Mermaid makes pretty diagrams from text. It's Javascript-based, so the command-line tool (mmdc) uses Puppeteer to get the results of evaluating the diagram in the browser. I was running into some errors trying to get it to work from Org Mode over ob-mermaid on Ubuntu 24, since apparently AppArmor restricts Puppeteer. (Error: Failed to launch the browser process! · Issue #730 · mermaid-js/mermaid-cli).

I put together a pull request to modify ob-mermaid-cli-path so that it doesn't get quoted and can therefore have the aa-exec command needed to work around that. With that modified org-babel-execute:mermaid, I can then configure ob-mermaid like this:

(use-package ob-mermaid
  :load-path "~/vendor/ob-mermaid")
;; I need to override this so that the executable isn't quoted
(setq ob-mermaid-cli-path "aa-exec --profile chrome mmdc -c ~/.config/mermaid/config.json")

I also ran into a problem where the library that Emacs uses to display SVGs could not handle the foreignObject elements used for the labels. mermaid missing text in svg · Issue #112 · mermaid-js/mermaid-cli . Using the following ~/.config/mermaid/config.json fixed it, and I put the option in the ob-mermaid-cli-path above so that it always gets loaded.

{
  "flowchart": {
    "useMaxWidth": false,
    "htmlLabels": false
  }
}

Here's sample Mermaid markup and the file it creates:

mindmap
  root((test))
    Node 1
      Node 1A
      Node 1B
    Node 2
    Node 3

Now I can see the labeled diagrams inside Emacs, too.