diagram-design

Wed, 12 Aug 2026 16:32:48 +0800

cathrynlavery/diagram-design

Diagram Design

Editorial diagrams your designer won’t hate.

New in 2.0 — the Loop: flywheels with a shared-memory hub. The dashed lines are the write-backs.

27 types. One agent skill for Claude Code, Codex, and Pi. Your brand in 60 seconds — the skill reads your website and maps colors + fonts to every diagram. Already have diagrams in draw.io or Mermaid? Point it at the source and it redraws them at the format, size, and level of detail your audience needs.

No Figma. No generic rounded boxes. No 30-minute color-picking sessions.

Why I built it

I write at littlemight.com (and run BestSelf.co on the side). Every time I needed a diagram — an architecture sketch, a flowchart, a pyramid of what matters most — I’d ask Claude and get back a generic rounded-box thing that looked nothing like the rest of the site. I’d either fight with Figma for 30 minutes or just skip the diagram.

So I built a Claude Code skill for it. Twenty-seven types, editorial quality, matches your brand in 60 seconds by reading your website.

The highest-quality move is usually deletion. Every node earns its place. The accent color is reserved for the 1–2 things the reader should look at first. Target density: 4/10.

What it makes

All 27 diagrams ship in three variants: minimal light, minimal dark, and full-editorial. Open any of them directly in a browser — no build step, no JS, no external images.

Architecture _{Components + connections}	Flowchart _{Decision logic}	Sequence _{Messages over time}
State machine _{States + transitions}	ER / data model _{Entities + fields}	Timeline _{Events on an axis}
Swimlane _{Cross-functional flow}	Quadrant _{Two-axis positioning}	Nested _{Hierarchy by containment}
Tree _{Parent → children}	Org chart _{Ownership + routing}	Venn _{Set overlap}
Layer stack _{Stacked abstractions}	Pyramid / funnel _{Ranked hierarchy or drop-off}	Consultant 2×2 _{Scenario matrix · named cells}
Radar / Spider _{Multi-axis comparison}	Loop _{Flywheel · stations around a hub}	IT current-state _{Legacy landscape · modernization}
High-Level _{End-to-end stack on a cluster}	Bar chart _{Categorical comparison}	Line chart _{Trends over time}
Gantt _{Tasks and phases on a timeline}	Scatter plot _{Distribution and correlation}	Process _{Multi-actor sequential workflow}
Medallion _{Multi-tier data storage}	Data flow _{Role-scoped pipeline steps}	DP integration _{Sources → core → consumers}
DP security matrix _{Per-role access permissions}

Browse the live gallery: open skills/diagram-design/assets/index.html in your browser to flip through all 27 diagrams with light / dark / full-editorial tabs.

Install

Pi:

`1`	`pi install https://github.com/cathrynlavery/diagram-design`

Run /reload in an open Pi session. Pi makes the skill available for matching diagram requests; use /skill:diagram-design to invoke it explicitly. Pi also loads the /export-diagram prompt template.

Claude Code:

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/plugin marketplace add cathrynlavery/diagram-design
/plugin install diagram-design@diagram-design

Claude Cowork: Customize → Directory → Plugins → + → paste cathrynlavery/diagram-design → Sync, then install from the Personal list.

Codex:

`1`	`npx skills add https://github.com/cathrynlavery/diagram-design --skill diagram-design`

Editable install

Managed installs are convenient, but changes to references/style-guide.md may be replaced by package updates. Clone the repo and install the local path if you plan to customize the style guide:

git clone git@github.com:cathrynlavery/diagram-design.git ~/code/diagram-design

# Pi: register the checkout as a local package
pi install ~/code/diagram-design

# Claude Code: symlink the inner skill
ln -s ~/code/diagram-design/skills/diagram-design ~/.claude/skills/diagram-design

The shared skill lives at skills/diagram-design/. Pi discovers it through the repo’s standard skills/ package directory; Claude Code, Codex, and other Agent Skills-compatible tools use the same files.

Onboarding — make it look like your brand

The whole point: ship editorial-quality diagrams in your colors and typography, not a generic template.

Out of the box, diagrams render in a clean jet-black + atomic-tangerine palette (white-smoke paper, jet-black ink, atomic-tangerine accent, blue-slate muted, silver hairlines). Good enough to screenshot straight away. But 60 seconds of onboarding is better — the skill will pull your brand from your website and apply it across every diagram.

