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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_vellum_lantern

A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.138 and was gone by v2.1.154.

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 — —
2.1.154 – 2.1.243 80 releases not in the build — —
2.1.138 – 2.1.153 15 releases in the build — bool:false

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
v2.1.120 read on another version Off in both readings off off no gate table built for this version

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. v2.1.120Lean Prompt Mode (Condensed Tool Descriptions)

    gate cited by this entry

  2. v2.1.120Lean Prompt System [Gradual Rollout]

    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_vellum, up to twelve of them.

tengu_vellum_anchorThe out-of-credits message can add a "progress saved" note, off unless a server enables it. 2.1.229 tengu_vellum_ashNo description from anybody. 2.1.202 tengu_vellum_sidingNo description from anybody. 2.1.143

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.