Block Runner

The primitive between everything and WordPress blocks.

Block Runner is the layer between generated content and WordPress. AI tools, agents, and design tools spit out HTML, but the block editor only trusts blocks it recognizes, so it freezes everything else into a single "Custom HTML" blob, or breaks the block outright with "Attempt Block Recovery." Block Runner converts that output into real, nested, native Gutenberg blocks (wp:cover > wp:columns > wp:buttons) and proves every result is editor-valid. Built to sit in an agent loop, a content pipeline, or a CI gate, and deliberately a primitive rather than a platform: the blocks it emits are plain, native WordPress, editable in any editor with nothing proprietary to keep installed.

	Generated HTML reaches the editor as…
Today ❌	one frozen Custom HTML blob, or a broken block and "Attempt Block Recovery"
With Block Runner ✅	wp:cover > wp:columns > wp:buttons: real, nested, editable, valid

Quickstart

npm install block-runner          # requires Node.js ^20.19.0 || ^22.13.0 || >=24.0.0

This stable install provides deterministic convert, assemble, validate, fix, and skill commands without Docker, browser binaries, wp-env, or browser-proof dependencies.

The public registry currently offers stable 0.8.0 on latest. The 0.9 registered-block authoring work is an unreleased candidate: use a tarball supplied for a pinned candidate revision, not a nonexistent @testing tag. In a clean consumer project, install that reviewed artifact by path:

npm install /absolute/path/to/block-runner-0.9.0.tgz

Candidate preparation and release evidence are described in release/0.9-testing. Publishing or changing npm tags remains a manual owner decision. The registered-block author, plugin, and proof workflow below refers to that reviewed candidate, while the page-content conversion workflow remains available on stable 0.8.

A packed candidate proves only that its named tarball can be consumed. Automated proof can establish the specific runtime/editor claim named in its receipt. Neither a prepared owner-acceptance checklist nor an agent-assisted keyboard/screenshot review records the owner's visual, editing-feel, or manual-accessibility judgement; those remain required until a hash-bound owner record is retained. None of these states publishes 0.9 or changes an npm tag.

Then just ask your coding agent:

Use block-runner to convert this hero into a native Gutenberg block.

Or run the CLI yourself:

# native blocks stream to stdout by default; pipe them anywhere
block-runner convert hero.html

# pipe in from an agent, a generator, or curl
generate-page | block-runner convert -

# or write straight to a file
block-runner convert hero.html --out hero.blocks.html

Every run is checked against headless Gutenberg, so what comes back is guaranteed editor-valid, or Block Runner tells you exactly what wasn't and points at the line.

Using Block Runner from an AI agent

If you are the one deciding the structure, don't write HTML and convert it. Describe the structure as an intent tree and pipe it to block-runner assemble — deterministic code builds the markup, so it cannot come out invalid.

Block Runner ships a canonical skill in the open Agent Skills layout. Install it into the current project (ask the user before writing files):

# after installing the reviewed candidate tarball in this project
npx --no-install block-runner skill --install

That installs the same skill to the cross-agent .agents/skills/block-runner location and Claude Code's .claude/skills/block-runner compatibility location. Project scope is the default so the instructions can travel with a repository. Use user scope or one target when that is what you want:

npx --no-install block-runner skill --install --scope user
npx --no-install block-runner skill --install --target agents
npx --no-install block-runner skill --install --target claude

For a harness with another skills directory, use --dir <skills-directory>. With no skill system, npx --no-install block-runner skill prints the complete harness-neutral guide to stdout and writes nothing. Project discovery is the most portable choice; user-wide discovery paths still vary between harnesses, so use --dir when a client documents a different global root.

Benchmark

The image is historical conversion evidence, not an authoring result. Its workload is 63 fixed HTML sections per lane (11 serial lanes, 693 conversions); the suite, models/low effort, per-lane invalid counts, and monotonic serial timing method are labelled in the benchmark report. Each model gets the same fixture in two lanes: Direct writes Gutenberg markup itself; Block Runner returns an intent tree that the package assembles and validates. The dashed line is the deterministic rules converter running without an LLM. Every result is scored from 0 to 100 against the fixture's accepted block tree.

Registered-block authoring has a separate, currently unscored corpus in benchmarks/authoring. It has no combined score with this suite: it records editable plans, generated plugin source, native-block use, the style ledger, warnings, build, editor, frontend, pattern overrides, fidelity, and accessibility independently. The authoring benchmark is optional for 0.9 testing and does not run automatically during release checks. Required package and WordPress proof remain separate: a missing required gate is blocked, never a pass.

What it does

Two jobs: convert generated HTML into native blocks, and validate that what you ship is editor-valid. Use either half on its own: convert in your agent pipeline, or run the gate as a standalone validator in CI.