The flow

You:     "onboard diagram-design to https://yoursite.com"
Agent:   → fetches the homepage
         → extracts the dominant palette + font stack
         → maps detected values to semantic roles:
             paper, ink, muted, accent, link
         → shows a proposed diff
         → writes your tokens to references/style-guide.md
You:     "yes, apply it"

Every new diagram now uses your colors. Your website’s paper color becomes the diagram background. Your CTA color becomes the focal accent. Your body font stack becomes the node label family.

What gets extracted

Detected from your site	Becomes
`<body>` background	`paper` token
Primary text color	`ink` token
Secondary / caption text	`muted` token
Cards or containers	`paper-2` token
Most-used brand color (CTA, link, heading)	`accent` token
`<h1>` font family	`title` font
`<body>` font family	`node-name` font
`<code>` / `<pre>` font	`sublabel` font

Contrast checks happen automatically

Before writing tokens, the skill verifies WCAG AA contrast on ink over paper. If your site has a color that fails contrast at diagram sizes (9–12px), it proposes an adjusted value and explains why.

Accessible by default

Every diagram template gives the inline SVG an accessible name and description: role="img", a resolving aria-labelledby, and first-child <title> / <desc> slots. IDs are prefixed per diagram and variant, so multiple SVG exports can be safely inlined on one page without duplicate accessible-name IDs. Decorative specimen icons are hidden from assistive technology instead.

Manual override

Prefer to set tokens by hand? Open skills/diagram-design/references/style-guide.md and edit the table. Everything downstream reads from there — all 27 diagrams, the annotation primitive, and the gallery all inherit semantic role names (accent, not #eb6c36).

First-run gate

The skill won’t silently ship default-skinned diagrams into a branded project. On first use in a new project, it checks if style-guide.md has been customized. If not, it pauses and asks:

“This is your first diagram in this project. The style guide is still at the default. Want to run onboarding, paste tokens manually, or proceed with default?”

See skills/diagram-design/references/onboarding.md for the full spec.

Quickstart

# From a cloned checkout, open the gallery to see all 27 diagrams
open skills/diagram-design/assets/index.html       # macOS
xdg-open skills/diagram-design/assets/index.html  # Linux

# In Claude Code, Codex, or Pi, ask:
# "Make me an architecture diagram of my app: frontend, backend, database, Redis cache."
# "I need a quadrant showing Q2 projects by impact vs effort."
# "Give me a sequence of a bearer call with token refresh on 401."
# (branching refresh uses the ALT combined-fragment grammar in type-sequence.md;
#  see skills/diagram-design/assets/example-sequence-oauth.html — not a full authorize-code handshake)

Your agent will pick the right type, build the HTML, and save it. You can also start from a template directly:

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cp skills/diagram-design/assets/template.html my-diagram.html        # minimal light
cp skills/diagram-design/assets/template-full.html my-diagram.html   # editorial with summary cards

Import from draw.io or Mermaid

Already have diagrams in draw.io / diagrams.net or Mermaid? Point the skill at the source and it redraws them — same content, this design system, at whatever the destination needs.

A 12-node draw.io file redrawn at balanced detail for a blog post. The source’s six pastel fills became one accent; its hand-dragged coordinates became a 4px grid.

/diagram-design:import platform.drawio
/diagram-design:import platform.drawio --size=slide-16x9 --detail=simplified --audience=executive
/diagram-design:import platform.drawio --detail=faithful --format=png --page=all
/diagram-design:import-mermaid README.md --diagram=all
/diagram-design:import-mermaid architecture.mmd --size=slide-16x9 --detail=simplified

Or just ask: “redraw this drawio file for my deck”, “make this Mermaid block editorial”, or “この Mermaid をスライド用にきれいにして”.

Reads the common containers draw.io writes — .drawio, .drawio.xml, .drawio.png (embedded diagram), and .drawio.svg — including compressed payloads that look like base64 garbage in an editor. For Mermaid, it accepts .mmd, .mermaid, and one or more fenced mermaid blocks in Markdown. It parses text only: no rendering, JavaScript, browser, network, or followed click targets.

The four dials

The point isn’t conversion, it’s fitting the output to where it’s going. Same source file, three different diagrams:

Dial	Options	What it changes
Format	`html` · `svg` · `png` · `html+png`	The deliverable. SVG for Figma, PNG for slides, HTML for the web.
Size	`doc-inline` · `doc-wide` · `slide-16x9` · `slide-4x3` · `social-og` · `social-square` · `print-a4-landscape` · `print-letter-landscape` · `fit`	The `viewBox` and the type ramp — a projected slide gets 16px node names, not 12px.
Detail	`faithful` (≤24 nodes, zoned) · `balanced` (≤12) · `simplified` (≤7)	How much of the source survives, via a fixed degrade ladder — decorations, then duplicates, then leaf clusters, then infrastructure.
Audience	`engineer` · `mixed` · `executive`	The wording, not the count. `Auth Service / JWT · RS256 · :8443` → `Auth Service / token check` → `Sign-in`.

