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github/spec-kit: the spec layer
Writes the spec the agent has to follow. Ends the era of "just vibe-code it."
GitHub's official spec-driven development toolkit (MIT, 94.4k⭐, install via uv tool install specify-cli --from git+https://github.com/github/spec-kit.git). A CLI plus methodology for treating specs as executable artifacts: write what to build, let one of 30+ supported AI agents (Copilot, Claude Code, Gemini CLI, Cursor, others) handle the how. The spec is the source of truth, not the prompt history.
Reach for it when "vibe coding" with an agent has produced a codebase nobody can reason about anymore — you can't tell which decisions were intentional and which were the model filling in blanks. Spec-driven flips that: the spec exists separately, gets versioned, and is what you actually maintain.
Delete: the README plus three half-written Notion pages where you keep specs that the agent never sees. Tradeoff: SDD is a discipline, not a tool — installing the CLI doesn't make you spec-driven any more than installing pytest makes you test-driven. Expect a real adjustment period before the workflow clicks.