How do restartless add-ons work?

I blogged a short time ago about how we’re adding support for a new form of add-on to Firefox that can install and uninstall without needing to restart the application. Since then I’ve been finalizing a specification for how the platform will load these add-ons, trying to keep it simple but still give developers everything they commonly need. The planned specification is now available and if developers have comments then I’d like to hear them. Currently there isn’t a version of Firefox that implements it but that should change in the next day or so when I make the changes to the add-ons manager project branch and very soon when it all lands on trunk.

My hope is that once on trunk this spec won’t change but obviously this is quite new so we may see changes for a short time if add-on developers come across problems.