Convert: generated HTML → native blocks

• Native blocks, never locked in. Real wp:cover > wp:columns > wp:buttons, properly nested, with real media ids: plain core blocks anyone can edit in any WordPress, not a builder's proprietary block types you have to keep its plugin installed to touch.
• Broad element coverage. Tables, quotes, code, separators, video/audio, <details>, YouTube/Vimeo embeds, and image galleries all map to their native core blocks — not just the hero primitives. What genuinely has no native home (inline SVG icons, definition lists, arbitrary iframes) is preserved as Custom HTML with a warning pointed at the line, never dropped and never crashing the run.
• Any model, any agent. Feed it whatever your LLM, agent, or design tool emits, from any vendor, and drop it into your own pipeline instead of adopting someone else's editor.
• Media resolution. Resolve images to real attachment ids via a map, WP-CLI, or the REST API.
• Styling fidelity, your call. Keep off-theme styles or map them to your theme, up to a ceiling you set.
• Extensible. Built-in rules out of the box; add your own, or hand the hardest layouts to an LLM (experimental).

Validate: prove it's editor-valid

• A seatbelt for generated blocks. Models and builders will cheerfully emit markup that corrupts the editor; every result is held to a gate wired to headless Gutenberg first, so valid means what the editor means, not what a generator hoped.
• Reproducible gate. Same markup, same verdict, every time. Safe to run on every request and in CI.
• Canonicalize. Rewrite near-miss markup into the exact shape the editor expects.
• Never fails silently. When something can't be expressed natively, it says so and points at the exact line.

Why Block Runner

Content pours out of AI and agents faster than anyone can hand-build it, but "a block the editor actually accepts" is a brutally exact bar. To land one valid block, every one of these has to be right:

• Markup is validated against what the block's save() would output. Attribute order, class names, whitespace, a stray self-closing slash: one mismatch and the editor throws "This block contains unexpected or invalid content" and offers Attempt Block Recovery.
• Attributes live in a typed HTML-comment schema (<!-- wp:cover {"dimRatio":50,...} -->), order-sensitive, with defaults that must or must not appear depending on the block.
• Nesting is enforced. wp:columns accepts only wp:column, wp:buttons only wp:button, wp:cover wraps a specific inner container. Put the wrong child inside and the block is invalid.
• Each block expects its exact generated classes (wp-block-cover, wp-element-button, has-background-dim, wp-image-1234). Miss one and it breaks or renders wrong.
• Images need a real attachment ID, not just a URL, so you also have to resolve and import media into the library and thread the id through the markup.
• Colors, spacing, and fonts can map to your theme presets (var:preset|spacing|40, has-accent-color) only when the captured theme category and literal value match; otherwise the reviewed literal or scoped CSS remains explicit.
• Blocks carry deprecations. Markup that validated against last year's save() may not validate against this year's.
• Anything it can't place collapses into one frozen "Custom HTML" blob, and the structure, nesting, and editability are gone.

Get any of it wrong and you ship invalid blocks, broken layouts, or one giant uneditable blob. Block Runner gets all of it right: it turns whatever your agents and tools generate into real, nested, editable blocks with resolved media, then proves every result against headless Gutenberg before it reaches the editor.

Any content in. Real blocks out.

CLI

Command	What it does
convert	Authored HTML to native post-content blocks, including the legacy styling path.
author <html> --json	Analyze one authored design into a canonical registered-block plan, checked source, and style/asset ledgers. Does not write source.
assemble	An intent tree — JSON describing which blocks and how they nest — to native blocks, built with createBlock so the result cannot be invalid.
author preview <plan|->	Validate and render a versioned registered-block GeneratedAuthoringPlan without writing files.
author write <plan|-> --confirm <hash> --output-dir <dir>	Write the reviewed compiler-owned source package bound to its SHA-256 confirmation and destination. Build and runtime proof remain separate.
validate	Check block markup against headless Gutenberg.
fix	Canonicalize near-miss block markup.
context	Read a WordPress site into a site.context.json manifest (read-only).
proof	Run a real-WordPress proof profile for a built plugin ZIP and write an immutable receipt.
skill	Print or install the agent guide.
plugin inspect	Read-only detection of the supported @wordpress/scripts plugin profile.
plugin preview / plugin write	Preview, confirm, and integrate a generated registered-block directory; or create a standalone plugin wrapper.

block-runner convert hero.html                    # blocks to stdout
block-runner author hero.html --name acme/hero --json
block-runner assemble intent.json                 # structure in, blocks out
block-runner validate "content/**/*.html" --json
block-runner fix post-content.html --out post-content.fixed.html

# Inspect a host before integrating generated block files. This writes nothing.
block-runner plugin inspect ./my-plugin --json

# Preview every exact target, then use the displayed fingerprint with `plugin write`.
block-runner plugin preview ./generated-block --host ./my-plugin

# For an absent or unsupported host layout, make a complete standalone plugin instead.
block-runner plugin preview ./generated-block --standalone ./my-notice-plugin

plugin preview never writes. Its fingerprint binds the exact target files; pass it to plugin write --confirm <fingerprint>. Existing PHP or package.json files are marked as separate replacement approvals, so their absolute preview paths must also be supplied with --approve-replace <path...> before they can change. An unrecognised host is refused without writing and the command offers the standalone form above.

