artifact-design

name

artifact-design

description

Design guidance for any self-contained HTML/Markdown file shown in octo's Artifacts panel — reports, dashboards, architecture/system diagrams, generated UIs, slide-style pages. Read this BEFORE writing the file, not after — it calibrates how much design effort the request warrants and covers the panel's real constraints (sandboxed iframe, no external resources, narrow default width, no live theme push). Use when the user asks to "画架构图" / "generate a diagram" / "make a dashboard" / "produce a report page" / "visualize this as a page" / build any artifact meant to be looked at rather than edited. For chart/graph/plot-specific color and mark rules, also read the dataviz skill.

Artifact design

An artifact is any .html/.htm/.md/.markdown/.png/.jpg/.jpeg/.gif/.svg/.webp file the agent produces. Writing one through write_file/edit_file surfaces it automatically in the web UI's Artifacts panel; a file built some other way (a script, a build step, a download) needs one show_artifact call with its absolute path. This skill is about what to put inside the HTML — read it before writing the first line.

How the panel actually works — design within these constraints

• Sandboxed, not sandboxed-privileged. HTML renders in <iframe sandbox="allow-scripts" srcdoc=…> — scripts run, but there is no allow-same-origin: no cookies, no localStorage, no reach into the host app. This is a hard boundary, not a suggestion — design as if the page runs on an isolated blank origin, because it does.
• Self-contained is enforced, not just recommended. The panel detects <script src=…> / <link href=…> pointing anywhere but data:, blob:, or #, and if it finds one it refuses to render the page at all — showing a warning plus the raw source instead of your design. Inline every <style> and <script>; embed images as data: URIs; never reference a CDN, a Google Font, or any other network resource.
• The default viewport is narrow. The panel is a 420px-wide docked sidebar by default; the user can maximize it to min(900px, 75vw), but don't design for that as the common case. Build the layout to read cleanly at ~380–420px first, then let it use extra space gracefully above that — not the other way around. This is the opposite of most artifact platforms, where the canvas starts wide. Multi-column layouts, wide tables, and side-by-side diagram lanes need an explicit @media (max-width: 720px) (or tighter) fallback to a single column, or they'll clip or force horizontal scroll in the default view.
• Theme support is one-directional. Only @media (prefers-color-scheme: dark) is a live signal in octo today — the panel does not push its own light/dark toggle state into the iframe (unlike some other artifact hosts). Still write :root[data-theme="dark"] / :root[data-theme="light"] overrides alongside the media query — they're free, harmless if unused, and correct if that wiring ever lands — but don't rely on them being live; the media query is what actually renders today for most users.
• Update in place, not by versioning. Re-running write_file/edit_file against the same absolute path updates that same panel entry rather than creating a new one. If you're iterating on a diagram, keep writing the same file.
• No title/gallery metadata to set. The panel derives the display name from the file's basename and its type label from the extension — there is no favicon or description field to populate. A <title> tag is harmless but cosmetically inert here.
• Markdown gets code-block styling for free (the panel inlines a highlight.js theme for .md previews) — don't hand-roll code-fence CSS in a Markdown artifact; that's only a concern for HTML artifacts.

Calibrate effort to the ask

Don't build a dashboard when a status note was asked for, and don't ship a bare unstyled div when the user asked for something they'll actually look at and share. Match investment to what's being requested:

• A one-off answer, a small table, a short report → a clean, readable page. Spend your effort on typography and spacing, not on custom components.
• A named artifact meant to be referred back to (an architecture diagram, a dashboard, a generated tool UI) → invest in layout structure, a real color system, and responsive behavior — this is the case the rest of this skill is written for.

Self-contained checklist

Before calling write_file/show_artifact, confirm:

• No <link rel="stylesheet" href="https://…">, no CDN <script src> — everything needed is inlined in one <style>/<script> block
• No web fonts — use the system stack: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif
• Any image is a data: URI or omitted, never a network URL
• @media (prefers-color-scheme: dark) covers every color used, and every color has a light-mode default that isn't just "assume light"
• The narrowest layout (~380px) has no fixed-pixel widths wider than the viewport and no unintended horizontal scroll on the page body — wrap any table/code block that must be wide in its own overflow-x: auto container instead

The box-and-arrow diagram pattern

For architecture/system/flow diagrams, hand-written CSS beats reaching for a charting or graph-layout library — you get exact visual control, real theme support, and no library to inline. This is the same technique behind well-made "layered boxes with a few connectors" diagrams:

• Zones — a <div> per architectural layer/boundary, colored via a CSS variable per zone (--accent, --serve, --agent, …), laid out with display:flex/grid, not absolute positioning
• Cards inside a zone — one per component, a title + one or two lines of description, not a paragraph
• Connectors — Unicode arrow glyphs (↕ ↓ ↑ → ←) centered in their own small <div>, not actual line-drawing; this keeps everything reflow-safe when the panel width changes, which real SVG connectors are not
• Legend — a row of colored dots (<span class="dot"> with background: var(--accent)) mapped 1:1 to the zone colors, so readers decode color without following a line
• Numbered steps — <ol> with CSS counters (counter-increment/content: counter(s)) rendered as a small filled circle, cheaper and crisper than an actual numbered-badge image

Skeleton:

<style>
  :root { --bg:#fafaf9; --ink:#1c1917; --line:#d6d3d1; --accent:#2563eb; --accent-soft:#eff6ff; }
  @media (prefers-color-scheme: dark) {
    :root { --bg:#0c0a09; --ink:#f5f5f4; --line:#292524; --accent:#60a5fa; --accent-soft:#172033; }
  }
  :root[data-theme="dark"] { --bg:#0c0a09; --ink:#f5f5f4; --line:#292524; --accent:#60a5fa; --accent-soft:#172033; }
  :root[data-theme="light"] { --bg:#fafaf9; --ink:#1c1917; --line:#d6d3d1; --accent:#2563eb; --accent-soft:#eff6ff; }
  * { box-sizing: border-box; }
  body { margin:0; background:var(--bg); color:var(--ink); font:14px/1.5 -apple-system,BlinkMacSystemFont,sans-serif; }
  .wrap { padding: 20px 16px; }
  .zone { background:var(--accent-soft); border:1px solid var(--line); border-radius:12px; padding:14px; }
  .cards { display:grid; gap:10px; }
  .card { background:var(--bg); border:1px solid var(--line); border-radius:8px; padding:10px 12px; }
  .connector { text-align:center; color:var(--line); font-size:20px; margin:6px 0; }
  @media (min-width: 640px) { .cards.two { grid-template-columns: 1fr 1fr; } }
</style>
<div class="wrap">
  <div class="zone">
    <div class="cards">
      <div class="card"><b>Component</b><br><span style="color:var(--line)">one line of description</span></div>
    </div>
  </div>
  <div class="connector">↓</div>
</div>

Reach for real SVG or an inlined graph library only when the diagram has many interconnected nodes needing automatic layout, or edges that genuinely cross at arbitrary points — most system/architecture diagrams are layered boxes and don't need that.