Fission-AI/OpenSpec

→ fluid not rigid
→ iterative not waterfall
→ easy not complex
→ built for brownfield not just greenfield
→ scalable from personal projects to enterprises

Follow @0xTab on X for updates · Join the OpenSpec Discord for help and questions.

You: /opsx:explore
AI:  What would you like to explore?
You: I want dark mode but I'm not sure how to do it cleanly.
AI:  Let me look at your styling setup...
     Cleanest path here: CSS variables + a small theme context,
     with system-preference detection. No new dependencies. Scope it?
You: Yes, let's do it.

You: /opsx:propose add-dark-mode
AI:  Created openspec/changes/add-dark-mode/
     ✓ proposal.md — why we're doing this, what's changing
     ✓ specs/       — requirements and scenarios
     ✓ design.md    — technical approach
     ✓ tasks.md     — implementation checklist
     Ready for implementation!

You: /opsx:apply
AI:  Implementing tasks...
     ✓ 1.1 Add theme context provider
     ✓ 1.2 Create toggle component
     ✓ 2.1 Add CSS variables
     ✓ 2.2 Wire up localStorage
     All tasks complete!

You: /opsx:archive
AI:  Archived to openspec/changes/archive/2025-01-23-add-dark-mode/
     Specs updated. Ready for the next feature.

## ADDED Requirements

### Requirement: Theme selection
The app SHALL let users switch between light and dark themes,
defaulting to the system preference.

#### Scenario: User toggles dark mode
- **WHEN** the user clicks the theme toggle
- **THEN** the app switches to dark mode and persists the choice

Solo, OpenSpec keeps you and your AI honest on a single repo. On a team, the hard part moves: a feature spans the API server, the web app, and a shared library; requirements are owned by one team and consumed by others; planning starts before any code exists.

Stores are the answer — planning in a repo of its own. The same openspec/ shape you already know (specs and changes), shared by git push like anything else. One source of truth your whole team and every coding agent can read, across every repo.

• Cross-repo features — one change, one plan, even when the code lands in three repos.
• Shared requirements — a platform team owns the specs; product teams reference them read-only, right where their coding agent can read them. No drifting wiki.
• Plan before code — capture the plan in the store now; the code repos catch up later.

Stores are in beta. Start with the Stores User Guide.

Requires Node.js 20.19.0 or higher. Homebrew installs it as a dependency.

Install OpenSpec globally:

npm install -g @fission-ai/openspec@latest

Or install the official Homebrew formula on macOS or Linux:

brew install openspec

Then navigate to your project directory and initialize:

cd your-project
openspec init

Want your AI to do it? Paste the setup prompt into your coding assistant — it installs the CLI, runs openspec init, and verifies the result.

Now talk to your AI:

• Not sure what to build yet? Start with /opsx:explore, a no-stakes thinking partner that reads your code, weighs options, and shapes a plan before any code gets written. (Explore guide)
• Already know what you want? Go straight to /opsx:propose <what-you-want-to-build>.

Both are in the default profile. If you want the expanded workflow (/opsx:new, /opsx:continue, /opsx:ff, /opsx:verify, /opsx:bulk-archive, /opsx:onboard), select it with openspec config profile and apply with openspec update.

/opsx:propose is the canonical name; your tool may spell it /opsx-propose (Cursor, GitHub Copilot), @opsx-propose (Amazon Q) or $openspec-propose (Codex). openspec init prints the right form for the tools you picked — see How To Invoke.

Start here: the Documentation Home maps everything. New to OpenSpec? Read Getting Started, then How Commands Work (where you actually type /opsx:propose).

→ Getting Started: first steps
→ Explore First: think it through with /opsx:explore before you commit
→ How Commands Work: where slash commands run vs the CLI
→ Core Concepts at a Glance: the whole mental model, one page
→ Examples & Recipes: real changes, start to finish
→ Workflows: combos and patterns
→ Existing Projects: adopt OpenSpec on a brownfield codebase
→ Editing a Change: update artifacts, go back, reconcile manual edits
→ Commands: slash commands & skills
→ CLI: terminal reference
→ Stores: plan in a separate repo, shared across your team (beta)
→ Supported Tools: tool integrations & install paths
→ Concepts: how it all fits
→ Multi-Language: multi-language support
→ Customization: make it yours
→ Community Showcase: projects and resources built with and for OpenSpec
→ FAQ · Troubleshooting · Glossary: quick help

Third-party schema bundles distributed via standalone repositories — these provide opinionated workflows that integrate OpenSpec with other tools, similar to how github/spec-kit's community extension catalog handles tool integrations.

→ Browse the catalog in the customization docs.

AI coding assistants are powerful but unpredictable when requirements live only in chat history. OpenSpec adds a lightweight spec layer so you agree on what to build before any code is written.

• Agree before you build — human and AI align on specs before code gets written
• Stay organized — each change gets its own folder with proposal, specs, design, and tasks
• Work fluidly — update any artifact anytime, no rigid phase gates
• Use your tools — works with 30+ AI assistants via slash commands

vs. Spec Kit (GitHub) — Thorough but heavyweight. Rigid phase gates, lots of Markdown, Python setup. OpenSpec is lighter and lets you iterate freely.

vs. Kiro (AWS) — Powerful but you're locked into their IDE and limited to Claude models. OpenSpec works with the tools you already use.

vs. nothing — AI coding without specs means vague prompts and unpredictable results. OpenSpec brings predictability without the ceremony.

Upgrade the package

npm install -g @fission-ai/openspec@latest

If you installed OpenSpec with Homebrew:

brew upgrade openspec

Refresh agent instructions

Run this inside each project to regenerate AI guidance and ensure the latest slash commands are active:

openspec update

Model selection: OpenSpec works best with high-reasoning models. We recommend Codex 5.5 and Opus 4.7 for both planning and implementation.

Context hygiene: OpenSpec benefits from a clean context window. Clear your context before starting implementation and maintain good context hygiene throughout your session.

Open a discussion (for core design changes) or an issue before you open a PR, and link the issue or discussion from the PR. New features, significant refactors, and architectural changes need an OpenSpec change proposal first.

→ CONTRIBUTING.md: the full process, from first issue to merged PR

MIT