Yes. The free plan has no time limit and includes 40 compiles per day, a two-minute build limit, the last 15 versions, the full template library, real-time editing, and unlimited collaborators. Lexi and MCP access are the paid parts.

What is the difference between Pro and Academic Pro?

Academic Pro is $9 per month and gives students, faculty, and staff unlimited compiles, full history, and a reduced Lexi allowance. Pro is $18 per month and adds MCP access from Claude and ChatGPT, Lexi web search, a priority compile queue, and GitHub import and export.

Do I need a university email for Academic Pro?

No, and an academic email on its own is not enough. Verification uses a current transcript or a student or staff ID, which is why the plan can cover faculty and staff rather than students alone.

Can Claude or ChatGPT edit my LaTeX project directly?

Yes, through the hosted MCP server at api.letx.app/mcp on the Pro plan. The connection uses OAuth 2.1, so the client never sees your password, the consent screen lists the scopes it is asking for, and you can revoke access later. Six of the thirteen tools can write, and prior versions stay recoverable.

Does LetX train AI on my documents?

LetX's published privacy policy states that private documents are not used to train AI without explicit opt-in consent. Confirm the current wording on the policy page before relying on it in a procurement review.

← Journal

Product research · August 29, 2026

LetX in 2026: Lexi, MCP, and Academic Pro

What LetX is after the 28 August release: a compiler-aware agent, a hosted MCP server, and two paid plans. Figures rechecked on September 25, 2026.

By Shihab Shahriar Antor · Updated 2026-09-27

The free editor is the part most people meet first: real-time collaboration, a thousand compile-tested templates, and full TeX Live in the browser. That is not the part this note is about. The two capabilities added on 28 August change what the product is for, and they are the two nobody has heard of.

The verified baseline

Every figure below carries the date it was checked. The canonical source is LetX by the Numbers, which states when its own data was last verified. Treat these as a dated snapshot, not a permanent claim.

LetX platform figures

Measure	Value	How it is defined
Registered users	4,400+	Students, researchers, and faculty
Universities and labs	350+	Rounded down from 359 institutions behind verified academic email domains
Countries	60+	Rounded down from 63 verified institution locations, not self-reported profiles
Compile-tested templates	1,000+	Across 20 categories, all editable in the browser
Lexi tokens processed	220M+	Input and output tokens processed since Lexi launched, rounded down from 226,566,554
Typical compile	~6 s	About 2 s queue plus about 3.7 s median, over 12,700 compiles in 30 days
CTAN packages	5,000+	Full TeX Live preinstalled

Adoption and catalogue figures checked September 25, 2026. The public claims are rounded down from 4,448 registered accounts, 359 institutions, 63 countries, 1,019 templates, and 226,566,554 Lexi tokens. A verified academic email domain shows where a user works. It is not an institutional endorsement.

Lexi compiles its own edits

A general chat model usually sees only the text pasted into the conversation. It cannot see your document class, a local macro, the bibliography, an included chapter, an image path, or the exact error pdfLaTeX emitted. So an answer can look correct and still fail in the real project.

Lexi works inside the project boundary instead. It reads the files, the bibliography, and the actual compile log, applies a change in place, runs the compiler, and uses the result to decide what to do next. The previous version stays recoverable.

A successful compile proves something narrow but real: the edited source was accepted by the toolchain and produced output. It does not prove the mathematics, the citations, the originality, or that a journal will accept the formatting. The loop removes one class of uncertainty. It does not replace review.

The 18 documented Lexi commands

/fixRepair
Reads the compile log, finds the failing line, and corrects it.
/explainRepair
Explains what a command or an error actually means.
/cleanRepair
Strips invisible characters and normalises punctuation.
/outlineStructure
Proposes a document structure before you commit to one.
/scaffoldStructure
Generates a starter document for a given kind of work.
/formatStructure
Adjusts spacing, sectioning, and layout.
/convertStructure
Reformats a document for a different venue.
/tableContent
Turns pasted data into a booktabs table.
/figureContent
Inserts a figure with the float and caption set up correctly.
/diagramContent
Generates a TikZ diagram from a description.
/beamerContent
Creates a presentation template.
/slidesContent
Turns a paper into Beamer slides.
/image-to-texConversion
Converts a screenshot of a table or equation into LaTeX.
/pdf-to-texConversion
Rebuilds a PDF document as editable source.
/citeWriting
Adds citations along with the matching .bib entries.
/shortenWriting
Trims text to a word or page limit.
/humanizeWriting
Rewrites a passage in a more natural voice.
/translateWriting
Handles multilingual text, including the font setup it needs.

