Spec-Driven Development

Overview

Write a structured specification before writing any code. The spec is the shared source of truth between you and the human engineer, it defines what we're building, why, and how we'll know it's done. Code without a spec is guessing.

When to Use

• Starting a new project or feature
• Requirements are ambiguous or incomplete
• The change touches multiple files or modules
• You're about to make an architectural decision
• The task would take more than 30 minutes to implement

When NOT to use: Single-line fixes, typo corrections, or changes where requirements are unambiguous and self-contained.

The Gated Workflow

Spec-driven development has four phases, preceded by a scope check (Phase 0) that activates only when one request bundles several independently testable capabilities. Do not advance to the next phase until the current one is validated.

SPECIFY ──→ PLAN ──→ TASKS ──→ IMPLEMENT
   │          │        │          │
   ▼          ▼        ▼          ▼
 Human      Human    Human      Human
 reviews    reviews  reviews    reviews

Phase 0: Scope Check

Most requests describe one capability. If this one does, skip this phase and go straight to Specify, Phase 0 exists for the exception, not the rule, and it puts no hierarchy on single-capability features.

Detection. Decompose before specifying when a single requirement bundles several independently testable capabilities:

• The requirement names distinct capabilities with their own consumers or data (e.g. identity, billing, notifications, reporting)
• Acceptance criteria cluster into groups that could ship and be verified separately
• One capability could be cut or replaced without rewriting the others' requirements

Propose a capability map before writing any spec. Small and reviewable, a module table plus a build order, not a project plan:

# Capability Map: [Initiative Name]