Quote Originally Posted by Segev View Post
There isn't "fighter's extra attacks" and "bladesinger's extra attacks." There's the number of attacks you're allowed. That's why they don't stack.
There is the ability Extra Attack granted by the Fighter class, and an ability Extra Attack granted by the Bladesinger class. Per the rules on multiclass, the features don’t get added together.

You are saying “yes, you can add them together” and I’m wondering what you’re basing this on as the RAW is very clear they don’t add together.

So how do you take the BS ability, which clearly states you can use one of the attacks granted by that specific ability and cast a cantrip, and add that property to the Fighter ability; without adding those features together?