Diagram Design Passes 47,900 Stars, and Its README Tells Git Users to Pick Mermaid

Diagram Design, an agent skill that draws editorial diagrams as one HTML file, has 47.9k GitHub stars, and its own README tells anyone whose diagrams live in Git to use Mermaid instead.

The repository, cathrynlavery/diagram-design, is by Cathryn Lavery and uses the MIT licence. GitHub's trending list showed it gaining 1,739 stars on October 10. It had 3.0k forks, 271 commits on main, 20 open issues and 61 open pull requests when read.

What it produces and how it installs

The skill runs inside Claude Code, Codex, GitHub Copilot, Cursor and other hosts that read the Agent Skills format. Install is npx skills add cathrynlavery/diagram-design, and Claude Code, Codex, Copilot, Factory Droid and Pi each have their own marketplace command.

Output is a single .html file that opens offline in a browser. It can be exported to SVG or to PNG, rendered through Playwright at 2x by default. The skill can also redraw existing draw.io, Mermaid and Excalidraw files.

The README lists 44 diagram types, from architecture and sequence to Sankey, Wardley map and fishbone, each in minimal light, minimal dark and full-editorial variants. The repository sidebar says 42, so the project disagrees with itself by two.

The README argues against its own use case

Most viral skills repos sell. This one carries two admissions. The first reads: "Output quality depends on the model you run it with, and the same prompt can lay out differently twice." The second says the output has "no text to diff in a pull request and no canvas to drag a box on."

For diagrams that live in Git and change often, the README says "Mermaid is still the better fit." That is a fair verdict. Mermaid is MIT-licensed, describes itself as generating diagrams "from text in a similar manner as markdown," and had 90.6k stars and 9.3k forks.

1. mermaid-js/mermaid90.6 thousand stars
2. cathrynlavery/diagram-design47.9 thousand stars

Source: GitHub repository pages for mermaid-js/mermaid and cathrynlavery/diagram-design, read Oct. 10, 2026

Stars are not adoption. They record a click, not a diagram in a pull request.

Five export and checker items filed on October 6

The open issues show where a generated-HTML pipeline strains. Five items were filed on October 6 and are about export and checking, the step that turns the agent's drawing into a file someone can ship. One of them, #306, is titled as a fix.

Issue	Filed	Problem, in the issue's words
#299	Oct 6	"PNG export rejects the fractional scale documented for exact pixel sizes"
#289	Oct 6	"SVG export applies print-only diagram CSS during screen rendering"
#288	Oct 6	"SVG export rejects valid rgba paint with separate presentation opacity"
#291	Oct 6	"Treemap verifier reads a numeric suffix instead of the printed percentage"
#306	Oct 6	"fix(geometry): exclude SVG definitions from painted shape checks"

A sixth, #209 from September 10, reports that the Mermaid extractor rejects a compact label containing whitespace, which touches the redraw feature the README advertises. None of the 20 open issues on the page is described as a security or licensing problem.

What to read next in the same pile

The issue list also holds a policy question, #262 from September 28, titled "Unattended runs: explicit path through the §0 style gate," which asks how the skill should behave when no human approves the style step. A request filed October 9 asks whether the author plans to support Cursor, even though the README lists Cursor among compatible hosts. Both read as users probing the edges of a rule set that is still being written.

The pattern matches other trending skill collections this site has covered, such as Matt Pocock's agent skills and the Impeccable design detector. The test for Diagram Design is a diagram you must regenerate next month: if the layout changes between runs, as the README admits it can, the file stops being a record. The 61 open pull requests are the number to watch.