It’s that Shabbos with the vexing problem again: What to say in bentching of Seudah Shlishis on Shabbos Erev Rosh Chodesh?
1) Don’t eat “pas” (challah, bread, cake) after sheki’ah–and only say retzei.
2) If you did eat “pas”, but not past 20 minutes after sheki’ah, only say retzei.
3) If you did eat “pas” past 20 minutes, you have a problem. Aruch haShulchan says only retzei, MB says only ya’aleh veyavoh or maybe both. So don’t do this. Control yourself!
To accommodate everyone, we will be shortening Minchah by not saying “Tzidkosscho tzedek,” thus enabling everyone to start their seudah shlishis that much earlier.