A spec is an envelope that contains all programs that comply. Creating this spec is often going to be harder than writing a single compliant program.

Since every invocation of an LLM may create a different program, just like people, we will see that the spec will leave much room for good and bad implementations, and highlight the imprecision in the spec.

Once we start using a particular implementation it often becomes the spec for subsequent versions, because it's interfaces expose surface texture that other programs and people will begin to rely on.

I'm not sure how well LLMs will fare are brownfield software development. There is no longer a clean specification. Regenerating the code from scratch isn't acceptable. You need TPS reports.