What are the rulings concerning someone who joins a congregational prayer late (masbuq) when the Imam prostrates for forgetfulness (sujud al-sahw)?

A latecomer to congregational prayer (masbuq) whose Imam makes a mistake in prayer (saha) has two scenarios:

1. The Imam prostrates for forgetfulness (sujud al-sahw):

If the Imam prostrates before the salutation (taslim), the worshipper must follow him. As for whether he should repeat the prostration after finishing his prayer, there are two opinions.

If the Imam prostrates after the salutation, following him is obligatory according to the Hanbalis and the Hanafis (Ahl al-Ra'y), whereas Al-Shafi'i and Malik said that the latecomer should complete what he missed and then prostrate.

2. The Imam does not prostrate for forgetfulness:

The latecomer prostrates at the end of his prayer, according to the Hanbalis.