Spec-driven development (SDD) for AI coding assistants. Lightweight, iterative, and built for real projects.
Our Philosophy:
Agree before you build. Stay organized. Work fluidly. Use your tools.
Human and AI align on specs before code gets written. No more vague prompts or unpredictable results.
Each change gets its own folder with proposal, specs, design, and tasks. Everything in one place.
Update any artifact anytime, no rigid phase gates. Iterate freely and adapt as you go.
Works with 20+ AI assistants via slash commands. No lock-in, no vendor restrictions.
Understand changes at a high level without digging through code. Review proposals in seconds.
Specifications live alongside code in your repository. Context persists beyond chat sessions.
Simple workflow, powerful results
You: /opsx:new add-dark-mode
AI creates the change folder structure and prepares the proposal.
You: /opsx:ff # "fast-forward"
AI generates proposal.md, specs/, design.md, and tasks.md automatically.
You: /opsx:apply
AI implements all tasks systematically, following the specs and design.
You: /opsx:archive
Move completed changes to archive and update specs. Ready for the next feature.
Get started in minutes. Requires Node.js 20.19.0 or higher.
npm install -g @fission-ai/openspec@latestAlso works with pnpm, yarn, bun, and nix
cd your-project
openspec init# Tell your AI:
/opsx:new <what-you-want-to-build>OpenSpec works with 20+ AI coding assistants:
Engineers who want predictable AI output without heavyweight process—whether you ship alone or in a team.
Keep intent in Markdown next to your code so new chat sessions pick up where you left off. See best practices for context hygiene.
Review proposal and spec deltas before large diffs land. Useful for onboarding and async review. Patterns in use cases.
Add SDD incrementally: openspec init does not require rewriting your app. Learn what SDD means in practice.
Same workflow across supported assistants. Dedicated notes for Cursor and MCP.
Real-world usage example
/opsx:new add-dark-mode
/opsx:ff # "fast-forward" - generate all planning docs
/opsx:apply
/opsx:archive
Long-form explanations, terminology, and team patterns—built for search and for humans skimming before they install.
Definitions, how SDD differs from ad-hoc prompting, and when specs pay off for AI-assisted coding.
Read the guide →How to write proposals, keep tasks small, review deltas, and work safely in brownfield codebases.
See practices →From solo side projects to regulated teams: where OpenSpec fits and how to roll it out.
Explore use cases →Quick reference for change folders, fast-forward, archive, AGENTS.md, and other OpenSpec terms.
Open glossary →Setup tips, slash commands, and how to keep specs and code in sync in the Cursor editor.
Cursor guide →What is new in the CLI and docs, with a link to the full history on GitHub.
View highlights →OpenSpec vs alternatives
Spec Kit: Thorough but heavyweight. Rigid phase gates, lots of Markdown, Python setup.
OpenSpec: Lighter and lets you iterate freely. No Python required. 5-minute setup vs 30 minutes.
BMAD: Powerful multi-agent system but complex setup and steep learning curve.
OpenSpec: Simple, focused on spec management. Get started in minutes, not days.
Kiro: Powerful but locked into their IDE and limited to Claude models.
OpenSpec: Works with the tools you already use. No vendor lock-in.
Without specs: Vague prompts and unpredictable results. Context lost in chat history.
OpenSpec: Brings predictability without the ceremony. Persistent context.
Open-source spec-driven development for teams and solo builders using AI assistants