OpenSpec is a lightweight agreement layer between you and your AI coding assistant — “plan mode, but organized.” It’s lighter than alternatives like git-spec or BMAD, fluid by design (no phase gates), and built brownfield-first for existing codebases.

→ Open presentation

In Short

  Heavier approaches OpenSpec
Setup Methodology + templates npm install + openspec init
Specs Full system spec first Delta specs — only what’s changing
Workflow Separate tools, phase gates Slash commands in your AI chat
Existing code Document everything upfront One change at a time, specs grow

The loop: propose → apply → archive. Describe what you want, AI drafts the plan, you review, AI builds, you archive. All in your existing chat — no new UI to learn.

Philosophy

fluid not rigid         — no phase gates
iterative not waterfall — refine as you go
easy not complex        — minimal ceremony
brownfield-first        — existing code, not just greenfield

Artifacts are enablers, not gates — edit any of them anytime. Discover the design was wrong mid-implementation? Fix design.md and keep going.