Two of the main feature's we're investing heavily into are remote sandboxes + syncing, and voice agent support, wouldn't work with E2EE.

I can voice chat with Happy coder. Also, I run happy coder in a sandbox of mine on my computer. What do you mean by syncing? Happy coder syncs sessions between all my happy coder clients. I can even see in real time how happy coder in my browser's conversations progress as well as on my phone, in parallel.