What's missing from the web to support transparent browser restarts?

Could browsers restart without negatively impacting user experience? Why would we need this? Because of security of course. If you've been paying attention, you've seen that all major browsers now release new updates much more frequently than they used to. Down to two weeks in fact. This is mainly due to wanting to quickly patch security vulnerabilities because attacks have been getting more numerous, faster, and more sophisticated. And AI is only making this worse. So releasing new updates quicker and restarting the browser more often is a good thing. One blocker, though, is that end-users have learned, through many years of bad experiences, that closing a tab, let alone restarting the browser, is a very bad thing. You risk losing your work, your state, your session, and so on. And they're mostly right, many sites don't survive a restart. Browsers might need to start forcing restarts to get users to update. But a forced restart isn't the only case where we need to consider…