Openspec
Spec-driven development (SDD) for AI coding assistants.
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What is Openspec?
OpenSpec is a lightweight, open-source spec-driven framework that adds a living specification layer to software repositories so AI coding agents and human developers can plan, implement, and verify features against explicit requirements. It stores human-readable specs and change proposals alongside code (openspec/specs/ and openspec/changes/) so intent, constraints, and verification criteria persist with the codebase rather than being lost after a chat session. The tool generates change proposals, implementation tasks, technical design notes, and spec deltas for each proposed feature so teams can review and refine plans before any code is written, reducing misalignment and catching design mistakes early. OpenSpec is designed for brownfield codebases and teams that want to preserve system context; it supports many coding assistants and works locally without API keys or central managed services, making it usable by individual developers and teams seeking reproducible, reviewable planning workflows.
Openspec pricing
Pricing model: Freemium
OpenSpec is offered as an open-source, free-to-use framework that runs locally with no API keys or managed control plane required; the website describes core functionality as free and open source, with invitations for teams to join early access or private collaboration for upcoming team-oriented features (workspaces and advanced integrations) rather than explicit paid tiers listed on the site.
Openspec pros
- Stores specs as living documentation alongside code
- Generates proposal, design, tasks, and spec deltas for each change
- Reduces context loss between AI sessions by persisting intent
- Brownfield-first design tailored to mature codebases
- Works locally with no API keys or managed control plane required
- Universal agent compatibility across 20+ coding assistants
- Lightweight CLI with minimal setup and quick onboarding
- Spec deltas make reviews focused on requirements, not code
- Encourages review and verification before implementation
- Integrates with Git workflows and PR-based collaboration
- Helps detect and prevent agent hallucination by supplying specs
- Living spec library improves new-developer ramp-up
- Proposal -> change lifecycle creates an auditable history
- Searchable specs give agents reliable, up-to-date context
- Modular folder layout (openspec/specs and openspec/changes) is simple and transparent
Openspec cons
- Requires discipline to write and maintain specs (manual effort)
- Not a magic planner—needs human engagement to be effective
- Spec generation for entire existing codebases is not solved
- Team workspace and advanced collaboration features are still in development
- May add overhead to fast prototyping workflows
- Depends on teams adopting Git workflows to get full value
- Primarily text/markdown based—no visual modeling provided
- Feature set for large multi-repo enterprises is incomplete
Frequently asked questions about Openspec
How does OpenSpec integrate with my repository?
OpenSpec stores specs and change proposals in your repository under an openspec/ folder (openspec/specs/ for capability specs and openspec/changes/ for change proposals and deltas), letting you check living requirements into version control and collaborate through normal Git workflows.
Which AI coding assistants work with OpenSpec?
OpenSpec is designed to be agent-agnostic and currently lists native support for many popular coding assistants (for example: Claude Code, Cursor, Codex, GitHub Copilot and others), with compatibility across 20+ coding agents so your specs remain useful regardless of agent choice.
Do I need API keys or a managed service to use OpenSpec?
No—OpenSpec runs locally and is built to work without API keys or a central managed control plane, so you can use it in local development and check specs into your repo without depending on vendor-managed services.
What does a typical change proposal include?
Each change proposal includes a proposal.md describing intent, a design.md covering technical decisions, a tasks.md breaking implementation into phases and tasks, and spec delta files under openspec/changes/<change>/specs/ that show exactly how requirements will change.
Can OpenSpec verify work after implementation?
Yes—OpenSpec emphasizes verification by capturing 'how to verify' criteria in specs and spec deltas so completed work can be checked against explicit acceptance scenarios rather than relying solely on code inspection.
Is OpenSpec suitable for greenfield projects?
OpenSpec can be used in greenfield projects, but the project is intentionally brownfield-first—it focuses on helping mature codebases where documenting existing intent and decisions matters most.
How do specs help prevent agent hallucinations or wrong implementations?
Specs provide persistent, authoritative context that agents read when planning and executing work; by specifying requirements, scenarios, constraints, and verification steps, agents are less likely to guess or fill gaps incorrectly because they have structured guidance tied to the repository.
Are specs machine-readable or only human-readable?
OpenSpec uses human-readable markdown for specs and a defined folder/schema layout so both humans and tools (including agents and validators) can read, search, and act on the specification content; there is also an open schema for the format to support tool interoperability.
How do I start using OpenSpec in an existing project?
Install the CLI and initialize OpenSpec in your project (for example via the npm package), then create the openspec/ folder and add specs for capabilities you want to preserve; use commands to create changes, view diffs, list specs, and iterate through proposals before implementing code changes.
What team features are planned or coming soon?
The project roadmap mentions upcoming team-focused features such as Workspaces for longer-lived planning across sessions, multi-repo planning, deeper integrations, and customization for large codebases, with opportunities for teams to join early access and help shape roadmap priorities.