There’s a pattern that appears over and over again when devs get frustrated with Claude Code (or with any code agent, really): they give it a vague idea, the agent interprets something different from what they had in mind, generates code that works but doesn’t solve the real problem, and the cycle of corrections becomes an endless loop.
The problem is almost never in the model. It’s in the input.
spec-based-claude-code is a concrete implementation of a solution to that problem: a Spec-Driven Development workflow built directly into Claude Code using custom slash commands.
What is Spec-Driven Development?
The central idea is simple: before you write a single line of code, you write a specification. Not a vague comment in the chat. A real spec — with problem context, expected behavior, edge cases, acceptance criteria, and explicit design decisions.
Only when the spec is clear does the agent start implementing.
The approach isn’t new. It has roots in BDD (Behavior-Driven Development) and contract-by-design methodologies. What changed is that we now have code agents capable enough that a good spec translates directly into functional implementation, without having to write each line manually.
How spec-based-claude-code works
The repository implements the workflow through slash commands that guide both the developer and the agent through a structured process:
/spec — Define before implementing
The first command forces the creation of a complete specification before touching code. The agent doesn’t ask “what do you want me to do?” — it walks you through a structured process to define:
- The real problem you’re solving (not the solution you have in mind)
- The expected behavior in terms of observable inputs and outputs
- The edge cases that matter for your specific context
- The technical constraints — what it can use, what it has to respect, what’s out of scope
The result is a spec document that lives in your repository. Not in the chat. In the repo.
/plan — Architecture before code
With the spec as a foundation, the next command generates a technical implementation plan. Which files will be created or modified, what dependencies come in, what architectural decisions are made and why.
This step is especially valuable because it forces Claude Code to reason about the complete solution before committing to a particular implementation. Architectural errors are exponentially cheaper to fix in a text plan than in code already written.
/implement — Disciplined execution
Only at this point does the agent start generating code — but not from scratch, but following the approved plan and defined spec. The context is loaded, the decisions are made, and the margin for divergent interpretations is minimized.
Why it works
The underlying problem with conversational prompting for coding is that ambiguity accumulates. Each vague instruction adds uncertainty, and the agent fills that uncertainty with its own assumptions — which are sometimes reasonable, and sometimes not.
A well-written spec eliminates that ambiguity before the problem exists.
It also changes the dynamics of review. Instead of reviewing code line by line and trying to understand if it does what you wanted, you review the spec first. If the spec is good, the code almost always is too. If the code is wrong, you go back to the spec and find the disconnect.
Who should use this
Spec-based-claude-code has more value in contexts where:
- Features are complex — more than a couple of files, more than one use case, cross-dependencies
- The cost of redoing is high — features that impact critical parts of the system, public APIs, or core business logic
- You work in a team — specs are living documentation that others can review and question before a single line of code exists
- You use long-running agents — workflows like Ralph Loop benefit enormously from having specs that the agent can reread between tasks
For small scripts and simple CRUD tasks, the overhead probably isn’t worth it. But for anything that requires more than 30 minutes of implementation, the time you invest in the spec will save you in corrections.
How to get started
The repository has 103 stars and is growing actively. Installation is straightforward — the slash commands are added to your Claude Code configuration and are available in any project from that point on.
The most valuable thing is not just executing the commands, but internalizing the mindset shift they propose: first fully understand the problem, then solve it.
With increasingly capable code agents, the differentiating skill won’t be knowing how to program — it will be knowing how to specify. Devs who learn to write clear specs will multiply what they can build alone.
spec-based-claude-code is available on GitHub. Claude Code, custom slash commands, and the plugin ecosystem surrounding them are topics we cover regularly on yoDEV.