The prompts themselves are encrypted when saved to disk, so you can't inspect them after the fact. If you switch agent threads in the terminal UI (you can kinda swap active session to prompt subagents yourself), you can see the subagent prompt set by the main agent, as long as you have the terminal client open. And this is also for v2 multi_agent mode, v1 doesn't have this, but you need to do a bunch of annoying stuff to re-enable v1 for GPT-5.6 Sol and Terra.