Source Intelligence

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.221 Home All releases olderv2.1.220 v2.1.222newer

Artifact skill prompt now states a page size limit

You'll notice
Useful2 Signal0
Artifacts

Claude now knows artifacts have a hard page size limit, including embedded data URIs, so it builds smaller pages.

What

The artifact authoring guidance tells the model there is a hard byte ceiling on the rendered page.

Details
  • A new Size bullet renders the limit from a constant into MB.
  • The guidance states that embedded data: URIs count toward the limit.
Evidence

Size: The rendered page must be

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.221 →