Spec-First Coding

1. Concept Overview & Systemic Problem

The main temptation for newcomers in vibe coding is speed. It seems that the magic of AI lies in throwing out a single sentence: “Build me a subscription system with Stripe, a user dashboard, and a database” — and watching a pile of code appear in 30 seconds.

However, in 95% of cases, such euphoria ends in disaster: the project throws up 50 compilation errors, database migrations conflict, and attempts to ask “Fix this!” only worsen the situation, erasing already written working code.

The Spec-First methodology is the gold standard of mature AI development. It is based on the ironclad rule:

No line of code until the architectural plan in the SPEC.md file has been read and approved by a human!

2. Architectural Taxonomy & Mental Model

┌─────────────────────────────────────────────────────────────┐
│                 TWO APPROACHES TO VIBE CODING              │
├─────────────────────────────────────────────────────────────┤
│ ❌ Chaotic Approach (Vibe & Pray):                          │
│    “Write the entire feature at once”                       │
│    ➔ AI generates 500 lines of mess                         │
│    ➔ Nothing works ➔ 3 hours of debugging and stress        │
├─────────────────────────────────────────────────────────────┤
│ ✅ Spec-First Approach (Disciplined Engineering):           │
│    1. Create `SPEC.md` (Architecture and Steps)            │
│    2. Human reviews the plan: “Fix the logic here”         │
│    3. Only after OK: Agent implements Step 1 ➔ Verification │
│    4. Agent implements Step 2 ➔ Verification                │
│    ➔ Clean, working project from the start!                 │
└─────────────────────────────────────────────────────────────┘

3. Technical Pipeline & Internal Mechanics

1. Step 1: Planning Prompt:

   “Do not write code! We are planning to add a comment system under articles. Create a SPEC.md file that describes: the database table schema, necessary API routes, a list of new components, and 4 step-by-step implementation tasks.”

2. Step 2: Human Review: You open the created SPEC.md, read it, and make edits: “Let’s remove the option for anonymous comments, only after login.”
3. Step 3: Step-by-Step Execution:

   “Plan approved. Now execute ONLY Task 1 from the specification (create the table schema and migration). Do not touch the rest.”

4. Step 4: Verification: You check that the migration was successful, and only then do you give the command to proceed to Task 2.

4. Production Engineering Scenarios

01. Implementing a Comment System

You initiate the project by creating a SPEC.md that outlines the database schema and API routes, ensuring clarity before any code is generated.

02. Developing a User Dashboard

The SPEC.md includes detailed descriptions of components and their interactions, allowing for a structured approach to building the dashboard without confusion.

03. Integrating Payment Processing

By defining the payment flow and necessary APIs in the SPEC.md, you streamline the integration process, reducing errors and enhancing efficiency.

5. Pitfalls, Common Mistakes & Security

The Spec-First approach transforms you from a confused user begging the bot to fix a broken site into a Chief Technical Officer (CTO). You manage strategy and architecture, while AI obediently acts as a fast yet disciplined executor.