Tone instructions in a system prompt collapse the moment your AI hits production. "Write in our brand voice" is the prompt-engineering equivalent of writing a comment that says "make it work." It does nothing the model wasn't already going to do, and it breaks the moment a user asks something the example outputs didn't cover.
I built five production AI products on the same technical spine, three of them with strong, distinct brand voices that had to hold under unusual conditions. Couples in the most emotionally loaded purchase of their lives. Families of missing people. Multi-tenant hospitality clients with completely different tones from each other. The four-layer architecture in this talk is what survived contact with all of them.
The four layers, in order: the immutable identity layer (what the brand structurally cannot say), the situational mode layer (what shifts when the user's state shifts), the example-anchored voice layer (where most teams stop, and why it isn't enough on its own), and the post-generation veto layer (the cheap final pass that catches what the other three missed).
Real prompts. The multi-tenant pattern that made it scale. The failure cases that forced each layer into existence. The version I'd build differently if I started today.
Could do a hands-on workshop on prompt building.