diagram-design: An Open-Source Claude Code Plugin That Auto-Generates Architecture Diagrams

Sometimes the fastest way to explain something is to stop writing and start drawing. Three paragraphs nobody reads versus three boxes everyone understands — that gap is exactly what diagrams are for.

Why Diagrams Still Matter

The Tokyo Metro map is a perfect example. The same information in text would run dozens of pages and still be impossible to follow. A diagram communicates "this connects to that" in a single glance. Metro maps, org charts, and software architecture diagrams all work the same way: boxes, arrows, and just enough labels.

How We Made Diagrams Before AI

Before AI tools became widespread, Miro, draw.io, and Figma were the go-to platforms. You drew a box, labelled the arrow, built the flow manually. Time-consuming, but you had full control over the result.

With AI, you can now ask Claude to generate a diagram directly. That works — but it comes with real practical problems:

• Color mismatch: The output doesn't match your project's brand palette.
• Arrow clutter: Arrows overlap, making the flow hard to trace.
• Layout issues: Labels spill outside boxes, visual hierarchy breaks down.

Fixing each of these is extra effort that defeats the purpose.

What diagram-design Does Differently

diagram-design is a free, MIT-licensed, open-source plugin for Claude Code. It addresses those problems in three concrete ways:

1. Pulls brand colors automatically. It reads your site or project files and applies your color palette to the diagram. The output looks like it belongs to your project.
2. Reads your codebase and infers the architecture. You don't have to explain the structure manually — the plugin analyzes component relationships on its own.
3. Produces consistent output every time. Arrows don't overlap, labels are correctly placed, and a clean legend appears at the bottom of the diagram.

The video places two outputs side by side: one generated by asking Claude from scratch, the other produced by the diagram-design plugin. The difference is visible immediately — the plugin output is cleaner, with no overlapping arrows and a properly formatted legend.

Diagram Types

The repo isn't limited to architecture diagrams. It includes templates for different diagram types, and once added as a Claude Code skill, it selects the appropriate type based on your project's needs.

You Learn by Doing

What makes this tool worth trying isn't just the feature set. The real point is simpler: if you're presenting a system to someone unfamiliar with it, visual clarity is everything. A clean diagram that communicates the flow at a glance outperforms a long document every time.

Learning to work with AI tools requires hands-on experimentation. You won't get there by reading about it — you get there by running a prompt and looking at what comes back. diagram-design offers exactly that kind of low-friction starting point: free, open source, and immediately usable.

Find the repo on GitHub at cathrynlavery/diagram-design.