This is a compromise between usability and performance and is by design.

> It seems to me that these numbers are set in browsers as cookies, so they are not synced across different browsers running under the same account. In my opinion, these numbers should be "attached" to the account instead, so I always see the true number no matter which browser or device I use.

That's correct, TopAnswers [uses localStorage](/meta?q=974) to "help keep track of unread message counts when you participate in chat".

If we instead stored this on the database then there would be a lot of  extra writes (state changes). We don't think this would scale well if we end up with thousands of users. For example, if one person posts a chat in a high traffic room, all others who have that room open in a tab would need to immediately perform a database write to persist the fact that the message has been viewed. That could be a large amplification of the the initial single write.

However, what you may not know, and may find useful: the 'read chat' info is **pushed to the database whenever you post a chat message**. If you do that in Brave, the next time Edge polls or you navigate to another page, it will have the updated counts — so at least for a moment they will be in sync.

> Interestingly, notifications seem to work well: if I have marked a notification as read in Brave, there are no notifications reported in Edge (or at least it appears to me so).

That's also correct — dismissing a notification is not going to cause the same scaling issue (there is no amplification) and we can persist that change to the database immediately.