Vibe Coding vs Spec Coding

March 9, 2026

These two terms get thrown around a lot. Usually by people who’ve picked a side and want to argue about it. I use both, depending on what I’m building and where I am in the process.

Here’s a straight comparison.

Definitions

Vibe coding: You prompt an AI with a rough idea and iterate based on what it produces. No spec, no detailed plan. You describe what you want in natural language, look at the output, adjust, repeat. The AI leads the structure. You steer.

Spec coding: You write a specification first — data models, file structure, behavior, constraints — then hand it to the AI for execution. The spec leads the structure. The AI implements.

Neither is inherently better. They solve different problems at different stages.

When vibe coding works

Vibe coding is genuinely good for:

Prototyping. You have an idea and want to see if it holds up. You don’t need clean architecture — you need a thing on screen. Vibe code it. Get the shape. See if the concept works before investing in structure.

Exploring APIs and libraries. When I’m trying a new library, I’ll vibe code a quick integration to see how it behaves. The code is throwaway. The knowledge isn’t.

Learning. If you’re picking up a new language or framework, vibe coding lets you move fast and see patterns. You learn by watching what the AI generates, then questioning its choices.

One-off scripts. Need a script to migrate data between formats? Parse a log file? Generate seed data? Vibe code it. It runs once. It doesn’t need architecture.

Solo projects that stay small. A personal tool, a single-page app, a browser extension. If the entire codebase fits in one or two files, vibe coding gets you there faster than spec coding ever will.

I wrote more about these scenarios in when vibe coding is actually fine. The short version: vibe coding is great for things that don’t need to scale.

When vibe coding breaks down

The problems show up when:

The codebase grows past a few files. Without a spec, the AI makes structural decisions on the fly. Those decisions compound. By file 10, you have inconsistent patterns, duplicated logic, and an architecture that nobody planned.

You need to work in parallel. You can’t vibe code with 6 AI sessions at once. Each session would make its own structural choices, and they’d conflict. Parallel work requires shared specs.

Someone else needs to understand the code. Vibe-coded projects have no documentation of intent. The code exists, but the “why” behind the structure lives only in the chat history that generated it.

You need to iterate over weeks. The first session is fine. The fifth session is guessing at the conventions the first session established. By session ten, you’re fighting the AI to maintain consistency.

I went deeper on this in why vibe coding breaks at scale. The pattern is predictable: vibe coding works until complexity crosses a threshold, then it collapses.

When spec coding works

Spec coding is built for:

Production applications. Scouter has 50+ files, a database schema, API routes, a frontend, and a scraper system. Every major feature started with a spec. Without specs, there’s no way Claude would maintain consistent patterns across that many files.

Parallel development. When I run 8 Claude Code sessions at once, every session has a spec. The specs define file paths, expected behavior, and constraints. Each session works independently because the spec removes ambiguity.

Multi-week builds. Specs are persistent context. When you come back to a project after a week, the spec tells Claude (and you) exactly what the plan was. No need to reconstruct intent from code.

Anything with a team. Even a team of one person plus AI agents. The spec is the contract between you and the agent. It’s how you verify the output matches the intent.

The complete guide to spec coding covers the methodology in full.

The real cost of each

Vibe coding costs: rework time. You move fast initially, but you pay later in refactoring, debugging structural issues, and rewriting things that should have been planned. The total time for a complex project is often higher than spec coding because of the rework cycle.

Spec coding costs: upfront time. You spend 10-30 minutes writing a spec before any code gets generated. For simple tasks, that overhead isn’t worth it. For complex tasks, it pays for itself many times over.

The break-even point, in my experience: anything that touches more than 3 files or takes more than one session to complete.

Below that threshold, vibe code. Above it, write a spec.

The hybrid approach

In practice, I rarely use pure vibe coding or pure spec coding. Most work falls somewhere in between.

Phase 1: Vibe the prototype. I have an idea for a new feature in Scouter. I vibe code a rough version to see if the UX works. Quick, scrappy, no spec. This takes 15 minutes.

Phase 2: Spec the real version. The prototype confirms the idea is worth building. I throw away the prototype code and write a spec. Data model, API endpoints, frontend components, file structure.

Phase 3: Execute the spec. Claude Code builds the real version from the spec. The output is clean, consistent, and reviewable.

This is how Lucid’s audio session feature got built. Vibe-coded prototype in an afternoon to test the interaction model. Spec’d and rebuilt properly the next day. The prototype was throwaway. The spec was the real investment.

Decision framework

Use this:

What actually matters

The vibe coding vs spec coding debate misses the point. The real question is: do you have a plan for what you’re building, or are you making it up as you go?

Sometimes making it up as you go is the right call. Exploration needs freedom. But production needs structure. The developers who ship consistently are the ones who know when to switch modes.

Vibe code to explore. Spec code to ship. Know which phase you’re in.