I think I am starting to get my answer. I would love to have the option of responding exactly like you describe, but to do that, I need to be a lot more sorted about how these things upend me, and not be so upended. Plus there's something right now about respect for myself and my sensitivities, as stupid and irritating as they feel.

Mindfulness model would suggest something like:

Acceptance: This is where I am at, no matter how much I wish I was more sorted/less fragile/not damaged/less sensitive.

Non-judgement: and I am not gonna beat myself up for those things (in this situation). And I can explore this without judging T before he has actually done anything, also, and the situation.

Compassion: this is hard and exposing and scary and uncertain for someone who's been through what I have. I need much self-kindness and caring and should double up on self care (actually doing some would be progress)

Be here now:this is not XT, not my parents, I am not 8 years old. I have been through so many things since then and learned so much, and I have new skills and strengths that can keep me safe and moored to reality and here, now.

Have run out of top-of-mind Mindful-isms but I am going to try to start here:

Something I am learning in T is that I can address things that scare me without getting myself caught up in motive, judging the other or letting my fears/past experience be the adjudicator for what is happening in my life now.

So reality right now is: T is (lolling back in the chair) relaxed and appears to be engaged and interested (lost???) in our dialogue. He's sprawled out a bit, with his legs closer to me than they used to be. I remain in my usual position, bunched up, as small as possible, legs crossed as a barrier, jammed into the arm of the couch.

How curious that his physical loosening up brings up so many difficult thoughts, feelings and fears for me. What might that be about (and one of the options is that sometimes something genuinely scary is going on)? Can I sit with that, keep it in my consciousness (not dissociate, push it away to 'make' things 'safe' so I can keep him as all-good) and so keep myself truly safe, and can I tentatively trust him to walk through this, with me?