Every import ends with a fidelity ledger — what got merged, collapsed, or dropped. You know the source; you’d notice anyway.

Detail: balanced · 12 source nodes → 8 drawn
Collapsed: "Token valid?" decision → edge label on Gateway → Auth
Dropped:   1 sticky note ("legacy path, to be retired") — unconnected in source
Kept in full: the request path (Web/Mobile → Gateway → Orders → Postgres)

What never carries over: source or renderer coordinates, source palette, source fonts, draw.io’s diagonal connector spaghetti, or Mermaid’s automatic layout. What always does: components, relationships, grouping, and direction. See references/import-drawio.md, references/import-mermaid.md, and references/output-spec.md.

Export to PNG / SVG

Diagrams ship as self-contained HTML, but you can export the diagram itself for Figma, slides, or social cards. Use the slash command for your agent:

Pi:

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/export-diagram path/to/diagram.html
/export-diagram path/to/diagram.html --svg-only
/export-diagram path/to/diagram.html --png-only --scale=3

Claude Code:

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/diagram-design:export path/to/diagram.html
/diagram-design:export path/to/diagram.html --svg-only
/diagram-design:export path/to/diagram.html --png-only --scale=3

Or just ask in natural language:

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"Export this diagram as SVG and PNG."
"Save my-diagram.html as PNG."

SVG — extracts the <svg> node and injects Google Fonts so it renders standalone in browsers, Figma, and Illustrator.
PNG — rasterizes the diagram via Playwright at 2× by default. One-time setup: pip install playwright && playwright install chromium.

Both formats are diagram-only — editorial cards and headers from -full variants aren’t included. For a screenshot of the full editorial layout, use your browser’s print-to-PDF or full-page screenshot. See skills/diagram-design/references/export.md for the full procedure.

Architecture

Progressive disclosure. SKILL.md is a lean index — it tells the agent how to pick a type and where to look for detail. Every type lives in its own reference file, loaded only when relevant.

diagram-design/
├── commands/
│   ├── export-diagram.md            — Claude Code export command
│   ├── import-drawio.md             — Claude Code draw.io import command
│   └── import-mermaid.md            — Claude Code Mermaid import command
├── prompts/
│   ├── export-diagram.md            — Pi `/export-diagram` prompt template
│   └── import-mermaid.md            — Pi Mermaid import prompt template
├── skills/
│   └── diagram-design/
│       ├── SKILL.md                 — philosophy, selection guide, checklist
│       ├── references/              — loaded only when a type or primitive is chosen
│       │   ├── style-guide.md       — single source of truth for colors + fonts
│       │   ├── onboarding.md        — the URL-to-tokens flow
│       │   ├── import-drawio.md     — draw.io redraw procedure
│       │   ├── import-mermaid.md    — Mermaid redraw procedure
│       │   ├── output-spec.md       — format × size × detail level
│       │   ├── export.md            — SVG / PNG export + sizing
│       │   ├── type-architecture.md
│       │   ├── type-flowchart.md
│       │   ├── type-sequence.md
│       │   ├── type-state.md
│       │   ├── type-er.md
│       │   ├── type-timeline.md
│       │   ├── type-swimlane.md
│       │   ├── type-quadrant.md
│       │   ├── type-nested.md
│       │   ├── type-tree.md
│       │   ├── type-org-chart.md
│       │   ├── type-layers.md
│       │   ├── type-venn.md
│       │   ├── type-pyramid.md
│       │   ├── primitive-annotation.md
│       │   ├── primitive-sketchy.md
│       │   └── primitive-terminal.md
│       ├── scripts/
│       │   ├── drawio_extract.py    — draw.io → structured IR
│       │   └── mermaid_extract.py   — Mermaid → structured IR
│       └── assets/
│           ├── index.html           — live gallery, tabbed
│           ├── template*.html       — scaffolds for new diagrams
│           ├── example-<type>.html  — 3 variants × 27 types
│           ├── example-loop-terminal.html
│           ├── example-quadrant-consultant.html
│           ├── example-import-drawio.html
│           ├── example-import-mermaid.html
│           └── example-sequence-oauth*.html
├── scripts/fixtures/
│   ├── sample-flowchart.mmd
│   ├── sample-readme-with-mermaid.md
│   └── sample-adversarial.mmd
└── docs/screenshots/                — images used in this README

This keeps the agent’s working context tight (only load what you need) and makes the skill easy to extend — drop a new type-<name>.md and wire it into the selection guide. The skill ships with 37 reference files covering every diagram type, primitive, and utility.

