That is certainly interesting.

We’ve all seen the video where the Erlang guys live update the code on a telephone switch without closing any of the calls that are on-going.

Elixir runs on the Erlang VM.

Does Drab support hot code reloading? Does it handle modifications of templates without breaking existing client sessions?

Drab is a hex package, so asking if it supports hot code reloading isn't the right question. As to the second question, the answer is yes assuming your server side hot code didn't break the client session, and didn't introduce an API mismatch.

Not an expert on this matter but I'm pretty sure it doesn't mess with that particular base feature of the programming language / runtime.

That’s a good question. I haven’t played with it enough to know, just been watching from a distance til it hits 1.0.