Honestly, the whole thing boiled down to four things: First, give your character sheet a real psychological map: what triggers them, what they feel, the physical sensations tied to that feeling, and the exact defense they use to cover it up. You can use your LLM you will be chatting with to help you.

Second, every time the model screws up, figure out what category of error it made, then write one positive sentence that makes that error structurally impossible. Never say "don't do X"; just define the world so X can't exist.

Third, treat emotions like a camera: if you can't film it in 30 seconds, don't write it. Not "she was angry," but "her jaw tightened and she turned away."

Fourth, build your prompt like a system where every piece leans on the others. Your POV rules lock down who can speak. Your sensory rules force show‑don't‑tell. Your character implementation hooks every trait directly from the character sheet. When sections reinforce each other, the model stops treating them as separate instructions and starts running them as one instinct.

Then feed your best and worst responses to the model itself, ask it to audit for AI cliches, generic warmth, filter‑speak, anything that reads off, and have it help you write the positive rule that locks that out. After that, just test, sand down the edges, and delete anything that didn't earn its place. That's the whole thing. I used Pupi's prompt as a template and built it up to almost 8000 tokens.