Eating before midday:<a href="#_ftn1" name="_ftnref1">[1]</a>
One may not fast past midday on Chol Hamoed. One must thus eat or drink something prior to midday.
<a href="#_ftnref1" name="_ftn1">[1]</a> M”A 652:4; Admur 288:1 rules that it is forbidden to fast until midday on Shabbos, even if one does not intend to do so as a fast. The same applies towards Yom Tov and Chol Hamoed. [M”A 652:4; M”B 652:7 regarding Chol Hamoed Sukkos] However regarding Rosh Hashanah however see Ateres Zekeinim 597; M”B 597:2; Kaf Hachaim 597:6

Shulchan Aruch HaRav | Eating before midday on Chol Hamoed

Eating before midday:[1] One may not fast past midday on Chol Hamoed. One must thus eat or drink something prior to midday. [1] M”A 652:4; Admur 288:1 rules that it is forbidden to fast until midday on Shabbos, even if one does not intend to do so as a fast.