OpenSpec is an AI-native spec-driven development CLI tool that provides a lightweight agreement layer between humans and AI coding assistants. It manages structured 'changes' with proposals, delta specs, designs, and tasks, supporting 30+ AI coding tools (Claude, Cursor, Devin, Copilot, etc.) by generating per-tool skills and slash commands. The CLI features a store system for cross-repo planning, an artifact graph for tracking change progress, shell completion generation, and a validation system. The codebase is well-structured with extensive test coverage, reusable components (artifact graph, markdown parser, command generation adapters, store foundation), and security-conscious patterns (atomic writes, prototype pollution guards). It is actively maintained with a large community (70k+ stars).