If one desires to fulfill shalosh seudos by eating cake, fruit, or fish, is it necessary to stop eating them by shkia, or may one continue to eat them for as long as one desires? Sources would be much appreciated.
For fruit or fish one must stop, for mezonos one may be lenient to continue eating.
See Pesachim 105a that one must stop drinking but not stop eating. It is questionable what is included in eating. The Rishonim pose various explanations for the obligation to stop drinking: it is not considered important [chashuv] to have a continuation [Rashi], there is no “keva” set meal – for drinking [Tosfos], havdala is drinking, so all other drinking must be stopped [Meiri]. Based on all these reasons one eating mezonos may continue. This was the opinion of Harav Elyashiv [Hilchos Shabbos Bshabbos Vol 4, pg. 203. cf. Aruch Hashulchan O:C 299:5.