Understanding Spec-Driven-Development: Kiro, spec-kit, and Tessl

After looking over the usages of the term, and some of the tools that claim to be implementing SDD, it seems to me that in reality, there are multiple implementation levels to it:

• Spec-first: A well thought-out spec is written first, and then used in the AI-assisted development workflow for the task at hand.
• Spec-anchored: The spec is kept even after the task is complete, to continue using it for evolution and maintenance of the respective feature.
• Spec-as-source: The spec is the main source file over time, and only the spec is edited by the human, the human never touches the code.

All SDD approaches and definitions I’ve found are spec-first, but not all strive to be spec-anchored or spec-as-source. And often it’s left vague or totally open what the spec maintenance strategy over time is meant to be.

Source: Understanding Spec-Driven-Development: Kiro, spec-kit, and Tessl