Here the people who do this for a living part ways. One camp says the spec is now the real source code.
Spec-driven development
Also called SDD, Specifier role
Working so that the spec comes first and stays the main thing: you write and review the spec, and agents produce the code from it. How far this goes varies, from a spec for one task to a spec that replaces code as what you edit.
It answers a real problem. Code is cheap, intent gets lost, and agents write more than anyone can read, so a spec gives you something smaller to check. The bill is long documents to review, and an agent that may still ignore them.
Say it to your agent
“Write the spec for this feature in specs/webhooks.feature, as Given/When/Then scenarios with real values. Stop there. I will approve it, and then a separate session writes the code and makes each scenario run as a test.”