> Is [immersion] being only in the programming environment and not leaving? The dream is never leaving, as expressed by the Dynabook concept. However, in the full expression of that dream, the browser et al that you mention would also be inside the context.

In practice, things like using a browser for documentation is acceptable but not super common because viewing in the IDE is so much more powerful in certain ways (e.g. executable examples, finding "senders" of a message).

The idea is about having one's computer be "turtles all the way down" where you have the same power to change and explore every layer of the system without learning a whole new technology - from what we usually leave to the OS (which Dan Ingalls said "shouldn't exist") to what currently exists in apps (which Alan Kay and the creators of Smalltalk envisioned as services, which didn't stovepipe possibilities/power down to a small fraction of what's available).