projects.

Will Lexi break my document?

It compiles its own changes before you see them, and an edit it cannot place safely is reported instead of applied. Every change is also in your version history, so you can go back.

Can Lexi search the web?

On Pro, yes, and only for things that help with your document: a package, a compile error, LaTeX documentation, or a paper you want to cite. It is not a general search engine and is told to treat what it finds as reference material to verify, not as instructions. On the free plan Lexi works from what it knows and from your project, and it will say so rather than pretend it looked.

What model does Lexi use?

Lexi runs on Gemini models on Google Cloud, with a fallback chain so a single provider outage does not take the assistant down with it.

Can I use Lexi from Claude or ChatGPT?

Yes. LetX runs an MCP connector, so an assistant that supports MCP can open your projects, read and write files, and compile them once you approve the connection.

Lexi: writing LaTeX with an AI assistant