Is it obligatory for the congregant to perform the prostration of forgetfulness (sujud al-sahw) if he makes a mistake in reciting Al-Fatiha and repeats it, and is the prayer invalidated by the intention to repeat it after finishing?

If a worshipper (ma'mum) incurs an obligation for the prostration of forgetfulness (sujud al-sahw) while praying behind an imam, the imam bears that responsibility on his behalf.

If one makes a mistake in reciting Al-Fatiha that does not alter the meaning, their recitation and prayer are valid, and they are not required to repeat what they erred in. However, if the mistake changes the meaning, they must repeat the recitation. If they do so intentionally, their prayer becomes invalid; otherwise, it does not. The prostration of forgetfulness is not required in this case.

If a worshipper abandons the intention of prayer to repeat it, their prayer becomes invalid, and they must repeat it. But if the intention for prayer remains present, their prayer is valid.