How To: Use Tectonic with AucTeX

This section is a guide aimed at GNU Emacs users for setting up AucTeX with Tectonic as the TeX/LaTeX distribution.

Basic Prerequisites

To follow this section you will need Tectonic and GNU Emacs installed on your system. Additionally, you will require the AucTeX emacs package to be installed before following along.

Note: This section makes use of the V2 tectonic CLI, invoked using the tectonic -X flag or nextonic command alias.


All the code displayed in this section should go into your init.el file (or equivalent, such as config.el if you are using Doomemacs).

First, load the AucTeX package.

(require 'latex)

You will need to set the default TeX engine AucTeX uses to figure out the build commands to use Tectonic instead of traditional TeX distributions. Therefore we have to modify the TeX-engine-alist varible.

  • The first element of the list is the symbol that AucTeX recognizes.
  • The second element is a string with the name of the TeX distribution.
  • The third element is the shell command for compiling plain TeX documents.
  • The fourth element is the shell command for compiling LaTeX documents. Here we are assuming the user is using a Tectonic project (generated using tectonic -X new <proj-name>).
  • The last element is the shell command for compiling ConTeXt documents, left unconfigured for now.
(setq TeX-engine-alist '((default
                          "tectonic -X compile -f plain %T"
                          "tectonic -X watch"

Next, modify the LaTeX-command-style so that AucTex doesn't add extra options to it that Tectonic does not recognize. We simply set it to the %(latex) expansion (from TeX-expand-list-builtin), removing any other extra options.

(setq LaTeX-command-style '(("" "%(latex)")))

We need to set the TeX-check-TeX variable to nil since AucTeX will try to find a traditional distibution like TeXLive or others, and will fail since Tectonic doesn't meet it's criteria.

Additionally, we should also set TeX-process-asynchronous to t, so that running Tectonic in watch mode doesn't hang up Emacs.

We'll also just ensure that the TeX-engine is set to default.

(setq TeX-process-asynchronous t
      TeX-check-TeX nil
      TeX-engine 'default)

Finally, modify the TeX-command-list to use the appropriate commands, and not pass in extra metadata and options to Tectonic which cause it to error out. This needs to be done in place.

(let ((tex-list (assoc "TeX" TeX-command-list))
      (latex-list (assoc "LaTeX" TeX-command-list)))
  (setf (cadr tex-list) "%(tex)"
        (cadr latex-list) "%l"))

And that is all! You should now be able to

  1. Compile plain TeX files.
  2. Build Tectonic LaTeX projects in watch mode.

Additional Configuration and Usage Suggestions

Compile LaTeX outside a Tectonic project

To do this, you can simply invoke M-x TeX-command-master, and the select the Other option, passing in the compile command tectonic -X compile -f latex <name of file>.

Caution: Compiling a document with multiple LaTeX files in this manner isn't extensively tested, as using a Tectonic project is the better way in that case. Any bug reports are welcome.

Live PDF Preview in Tectonic projects

AucTeX expects the output PDF after compiling to be in the same directory as the input file. So it will error out when that is not the case, since Tectonic places the output in a build directory.

This behavior can be controlled by using the TeX-output-dir variable on a per project basis.

This configuration assumes you are using project.el, although porting this code to projectile.el should be trivial.

(add-hook 'after-change-major-mode-hook
          (lambda ()
            (when-let ((project (project-current))
                       (proot (project-root project)))
              (when (file-exists-p (expand-file-name "Tectonic.toml" proot))
                (setq-local TeX-output-dir (expand-file-name "build/index" proot))))))

We are basically looking for Tectonic.toml file in the project root, and if it exists, setting the TeX-output-dir to the appropriate path to the build directory. You may replace the "build/index" path to wherever your PDF file is placed after it is generated by Tectonic.