Standalone previews include the complete, versioned npm lock for their pinned local @wordpress/scripts toolchain. Confirmed writes only materialize the reviewed source and lock bytes: they do not resolve dependencies, contact a registry, or run npm. Run npm ci separately when preparing the generated plugin to build or package it.

Registered-block authoring

HTML analysis returns package.canonicalPlan. Save that object as your plan, review its native structure and editing policy, then use the same preview/write workflow below. Successful analysis uses the canonical source compiler; unresolved Custom HTML regions, unsafe assets, and unsupported CSS produce explicit failures, not a ready-to-install package.

For a reusable registered block, first make a versioned GeneratedAuthoringPlan rather than jumping from a description or design directly to source. The plan records the block target and native structure, editable and locked fields, style outcomes, pattern overrides, assets, planned files, and warnings. Review it before any write:

block-runner author preview authoring-plan.json --output-dir generated/feature-grid

The plain preview is deterministic for a plan, generator version, destination snapshot, and terminal width. It shows the plan SHA-256 and a separate confirmation SHA-256 bound to the planned destination and its fingerprint, labels fixed/editable/override fields without relying on colour, and ends with No files written. Preview is read-only; it has no prompt. NO_COLOR is honoured, and --json never contains ANSI escape sequences.

An installed Block Runner skill presents that preview to the user and asks for explicit approval. The CLI itself is always non-interactive. After the user approves the displayed confirmation hash, write the exact same plan to the previewed output directory. --output-dir is the exact package destination (not a parent root):

block-runner author write authoring-plan.json \
  --confirm '<full-sha-256-from-preview>' \
  --output-dir '<the-previewed-directory>'

Missing, stale, or incorrect confirmation values write nothing. If a plan replaces existing files, get a distinct, explicit replacement decision; a path collision, traversal or absolute path, changed destination, or any destination-prefix symlink fails before any write. The command rechecks these conditions immediately before exclusive, atomic writes. Use - for plan input only—never as a source of confirmation. files may declare only compiler-owned output paths and their create/replace operation; it never accepts file content. The deterministic compiler always emits its complete source set (and confirmed assets), including when files is empty.

Complete source-to-build routes

Both routes begin with a reviewed authoring-plan.json; use author <design.html> --name <namespace/slug> --json when you need the deterministic HTML analysis to produce its canonical plan. Neither route requires hand-written React, PHP, block metadata, or a repair step.

For a retained standalone plugin:

block-runner author preview authoring-plan.json --output-dir generated/feature-grid
# Review the complete preview and obtain its displayed confirmation hash.
block-runner author write authoring-plan.json --confirm '<confirmation-hash>' --output-dir generated/feature-grid

block-runner plugin preview generated/feature-grid --standalone plugins/acme-feature-grid
# Review the complete plugin preview and obtain its displayed fingerprint.
block-runner plugin write generated/feature-grid --standalone plugins/acme-feature-grid --confirm '<plugin-fingerprint>'

cd plugins/acme-feature-grid
npm ci
npm run zip
npm run test:zip

npm run zip builds the compiler-generated source and creates acme-feature-grid.zip; npm run test:zip checks the archive policy. That is build-ready delivery, not WordPress runtime proof. Run block-runner proof acme-feature-grid.zip --profile full ... with the reviewed source, markup, and fixture before claiming activation or editor behaviour.

For a recognised existing plugin, inspect before making any integration plan:

block-runner plugin inspect plugins/acme-host --json
block-runner author preview authoring-plan.json --output-dir generated/feature-grid
# Review and approve the displayed confirmation hash.
block-runner author write authoring-plan.json --confirm '<confirmation-hash>' --output-dir generated/feature-grid

block-runner plugin preview generated/feature-grid --host plugins/acme-host
# Review the exact paths and separately approve every displayed replacement path.
block-runner plugin write generated/feature-grid --host plugins/acme-host \
  --confirm '<plugin-fingerprint>' --approve-replace '<approved-path>'

cd plugins/acme-host
npm run build

The recognised profile places the generated source and safe registration update into the host, then npm run build produces the previewed build target. Create the host's normal delivery ZIP and run the same proof --profile full route; source integration or a build alone is not a runtime verification.

