OpenSpec

OpenSpec is an open-source, CLI-driven spec-driven development (SDD) framework from Fission AI. Instead of asking an AI to just build a feature, it forces the creation of structured, source-of-truth specifications (proposals, specs, design notes, tasks) stored in an openspec folder inside the repo, which agents reference to produce more accurate, maintainable code. The core loop is change-driven: current specs live in openspec/specs, proposed work in openspec/changes, and deltas merge back after review.

The GitHub repository has surged past 68,000 stars (press-reported) and the npm package @fission-ai/openspec is past version 1.13. It is framework-agnostic, working with Claude Code, Cursor, GitHub Copilot, Cline, Aider, Windsurf, and Codex. The philosophy is that AI assistants are confident even when wrong, so requirements should live in the repository rather than in a chat thread.

The honest picture: OpenSpec adds process overhead, which pays off on teams and brownfield codebases and can feel heavy for solo throwaway scripts. It excels at managing updates to existing features (delta specs need no upfront docs). Star counts are press-reported and move constantly.

npm install -g @fission-ai/openspec, then initialize in a project repo.