Getting started

Last updated: 1 September 2026

Diagon is a desktop app where a diagram is a text file. You write objects and arrows on the left, and the layout engine draws them on the right while you type. Drag a node in a flat diagram and its position is written back into your code.

It runs entirely on your machine. The AI that drafts diagrams from a sentence is bundled inside the app — there's no account to make and no server to call.

This page gets Diagon installed and gets you through your first diagram. After that, The language is the full syntax reference, The editor covers the canvas and export, AI drafting covers the ✨ Generate panel, and Licensing & updates covers the trial and subscription.

What you need

Windows 10 or 11 (64-bit), or a modern 64-bit Linux distribution. macOS isn't available yet.
About 8 GB of RAM. Diagon runs fine on less, but the bundled AI model is happier with room.
Roughly 2 GB of disk for the download and about the same again once installed.

The download is large because the AI model ships inside the package rather than living on someone else's server. Nothing else about the app is heavy.

Download

The download page is the single source of truth for the current version, the exact file names and their sizes: a Windows installer, a Linux AppImage and a Debian/Ubuntu .deb. Take the one for your platform from there. What follows is only what each package does once you have it, which doesn't change between versions.

Windows

The Windows package is an NSIS installer. This build isn't code-signed yet, so SmartScreen may warn you that the app is new — choose More info, then Run anyway.

The installer isn't one-click: it asks where to put Diagon, installs for the current user only (no administrator prompt), and creates a desktop and Start-menu shortcut called Diagon.

Linux, AppImage

No installation and no root — make the file executable and run it:

bash

chmod +x Diagon-*.AppImage
./Diagon-*.AppImage

On Ubuntu 22.04 and later you may need FUSE once:

bash

sudo apt install libfuse2

Linux, Debian and Ubuntu

The .deb installs system-wide:

bash

sudo apt install ./diagon_*_amd64.deb

Then launch Diagon from your application menu. One thing to know up front: .deb installs don't update themselves. Windows and the AppImage do. If you're on the .deb, you'll download a new package when a version ships — see Licensing & updates.

First launch

Diagon opens with a starter diagram already in the editor so there's something to look at:

diagon

# Diagon — diagrams as code
# Edit on the left; drag any node to pin its position (written back here).
direction: down
routing: curved

start: Start { shape: pill, fill: #1f6f43 }
collect: Collect input
valid: Valid? { shape: diamond, fill: #6b4f1d }
save: Save to DB { shape: cylinder }
retry: Show error { fill: #5a2230 }
done: Done { shape: pill, fill: #1f6f43 }

start -> collect
collect -> valid
valid -> save: yes
valid -> retry: no
retry -> collect
save -> done

The window has three parts. The toolbar across the top holds file actions, view controls and export. The code pane on the left is a plain text editor with a line-number gutter and a red error bar under it when something doesn't parse. The preview on the right is the diagram — scroll to zoom, drag the background to pan, drag a node to move it.

The drag handle between the two panes resizes them.

Your first diagram

Press Ctrl+N for an empty file and type this:

diagon

# my first diagram
idea: An idea
draft: A draft
ship: Shipped

idea -> draft: write it down
draft -> ship: review

Three things happened. idea: An idea declared a node with the id idea and the label An idea. idea -> draft: write it down drew an arrow with a label on it. And the layout engine decided where everything goes — you never place anything by hand unless you want to.

The status line in the top right reads something like 3 nodes · 2 edges · 4ms while it works. If it reads 1 issue, look at the red bar under the code for the line number and the reason.

Now give the nodes some shape:

diagon

direction: right

start: Start { shape: pill, fill: #1f6f43 }
check: Looks right? { shape: diamond }
ship: Ship it { shape: pill, fill: #1f6f43 }

start -> check
check -> ship: yes
check -> start: no

direction: right flows the diagram left-to-right instead of top-down. The braces hold attributes — shape, colour, an icon URL, a fixed position. There are seven shapes and a handful of attributes; they're all listed in The language.

Note the comment style: a comment is a whole line starting with # or //. A # partway through a line isn't a comment — it becomes part of your label, and on a direction: or routing: line it breaks the directive.

Saving and exporting

Ctrl+S saves a plain UTF-8 text file, .diag by default. That file is the diagram. It opens in any editor, diffs cleanly in git, and doesn't need Diagon to stay readable.

Export SVG and Export PNG are on the toolbar and in the File menu. SVG comes out standalone with the styling embedded; PNG is rasterised at 2× on the current theme's background. Both crop tight to the drawing.

Try the AI

Click ✨ Generate, describe what you want in plain words, and press Generate. The model runs on your machine — the first run takes a few seconds while it loads, after that it's quicker.

If the editor already holds a working diagram, the panel switches to editing mode and applies your sentence as a change instead of starting over. AI drafting explains both modes and their limits.

The trial

Every install starts a 30-day free trial on first launch. No account, no card, no feature held back — exports, containers, the AI, all of it, with no run limits.

When the 30 days are up, Diagon locks behind a screen offering a subscription or a licence key. Save and Save As keep working there, so nothing you made during the trial gets trapped. Your .diag files are yours regardless.

Licensing & updates has the details: what a key is, how renewal works, and what happens on expiry.

Where next

The language — every statement, shape, attribute and container rule.
The editor — dragging, pinning, routing, export, and the full shortcut list.
AI drafting — the ✨ Generate panel and the model behind it.
Licensing & updates — trial, keys, renewal, updates.

Stuck on something? Email hello@soverain.cz.