Spec-Driven Development with AI: Building a Real Flutter Feature Step by Step

Spec-driven development is a workflow that shifts decision-making before implementation begins when using AI coding agents. Instead of sending a vague prompt directly to an agent, you first generate a detailed spec by having the agent ask clarifying questions and research the existing codebase. The workflow demonstrated uses the Agentic Coding Toolkit with five steps: spec, refine-spec, plan, work, and compound. A real Flutter feature (stacked area chart for a portfolio tracker) is used to show how hidden product decisions around UX, persistence, and edge cases are surfaced and resolved before any code is written. Even with a solid spec, manual QA remains essential for catching visual issues at runtime.