Design Concept★

The design concept (a term coined by Fred Brooks in The Design of Design) is the shared understanding of a feature's purpose, rules, and boundaries. It is not the code, the specifications, or the prompt; it is the mental alignment held between the developer and the agent.

You develop a design concept whenever you:

• Discuss the goals of a feature with an agent before writing code.
• Interview the agent or answer its questions about how edge cases should behave.
• Iterate on mockups to align your visual preferences.

The Gaps of Silence

A common developer frustration is: "The agent wrote exactly what I prompted, but it's still completely wrong."

• The Cause: The design concept was incomplete in your own head. Because you hadn't worked out all the edge cases (like how to handle partial refunds or shipping cancellations), your prompt was silent on them.
• The Reaction: The agent did not stop to ask. Instead, it silently filled the gaps with its own assumptions, generating plausible-sounding code that conflicts with your actual intent.

A design concept is successfully shared when the agent begins suggesting answers or predicting edge cases exactly the way you would. Until that alignment is reached, writing a Spec or code is premature.

Aligning the Concept

To build a solid design concept:

1. Grill the Plan: Have the agent interview you Socratically to uncover hidden assumptions.
2. Prototype Early: Have the agent build a quick, throwaway visual page so you can react to it.