spec-kit/docs/concepts/sdd.md

# What is Spec-Driven Development?

Spec-Driven Development **flips the script** on traditional software development. For decades, code has been king — specifications were just scaffolding we built and discarded once the "real work" of coding began. Spec-Driven Development changes this: **specifications become executable**, directly generating working implementations rather than just guiding them.

## Core Philosophy

Spec-Driven Development is a structured process that emphasizes:

- **Intent-driven development** where specifications define the "*what*" before the "*how*"
- **Rich specification creation** using guardrails and organizational principles
- **Multi-step refinement** rather than one-shot code generation from prompts
- **Heavy reliance** on advanced AI model capabilities for specification interpretation

Spec Kit does not prescribe how teams preserve or mutate `spec.md`, `plan.md`,
and `tasks.md` after requirements change. See
[Spec Persistence Models](spec-persistence.md) for the concepts and
[Evolving Specs in Existing Projects](../guides/evolving-specs.md) for the
existing-project evolution workflows.

## Development Phases

| Phase | Focus | Key Activities |
|-------|-------|----------------|
| **0-to-1 Development** ("Greenfield") | Generate from scratch | <ul><li>Start with high-level requirements</li><li>Generate specifications</li><li>Plan implementation steps</li><li>Build production-ready applications</li></ul> |
| **Creative Exploration** | Parallel implementations | <ul><li>Explore diverse solutions</li><li>Support multiple technology stacks & architectures</li><li>Experiment with UX patterns</li></ul> |
| **Iterative Enhancement** ("Brownfield") | Brownfield modernization | <ul><li>Add features iteratively</li><li>Modernize legacy systems</li><li>Adapt processes</li></ul> |

## Experimental Goals

Our research and experimentation focus on:

### Technology Independence

- Create applications using diverse technology stacks
- Validate the hypothesis that Spec-Driven Development is a process not tied to specific technologies, programming languages, or frameworks

### Enterprise Constraints

- Demonstrate mission-critical application development
- Incorporate organizational constraints (cloud providers, tech stacks, engineering practices)
- Support enterprise design systems and compliance requirements

### User-Centric Development

- Build applications for different user cohorts and preferences
- Support various development approaches (from vibe-coding to AI-native development)

### Creative & Iterative Processes

- Validate the concept of parallel implementation exploration
- Provide robust iterative feature development workflows
- Extend processes to handle upgrades and modernization tasks