WordPress proof requirements

Headless validation is a fast first rung. A generated plugin needs a separate real-WordPress proof before any claim that it activates, registers, edits, or renders is credible. Before running, the proof report derives the required gates from the selected claim and the hash-matched artifact contract rather than treating every artifact as pattern-override-ready:

Claim / profile	What it establishes	Extra proof requirements
generated	Deterministic Gutenberg validation.	None; it does not start Docker.
built	ZIP installation, activation, and runtime registration.	Exact wp-env, Playwright, WordPress Playwright helpers, and Axe; Docker; an explicitly installed Chromium browser.
editor-verified	Built behavior plus insertion, declared editable fields, save, and reopen.	The runtime/editor toolchain.
fidelity-checked	Editor behavior plus frontend, visual, and automated accessibility checks.	The runtime/editor toolchain plus exact pixelmatch and pngjs.
pattern-verified	The two-instance pattern-override lifecycle.	A hash-matched artifact contract that declares capabilities.patternOverrides: true and its complete pattern fixture.
full	The exhaustive release-profile gate set.	All full-profile inputs, including pattern, visual, and manual-review evidence.

Library plus convert, assemble, validate, fix, author, plugin, context, and skill need only Block Runner's production dependencies. WP-CLI remains an external requirement only when selected for context, token, or media resolution.

The 0.9.0 package inventory moves the six real-WordPress/browser packages from the 19 direct production dependencies to six exact optional peers (retained as development dependencies for this repository). A basic installed dependency tree therefore has none of @wordpress/env, @playwright/test, @wordpress/e2e-test-utils-playwright, axe-core, pixelmatch, or pngjs; install them only in a project that runs real-WordPress proof.

Set up the runtime/editor proof boundary before requesting runtime or editor:

npm install --save-dev --save-exact \
  @wordpress/env@11.12.0 \
  @playwright/test@1.61.1 \
  @wordpress/e2e-test-utils-playwright@1.51.0 \
  axe-core@4.11.0
npx --no-install playwright install chromium

The full profile adds the visual-proof pair:

npm install --save-dev --save-exact pixelmatch@7.1.0 pngjs@7.0.0

This is deliberately explicit: the proof command never downloads tooling or a browser, and never makes a model call. If its optional tools are absent or on the wrong version, the receipt is blocked before Docker starts and prints this exact install command. A working Docker CLI and daemon are still required for real-WordPress profiles.

# Fast Gutenberg markup check; no Docker is started.
block-runner proof dist/acme-hero.zip --profile headless --markup fixtures/hero.blocks.html --input fixtures/hero.source.html --fixture fixtures/hero.proof.json

# Docker/MySQL WordPress 7.1, visible inserter, save/reopen, frontend, deactivation,
# visual and Axe checks. Evidence and the final receipt are SHA-256 addressed.
block-runner proof dist/acme-hero.zip --profile full --markup fixtures/hero.blocks.html --input fixtures/hero.source.html --fixture fixtures/hero.proof.json --receipt-dir artifacts/proof

headless, runtime, and editor remain cumulative operational profiles; full adds frontend, static deactivation, pattern, visual, and accessibility gates. For an artifact that declares patternOverrides: false, editor-verified and fidelity-checked do not claim or require pattern behavior. pattern-verified and full do. A required fail, skip, blocked, or missing result fails the selected claim. not_applicable can pass only for media when the fixture explicitly has no media; it never substitutes for omitted proof configuration.

The fixture supplies the generated block name, a non-empty editable field inventory, frontend scope/expectations, reviewed visual golden/masks/threshold, and Axe/manual-review scopes. A pattern fixture with edits to persist is required only when the selected claim requires pattern behavior. The browser always navigates to the post it created and published during the run, then records that ID and permalink. Golden images are read-only inputs: the runner stores expected, actual, and diff evidence but never refreshes a golden. Axe output is preserved in full; it is an automated check plus a separately recorded manual-review status, not a claim of complete WCAG conformance.

Proof tooling is exact-pinned as optional peers and retained in this repository's development dependencies. The included proof/wp-env.json pins WordPress core 7.1 and PHP 8.3, while the packed proof/dependency-pins.json preserves the direct WordPress package integrity pins that npm intentionally omits from package tarballs. The receipt additionally captures running-container image IDs, database/PHP/core/theme/browser observations, observed plugin metadata, Node and WordPress-package pins, generator/input/plugin/ZIP hashes, command logs, and every evidence object. The environment gate verifies that every retained observation command exited successfully, parses each value against its requested version/hash format, and requires the lockfile or packed pin snapshot plus integrity-pinned direct @wordpress/* packages. Missing or malformed observations block the runtime profile. Use --no-run only to produce an honest blocked diagnostic receipt after proof tooling is available.

npm run test:proof:mutations is an opt-in Docker acceptance suite. It builds deliberately broken plugin ZIPs and proves that registration, save, stylesheet, and pattern failures reach their respective independent gates; it does not run as part of the ordinary unit suite.

