We've known for awhile that Nathan has trouble with transitions. He needs a two minute warning before switching tasks or activities. He also has a lot of trouble with demands (even basic replying to a "hello") while he's in the middle of a transitional activity, such as coming home from school or tidying up before getting screen time.
However, we've also discovered that we have to be careful when we ask him about things he'd like to do. Stuff he would normally be excited about (seeing his grandparents, going on a playdate) will be met with rigid resistance if asked in the wrong time. A simple question like "Are you hungry for lunch?" can induce a toy-throwing explosive tantrum if it interrupts his mental process.
I've been trying to compensate for this by using the 2 minute technique for interruptions. I tell him that I have a question for him and will ask in two minutes, then he can play some more. In two minutes, I have him pause his game (I've noticed the tantrums are especially bad if I interrupt screen time), wait until he's calmed down (usually 10-15 seconds) and then I ask the question. If he starts to whine or evade, I remind him that he needs to answer me before he can play more.
This technique works for questions like what he wants for lunch or checking to make sure a task has been done. But it won't work for asking if he wants to do an activity. Because whatever he's doing in the moment will win out over any future option, no matter how enticing. For these, I've had to find moments where he's not particularly engaged in something, draw him out, give him time to collect his thoughts and then ask about it. And I have to be prepared, just because he's agreed to do something, it doesn't mean he'll do it without a tantrum when the time comes.
We're limited screentime as much as possible to try and avoid tantrums but we can't get rid of it entirely. It gets exhausting to say yes to screentime when I know that getting him off the computer or iPad or Xbox will be a fight. I'm trying to use an impartial timer more and more but he tends to be so caught up in what he's doing that he misses the sound of it going off.
I'll find a way. Meanwhile, I work on reminding him that tantrums are not an acceptable way to express feelings and open negotiations.
If only more people had figured that out in life.