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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.

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Claude Code v2.1.221

New artifact-diagramming skill and slash command

Not switched on
Useful3 Signal4
Artifacts Notable not in their notes

A new /artifact-diagramming command gives guidance on hand-authoring inline SVG diagrams inside Artifacts.

The /artifact-diagramming skill is registered but only appears behind the artifact gate, off by default.

Feature flag
tengu_cobalt_plinth On for this account, and not off by default

The flag server returned on for the one account this site reads, and nothing in this release compiles it off by default. The compiled default is shown below, and says which it is when we cannot read one: a fifth of gates compile in a string or a number rather than on or off, and most published releases have no gate table behind them at all. No client can see what the server returns for your account.

This account: on · anonymous baseline: on · compiled default in v2.1.221: on

These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.

Read once, for one account on one subscription tier, against v2.1.221. It isn't a statement about your account. What a flag value here can and cannot tell you

/artifact-diagrammingCLAUDE_CODE_ARTIFACTenableArtifact
What

A user-invocable command serves guidance on when a diagram earns its place in an Artifact and how to hand-author inline SVG for it.

Details
  • Registers under the name artifact-diagramming with menu text "Diagramming guidance for Artifacts".
  • Covers viewBox sizing, currentColor theming, marker arrowheads, figure/figcaption with role="img", and no script, style or foreignObject inside the SVG.
  • The workshop skill's instructions were updated to load it alongside artifact-capabilities during setup.
  • Gated behind the artifact availability check: env CLAUDE_CODE_ARTIFACT or tengu_cobalt_plinth with an in-source fallback of false, plus plan tier and the enableArtifact setting.
Usage
/artifact-diagramming
Evidence

Diagramming guidance for Artifacts

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

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.221 →