Licensing & updates

Last updated: 1 September 2026

Diagon is a subscription with a full 30-day trial in front of it. This page says exactly what that means: what the trial includes, what a licence key is, what happens the day it expires, and how updates arrive.

The short version: the trial is the whole app for 30 days with no account and no card; a subscription is €4.99 a month or €49.90 a year; and when neither is running, Diagon locks — but your diagrams are plain text files that stay yours either way.

The trial

Every install starts a 30-day trial on first launch. There's nothing to sign up for and nothing to enter.

Everything is unlocked: the editor, containers, SVG and PNG export, and the AI, with no per-run limit and no reduced free tier underneath. What you're trying is the product.

Help → Licence… shows how much is left, as Trial — 12 of 30 trial days left. The ✨ Generate panel shows the same line while the trial runs.

A few mechanics, stated plainly because they're the kind of thing people would rather read than discover:

• The trial's start date is kept in two small JSON files — one in Diagon's own data folder, one in a .diagon folder in your home directory. Deleting one doesn't restart the trial; the app heals the missing copy from the other. They're readable text, not DRM, and the code that writes them says as much.
• Winding your system clock backwards freezes the trial rather than extending it. Diagon uses the later of your clock and the last day it saw, so days already spent stay spent.

Subscribing

Subscriptions are at soverain.cz/diagon — €4.99 monthly, or €49.90 yearly, which is two months free. Cancel any time.

After you subscribe, a licence key arrives by email. It looks like this:

SOVR1.eyJ2IjoxLCJwcm9kdWN0Ijoi….Zk9sN3E…

Paste it into Help → Licence… and press Activate, or into the lock screen if the trial has already run out. It unlocks the app immediately — no restart.

The key is checked offline. It carries a signature Diagon verifies against a public key built into the app, so activation works with no network at all. There's no activation server and no phone-home at start-up.

Once activated, the licence panel reads back what it knows: the email the subscription belongs to, the date it's unlocked through, and whether renewal is due.

What a key covers

A key carries an expiry date and the email it was issued to. It's good through the whole of its expiry date — a key expiring on the 30th works all day on the 30th and stops on the 31st.

That date is the end of the period you paid for plus a three-day grace window, so a card that needs a retry doesn't lock a paying customer out.

Automatic renewal

You paste your key once. After that Diagon keeps it current on its own.

It checks at start-up and once a day, but only inside the last 14 days before expiry, or after a key has lapsed — the rest of the time it does nothing. A check sends your current key to soverain.cz and nothing else, and it accepts a replacement only if that replacement passes the same offline signature check.

Being offline is not a failure. If the check can't reach the server, your stored key is left exactly as it is and the app says so calmly: Couldn't reach soverain.cz — check again when you're online. The same is true if the server answers that there's no renewal yet.

Check now, in the licence panel, runs the check immediately and ignores the 14-day window — useful right after renewing.

The one thing renewal needs is for your machine to be online at some point in that final fortnight. A computer that's been offline for a month will hit its expiry date and lock until it can check in or you paste a new key.

When it expires

When the trial ends and no subscription is running — or when a subscription lapses — Diagon locks behind a full-window screen. It reads Your 30-day trial has ended or Your subscription has ended, with the date your last paid period ran to, and offers three things: Subscribe, Enter licence key, and Check now.

This is a hard lock. The editor is disabled behind it, and there's no reduced mode and no older version that keeps running. When the subscription ends, so does your licence to run the app.

Two deliberate exceptions:

• Save and Save As keep working from behind the lock screen. Nothing you made during the trial is ever trapped inside the app.
• Your files are untouched. Diagrams are .diag text files on your own disk. They open in any editor, in or out of subscription, forever. The app needs a licence; your documents never do.

Unlocking takes effect at once. Paste a valid key and the screen comes down — no restart. If a renewal lands in the background while the lock screen is up, that unlocks it too, and the app re-checks the gate every few minutes, so a trial running out while you're working raises the screen on its own rather than waiting for a restart.

An expired key isn't deleted. It stays stored so a later renewal can revive it, which is why Check now on the lock screen is worth a try after you've renewed. To remove a key deliberately, use the licence panel.

Machine-locked complimentary licences

Some keys we issue by hand — review copies, complimentary licences — are bound to one computer. Bought subscriptions never are.

A bound key carries a machine code. Diagon derives that code locally from your operating system's installation identifier, hashed; the raw identifier never leaves your machine and nothing about your hardware is transmitted. Your code is shown in Help → Licence… in the form A1B2-C3D4-E5F6 — that's what to send us when asking for a bound key.

A bound key used on a different computer is refused, at activation and at every later check, with this key is locked to a different computer. A machine that exposes no stable identifier can't prove the binding, so a bound key is refused there too. Unbound keys never run into any of this.

Updates

Diagon checks for updates 15 seconds after launch and every six hours after that. It downloads in the background and installs when you quit. A small toast with a Restart now button appears only once an update is ready — nothing interrupts you while it's downloading.

Help → Check for updates… runs a check now and shows the intermediate states.

The Windows updater downloads differentially, so an update that doesn't touch the AI model fetches a fraction of the 2 GB rather than all of it. On .deb, Check for updates… answers that this install updates via the download page.

The only thing an update check sends is the request for release information from GitHub, where the packages are published. Nothing about your machine, your licence or your diagrams goes with it.

Updates are included for as long as your subscription is active.

Code signing

Windows installers from 1.1.0 on are code-signed by Soverain s.r.o. through Azure Trusted Signing. SmartScreen may still show a notice while the certificate builds reputation — choose More info, then Run anyway. You can check the signature yourself: right-click the installer, Properties → Digital Signatures, and the signer should read Soverain s.r.o.

Refunds and cancellation

Ask for a refund within 14 days of a charge — your first payment or any renewal — and you'll get one, no questions. The full terms are in the refund policy, and the EULA covers what you may do with the app.

To stop future charges without a refund, cancel; your access runs to the end of the period you've already paid for.

Anything unclear, or a key that won't activate: hello@soverain.cz. Include your machine code from the licence panel if it's an activation problem.

Related

• Getting started — install and first diagram.
• The editor — the app you're subscribing to.
• AI drafting — included at no extra cost, with no run limit.