Interesting idea. My problem is that one “stream” usually spans multiple apps that silo data. So i have an email from a client and command line and a tab in chrome and maybe a note and an excel file. There are of course exceptions to this, but in real life we bring tools to the project not the other way around. Naturally some “projects” might have sub projects, or some might be transient - a quick email reply. You might organize your digital life this way - with virtual desktops, but why can’t the computer keep track?