An idle game asks the player to trust that progress will still exist tomorrow. A browser game adds another complication: tomorrow might begin on a phone, continue on a desktop, and end with two tabs that both believe they are in charge.
The Unfinished Kingdom keeps combat on the player's device, but protected accounts also maintain a cloud checkpoint. Each accepted checkpoint receives a revision number. When the browser sends the next update, it must name the revision it started from. An older tab cannot quietly overwrite newer progress because its revision no longer matches.
Recovery needs more than an error message
Rejecting an old revision is only half the job. When newer protected progress exists, the game retrieves the authoritative save, preserves the displaced local copy as a recovery record, updates its revision, and resumes from a known state. If the browser already has the same save and only missed the server response, it can refresh the revision without replacing the Warden.
That distinction matters on unreliable connections. A request can succeed on the server even when the response never reaches the browser. Treating every timeout as a failed save would create false conflicts and repeated rewards.
Devices and tabs are different problems
Only one device may control a protected Warden. Taking control on another device requires a new email code and loads the latest accepted cloud checkpoint. The previous device stops advancing and explains that control moved elsewhere.
Two tabs in the same browser need a faster answer. They share the same account session, so asking for another email code would not solve the real problem. The game now elects one active tab locally. Other tabs pause and can become active only through an explicit action that warns the player their displayed numbers may be older.
Trust is part of progression
The server does not simulate every sword swing. It checks ownership, revisions, elapsed time, important rewards, and the active control lease. The browser keeps combat responsive while the server protects the points where progress can split or be duplicated.
None of this makes the next Bellkeeper easier. It makes closing the browser less frightening. For a game built around continuous progress, that trust is part of the game system.