Terms of Service

1. The agreement

These terms are between you and Quiet Grid Labs co. ("Quiet Grid Labs", "we", "us"), registered at Žemaitės gatvė 5c, Vilnius, Lithuania, and they cover your use of Viaduct — the web application at c4.quietgridlabs.com, the hosted MCP server at mcp.quietgridlabs.com, and everything we publish alongside them.

By creating an account, signing in, or using the local editor you accept these terms. If you are accepting them for a company, you confirm you may bind that company.

2. What the service does

Viaduct is a modelling tool for software architecture: C4 diagrams, documentation and sequence diagrams attached to elements, API contracts, and an MCP server that lets AI development tools read and write that model on your behalf.

You can also use the editor without an account. In that mode the model stays in your browser and is never sent to our servers; clearing your browser data deletes it, and we cannot recover it.

3. Accounts

An account is created through Google, GitHub, or the GitLab we run at git.quietgridlabs.com. Each of those is a separate account here even when the email address on them is the same — signing in with a different provider puts you in a different workspace, not the same one, and there is no way to merge them.

You are responsible for what happens under your account and for any personal access token you issue for the MCP server. Tell us at once if you believe a token or an account has been compromised; you can revoke tokens yourself at any time.

You must be old enough to enter into a contract where you live.

4. Your content

Your models, documentation, diagrams and files remain yours. We claim no ownership of them.

You grant us the limited licence needed to run the service: to store your content, to display it back to you and to the people you share it with, to back it up, and to process it when an AI tool you have connected asks for it through the MCP server.

You are responsible for having the right to upload what you upload, and for anything you choose to share by link. A share link works until you revoke it, so treat it as you would the content behind it.

5. Acceptable use

Do not use Viaduct to:

• break the law, or infringe anyone’s rights;
• store or distribute malware, or content you have no right to;
• attack, probe or overload the service, or work around its limits and access controls;
• resell or rebrand the hosted service as your own;
• automate use in a way that degrades the service for other people.

We may suspend an account that does any of these, and will say why where we lawfully can.

6. Availability and changes

We work to keep the service up but do not promise uninterrupted availability, and there is no service level agreement unless we have signed one with you separately. Maintenance, incidents and third-party outages happen.

We may add, change or withdraw features. If we withdraw something you depend on we will give reasonable notice and, where we can, a way to take your work with you — the model exports as JSON and the contracts as OpenAPI at any time.

7. Fees

Viaduct is free to use. There is no paid plan, no trial that ends, and no feature held back behind one.

You may donate if you want the work to continue — through Stripe from the EU or the US, or through CloudTips from Russia. Both are external services: you leave this site to pay, and we never see your card. A donation buys nothing — no support commitment, no feature, no priority — and it is not refundable through us.

If that ever changes and part of the service becomes paid, we will say so in the application before it applies, and nothing you already have will be locked behind the change without notice.

8. Ending the agreement

You may stop using Viaduct at any time, and ask us to delete your account by writing to support@quietgridlabs.com.

We may terminate or suspend an account for a material breach of these terms, or if we stop offering the service. On termination we delete your content according to the retention periods in the Privacy Policy — export anything you want to keep first.

9. Warranties

The service is provided "as is" and "as available". To the extent the law allows, we disclaim implied warranties of merchantability, fitness for a particular purpose and non-infringement.

Where you deal with us as a consumer, nothing in this section affects your statutory rights.

10. Liability

To the extent the law allows, we are not liable for indirect or consequential loss, loss of profit, or loss of data beyond our obligation to keep the backups described in the Privacy Policy.

Where we are liable, our total liability for all claims arising in any twelve-month period is capped at €100. The service is free, so there is no fee to measure it against; the cap is a fixed sum instead.

Nothing here limits liability for death or personal injury caused by negligence, for fraud, or for anything else that cannot lawfully be limited.

11. Changes to these terms

We may update these terms; the date at the top of this page always says when. If a change materially reduces your rights we will give notice in the application or by email before it takes effect, and using the service after that date means you accept the new terms.

12. Governing law

These terms are governed by the law of the Republic of Lithuania, and the courts of Vilnius have exclusive jurisdiction — without affecting any mandatory protection you have as a consumer where you live.

13. Contact

Questions about these terms: support@quietgridlabs.com, or by post to Quiet Grid Labs co., Žemaitės gatvė 5c, Vilnius, Lithuania.