OpenSpec
FreeSpec-driven development (SDD) for AI coding assistants.
FreeFree tier
Inputs: text
About OpenSpec
OpenSpec is a lightweight, open-source framework for spec-driven development (SDD) with AI coding assistants. It enables developers to define structured specifications alongside their code, allowing AI agents to understand requirements and track changes through spec deltas. When a change is proposed, OpenSpec automatically generates a proposal document, implementation tasks, technical design decisions, and spec deltas—so intent is reviewed before any code is written. Specs live in the repository, providing persistent context that survives chat sessions or team turnover. The tool natively integrates with over 20 popular AI coding tools, including Claude Code, Cursor, GitHub Copilot, Windsurf, and more, with custom slash commands or AGENTS.md support. OpenSpec is available under the MIT license and requires no API keys or MCP setup.
Key Features
Spec deltas: captures the change in requirements, making it easy for developers to understand how they are modifying the system and for reviewers to grasp changes without digging through code.
Persistent context: specifications live in the repository alongside code, organized by capability, so context does not disappear when a chat session ends or someone leaves the team.
Proposal generation: from a natural language description of a desired change, OpenSpec automatically creates a change proposal (proposal.md), implementation tasks (tasks.md), technical design decisions (design.md), and spec deltas for review.
Native integration with over 20 AI coding tools, including Claude Code, Cursor, Codex, GitHub Copilot, OpenCode, Windsurf, Gemini CLI, Antigravity, Cline, RooCode, Kilo Code, Amazon Q, Qoder, Auggie CLI, Qwen Code, CodeBuddy, CoStrict, Crush, Factory, Droid, iFlow, and more.
AGENTS.md support for tools that do not have native slash commands; agents pick up instructions automatically.
Lightweight and open source: MIT license, no API keys or MCP required, installable via npm.
Workspaces feature in development: aimed at large codebases, multi-repo planning, customization, and team collaboration.
Pros & Cons
Pros
- Open source and free, with no API keys or MCP required.
- Lightweight framework that integrates natively with many popular AI coding tools.
- Spec deltas provide a clear, high-level view of requirement changes, aiding code review.
- Persistent context in the repository ensures specs survive chat sessions and team turnover.
- Automatic generation of proposals, tasks, and design decisions speeds up the change planning process.
- Designed to catch misalignment early by reviewing intent before any code is written.
Cons
- Workspaces feature for team collaboration on large codebases and multi-repo planning is still under development.
- Requires adoption of a spec-driven workflow, which may have a learning curve for teams accustomed to other approaches.
- Relies on specific tool integrations; while many are supported, not all AI coding assistants are covered.
Best For
Reviewing intent of code changes before implementation by examining generated proposals and spec deltas.Onboarding new developers: they can browse the spec library to understand system capabilities and requirements.Managing requirements changes across large codebases with structured spec deltas that show exactly what is changing.Collaborating with AI coding assistants on feature development with a plan-then-code workflow.Maintaining persistent context for AI agents across chat sessions and team changes.Planning multi-repo changes (upcoming Workspaces feature).
FAQ
What is OpenSpec?
OpenSpec is a lightweight, open-source framework for spec-driven development (SDD) with AI coding assistants. It helps define, track, and review requirements through spec deltas and automatic proposal generation.
Is OpenSpec free?
Yes, OpenSpec is open source with an MIT license and is free to use. There are no paid tiers or API keys required.
Which AI coding tools does OpenSpec support?
OpenSpec has native integration with custom slash commands for tools like Claude Code, Cursor, Codex, GitHub Copilot, Windsurf, Gemini CLI, Cline, RooCode, Amazon Q, and many more. Tools without native integration can use AGENTS.md support.
How do I get started with OpenSpec?
Install via npm: 'npm install -g @fission-ai/openspec@latest' and follow the documentation on the GitHub repository.
How does OpenSpec handle context persistence?
Specifications live in the repository alongside code, organized by capability. AI agents read these specs for context, and changes produce spec deltas that persist across sessions and team changes.