Was there a deal that China broke?
No. I didn't say there is a deal. But Iran was expecting CHina to continue to buy oil openly even with the US sanction.
But CHina didn't do it really because of fear of sanction. CHina oil import reduce a lot officialy even if CHina is still buying Iran oil trough Malaysia.
Anyway, since 2016, there has been quite a hectic new development between China and USA. Did you notice? Trade war leading to the Phase One deal, war on Huawei, US interference on Hong Kong and now Tiktok. Can you see the new calculus for China? Can you see that the past does not apply as much to China now?
All those thing are theatrical. The past will apply until CHina have a good IR policy and strategy.
US have a strategic approach to the PRC write in the NDS document with clear objective.
Where is the China similar doctrine against US? That is what China need firstly.