Read from stdin with -:

cat hero.html | block-runner convert -

Flags

All commands:

Flag	Description
--config <path>	Use a specific config file (otherwise auto-loaded from the working directory).
--json	Emit a machine-readable JSON report instead of text or markup.
--strict	Exit 1 on strict warnings (unresolved media, fallback blocks).
--explain	Include rule attribution and near-misses in the report.

convert and fix also take --out <path> to write the result to a file instead of stdout.

convert adds styling flags:

Flag	Description
--styling <level>	Styling ceiling: strict, relaxed (default), open. See Styling fidelity.
--css-out <path>	Write the sidecar CSS emitted by --styling open to a file.

convert adds media-resolution flags:

Flag	Description
--resolver <kind>	Media resolver: noop, map, wpcli, rest.
--wp-url <url>	WordPress URL for wpcli or rest resolution.
--wp-user <user>	WordPress username for rest resolution.
--wp-app-password-env <name>	Env var holding a WordPress application password.

author <html> --name <namespace/slug> --json analyses exactly one design and returns a canonical plan; it does not write source. Use author preview then the confirmed author write command to materialize the compiler-owned package. Shared generated CSS is registered through block.json's style field, while editorStyle is reserved for explicitly supplied editor affordances.

skill --install adds installation flags:

Flag	Description
--scope project|user	Install for the current project (default) or the current user.
--target all|agents|claude	Install both discovery copies (default), only .agents/skills, or only .claude/skills.
--dir <path>	Install under one explicit skills directory; cannot be combined with --scope or --target.
--dry-run	Show resolved destinations without writing files.
--force	Replace locally changed or unmanaged files at canonical bundle paths.

Installed instructions pin runtime commands to the package version that installed them. To update an unreleased candidate, first install the newly reviewed tarball, then re-run npx --no-install block-runner skill --install. Existing local edits are refused unless --force is explicit. After a published release, verify its available npm channel before using it in an update command.

An installation made by 0.7.x predates the managed manifest, so the first upgrade is deliberately refused as unmanaged. Review that copy, rerun once with --force, and remove the preserved root-level GUIDE.md after confirming the new references/GUIDE.md copy.

Exit codes

• 0: clean
• 1: problems found
• 2: usage or I/O error
• 3: headless Gutenberg boot failure

Run it anywhere

It's a Node CLI, so it drops into whatever you already use: your shell, a pre-commit hook, GitHub Actions, or any other CI (GitLab, CircleCI, and friends all run Node). And it's model-agnostic: it works on the output of any model, from any vendor.

pre-commit (add to .pre-commit-config.yaml):

- repo: https://github.com/humanmade/block-runner
  rev: v0.1.0
  hooks:
    - id: block-runner
      args: ['content/**/*.html']   # glob of files that contain block markup

GitHub Actions (or any CI) validate blocks on every push:

- uses: actions/setup-node@v4
  with: { node-version: 22.13.0 }
- run: npx block-runner validate "content/**/*.html" --strict

Library

The library is ESM-only and requires Node.js ^20.19.0 || ^22.13.0 || >=24.0.0. This means Node 20.19.0+ on the 20.x line, Node 22.13.0+ on the 22.x line, or Node 24.0.0+. Node 21 and 23 are intentionally unsupported. CommonJS callers should use await import('block-runner') rather than require('block-runner').

import { canonicalize, convert, validate } from 'block-runner';

const validation = await validate(markup);
const fixed = await canonicalize(markup);
const converted = await convert(html, { resolver: 'noop' });

Registered-block authoring contract

GeneratedAuthoringPlan is the public authoring contract at the preview/confirmation/write boundary. AuthoringPlan remains the semantic input contract for existing consumers, with SemanticAuthoringPlan available as its additive alias. HTML analysis (author()) and the deprecated semantic compileAuthoringPlan() adapt that contract; their returned canonicalPlan is a GeneratedAuthoringPlan that consumers review and write.

For HTML authoring, a harness first calls collectSourceEvidence() (or author() analysis) and then sends AuthorOptions.proposal: an ordered native structure with the returned sourceRefs, editor fields/locks, and any explicit content decisions. Block Runner binds exact source content, assets, CSS coverage, and required warnings before returning the same canonical plan. Existing complete AuthorOptions.plan callers remain supported. Component foundation containment remains an explicit author.styles.foundation: 'component' caller policy. The runnable authoring lifecycle example uses the same shape as the CLI and skill examples from proposal through preview, confirmation identity, and generation.

