A Claude Code plugin with two skills that turn an understanding target — a document, repository summary, pull request / diff, README, design note, or specification — into an offline HTML explainer bundle tailored to how a particular reader understands things.

The two skills split the work cleanly:

Input (doc / repo / PR / README / design note / spec)
  ↓ generate-explainer-yaml
core.yaml  (what it MEANS — concepts, relations, importance, difficulty, sources)
view.yaml  (how to SHOW it to this reader — audience, forms, emphasis)
  ↓ generate-explainer-html
HTML bundle: index.html (light/dark shell + view switcher + add-a-view prompts)
             + views/NN-<id>.html  (one switchable iframe view each)

1. Install the plugin (run these inside Claude Code):

/plugin marketplace add hirokita117/yaml-to-html-skill
/plugin install yaml-to-html@yaml-to-html-skill

2. Ask for an explainer. A single prompt runs both skills in the right order — generate-explainer-yaml first (writes core.yaml + view.yaml), then generate-explainer-html (reads that YAML by absolute path and builds the HTML bundle). Paste a document / repo summary / PR diff / README / design note, or point at a path.

English

Build me an offline HTML explainer bundle for this PR, aimed at an engineer reviewing it.
First use generate-explainer-yaml to produce core.yaml + view.yaml, then use
generate-explainer-html to turn that YAML (by absolute path) into a light/dark switchable
view bundle in ./explainer-bundle.

--- target ---
<paste the PR / document / repo summary / README / design note here, or give a path>

Japanese

この PR を、レビューするエンジニア向けに分かりやすく説明する HTML バンドルを作ってください。
まず generate-explainer-yaml で core.yaml と view.yaml を生成し、
続けて generate-explainer-html でその YAML（絶対パス）から
ライト/ダーク切り替え付きのビュー HTML バンドルを ./explainer-bundle に組み立ててください。

--- 対象 ---
<ここに PR / ドキュメント / リポジトリ概要 / README / 設計メモを貼る、またはパスを指定>

3. Open it. Open ./explainer-bundle/index.html in Firefox over file://, or serve the folder for Chrome/Edge (cd explainer-bundle && python3 -m http.server). See Opening the bundle for why.

Prefer to drive it step by step? Generate just the YAML first ("generate-explainer-yaml で core.yaml と view.yaml を作って"), review the two files, then hand their absolute paths to generate-explainer-html.

The HTML output is a bundle (a directory), not a single file:

• A light/dark shell (index.html) with a theme toggle (light by default).
• A right pane that switches between iframe views. Each view is a separate self-contained HTML document under views/. Views are additive — ask for a "table" view next to your "beginner" view and you get a second tab, not a replacement.
• A left pane of copyable prompt templates. Each asks another local-file-reading AI (Claude Code / Cursor / an agentic IDE) to read the YAML by absolute path and return one new view to add to the bundle. The prompts never embed the YAML content.

• No server, no API route, no build pipeline, no chat UI.
• No external CDN, CSS, or JS; no network calls; no storage or cookies.
• Each view runs in a sandboxed iframe (sandbox="allow-scripts", no allow-same-origin) and cannot reach the parent page.

The shell loads each view via a local relative src (e.g. views/01-engineer.html) — a local file read, not a network read. (A remote src stays forbidden.)

Two intermediate representations sit between the input and the HTML, produced by generate-explainer-yaml:

Keeping meaning separate from presentation is what lets the same core.yaml become many switchable views — each a different form of the same meaning.

The Quick start lists the two install commands. Once installed, both skills are available to Claude as generate-explainer-yaml and generate-explainer-html (namespaced yaml-to-html:generate-explainer-html, etc.). You can also use the scripts directly from a clone without installing the plugin.

When this skill is updated and the version in .claude-plugin/plugin.json (and marketplace.json) is bumped, users who installed via the marketplace need to update to get the new version. The installed copy does not update itself automatically by default.

Run these inside Claude Code:

/plugin marketplace update yaml-to-html-skill
/plugin install yaml-to-html@yaml-to-html-skill
/reload-plugins

1. /plugin marketplace update yaml-to-html-skill — re-fetches the latest marketplace.json from the repo so Claude Code sees the new version. This step is a required prerequisite: without it, the install command below won't see the update.
2. /plugin install yaml-to-html@yaml-to-html-skill — re-running install pulls in the new version.
3. /reload-plugins — activates the updated skill content in the current session without a full restart. (Restarting Claude Code also works.)

Tip — enable auto-update. To skip these steps in future, run /plugin, open the Marketplaces tab, select yaml-to-html-skill, and toggle Enable auto-update. Claude Code will then refresh the marketplace and update the plugin at startup.

