kernel-ui: Instructions file for Codex

Working in this repo

This is a monorepo for a component library built on real semantic HTML. Read README.md for the project pitch. This file is operational guidance for anyone (human or agent) making changes here.

Release checklist for pull requests

Any PR that changes a publishable package under packages/react, packages/elements, packages/styles, or packages/cli must include a .changeset/<descriptive-name>.md file describing the affected package(s) and the release level (patch, minor, or major). Run bunx changeset to create it. Docs-only changes do not need a Changeset. CI enforces this rule; the only exception is the Changesets-generated Version Packages release PR.

When creating a PR, never leave the Changeset decision implicit: add the file or explicitly confirm that the PR is docs-only/non-publishable. A merged PR without a Changeset will not produce an npm or GitHub release.

For consuming the published packages, don't read this file — read packages/react/llms.txt or packages/elements/llms.txt instead; they're the API reference. This file is about building the library, not using it.

The one rule that matters most: build every component twice

Every component ships in both @kernelui-lib/react (packages/react/src/components/<Name>/) and @kernelui-lib/elements (packages/elements/src/components/<Name>/) — a React version and a framework-free Custom Element version, with matching visual design and equivalent props/attributes. Adding a component to only one package is an incomplete PR, not a smaller one. Before considering any new component done, grep both packages/react/src/index.ts and packages/elements/src/index.ts for its export.

Repo layout

• packages/react — @kernelui-lib/react. Each component: <Name>.tsx + <Name>.module.css, exported from src/index.ts in shipping order (not alphabetical — new exports go at the end, before the polymorphic utils export block).
• packages/elements — @kernelui-lib/elements. Each component: <Name>.ts (extends KernelElement from ../../base, registers via customElements.define) + <Name>.css, exported from src/index.ts. CSS class names use kernelClass("Name", "part"), which produces the exact same class names React's CSS Modules compile to (see packages/react/vite.config.ts's generateScopedName) — this is deliberate, so one set of component styles serves both packages.
• packages/styles — @kernelui-lib/styles. Design tokens (tokens.css) and reset (reset.css). Both packages' components read tokens from here; never hardcode a color/spacing/radius value in a component's own CSS.
• apps/docs — Astro docs site. Each component needs: an entry in packages/registry (re-exported by apps/docs/src/data/components.ts), a page at src/pages/components/<slug>.astro, and src/components/demos/<Name>Demo.tsx + <Name>Playground.tsx. Copy the structure of an existing page (text-field.astro/scroll-area.astro are good recent examples) rather than inventing a new layout.
• packages/registry — shared component catalog consumed by docs, CLI, and LLM asset generation. Run bun run build there after changing entries.
• packages/cli — @kernelui-lib/cli. Published integration CLI (kernel init, kernel doctor, kernel docs).