You can look at the Web as a starter: https://html.spec.whatwg.org/#history-2

> The WHATWG was based on several core principles, (..) and that specifications need to be detailed enough that implementations can achieve complete interoperability without reverse-engineering each other.

But in my experience you need more than a spec, because an implementation is not just something that implements a spec, it is also the result of making many architectural choices in how the spec is implemented.

Also even with detailed specs AI still needs additional guidance. For example couple of weeks ago Cursor unleashed thousands of agents with access to web standards and the shared WPT test suite: the result was total nonsense.

So the future might rather be like a Russian doll of specs: start with a high-level system description, and then support it with finer-grained specs of parts of the system. This could go down all the way to the code itself: existing architectural patterns provide a spec for how to code a feature that is just a variation of such a pattern. Then whenever your system needs to do something new, you have to provide the code patterns for it. The AI is then relegated to its strength: applying existing patterns.

TLA+ has a concept of refinement, which is kind of what I described above as Russian dolls but only applied to TLA+ specs.

Here is a quote that describes the idea:

There is no fundamental distinction between specifications and implementations. We simply have specifications, some of which implement other specifications. A Java program can be viewed as a specification of a JVM (Java Virtual Machine) program, which can be viewed as a specification of an assembly language program, which can be viewed as a specification of an execution of the computer's machine instructions, which can be viewed as a specification of an execution of its register-transfer level design, and so on.

Source: https://cseweb.ucsd.edu/classes/sp05/cse128/ (chapter 1, last page)