Spec-Driven Development
Spec-driven development is an approach in which explicit product and workflow definitions guide implementation, documentation, review, and verification.
Definition
In this approach, a specification is not only an initial planning artifact. It acts as an ongoing reference for:
- product purpose
- scope boundaries
- required behavior
- acceptance criteria
- review standards
Why it matters in AI-assisted work
AI increases delivery speed, but it can also increase product drift when intent is vague.
Spec-driven development helps by giving teams a stable source of truth that can be reviewed, updated, and used to evaluate generated output.
Typical layers
Common layers in a spec-driven system include:
- product specification
- implementation guidance
- current-state documentation
- demo or application behavior
- validation rules and tests
- CI/CD enforcement
Common failure mode
A common failure mode is letting the most visible artifact become the default source of truth.
Examples:
- the latest prompt
- the current prototype
- the current implementation shortcut
- a stale documentation page
Spec-driven development reduces that risk by making the intended authority chain explicit.
Let Books context
In Let Books, spec-driven development is supported by:
AGENTS.mdAGENTS-Implementation.mdREADME.mddocs/Development.mddocs/Deployment.md