Mermaid’s default styling has become the visual signature of AI slop. You can spot an agent-generated diagram from across the room: purple boxes, drop shadows, that same tired arrow. diagram-design (cathrynlavery) is a Claude Code skill built specifically to kill that look — the README literally says “no shadows, no Mermaid-slop.”
What it actually is
Not an app, not an API. It’s a skill library you install into your coding agent (/plugin marketplace add cathrynlavery/diagram-design for Claude Code, also works in Codex and Pi). 29 editorial diagram types — architecture, sequence, swimlane, quadrant, Gantt, org chart, radar — output as self-contained HTML with embedded SVG. No dependencies, no render server.
Why it’s trending
9,052 stars, +2,951 in a single day, #1 AI repo on GitHub trending. The hook is a 60-second onboarding that scrapes your homepage for palette and font stack, then maps them onto all 29 types. Defaults are jet-black and atomic-tangerine on white-smoke paper with silver hairlines. It also imports existing draw.io and Mermaid files and converts them.
MIT licensed. Author is Cathryn Lavery, founder of BestSelf.co — a designer, not an infra engineer, which is exactly why it looks the way it does.
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