What is the ruling on fasting Thursday after having intended to fast on the night preceding Eid, and then learning in the morning that it is the day of Eid al-Fitr?

Whoever intended to fast on the day of Eid while unaware of it incurs no sin, but they must break their fast immediately upon learning that it is an Eid day, because fasting on the day of Eid is forbidden by scholarly consensus. This applies to both obligatory and voluntary fasting. However, if Eid is established astronomically but not legally (by sighting), then one is not commanded to break their fast.