Regeneration and saved content

Compiler-owned output is only replaced after the destination-bound preview marks each replacement and its confirmation is supplied. An unchanged package is a no-op. Preview classifies a replacement as content-defaults, style-only, or saved-markup/structure. Style and asset changes can alter rendered appearance, but do not migrate saved block markup. Updated editor defaults apply to new insertions; existing saved content remains its own content record, though changed editor code can alter its editing experience.

A same-identity change to saved markup, registration identity, or attribute schema is refused. Use a new block identity, or add a tested WordPress deprecation/migration before replacing it. Block Runner does not edit a site's database, templates, or posts. Synced-pattern canonical updates are separate site operations and source changes make no sitewide propagation claim. Direct insertion, synced-pattern use, and plugin deactivation each need their own WordPress acceptance proof. Generated packages are static WordPress source and contain no Block Runner runtime dependency.

Supported entry point	Compatibility boundary
GeneratedAuthoringPlan, validateAuthoringPlan, hashAuthoringPlan, renderAuthoringPreview, planRegisteredBlockOutput, compileRegisteredBlock, destination inspection/write helpers	Supported v1 confirmation contract. The canonical hash is its sole plan identity.
AuthoringPlan / SemanticAuthoringPlan, author() and compileAuthoringPlan() / compileAuthoringBlock()	Supported semantic adapters. They return a GeneratedAuthoringPlan; semantic input is not a second preview/write contract. The compile names are deprecated through 1.x.
generateRegisteredBlock, materializeAuthoringPlan	Deprecated compatibility aliases through 1.x. Migrate to compileRegisteredBlock; no runtime behaviour changes.
emit*, validateBlockMetadata, generated-source and destination primitives	Advanced/internal-facing helpers.
convert, assemble, validate, fix/canonicalize, extractIntent, realize	Existing page-content APIs, unchanged and outside registered-block authoring.

target.metadata carries hash-bound native block.json metadata without forcing a reduced vendor schema at plan parsing time. The static compiler validates capabilities: executable keys and string metadata.variations PHP-file references fail with a precise compilation error. Inline declarative variation records and safe native metadata pass through unchanged.

Migration boundary: AuthoringPlan remains the supported semantic import throughout this compatibility line, and SemanticAuthoringPlan is an additive alias. Use GeneratedAuthoringPlan for every confirmation flow. Existing semantic values remain accepted by the deprecated adapters. Passing one to compileRegisteredBlock intentionally fails with invalid authoring plan: $.version must be 1; adapt it first and preview the returned canonical plan. No page-content API is renamed or removed by this migration.

Synced-pattern overrides (WordPress 7.1)

The semantic adapter compileAuthoringPlan() makes native content regions of a generated wrapper ready for WordPress's synced-pattern override flow. It adds a deterministic metadata.name and explicit core/pattern-overrides binding only to supported Core child attributes: rich text content, image id/url/alt, and button text/url. Layout remains the one canonical InnerBlocks template; the compiler never binds or synthesizes innerBlocks.

Stable names derive from the reviewed plan path, so a synced pattern stores an instance's local values in the normal core/block content map. Use templateLock: 'all' or 'contentOnly' when the pattern must retain canonical structure.

The full proof route is intentionally fail-closed:

block-runner proof generated-plugin.zip \\
  --profile full \\
  --input design.html \\
  --markup generated.blocks.html \\
  --fixture proof-fixture.json

It starts a real WordPress 7.1 wp-env, records the canonical wp_block content and each core/block.content instance value in an immutable receipt, then verifies two instances, reopen, canonical update, reset, structural policy, a missing-binding negative, and frontend output. Consumer proofs require an installable plugin archive and reviewed visual/accessibility inputs for a passing full receipt.

The repository builds its generated fixture plugin and native markup from test/fixtures/authoring/pattern-overrides.plan.json. Its WordPress visual assertion compares the completed page with the checked-in, reviewed proof/wordpress-7.1-pattern-overrides.expected.png golden; it never creates a baseline while evaluating one. The real receipt runs without a proof adapter or externally supplied artifacts:

npm run verify
npm run test:proof:wordpress

verify runs repository and packaging checks; test:proof:wordpress runs the real editor and frontend lifecycle. The latter requires a working Docker CLI and daemon. Proof commands record bounded Docker, wp-env, and browser phases in receipt evidence, so a failed runtime is reported as a specific blocked or failed phase instead of exhausting the general test timeout. On GitHub Actions, the separate WordPress proof job uploads a wordpress-7.1-pattern-overrides-receipt artifact on success or failure, retained for 14 days. It contains receipt-index.json, the content-addressed receipts/sha256 record, and its evidence/sha256 objects, so reviewers can inspect the WordPress 7.1 lifecycle evidence from the relevant build without committing environment-specific run output.

These are automated repository-fixture checks for their exact artifact and revision. They do not run the prepared owner-acceptance journeys or establish a human judgement about visual fidelity, editing feel, or accessibility.

