OpenSpec

OpenSpec is a lightweight, spec-driven framework for working with software requirements alongside code. Its page describes it as an open source tool with no API keys, and it is built around keeping specifications in the repository so they can persist as context across sessions and team handoffs.

A central feature is the spec delta: each OpenSpec change produces a delta that captures how requirements change. The page says this helps developers understand the system changes they are making and lets reviewers grasp the intent of a change without digging through code. It also generates planning materials for review, including a proposal document, implementation tasks, technical design decisions, and the related spec deltas, so plans can be refined before code is written. The examples shown include session-expiration requirements and a change that adds a remember-me checkbox with 30-day sessions.

OpenSpec stores specs in the repository alongside code and organizes them by capability. The page presents this as useful when an agent needs context for how a feature should work, and when a new developer wants to browse the specification library to understand the system. It also says the framework has native support with custom slash commands built in for 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, and iFlow, with more tools available beyond that list. It additionally mentions AGENTS.md support, where tools use OpenSpec through AGENTS.md and interact through chat rather than slash commands.

Delivery is via npm, with installation shown as npm install -g @fission-ai/openspec@latest. The page also links to GitHub and Discord. OpenSpec is an open source framework, and the page describes it as universal and as a planning layer intended to work across multiple sessions and coding agents.