There is a distinction in software development that the industry has spent twenty years pretending doesn't exist. It is the distinction between building software and understanding what you are building. The first is implementation. The second is engineering. They are not the same thing, they do not require the same skills, and conflating them is the single most expensive mistake a development organisation can make. The mistake is now being turbocharged by AI. But to understand why, you first need to understand what was already broken. Part One: The 85% Nobody Talks About Two Kinds of Work Ask most developers how long it takes to build a feature and they will give you an implementation estimate. How long to write the code, wire up the endpoints, get the tests green. That estimate — the part where fingers meet keyboard — accounts for roughly 10 to 15 percent of what building good software actually requires. The other 85 to 90 percent is structuring. Understanding what the system is.…