---
title: What Is SDD
collection: Spec Driven Development for AI Apps
author: Anirudh Jwala
updated: 2026-10-21
source: https://docs.chaicode.com/sdd/what
---

# What Is SDD

## Spec-Driven **Development**

Spec-Driven **Development**
Define what correct means before writing code.
Define the intended behavior before implementation
Use that specification to guide development and verification
Depending on the workflow, the spec may guide a single change or evolve alongside the software

## Four Questions Every Spec **Answers**

A good spec answers
Four Questions Every Spec **Answers**
What are we building?
How should it behave?
What must never happen?
How will we verify it?

## A Conversation Carries Context. A Spec **Preserves Decisions**.

Prompt vs Spec
A Conversation Carries Context. A Spec **Preserves Decisions**.
A conversation carries context. A spec preserves decisions.
Decisions scattered across messages → Requirements in one place
Context tied to conversations → Reusable across sessions
Changes through follow-up prompts → Changes recorded explicitly
Requirements may be implicit → Requirements are reviewable

## SDD does not replace prompting

Key idea
SDD does not replace prompting
It makes important decisions **explicit**, **reviewable** and **reusable**.

## Four artifacts, four **questions**.

Artifacts and their jobs
Four artifacts, four **questions**.
Proposal: Why are we changing this?
Spec: What behavior must the system provide?
Design: How will we implement it?
Tasks: What needs to be done?

## Your decisions belong in the **repo**

Your decisions belong in the **repo**
Keep important decisions alongside your code. Review them, version them, and verify the result.