Design is the shape that makes behavior verifiable.

Studio 3 is about how you can tell a design is good before you look at the code — and why that judgment matters more now, not less, when AI can produce plausible code in seconds.

What you will experience

You will work with a set of pricing and discount policies. They begin simple and clear. Then they stop being either.

You will stay out of code for most of this Studio. That is deliberate. Implementation, when it arrives too early, captures all the attention — and the thing worth looking at here is the shape underneath it.

What to watch for in yourself

• The moment a rule stops being easy to verify on its own.
• What it costs to set up a check — and what that cost is telling you about the design.
• Which rule actually owns a behavior, when two of them overlap.
• Whether your AI stays at the level of behavior, or reaches for code before you have decided what you are building.

What you will produce

A Testability Review Card for one real feature from your own work — something you can run before asking AI for an implementation. It lives in your Explorer Workbook.

Why this one matters

Recognizing quality is one of the most valuable things a developer carries, and it is quietly getting easier to skip. Explorers who give this Studio their full attention tend to leave with something durable: a way of seeing that does not depend on the tools of the moment.

Be ready before the session

• Your AI of choice, signed in and ready.
• Your IDE of choice, open and working.
• Your language of choice.
• A new, empty project.
• Your Explorer Workbook, open.

You will write less code in this Studio than in the others — but come set up anyway. AI is part of the work from the start.