Testing workflow

For ordinary changes, run the focused affected tests first:

npx vitest run <affected files>

For changes to proof startup or publication recovery, run:

npx vitest run test/proof-control-setup.test.ts test/proof.test.ts test/publication.test.ts test/publication.public-api.test.ts
npm run typecheck

npm run verify remains the required repository gate. Run npm run build && npm run test:package when changing exports, packed files, dependency pins, or consumer behavior. Run npm run test:proof:wordpress for proof-runner, browser, emitted-editor layout, persistence, or pattern changes; it requires Docker. Run the opt-in npm run test:proof:mutations only when detector wiring changes, and run the existing release check only for release candidates or release automation. Do not relax the visible mutation skips, runtime-proof gates, thresholds, or the intentional fileParallelism: false Gutenberg serialization.

The following inventory makes the focused checks auditable:

• The control-startup helper replaces VM extraction and script-order assertions. Its test proves a writable .block-runner-proof-stage, retained existing ZIPs before startup, and that an incompatible path is preserved without invoking startup.
• A proof-runner command test replaces the staged-container-directory literal check: wp plugin install receives a byte-identical ZIP beneath /var/www/html/wp-content/block-runner-proof/, never an uploads path. The exact proof/wp-env.json mapping remains a schema contract.
• The wp_upload_bits, upload-error, retained-byte hash, and no-direct-write checks remain the media byte contract: successful WordPress execution cannot deterministically inject both upload failure and corrupt retained bytes.
• The one-command staging-failure receipt test remains. The former receipt-index source-order assertion is protected by the failed-full-proof content-addressed readable-receipt case in test/proof.test.ts. Named CI and release artifact-upload checks retain their if: always() and node_modules exclusions.
• The src/publication.ts call-site assertions were removed because the shared lifecycle matrix in test/publication.test.ts covers interruption, reconciliation, pending-file races, corrupt/missing/linked staging, and final verification. Authoring and plugin adapters retain their recovery, approval, conflict, and user-visible-error coverage; the public cleanup guard retains its recursive-deletion prohibition and guarded-trash fallback.

Unchanged behavioral coverage includes authoring.runtime.test.ts for emitted-component layout and v1-to-v2 content persistence; proof-real-wordpress.test.ts and proof-pattern-overrides.test.ts for native editor layout and isolated pattern instances; plugin.profile.test.ts plus test:package for packaged assets; authoring.destination.test.ts and registered-block.workflow.test.ts for confirmation; the shared publication matrix plus adapter suites for concurrent edits and interruption; proof-visual-baselines.test.ts for reviewed bytes; and the visibly skipped mutation suite for real-ZIP detector checks.

Timing is recorded only as comparable observed samples, never as a general speed claim. The baseline is npm test at head 631a13bd with the same lockfile on the same Mini: started 2026-09-06T05:08:49.668Z, finished 2026-09-06T05:14:44.746Z, duration 355.078s. Record the single required #52 Foundry-gate sample beside it with its exact tested head, command, start time, exit time, and duration; do not compare unrelated CI lanes, machines, or workloads.

Media Resolution

A <img src="hero.jpg"> in generated HTML is just a URL, but WordPress image and cover blocks want a real media-library attachment with an ID (wp-image-1234). Media resolution is how Block Runner connects the two: matching or importing each image into the library and threading the right id into the block. Choose how it does that:

• noop: leave URLs as-is and warn when an ID is missing (good for a dry run).
• map: look up IDs and URLs from a JSON map you provide.
• wpcli: find or import media with wp media list and wp media import.
• rest: find or import via the WordPress REST API, with credentials supplied explicitly.

Remote sideloading is off by default. Under --strict, unresolved media (and fallback blocks) cause exit code 1.

Configuration

Block Runner auto-loads block-runner.config.{mjs,js,json} from the working directory, so most runs need no flags; the config sets the media resolver, tokens, and rules. Pass --config <path> only to point at a config elsewhere.

block-runner.config.mjs:

export default {
  strict: false,
  media: {
    resolver: 'map',
    mapFile: './media-map.json',
  },
  tokens: {
    colors: {
      dark: 'contrast',
      light: 'base',
      accent: 'accent',
    },
    fonts: {
      heading: 'display',
      body: 'body',
    },
    spacing: ['20', '30', '40', '50', '60'],
  },
};

Styling fidelity

Design HTML often carries custom CSS (and sometimes JavaScript) that doesn't match the target theme. The styling level controls how much of it Block Runner keeps. The levels run from safest (cleanest, most editable blocks) to most faithful (keeps the original look, but less editable):

Level	What it does
strict	Map to the theme only. Off-theme styles are dropped. Cleanest, fully on-brand, fully editable.
relaxed	Keep exact off-theme values on the block (custom color, size, spacing). Still native and fully editable.
open	Also keep CSS no block can express, by putting a class on the block and emitting that CSS as a stylesheet you ship alongside. Look preserved, structure still editable.
source	Keep the original markup as a Custom HTML block. Exact, but not editable. Last resort.

