Prose, a brief, even a screen recording — shipd compiles whatever you give it into the same three reviewable artifacts: a plan, testable requirement deltas, and a task list, checked into your repo. Answers you've given before are already there; they're never asked twice.
A deterministic gate checks the spec against your actual codebase before a line of code is written. Gaps park the plan with findings attached — you enrich it, it re-enters. The system stops rather than guess.
An independent validator tries to refute every scenario in the spec against the running code, then CI and a semantic review — explicitly dispositioned, on record — gate the merge. What ships is what the spec says, verified.