Showing 18 of 18.

A hosted MCP server

The same loop is available from outside the editor. The hosted endpoint at https://api.letx.app/mcp connects an OAuth-capable client to your LetX projects, and LetX documents it as tested with Claude, ChatGPT, and Claude Code.

The difference from uploading a file to a chat is worth being precise about. An attachment is a snapshot: if the model rewrites it, someone has to copy the result back into the real project, and the model never sees whether it builds. An MCP connection exposes named operations against the project itself, and what comes out the other end is still a LetX project with version history and collaborators.

It is not a remote shell. The surface is thirteen named tools, and the split between the ones that read and the ones that write is the part to inspect before you approve anything.

The 13 documented MCP tools

search_templatesRead only
Searches the template library.
get_templateRead only
Returns a template's full record, including licence and preview.
list_projectsRead only
Lists the projects on the account.
list_project_filesRead only
Lists a project's documents and assets with exact paths.
read_project_fileRead only
Reads one text file from a project.
create_project_from_templateWrites
Starts a new project from a template.
create_projectWrites
Creates a project from supplied LaTeX source.
update_project_fileWrites
Creates or replaces a file, keeping version history.
compile_latexWrites
Compiles loose source to PDF.
compile_projectWrites
Compiles a stored project and returns the PDF or the error log.
set_project_compilerWrites
Switches between pdfLaTeX, XeLaTeX, and LuaLaTeX.
searchDeep research
Deep-research search over templates.
fetchDeep research
Retrieves a full template record by id.

Authorisation is OAuth 2.1, so the client never receives the LetX password. The consent screen lists the scopes requested, access can be revoked afterwards, and prior file versions stay recoverable in LetX. Tool calls still consume the account's normal plan limits.

What each plan actually costs

Self-service checkout is live by card, with Lemon Squeezy as merchant of record, so LetX does not receive full card numbers. Academic Pro is not a student-only plan: it covers faculty and staff too, and it is verified with a current transcript or a student or staff ID rather than the email domain alone.

Free, Pro, and Academic Pro

Feature	Free$0	Academic Pro$9 / month	Pro$18 / month
Daily compiles	40	Unlimited	Unlimited
Build time limit	2 minutes	5 minutes	5 minutes
Version history	Last 15	Full	Full
Templates	All 1,000+	All 1,000+	All 1,000+
Unlimited collaborators	Yes	Yes	Yes
Lexi allowance	No	Reduced	Monthly
MCP access from Claude and ChatGPT	No	No	Yes
Lexi web search	No	No	Yes
Priority compile queue	No	No	Yes
GitHub import and export	No	No	Yes
	Start free	See pricing	See pricing

Yearly billing is $90 for Academic Pro and $180 for Pro. Classroom, lab, university, and department licences are priced separately. Listed as checked on September 27, 2026; confirm current prices on the official pricing page before relying on them.

Questions

Is LetX free?: Yes. The free plan has no time limit and includes 40 compiles per day, a two-minute build limit, the last 15 versions, the full template library, real-time editing, and unlimited collaborators. Lexi and MCP access are the paid parts.
What is the difference between Pro and Academic Pro?: Academic Pro is $9 per month and gives students, faculty, and staff unlimited compiles, full history, and a reduced Lexi allowance. Pro is $18 per month and adds MCP access from Claude and ChatGPT, Lexi web search, a priority compile queue, and GitHub import and export.
Do I need a university email for Academic Pro?: No, and an academic email on its own is not enough. Verification uses a current transcript or a student or staff ID, which is why the plan can cover faculty and staff rather than students alone.
Can Claude or ChatGPT edit my LaTeX project directly?: Yes, through the hosted MCP server at api.letx.app/mcp on the Pro plan. The connection uses OAuth 2.1, so the client never sees your password, the consent screen lists the scopes it is asking for, and you can revoke access later. Six of the thirteen tools can write, and prior versions stay recoverable.
Does LetX train AI on my documents?: LetX's published privacy policy states that private documents are not used to train AI without explicit opt-in consent. Confirm the current wording on the policy page before relying on it in a procurement review.