Design docs

Find the reasoning behind a feature: why it is shaped the way it is, and the invariants a change must not break. Nothing is copied here: these link to the docs in plans/ on GitHub.

• Lit DevTools on Devframe — the panel as a Devframe definition, the source port, and what agents may call.
• DevTools features — HMR diagnostics, agent access, the update explainer, the CLI and MCP, snapshots, deep links, editor opens and persisted settings.
• Lit DevTools Timeline — the capture layers, the clock and grouping, and the virtual:lit-plugin/timeline API.
• DevTools redesign — the design-system tokens and theming shared by the panel and the runtime elements.
• ?css-sheet inline mode for library builds — the fetch-backed sheet 404s for consumers of a build.lib bundle, so the build inlines the CSS text instead.
• Documentation site with Astro + Starlight — this site: the stack, and why the material left the README.
• Release tooling — why releases are tag-driven, and what pnpm run changelog drafts.

Related

DevelopmentHow to build and run what these documents describe.

How HMR worksThe shipped behaviour the design docs led to.