Yes, staying overnight in Mina during the Days of Tashreeq is considered wajib (farz) by the majority of scholars. Specifically, hacilar should spend the nights of the 11th and 12th of Dhul Hijjah in Mina, with the 13th night being optional (as early departure on the 12th is permitted). The requirement is to be present in Mina for the majority of the night — roughly from Maghrib (sunset) to Fajr (dawn).
The tent cities of Mina are organized by country and Hac group, with assigned camps. Life in the Mina tents is communal and simple — hacilar sleep in air-conditioned tents, share meals, and use their time between stoning rituals for worship, Kur'an recitation, and rest. The days in Mina are spiritually significant as they are the Days of Tashreeq, during which Hz. Peygamber (sallallahu aleyhi ve sellem) said: 'The Days of Tashreeq are days of eating, drinking, and remembrance of Allah.'
If a haci does not stay overnight in Mina without a valid excuse, a fidyah (sacrifice of a sheep) is required alimlerin cogunluguna gore. Valid excuses include: genuine inability to find space in Mina (which does occur due to overcrowding), medical emergencies, or being assigned accommodation outside Mina boundaries by the authorities. Those whose camps are technically outside Mina's boundaries should still spend as much time as possible within the boundaries.