What minimum food intake is required for a third person to join two bread-eaters for a zimun of three?

BlessingsBirkat HaMazon

Synopsis

For a zimun of three, the Mechaber cites three opinions on what minimum the third person must eat: (1) a kazayit of bread specifically; (2) a kazayit of any grain product; (3) any food or drink at all. The Mechaber rules l'chatchilah to require bread, but b'dieved accepts any food.

Rishonim
Early Acharonim
Late Acharonim
Lenient
Strict
Lesser cited
Major authority

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