Validate Block Markup

Check serialized block markup against the WordPress core block library running in Node.js. Treat structural validity and cross-site portability as separate verdicts, and treat review and repair as separate jobs.

Verdicts are produced against the core block definitions shipped with WordPress 7.0.2. Always tell the user which snapshot the verdict came from.

Requirements

• Node.js 20.10 or newer, with npm on PATH.
• First run installs a runtime into this skill's own directory: npm ci of 350 packages, about 545 MB on disk, roughly 25 seconds, and it needs npm registry access. Later runs are offline and instant. --help and --version answer immediately and install nothing.
• The install never touches the user's project — no edits to their package.json, no lockfile changes, nothing written to a project-level node_modules. Everything lands in <skill-directory>/node_modules/.
• That distinction matters less than it sounds: the common npx skills add layout puts this skill inside the user's repository, so those 545 MB land in their repo tree. Say so before the first run. The skill ships a .gitignore covering node_modules/ and rewrites it before installing if it went missing, so git stays clean without the user doing anything.
• Most of the installed bytes are @wordpress/* packages, licensed GPL-2.0-or-later. The skill's own code is MIT.
• No WordPress, PHP, wp-env, Docker, Playwright, or browser is required.
• Run validation only through scripts/validate-block-markup.cjs. Do not import the module into your own process.

Dependency Bootstrap

The executable bootstraps itself. Before loading the validator it checks <skill-directory>/node_modules/ for four pinned packages and, if any is absent or at a different version, runs this in the skill directory: