This is working really well in GPT-5! I’ve never seen a prompt change the behavior of Chat quite so much. It’s really excellent at applying logical framework to personal and relationship questions and is so refreshing vs. the constant butt kissing most LLMs do.

I add to my prompts something along the lines of "you are a highly skilled professional working alongside me on a fast paced important project, we are iterating quickly and don't have time for chit chat. Prefer short one line communication where possible, spare the details, no lists, no summaries, get straight to the point."

Or some variation of that. It makes it really curt, responses are short and information dense without the fluff. Sometimes it will even just be the command I needed and no explanation.

Is there a way to make this a default behavior? a persona or template for each chat