All uses of force are to be considered as escalations, aside from self-defence and UN SC. Even forceful response to previous use of force is escalation.

It is a new level of violence between the countries as Iran has directly attacked Israel from its territory for the first time in history. A direct follow-up action by Israel on Iranian territory could almost trigger a whole new spiral wave of violence.

There have been attacks on embassies in the past. For example

1983 Beirut

1992 Buenos Aires

1998 Nairobi and Dar es Salaam

An interesting article from Foreign Affairs, by K.N. Waltz, published in 2012, and titled 'Why Iran Should Get the Bomb'

See link: https://www.jstor.org/stable/23218033