Modern AI doesn’t fail only when a model is wrong; it fails when the system around the model lacks clear policies, enforceable guardrails, and explanations people can trust. “Governance by design” means building those elements into the lifecycle—data to deployment—so reliability isn’t an afterthought. This article offers a practical blueprint you can implement without derailing delivery: what to govern, how to encode it, where to enforce it, and how to prove it works.