Is the Imam's final Tashahhud a pillar (rukn) or an obligation (wajib) for the latecomer (ma'mum masbuq), knowing that it is not the last for the latecomer?

Scholars differ on whether the final Tashahhud and the prayer upon the Prophet are pillars (arkān) or not. As for the latecomer (masbūq), the final Tashahhud is desirable (mustaḥabb) for him, unless it is in the position of his first Tashahhud, such as if he caught two rak'ahs with the Imam. In that case, the Tashahhud is obligatory for him. It is desirable for the latecomer to complete the final Tashahhud, including the prayer upon the Prophet (peace be upon him), provided he caught two rak'ahs with the Imam, based on the preference of some scholars.