About SPXSpec-Driven Development Framework

SPX is an open-source framework for Spec-Driven Development — a methodology designed to bring structure, speed, and determinism to AI-assisted development workflows.

The framework consists of two main components:

A fast, deterministic command-line tool that:

  • Scans specs/ directories for work item status
  • Provides instant (<100ms) status checks without LLM calls
  • Manages work sessions for context handoffs between agents

Repository: github.com/simonheimlicher/spx-cli

A Claude Code plugin marketplace providing:

  • Pre-built skills for TypeScript and Python development
  • Commands for git workflows and context management
  • Testing and specification writing guidance

Repository: github.com/simonheimlicher/spx-claude

When working with AI coding assistants, several challenges emerge:

  1. Status checks are slow: Asking an LLM to check work status takes 1-2 minutes and consumes tokens
  2. Context is lost: Work sessions don’t naturally persist between conversations
  3. Workflow is ad-hoc: Without structure, AI-assisted development can become chaotic

SPX addresses these challenges by:

  • Making status determination instant and deterministic via filesystem conventions
  • Providing session management for context continuity
  • Establishing clear hierarchies (capabilities → features → stories)

SPX is open source under the MIT license. Contributions are welcome:

  1. Report issues on GitHub
  2. Submit pull requests
  3. Share feedback and ideas

SPX is created and maintained by Simon Heimlicher.

MIT License — see the repositories for full license text.