Forking conversations have been a thing for a long time, and it's not the same thing (e.g. you may have 50% of your context used up at fork time that is carried into "both agents" afterwards)
Also sometimes _not_ having the context is what you want.
Eg when I have the AI do a self-code-review before bothering a human, I also want to the AI to give the draft PR to a sub-agent that only has the publicly available context that a viewer of the final PR would have; and not all the accumulated reasoning that lead to the writing of the code in the PR.
