I have always been expecting that sooner or later, India would outright backstab Russia and get real cozy with the West thanks to US pursuasion and Delhi's view that Moscow and Beijing are getting closer ever than before (and that Russia would become China's vassal thanks to the war in Ukraine).
Therefore, China should do its best to bring Russia completely over to its side and have Russia provide assistance to China in terms of intelligence on the Indian military, considering that at present, there are still significant amount of arms caches in India that are sourced from Russia. However, the later might not be very useful, but it would have to do.
Besides, as I have previously mentioned in the PLA Strategy for Taiwan Conflict thread - China must always be prepared for a two-front war - One in the WestPac frontier over Taiwan and the SCS against the US and their "allies", and another one in the Himalayan frontier over Aksai Chin and Aruchal Pradesh against US-backed India.
Of course, the higher priority should be given to the WestPac frontier compared to the Himalayan frontier, since the WestPac is where the key for the ultimate survival of the Chinese civilization state lies (remember that the barbaric invasion of China by Imperial Japan started there). However, whenever possible, the WTC should be able to at least hold off the Indian invasion of Tibet on their own while waiting for the WestPac frontier to be dealt with. The goal is to make the Himalayan frontier into as much of a WW1-style static front as possible. This could last for years, but it should be managable for the PLA thanks to the terrain.
At the same time, the MSS and PAP should monitor Tibet closely for any signs of insurrection movements supported by India, aiming to destabilize Tibet and negatively affect PLA movements in the region. On the flipside, China should massively increase the support of separatist movements in northeastern India for the similar goals of making things difficult for the Indian military in the Sikkim and South Tibet region.
Meanwhile, India-Myanmar relations should also be watched closely by Beijing. If Naypyidaw shows any sign of openly supporting India's actions against China, China should reciprocate in kind WRT the separatist movements in northern Myanmar. In contrary to many's opinion here, I don't think China should rely on any meaningful help from Myanmar.
Plus, China should consider roping Pakistan in to help China and split India's attention. For this, I believe Pakistan doesn't need to invade India - Just massing troops along the Indo-Pakistan border and the Jammu & Kashmir (J&K) region would be helpful to keep some portions of the Indian military attached to the Indo-Pakistani border and the J&K region. However, I wouldn't count on Karachi heavily for their capability in helping China to hold India off, considering that their military leadership has been throughoutly infiltrated by pro-US elements.