[jgruen]

Agreed. Right now we're pretty hands off about modifying default behaviors, link handling etc. Chalk this up to us wanting to be unopinionated about specific use cases, but there are definitely some optimizations to be made to shore up the situations you describe. Test Pilot is for WIP software, so don't be shy about filing issues.

[Ar-Curunir]

Would it be possible to have an add-on for this? One that automatically opens each website in a new container? That would allow default behaviour for most people, but for those that want isolation, it would be easy to get it.

[cpeterso]

There is a Contextual Identities API for WebExtensions shipping in Firefox 53:

https://developer.mozilla.org/en-US/Add-ons/WebExtensions/AP...