Contributing / skin lint

Before submitting a new example, run python3 scripts/lint-skin.py <your-new-example.html>. The repository-wide check python3 scripts/lint-skin.py --all --baseline must stay green. The linter’s a11y category rejects diagram SVGs without a resolving accessible name, an empty or misplaced title/description, or unsafe bare title / desc IDs. If you touch the draw.io import path, python3 scripts/verify-drawio-import.py must also pass — it drives the real extractor against scripts/fixtures/sample-architecture.drawio in all four container formats and checks the references stay in sync. If you touch the Mermaid import path, python3 scripts/verify-mermaid-import.py must also pass — it covers all supported grammars, multi-block Markdown, adversarial labels, trust-boundary behavior, resource caps, named failures, and reference/command wiring.

All pull requests and pushes are automatically validated via GitHub Actions CI (.github/workflows/ci.yml).

What loads when

At startup, the agent sees only the skill name and description. When a request matches, it loads SKILL.md; type references are pulled in only when relevant. This keeps the skill fast even with 37 reference files.

You ask for…	Agent loads
“Make me a flowchart”	`SKILL.md` + `references/type-flowchart.md`
“Build an architecture diagram”	`SKILL.md` + `references/type-architecture.md`
“Onboard this skill to my site”	`SKILL.md` + `references/onboarding.md` + `references/style-guide.md`
“Add an editorial callout to this diagram”	`SKILL.md` + `references/primitive-annotation.md`
“Give me a hand-drawn version”	`SKILL.md` + `references/primitive-sketchy.md`
“Give me a terminal / CLI-window version”	`SKILL.md` + `references/primitive-terminal.md`
“Redraw this .drawio file for my deck”	`SKILL.md` + `references/import-drawio.md` + `references/output-spec.md` + the chosen type’s reference
“Redraw this Mermaid block for my deck”	`SKILL.md` + `references/import-mermaid.md` + `references/output-spec.md` + the chosen type’s reference
Routine diagram-making (any of the 27 diagrams)	Only `SKILL.md` + that one type’s reference

No matter how many types exist, the agent only reads the one you need. Add a new type tomorrow and nothing else changes.

The design system (in one paragraph)

One accent color, 1–2 focal elements per diagram. Three font families: Instrument Serif (title + italic callouts), Geist sans (node names), Geist Mono (technical sublabels). 1px hairline borders, no shadows, max border-radius 10px. Every coord, width, and gap divisible by 4 — non-negotiable, it’s what keeps the diagrams from feeling AI-generated. Mono is for technical content (ports, URLs, field types), not a blanket “dev” aesthetic. Coral-tinted focal nodes draw the eye to the 1–2 things that matter. Full spec in SKILL.md.

Primitives

Annotation callout — italic Instrument Serif + dashed Bézier leader, for editorial asides that sit in the margins. See skills/diagram-design/references/primitive-annotation.md.
Sketchy filter — SVG turbulence + displacement map for a hand-drawn variant. Good for essays, not for technical docs. See skills/diagram-design/references/primitive-sketchy.md.
Icon set — 55 monochrome IT/cloud icons (laptop, phone, user, server, database, Docker, Kubernetes, AWS, Azure, GitHub, Postgres…) for richer architecture and sequence diagrams. Stroked icons from Tabler Icons (MIT); brand silhouettes from Simple Icons (CC0). Each icon uses currentColor so it inherits the editorial skin or your onboarded brand. See skills/diagram-design/references/primitive-icons.md; browse the gallery. Regenerate with python scripts/build-icons.py.

When not to use this skill

Quick unicode diagrams for tweets or terminal output → wiretext-style skill.
Lists of anything → a table or bullets.
Before/after comparisons → a table.
One-shape “diagrams” — a single box with a label → just write the sentence.

Before drawing, ask: would a reader learn more from this than from a well-written paragraph? If no, don’t draw.

About

Made by Cathryn Lavery — founder of BestSelf.co. I write about AI, entrepreneurship, and designing nice-looking things at littlemight.com — blog + newsletter.

If this is useful, star the repo and come say hi on X.

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