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Spec Driven Development for AI Apps

What Is SDD

Anirudh Jwala 6 pages 1 min read Updated Oct 21, 2026
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  1. Spec-Driven **Development**
  2. Four Questions Every Spec **Answers**
  3. A Conversation Carries Context. A Spec **Preserves Decisions**.
  4. SDD does not replace prompting
  5. Four artifacts, four **questions**.
  6. Your decisions belong in the **repo**

Spec-Driven Development

Define what correct means before writing code.

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A good spec answers

Four Questions Every Spec Answers

  1. 1What are we building?
  2. 2How should it behave?
  3. 3What must never happen?
  4. 4How will we verify it?
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Prompt vs Spec

A Conversation Carries Context. A Spec Preserves Decisions.

Prompt-drivenSpec-driven
Decisions scattered across messagesRequirements in one place
Context tied to conversationsReusable across sessions
Changes through follow-up promptsChanges recorded explicitly
Requirements may be implicitRequirements are reviewable

A conversation carries context. A spec preserves decisions.

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Key idea

It makes important decisions explicit, reviewable and reusable.

SDD does not replace prompting

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Artifacts and their jobs

Four artifacts, four questions.

  1. 01ProposalWhy are we changing this?
  2. 02SpecWhat behavior must the system provide?
  3. 03DesignHow will we implement it?
  4. 04TasksWhat needs to be done?
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Your decisions belong in the repo

Keep important decisions alongside your code. Review them, version them, and verify the result.

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