# Day 5: Spec-Driven Development

> You'll learn why writing specs before code matters and how the Specify → Plan → Execute loop works. SDD is the methodology that ties AI-Native Engineering together and keeps outputs aligned with intent.

- **Source:** https://ainativesoftware.engineering/roadmap/day-5
- **Site:** AI-Native Software Engineering — https://ainativesoftware.engineering/book

- **Day:** 5 of 7
- **Topics:** 4
- **Reading time:** 7 minutes

You'll learn why writing specs before code matters and how the Specify → Plan → Execute loop works. SDD is the methodology that ties AI-Native Engineering together and keeps outputs aligned with intent.

## The 4 topics

- 01 · [Why Spec-Driven Development?](https://ainativesoftware.engineering/roadmap/day-5/why-spec-driven-development.md) — The root problem SDD solves: drift, hallucination, and the limits of vibe coding. Why specs are durable artifacts that survive tool changes. _(1 min)_
- 02 · [SDD as a Pillar of AI-Native Engineering](https://ainativesoftware.engineering/roadmap/day-5/sdd-as-a-pillar-of-ai-native-engineering.md) — How Spec-Driven Development fits into the broader AI-Native Engineering discipline and why it's the methodology that ties everything together. _(2 min)_
- 03 · [Spec-kit: The Open Toolkit](https://ainativesoftware.engineering/roadmap/day-5/spec-kit-the-open-toolkit.md) — A hands-on look at GitHub's Spec Kit  how it structures the Specify → Plan → Tasks workflow and integrates with PR review gates. _(1 min)_
- 04 · [Spec-kit Under the Hood](https://ainativesoftware.engineering/roadmap/day-5/spec-kit-under-the-hood.md) — A 20-30 minute deep dive into Spec-kit's source code. Once you know how it works in practice, reading its templates and commands shows you exactly what prompts drive the workflow and gives you a model for building your own. _(3 min)_

**Every curated resource in day 5**

- [Understanding SDD - Martin Fowler](https://martinfowler.com/articles/exploring-gen-ai/sdd-3-tools.html)
- [SDD as a pillar of AI-Native Engineering](https://jsdevai.com/pillars/spec-driven-development)
- [Spec Kit - Official Toolkit](https://speckit.org/)
- [Getting Started with Spec-Kit - Microsoft Developer Blog](https://developer.microsoft.com/blog/spec-driven-development-spec-kit)
- [Spec-kit Commands – GitHub Source](https://github.com/github/spec-kit/tree/main/templates/commands)
- [Spec-kit Templates – GitHub Source](https://github.com/github/spec-kit/tree/main/templates)

- **Previous day:** [Day 4: Context Engineering and MCP](https://ainativesoftware.engineering/roadmap/day-4.md)
- **Next day:** [Day 6: Spec-Driven Development](https://ainativesoftware.engineering/roadmap/day-6.md)
- **All days:** [The 7-day roadmap](https://ainativesoftware.engineering/roadmap.md)

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_AI-Native Software Engineering by Alfonso Graziano (O'Reilly Media, Early Release; print edition February 2027). Every page of ainativesoftware.engineering is also served as Markdown: append `.md` to any URL. Index: https://ainativesoftware.engineering/llms.txt — whole site in one file: https://ainativesoftware.engineering/llms-full.txt._