Are you using AI to stress-test your idea before writing a single line of code?

I've noticed a pattern in almost every "how I built this" thread here lately: before touching the keyboard, people are opening a chat window with an LLM and asking it to poke holes in their idea.

Makes sense. Vibe coding has made building fast. You can go from idea to working prototype in an afternoon. But building fast doesn't mean you're building the right thing faster. If anything, it raises the cost of a wrong guess, because now you can ship the wrong product in a day instead of a month.

So I've started using AI earlier in the process to argue with me. I'll describe an idea and ask it to play the most skeptical potential customer it can, or to list every reason the idea might already be a solved problem. Sometimes that surfaces a competitor I hadn't seen. Sometimes it forces me to actually define the problem instead of jumping straight to the feature list.

Here's the part that worries me though: AI models are notoriously agreeable. If I phrase my idea with enthusiasm, I sometimes get validation back that feels a little too easy like it's mirroring my confidence rather than actually stress-testing the logic. That's dangerous, because it can create false certainty right before you commit real time to building something nobody asked for.

So I'm curious how others here are handling this:

• Do you use AI in your validation step, and how exactly do you prompt it to be genuinely critical rather than agreeable?

• Has AI ever given you false confidence that led you to build the wrong thing?

• What's your actual process for separating "AI thinks this is a good idea" from "real humans think this is a good idea"?

Not looking for tool recommendations here, just more interested in the actual habits and prompts people use, and where you've drawn the line between AI-assisted thinking and just talking yourself into something.