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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_expressive_whistle

A Claude Code feature flag, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.

What it is

Claude can refetch startup config when the server says it is stale, but the gate is off.

Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.246.

Presence across releases

The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.

Gate readings

ReleaseResolvedThis accountAnonymousCompiled default
v2.1.248 Off in both readings off off on
v2.1.246 Not enough to say no value returned no value returned on

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. v2.1.248Stale-data refetch throttle becomes server-tunable, still off by default

    Refetch throttling after stale-data signals is now server-tunable but stays off without a server value.

    gate cited by this entry

  2. v2.1.246Off-by-default refresh of startup data when the server says it is stale

    Claude can refetch startup config when the server says it is stale, but the gate is off.

    gate cited by this entry

  3. v2.1.246Prompt and context experiment renamed to tengu_expressive_whistle, four other switches retired

    A prompt-and-context experiment switch was renamed and four other switches disappeared entirely.

    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_expressive, up to twelve of them.

tengu_expressive_whistle_configRefetch throttling after stale-data signals is now server-tunable but stays off without a server value. never mined

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.