How to use
- Copy the installation command and review the source package before installing it in your own agent environment.
- Check the source document for required tools, credentials and supported hosts.
- Describe your input and desired deliverable; review the output against the source material.
npx skills add https://github.com/bostonaholic/skills --skill drawing-mermaid-diagramsBefore you start
- Installation does not include a model subscription, API allowance or permission to access your files.
- Repository stars and installation counts describe activity, not an independent quality or security test.
Rendered from the source repository. Headings, examples, code, tables, links, and referenced images are preserved.
Mermaid Diagrams
A diagram is done when it renders without error and its layout reads clearly. Pick the type that matches the content (process, messages, schema, schedule, hierarchy, and so on); a flowchart is not the answer to everything.
Renderer support
Each host (GitHub, GitLab, a docs site, an IDE preview) bundles its own Mermaid release, often older than the latest. -beta keywords (xychart-beta, sankey-beta, architecture-beta, block-beta) and recent types such as kanban may fail there. When the target renderer is unknown, prefer a core type, or ask which renderer will display the diagram.
Default to a frontmatter config: block before the diagram keyword. Fall back to a first-line %%{init: {...}}%% directive only for a renderer too old to read frontmatter config.
Validate by rendering
Write the diagram to <out>/diagram.mmd in a scratch directory and render it:
npx -y @mermaid-js/mermaid-cli -i <out>/diagram.mmd -o <out>/diagram.pngFor a Markdown file, -i doc.md -o <out>/doc.md renders every mermaid block. Fix each Parse error on line N or Lexical error and render again until it succeeds. When layout matters, open the PNG and check direction, overlaps, and label text. Only then put the code in its destination.
If mmdc cannot find Chrome, write {"executablePath": "<path to an installed Chrome or Chromium>"} to <out>/puppeteer.json and add -p <out>/puppeteer.json. If Node, network, or a browser is unavailable, do not install one without asking; check the diagram against the gotchas below and tell the user it was not rendered.
A successful CLI render uses the Mermaid release bundled with the CLI, so it does not prove an older host renders the diagram.
Gotchas
Several of these fail silently rather than with a parse error.
- Labels containing
(),[],{},:,;, or#are wrapped in
"..."; inner quotes are written #quot;, < and > as #lt; and #gt;.
- A lowercase
endas a flowchart node ID or bare label breaks the parse; use
End or ["end"].
- A node ID beginning with
oorxright after a link (A---oB) silently
becomes a circle or cross edge; add a space or capitalize.
%%comments sit on their own line; a trailing comment is a parse error.- Block diagrams have no
==>or:::shorthand. - Indentation is significant in
mindmapandkanban. - Styling not applying: the config block must come first,
themeVariables
need theme: base, and hex colors in frontmatter must be quoted (an unquoted # is a YAML comment and the color is silently dropped).
- Renders in the CLI but not on the host: the host's Mermaid is older; replace
a -beta or recent type, or switch frontmatter config to %%{init}.
