SPX: Spec-Driven Development for AI Agents

What is SPX?

SPX is a framework for Spec-Driven Development — a methodology that combines fast, deterministic CLI tooling with Claude Code plugins to streamline AI-assisted development workflows.

The Problem

When working with AI coding assistants, checking the status of work items typically requires expensive LLM calls that take 1-2 minutes and consume tokens. This creates friction in the development loop.

The Solution

SPX provides:

spx CLI: Instant status checks in under 100ms with zero token cost
SPX-Claude Marketplace: Pre-built Claude Code plugins for testing, coding, and documentation workflows

Fast CLI Tooling

The spx command-line tool scans your specs/ directory and provides instant, deterministic status analysis of capabilities, features, and stories.

spx CLI

Read on

1spx status
2spx next
3spx session handoff

Claude Code Plugins

The SPX-Claude marketplace provides skills and commands for TypeScript, Python, testing, specifications, and productivity workflows.

SPX-Claude Marketplace

Read on

1claude plugin marketplace add simonheimlicher/spx-claude
2claude plugin install core@spx-claude

Get Started

Install the CLI and marketplace to begin using Spec-Driven Development:

1# Install spx CLI
2git clone https://github.com/simonheimlicher/spx-cli.git
3cd spx-cli && npm install && npm run build && npm link
4
5# Add Claude Code marketplace
6claude plugin marketplace add simonheimlicher/spx-claude
7claude plugin install core@spx-claude