letX connector
Use letX inside Claude Code
One command installs letX in Claude Code: the letX tools, plus two skills for compiling and fixing LaTeX and for starting from a template.
The plugin is in Anthropic’s plugin directory, and in OpenAI’s for Codex. The server alone also works in other tools that connect to remote MCP servers with OAuth. Needs a paid letX plan: Pro, Academic Pro, or a seat on a Team.
Pro is $18 a month, Academic Pro $9 a month for verified students, faculty and staff, and a Team seat $20 a month. See the plans
- 1
Install the letX plugin
Run:
claude plugin install letx@anthropic-plugin-directoryIt adds the letX server and two skills, compile-and-fix and start-from-template. Inside a session,/plugin install letx@anthropic-plugin-directorydoes the same, and /plugin finds it on the Discover tab. A plugin you added in claude.ai arrives on its own when you sign in with the same Claude account. - 2
Sign in, or make an account
The first call opens your browser on letx.app. If you are not already signed in to letX, this is where you land. Use Google or GitHub, or fill in the form. Already have an account? Press Sign in at the top. A free letX account can connect free for 7 days from the first time it connects, and the next screen says so; after that, connecting needs a paid letX plan (Pro, Academic Pro, or a seat on a Team).
- 3
Allow access
letX then asks what to grant. The screen names whichever client you are connecting, so read it and press Allow access. Your client stores the token, never your password, and you can disconnect later from Settings → Connected apps.
- 4
Use it
Inside Claude Code: “compile this paper with letx and show me the errors”, “list my letX projects”, “push this LaTeX into a new letX project”. To run a skill by name, type
/letx:compile-and-fix.
Adding the server alone instead
For Cursor, or a Claude Code or Codex setup without plugins, add the server by its URL. You get the same thirteen tools, without the two skills.
- 1
Add the server
In Claude Code, run:
claude mcp add --transport http letx https://api.letx.app/mcpIn Codex, run:codex mcp add letx --url https://api.letx.app/mcpIt opens letX in your browser straight away. If Codex later says it is not signed in, runcodex mcp login letx.
Then sign in and allow access exactly as in steps 2 and 3 above.
What Claude Code can do with letX connected
- Compile LaTeX → PDF on a real TeX Live farm
- Search 1000+ free LaTeX templates
- Start projects from any template
- Read & edit your project files
- See compile errors and fix them itself
- Hand off to the letX editor anytime
Frequently asked questions
Plugin or server: which should I add?
The plugin, in Claude Code. It installs the same server plus two skills that teach Claude Code to compile, read the error by file and line, fix it and compile again. Add the server alone when the client is not Claude Code, or when you only want the tools.
Is letX in Anthropic’s plugin directory?
Yes. It installs as letx@anthropic-plugin-directory, and in claude.ai it is under Customize → Plugins, at https://claude.ai/customize/plugins/id/f834c318-a1c6-4011-9c1c-5b928231476c%40anthropic-plugin-directory for a signed-in Claude user. Anthropic scans every version before it reaches the directory.
What about Codex or Cursor?
Same server, same URL. letX is in OpenAI’s plugin directory, which Codex shares with ChatGPT, so in Codex run codex plugin add letx@openai-curated-remote for the server plus the two skills. Codex needs a paid letX plan: the free week is for Claude only. For the server alone, run codex mcp add letx --url https://api.letx.app/mcp and approve in the browser tab it opens. Adding letX to config.toml by hand skips that sign-in, so run codex mcp login letx afterwards, or Codex keeps getting refused. In Cursor or Windsurf, add https://api.letx.app/mcp as a remote server in their MCP settings. letX follows the MCP authorization spec, so a client that supports remote servers with OAuth signs in the same way.
Do I need a paid plan?
To keep it, yes. A free letX account can use Claude Code with letX for 7 days, no card needed, starting when you connect. After that, connecting Claude Code is part of letX’s paid plans (Pro, Academic Pro, or a seat on a Team), and the consent screen links to them. Compiles that Claude Code runs count against your letX plan like any other.
I already connected letX in claude.ai. Do I add it again?
Usually not. Connectors you add in claude.ai are available in Claude Code when you sign in to Claude Code with the same Claude account.
Why compile on letX instead of local TeX?
A full, always-current TeX Live without installing 5GB locally, identical output for every collaborator, and the compiled project is instantly shareable and editable at letx.app.