You set one ceiling. Per block, Block Runner uses the strictest level that still captures the design, and never goes past your ceiling. Configure it in block-runner.config.mjs, or per run with --styling:

export default { styling: 'relaxed' }; // the default

Styling is read from inline style attributes and from single-class <style> rules (.hero { … }). An inline style outranks a class rule, matching CSS. Every declaration is accounted for: mapped onto the block, recognised as consumed by the structure, or reported with the input line and the rule that authored it — nothing is dropped silently.

open emits a stylesheet, so it needs somewhere to put it. --styling open requires either --css-out <path> or --json (where it arrives as sidecarCss) and is an error otherwise — a level that quietly discarded the CSS it promised to keep would be worse than not offering it.

Custom JavaScript is never inlined. A behavior maps to a native interactive block, comes from a block plugin, or is dropped, and every drop or escalation is reported.

Registered-block CSS and assets

author accepts compiled CSS through author.styles.css (or <style> content in the design), but its author.styles.mode must explicitly be css or tailwind. It does not infer Tailwind from compiled utility declarations or ship it at runtime. In tailwind mode, supply the complete author.styles.tailwind graph: CSS entries, resolved imports and directives, sources, safelist, plugins, environment, browser target, and the project’s pinned compiler. author materializes that graph and runs the compiler; source directives use its output, while separately supplied CSS must match it. Missing inputs, unreadable entries/imports, compiler failures, and mismatches are reported field by field and generation stops. Every referenced --tw-* variable must also be defined in that output.

Non-native selectors are preserved only when they can be rooted beneath the generated block's deterministic .wp-block-<namespace>-<slug> class. Responsive, container-query, and pseudo-state rules retain their conditions. Preflight/global rules, escaping selectors, imports, and keyframes are ledgered and blocked rather than silently scoped. Confirmed local static assets are copied into assets/ and rewritten; remote image URLs remain external by default.

Authoring records the target theme snapshot hash, configured WordPress viewport ranges, unresolved custom variables, and reset assumptions in the hash-bound plan preview. It never edits theme.json. Without that target context it explicitly limits its fidelity claim. Only an exact WordPress 7.1 viewport interval on one unambiguous, supported native child can use a responsive state; every other conditional source rule remains scoped CSS.

CSS analysis has one tolerant source-facts pass: it retains rule/declaration IDs, exact line/column/byte ranges, malformed-declaration and blocked-rule evidence, then feeds asset, scope, native, and cascade decisions. PostCSS remains an output validation boundary rather than a replacement for this pass: malformed author input and byte-exact URL rewrites need the original spans. The URL and image-set() value lexer remains specialized because it must distinguish direct strings from url() tokens and rewrite escaped tokens tail-to-head. Selector cascade matching and responsive lifting likewise remain conservative semantic checks; ambiguous conflicts and non-equivalent media conditions stay exact scoped CSS or explicit warnings.

Local WOFF/WOFF2 fonts require an explicit source, SHA-256, ownership, and license decision. Approved font families get block-specific names and shared editor/frontend CSS. Full redistribution notices are retained separately in the production archive because minifiers can remove CSS comments. Unlicensed or unsupported faces use a safe fallback with a source-located warning. Destination theme font presets do not require copying font files.

Status: strict, relaxed and open are implemented. source is not built yet and is rejected rather than silently downgraded — though the converter already falls back to a Custom HTML block for structure it cannot convert.

Running the benchmark

A conversion benchmark lives under benchmarks/: it measures how faithfully real generator output (Impeccable, Codex, Claude, and more) converts to native blocks, across swappable converters (the built-in rules, plus experimental LLM translators run via their CLIs).

npm run bench          # score the suite; write benchmarks/presentation/review.html + benchmarks/presentation/scoreboard.html
npm run bench:record   # also append a provenance-tagged run to benchmarks/results.jsonl

Runs are recorded with engine / model / effort / suiteHash, so older engines stay backtestable against the current suite (scripts/backtest.sh). See benchmarks/README.md for adding producers and engines.

The registered-block authoring corpus is deliberately separate from that conversion suite:

npm run authoring:prove -- --plans ./candidate-plans

This requires saved canonical candidate plans and the configured WordPress runtime worker; see the corpus README. Without them it reports blocked work, not a benchmark result. It does not turn unrun browser/editor work or a model/tool failure into a zero product score. The 0.9 testing-release package, installer, and activation checks are run with npm run release:check; see release/0.9-testing for the receipt matrix and the draft product-preview brief.

License

GPL-2.0-or-later.