To confirm which version you have, run /plugin, open the Plugins (or Installed) tab, and check the version shown for yaml-to-html against the version in .claude-plugin/plugin.json.

yaml-to-html-skill/
  README.md                         this file — repository overview
  LICENSE                           MIT license
  .claude-plugin/
    plugin.json                     plugin manifest (name, version, metadata)
    marketplace.json                marketplace manifest (lets users add+install this repo)
  skills/
    generate-explainer-yaml/        Skill A — Gen YAML
      SKILL.md                      entry point + procedure
      agents/openai.yaml            portable agent definition
      references/
        core-yaml-schema.md         meaning structure schema (core/v1)
        view-yaml-schema.md         presentation strategy schema (view/v1)
        sample-core.yaml            sample meaning (a PR)
        sample-view.yaml            sample strategy (engineer)
        examples.md                 three worked intents
    generate-explainer-html/        Skill B — Gen HTML
      SKILL.md                      entry point + procedure
      agents/openai.yaml            portable agent definition
      scripts/
        build_html.py               build/grow the bundle (assembler, not renderer)
        validate_html.py            safety / self-containment linter
      references/
        html-generation-rules.md    safety + UI rules for view documents
        output-bundle-structure.md  the bundle's structure and shell
        prompt-template-patterns.md add-a-view prompt templates + path placeholders
        sample-iframe.html          sample iframe view (engineer)
        sample-prompts.json         sample add-a-view templates
        examples.md                 three worked bundles

Builds and grows a bundle: writes the shell (index.html), merges views into views.json, copies core.yaml / view.yaml in, and renders the prompt cards. It substitutes {{core_yaml_path}} / {{view_yaml_path}} (the absolute paths of the copied-in YAML) into prompt bodies; any other {{...}} token (e.g. {{希望する表現}}) is left for the user.

# from skills/generate-explainer-html/
python scripts/build_html.py \
  --bundle ./explainer-bundle \
  --core /abs/path/core.yaml \
  --view /abs/path/view.yaml \
  --prompts references/sample-prompts.json \
  --view-html "エンジニア=references/sample-iframe.html"

--bundle and --prompts are required; --core / --view are optional (recommended); --view-html "LABEL=PATH" is repeatable. Re-running with a new --view-html appends a view; re-running an existing label updates it in place. (Use python3 if python is not on your PATH. Standard library only — no install.)

Scans the bundle for unsafe or non-self-contained patterns and exits non-zero if any are found, printing the offending lines. Pass index.html and every view file:

python scripts/validate_html.py ./explainer-bundle/index.html ./explainer-bundle/views/*.html

Detected (each is an error): external <script src>, remote-loading <iframe> (scheme :// or //), <object>, <embed>, external <link rel="stylesheet">, fetch(, XMLHttpRequest, WebSocket, localStorage, sessionStorage, document.cookie, window.parent, window.top, target="_top", and any http:// / https:// URL. A local relative iframe src (into views/) is allowed. Pass --strict to also fail on warnings.

Because each view loads via an iframe src, Chrome/Edge block file:// iframe loads ("Not allowed to load local resource"). Open the bundle either:

• in Firefox over file://, or
• by serving the folder with a trivial static server, e.g. python3 -m http.server run inside the bundle dir — that reads only local files; the no-network rule constrains the content, not how you serve the folder.

• Offline, self-contained bundle — no external dependency of any kind.
• Each view is sandboxed and cannot reach the parent page or the network.
• No storage, no cookies, no secrets, no large verbatim source dumps.
• Verified by validate_html.py before delivery.

# from skills/generate-explainer-html/
python scripts/build_html.py \
  --bundle ./sample-bundle \
  --core ../generate-explainer-yaml/references/sample-core.yaml \
  --view ../generate-explainer-yaml/references/sample-view.yaml \
  --prompts references/sample-prompts.json \
  --view-html "エンジニア=references/sample-iframe.html"

python scripts/validate_html.py ./sample-bundle/index.html ./sample-bundle/views/*.html

Open sample-bundle/index.html (Firefox / served). Right pane: an engineer-oriented PR explanation (worktree + reading order + review checklist), with a light/dark toggle and a view switcher. Left pane: copyable "add a view" templates and the YAML viewers.

• skills/generate-explainer-yaml/references/examples.md — three worked YAML intents.
• skills/generate-explainer-html/references/examples.md — three worked bundles, including how to add a second view next to the first.

• More built-in view.yaml presets (designer, SRE, security reviewer, exec summary).
• A small library of reusable iframe view snippets per form, still AI-composed.
• A diff mode that highlights what changed between two core.yaml versions.
• Export of core.yaml / view.yaml back out of a bundle for round-tripping.
• An optional offline JSON-schema validation step for core.yaml / view.yaml.