What is the ruling if a worshipper intentionally swallows a sesame seed placed into their mouth from outside during prayer?

Invalidations of Prayer Part 2: Excessive Actions and Excretions

• Valid, because it is smaller than a chickpea.
• Invalid, because eating any external food during prayer invalidates it.
• Valid only if done in Nafal prayer.
• The worshipper must perform Sujud al-Sahw.