Legal

Terms of Use

Last updated 16 October 2026

1. Who we are and these terms

Kosumi is an app for learning and playing the board game Go, operated by Synton.ai LLC. By using Kosumi you agree to these terms and to Apple's Licensed Application End User License Agreement (the "Apple EULA"). Where these terms and the Apple EULA differ, these terms apply to the extent allowed.

2. Your account

Lessons, problems and games against the AI can be used without an account. Online play requires Sign in with Apple. Keep your device secure; you are responsible for activity on your account. You can delete your account at any time.

3. Kosumi Premium subscriptions

• Kosumi Premium is an auto-renewing subscription, offered monthly ($4.99) or yearly ($39.99), or the equivalent in your local currency as shown in the App Store.
• The yearly plan may include a 7-day free trial for new subscribers. If you don't cancel at least 24 hours before the trial ends, the yearly subscription starts and is charged.
• Payment is charged to your Apple ID at confirmation of purchase. The subscription renews automatically at the same price and period unless auto-renew is turned off at least 24 hours before the end of the current period. Your account is charged for renewal within the 24 hours before the period ends.
• Manage or cancel your subscription in your Apple ID settings (Settings › your name › Subscriptions). Cancelling stops future renewals; you keep Premium until the end of the period you paid for.
• Any unused part of a free trial is forfeited when you buy a subscription. Refunds are handled by Apple under its policies.
• We may change prices or what Premium includes; price changes follow Apple's rules and are announced in advance.

4. Fair play

Rated games are between people. In rated games you must not use any outside assistance: no Go engines or analysis tools (including Kosumi's own hints or review on another device), no help from another person, no consulting books or databases during the game. You must not manipulate ratings, for example by losing on purpose, playing against your own second account or arranging results.

We check games for signs of engine assistance and other abuse. We may annul results, adjust ratings, and suspend or ban accounts that break these rules, at our discretion. Unrated games against bots and the coach are, of course, yours to use as you like.

5. Conduct

Choose a nickname that isn't offensive, misleading or someone else's. Don't harass other players, stall clocks to annoy, abandon games repeatedly or misuse reports. We may change nicknames, limit features or close accounts that do.

6. The coach and the AI

Engine evaluations, hints and written explanations are there to help you learn. They are generated automatically and may occasionally be imprecise. Explanations are written by an AI model from KataGo's analysis.

7. Content and licences

The app, its lessons, design and text are owned by Synton.ai LLC and licensed to you for personal, non-commercial use. Kosumi uses KataGo by David J. Wu, released under the MIT License, together with its published neural networks under their respective licences. Classic problem collections included in the app are in the public domain. Full licence notices are available in the app under Settings › Licences.

You keep the rights to your games. You give us permission to store and show your online games to your opponents and, in anonymised form, to other players (for example in game histories and ratings).

8. No warranty and limitation of liability

Kosumi is provided "as is" and "as available", without warranty of any kind. Online play depends on network connections and servers, which may occasionally be unavailable; we are not responsible for games or ratings affected by outages, though we may annul affected games. To the maximum extent permitted by law, Synton.ai LLC is not liable for indirect or consequential damages, and its total liability is limited to the amount you paid for Kosumi in the 12 months before the claim. Nothing in these terms limits rights or liability that cannot be limited by law.

9. Changes and ending

We may update these terms; the app will ask you to accept material changes. You can stop using Kosumi at any time. We may suspend or end access for breaches of these terms.

10. Law

These terms are governed by the laws of the State of Wyoming, USA, without affecting mandatory consumer protections in your country of residence.

Questions: hello@kosumi.app · Privacy: privacy@kosumi.app