OpenSpec

Agree on a spec with your coding agent before it writes code

About

Lightweight spec layer that keeps you and your coding agent aligned

OpenSpec adds a small planning loop to any repo. Run `openspec init`, then use slash commands like /opsx:explore to think through an idea, /opsx:propose to create a change folder (proposal.md, specs, design.md, tasks.md), /opsx:apply to implement the checklist and /opsx:archive to fold the finished change back into the living specs. Specs are plain Markdown requirements with WHEN/THEN scenarios, so there is no special syntax to learn, and it is built for brownfield codebases, not just new projects. Stores (beta) put planning in its own repo so one plan can span several code repos. Built by Fission AI, it passed 72k GitHub stars and the repo itself is planned with OpenSpec. Repo: https://github.com/Fission-AI/OpenSpec.

Features

Proposal, specs, design and tasks per change, in plain Markdown
Slash commands: explore, propose, apply, archive
Works with 30+ coding tools (Claude Code, Codex, Cursor, Copilot, Amazon Q and more)
Built for existing codebases, not just greenfield
Stores (beta) for cross-repo planning
Install with npm or Homebrew

Install