# Spec Driven Development — Chapter 02 Memory: 0 - Why SDD is essential in the age of AI
- **Stage**: Complete
- **Next Step**: None (frozen). Next chapter is Chapter 03.
- **Reading Span**: PDF pages 13–19
- **Source Text**: /library/Spec Driven Development/Chapter-02-Why-SDD-is-essential-in-the-age-of-AI/Chapter-02-source-text.md (the chapter's own words; read instead of the PDF)
- **Full Record**: /library/Spec Driven Development/Chapter-02-Why-SDD-is-essential-in-the-age-of-AI/Chapter-02-chapter-notes.md (read only if needed)
- **Last Updated**: 2026-10-01

## Carried-in Context (from earlier chapters)
- Ch1: Ködel offers his experience (VB6 ERP, Basel II systems, mobile apps, long-run ownership of *Meu Cronograma Capilar*) as the reason to examine his approach. Reader trusts him and wants to see the method; credibility is not evidence of general effectiveness.

## This Chapter
- **Core Question**: Why does a specification matter more when AI generates code quickly?
- **Core Thesis**: As AI makes code generation fast, Ködel argues that a clear specification becomes more valuable because people must decide what to build, judge the result, and remain accountable for it.
- **Key Concepts**: Vibe-coding; specification as a reference; judge, decide, answer; the illustrative 70/30 framing.
- **Notable Arguments / Evidence Limits**: Hypothetical permission, offline, scale, and product-specific edge cases. No measured comparison establishes the 70/30 split or SDD's general effectiveness.
- **Action Item**: Write a five-line mini-spec for one small feature: problem, intended user outcome, one rule, one edge case, and a check that would show it works.

## Reader State
- **Pending Questions**: None
- **Reader's Answers (paraphrase)**: Identified vague agent prompting, the human duties to judge/decide/answer, edge cases, and the purpose of the 70/30 framing.
- **Misconceptions / Feedback Given**: A specification supplies the evaluation target; the percentages are illustrative, not measured.
- **Personal Threads**: None

## Open Threads
- 70/30 split and SDD effectiveness remain unsupported by measurement; watch for evidence later.