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Sweep 28 Aug 2026 · 00:00Z Build v2.1.250 478 read Stable v2.1.236 Latest v2.1.250 Next v2.1.250 Feeds RSS JSON llms.txt

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.

Reference / Feature flags

tengu_velvet_falcon_model

A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.163 and was gone by v2.1.174.

What it is

Nobody has written a line about this one. It is not in any of Anthropic's reference tables and no changelog entry here carries a description of it. It is in the build, which is the whole of what this page can claim.

Presence across releases

ReleasesReadingDeclared typeDefault
2.1.245 – 2.1.250 5 releases never mined — —
2.1.174 – 2.1.243 63 releases not in the build — —
2.1.163 – 2.1.173 9 releases in the build — string

A row reading never mined is a release with no archived bundle behind it. Nothing was read out of it, so nothing here says whether the name was in it. A declared type or a default is only ever what that release's own bundle stated.

Gate readings

ReleaseResolvedThis accountAnonymousCompiled default
v2.1.163 read on another version Not enough to say no value returned no value returned not a boolean we can read

Two arms, because they disagree: this account is the one account this site reads and anonymous is a baseline with no identity attached. A reading says nothing about your account, and off cannot rule out a rollout both readings sit outside of. What these readings can and cannot show.

Changelog entries naming it

  1. v2.1.163Velvet Falcon Model Detection [In Development]

    gate cited by this entry

Documentation pages

None of Anthropic's documentation pages this site has a copy of carries this name.

Names beside it

Every feature flag in the inventory starting tengu_velvet, up to twelve of them.

tengu_velvet_anchorNo description from anybody. never mined tengu_velvet_cascadeWhich models get the simple system prompt is now decided locally, not by remote config. 2.1.138 tengu_velvet_hammerNo description from anybody. 2.1.166 tengu_velvet_harbor_owlA startup banner pitching Claude Enterprise to org admins exists but no one sees it by default. 2.1.238 tengu_velvet_ibisMAX_MCP_OUTPUT_TOKENS is still honoured first, but it's no longer sanity-checked as a number. 2.1.138 tengu_velvet_malletAn alternate prompt wording for two tools exists but stays off unless you set an environment variable. 2.1.166 tengu_velvet_mothNo description from anybody. 2.1.138 tengu_velvet_staticNo description from anybody. 2.1.138 tengu_velvet_tideWhich models get the simple system prompt is now decided locally, not by remote config. 2.1.210

Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the feature flag does. All feature flags.